RCP Mig-29 V1M walkaround video

Hi Everyone -

I managed to shoot a walkaround video discussing in more detail the mods I made and giving my feedback on what I thought was and was not successful with the mods I made not that I have flown the plane.

Cheers,

Scott

RCP Mig-29 V1M build and maiden complete

Hi everyone -

I finished up my Mig-29 V1M build late yesterday and managed to get it out to the field today for a good "thrashing" (14 flights in total) ;).  Snapped a few pics of the finished plane before paint.

For some reason, I ended up a little heavier than I forecast, with 2200 battery I am at 510 gr/18 oz.  

You can go back through previous posts to find the details on all the mods, but essentially as a quick recap since it will relate to my flight report findings, here are the mods I made

• added KF4 airfoils made of paperless dollar store foam, 41% of chord at the root, 35% of chord at the tip, leading edge symmetrically shaped and sanded;
• added ailerons;
• scaled down the height of the vertical stabs and added rudders, I also angled the vertical stabs out 3 degrees each to create a "wedge" for greater stability in the back end; and
• scaled down the size of the elevons and created a fixed horizontal stabilizer rather than the elevon balancers on the stock plans.

Power/control setup 

• Gear Best 2212/5T 2700 Kv motor with 6x4 APC prop;
• Turnigy Plush 40A ESC;
• Zippy Flightmax 2200 3S 40C discharge battery;
• two 9 gram RC Timer nylon gear servos for the elevons;
• two 5 gram RC Timer nylon gear servos for the ailerons;
• two 5 gram RC Timer nylon gear servos for the rudders; 
• the elevon and aileron servos each have their own channel, rudder servos connected with a Y harness so that I could use the lighter smaller 6 channel receiver compatible with my Turnigy 9x transmitter (with er9x upgrade).

I started off balanced on the stock CG from the plans, in this picture you can see three blue "+", the furthest on the left is the stock CG, I ended up 1" ahead of that as indicated with the hex driver.

This is where my 2200 battery ended up to give me that neutral balance point.

For some reason I seem to remember my battery being in the same place with my previous Mig-29 V1s, but I was still balanced on the stock CG...or was I?  Long ago and my old brain probably doesn't remember exactly.  Anyway, this is the setup that seems to give me the best neutral balance when I do the arc test and inverted flight.

I put the battery right on the centreline of the plane for best performance, fortunately I only needed about 1 click of right trim to counter torque roll and no trim in the pitch or yaw, sometimes you just get lucky :)

Before I go further into discussing how I felt the mods worked out, here are what I ended up with as final throws to allow me to fly scale and have a bit of "emergency" throw in the pitch for "object avoidance" :)

• elevons 5/8" one way (1 and 1/4" total) in the pitch, 7/8" one way (1 and 3/4" total in the roll;
• ailerons 3/8" one way (3/4" total); and 
• rudders 5/8" one way, (1 and 1/4" total)

I am flying with 15% expo in the pitch and roll and 25% expo in the yaw.

Affects of the mods

KF4

Almost right away I could feel the added stability and "locked in" feeling provided by the KF4 airfoils, everything the plane did just seemed smoother and even more direct in it's tracking, very pleased with that change.

Ailerons

I know this plane would be fine without ailerons, but since I like to fly all my planes with them, I did notice better balance in turns and rolls having the ailerons rather than just all the control surface deflection coming from the rear with the elevons.  Again, perhaps personal preference, but I found them to be a good addition.

Vert stabs/rudders

This is probably a combination of the reduced size of the elevons and vert stabs/rudders, but I did feel less drag as I was flying.  I will admit, I probably went "overkill" on the rudder size, if I was to do it again, I would probably cut them down by almost 50%.  Even with the small amount of throw I have and expo, rudder input has to be very smooth and subtle or it will cause the plane to "snap rudder roll" which looks cool, but not too scale and would be less than ideal if I was low level, so more work to tune those in as I explore slow flight and high alpha.

Reduced elevons/horizontal stabs

I have been a big fan of this setup ever since trying it on the stock RCP Mig-29 V4, I like the extra stability it brings to the back end of the plane.  I had actually forgotten how responsive the Mig-29 V1 was in the pitch.  I initially maidened it with 1" of deflection (2" total) in the pitch and after scaring myself executing a loop when I thought I was just climbing, I toned that down immediately to find more ideal scale response in the pitch.

Overall impressions

I have always been a big fan of the RCP Mig-29 V1, it has been a very important plane in my development as a park jet pilot and right away it brought back fond memories of how much fun it is to fly.  However, since my flying style and skills have changed over time, I look for a plane that is balanced yet responsive and allows me to continue working on my scale flying skills.  

Obviously it still has some profile characteristics as with all those flat surfaces in the "fuselage" it can get bounced kinda funny by the wind sometimes and with the nose being a flat part of the wing plate it does tend to float and not maintain it's momentum like a score and fold park jet.  Having said all that, I found the mods I added helped the plane fly and feel much closer to a score and fold plane than I have ever experienced before with a profile park jet.  It was a lot of fun to see how a few simple changes made such a difference to the flight experience.

Time to put some paint on her and look forward to lots of ripping up the skies with the RCP Mig-29 V1!

Cheers,

Scott

RCP Mig-29 V1 build update #3

Hi everyone -

Another busy day puttering with my RCP Mig-29 V1M, I am in the home stretch on the build now :)

Here is a picture of it head on now, starting actually look like a jet, the vert stabs are just dry fit for now for the picture.

I glued the nose and wing plate together and after the glue dried, I cut out the center "fin" to give me more room to move my battery around and make it easier to install the rest of the electronics gear.  Here is a before picture with "fin" still there waiting for glue to dry.  

In this picture, you can see where the "fin" has been removed and velcro run back for battery placement.

Today after hooking everything up to make sure they work, I installed the servos, ESC and receiver and put in some velcro to hold the battery.  I used a trick I learned from my last Mig-29 V1 build and used a zip tie to secure my ESC.

On the outside of the intake/nacelle, I put a little piece of popsicle stick to keep the zip tie from tearing the foam :)

Here is a picture of the electronics bay from the rear, motor will be mounted after final sanding so as to prevent any dust/debris getting in the motor.

Showing the servos, from left to right, aileron, rudder and elevon, pushrods and control horns will be installed in the next stage of building.

KF4 airfoils installed and taped down, I will let the glue dry overnight before shaping and sanding the leading edge symmetrically.  Here is a picture of the rudder servo from the top, counter sunk into the top KF to help keep it out of the way.

Hope to get final finish and sanding done tomorrow, motor installed, pushrods connected and everything set up to be ready to fly before the end of the week.  Unpainted with a 2200 3S battery, I anticipate my weight to be around 480 gr/16.9 oz.  Hard to believe how heavy I used to build my planes.  My first Mig-29 V1 with only two servos, no KFs and nowhere near as much reinforcement weighed 19 oz/540 grams with a 2200 battery!  Even after painting, I will still be under that weight with KF4, 6 servos and linkages and lots of extra reinforcement.

Next update will be when she is one and ready to fly :)

Cheers,

Scott

RCP Mig-29 V1M Build update #2

Hi everyone -

I made quite a bit more progress on my RCP Mig-29 V1M today.  Sorry, the first one is a bit of a blurry picture :/   I first sanded the leading and trailing edges of my elevons/horizontal stabilizer, installed some bamboo skewers for reinforcement in the elevons, back plate along the horizontal stab, in the vertical stabs and along the nose as you can hopefully see in this picture.  This is a function of the Fli-Power Value XPS foam I am using for this build.  As I was handling the pieces, I found them to be very flexible and thus far these reinforcements seem to give my wing plate about the same rigidity as Depron.  So lessons learned there and when I am done this build, I will write a post about building an entire plane with this foam.

I also installed a 20" piece of 4mm carbon rod just behind the prop slot for my wing spar.  Given the flexibility of the foam and the fact I want to use a 2200 3S 40C battery for most of my flights, I wanted some extra strength and wing loading capacity.

You can see I also cut out holes in the wing plate to accept my rudder servos.  I would normally run these a bit more inboard, but if I did that, the pushrods would interfere with the prop slot.

In this next picture, you can see I expanded the prop slot just a bit, put some transparent duct tape on the bevelled side of my elevon hinges for extra insurance and installed the two side pieces.  My next step will be to install the elevon and aileron servos and pushrods with the plane as is since this is easier to do with the battery bay wide open like this and the plane laying flat on it's back.

I also measured and cut out my top and bottom KF airfoils to make the KF4 I want.  For now I am going with about 41% of wing chord at the root and 35% of wing chord at the tip.  These dimensions work really well on the NAMC Mig-35, so since it is a very similar wing, I will start there.  The slots cut out are to accept the rudder servos.  I will now use these as templates for the other wing.  Once I figure out if these dimensions work well, I will take some measurements and publish those in a follow on post.

I hope to have her ready to fly in a couple more days, much of the rest of the build is a bit fussy getting the gear installed and sorted out, then I always like to leave a plane overnight once it is done to let all the glue cure (ask me why I do that... :/) before flying.

I have a paint scheme in mind, but won't paint until I put a few flights in it in case I need to trim anything off with my knife like the KFs, etc.

I'm very happy with how it is shaping up thus far :)

Cheers,

Scott

RCP Mig-29 V1M - build update #1

Hi everyone -

I have all the pieces cut out for my Mig-29 V1M other than the KF4, I will wait until I get the wing plate all put together since I will have to do some measuring and tracing around the leading edge and wing tip to get the right dimensions before cutting those out.

I tried to remember to take pictures as I went along, so starting from the back, here are my modified elevons.  Similar to the F18 V3M project, I looked at diagrams of the Mig-29 to get a ratio between the wingspan and the elevon span to determine how much I needed to reduce the elevon to make it more scale.  This will also give me slightly smaller control surface, but that is OK as it should also reduce drag, improve stability and speed.  The area highlighted in orange is how I added some lines to make sure I could still match the hinge line on the back plate.  I also wanted to change the "nozzles" a bit as I always found them a bit too "pointy".

After getting my drawing done, I then cut this new elevon from scrap foam to use as a template so when I cut out the back half of each wing with the back plate, I could trace out the elevon and cut it off so that I still have the fixed horizontal stabilizer attached to the back plate.  

For the shortened vertical stab, I used one of my NAMC Mig-35s for reference as I knew that Stephan had made those plans scale, measured that and then sized it accordingly for the smaller Mig-29 V1.  It might look a little "squat" on the top, but we'll see.

To get the "wedge" where the vertical stabs are angled out to help with yaw stability in turns as well as high speed stability, I made the following change to the slot that accepts the tab from the vertical stabilizer.  I also moved the slot outboard about 2mm, I know that isn't much, but given that the back plate is fairly narrow, if I moved it out much more with the new angle I am using, the back of the vert stab would not stay on the top of the back plate.

For the ailerons, I used the dimensions of the ailerons on the NAMC Mig-35 and scaled down accordingly for the smaller Mig-29 V1M.

This build should come along pretty quickly, as long as flying doesn't get in the way ;).

Cheers,

Scott

Modified RC Powers Mig-29 V1 - initial thoughts

Hi everyone -

I guess I must be in a bit of nostalgic mood these days since finishing up my modified RCP F18 V3 as I decided to build another favourite of mine, the RCP Mig-29 V1 after finding a set of plans collecting dust in my closet.

The RCP Mig-29 V1 has been around quite awhile (over 6 yrs now according to the date of the thread on the RCP site and is definitely my favourite profile park jet of all time.

Here are some pictures of three previous builds in chronological order.  I wasn't keep track of my flights in those days like I do now, but if I had to estimate, I would have about 500 flights on these three planes combined :)

Since first flying this plane almost 3 yrs ago, I have often thought about playing around with some different mods I would like to try both for form (looks) and function (performance).  I've only ever flown this plane elevons only, no KF airfoils, nothing fancy.  I'm not going to mess around with motor location or worried about proving concepts like I did with the modified F18 V3M build, I just want to "jazz it up a bit" and have some fun.  

I think it will be a great plane to thrash around over the winter, here is proof of how tough it is, after this "mishap", I just pulled it out of the dirt, cleaned it off and kept on flying!

So here is what I am thinking thus far for build modifications

• scale down the size of the elevons to make them more scale proportions, from initial measurements and calculations, this will only need to be about an 8% reduction;
• use the horizontal stabilizer/elevon combo rather than the full floating/flying elevon that it has stock;
• reduce the height of the vertical stab to a more scale height and add rudders;
• in addition to reducing the height of the vert stabs, I am going to widen their stance ever so slightly and angle them out about 3 degrees from front to back, giving that "wedge" almost that has been proven to help with stability ever since the RCP Mig-29 V3;
• I will add ailerons, using the NAMC Mig-35 elevons as reference and just scale them down accordingly, the motor on the Mig-29 V1 is actually further ahead on the plane in relation to where the motor is on the Mig-35, so it might be fun during the calmer winter months to play around with some high alpha with it, so having ailerons will allow me to play around with spoilers/flaps;  and
• I will add KF4 airfoils to help with speed and stability, I have never tried them on a profile plane, but I'm thinking they can only help performance.

I am going to experiment with using Fli-Value XPS foam for the entire build (other than paperless dollar store foam for the KFs) as I think with the Mig-29 V1's small size and where some key glue joints are when forming the wing plate, it will be a good choice to use this inexpensive foam that is not quite as stiff as Depron.

I think this plane will be a great platform for the Gear Best 2212/5T 2700 Kv motor  and 6x4 APC prop combo that I have had good success with lately, I have a second one just screaming to get into a plane!  You can read more about my testing experience with this very inexpensive motor in this blog thread on our main NAMC website.

To try and keep it a bit lighter and since the rudders and ailerons aren't that big, I'm going to use some RC Timer 5 gram servos I have around waiting for a home :)  For the elevons, I will use RC Timer 9 gram servos that I use on almost all my builds.

So time to get out the pencil, ruler and dollar store calculator and work out what I need to do to make all the above build mods possible, more to follow very shortly.

Cheers,

Scott

RCP F18 V3M Walkaround video

Hi everyone -

I did a rather detailed walkaround video to summarize the process I went through when planning and building this modified plane to perform with more agility, precision and quickness.  I still have a bit of testing to do, but I am about 95% complete with what I wanted to evaluate.

I will also be writing a synopsis on our NAMC blog to discuss how this process was in line with out philosophy of "Think, Design, Test and Validate" and how certain scientific factors stayed true to a very different air frame and wing type and what I discovered did not carry over from a swept wing plane to a straight wing plane.

Cheers,

Scott 

RCP F18 V3M Field testing - Day #3

Hi everyone -

I managed to get another great testing session done yesterday with my modified F18 V3M.  I managed another 10 flights for a running total of 28 flights.

I am pretty satisfied that the main "dialing in" process is complete, I think there will still be a bit of tweaking for good high alpha flight, but since that is a rather extreme portion of the flight envelope, it will take some time.  Also, it relies on dead calm winds and me getting my "high alpha thumbs and brain" back which could be the longest part of the process :/.

As I mentioned in my last flight report, I did increase the deflection on my ailerons, increasing it now to 5/8" travel one way (1 and 1/4" total) which gives me noticeably crisper and snappier rolls.

KF airfoils

I have decided that the KF airfoils are just fine the way they are, I think if I did any more tweaking there, I might be chasing my own tail, as it flies now, I think that the CG and CP (centre of pressure which can be greatly affected by KF dimensions I learned from experience with the Mig-35/Mig-FA) are in excellent harmony :)

When testing the Mig-35/Mig-FA, we found we got a really "locked in" feeling when the trailing edge of the KF intersected at the point where the CG met the fuselage.  As we were testing and making the final adjustments to the CG and KF, you could almost feel as the CG and CP started to be in harmony.

With a more straight wing plane like the F18, this does not seem to be the case.  As you can see in this picture, I made a mark on the fuselage where the CG would intersect it.  The trailing edge of the KF is about 1 and 1/2" behind this point and the plane feels solid and very well behaved.  To help understand what I mean by the CG and CP being in harmony, as we were testing the Mig-35, on one of the first prototypes the trailing edge of the KF was almost 1/2" behind the CG and as I would try to pull out of an aggressive loop, split S or power dive, there was a definite lag in rotation and required much more up elevator to prevent union with terra firma!  Also, quite often in a turn, the nose would wander or the plane would feel rough like it was fighting itself, throwing a tantrum like toddler.  As these two came closer together, it became a much happier park jet.  Anyway, those were the behaviours I was looking for as I dialed in the KF dimensions.



As you can read from previous flight reports, I moved the CG back 3/4" from where I originally suspected it might be, so I did start to notice some of these adverse behaviours, but after trimming 1/8" off the back of the KF top and bottom, things smoothed out again.  Expressing the KF size in percentage of wing chord, it is 40% of chord when measured at the root along the fuselage and about 38% at the wing tip.

This is a far less tapered type of KF as you might expect from a straighter wing.  By comparison, the KF on the Mig-35 which has a much more swept wing is 41.5% at the wing root and 35% at the wing tip.

If just for testing sake I put the trailing edge of the KF on the F18 at the point where the CG meets the fuselage, I would only have a 21% KF, I think I might as well not have KF at that point as I would lose the stability they provide if they were that small.

High alpha performance

If you read through the RCP F18 V3 thread on the RC Powers forum, you will notice that many folks, including me, tended to fly high alpha with the battery quite far forward for best high alpha performance and stability on the stock F18 V3.  It almost felt that once you got the nose up there, the plane was "leaning" on something with that long moment of inertia.

As you might expect with a much shorter moment of inertia like I now have, this plane still performs very good scale high alpha (40-45 degree AOA), but the "slot" for staying stable is smaller.  The plane feels like it is balanced on a much smaller spot and when you have it on that spot, it stays very stable, but as you get close to the edge, it does "fall off" a bit more quickly.  So as my "high alpha thumbs/brain" come back I will continue to practice more and work to get it down lower.  Right now, lots of altitude is my friend as I practice :)  Like many things as you change things around on a design, there are points of compromise.  As my skills come back, I think it will still be an excellent high alpha platform.

I could of course put the battery further forward, fly it nose heavy just to do high alpha, but I tend to like to get one setup that suits the largest scope of the flight envelope and then work on my skills to get better at the more extreme flight regimes.

With the better balance and CG being back 1 and 3/4" from the stock plane, it does require much less up elevator to keep the nose up at 40 degrees AOA.  I do like to fly high alpha with spoilers deployed, so that also helps.

My elevons are deflected about 1/2 to 3/4" during high alpha.  My spoilerons were initially set at 1/2", the right one stayed that way and using "differential spoilerons", I have my left spoileron deflected to 3/4" to try and help with the tendency of this plane wanting to pull right.  As I have mentioned before, either I have built all 4 of my F18 V3s wrong or it just has a tendency to want to pull right instead of left which is what it should do due to prop wash/prop torque.

I did find that increasing my rudder expo from 15 to 25% did help with my smoothness and as I continue to practice and get my high alpha skills back, I will will consider reducing this back down, but the rudders are nice and responsive with this expo and the throw I have set now.

So now that I have the plane about 95% dialed in for how I like to fly, it is time to do some more "homework" and assess how much I should raise the battery to get the right vertical balance to see how the plane performs without being so "bottom heavy".  Stephan did this excellent video awhile ago that explains how he used these principles that led to the great vertical balance on the NAMC Mig-FA.

More to follow as I get more testing done :)

Cheers,

Scott

RCP F18 V3M Field testing - Day #2

Hi everyone -

Back out at the field again today getting some flights in with my F18 V3M :)

I managed to get 8 more flights in today before being chased away by some rain, but it was a very productive day none the less.  I think I have the CG now dialed in exactly where I want it.

CG/PMI

I moved the battery back 1/2" from yesterday's testing and it just really gave me that locked in and almost perfectly balanced feeling when flying the plane.  So my PMI is now about 9.5", not quite as tight as the NAMC Mig-35, but darn close.  It certainly feels just right for this plane.  

What was interesting today however was as I moved the battery back, the CG balance point moved back considerably from yesterday, either that or perhaps I was assessing it incorrectly, I'll be the first to admit I do make mistakes often :/

Anyway, today, the plane seems to balance perfectly at a point 1 and 3/4" behind the wing break or 1 and 3/4" behind where it is marked on the original RCP plans.

Here are a couple pictures showing where the CG is now located and how the battery is located in the electronics bay.  In this first picture you can see the blue "+" indicating where my plane balances with the battery installed.

In this picture, you can see how far back the battery is compared to my first flight, hard to believe that I used to fly this plane with the battery 9" further forward than this :/  Just for testing sake, I did try it just a bit further (about 1/4") back, but then I could feel the plane tail heavy and harder to handle.

With the battery in this position, there was a significant difference in the arc tests, the plane actually floated a bit over the top of the arc before the nose dropped, which is what I am looking for.  Then when I rolled inverted to cross check it, it only needed about 20% forward pressure on the stick to keep the nose level while upside down.  Even though it would now be "top heavy" while inverted, it was very well behaved during inverted flight.

I know we all set our planes up a lot for how it feels to us, but as soon as I got the battery in this position, I could tell the difference.  As I was flying straight and level, I could just let go of the sticks and it stayed true, smooth and stable and I have no trim required any longer in the pitch axis.

General flight characteristics

General handling and aerobatics are very smooth, yet very precise and the plane is quick and agile, but only goes where you point it, it doesn't over respond to the controls when it is balanced this well.

On launch, it just goes straight forward, I can see how well balanced it is as it starts to fly away and picks up speed.  Then on landing, it just finds it's own natural sink rate, a little up elevator to hold it off at the end and I can touch it down almost like a feather, very impressive and satisfying to fly a plane when balanced properly.

KF adjustment

I am undecided as to whether I am going to play with the KF dimensions any further.  I mentioned at the end of my last test session I thought I saw some "mushiness" returning to it's handling, but perhaps that was from a bit of wind or was "mushiness" of the brain and not the plane! :/  I'll further evaluate it's performance in the wind before considering whether to trim any more off the trailing edge of the KF.  I have actually already removed about 3/8" from the stock KFs as I trimmed 1/4" off before installing them.  Once I am satisfied the KFs are the way I like them, I will measure and report them based on their percentage of total wing chord at the wing root and wing tip.

Slow flight and high alpha

Although there was a light and variable wind today, I kept the plane up a bit higher and assessed it's slow flight and high alpha performance.  I can see there is quite a bit more dialing in that will be required for the optimum high alpha setup which also relies on pretty calm conditions, so that may be a work in progress for awhile.

I could cruise around quite comfortably at about 40% throttle and still make easy turns with elevons and ailerons without danger of tip stalling, however with the plane being so well balanced and a tight PMI, it is far more responsive to the controls than I was used to with my previous F18s, so I had to be careful not to over control as I didn't have a lot of airspeed with which to help me recover.  Fortunately, the 2212/6 2700 Kv motor and 6x3 EMP prop combo gives great pop to get me out of trouble if I do get too slow.

As I mentioned in my previous post, even with the battery all the way to the left of the battery bay, in high alpha the plane wanted to turn right on it's own all the time which defies normal performance where due to prop wash and torque the plane always wants to go left in high alpha.  I did increase the throw on my rudders by 1/4" (1/2" total) which helped, but I need to experiment some more with "differential spoilerons" to help with high alpha stability and handling.  Awhile back I wrote this article that might help you understand what I mean by setting up differential spoilerons for high alpha.  http://migsrus.blogspot.ca/2014/12/differential-spoilerons-for-high-alpha.html

As you can imagine, the plane is much more sensitive to high alpha control inputs as the CG is much further back and the PMI is much shorter than the setup I used to have.  It can hold very scale high alpha, about 40 degrees AOA (angle of attack), but I will have to train myself to be very smooth on the sticks to get the best high alpha performance, but I am up to the challenge.  I've always found the F18 V3 to be one of my favourite planes when I feel the need to try a little high alpha flying and since the F18 does this a lot in airshows, it is nice to try and emulate the scale performance I have watched on many occasions live.

So a bit more testing to be done before I write my final synopsis, but thus far I am very, very pleased with the new life that seems to have been injected into the F18 V3, one of my favourite all time park jets :)

Cheers,

Scott

RCP F18 V3M Field testing - Day #1

Hi everyone -

Had a great day at the field today, managed to get 10 flights completed with my F18 V3M.  It had been a couple weeks since I had flown, so I did a couple "warm up" flights with my NAMC Mig-35 to get my thumbs and brain limber :)

It was a great day for testing as there was little to no wind, maybe 5 kts maximum, so it gave me a chance to get started on the "dialing in" process.  Today I focused primarily on getting the battery positioned just right to find the neutral CG and although I think I still need to tweak it just a bit more, I'm almost there.

I also wanted to work on getting the plane trimmed and determine what my throws should be.  My whole philosophy on how I set up my planes has changed dramatically since I last flew an F18 V3, before this I was using 3D type throws, 50%+ expo, not in tune with the more precise way I like to set up and fly my planes now.

CG/battery position/PMI

Before getting too far into the CG and PMI, I must say there is something very unique with the F18 V3 and how it balances in the roll axis in my experience.  This is the 4th F18 V3 I have built and for some reason, no matter how careful I am with aligning everything during the build and setting up the control surfaces, it always wants to roll right, not left as you would normally expect you would have to compensate for due to torque roll.  As a result, I maxed out my left trim and it still wanted to roll right.  I checked and double checked my alignment of everything, my control surfaces, etc and still had the same problem.  So although I would prefer to fly with my battery dead centre along the centreline of the plane, I had to put it to the far left of the battery bay so that I was not dragging so much trim deflection around.  Not ideal, but I guess I will just have to live with it and hopefully as the dialing in continues it won't have too much impact on how the plane performs.

As mentioned in a previous post, I started off with the plane balancing at a point 1" behind stock or 1" behind where the wing breaks from the LERX.  As a reminder, this was where the battery was located to balance on that point before I left the house.

This gave me a PMI of 12.5".  As I started flying it, it was quite nose heavy.  I began doing several "arc" tests to determine proper balance.  Essentially, I take the plane up in about a 30 degree nose up climb, 60-70% throttle, then chop the power and watch what it does.  One thing I did note with the F18 is that because it slows down much quicker than other planes I have tested using this method, the nose still would drop a little quicker because the momentum bled off quite quickly.  So I would cross check by rolling the plane inverted and seeing how nose heavy it still was when flying upside down.

By the end of the 10 flights, this is where my battery is located and I think it could still go back a bit further, maybe another 1/4" at least, but I will confirm that during the next test session.

My PMI is now 10"!  Wow, big difference and as mentioned, this might be tightened up a bit more still.

Here is where it gets interesting.  I would have thought that moving the battery back 2.5" would have a dramatic effect on where the CG balance point would be.  In fact, it only moved back about 1/8", so my CG is now 1 and 1/8" behind the wing break.  What tells me I am getting close to dialing in to neutral CG however is that if I put my fingers even 1/16" behind or ahead of that point, the plane either pitches up or down significantly, there is very little tolerance.  I found this to be the case as we dialed in the Mig-35 and Mig-FA, so I know I am getting very close to being bang on the neutral CG of this plane, at least in the pitch.

Control surface throws

This shortened PMI has made a significant impact with how this plane is balanced and flies, much more responsive and requiring very little control surface deflection to get it to change direction.  In my opinion to suit the way I like to fly, this is important, less deflection means less drag and turbulence and greater stability and less energy loss as the plane changes direction.

I fly with very little expo, only 15% on each axes, so this gives me not only a better feel for the plane, but small stick inputs translate to more instantaneous control surface movement without the lag that a large amount of expo can cause.  I try to set my planes up with "just enough" throw to allow me to fly scale type manoeuvres with a little extra emergency throw in the pitch in case I need to avoid something quickly, like the ground :/

My current surface deflections are as follows -

• elevons, 1 and 1/4" in one direction, 2 and 1/2" total, measured in both the pitch and roll position;
• ailerons, 1/2" in one direction, 1" total.  I may tweak this up about 10-20%, the long straight wing of the F18 needs a bit of extra help to make the rolls crisp and snappy;
• rudders, 1 and 1/8" in one direction, 2 and 1/4" total.  This is sufficient for good scale stall turns, it might need to be tweaked a bit more as I explore high alpha performance.

KF adjustment

About halfway through the CG determination process, I noticed that the plane started to feel a bit "mushy" and at times was fighting itself in turns.  From my experience with the Mig-35 and Mig-FA, this indicated to me that the trailing edge of the KF was too far back, causing an imbalance with the CG and CP (centre of pressure).  I trimmed about 1/8" off the back of the KF top and bottom and it smoothed this out.  I am thinking that I will probably need to trim just a bit more off as I continue to test, especially if I move the battery back more as during the last flight I was starting to feel that "mushiness" (I know not exactly a scientific term :/) again.  

Overall performance

Ok, enough of the technical stuff, what happened in the air?!  

I must say I am extremely happy with the effect these mods have made on one of my favourite park jets of all time.  This plane just feels tighter, crisper and far more precise than the stock F18s I have built in the past.  It tracks even truer, is more balanced and responds to inputs with just the lightest of touches.  

Nothing of what I have done has done much to make the plane any faster, but it is far more agile and quicker to change direction with less control input and it does so without any hesitation, bobbles or sloppiness, just quick, precise movement.  Although it is still "bottom heavy" because the battery is so far below the wing plate, it still has some self correction qualities, but far less than the stock setup, meaning it is still very stable, but more responsive for someone looking for more intermediate to advanced performance from this tried and tested park jet.  This is something I will also assess and test to see if I can raise the battery up somewhat once I know exactly where it will be located for best balance in the pitch and roll axes.

I still have considerable more testing to do to get the CG really dialed in, KF adjusted just right to how I want the plane to fly and perhaps more adjustment to the throws and to assess it through the slow flight and high alpha flight regimes.  So much more to follow as I can get to the field and keep blasting batteries through this plane :)

One final note concerning the wing reinforcement plan I am testing, as a reminder here is what it looks like.

I did several full throttle hard turns in front of myself and several full power pull outs from dives/loops and saw no flex in the wing, so I am very pleased with how this is working out thus far.  It does add a bit more weight to the plane, but gives me the confidence that my wing is rock solid and strong.

More to come very soon I hope :)

Cheers,

Scott

RCP F18 V3M Ready to fly :)

Hi everyone -

With a couple days of bad weather keeping me indoors, I have been very busy the last two days and finished up my modified RCP F18 V3.

I will eventually do a more detailed walkaround video after I maiden the plane and start the dialing in process.  I have a paint job in mind, but since this is a test bed and I will probably be trimming some bits off the trailing edge of the KF airfoils, I decided to go with just some magic marker on the canopy and "nozzles" and some painter's tape on the wing tips to help with tracking and orientation.  Although very simple, I have found with testing the NAMC Mig-35 and Mig-FA that this is a very effective scheme to help me keep track of the plane in just about any sky condition.

So after all the hacking and slashing, I ended up with these dimensions

• I shortened the plane by 2.1", my plane is 42.25" long, the stock build is 44.35" long.  I am hoping this will make the plane more responsive overall, but especially in the pitch axis as it is now more "compact";
• My AUW with a 2200 3S battery is 599 gr/21.1 oz which is a good weight for this plane.  I didn't change the wing area, so wing loading should still be fine.

With moving the motor 1" forward, I have moved the stock CG back by 1" just as a starting point, here is a picture of what my electronics bay looks like with the battery placed to balance on this new CG.  Obviously I will only find the true CG once I have had a chance to fly and adjust it for balance and KF dimensions.  In this picture if you look on the right hand side, the black "+" indicates the new CG I will start with.  I made several little plus signs aft of that in 1/4" increments to give me an idea of how much I am moving it as I dial in the plane.  I am assuming it will only be going back as from my previous V3 experience, the plane balanced nose heavy on stock CG.

I placed my rudder servos a bit farther back that I normally would like, but since I will more than likely be trimming some foam off the back of the KF airfoils as I dial in the plane, I figured it would be easier with them out of the way.  I still need to trim off the extra pushrod that is sticking so far forward.

When I measure from the front of the battery to the tip of the bullet nut on the motor mount which in previous testing I referred to as the PMI (polar moment of inertia), I get 12.5" which is a huge improvement in tightening this up and hopefully making the plane even more responsive, precise and maneuverable.  With the old setup, my battery was all the way up against the bulkhead which gave me a stock built PMI of 18".  Big difference.

Here is a side shot, it does look like a much different plane than the stock, I can notice the 2" less in length.  I shortened the nose by about 5/8", but I think it still looks pretty good, not as "pointy", but that is a purely aesthetic thing for my preference.  

If using the length of the plane as a percentage, with the new length and motor location, the motor is located at 61% from the nose which is almost identical to where it is on the NAMC Mig-35.  Again, I'm hoping getting the CG, CT and CM closer together I will be getting better balance and overall performance.  

Above and below you can see that I mounted my servos and ran my pushrods externally as I like to do on all my planes, I find it makes for much easier, more secure installation and adjustment and keeps the prop wash area clean of as few obstructions as possible.

So I am very excited not only to have an F18 in my "hangar" again, but to start some testing and comparison side by side with the NAMC Mig-35 to see if some of the principles built into the Mig-35 carry over to the F18 which is a very different airframe style with a more straight wing.  Let the field testing begin!

Cheers,

Scott

RCP F18 V3M Update #2

Hi everyone -

I have been plugging away slowly on my modified RCP F18V3 and have reached the stage where I am ready for the main assembly.  In this first picture I wanted to point out a different wing reinforcement setup I am going to experiment with.  On our NAMC Mig-35 and Mig-FA, we have had great success with a "Pi" shaped setup, named as such because it resembles the mathematical symbol "Pi".  On the F18 because of the different wing shape and the fact that I moved the motor mount forward by 1", I was not going to be able to run as long a main wing spar as if I built stock.  So I am going to experiment with this "A" shaped plan.  The main spar is 4mm carbon rod, very stiff, a piece about 16.5" long.  The two pieces of carbon fibre that angle along the leading edge of the wing out to the wing tip are 3mm carbon tube, each piece 12.5" long.  I didn't come up with these lengths using any kind of scientific formula, I just had them laying around and they seemed to fit my plan just fine.  Already I can tell it will be a very stiff, strong wing, even stronger once I install the KF4 airfoils.

It might be hard to see the line in the picture, so I put a pen to point where the line is so I could ensure that the inside tip of the 3mm carbon tube pieces will get locked under the nacelles/intakes when those are glued on.  As we learned from the NAMC Mig-35/FA, this really helps lock in the carbon fibre tube to make as solid a wing reinforcement as possible.

I attached the back plate/horizontal stab/elevon piece back on to the main wing plate and I have also installed my elevon control horns.  I find it so much easier to do this when it is still a flat piece of foam to work with.  On this wing plate, I have also sanded the trailing edge of the wing/aileron so that it is symmetrically tapered to allow for smooth airflow.  I also did the same to the leading edge of the horizontal stab/elevon and the trailing edge of the elevon, the leading and trailing edges of the prop slot, all to allow for smoothest airflow possible.

I have also installed a short piece of 3mm carbon fibre tube in each vertical stab, these pieces are 5.5" long, again nothing scientific, just what I had laying around.  The side shown of the vert stab/rudder assembly will actually be on the outside of the plane with the smooth side of the hinge on the inside.  This hopefully keeps the prop wash area between the stabs/rudders as smooth as possible by having the bevelled part of the hinge on the outside.  You can see a blue line I drew so that when the stab/rudder is installed on the plane, a portion of the carbon tube will extend below the wing plate to lock it in nice and tight and hopefully keep the vertical stabs from fluttering in the wind and high alpha.

I also assembled the fuselage and installed the canopy.  I tapered the canopy front and back by narrowing the centre piece by 1/4" on both sides giving a more oval shape to not only make it look good, but hopefully more sleek through the air.  The front part of the fuselage has been shaved down with a knife to remove the square edges of the score lines, then filled with a very lightweight finishing spackle, then that has all been sanded as smooth and sleek as I can get it to present the least amount of drag.

Next up is to put the plane together short of installing the vert stabs/rudders, I will do that last after final sanding as I find it easier to handle the plane without the vert stabs/rudders in the way when I am constantly flipping the plane on it's back to adjust elevon and aileron control setups.

More to follow very soon, I'm getting more excited at each stage of the build to see how this modified F18 is going to turn out and perform :)

Cheers,

Scott

RCP F18 V3M - First update

Hi everyone -

Since my last post on my modified RCP F18 V3, I have been busy with the calculator, ruler, pencil and quite often the eraser :/ drawing the mods I discussed in the first post.  All the parts are now cut out and the weight of raw foam weighs 153 gr/5.4 oz (this includes the four pieces needed to make the KF4 airfoils).

I tried to remember to take some pictures as I went along to show the modifications I have made thus far, but when I am all done, I will do a "walk around" video that will describe in detail all the changes I made from stock to permit the testing I want to do.  Here are a few pictures that I did remember to take.  The picture below shows an overview of what I did to the wing plate thus far to accommodate moving the motor further forward and to adapt to changes I made to the elevons and back plate. To attempt to get the right scale wingspan to length ratio, I extended the wing span by 1/4" on each end.

 This picture below shows in a bit more detail what I did to move the motor mount forward.  You will also notice I moved the back part of the centre gap further forward by 1".  This area accepts the back part of the fuselage and I needed to maintain some foam between the motor mount and this area for strength and carbon rod installation.  I prefer a straight trailing edge to my prop slots, so I just drew back to where the original trailing edge would be, this will give the prop plenty of room to "breathe".

This picture below hopefully shows how I trimmed about 1/4" off the trailing edge of the wing since I am moving the elevons forward a bit to try and achieve scale proportions between wingspan and overall length.  We found in testing on many different platforms (RCP Mig-29 V4, NAMC Mig-35/Mig-FA) that an aileron span of about 60% of the wing span on that side works quite well giving the best control for basic flying and or when we wanted to play with spoilers/flaps for high alpha or other advanced aerobatics.  Since the F18 wing has a fairly deep chord, I left the chord of the aileron stock.

In order to allow me to play around with the elevon sizing and to be able to keep a fixed horizontal stabilizer similar to several other park jets, I cut the back plate part of the plans away from the wing before cutting as I couldn't orient the entire big piece on my sheet of Depron with the elevons/horizontal stabs attached.  Additionally, this will make it much easier to sand the elevons, trailing edge of the wing and ailerons before assembling the pieces.  I will discuss this further in follow on posts.  When the time comes, I will reattach the back plate with epoxy or Foam Cure, it will be a very strong joint, in my experience the foam will probably break before the glue joint does.

Hopefully in this picture, you can see where I will be cutting the hinge line for the elevons.  It shows up a bit with a thin blue line from marking it with a pen.  The elevons are about 88% of stock, I printed the portion of the tiled plans that includes the elevon at 88% and then made some modifications to the "nozzle" location and hinge line so that it would all fit together.  Hopefully it shows up in the second picture under this paragraph.

To accommodate moving the motor forward, I had to trim the fuselage somewhat, on the end where the ruler is I trimmed 1" off and moved the tabs as shown by where the pen is 1" forward so that they would fit into their new slot on the wing plate.  I also shortened the nose by about 1/2 - 5/8", I just kind of roughly drew on the paper before cutting things out, so hopefully the nose will still look OK.  I can always shape and sand it to how I want it to look anyway which is part of my build plan.

On the nacelles, I trimmed 1" off the back where the blue pen is pointing to ensure no interference with the prop with the new motor location.  I have always trimmed the fin off the back of the side piece of the nacelle, mostly for looks and weight reduction as you can see where the orange highlighter pen is pointing.  This will put the back part of the side piece about even with the front of the elevon hinge line. Also, since I know from hard earned experience how weight sensitive the F18 V3 can be, any weight reduction I can make without sacrificing structural strength is OK with me.

Here are the KF airfoils cut out.  I have found with my previous modified F18 and with many other planes that extending the top airfoil all the way forward to cover the LERX helps the stability and smoothness of the plane's handling.  It does add a bit more weight, but is worth it in the long run.

I have my components picked out, the receiver has been bound, all the servos have been checked and are ready to go.  I will be using a Deal Extreme 2212/6 2700 Kv motor and 6x3 EMP prop with a Turnigy Plush 40A ESC.  The servos are 9 gram nylon gear servos from RC Timer.  I will most likely be using a 2200 Mah 3S battery.  I am hoping to get my finished weight (with battery) around the 21.5 oz range as I have found that is about the best wing loading for my preference, gives good stability and wind penetration without over stressing the wing.  All the components I am using are listed on the NAMC Recommended Parts List.

I should mention that my build will be of a "composite" nature WRT types of foam used.  The wing plate, back plate, vertical stabs/rudders, all other control surfaces, nacelles and internal structure will be built with 6mm Depron as I prefer the added strength and stiffness in these areas.  The fuselage and canopy will be built with Fli-Value XPS foam (similar to MPF or model plane foam) as it is less expensive than Depron and easier to bend and sand.  The KF airfoils will be made from paperless dollar store foam.

Well, that is probably enough for now, next steps are to install the carbon reinforcement, bevel and attach all the control surfaces, do some sanding of certain areas of the wing plate (always much easier for me to do before assembling the whole plane).  More to follow in the days to come :).

Cheers,

Scott