|Sep 09, 2013, 10:00 AM|
HK P51 Profile Fighter
I bought 2 of these with all identical running gear to try some combat RC flying with a mate.
After quite a bit of time at the school of hard landings we have concluded the following:
1. The scale look of the P51 is nice, but the long nose is prone to breakage. I sheeted my nose with kevlar and hotglue. My mate sheeted his nose with Extreme tape over hotglue. They survive much better now.
2. The wings are floppy. Pull anything more than 2G and you will think it has morphed into an ornithopter. The carbon spar should be on the bottom of the wing so its tensional strength will act against flex. We countered by adding a strip of extreme tape along the bottom of the wing. Unfortunately, this acted as a random air brake until we hot glued the edges down to the foam. Now it works great.
3. I glued the body and wing spars in with foam safe CA, but the CA eventually fractures and the spars slide in the slot. Suddenly the plane flexes randomly in odd places. I am sure this is part of the cause of the random tricks these planes are known to perform. Eventually I cut the CA away with a dremel tool and replaced it with hot glue. Much more shock resistant and now sticks to the ground surface of the rod better.
4. Various web comments indicated the roll rate was pretty poor. I built the planes with two aileron servos. Cut them into the surface of the wing and hot glued them in. Strength as good as the original wing and HXT900 servos are so light that one extra makes little difference. Snap rolls like a 3D plane now
5. The standard CG (55mm) is too far back. It looks about right, but it is the major cause of sudden unexpected stunts which often end in a death spiral. These planes will tolerate a CG right up to about 20% from the leading edge and still fly well. We are now flying them at 45mm and they are solid and responsive in the air. Found this out when I busted a motor and had to replace with one nearly double the weight. POWER covers many sins! Later I repaired the original motor and we are still using them, but I can see there will be a thirst for more power when we get good enough to use it
6. We use plastic flagging tape as a streamer. It looks too tough, but it cuts easily in a whirling prop and it makes a good snap sound to confirm a touch. It is also waterproof and reusable
7. The supplied props are way too flimsy. Both were toast after the first test flights. GWS orange plastic 9x7.5 are a cheap effective replacement, but any heavy landing will cost you another one. Now we are using solid grey plastic 9x7.5 electric props. They are a bit heavier, but that helps with the CG issue and they seem pretty bullet proof.
Some video of R&D here:
P51 Profile Fighter test flights (1 min 51 sec)
Bullet proof P51 (1 min 56 sec)
Some dogfights after we got everything working:
P51 Dogfights get serious (7 min 46 sec)
|Sep 14, 2013, 12:06 AM|
Lamination would stiffen the wings up nicely. Just need to make sure whatever you use sticks to EPP really well. Not many adhesives do that, but I guess you might do OK if you sprayed the foam with super77 first.
|Sep 16, 2013, 08:09 AM|
The power of the stock motor is plenty. They will climb vertically at full throttle with a good 20c 3S battery. Maybe you could use more power, but this amount of power forces you to FLY the aeroplane and conserve energy like a real dogfight. Any more and you will just be flying 3D with streamers.
More power will also increase the severity of crashes, both mid-air and ground intersections. It is already possible to shatter these in a diving collision (see the end of the third video!).
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