Aircraft starting to snap mid roll.

[Curare]

Hey all, just after a bit of quick advice.

I've been flying my trusty old CAP 10, and once again a problem that has been an issue in the past really seems to be making itself prevalent.

It starts to wind up into a snap during rolling circles. Now as you know there is a point where all of the controls end up mimicing a snap condition but i've never really had another airplane do this.

What's causing it? I know it's a short coupled fat airplane, but even so, it's very irritating.

[rcdart]

Have you ever heard the phrase "snappy cappy"?

You should not have that much control input to initiate a snap, unless maybe flying really slow, I would look at your C of G to make sure it is not to far back.

Also, how much expo are you running, if the expo is really high, you could be getting a situation where it is giving very little movement, then lots, make sure your expo on rudder and elevator in particular are no more than 30 - 35% maximum.

[Curare]

Snappy cappy! Yeah and she'll lomcevak with the best of them.


I usually run at about 25-30% expo, as it feels comfortable, and just quietly I have been shifting the CG back to get it to hover, but being a lardy bastard it doesn't go uphill for long. That being said, she still pitches nose down when hung from the wing tube (approx 33%)

It's a strange plane, considering it's soo short coulped one would expect not to be needing big control throws but, even on low rates and an aft CG she still needs more than I would have expected. I think it may have something to do with the high moment of inertia in the tail.

[Richo]

Pretty much like RCDART said, rearward C of G and being overweight are the enemy of the Cap.

[fastace]

are you doing the rolls in circle pattern abit to fast ? what you need to try is firstly get the C.O.G. in rocking mode slightly nose down , reduce aileron throw and elevator throw but keep a fair amount of rudder throw. test fly a few proceedures of straight line horizontal rolls at medium speed with slight TX stick inputs so the model rolls over slowly and not too fast , if this works better you can then go onto the circle pattern with simular stick controls. the best rolling circle patterns are the slow ones and not the flat out 3D type such as full noise bang bang the sticks. just take it nice and slow and i am sure this model will do it providing you guide it nicely.

[axeman83]

as said above you shouldnt need anywhere near snap level inputs for a rolling circle, unless your talking about a rolling harrier circuit? in either case you could try this, instead of rolling you left stick in a circular pattern ie rudder-down-rudder-up. im asuming you fly mode one, try making it more an exagerated diamond shape if you get what i mean. so you never have much elevator and rudder in at the same time, so your left stick comes back close to center in between inputs, i hope im explaining it right. that said caps and especialy early models 10 and 231 are notorious for this crap, good luck with it mate

[vincentp]

If your CoG is too far forward it can also end up snap rolling during a rolling circle, I've had that happen before with my 2.6m yak.. wit hthe CoG forward you end up using a lot of rudder on knife edge.. push or pull in some elevator to get it round the corner and bam! If you have a lot of expo (more than 50%) on the rudder this can also make it worse as you end up suddenly kicking in a lot of rudder.

Try and get your CoG right otherwise you are wasting your time. Pull up to a 45deg climb, roll inverted and watch what it does.. looking for it to slowly head back to earth in a nice gentle arc.. if she climbs she's tail heavy, if she drops sharply she's nose heavy.

Oh, and wot they said, it's a CAP, only ever had one.. didn't last many flights.

Vince.

[Capt Wally]

Also consider putting small traingle stock stall strips along the LE of each wing panel about half way out to span around a 1/3 of each wing panel length. Had a hanger 9 Cap that was a pig to fly & when we did this it was stable for the first time in it's life. Pull a tght turn & whamoo!!! snapped off at the top of a tight loop or did it's own thing during a tight turn. Cof G as mentioned is critical with the Caps degree here.

cheers

Capt Wally

p.s...Hi Richo, how's the Brissy life going?

[Curare]

I've got some angle ali strips kicking around here. I take it you were using the triangle stock to make a sharp root LE?

[fastace]

you can try this alloy edge along the LE section for a test , use some good quality duct tape to secure it on and if it works i would suggest its time to remove some wing covering and re shape the leading edges to a sharper profile.

[Curare]

Hehehe, I've got nothing to lose!

[Capt Wally]

As "fastace' said, try the triangle piece with one edge protruding into the airflow. This essentially makes the wing stall more predictably in the area of the flow divider strip. If temp fittign with duct tape make sure you have it dead smooth across the face of the strip otherwise you could end up creating a more turbulent airflow over that part of the wing. It's all an experiment & a bit of fun. We also produced some washout byt way of heat warping the wing at the tips on this pig of a Hanger 9 Cap & that seemed to help even more, we never did take the strips off to see if either method worked on it's own as the end result was a more flyable model than ex factory. A friend of mine whom used to teach full sized Aero's in a Cap said pretty much the same thing, when pushed the Cap would behave badly.

Oh BTW just some 6mm balsa stock will work, no need for metal.

good luck & yes you have nothing to loose

Capt Wally:-)