Jeff's FPV and RC Planes: DW Foamies BAF Yak 48"

I finally went ahead and got one of the DW Foamies 48" Yak 54. Going to run my Turnigy 35-42C 1100kv motor in it with a 40A Turnigy ESC and either an APC 11x5.5E or 12x6E prop. Probably try to pick up some 1800mAh 3S1P Lipo's for light flight, but 2200mAh will be normal. Want to also try 4S 2200mAh. Went with 4 hitec HS-65HB servos, which are a little spendy, but not as much as the metal gear ones. I'll keep this section updated with the build thread. Final AUW with landing gear and no battery is 26oz. Including the 2650mAh 3S1P Lipo, it is 34oz. The 4S1P lipo is slightly lighter by half an ounce.

Update 2/7/10: Finished the build and couldn't stand it anymore. It has begun blowing more and more all day. The plane wants to hover just below 2/3rds throttle and it buffets the tail pretty good from the air over the APC 11x5.5E prop. I need to put my Eagle Tree eLogger v3 on it to check currents and power (see below), but seems good. I maidened it inspite of the wind. It feels heavy. I may have to try the 2200mAh lipos. Also may need to move the wings to the center slot (they are all the way back right now). Flew straight and pretty well behaved with only a couple clicks of trim. Wind was really gusting, but it was well behaved (seemed to have some tip stall when trying to do elevators with no power). I'll have to try it without the wind.

Update (2/8/10): Peak power is 456W, but sustained is ~420W on 3S1P with the 11x5.5E prop and ~35A draw. Something seems wrong with the 4S1P, though, because peak power was 451W (sustained around 420W again) with peak current at 32A and sustained around 28A. Motor also seemed slugish to respond going to full power from 1/8th throttle. I may need to play with timings.

Update (2/9/10): Wind was calm when I came home at 5:15PM tonight (super early for me), and there was still some sunlight. So I grabbed my radio and the Yak and ran across the street. Anyway, this thing does elevators like nobody's business (has a tendancy to want to roll/turn right, which is the Lipo side, both inverted and upright, so I think that is a big part of it, I'll have to check lateral balance). I normally fly in a single lot small park space (ok, it is really just a big drain area for high rains), but it has houses and trees on all sides, so it gets tight real fast. I suck even more than I thought on 3D with this plane (at least my smaller sub-8oz planes I could float and play with...this one really moves and feels heavy compared to them). I ran a 2200mAh 4S on a 11x5.5E, and W-O-W. It moves. Actually swamps the ailerons even with HS-65HB's. I have the wing in the far back position and CG is right on the spar. Even there, the precision on this plane is pretty obvious. Nice lines.

Now, my problem. I do tight loops with full throws, and it is pretty nice and well behaved. But doing waterfalls and tight outside loops it really does a roll left tendancy. I'm sure I'm flexing somewhere, because backing off the throws to about half doesn't have the same bad tendancies. Any hints from anyone where to start to look at this? Maybe the lipo off balance to the right is to blame like the elevator maneuver suggests and a tight loop is enough to stall the wing and cause it to roll. Flies pretty good both slow/fast and upright and inverted, so I think the CG is pretty good and trims nice.

Need to get some more time on this plane. Hope I can get some video I'm not embarrased to actually share soon.

Update (2/10/10): Have definately confirmed that the lateral balance isn't great on this plane with the lipo being the most likely cause. I think the full stall up elevator glide (elevators maneuver) tendancy to drop the right side into a turn both inverted and upright are the biggest clue it is the lipo lateral balance.

Update (2/12/10): Got data recorder connected to gather real time data while flying on 4S1P and 3S1P (both 2200mAh) with APC 11x5.5E prop. Unlike the static measurements, this one shows the 4S peaking at 550W (typical full throttle bursts ~520W) and max 39.93A (typical full throttle bursts ~38A). Compared to 3S which typically ran 280W during full throttle bursts and 29A.

Original packaging from DW Foamies came in super trashed. Most of the contents were ok, but had a couple of the parts creased and dented when looked a little closer. Mike from DW Foamies was super to work with and got me replacement parts out very quick!

Showing some of the damage on the spare sheets of 9mm depron.

Wings pinned and doing the aileron hinges. This is after doing the 45' bevel on the aileron surface and 15' bevel on the wing mating for some good throws. I sort of messed up here, as I had been wanting to try the welders glue hinge trick, but turns out the welders eats some of the depron. It wasn't bad, but it did gap a little on the really thin parts of the bevel. Hinge is good and strong, though, and I don't think it is going to be a problem, just more superficial than anything.

Close ups of the gap that formed from the glue.

Another close up. I think doing the welders glue on EPP would be great and I'll probably try it on my Piaget next time, but will just do the blenderm tape if I were ever to do this depron again.

Left wing with aileron hinge taped over the welders (probably didn't need to do this) and the spare CA'ed in and taped over with blenderm. Also shows the color tape that I'm planning to do. There is a great thread on RCGroups.com that covers doing this, including some tricks for the checker board.

Picture of how you start out with the checker pattern.

The fuselage with some of the spare checkers from the wing to be used on the vertical stab.

Picture with all the checkers finished.

Final pics of the scheme with the left side red stripe and all the vinyl decals. Yes, I screwed up the "YAK ATTACK" decal (put it on facing the wrong way, AND it gets covered by the horizontal part of the fuse too...sigh).

Final scheme test fit together before gluing. The vinyl really adds some good lines and looks great.

Another picture before gluing from the left side. Hopefully the red will add some good contrast when I'm practicing my rolling harriers. The bottom is all plane white.

Getting the servos mounted and setting the throws.

More pictures of the rear servos.

Left side routing of the servo wires from the rear (including 9" extensions), which were hot-glued to secure them. Turnigy Sentry 40A ESC also pictured.