Battery placement experiment for best balance

Hi everyone -

After watching Dave Power's "3 Axis Balance: Battery-Booster-Seat" video the other day, I realized I still needed to work on getting my plane even more neutrally balanced than I had already been working on.  Here is Dave's video.

I'm not so worried about getting my planes to hover, but eventually I will experiment with aligning my battery with the wing plate as Stephan has already discussed awhile back in one of his posts.

If you have been following the theme of many of my recent posts, I am striving to set my planes up to achieve neutral balance and thus far have done so by concentrating only on the pitch axis, I have still been stuck in my old philosophy with respect to the roll axis.

What I mean by this is that probably 90% of the park jets I have ever flown, I have put the battery all the way to the right side of the electronics bay to help counter torque roll in order to have zero trim in the roll if possible.  Here is a picture of what I mean.  This is because I was still stuck in the mentality that I have to balance my plane so that I have zero trim and not balance it first and then trim as required.  It makes a big difference in how my planes fly as I shed this old way of thinking.

As I have been dialing in my planes using neutral CG in the pitch along with other precision setup techniques learned from Dave Scott's Airplane and Radio Setup manual (have my own copy now, so life is even better... :)), I have noticed that the plane is much more responsive in all three axes.  When I say responsive, I don't mean twitchy, but as my planes become more balanced and responsive, they are also affected more by other factors that can adversely affect this optimal balance such as the battery being placed too far right or left of center line in the roll axis.

So here is what has been happening thus far when flying with my battery all the way to the right.

The plane has much greater tendency to want to tip stall to the right when slow and too much control input is applied.  Also, I noticed in loops that it often would want to spill out to the right as speed bled off, so my loops were not quite as smooth and uniform as I was liking.  Rolls were also not balanced in both directions.  I know torque roll can impact roll behavior, but with the battery so far to the right, my right hand rolls were tighter and smoother than my left hand rolls because the plane was having to lift that unbalanced weight as I tried to roll left.  Because I was still stuck in my old "zero trim is good" mentality, I just worked harder to fly my planes and compensated for these shortcomings.

So just a couple numbers first to put things in perspective.  I like to fly with a 2200 3S battery in my planes as shown in the picture above about 99% of the time, I just like the weight and wing loading it brings to my planes and helps with wind stability and penetration.  Since most of my planes are in the 20-22 oz range and the battery weighs 6.9 oz, it makes up about 33% or 1/3rd of my plane's total weight which is pretty significant.  So by having it so far to one side of roll center line, it would be like going for a hike and packing all your heavy stuff to one side of your back pack, you would feel very imbalanced and so does the plane.

So the last couple times at the field, I have been placing my battery as close to dead center as possible in relation to the center line like in the picture below.

Before I started doing this, I zeroed all my trims to ensure that all control surfaces were still dead center.  I did find one aileron and one rudder not quite centered, so after centering them, I got on with the testing.  

Right away, my plane felt more balanced, easier to fly and the handling smoother, regardless of direction.  The tip stalling to the right was pretty much eliminated as was pulling to the right in loops and my roll balance was almost completely equal both left and right.

I did have to put a couple clicks of right trim in the roll to help counter torque roll and I am good with that.  I am changing my philosophy that trim is my friend and not my enemy like I always thought it was.  Of course this has to be applied with reason I think, if I needed to carry half the trim I have available to me around, then there might be something not right with my plane.  This of course is always a bit of a crap shoot with the scratch built planes I fly, not every one of them is going to be perfectly straight and true and each plane is subtly different.

So I guess next up might be to experiment with the "Battery Booster Seat" and see how that affects the balance of my planes.  Stay tuned... :)

Cheers,

Scott

A warm welcome to our newest NAMC member

Hi everyone -

Stephan and I would like to extend a warm welcome to the newest member of the NAMC partnership, Dave Messina (aka Backmarker).

Dave has been contributing excellent comments and insight to the blog for quite awhile now and it became obvious to Stephan and I that Dave was a perfect fit to what we are trying to achieve here.  It is with great pleasure that we have added Dave as partner and author to the blog so that he can expand beyond just leaving comments to posts that Stephan and I have made.

I won't steal Dave's thunder in introducing himself and presenting his RC resume, but suffice it to say that he brings not only a vast amount of RC knowledge with him, but significant life experience as well and this blog will be a much better place with Dave fully involved.

Welcome Dave!

Cheers,

Scott

Puto, Consilium, Test et Convalidandum; Think, Design, Test, and Validate

Two Finger Convert & Resolving Resolution, Now I Don't Need a New Transmitter

Lousy day at the golf course, I need new clubs.

Double faulted match point, I need a new racquet.

Mid life crisis, I want a Porsche (better choice than trading your late model in for a new edition blonde).

Crashed my plane and there's three wasted hours on the web checking out the latest greatest electronic upgrades for my setup.

TVAW, Twerking, Thrusting Vector Stalls, what's wrong with this plane!

I am going to save a lot of money and have a lot more fun at the flying field after today's experience.  Just a couple of posts back, Scott did an awesome review of what we have learned from David Scott's flight manual, Airplane & Radio Setup.  Buy the book now, I promise it will be the best money you ever spent on RC.  I didn't discover this book, Dave Messina recommend it in a reply to one of my blogs.  

Finally the sky cleared and I was able to head to the field.  The wind was gusting 10-15 but I was willing to crash to get some stick time.  For the first time in a long time, not only did I not crash testing the flight envelope of our developmental "ultimate flying machine",  I didn't even have a close call. No TVAW twerking (thrust vectoring ass wagging) or EPPE (elevon polar pitch effect).  

What made the difference?  I dialed my plane into a precise flying machine and not a 3D park jet. Don't get me wrong, I like to fly 3D with my Edge, but that setup doesn't belong on the "ultimate flying machine."

I went to the field with specific goals, another recommendation from David Scott.  I thought it was going to be a boring day; launch, land, change radio and/or control rod linkage holes, repeat, repeat, crash, repeat.  With every adjustment, the stick feel and flight performance was not incremental but rather monumental.  I could not believe the difference, it was like flying a brand new plane.  Scott and I truly had developed the "ultimate flying machine."  I know realize all the developmental negative flight characteristics were setup related and not design issues.  

So how did I approach my day?  I looked individually at pitch, roll and yaw.  At maximum stick throw, I got the maximum, and no more, desired affect.  I picked the roll rate slightly faster than scale but not a rifled bullet.  For pitch, I used to set full up to be able to do a Cobra.  From playing with the throws, I now know that what I had been using was too much, they were 3D settings on a precise airplane.  At that much pitch, it was to easy to TVAW, twerk, and thrust vector stall.  The final setting for pitch was where the plane would do a slow motion flip/tumble  loop at full throttle. For yaw, I wanted nice lazy rudder stall turns at full throw.  I then confirmed the throws at 50% throttle which is where I spend most of time flying.

I first adjusted the travel and expo rates to get the desired throw.  After looking at the numbers,  I then moved the control rod down the control arm on the servo to maximize servo resolution, i.e. take advantage of the full range of motion of the servo.  I adjusted my travel and expo accordingly trying to hit the sweet  spot of 90% each.  On my present build I have switched to FliteTest control horns that have 3 possible positions instead of just one on Grayson control horns and RCP plans (see Dave Backmarker's replies to Scott's posting on precise flying.  This will allow even more fine tuning. 

Not only was my plane more precise but the near crashes, TVAW, twerking and thrust vectoring stalls were no longer part of my routine flight experience!  I was in Mig heaven.  

One other very interesting thing occurred that also greatly improved the handling.  I keep a spreadsheet of my setups and throws.  My elevon throw was reduced from 2.5 to 1.5 inches.  But the differential elevon plus aileron max throw was reduced from 4 to 1.75 inches ( i.e. at max elevator to max aileron the additional throw was reduced from 2.25 to 0.25 inches!).  Clearly this added a great deal to better flight performance.  This reduction occurred from improving resolution.  I'm sure I could have programmed the radio to have less aileron input to the elevons, but that is way beyond my understanding of the Spektrum Dx8.  I'm still waiting the Dx8 For Dummies book.

So what I thought was going to be a boring day of flight testing, turned out to be one the best days ever at the field.  Not because I didn't crash, but I had take my late 70's American highway cruiser and turned into Nurburgring asphalt eating "ultimate flying machine."  Combine the new setup with our new Mig, and it truly is deserved of the title.

One more thing, I have changed to Dave Scott's two finger technique and thrown away the neck strap.  A additional bonus to an amazing day.

To finish up, here is picture of one of my prototypes that I painted so hopefully someone will buy it.  Looking through the paint at Hobby Lobby I saw some super glitter paint.  I top coated the canopy with it see if it looks more like glass up in the sky.  Next time, I'll do the glitter on top of silver.  The paint scheme is standard four color camouflage pattern from http://www.mars.slupsk.pl/fort/mig/default.htm

Stephan

Teaching myself the "two finger" method of RC flying

Hi everyone -

As I mentioned in my previous post and showed briefly in my flying video, I have been teaching myself to fly with "two fingers", well I suppose finger and thumb really to try to become a more precise RC pilot.

Here is a video I shot describing the process I went through to get to where I am now with respect to how I handle my transmitter.  It took me about a dozen flights to get my final hand position figured out, and now it works really well.

Since it was kind of like learning to fly all over again, I kept my plane up higher than normal to give myself more recovery altitude and I certainly needed it a few times until I got the hang of it... :/

This technique of flying is adopted from the Dave Scott's Airplane and Radio Setup manual available from http://www.rcflightschool.com/

If you are looking for a way to have a more light touch on your sticks, it is definitely worth giving a try, I notice that my grip on the transmitter feels much lighter and more balanced as does my touch on the sticks.  For me it is a much more precise and relaxed way to fly my planes.

Cheers,

Scott

Mig-PAK FA T-50 Prototype Evolution

1/15/2015 Update

Dave Backmaker, a regular contributor to our blog, had some great comments he posted on my blog about printing on Depron.  I "painted" my plane and took it to the print shop yesterday.  The "mainframe" will be double side printed on Depron.  The fuselage will printed on MPF.  I like to use MPF on the fuselage because it is easier to mold and sand than Depron. The KFs will be printed on Dollar Store Foam.  I leave town for a week so there won't be an update on the final print until I get back. The guys at the print shop are as excited as I am.  Here are jpgs of the PDFs:

Earlier I posted a video on my latest prototype build.  After further development of the design, I thought I'd post an update.

I definitely need to figure out a better name for this "hybrid" plane.  Perhaps simply the Mig-FA.  It's kind of like putting a small block Chevy in a  channeled & chopped custom 32 Ford roadster.  More on the design after some background.

The Russian military PAK-FA (Prospective Airborne Complex of Frontline Aviation) project was a fifth generation fighter program focusing on stealth technology.  In 2000, Mikoyan-and-Gurevich Design Bureau designed a stealth plane, the MiG 1.44/1.42, that was an evolution of the Mig-37.  The Mig1.44/1.42 flew in 2000 but never made it to production:

Sukhoi went on to design and build the T-50:

In the search for "stealthiness" there are many aerodynamic comprises.  Stealth design leaves little airflow over the vertical stabilizers as the horizontal stabilizer is coupled to the wing trailing edge.  With that comes bad slow speed tendencies at high angles of attack as there is no gap between the wing and horizontal stabilizer for air "leak" through and onto the vertical stabilizers.  Additionally, the vertical stabilizers are angled therefore the rudders cause pitch in addition to yaw further complicating surface control input commands.   I wanted a stealth plane as I really like the look,  so I built the RCP F-22v3 and quickly learned why as stealth plane is such a handful to fly. Real planes are loaded with computer assisted flight controls.   At slow speeds, the F-22 would violently yaw and then pitch into the ground.  As long as I was flying 50% throttle and above it was blast.

So after 8 months of developing the ultimate Mig "chassis" (stay tuned, more to come), I decided to do some old fashioned hot rodding and make a stealth plane.  I started with the fit, finish and design of Scott's and mine ultimate Mig and went back to the computer and started drawing.  Borrowing a proven Ford chassis, I added a Chevy carriage.   Using diagrams, photos, and plans from the internet on the T-50, I redrew a new stealth plane around our new ultimate Mig chassis.

Technical drawing that was the inspiration for prototype #1:

Protoype #1:

The T50 is 65 ft long divided by wingspan of 45.8 ft  = 1.41. My prototype is 38" long and 27” wide = 1.407.

The fuselage in the picture above was a left over design experiment the ultimate Mig project.  The plane flew amazingly well and had a great profile in the sky so I moved forward with the project.  It did not have the undesirable characteristics of the F-22, even with its coupled tail and "hidden" vertical stabilizers except for at near stall speeds.  I spent another 30 hours or so moving pixels in my drawing program (iDraw vector drawing program for Mac) and building Dollar Store foam board fuselages to try and improve the look.  

I started with this side profile photo to improve the look and made several builds:

Forming and shaping the nose has always been difficult, so I added a forward piece to stringer:

Final fuselage in profile and same with a drawing:

From a design standpoint the radar extension on the tail is polarizing.  This area of the elevons is very important in parkjets for thrust vectoring, especially in high alpha.  Prototype #1 had excellent thrust vectoring control, I think it was due to a combination of right amount of square area and the centrally located radar extensions which minimized the roll lever arm.  For prototype #2, I also drew elevons without the radar extension, but I maintained the same square area in the thrust vectoring zone. For the final plans, this will be an option.  

Tailplane with thrust vectoring square area measurements:

Elevon options with and without radar extension:

Schematic of plane without fuselage:

Next phase of the project is "painting" the plane in the drawing program and  Iwill print it directly onto Depron as with these plans:

Hopefully the weather will clear and it get in some more test flights on prototype 2.  My case of Depron came in today.  Quick aside on my builds, I use MPF for the canopy and fuselage as it sands better than Depron.  The rest of the build is Depron.  Another Ford & Chevy hybrid?

I think I'll call this plane simply the Mig-FA.

Stephan

Dialing in plane and pilot for precise RC flying

Hi everyone -

As I wrote in my last post http://migsrus.blogspot.ca/2015/01/scotts-rc-goals-for-2015.html , I am in the process of changing how I set up my planes, my transmitter and myself to become a more precise and honest flying RC pilot.  I also forgot to add that I want to learn to be more relaxed and skilled when flying inverted, it is kind of my "RC kryptonite" right now, but with the process I am going through, I see that being a much easier thing to learn and hopefully master.

I shot a video at the field yesterday to hopefully better demonstrate some of what I am talking about.

Hopefully the video touches on most of the process that I have been learning with help from Stephan and his inputs from Dave Scott's Airplane & Radio Setup manual http://www.rcflightschool.com/Setup_Manual.asp , but I wanted to touch on a few highlights that stick out in my mind from going through this process.  I have my own copy of this manual on the way in the mail and will share more with the blog once I receive it.

The foundation of this all rests on setting up and flying a more balanced plane, so I would strongly recommend doing this first as it makes the plane much more balanced and predictable in what it is going to do from my experience.  Even with 3D style throws and tons of expo, my planes have been flying immensely better when properly balanced.  In my video and the video Stephan shot, we demonstrate the arc method of determining whether your plane is properly balanced.

There is no "class answer" on exactly what your arc should look like, you have to use some judgement there.  What I would say to look for from my experience is if the nose drops almost right away after you cut the power, the plane is more than likely nose heavy.  If the back end drops and the plane kind of "mushes" (sorry not the most scientific of terms) it's way through the arc, it is probably tail heavy.  

The plane should continue to climb after chopping the power and as speed bleeds off, transition across the top in a smooth, uniform arc before the nose starts to drop.  

Like any dialing in process, it needs to be done in steps, don't move the battery on your Mig29 back by 2" right away just because I did, take it in smaller increments maybe 1/4" at a time until you find the right balance.  You can do a couple arc tests, land, move the battery, try again, etc, so you can get several arc tests done in one battery to help speed up the process.

Once you get the plane balanced, don't be scared if you have to put in some trim to keep it level for certain parts of the flight envelope, sometimes the plane might want to zoom or descend on you at full throttle, so a few clicks of trim to help that out is not a bad thing.  This was one of the hardest ruts for me to break out of.  Now obviously if you are using half your down trim and are dragging around 1/4" of deflection in your elevators, the plane might not be balanced properly or the elevators were not dead center at zero trim, so you might want to recheck the balance point and the control surfaces.

I mention this at the end of the video and will mention it again as I learned this while going along and I think it is very important to the process.  It is important to ensure that your control surfaces are dead center when you have zero trim.  Over time especially with scratch built park jets, I have found as hinges and linkages get broken in, what was once center with zero trim can shift, causing me to have to trim to compensate for that as well.  So I found it very important to be working from a point of dead center control surfaces as I dialed in my plane, my transmitter and myself to become a more precise pilot, otherwise I was battling against something which didn't need to be there.

What I found worked well for me once my plane was properly balanced was to then train myself to use the two finger method of stick control before playing with my servos and expo.  I now have about 50 flights using this method and will never go back to "thumbs only".  In honesty it took me probably about a dozen flights to fully get comfortable with my new hand position and control and it wasn't without a few mistakes... :/  So while learning this method, I kept my plane up a little higher than normal to give me recovery altitude if I messed something up.  

Then the next step was to start dialing down my expo.  As I have mentioned before, I was in the rut of at least 50% expo on everything as a way of smoothing out my plane not being balanced and essentially what were 3D setups in my radio and with my servos and linkages.  So again, baby steps here, dropping no more than 5-10% at a time, get used to that, then drop again until I got dialed down to 20% expo on the pitch and roll and about 35% on the rudder.  I am still working on the rudder setup, but with the planes Stephan and I have modded and fly, we like having large rudders to help compensate for prop wash in high alpha and other rudder dominant moves, so this may be an area of compromise.

Then the last step I did which I show in the video was to move my linkages as close as possible to the servo to give smoothest response.  Even then with 100% throws, this reduced the travel of my control surfaces, but I am actually very happy with how the plane flew.  As I mention in the video, in future builds I will use different control horns on my rudders and elevons to give me more flexibility in being able to adjust my control surface deflections mechanically.  Awhile back, Stephan was kind enough to send me some control horns from Flitetest http://store.flitetest.com/control-horn-20-pieces/  One of their control horns is on the right compared to a Grayson Hobby control horn which I have been using.

I have at least another 1/8" of control horn to work with which should give me lots of flexibility in getting the control surface travel I want.  Plus, they are much cheaper, $5 for 20 compared to $2.99 for 4.  

As soon as I moved my linkages closer to the servo, I noticed how much smoother the surfaces were moving.  When I had the linkage at the end of the servo arm, the action could be very "jerky".  Of course I am using inexpensive nylon gear servos, but helping the servo out in it's job has helped out the precision I feel and see in how my plane flies.

So although that was the last piece of the puzzle, there is still much work to be done to master the whole process and convert my fleet over, but it has been well worth it.

I found that by following the steps that I did it was actually a very smooth transition, much less difficult than I originally expected.

So again, I'm not trying to be an evangelist here or anything, but if you are looking to push your plane and yourself to a whole new level, these techniques might be worth a try.  If nothing else, next time you fly, try the arc test with your plane and see how it responds.  As I mentioned before, if a person was to try nothing else other than to ensure their plane is balanced on neutral CG, they will immediately notice a difference in the balance, predictability and improved handling of their plane, at least that is what I have learned.

Cheers,

Scott

Bob Smith Industries Foam-Cure Review, Stop Wasting $$$$$ on Foam-Tac

 Foam-Tac is great stuff and I've been using it for the last couple of years on all my builds.  I use epoxy on the fuselage internal pieces and motor mount and supports,  3M 777 for KFs, Alene's glues for glassing, spot or two of hot glue, and Foam Tac everywhere else.  There are two problems with Foam-Tac, number one is that it is expensive, and number two is that it remains too elastic when cured.

Because of its final elasticity, it does not sand well and beads.  It also sticks to painters tape and is easy to pull out like caulk when removing the tape.  Over the years I've learned to work with these downsides.  I used Alene's glues for glassing because of tremendous cost savings.  As much glassing as I do, I could buy a BNF  plane with the money I'd spend on Foam-Tac.  The downside of Alene's glues is that they are water soluble and this makes painting difficult with water based acrylics.  There had to be something better out there.

A couple of weeks ago, I placed a big order to Hobby King.  As always,  I looked for things I might need but didn't know I needed them until I saw them.  Worst than going to Costco, you always buy more stuff than you intended.  I came across Bob Smith Industries Foam-Cure and every hobbyist has their epoxies and CAs at their bench.  If they decided to make a foam glue, you know they would get it right.  Foam-Tac is good, but it is a modified glue for making and mending clothes!

So on my current build I used Foam-Cure as a trial where I've had the biggest problems with Foam-Tac.  I like to fill the fuselage nose gaps with foam strips and sand it smooth.  These are parkjets, smooth equals less drag, more speed, and less downstream turbulence.   Sanding Foam-Tac is like sanding the gummy residue left by a sticker and Foam-Cure is like sanding Bondo. Bonus, the fuselage nose cone built with Foam-Cure feels much more solid than the one with Foam-Tac.  Score, it dries faster!  The picture doesn't do justice to the difference in the sand-ability of the two products (Foam-Cure on the left):

Foam-Cure

Foam-Tac

Check out the price difference:
Foam-Cure from Hobby King $4.03 for 4 oz = $1/oz  Same price Alene's
Foam-Tac from FRC Foamies $9.99 for 2 oz = $5/oz

Foam-Tac cost 5x Foam-Cure!!!!! For that price difference it should build the plane as well as hold it together!!

Stephan