Ramblings & Comments to Scott's NAMCpedia

I’ve gotten way behind in my comments/additions to Scott’s postings.  He has posted a lot of great tips and references.  Scott is definitely turning this website into the go to site for park jets.  Keep up the good work Scott!  So rather than going back and adding comments, I going to compile them in this posting.

Launch/takeoff- Ailerons Off

Ouch, I’ve crashed several planes at launch.  Practice with something that weighs similar to your plane.  I hold the fuselage at the CG and throw it at 30-degree angle with 45-50% throttle.  Amount of effort is to toss the similar weighing object about 15 feet.

Something that I do differently than Scott is I turns ailerons off.  I program my radio so I can turn the ailerons off with the dual rate switch (not effect the elevons).  

There are several advantages to having an aileron off mix.  These planes fly very well with elevons only.  They fly even better with a touch of aileron input.  Too much aileron and you can turn your plane into a lawn dart—been there, done that.  Same with dual rates, you get fumbled fingered and leave it in high rate at landing—lawn dart.  Yep, did that too.  So when do I turn my ailerons off?  I turn them off at take off to help prevent wing tip stalls.  I also turn them off when I am doing a max throttle high speed fly by.

Spoilers/Flaps

I really enjoy these mixes on the park jets.  Spoilers give you extra degrees of high alpha and flaps are great if you are running a heavy setup like the NTM 2700 prop drive.  When I launch and land a plane with NTM, I always use flaps.  Noticed I used the words spoilers and flaps rather than spoilerons and flaperons.  I turn off the aileron input when I deploy flaps and spoilers.  I have found the plane to be much more stable at slow speeds by not having aileron input to the spoilers and flaps, i.e. spoilerons and flaperons.  The more you upset the airflow over the wings at slow spead, the greater the chance of a wing tip stall.

Performance & Flight Evaluation

Dialing in the ailerons.  I first set up the elevons to get the amount of pitch I want.  Once I am happy with the throws, I then start on the ailerons.  I roll the plane nose up at 50% throttle and dial in the aileron throw to get the desired roll rate.  I am not the rifled bullet make your dizzy type, I like a roll rate that is a little faster than scale (see this in my videos).  

The other maneuvers I like to test are rudder stall turns and knife edge turns.  Of all the maneuvers, the knife edge has been to toughest and what led to the development of the vertical rudder.  I can do a knife edge circle but have yet to do a straight down the runway knife edge.

Whoosh or Stealth

Great observation Scott.  All of my planes make different levels and types of sounds.  As you mentioned, noise is a result of air disturbance and inefficiency.  Taking the time to smooth leading and trailing edges makes a huge difference.  A plane cuts through the air like a knife, which do you prefer sharp or dull?

Push Rods

I’ve tried multiple variations and I agree completely with Scott on the Dubros.  They are way too heavy and a complete pain in the butt to adjust.  I use carbon rods/tubes but a slightly different technique.  For elevon pushrods I use 2mm carbon rods.  Instead of a clevis, I make use wire with a Z bend and piece shrink wrap.  For my NTM planes, I use a 3mm tube that Dubro rods fit nicely inside of.  I will make a how I do it video that will include outboard servo setup that Scott and I use.

Alene’s Tacky Glue

I love this stuff!  It is dirt cheap and I use it for glassing.  FoamTac is great stuff, but way too expensive to use for glassing—if you glass as much as I do.  

I’ve been crazy busy and haven’t had much time for building or flying.  My NAMC v4 only needs servos, rods and KFs.  Hopefully I will get it done this weekend.  Meanwhile, Scott is going to have to build another one because he fatigued the airframe from flying so much!

If Scott’s proposed NAMC’ed Su35 with fixed elevator/elevon flies like I think it will, I know what I’m building next.  Have to keep that one a secret from FRC!

Blue skies to ya!

Stephan

Great websites for paint scheme inspiration and markings

Hi everyone -

I'm always on the lookout for inspiration for new paint schemes for any of the planes I build... :)  After building several Mig29s and Su27 to Su37 aircraft, it is tough not to repeat the same paint scheme, although when you find one you like, it can be worth repeating, especially if it is simple to do and gives good contrast in the sky.

Here is an excellent site for looking at different Mig29 paint schemes

http://www.mars.slupsk.pl/fort/mig/

Another one for Su27 to Su37 paint schemes

http://www.mars.slupsk.pl/fort/sukhoi/

  

Mariusz Wojciechowski  is the gentleman from Poland that maintains the two sites above, I have pasted in his logos from the two sites and might start putting them on my planes if I use his site for inspiration for a paint scheme.  I highly respect his passion for keeping his sites up to date and providing me with such great inspiration for different Mig and Su paint schemes.  When you open either of the sites, normally if you left click on the side view drawing of any plane you see, it will open a full scale sheet with side, top, bottom views and what the inside and outside of the tail fins look like.  You can actually right click on this new page when you open it and save his drawing to be able to zoom in or out as you are painting your plane, works great for me.

A Wiki site that can be very helpful for finding accurate fin flashes for planes is http://en.wikipedia.org/wiki/Fin_flash

This Wiki site is great for finding roundels to put on your plane, I use it all the time http://en.wikipedia.org/wiki/Military_aircraft_insignia

For these logos or any other insignia, I make mine out of paper, I simply copy the image, open in Word or other document where I can size it where I want it and print it out.  I then cut it out of the paper with a new sharp Exacto #11 blade and I find using Aleene's Tacky Glue, there is a description here at Amazon http://www.amazon.ca/Aleenes-15601-Original-Tacky-16-Ounce/dp/B0084DC3KA/ref=sr_1_1/189-2586512-6011846?ie=UTF8&qid=1406771155&sr=8-1&keywords=aleene%27s+tacky+glue  Stephan directed me to this product and it works really well.



I suppose any other white craft glue that dries clear would work well, I just put some down on a piece of wax paper and then use a small piece of scrap foam to smear a thin layer on the back of the "decal" and using a fine pair of tweezers position it on the plane, works really well... :)

Another great site if you want to do replica paint schemes of airshow teams or are just looking for inspiration is this site, lots of awesome pictures.

http://aerobaticteams.net/

Another couple great sites if you are looking to watch some video of the Mig29 history and development from the Russian point of view is here http://nordsky.blogspot.ru/2012/10/from-mig-29-to-mig-35-take-off-into.html

Same for the history and development of the Su27 family of fighters http://nordsky.blogspot.ru/2012/06/sukhoi-su-27-flanker.html

Hope this might be of help when looking for a inspiration for a cool paint scheme for your plane.... :)

Cheers,

Scott

Evaluating a plane's performance - the Basics

Hi everyone -

In the pursuit of building and flying the "perfect park jet", Stephan and I are constantly assessing and evaluating the performance of our planes to see if there are certain characteristics that still need improvement or perhaps they are just behaviors that will always be there and we just need to adjust our flying accordingly.

As you can imagine, it takes some time to fully assess how an airplane is going to react in certain maneuvers and it takes time and repeated execution of that maneuver to honestly assess what a plane is doing.  Some of these things are evaluated hand in hand with the process of "dialing in" a plane that I described in a previous post http://migsrus.blogspot.ca/2014/07/some-thoughts-about-dialing-in-plane.html.  But then once the plane is "dialed in", more intermediate and advanced maneuvers can be practiced and assessed already knowing that for normal flying around the plane has been trimmed and balanced to the best of my ability.

Additional factors are also the limits of a person's flying skills, there are certain moves I am still working on, but currently don't have the skills to execute properly on a regular basis to be able to assess the plane's performance.  Additionally, I don't always repeat the same loop or same roll each and every time, pilot error, or slight differences in stick movement can make a big difference, so it takes some focus and discipline to try and repeat the same maneuver over and over the same way.  Weather and wind conditions are another big variable over which we have no control and have to factor in whether or not it is the plane that has bad behavior or if it is the wind or maybe a combination of both.  Often we find bad behaviors like the negative impact of Elevon Polar Pitch Effect (EPPE) caused by wind which has led to Stephan and I working hard to reduce elevon and tail plate size on the V4M3e3 to reduce this behavior.

Stephan and I both love flying foam park jets, there are few types of RC planes that can be such fun to build with inexpensive materials and components that give back such exciting performance.  We love the speed, agility and how we can push our planes and our skills for such little investment of time and money when compared to other types of planes in the RC realm.  I like to call it a very high "fun to dollar" ratio.

To put my flying style into perspective and I think Stephan is in the same ball park, let me try and describe how I like to fly as this has a large impact on the framework within I assess my planes.  For the past year I have really been focusing on trying to fly in a more scale fashion.  I have watched countless videos on Migs and other Jet fighters flying at airshows and have been trying my best to repeat turn rates, climb rates, loops, rolls, etc.  I find it a very challenging and satisfying way to fly as repeating a move that a real plane has executed is a lot of fun.  I'm not a fan of crazy rifle bullet rolls or flip loops, I did do this at one time, but found there was very little challenge to doing these as they just require slamming the sticks around without requiring much finesse on my part.

When I look at a plane, I am looking at it as a whole of it's parts, not just control surfaces, but weight, wing loading, thrust to weight ratio, acceleration, top speed, etc.  For the most part since I build with only two different power setups, the Focal Price 2700 and the NTM Prop Drive 2700, if the weight, thrust to weight ratio, acceleration and top speed are off, then either there is a problem with one or more components of the power train, or I have simply built too heavy.

So for this first installment, I would just like to discuss how I evaluate a few basic handling characteristics of a plane, ones which will be repeated over and over during the life of the plane, but are probably some of the most crucial.  Those are launch/takeoff, climbing, descending, turns, landing.

Launch/takeoff

Hand launching a plane is still one of the most unpredictable things for me about flying park jets.  It is that few seconds in every flight where I don't feel like I have any control of the plane right after it leaves my hand and starts to fly away.  What I am looking for here are any bad behaviors, too much torque roll (perhaps I am launching with too much throttle), sudden nose dive or nose pitch up, I find most of my planes will pitch down slightly, but that is normal until I get get a bit more speed and the plane stabilizes.  I normally launch all my planes with about 45-50% throttle, normally on the higher end if it is a bit windy.  Most planes that are fairly stable at slow speed like the Mig29 are not too much of a problem.  The RCP T50 V1 which does not like to fly at slow speed can be a real crap shoot on take off, so I really have to be careful with it.  I am looking primarily for the plane to at least stay airborne for a second or two after it leaves my hand until I can get both hands back on the transmitter and start flying it away.

Climb out

When a plane is climbing out after launch or at anytime during the flight, I am looking for it to respond smartly with no pitch up or rolling tendencies.  As I discussed in a previous thread, I find that 1.7:1 thrust to weight ratio is ideal for how I like to fly and expect my planes to perform http://migsrus.blogspot.ca/2014/07/some-thoughts-about-thrust-to-weight.html  I am also looking to make sure it tracks in direct response to the power and control inputs I give it and not drift one way or the other (unless it is due to wind).  If it does, either it needs some trim or something is wrong with how I built it.

Descent

When a plane is descending, especially with a bit of speed on, I want to ensure it responds well to the elevator input so that I can pull out in time, I'm also watching again that it doesn't drift or want to roll as it gathers speed in descent and that I am not seeing any wing flex as I pull out of the bottom of a descent or loop to ensure that my build has been strong enough to compensate for the wing loading and g forces I plan to put on my plane.

Turns

As I have mentioned in a previous post, when you think about the makeup of your average flight, the one maneuver you will do the most is turn.  If a plane misbehaves or is a handful in turns, it is more than likely going to be a handful in most other maneuvers as well.  Normally I will set my throttle at about 50% and fly several figure 8 patterns in front of me, alternating direction so that I am not always turning left to the left of me and right to the right of me (almost sounds like the song "Stuck in the middle with you"... :)).  By flying at about 50% throttle and inputting about 50% stick deflection in the turns, I am simulating how most of my turning at my flying field will happen as I re-position for my next aerobatic maneuver/high speed pass, etc.

In the turns I am looking for how the tail is handling, is it bobbling around, or following the rest of the plane like it is supposed to?  How does my plane hold it's energy?  Does the tail want to drop in the turn requiring rudder input?  Does the nose drop indicating that the plane is losing energy in the turn and needs more power to sustain an even turn?  How does it track?  Does it maintain even, uniform turn rate, or does it dig in it's heels and "bat turn", or wash out like a drift car?  Some of this may be due to the fact I don't have my throws and expo dialed in just right yet, so it is a good indicator that more adjustment is needed, or it could be something I need to adjust in how I fly the plane or adjust for the next time I build it.  If I am finding negative effects from too much surface area in the back, or Elevon Polar Pitch Effect, this can be compensated with a gentle acceleration through the turn, or as mentioned, adjusted through modification in the next build.

I am also looking to ensure it is not too sensitive in the roll part of a turn or the aileron input.  Since I fly my planes with aileron and elevon working together, they can get a bit more touchy in the roll, so I want to make sure I adjust this properly so I don't over bank when trying to do a simple turn.

Landing

Landing like take off can be an exciting phase of flight as the plane slows down and again comes in close proximity to terra firma... :/

Before I talk about what I am looking for on approach and landing, I should discuss the landing technique that I have developed (I won't say perfected, as I don't know if I will ever be there... :/) over thousands of park jet flights.  Most of my planes are in the 21 oz/595 gr region.  For my heavier 25 oz/710 gr planes with the NTM Prop Drive, everything stays the same, I just give myself more room to land as the heavier planes tend to glide further.  This is certainly not the only way to fly and approach and land safely, but one that works for me... :)

I like to do my base leg turn at about 50% throttle, that way as I am turning final, I have some decent speed and momentum.  When the plane is about eye level (or what I perceive to be about 6 ft off the ground), I chop the throttle to zero.  I always fly with the ESC brake "off", so I normally get a bit of free spooling which I find helps keep my plane more stable as it slows down.  I allow the plane to descend on it's own using rudder and or roll inputs to keep tracking as straight as possible down the runway.  I like to allow it to keep up some speed as it goes forward to help penetrate ground effect, that spot about 1-1.5 wingspan lengths from the ground, so in the case of these planes, about 2-3 ft off the ground.  Once I am about 1.5 - 2 ft off the ground, I will feed in very gentle elevator input to flare the plane and use some aerodynamic braking for a nice smooth landing.  Of course all bets are off if it is windy, this may require the power to be held on slightly to help with forward momentum or maneuvering, all a matter of practice and knowing how the plane will react.

 On approach to landing, I am looking at how the plane slows down, does it just stop dead when I chop the throttle or maintain decent momentum?  I am looking for it to maintain some momentum or I will have to keep power on through most of the landing phase to keep from "landing too high" i.e. landing two feet off the ground and then just thumping down... :(  Tip stalls can occur quite easily on approach to landing if a plane is susceptible to this problem.  In other words one wingtip will stop flying and drop (often quite quickly) and often the plane then ends up cartwheeling... :(  I'm also looking to see how a plane handles ground effect, sometimes if a plane is a bit "floaty", it will almost bounce off the ground effect layer meaning perhaps I need to keep a bit of power on to help it penetrate the ground effect.  Many of my worst landings have been caused by landing on top of the ground effect layer where I am basically at zero speed still a foot or two in the air and then the plane just drops in whatever fashion it wants to... :(.

So hopefully this explains the basic guidelines I look for when evaluating a plane and some of the basic maneuvers I use to be able to repeat the same maneuver numerous times to truly assess what my plane is doing.

Next installment of this series, I will look at some more intermediate maneuvers, rolls, stalls, loops, stall turns, slow and high speed flight to further evaluate a plane's performance.

Cheers,

Scott

Time for another NAMC modified FRC Su35 MK2... :)

Hi everyone -

Was out blasting around with a couple of my favorite Russian park jets this morning... :)

I hadn't had my modified FRC Foamies Su35 MK2 out in a couple weeks as I have been so busy flying and evaluating my new Mig29 V4M3e3.  I now have 150 flights on the Su35 and it has been an amazing plane to fly and was the first plane I modified since I started sharing ideas with Stephan a few months ago.  I explain the mods I made from the stock FRC Su35 MK2 in this walkaround and flight video.  The flight video part is not the best, the plane tends to wash out quite a bit, but the first part will explain what changes I made from stock.  All of these mods I talk about in the video will stay, with a couple minor updates... :)

So today I noticed a couple of things, the vertical rudders work awesome, just like they do on the V4M3e3, so that is staying.  Also, it was proof again that the vertical trailing edge on the vert stabs makes for a "quieter" back end on the plane.  Overall the Su35 is not quite as stable as even the stock RCP Mig29 V4, but much quieter in the back end in turns for sure.

What I did notice when I did a close fly by test is that there must be quite a bit of turbulent air flowing over this plane as there is quite a "whoosh" just like I described in my last post about the stock Mig29 V4.  So some changes need to be made to address that hopefully... :)

So here are a couple more tweaks I think need to go into another Su35 MK2.  I was planning on building an F18 V4 with quite a few NAMC mods, but decided to build another Su since I really do enjoy flying it so much.

The only thing structurally I will update is the elevons.  I will evaluate their size again to ensure they are still as close to scale as possible, probably extend the "tail boom" a bit for more scale looks, but the biggest change is I will adopt the hinge setup from the RC Powers Mig29 V4 where I will have a traditional horizontal stab portion then the elevons hinging from that.  This will result in less moving surface, but I think help make things even just a bit smoother in turns and pitch maneuvers like loops.  The real Su is more responsive in the pitch than the real Mig from what I have seen in watching countless You Tube videos, but I would rather be the one putting in that aggressive pitch move than have to compensate for the plane being over aggressive in the pitch.  I think this also reduce drag and turbulence in the back end when flying due to the smaller moving surface of the elevons.

To help reduce overall drag and turbulence, I will symmetrically shape all leading and trailing edges as well.  The Su35 in the picture above was the last plane I built with "chisel" shaped leading edges on the wing and elevons.  I had done this for many, many planes as that is what everyone seemed to be doing when I first joined the RC Powers forum.  Fortunately, Stephan was able to shake me of that paradigm and I have definitely bought into the symmetrical leading edge helping with overall "slipperiness" of the plane through the air.  The top speed I have ever clocked with this plane is 74 mph, so I think with these changes that speed will be broken easily.  Being smaller than the Mig29 V4, there is no reason it should not be up there around 80 mph like the Mig is, I think that by using this old style build technique, I am fighting build induced drag... :/

So, time to dig out some plans and start drawing out the mods in the next few days.  Excited to see how these fairly minor changes to a plane I already modified will perform.  I think things can only get better... :)

Cheers,

Scott

RCP Mig29 V4 vs Mig29 V4M3e3 - mid term evaluation... :)

Hi everyone -

Was out blasting through a bunch more lipos this morning doing another bit of a fly off between my stock RCP Mig29 V4 and my NAMC modded Mig29 V4M3e3.

I now have 147 flights on my stock Mig29 V4 and 75 flights on my V4M3e3.  Although I have yet to have ideal conditions to really dial in the high alpha setup on my V4M3e3 since it has been too windy, for all other flying I have it dialed in pretty much exactly the way I want it and through 75 flights have put it through it's paces in just about every imaginable attitude and aerobatics that my skill levels allow me to attempt.

It had been almost two weeks since I last flew my stock V4 and once again it reminded me of why it is without a doubt my favorite stock built park jet of all time.  If I could never modify a plane ever again and could only fly a stock built Mig29 V4, I would still be the happiest guy at the field.  I know that sometimes it seems like in my excitement of how great a modified plane flies that it seems like I might make the stock plane sound like it is not even worth building.  That has never been the case and as I have posted here on this blog and many times on the RC Powers forum when I was still actively posting there, the Mig29 V4 is the best stock built park jet I have ever built and flown.

So, having said that and I know I may be a bit biased as I shared in the ideas and modifications for the V4M3e3, it is simply a more stable, more precise and better flying plane in all aspects with really just a few simple, very achievable modifications.  I know I have already said this when I did the first comparison when I maidened the V4M3e3 and wrote my post flight report comparing the stock and NAMC modified Mig29 V4, but now that I have significantly more flights under my belt, I would like to report some more in depth findings I noticed today.

I know I don't have side by side video comparison or wind tunnel tests or anything else to compare and unless you actually are standing at the field, you wouldn't see the difference, but there are a few simple aerodynamic differences that help back up some of my opinions.

The smaller control surfaces, especially the modified elevons and vert stab/rudders make a big difference in how precise this plane is, how much quieter it is not only it how it flies, but physically quieter which I will describe in a bit.

So here are a few numbers to put things in perspective hopefully.  As I said throughout the build process and early flights, I estimate the total reduction in elevon surface area between stock and the V4M3e3 is about 15% and total reduction in aileron surface is about 40%.  The rudders may be about the same size in surface area, but the orientation of the hinge and trailing edge is what makes the big difference in rudder performance.

For my flying style and since I fly at the same field all the time, I have developed a certain amount of muscle memory in my thumbs when I turn especially and I tend to adjust the expo and throw on each new plane to account for that.  Meaning I put the same amount of input in the sticks to get the plane to turn 180 degrees at each end of the field without hitting the trees and then just adjust how much throw I need with each new plane to allow me to do that without adjusting my flying style too much.  Hopefully that makes sense... :/

So here are my expo and throws for the stock V4 to allow me to fly the way I like to fly

• Rudder - 60% expo, 100% throws;
• Elevator - 55% expo, 75% throws; and
• Aileron - 60% expo, 50% throws.

Here are my expo and throws for the V4M3e3

• Rudder - 60% expo, 100% throws; 
• Elevator - 55% expo, 80% throws; and
• Aileron - 60% expo, 65% throws.

So not a huge difference in settings to allow me the same turn rate and roll rate between both planes.  This is logical considering the difference in size of the elevons and ailerons that a bit more travel sometimes would be required to get the same pitch and roll rates.

However, in how the planes fly, a noticeable difference.  

In turns, the stock V4 still will occasionally bobble a bit or have negative behavior from elevon polar pitch effect (EPPE which Stephan and I have discussed on the blog in depth).  It is still very smooth, but not as "quiet" as the V4M3e3.  As I have mentioned several times, the V4M3e3 just carves through the air with minimum wasted movement or effort, it tracks more solid than any other plane I have ever flown.

In loops, with the V4M3e3 having less moving surface, I can put on 60% power, pull about 50% down on the elevator and it just flies a smooth, constant loop all the way through with no real requirement to modify the control inputs.

With the stock V4, I have to be more gentle with the initial input or the plane will go straight vertical rather than "arching" it's back and entering the loop smoothly.  Then throughout the loop, much more finesse is required with the throttle and elevator to get the plane to maintain a uniform circle and pull out in the same spot/altitude where it entered.  For how I like to fly, it has just a bit too much moving surface in the elevator and there is too much drag and turbulence caused by this bigger surface while it is deflected.  Now I know that in theory a good smooth loop is an aerobatic move that does require the pilot to adjust power and control surface inputs to maintain a uniform circle, but with the V4M3e3, it is just so much easier and smoother.

For rudder performance, there is really no comparison if you want to execute maneuvers that require good solid, responsive rudder input that will move the plane properly in the yaw axis without having to compensate for too much roll.  For me, I have found that a good way to evaluate how "clean" and direct rudder movement is in a plane is to execute a stall turn http://en.wikipedia.org/wiki/Stall_turn.  I know the diagram below is a bit simplified, but it essentially is going vertical at about half throttle, letting the speed bleed off till almost in the stall and then kicking the rudder full left or right.  The plane should do what the plane is doing in the diagram.  With the V4M3e3, I can do this with little to no opposite aileron input and the plane goes through 180 degrees of yaw and starts it's decent within about one to two wingspans of space.  I almost never see any tendency to want to roll while it is going through the stall turn.



With the stock V4, I have to coordinate the rudder kick and feed in opposite aileron to keep the airplane from rolling rather than just kicking the nose through 180 degrees in the yaw axis, meaning the rudder is causing roll input as well as yaw, not something I really want my rudder to do, but again, just what I want/expect from my planes.  Also, by having to put quite a bit of opposite aileron to prevent the roll, the move ends up looking more like a wingover http://en.wikipedia.org/wiki/Wingover than a stall turn as it can take almost 4 wingspans to get the plane through 180 degrees.

Having said that, the wingover is another good maneuver to use lots of rudder and see what the plane does, although with both planes I found opposite aileron was required, just lots more with the stock V4.





So earlier in this post I mentioned not only does the V4M3e3 fly "quieter" in that it is much smoother with less bobble, bouncing around, etc., it is physically quieter.  Now before you think I am losing it... :/, try the following the next time you are flying and see what sort of sounds (other than the prop) you can hear your airplane making.

I flew several close passes in front of myself with both planes, about 10 ft in front of me at about eye level, so about 6 ft off the ground and at about 75% throttle.  I flew these passes in both directions with the wind and into the wind.  As the stock V4 flew by, I could easily hear a "whoosh" as the air flowed over the plane.  As the V4M3e3 flew by, it was about 50% quieter.  I can only put this down to reduced turbulence brought on by smaller elevon span and vertical trailing edge on the rudder/vert stab.

As you probably know, turbulent air causes sound.  As I drove home from the field, I had my car window rolled down and it drove this point home.  By having the window rolled down, I was reducing the aerodynamics of my car, causing turbulent airflow over my car and increased noise.  In the case of the two planes, I can only assume the difference in the "tail feathers" (elevons/vert stabs/rudder) was responsible for the much quieter sound of the V4M3e3.  It is without doubt more sleek and "quieter" through the air which also leads me to believe it is more efficient through the whole speed range.  I have already clocked it as being 6 mph faster than stock, even when it is about an oz heavier!  So reduced drag and turbulence due to size of the elevons and orientation of the vert stab/rudder seem to be the only answer as the finish of bevelled/symmetrical leading and trailing edges is identical on both planes.

This fact was also driven home to me again in approach and landing.  The V4M3e3 glides about 25% further than the stock V4, again leading me to believe there is a noticeable decrease in drag and turbulence and increase in efficiency as the plane passes through the air.

So as I have said before, I know not every plane can have the vertical hinged rudders or have vertical trailing edges on the rudder/vert stab, that would like kinda weird on an F18, but the smaller elevons and ailerons are definitely big winners.  I also think that the 40% KF has an important role to play in increased stability and lift.  I know it isn't a big increase over stock, but working in conjunction with all the other modifications, it all makes a big difference.

Again, I know I am a bit biased, but I am amazed at how a few changes here and there make such big differences in the performance of a plane.  It is fun to experiment and educational, as I learn so much with each new plane as to how little modifications here and there are affecting airflow, drag, turbulence and overall aircraft performance.

Cheers,

Scott

Thoughts on "scratch built" pushrods

Hi everyone -

As a sequel to my previous article about using lighter, less expensive nylon gear (NG) servos in place of metal gear (MG) servos in most circumstances to lighten my planes, I wanted to write about my method for scratch built pushrods.  This is certainly not the only method for making your own pushrods, I know Stephan uses a different method, but for the same reason, the pushrods end up being lighter and less expensive in the long run.

Up until about a year ago, I used to build notoriously heavy, too much glue, components that were too heavy, etc.  My planes still flew OK, but I was missing out on a lot of potential performance because my planes were so heavy and had such high wing loading.  And it also took me several catastrophic crashes to realize that heavy planes are actually less durable than light planes.  The more weight coming to a sudden stop, the more damage, often non-repairable.  Now with my lighter planes not only do they respond quicker when I start to get in trouble, but if I do have the odd "gonk", the damage is far less serious.

So when I took the leap to start using NG servos to help lighten my planes, I also started making my own pushrods to save weight and in the long run a bit of money.

RC Powers recommends using Dubro 2-56 threaded pushrods on their master parts list http://www.rcpowers.com/community/threads/master-parts-list-official.8300/.   This is fine for beginners as they are easy to bend and easy to adjust, all you really need is a "Z" bend at the servo end and the adjustable clevis at the control horn.  Again I'm not trying to undermine or criticize RC Powers, just discuss some ideas for lighter, less expensive options to achieve the same goal.

The Dubro pushrods are heavy and in the long run more expensive than making my own.  One pair of 12" Dubro push rods weighs 14 gr/0.5 oz.  The cheapest cost that RC Powers lists them for is $3.49 for a package of 5, so essentially $0.70 each.  So if you like to use 6 servos like I do, you have to buy two packages of 5 as I use 6 push rods.  So that is fine, unit cost is still the same.

So here are the products I use to make my own scratch built pushrods

1. Nylon clevis from HK - http://hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=8421  cost is $0.64 for 10, so lets say for arguments sake $0.07 each.
2. 2mm carbon rod from RC Foam, sold in 1 meter or 39" lengths - http://www.rcfoam.com/carbon-fiber-sheets%2C-carbon-rods-and-tubes/carbon-rod/carbon-rod-p-737.html one length costs $1.60, so $.04 per inch.
3. 2mm quick connectors from HK - http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idproduct=8519  I actually normally use ones from RC Timer, but the RCT website seems to be down as I write this.  So the quick connects from HK are $0.12 each.

So lets look at my recent Mig29 V4M3e3 build to figure out what it would cost to use Dubro pushrods versus scratch built both in weight and cost.

I use 6 servos for all my planes, so 6 pushrods would be needed, cost would be $4.20 for 6 Dubro pushrods.  Unfortunately, I would end up wasting some of the rod as once I cut it off, I don't have much use for the scrap rod.  My elevon pushrods are each 10" long, aileron pushrods 5.75" long and rudder pushrods are 9" long.

So here is where the math gets a little anal, the Dubro pushrods weigh 0.02 oz per inch, so if I need 49.5", my pushrods will weigh 1 oz.

So now lets look at cost and weight for my scratchbuilt pushrods. So I need 6 clevis at $0.07 = $0.42, 49.5" of 2mm carbon rod costs me $1.98 and 6 quick connects at $0.12 = $0.72, total cost is $3.12.

For weight, the clevis are 0.5 gr each, so 3 gr total.  The carbon rod weighs 1.5 gr per ft, so 6 gr plus lets round up 1 gram to include a bit of weight for the epoxy needed to make them, so 7 gr plus 6 quick connects at 1 gr each is 6 grams, total weight is 16 gr or 0.56 oz.

So I have saved myself $1.08 in cost and 12.5 gr/0.44 oz in weight.  I know that this perhaps doesn't seem like a big saving in either category, but in the long run it is for me.  Both types of pushrods can be recycled between airplanes, so once a set has been made they can continue life through several planes.

I waste less material with the carbon rod method as I can cut the 2mm carbon rod exactly to size and any little bits I have left over I keep to recycle if I need a little bit of extra reinforcement in a plane here or there.

Granted, not everything about the carbon rod pushrod setup is easy, they cannot be bent like the Dubro rods, but for my preference, I prefer pushrods with no bends.  To accommodate for this shortcoming, I simply angle my servos like in these pictures.

The rods are quite simple to make.  I cut the rod to the length that I need, then take a razor knife and gently shave/whittle the ends so that they will fit easily into the clevis and quick connect.  Normally I have to drill out the hole in the clevis so that the rod will fit in.  I still want it snug, but not so tight I might split the clevis putting the rod in.  I then mix up a little 5 minute epoxy, put a dab in the clevis hole and a small bit on the end of the rod and slide it in so that the sleeve in the clevis is filled with the rod for a good secure bond.

For the quick connects I use from RC Timer, they have a little nut that goes on a threaded shaft to hold them to the servo arm, I always put a very tiny bit of blue loctite on the threads to keep it secure.  It is important not to over tighten the little grub screw in the quick connect so that you don't crack or crush the carbon rod.  The nice thing is though that with a little tightness, the grub screw bites into the carbon just a tiny bit and prevents slippage.

I do prefer the very fine adjustment available to me with the quick connects also.  With the Dubro pushrods they are very adjustable, but sometimes I end up just that tiny bit off since they can only be adjusted a half turn at a time where the little nylon clevis screws on and off of the rod.  I also find they are a bit more of a pain to adjust as I have to keep removing the clevis from the control horn, make a few turns, hope it is enough, then reattach.  This can take a few tries whereas with the quick connects, one adjustment and I'm done.

So as I mentioned earlier, not a massive savings in cost or weight, but when you are really looking to save weight on your plane, a few grams here and there all add up and the more weight I can save without sacrificing strength and performance, the better.  And if I save a buck or two here and there, that is an added bonus... :).  

Anyway, another option to consider if you are looking for a simple, inexpensive way to lighten up your plane and save a few pennies.

Cheers,

Scott

Metal gear servos on park jets - "necessity or overkill?"

Hi everyone -

If you have watched my walk around videos for the last several planes that I have built, you probably noticed I am a big fan of lighter, less expensive nylon gear (NG) servos.  About a year ago after watching my first "overweight" RCP F18 V3 self destruct in front of my eyes (wing snapped in flight due to too much weight, too high a wing loading... :(), I really started to focus in on building light and started seriously looking at ways to reduce every gram of weight possible.

Previously to this time, I followed the RC Powers recommendation of using metal gear (MG) servos for everything, which not only added weight to my plane, it reduced a lot of weight from my wallet... :/  So I took the chance on using NG servos on my planes then and have not looked back since .

Here are some quick weight and cost comparison numbers to help explain some of what I mean.

Popular MG servos

• Hextronik MG-14 metal gear servo currently recommended by RC Powers master parts list - weighs 14 gr/0.5 oz - cost is $7.95 http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8303&aff=46898  I have a couple of these servos and this is the actual weight on my inexpensive kitchen scale.
• Hobby King 939MG Metal Gear Servo (used to be one of the recommended servos on the RC Powers master parts list). These are advertised as 12.5 gr servos, their actual weight on my scale 15 gr/0.5 oz, current cost $5.75 http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14458
• RC Timer 9018MG servos, these are advertised as 9 gram MG servos, they actually weigh 15 gr/0.5 oz and cost $4.29.  These are my favorite metal gear servos, and not just for the cost which I will explain in a bit.  http://www.rctimer.com/product_525.html  Here is an interesting note to watch for.  RC Timer sells 6 packs of this same servo for $27.99.  You would normally think that bulk packs would save you money...well, $27.99 divided by 6 = $4.67... :/, so cheaper to buy them individually.

Popular NG servos

• Hobby King HXT900 9 gr servos.  These very popular blue servos have been around a long time and I strongly suspect are made by the same company and sold as Tower Pro and other brand names at almost every hobby shop or online vendor around.  Actual weight 11 gr/0.4 oz, cost at HK - $2.69 http://hobbyking.com/hobbyking/store/__662__HXT900_9g_1_6kg_12sec_Micro_Servo.html.  
• RC Timer TS-9018 9 gr Micro Servo.  Actual weight 11 gr/0.4 oz, cost - $1.98 http://www.rctimer.com/product_458.html These are my favorite nylon gear servos and not just for the price which I will explain in a bit.

So I'm not saying throw away your MG servos or never buy another one, they certainly do serve a purpose for certain applications.

About a year and a half ago, I had built a Boxermad84 (before it was FRC Foamies) F35 600, it was a small, fun plane to fly which I built elevons only and initially had the Turnigy D2826/6 motor in it.  It was one of the first park jets where I took the chance with NG servos (HXT 900s to be exact).  So as I gained experience in flying, of course I wanted to see how fast I could get this plane to go.  I kept increasing motor size until I got to the NTM Prop Drive 2700.  I got this plane up to over 90 mph with the NTM...very exciting stuff for me at the time.  However, one thing I started to notice was at speed (lets say 70% throttle or higher), when I tried to turn, I got what I call "prop wash or servo blow back".  The elevon servos could not hold the elevons in place due to the excessive strength and turbulence of the prop wash caused by the 42 oz of thrust the NTM was generating.  So I would get kicked out of turns because the servos could not hold the strain.  Fortunately I never stripped a servo or lost the plane, I swapped the NG servos for MG servos and life continued along merrily.

So as a rule, with any plane where I am going to use the NTM Prop Drive 2700 motor, I use MG servos on the elevons.  It just buys me a little piece of mind that my servos can handle the stress and thus far even at 109 mph on a 4S with my Mig29 V3M3e3, the RC Timer MG servos I mention above have worked flawlessly... :)

On any other planes where I am going to use the Focal Price 2700 or lighter motor, I go with the RC Timer 9 gr NG servos for all the control surfaces and thus far, have not had a single problem in hundreds and hundreds of flights in temperature conditions from -5C/23F to 30C/86F.

So you might say, "well why worry, I am only saving 4 gr per servo".  Well even with my NTM planes, I use NG servos on my ailerons and rudders, so in fact I have saved 16 gr/0.56 oz.  But more than that, I save $9.24 which can buy a lot more servos, props and other goodies, or just stay in my pocket for other things in life... :)

By using all NG servos on my current plane the Mig29 V4M3e3 over using MG servos, I save 24 gr/0.85 oz and a total of $13.86, now I have saved enough to buy another Focal Price motor!

So why do I prefer the RC Timer servos both MG and NG?  Well, of course the price is right, much less expensive than the HK servos and shipping is pretty cheap.  Now, a word of caution in dealing with RC Timer (and Focal Price for that matter), what you save in shipping cost, you pay for in shipping time, so don't be surprised if it takes 4-6 weeks for your products to get to you from RC Timer/Focal Price.  This is why I normally make my orders worth while and buy enough servos for at least two airplanes at a time.  I also get my 6x3 EMP props from there http://www.rctimer.com/product_218.html , best deal I have found, so I don't make small orders from there, I get plenty of goodies and end up being my own supply source.

But cost aside, they just plain work better in my humble opinion than the HK choices.  They are quieter, smoother and come with longer servo arms giving me a bit more flexibility in push rod placement.  Here is a side by side picture comparing the black RC timer servo on the left to a blue HXT 900 servo on the right.

I don't work for RC timer nor do I get any special deals because I write about their stuff, I use their stuff because it is inexpensive and it just plain works time after time.  I have hundreds if not thousands of flights in total with planes using RC timer MG and NG servos and have not had a single problem to date.

So you might be apprehensive about using NG servos.  If RC Powers recommends MG, then why should I listen to this goofball writing this post?  Well, I'm certainly not trying to discredit RC Powers or anyone else, I am simply passing on my experiences from buying, building and flying with NG servos over hundreds if not thousands of park jet flights.  I push my equipment to the max on a regular basis and have not had an issue with any NG servos for park jet applications (other than in the story of the Boxermad84 F35 600 I told above).  As I already wrote, I would recommend MG servos for elevons on a plane where you might use the NTM 2700 motor or a motor that produces that much thrust or more, but for ailerons and rudders, NG servos work just fine flight after flight.  

And for the Focal Price and lighter motor planes, NG servos for all control surfaces have worked for me on over a dozen planes.

So after all these numbers and rambling, what is the answer to my question?  Well, for the one application with the NTM Prop Drive motor, I think that MG servos on the elevons are a necessity.  For all other applications, I believe and have proven time and again with my own flying experiences that MG servos are overkill for park jets.

So hand on heart I feel very, very confident in recommending NG servos for park jets within the criteria I mentioned.  Not only do they lighten the load on my plane while giving me excellent performance, they also significantly lighten the load on my wallet, which I think we all appreciate... :)

Up next in the theme of keeping things light, strong and inexpensive, the sequel article to this post, "making light, strong, inexpensive pushrods from scratch"  :)

Cheers,

Scott

Some thoughts about "thrust to weight" ratio and motor/prop choice

Hi everyone -

Awhile back I wrote a post about my favorite all round weight for the V3 and now V4 size planes as well as the FRC Su35/37.  You can read more in that link here http://migsrus.blogspot.ca/2014/02/rc-powers-v3-size-planes-and-weight.html

Essentially what I found for my style and preference of flying was that between 20-21.5 oz in AUW (including battery, in this case a 2200 3S) was where I liked to be for these planes when I use the Focal Price 2700 motor.  As I mention in the article, this gives me a thrust to weight ratio of about 1.7-1.8 to 1 which still gives me good speed, acceleration and punch out power for best overall performance in matching my flying style and skill level.

So as I was flying my Mig29 V3M3e3 the other day comparing it to my Mig29 V4M3e3, I was trying to think of something they might have in common and it turns out to be the thrust to weight ratio.  The NTM Prop Drive 2700 with a 6x4 APC prop on 3S produces about 42 oz of thrust.  With a 2200 battery, my V3M3e3 weighs 25 oz, so a thrust to weight ratio of 1.7:1.  One thing I have learned over almost two years and 40+ park jets is that thrust to weight ratio is an important component of how I build and fly my planes.  Fortunately for me after testing multiple motor and after literally thousands of flights over 2 yrs, my two favorite park jet motors are the Focal Price 2700 for lighter planes and the NTM Prop Drive 2700 for heavier and very fast planes.

So here are some interesting things I started analyzing.

1. While thrust to weight ratio has a lot to do with top speed, the prop used has a big impact on initial acceleration and top speed characteristics.
2. When I speed tested my Mig29 V4M3e3 the other day with the FP 2700 motor and 6x3 EMP prop, my weight was about 20.5 oz, so a thrust to weight of about 1.75:1, top speed of 88 mph.
3. When I speed tested my Mig29 V3M3e3 with the NTM Prop Drive and 6x4 APC prop, my thrust to weight ratio was 1.7:1, top speed of 94 mph.
4. Both setups gave me the overall speed and acceleration (give or take depending on the motor/prop setup) that makes for exciting flying and the scale performance and aerobatics that I enjoy, so the common thrust to weight ratio of about 1.7:1 is an important number to me for how I build to enjoy the performance I want when I fly.

I had found last summer/fall when I tested 8 different motors on the bench and at the field in my RCP F18 V3 along with different props 6x3/6x4 EMP and 6x4 APC that the 6x3 EMP prop was excellent for initial acceleration and punch out power as it spooled up to max RPM quicker, but for true top end speed, the 6x4 APC didn't spool up as fast, but delivered best top end speed.

Why I bring this up is that for our next NAMC modification of the RCP Mig29 V4, Stephan and I are going to try and build a hybrid plane that has enough strength to handle the punishment and weight of the NTM 2700 power train without making it too heavy so that we can still effectively use the FP 2700 as well.  Basically one air frame with two different power train options.  It will be an interesting challenge, but one that I'm sure we are up to... :)

Essentially once the air frame is completed, the difference in power trains will be as follows based on weights I took last year when I did all the motor testing.  Your weights may vary depending on what ESC and/or battery you use.

Focal Price motor setup

• FP 2700 motor with 6x3 EMP prop - 65 gr/2.3 oz + Turnigy Plush 40A ESC - 41 gr/1.5 oz + Turnigy 1600 Mah 3S 30-40C discharge battery - 147 gr/5.2 oz - total weight of 253 gr/9oz.  If we use the 2200 Mah battery which I like to use depending on airframe weight, it brings the weight up to 303 gr/10.7 oz

NTM 2700 motor setup

• NTM 2700 motor with 6x4 APC prop - 99 gr/3.5 oz + Turnigy Plush 60A ESC - 70gr/2.5 oz + Zippy Flightmax 2200 Mah 3S 40C discharge battery - 197gr/6.9 oz - total weight of 366 gr/12.9 oz.

So here is where things get kind of interesting...

With the 1600 Mah battery option for the Focal Price motor, the power train alone produces 4 oz of thrust for every ounce that the power train weighs.

The NTM 2700 setup produces 3.3 oz of thrust for every ounce that the power train weighs.

More than likely, oz for oz, the NTM setup will produce a greater top end speed because of the prop, but the Focal Price setup will have better initial pop and acceleration for some quick agile moves and aerobatics because of it's prop.  Both these setups I find give me about 5 minutes of flight endurance.  Of course, using 4S with the NTM 2700 for some blinding speed is a lot of fun too for those of you with a bit more experience, this gave me a thrust to weight ratio of 2.2:1 and a top speed of 109 mph... :)

Unfortunately, the Focal Price 2700 runs way too hot when trying to use a 6x4 APC prop and trying to use a 6x3 EMP prop on the NTM Prop Drive wastes horsepower, so it is not really an option to swap out props with these two motors as a way to have different thrust to weight ratios.

So you might say, well that is all good for you as you have a couple years experience and like to fly a little faster (probably 90% of my flying is at 50% throttle or higher) and more scale than some folks do, what about someone just starting off or someone who doesn't like to fly as fast or expect the performance that you do?

Interesting question and while I am well on my way to another good "ramble fest", why not look at some different numbers dependent on what you might want your airplane to do or what it is capable of doing dependent on your build and flying experience.  As beginners, we probably all build a little heavier than we should, but that is fine, all part of the experience.  I have learned that after building 40+ park jets, that light but strong is the best setup.  It takes some time and experience to know where to spend the air frame weight to gain the strength and where to save it which is why scratch building is so much fun and rewarding, each new build is a learning experience and a chance to experiment.

So, if I look back to all the testing I did with my RCP F18 V3, I ranged in weight from 17.3 oz to 21.5 oz depending on the motor/ESC/battery combo I tested.  I ranged from 1.2:1 to 1:8:1 in thrust to weight ratio.  With the F18 top end speed is not a real factor since at a certain point, drag becomes too much, but having that "hole shot" power is helpful for aerobatics and powering out of high alpha.

So at 1.2:1, the plane flew OK, would move along well, but had very limited vertical capability, maybe about 50 ft straight up in the vertical before it just ran out of "oomph".  Also, punch out power was fairly limited, so I didn't have that emergency acceleration I might need to get out of trouble.  I was light at 17.3 oz with the Grayson Hobby MJV3, but very limited power range and got bounced around quite a bit in the wind.

Since I have already discussed the higher end thrust to weight ratio and what power setups I use to achieve this, let's look at the mid range where a lot of folks might be if using the recommended power setups from RC Powers.

Hobby King Turnigy D2826/6 motor setup

• D2826/6 motor with 6x4 APC prop - 67 gr/2.35 oz + Turnigy Plush 30A ESC - 34 gr/1.2 oz + 1600 Mah 3S battery - 147 gr/5.2 oz - total weight - 248 gr/8.75 oz.  The thrust per ounce of power train with this setup is 3 oz of thrust per oz of power train.

In bench testing, I found that with a 6x4 APC prop, the best setup was with medium timing on my ESC, the thrust produced is 750 gr/26.5 oz.  On my F18 V3, this setup took me to 17.8 oz, so a thrust to weight ratio of 1.5:1.  For most folks starting off, this is a pretty light weight and if you are using hot glue, you might only get to this weight by using two servos and elevons only and keeping the paint application to a minimum (magic marker works great for a quick paint scheme and adds zero weight).  The plane flew very well with this motor, much better punch out, overall performance and speed than the MJV3 and would be an excellent overall starter package for a beginner or folks not really needing or wanting to fly too fast.  In effect, your plane could weigh up to 22 oz with this motor setup, which would give you a thrust to weight of 1.2:1 and about the same performance I describe getting with the MJV3 with my F18 V3.  Much heavier than that in all honesty and you are going to have to fly around at a pretty high throttle setting and won't have much power in reserve to get yourself out of trouble which is always a good thing, especially when starting off.

As a side note, when bench testing the D2826/6 motor and the 6x3 EMP prop, I got about 30 oz of thrust and much better pop and acceleration at the field when flying.  Top end speed difference was not noticeable, but again I was flying a "draggy" plane in the F18 V3.  Additionally, the motor ran much cooler and more efficiently with a 6x3 EMP prop.

So, to try and make sense of this all, "thrust to weight" ratio should be considered an important part of how a plane is going to perform and a factor that should be considered when building a plane.  It is always a trade off, normally the lighter the motor, the less power it produces, the heavier the motor the more power it produces.  Where the balancing act really becomes interesting is that with a heavier motor, normally a heavier ESC and battery are required and more reinforcement is required to handle the wing loading and punishment the big powerful motor will produce.  As mentioned earlier, greatest success and flexibility is achieved by keeping the build as light as possible (using light, strong glue like Foam Tac) while keeping it strong.  I would rather have a light plane that I can have the flexibility to add weight by putting in a heavier battery than have a heavy plane that will only fly and perform well with a light battery.  With bigger motors like the NTM, heavy batteries are pretty much a must as you need the capacity and C rating to feed that beast of a motor.

So you might say, well if I am going to build heavy and want extra power in reserve, why not just start off with the NTM Prop Drive?!  Well, I can tell you from experience this is really not a good choice for beginners as the extra torque, weight and power can get you into more trouble than it will get you out of.  The Turnigy D2826/6 package recommended by RCP is probably one of the best all round choices to start off with.  If you want to give yourself flexibility for starting off, get a 40A ESC for your D2826/6 and then for just about a $12 investment, you can upgrade to the Focal Price 2700, gain about 10 oz of thrust without having to change anything else...like flying a whole new plane with just an easy motor change and the increased speed and acceleration is big time fun... :)

If you are looking for some more help in choosing a motor/prop combo or want to have a better idea of what your current setup is giving you (as long as it is on my spreadsheet... :)), post #127 of this thread on the RC Powers site has the latest version of the spreadsheet I produced when I did all the bench testing of popular park jet motors last year http://www.rcpowers.com/community/threads/parkjet-motor-bench-testing.15685/page-7  I would encourage you to go have a look at this and download it, it can be very helpful in determining motor and prop choice dependent on what your airplane might weigh or what you think it might weigh at completion.

So hopefully this rambling has been helpful in demonstrating how thrust to weight ratio might be important in how you like to build and fly.  While many of the numbers I quoted and calculated are fact, how they performed at the field is primarily from my opinion and assessment of the plane/power setup and it's performance in the framework of how I like to fly.

Please don't hesitate to post questions or comments on this or any of our posts if you are looking for help with a build or just want to discuss something.  We don't have all the answers, but might be able to shed some light on another way of looking at things if you are looking to try a new power setup or are looking for some different performance characteristics from your plane(s).  And besides, we both just love planes are are more than happy to talk about them... :)

Cheers,

Scott

"Honey, you have too many planes" + Crowd Watching You Fly =

Teenage Male Driver + Girls in the backseat =
Driver + Texting =
Pilot + Disregard for Checklists =

CRASH

Yep, crashed at the field today--twice!  First one I was not showing off and had no intention of recycling my Blue Angels RCP F-22v3.  She won't get recycled but she'll need a rhinoplasty.  Somehow at launch, I bumped and killed the throttle.  Down she went nose first.  Still flew great.  The F-22 is a lot fun, as long as you are flying at half to full throttle.  At slow speeds she can get squirrelly as there is no air flow over the vertical stabilizers.

Second crash was reminiscent of the F-16 Thunderbird crash at Mtn Home AFB in 2004.  I was doing crazy giant loops with souped up NTM Prop Drive 2700 Mig-29v3M3 and came in a little short and hit the ground.  Embarrassingly not the first time I've done this.  How low can you go?  I really do enjoy mowing the grass with these planes.

Just before I went I flying my wife commented that I had too many planes.  Yep, there were a couple of gawkers and I was pushing the limits.  No need to shed tears, building is therapy for me.  Honestly, I get as much satisfaction reading about aerodynamics, designing modifications, and building as I do flying.

Lessons learned today
1. Hide your airplanes from your wife
2. Don't fly in front of a crowd, your inner teenage boy will come out and you'll do something stupid

V4 or V3 Tail Plate?

In the v4, the tail plate grew in width and length.  Additionally, the shovel angle of the vertical stabilizers was increased.  I firmly believe that the design change that had the most effect on improving the stability of the v4 over the v3 was the addition of a horizontal stabilizer.  I think that the increase in the surface area of the tail plate contributes to undesirable EPPE.  Aesthetically, v4 has too much back for me.

This first picture is a comparison of the wing plates to which I added the side plates.  You can see the 1/2 increase in overall width of the tail plate and the slight increase in the shovel  angle.

Here is a comparison of the v4 and v3 tail plates (note the elevons are M3e3 modifications)

In thinking about my next build, my goal is continue to minimize EPPE and improve the aesthetics.  So I will modify the wing plate back to v3 width and shovel angle.  I will also modify the tail plate to v3 size.  I prefer the look of rear swept leading edge on the tail plate.  Once I start building, I'll document how I did the mods.  Here is the new tail plate (green):

Servo and Radio Settings Spreadsheet

I just figured out that I can't add file to a posting that is a "comment."
So here is the spreadsheet I mentioned in my comment to Scott's posting on dialing in a plane.
Stephan

Some thoughts about "dialing in" a plane... :)

Hi everyone -

Now that I have pretty much dialed in another plane, I thought it would be a good time to post my process for how I like to dial in my planes to have the best setup and chance of long term success and enjoyment.  This post will probably take longer to write than the process takes itself, but hopefully there will be a few tidbits that might be of use to you.  As the old saying goes, "the devil is in the details" and being and old Air Force operator, I am big on processes and checklists... :)

Another caveat that I should add is that though some of these points might seem painfully obvious, sometimes in my rush to get a plane to the field to get flying, I have missed them and paid the price.  In the almost two years since I started scratch building park jets, I have maidened over 40 planes, most of them successfully, but often not without moments where I lost a few thousand heartbeats in panic!  And at my age, I can't afford to lose too many more heartbeats to self induced stupidity... :/

So like many things with my planes, it starts with the build, I try to build as light as I can but still keep my planes strong and hopefully durable.  Ensuring the control surface hinges are secure, that control horns are lined up as close as possible so that the holes are directly over the hinge, pushrods and other linkage components are in good condition and secure and that all the electronics, motor, ESC, RX and servos have been bench tested before installation in my plane.  All common sense stuff, but there have been times in a rush to get a plane finished I have missed one of these steps and like having a poor foundation on a house, it has cost me at the field.

Once I do have my servos installed in the plane, I discipline myself to let the glue on them completely dry so that as I am connecting the pushrods, etc I don't work them loose or weaken the glue joint before it has hardened.  Again, lesson learned!

I currently run a Turnigy er9x radio system, so I am able to do the bulk of the initial configuration of my radio setup through my PC which saves considerable wear and tear on the buttons of the radio.  I run through everything to ensure that I haven't put in any subtrim or other weird travel adjustments that might affect me getting my plane setup with a clean slate right from the start.

 Before doing much of anything else when hooking up my system, I always ensure I re-bind the Tx and Rx.  Then I set the throttle points on my ESC.  Even if I have used this ESC before, I always do this, especially if I am using a different receiver than I used with the ESC in the past.  It is a bit anal, but it gives me the confidence of knowing that my ESC is set properly for this setup.

Your ESC might be different, so check the manual if you have one either in paper on online to see if setting the throttle points might be different.  I think the lion's share of ESCs are the same for this setup.  I use Turnigy Plush ESCs from HK, 40A with my Focal Price motors and 60A with my NTM 2700 motors.  Before starting to set the throttle points, I will connect my ESC to the programming card to double check that all the other settings on my ESC like brake (I fly with mine off), timing, etc are all where I want them to be.  If the brand of ESCs you like to use has a programming card, I would highly recommend picking one up.  The Turnigy one for example is about $8 and for the cost, it saves a lot of hassle with doing it through the transmitter and gives me the confidence that my ESC is going to do what I want it to.

Setting throttle points is normally done before I put the prop on the motor, just in case something crazy happens, I don't have my plane fly off the table or worse yet hurt myself with a prop that is suddenly spinning at 30,000 RPM.  The motor is connected to the ESC for this process, so I turn on my transmitter, advance the throttle to full or 100%, then connect the battery to the ESC.  I then should hear one beep followed by two beeps in quick succession, I then chop the throttle to zero and I normally hear one beep, followed by 3 beeps for the number of cells in my lipo and then a single beep letting me know the throttle points have been set.

So now I should have all the gear installed and connected.  I use a throttle cut safety switch on my transmitter to ensure I don't accidentally advance my throttle while I am playing around with the sticks, if you don't have this feature or don't feel confident your motor won't start up unexpectedly, you can leave the prop off while going through the process of checking all the control surfaces.

So all my servos are now in the correct configuration and channels on my receiver and it is time to fire things up and see where we are at.  I connect my battery and wait for everything to initialize.  Often the control surfaces won't be perfectly centered, so I first check that I have all my trims at zero, then I mechanically center them with the quick connects I like to use or you can use whatever you have like adjustable clevis, etc to ensure the control surface is as close to dead center as you can get it.

So now that all my surfaces are dead center, I check that they are moving in the correct direction.  I always pay close attention that they are moving in the correct direction and not just a quick waggle of the sticks to ensure they move.  Ailerons are the worst culprit of this, I still see guys at my field give the sticks a quick waggle, take off and then realize that although their ailerons were moving, they were going the wrong way, so left is right, right is left...you get the picture...it often results in a short walk of shame after cranking the plane into some immovable object... :(

Since I have a very easily programmable transmitter, I will also fine tune my elevons and ailerons to ensure that when I pull full up on the elevator that both elevons are equal.  If one comes up a bit further than the other, every time I pull up in a loop, it will roll at the same time and cause other issues of imbalance in handling.  Fortunately with the er9x, I have huge flexibility in mixing and programming, so this is very helpful in achieving the control surface throws I am looking for.  I will also use a ruler to ensure that my ailerons travel the same distance to prevent my plane rolling faster one way than the other.  All a bit anal, but well worth it.  My personal choice for starting throws and expo is 70% throws on aileron and elevator with 50% expo on the elevator input and 60% throw on the aileron.  For the rudders, I start with 100% throws and 50% expo.  I don't bother with low and high rates, just personal preference.

So after a quick check to ensure all my hinges, control horns, servos and linkages are good and secure after all the adjusting, I get ready for battery placement as long as I have already installed my prop and ensured it is running in the right direction.

Unless I specifically know that a certain plane is always going to have the center of gravity (CofG) ahead or behind what is marked on the plans, I balance my plane using the stock CofG per the plans.  I also find this is easiest to do at home in the house so that no wind will affect my plane balancing properly.  I use a fully charged battery so that when I get it balanced, I just leave that battery in until I am ready to maiden it at the field.  I like to have my plane balance right on or perhaps very slightly nose heavy, maybe about 10 degrees nose down for the maiden.

When I get to the field, I like to take one plane that I am already very comfortable with and fly that a couple times just to get my brain and thumbs warmed up.  Even after over 40 maiden flights, I still get nervous flying a new plane for the first time and find that if I put a couple batteries through a plane that I am familiar with, it helps calm my nerves and gets things warmed up.

I normally launch my planes with about 45-50% throttle and then just climb away gradually until I am up at about 100 ft off the ground (at least two mistakes high, whatever altitude that is supposed to be...:/) and then keep it out in front of me so that I can figure out what trim it needs.  I do this by flying it perpendicular to me (so that I am looking basically at the side of the plane as it flies by) and then center the right stick so I'm "hands off" (I fly mode 2) and seeing what it does and adding trim accordingly until when I let go of the stick it pretty much flies straight and level without control input.  I normally just trim in the roll and pitch (aileron and elevator) axes, I don't worry too much about the rudder, I just check them regularly to ensure they are always dead center and not causing me trim issues.

Then once I have completed that first flight, the fine tuning begins.  I am always in search of the ability to fly my plane balanced and straight and level with no trim input if I can, I find it just allows my planes to fly better and I am not dragging around any deflected control inputs because of trim.  Although not always possible, this is easiest done on the calmest day possible so that wind is not a big factor in me getting my plane trimmed the best way possible.

I find it easiest to solve the trim one axis at a time and I normally start with pitch.  If the plane was nose heavy, I move the battery back slightly.  If it was tail heavy, I move it forward.  Not that this is a hard and fast rule, but I find most planes that 1/4" of battery movement (with a 2200 battery anyway) is equal to about one click of trim, but I do this very gradually.  Then for the next couple flights, I just keep flying and adjusting the battery backwards or forwards until I get it to the point of zero trim in the pitch.  Sometimes I will even land a couple times during a flight, make an adjustment, continue on.  In drastic cases if I can't get it down to less than one or two clicks of trim (which I can live with if I absolutely have to), I will try to move my ESC and/or Rx forward or aft to help achieve that neutral balance.

So, once I am happy with where my battery is for balance in the pitch, I mark the foam with a magic marker so that I can continually put the battery in the same place time after time.

Then I solve for the roll axis if need be.  I would say that with about 90% of my planes, I end up with the battery all the way over to the right to compensate for torque roll and roll is often the most difficult for me to get to zero trim.  Again, if I have one or two clicks of trim, I can live with that.  I am not a big fan of adding extra weight to a plane to get it to balance, but I will if I find that I need excess trim to get it to fly straight and level.

Then once I am happy with where I have put my battery, if it is considerably different from where it was in the pitch axis for the maiden flight, I leave the battery in and starting at the old CofG, I try to balance it again on my fingers (I like to do this with the plane upside down, just my technique) and keep moving the plane on my fingertips until it balances perfectly.  Again, this is easier done indoors if you can so no wind affects the plane.  Then I mark on the wing (normally I just put a little dent in the foam with a nail or make a little mark with a marker) where the true CofG is for that plane.  That way, if I decide I want to use a different size battery, I know where the plane needs to balance and I don't have to go through the process again.  As you have probably seen on my stock Mig29 V4, I ensure to label the marks in the battery bay so that I know where a 2200 battery goes and where a 1600 battery goes.  This prevents me from putting one where the other should go...again, lesson learned the hard way!

Within the first 6-10 flights, I also double check that all my control surfaces have stayed dead center with zero trim.  I have found that as hinges get broken in and linkages get worked in that sometimes the control surface can be off center slightly and I might end up trimming against that slight deflection.  Again, anal, but worth it in my experience.  Then I check my plane each time I take it to the field before the first flight of the day just to ensure nothing in the control surfaces has become loose, servos, pushrod connections, control horns, hinges, etc.

Then as I accumulate more flights with that plane, I will start to assess the requirement to adjust any throws and expo.  I rarely will adjust my expo from the start, but sometimes I will add more throw like I did with the Mig29 V4M3e3 to get it to fly close to scale and the way I like to fly.  If you like to fly more aggressively or more gently you can adjust accordingly.  Then I will also assess and adjust any flaps/spoilers I might be using for high alpha or landing or other such portions of the flight envelope.  This is simply trial and error to find what deflection of spoiler/flap/spoileron/flaperon might work best for a specific portion of the flight envelope where these special control surfaces may be utilized.  For things like high alpha, I might also temporarily adjust my battery position like I did on my stock Mig29 V4, I found that having it further forward was better for more steady high alpha.

I have several planes with over 100 flights on them and have found that sometimes over time, a plane seems to gain weight either in the nose or the tail.  I know this is not the case, but perhaps as the foam gets more flexible over time, it seems to affect the balance, so as your plane accumulates more flying time, you may have to readjust your battery position and once again determine the new CofG.

So if you are still awake after working through all this stuff, I hope at least some of it might be helpful to you or give you some other ideas to consider when dialing in your plane.  For the longest time I didn't really worry about it, I just flew with lots of trim and thought I had to live with it.  But as I started to improve and challenge my skills to fly more scale and more precise, I knew I had to get my planes setup to allow for this.  It makes a huge difference in how my planes fly and how predictable they become when I can trim and balance them as close to zero trim as possible.  Some planes dial in faster than others, but it is fun to go through the process and the rewards are worth the tedium...at least in my humble opinion.

Like many things in RC and especially scratch building planes, there are numerous ways to achieve the same goal, so I don't think for one minute I have presented all the answers or what might even be the right answer for how you like to fly.  Much of what I have written I have learned the hard way or borrowed from other folks at the field or in posts I have read in different forums, sometimes just trying new things can be fun and could be a breakthrough in helping with a particular process in your RC adventure.  Good luck!

Cheers,

Scott