Flight B/C

[pumptato-cat]

Unfortunately, I can't do glide tests in my house without crouching and releasing the plane at almost knee height. When releasing at knee height, it turns to the left... When releasing any higher(shoulder height ish) it begins turning right. I'd do more testing and change wash-in, but it's crashed twice pretty nastily into chairs, lamps, and more...
Any ideas on why it might change direction depending on what height it's launched at? I'll try changing wash-in when I get back to my flying site, but as of now, I'll have to settle for my hazardous glide tests.

Cat,

This makes sense. It takes a moment for the airplane to build up speed (higher launch height). And washin has greater effect at higher speed.

Brian T

Ohhh I see, thank you! I'm going to try to fly tomorrow or Friday, but I might have to wait until the weekends... I'll try decreasing wash-in like Coach Chuck said and just see what happens.

I'm still not sure why the plane flew very well with 1/2" of washout before regionals--it seemed perfectly fine on .3oz torque(same value I tested with two weeks later). I do think something must've been dislodged or bent, but I can't find anything wrong with the plane after checking over everything multiple times. I'm just utterly confused on why such a major change occurred... and why adding rudder offset would make the turn to the right worse. Shouldn't this year's planes fly with a very large amount of wash-in? I suppose scratch-built planes or different kits would be different but I'm not sure why adding a tailboom would change amount of wash-in required. Anyone have any ideas as to what happened? I've had some people I know look at it and they can't see anything wrong, either.

I'll update with stab and rudder tilt angles tomorrow, but just by eyeballing them, the tilt looks significant enough to make the plane turn..

[coachchuckaahs]

Look for twist (wash) in the stab. This can cause strange issues. Also weak joints from wing post to wing or to motor stick. A weak joint here can cause wash to change during flight.

Since you added a person's thinner tail boom, one possibility is it is not stiff enough torsionally. Them a minute amount of stab twist could get amplified considerably with speed. Same with weak joints stab to boom

Coach Chuck

[pumptato-cat]

Okay, thanks! I've checked the wing joints and all I see is that I'm only using one rubber band on the front of the wing saddle, but two on the back(I lost one... the kit didn't have any spares) I don't think this is the issue, because it was flying fine before.
You might be right about the tailboom--If I use significant force it does wiggle a bit(the wood, but not the joint). I looked at the stab closely and it seems like the left and right sides of the trailing edge are tilted upwards slightly-probably around 1/16"? Not sure if that might be an issue. I measured both the stab tilt and rudder offset-both are ~1.94deg. Not sure if that is sufficient or not.

[jgrischow1]

Any suggestions for fixing a rear stab (carbon fiber) that's warped? My kids tried to put weights on it and flatten it out overnight but that didn't do much.

[bjt4888]

Any suggestions for fixing a rear stab (carbon fiber) that's warped? My kids tried to put weights on it and flatten it out overnight but that didn't do much.

Jg,

You can’t straighten warped carbon rods. However, you can tweak the flying surface (I assume it’s the stabilizer with the problem) to minimize the detrimental effect. For instance, if the warp is trailing edge down on the left side, this is not much of a problem if it’s only a degree or so of twist. A small amount of washin on the left side of the stab is occasionally used as a trim method. You may mean 0.5 degrees of additional decalage to compensate.

A picture of the warp would allow us to diagnose and give a better recommendation.

Brian T

[bjt4888]

Any suggestions for fixing a rear stab (carbon fiber) that's warped? My kids tried to put weights on it and flatten it out overnight but that didn't do much.

Jg,

You can’t straighten warped carbon rods. However, you can tweak the flying surface (I assume it’s the stabilizer with the problem) to minimize the detrimental effect. For instance, if the warp is trailing edge down on the left side, this is not much of a problem if it’s only a degree or so of twist. A small amount of washin on the left side of the stab is occasionally used as a trim method. You may need 0.5 degrees of additional decalage to compensate this particular warp.

A picture of the warp would allow us to diagnose and give a better recommendation.

Brian T

[bjt4888]

I meant to select “edit” and accidentally “quoted” my message to edit it.

[pumptato-cat]

Thanks so much for the help everyone!!!
The plane (I will be flying this weekend, only was able to do glide tests today :/) has a very long, flat glide with a slight left turn at the end. I changed the shim position by barely anything, probably around 1mm. Are this year's planes really that sensitive to wash-in? The warp was reduced a little, and then it just magically started turning left. Quite odd. If I reduce it further, the turn tightens up...
It's so sensitive I might have to just glue the shims in. Very strange, compared to my FF stock plane.

[bjt4888]

Thanks so much for the help everyone!!!
The plane (I will be flying this weekend, only was able to do glide tests today :/) has a very long, flat glide with a slight left turn at the end. I changed the shim position by barely anything, probably around 1mm. Are this year's planes really that sensitive to wash-in? The warp was reduced a little, and then it just magically started turning left. Quite odd. If I reduce it further, the turn tightens up...
It's so sensitive I might have to just glue the shims in. Very strange, compared to my FF stock plane.

Cat,

Yes, the airplanes are that sensitive to washin adjustment. This is the reason we don’t use a moveable wing saddle held in place by rubber bands. While the moveable saddle allows adjustment of CG, it also creates the potential for accidental change in washin when you have a hard landing.

Yes, once you have washin where you want it, place a small dot of duco cement on the back edge of the shim and a medium sized dot of duco on the front edge of the saddle to bond them to the motor stick.

Brian T

[jgrischow1]

Any suggestions for fixing a rear stab (carbon fiber) that's warped? My kids tried to put weights on it and flatten it out overnight but that didn't do much.

Jg,

You can’t straighten warped carbon rods. However, you can tweak the flying surface (I assume it’s the stabilizer with the problem) to minimize the detrimental effect. For instance, if the warp is trailing edge down on the left side, this is not much of a problem if it’s only a degree or so of twist. A small amount of washin on the left side of the stab is occasionally used as a trim method. You may mean 0.5 degrees of additional decalage to compensate.

A picture of the warp would allow us to diagnose and give a better recommendation.

Brian T

https://drive.google.com/file/d/15lgztN ... share_link
https://drive.google.com/file/d/1rzL4hv ... share_link

Unfortunately it looks to be the opposite of what you hoped!