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Modification to FT Flyer for THE BEEF

Hi all,

Newbie to R/C flying and Flitetest here! I'd like to show y'all my FT Flyer build that I just finished last night which includes a simple but hopefully worthy modification.

Quick backstory, last week I built my first foamie (a FT Mustang) from the speed-build kit. It went really well and was alot of fun! I took it out for her maiden flight and crashed her twice before I realized that my aileron channel was reversed! DOH! I have the HK T6a v2 radio, so I had to order the connector cable in order to reverse that channel. I'm grounded for a week.

In the meanwhile, I decided I would scratch build an FT Flyer from the plans. This plane has no ailerons, so my controller would not be a problem! Also since the FT Flyer is a beginner plane I can use it to get better at flying before I ruin my nifty Mustang. My only power pod is the "C" pack from Flitetest, and I read on the forums that the Flyer isn't big enough to carry the BEEF. I figured a modification to the wing size had to be made to improve the flight characteristics with the additional weight and power.

I did some weight calcs and figured out that the FT flyer with the BEEF is ~60% heavier than the Flyer with the recommended electronics. To generate the additional lift (at the same speed and AoA) I had to increase the area of the wings. I did this by increasing the wingspan, which I figured was the simplest way to increase the lift without changing the longitudinal center of lift of the wings (much, anyway). The span of one wing of the FT flyer is 13.0 inches, and I increased this dimension to the full width of a DTFB (20"). I kept the same tip chord as the original plan, therefore increasing the wing area by 54%. The increase in my lift-curve slope due to the increased aspect ratio will hopefully take me up over the 60% increase in required lift. The only other modification was moving the tail aft slightly, about 1", which should improve the control authority a little.

The result came out pretty good and I'm proud of my first scratch build from plans! I do realize that I've increased the stress in the wing-fuselage joint significantly with this mod, so no high G maneuvers! Anyway, if I fold the wings I'll just figure out a way to reinforce this area!

Enjoy the pics!

IMG_20150902_064852.jpg IMG_20150902_064822.jpg IMG_20150902_064914.jpg
Make sure that glue joint is solid! I've folded some FT Flyers with hot motors before!
It should work fine, and if you end up ever wanting to build another one, I used to fly an FT flyer with a "Beef" sized motor, it would fly, it was just faster than most FT Flyers.

If the wings end up holding up well, try some loops, I can even do outside loops and rolls with a fast FT Flyer.
The FT flyer doesn't generate lift, so increasing the wing area is likely just a recipe for folding the wings at the glue joint since you will see an enormous increase in drag.

In its stock setup I've had a park 400 swinging a 10.5" prop and powered by a 3s 2200mah lipo on a FT flyer with nothing but fun results. I can't imagine that setup is different enough from the beef for you to have contrary results from mine.
Thanks for the tips guys!
I'm thinking about adding some foam to the top of the wing near the glue joint to reinforce that area.

Strada, I'm curious about your comment that "The FT flyer doesn't generate lift". Perhaps we are different on our definition of lift, I consider "lift" to be the force generated by the wing perpendicular to the oncoming flow. Therefore for straight-and-level flight, this would be a vertical force, which must be equal and opposite to the gravitational force acting on the aircraft (minus the vertical force generated by the angle of the propeller thrust).
I think he means there is no lift because there is no airfoil. The FT Flyer has to hold some angle of attack to maintain level flight.

I use a carbon rod to brace the wings but bbq skewer should work as well.
Phenom, thanks for the tip with the BBQ skewers! Do you stick the rod into the foam or do you glue it down on top of the wing?

I looked up the subject of flat plates in my copy of Hoerner's "Fluid Dynamic Lift" I have at work. The subject appears on page 21-1. Hoerner writes:
"Lift can be developed on bodies with blunt shapes that have no resemblance to wings. In this case the lift on the bodies is defined as that force acting normal to the direction of relative motion. A flat plate produces lift like an airfoil or wing when at small angles of attack. Long before reaching AoA=90 the flow is completely separated, however. -- Splitting up the normal force in drag and lateral, or lift, components, CL=CN * cos(AoA) is obtained."
The ft flyer wing is not capable of generating lift due to a lack of an airfoil. It can however acheive "lift" through thrust and drag. Adding weight (larger power plant) and increacing the surface area of the wing dramatically increases drag which will put a tremendous strain on the already under reinforced wing.

If you leave it the way it is (stock but larger surface area), you risk folding the bird in half.
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wouldn't a flattened KF ft flyer with ailerons be basically the FT Delta with a tail attached?

I'd wonder what the slow fly characteristics are in such a setup. To me, the whole point of the ft flyer is how it slow flies.
wouldn't a flattened KF ft flyer with ailerons be basically the FT Delta with a tail attached?

I'd wonder what the slow fly characteristics are in such a setup. To me, the whole point of the ft flyer is how it slow flies.
Nope. the Delta has elevons, the FT Flyer in that setup would have ailerons, elevator and rudder. Very different flight characteristics.

Yeah, the slow gentle flight characeristics are for the most part gone at that point... but it makes for a heluva streamer combat plane!
Cellsafe: That was my goal by increasing the wing area by about the same percentage as the extra weight. You said it: one thing people like alot about the FT Flyer is how slow it flies.

I estimated my flyer w/ beef to be 60% heavier than the standard flyer. If I wanted to go the same speed as the standard flyer I would need 60% more lift from the wings & engine combined. The wings will generate more lift if the angle of attack is increased, until they stall of course. I wanted to be able to carry the additional weight without a significantly higher angle of attack from the original flyer, so I decided to increase the wing area.

Read on for my nerdy thoughts on the aerodynamics:

For a given wing geometry at a given angle of attack, the lift and drag coefficients will be constant.

CL= Lift/(0.5*density.of.air*Speed^2*Area)
CD= Drag/(0.5*density.of.air*Speed^2*Area)

If the CL and CD are constant, than we can see how a 60% increase in area results in a 60% increase in lift and drag (for the same density and air speed).

However, I didn't scale the FT flyer wings, but instead I stretched out their span, increasing their aspect ratio. A higher aspect ratio wing will have a higher lift coefficient than a similar wing of lower aspect ratio at the same angle of attack. The difference in lift coefficients between similar wings of different aspect ratios can be estimated by the formula:

CL=0.11*AoA*(AR/(2+AR)), where AoA is in degrees and AR is aspect ratio.

Using this equation I estimate my wings will have a 15% higher lift coefficient at the same angle of attack compared to the standard flyer wings due to their higher aspect ratio. Due to the additional lift from the increased wing area and aspect ratio, I should be able to fly at the same speed and actually a little less AoA compared to the standard flyer. There will also be a contribution to lift from the thrust of the propeller, which is pointed upward at the AoA. If my AoA is smallish though (less than ~8deg), this should be a small correction.

On the other hand, my wings could fold up and I'll crash and burn!
Got to take her out for a maiden flight tonight! Nice and slow as I hoped, and even survived a few crashes, including a run in with a light pole haha! The wings held up but there they were real bendy with lots of additional dihedral during flight. I came home and added a BBQ skewer strut.
I took my FT flyer mod out flying with my wife yesterday after work. Through a combination of it being too windy and my bad piloting, I folded a wing and she crashed HARD. My power pod looked like a banana, and I broke BOTH blades off the prop! I'm lucky my 2200mAh lipo didn't catch fire!

Here is a pic of the ruined Mk1:

I couldn't wait to build the Mk2 and get back out there! I decided to take RAM's suggestion about adding a KF step to the wing for extra strength and lift as well.

Here is the result of a few hours of work while watching Castle with the wife last night: the BEEFy FLYER Mk2!

2015-09-05 (1).jpg

Hooray for iterative development!


Since you are flying with The Beef, increasing the wing area is sort of opposite of what you'd want to do. I'm not sure what your goal for performance is, but a bigger motor will fly that plane on less wing area.

Here's a thought… Keep the span as you have it in your modded version, but decrease area by making the wing much more narrow. Reinforce that thing. You may just have a hotliner!