I have a Great Planes Cap 21. It is a great looking plane. It is powered by a ST45, Pitts muffler. I just flew it again this past weekend, and I'm amazed all over again, just as I am every time I fly it, at how badly it flys. I know it has earned the nickname, "Snap 21", but I can't figure out why it flys the way it does. I tinkered with installing the FMA auto pilot on it last week, and while it may tame it in the air, landings will still be fatal. It is almost required to land at 3/8 throttle to avoid cartwheeling. Unfortunately, my last landing was a little less than 3/8 throttle, and after cartwheeling, it hit the spinner so hard it broke the motor mount.
In the air trying to do loops without having it "snap" out on top takes a really light finger. I set low rates so low you had to look twice to see if the elevator was in fact moving. I also set exponential at 67%. One out of five loops will complete without snapping out and "hunting" the ground.
I'm not the best pilot in the world, but I have always been able to land anything. that is until I met up with this Cap. Anyone have any similar experiences?

Hello snapy freind
I build my over two winter and flew it for a couple of saison
with a YS140FZ weight 10.5Lbs! I lighted up the fuse with holes
and removed the insid turtle deck foam to keep it light,it is cover with monocote. I have 2 ail servos,1elv1rud,1throt.
the plane fly very well, no bad snap habbit since it has been kept light durring building it!
I have max throw on every surface control with EXPO.
does ALL the maneuvres very well.
and land like H9cap232 (slow).
I your case I would suggest to have enough power to pull quikly
from a stall, make large smoth turn, Cg it 5-7deg on the noze down very important! this is a short nose airplane you'll need
to light up the taill or extand the nose to keep it light.

I have some pics at http://www.wingandrotor.org under Planes

good luck :idea:
Erol

Erol: Are we talking about the same plane? Here is a pic of my "demom".

Basically, the Cap 21 is a *iss poor design.....both full scale and model...it just shows itself worse in the model. Biggest problem is weight and wing area.

ME

Jim,

If I am correct, you are referring to the GP Cap kit that is discontinued. I started mine @ 8 years ago - tried HobbyPoxy primer on it - and put it away. That primer was god awful. Whenever I had a choice between watching paint dry and sanding that junk off, I chose to watch paint dry. Just finished repriming it yesterday - will paint it this week. The wing will be Monokoted. But yes, I recall reviews where this thing was a real handful to fly - and it snapped just like you say. I don't know the answer, but I'll start out real nose heavy and use lots of expo. I want to finish the plane - but I am not sure if I want to fly it - maybe it will go on the block before I do get the itch to fly it. Or, maybe I'll let my buddy fly it and trim it - he is real good at that. He never uses dual rates - just cranks it up all the way on ATV and uses 80-90% expo on all his planes - even his 3D stuff.

Dan

I just finished an old Zimpro CAP 21. .60-size, 62" wingspan, 8#, Saito .91 four-stroke. This plane flies AWESOME!!! it will do everything I am capable of and more! No bad tendencies (that I have found yet) and lands like a *****cat! Sorry to hear yours is not as enjoyable!

Regards,

Jeff

Lands like a ***** cat?

Is ***** a bad word?

Not in MY book!

I've built and flown both the .40 size (ST .45) and the .60 size (OS .61 SF) with excellent results. The .40 size was a blast to fly at about 5 1/2 lbs dry. If it is snapping on you move the CG forward. I had problems with BOTH of the GP kits being tail heavy and ended up adding quite a bit of nose weight to each before they would fly well. I had almost a POUND of lead bolted under the engine mount in the .60 CAP 21 but it flew very well. It weight about 9 lbs dry and with a 12/6 Zinger, 20% nitro the Long Stroke .61 could just pull it through a tall vertical eight starting from the bottom. You had to hold a little power on to land it but after getting the CG and thrust right it NEVER exhibited any snapping tendencies unless you pulled hard at low speeds. The Caps fly well if set up properly and should be capable of doing every manuever in the book with sufficient power.

You notice that I speak of both the Caps in the past tense. I wore the .40 size Cap out several years ago and after many, many flights I center-punched a steel light pole at our field with the .60-size on a long approach. That's what happens when you fly too late in the day and your depth perception ain't the best in the world. :stupid:

I've also watched a full-size Cap21 doing competition aerobatics and it was impressive. It's an outmoded design now but I disagree with those who say it was a poor flyer.

Had a couple of 40 size GP Cap's myself. They were dubbed "snapping caps" for a reason. If you loose an engine forget about streching the glide. When doing spins, stop very early and get plenty of speed before pulling out try to soon and it will just spin tighter. As far as low speed handeling it really fools you. It comes in looking rock stable....slow it down a bit more .............pull the nose up for a flare.....and........BAM!!! it stalls with a vicious snap and gives zero warning before it goes. They are a challenge to fly. I sometimes miss them. Be carefull and enjoy
My 2 cents
Brian

I don't think mine flies much different than my 1/4 Sukhoi or Extra.
The old 21 is lighter and not as 'beefy' as the newer 'Edges' and 232's so it doesn't require the power but, I don't think it snaps any worse than the others.
Keep the CG right-on or slightly forward and it's a great aerobat.
It was my first low-wing about 13 years ago!

Good luck!!! Kirk