cap snapping
04-12-2003, 12:16 AM
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cap snapping
Reduce your throw on the elevator to about 3/8" for low rates, that will turn most Caps into a docile bird. Get an Edge or and Extra and eleminate the problem! Pete
04-12-2003, 12:04 PM
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cap snapping
Definately not a problem with elevator throw... on low rates with expo, I'm only getting about 3/8" of throw, and it still snaps. I'm thinking that it's a combo of the hinge gaps and the CG being a little off.... It's the Matt Chapman cap 232, Moki 1.8 combo that I have. Sooooo.. do the non-sealed hinge gaps play into this as well possibly??
04-13-2003, 12:28 AM
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cap snapping
A CG to far aft will cause it to snap ( as already posted). A wing that has a + incidence will do this as well especialy if it's just at the tip (warped wing). Don't ask me how I know! Check your plane over carefully. My GP Cap 231EX (.46 size) was just this way, nothing I could do about it.
04-14-2003, 03:16 PM
#9
cap snapping
Tip stalling can sometimes be alleviated by "reflexing" the ailerons. RAISING (that's right) both ailerons 1 or 1.5 turns on the clevis will in effect reduce the wing tips' angle of attack, thereby improving stall characteristics.
If you have a computer radio, you can set this to work only on landing which would preserve the "snappyness" for tumbling maneuvers.
There's a reason the old Cap 21 was called "Snap 21"
If you have a computer radio, you can set this to work only on landing which would preserve the "snappyness" for tumbling maneuvers.
There's a reason the old Cap 21 was called "Snap 21"
04-14-2003, 03:27 PM
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cap snapping
Do you happen to have dual elevator servos? I have an Extra that was "snapping"... or so I thought. I had one elevator that would move a small amount more than the other. This was causing the problem.
Mike
Mike
04-14-2003, 04:28 PM
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cap snapping
DO NOT REDUCE THE ELEVATOR THROW!
Put an incidence meter on the wing panels (root and tip) and get rid of the warp! Turn the radio on and check the ailerons too, they may be warped. You can add a little washout if you like.
Mike's right, check that the elevators have equal travel at all stick positions, not just full up and full down. I used an MK ball bearing bellcrank to run mine but there are several ways to improve the "Y"'d pushrod.
Raising the ailerons a turn or two can help but make sure that they're straight first.
Additionally, the Cap has a high thrust line and low center of drag, it requires 1-2 degrees of up thrust on the motor. At 0 or negative the plane will balloon when you chop the throttle.
I'm on my 4th and have set up several others with ST 2300, Moki 1.35, 1.8's and 2.10's. All balanced at 25-35% of the MAC, ran +/- 45 deg. (2.5 inches) on the elevator and as much aileron and rudder as we could get. None of the above airplanes had a snap habit once the warps were straightened out. My latest even had - 1.5 deg in the left panel and + 2 deg. in the right. After I fixed it the wing rocking in high alpha stopped.
Chris
Put an incidence meter on the wing panels (root and tip) and get rid of the warp! Turn the radio on and check the ailerons too, they may be warped. You can add a little washout if you like.
Mike's right, check that the elevators have equal travel at all stick positions, not just full up and full down. I used an MK ball bearing bellcrank to run mine but there are several ways to improve the "Y"'d pushrod.
Raising the ailerons a turn or two can help but make sure that they're straight first.
Additionally, the Cap has a high thrust line and low center of drag, it requires 1-2 degrees of up thrust on the motor. At 0 or negative the plane will balloon when you chop the throttle.
I'm on my 4th and have set up several others with ST 2300, Moki 1.35, 1.8's and 2.10's. All balanced at 25-35% of the MAC, ran +/- 45 deg. (2.5 inches) on the elevator and as much aileron and rudder as we could get. None of the above airplanes had a snap habit once the warps were straightened out. My latest even had - 1.5 deg in the left panel and + 2 deg. in the right. After I fixed it the wing rocking in high alpha stopped.
Chris
04-14-2003, 05:00 PM
#14
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cap snapping
Originally posted by bdtsr
The GP Cap 231EX has a very short wing (LE to TE) which enhances the snapability of the plane.
The GP Cap 231EX has a very short wing (LE to TE) which enhances the snapability of the plane.
04-15-2003, 11:36 AM
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cap snapping
Paul,
Most Cap's pitch up when you reduce throttle on landing, or balloon, due to the high thrust line and low center of drag. To correct this you add 1-2 degrees of up thrust on the motor mount. The 1/4 scale Cap fly's great with 1 degree of up. Using a meter check that the wing is at 0 degrees, the stab is at 0 degrees and the motor is +1, 1 set of washers under mount on the bottom usually works.
The biggest problem people have with the Caps is the enormously powerful rudder and elevator, it's also its greatest virtue. The design isn't any more prone to "snapping" than an Extra, in fact they have virtually the same wing and the Cap has dihedral to boot! What it does have is an elevator and rudder powerfull enough to stall the wing at any time in any condition, regardless of speed.
Consider a stall being when the wing exceeds the critical angle of attack and stops producing lift. You can do it with pitch or with yaw. Example: During full throttle level pass, apply full rudder and the plane will tuck under in a violent snap roll. During a hard "bank and yank" turn, you apply too much elevator and it'll snap out.
The movement of CG effects the force required to induce these pitching and yawing movements. Like moving the fulcrum point on a lever.
If you keep the Cap light and make sure that it's straight as an arrow it'll be the most impressive flying plane you've ever flown. Most guys that fly them get hooked, you'll love it. Just ask Mike, we've both got the Cap virus bad.
Chris
Most Cap's pitch up when you reduce throttle on landing, or balloon, due to the high thrust line and low center of drag. To correct this you add 1-2 degrees of up thrust on the motor mount. The 1/4 scale Cap fly's great with 1 degree of up. Using a meter check that the wing is at 0 degrees, the stab is at 0 degrees and the motor is +1, 1 set of washers under mount on the bottom usually works.
The biggest problem people have with the Caps is the enormously powerful rudder and elevator, it's also its greatest virtue. The design isn't any more prone to "snapping" than an Extra, in fact they have virtually the same wing and the Cap has dihedral to boot! What it does have is an elevator and rudder powerfull enough to stall the wing at any time in any condition, regardless of speed.
Consider a stall being when the wing exceeds the critical angle of attack and stops producing lift. You can do it with pitch or with yaw. Example: During full throttle level pass, apply full rudder and the plane will tuck under in a violent snap roll. During a hard "bank and yank" turn, you apply too much elevator and it'll snap out.
The movement of CG effects the force required to induce these pitching and yawing movements. Like moving the fulcrum point on a lever.
If you keep the Cap light and make sure that it's straight as an arrow it'll be the most impressive flying plane you've ever flown. Most guys that fly them get hooked, you'll love it. Just ask Mike, we've both got the Cap virus bad.
Chris
04-15-2003, 01:53 PM
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Lanier CAP
I'm currently tuning a CAP 232 Lanier ARF that I bought used. I believe I have once and for all proven that it doesn't save any time to buy a used plane. I could have gotten the kit built and ready to go in this much time - and lighter too.
Anyway, these are all good suggestions. With so little elevator throw, doesn't it take almost all the elevator throw to get the thing leveled for landing? Right now I actually have too much up-thrust, so it dives for the ground at idle. Tough to land that way.
I also have a snap problem - seems to happen to the same direction almost every time. Gotta true this thing up. I already checked elevators - but will re-check. I gotta do the lateral balance as well.
Also, I had a friend suggest using turbulators on the outer wings to help tame the snap. I'm gonna give this a try as well. I'll report the results.
Anyway, these are all good suggestions. With so little elevator throw, doesn't it take almost all the elevator throw to get the thing leveled for landing? Right now I actually have too much up-thrust, so it dives for the ground at idle. Tough to land that way.
I also have a snap problem - seems to happen to the same direction almost every time. Gotta true this thing up. I already checked elevators - but will re-check. I gotta do the lateral balance as well.
Also, I had a friend suggest using turbulators on the outer wings to help tame the snap. I'm gonna give this a try as well. I'll report the results.
04-15-2003, 02:17 PM
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cap snapping
John,
The turbulators work well. I have a friend that adds them to everything and amazes people with how docile some of his planes become.
I'd definitely meter the wings and check for warps first. Laterally balancing the wings makes a big difference too.
My friend will try out turbulators by taping some triangle stock or even square stock to the leading edge at the tip.
Chris
The turbulators work well. I have a friend that adds them to everything and amazes people with how docile some of his planes become.
I'd definitely meter the wings and check for warps first. Laterally balancing the wings makes a big difference too.
My friend will try out turbulators by taping some triangle stock or even square stock to the leading edge at the tip.
Chris
04-15-2003, 05:09 PM
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cap snapping
The easiest way to add washout is to flex the tip and use a heat gun to take out the wrinkles (it takes about 1/2 hour and two people)
Put a meter on the wing and get a baseline first. Flex the tip - trailing edge up, leading edge down and shrink out the wrinkles in the covering. Continue flexing the tip until the covering cools. Now repeat on the bottom of the wing. Each time you do it you'll find that the wing has "given" a little in the right direction. It usually takes 5 or 6 times on each side.
1/2 - 1 degree of washout is plently. Just matching the incidence between the two tips will probably make a noticeble difference.
Chris
Put a meter on the wing and get a baseline first. Flex the tip - trailing edge up, leading edge down and shrink out the wrinkles in the covering. Continue flexing the tip until the covering cools. Now repeat on the bottom of the wing. Each time you do it you'll find that the wing has "given" a little in the right direction. It usually takes 5 or 6 times on each side.
1/2 - 1 degree of washout is plently. Just matching the incidence between the two tips will probably make a noticeble difference.
Chris
04-23-2003, 01:49 AM
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cap snapping
JohnG,
I also just bought the Lanier Arf used. The first three flights were perfect but on the fourth it snapped out at the bottom of a loop. I guess to much elevator not enough power. I saved it with very little room to spare and only because I had snapped the simulator enough times to know what to do.
I am moving the CG forward to the factory recomendation untill I get to know it better, changing the rudder to pull-pull so as not to have to add weight.
Other than it scaring the heck out of me I like it so far, especially with the brison3.2.
Richard
I also just bought the Lanier Arf used. The first three flights were perfect but on the fourth it snapped out at the bottom of a loop. I guess to much elevator not enough power. I saved it with very little room to spare and only because I had snapped the simulator enough times to know what to do.
I am moving the CG forward to the factory recomendation untill I get to know it better, changing the rudder to pull-pull so as not to have to add weight.
Other than it scaring the heck out of me I like it so far, especially with the brison3.2.
Richard