Timthetoolman1

My Feedback: (6)

I was given a Kaos, thanks bro, that was partially covered but otherwise almost in ARF form. We are molding Dirty Birdys but I wanted to get everyone else’s out before I started mine (I haven't forgotten you David...eh!) but that left me with no plane for SPA so I moved the Kaos onto the table..
With no information I assumed the top of the fuselage was parallel with the thrust line so I'm using that as a datum to set the wings. I'm also assuming that the wings are set to 0*. There was a large gap between the TE of the wing and the back of the wing saddle of 3/8" or more so I made a plate to go over this area for the wing bolts. Is this normal?
Now the problem was when I mounted the wing it reads 0* but the tip had 2* of wash-IN. Well, horse pucky! I've made 1* or so of correction to uncovered wings but getting almost a 3* twist so I will end up with about 1/2* wash-out seems problematic in the future. I figured I'd share my experiences and maybe hear from some that have experienced this.
The photo shows the jig I set up. I used a long 'arm' so I would have more twisting action than actual weight; however the wing is bowed up towards the tip as well. I found the spot where the builder went awrie and stabilized from that point towards the root so only the tip would twist.
This is its fourth session in traction trying to train the wood and covering to stay where I want it. I heat the covering to take out the wrinkles after I twist it and after releasing I'm not getting anymore wrinkles so I'm getting close. The last check was still 1/2* wash-in so 1* to go then it should relax back to about 1/2*.
If this doesn’t work I will have to strip the wing, shape it, then recover it.

bjr_93tz

Hi Rangerman, I had a twisted built up wing once and the only cure was to strip the covering, remove the shear webs, and re-install new shear webs with the wing twisted to the correct position + a little bit more. It held for a couple of years but the twist slowly returned. Ideally the leading edge sheeting should have been removed as well because that locked in a fair bit of twist.

If you're really lucky and the wing is really flimsy then shrinking the covering will work, but it's a really cheap and nasty way of doing it and probably only suitable for RES glider wings.

I got lucky with a set of foam core wings, the twist was minor and the sheeting had been attached with a water based wood glue so I was able to steam iron the twist out of them, then recover.

Cheers
Brett

Timthetoolman1

My Feedback: (6)

Brett,

I was afraid this method would require straightening the wing before each flight. Hopefully I'll have the Dirty Birdy done for the next event.

I'll be curious to see how this works on foam with balsa sheeting wings. I have a buddy that ended up with a bad wing, maybe I'll experiment.

I thought it would be cool to show others how I fix a wing but I must mention that this should be done before the wing gets covering or glass.

dbacque

My Feedback: (3)

There's nothing wrong with using the covering to correct twist, I use that method for truing every wing I build. And it holds too, especially with MonoKote which has a higher tensile strength than other coverings.

Sounds like you're doing everything right but it can take several cycles to finally get it straight. I've taken more than 3 degrees of twist out of the wing of a Super Kaos 60 this way.

But personally I wouldn't include any washout. A Kaos wing should have absolutely no twist.

Dave