Avoiding Warps in wings & structures.

**wonwinglo** · 05-05-2004

Scale modellers,most warps start during the build on the board,the temptation to lift off before the glue really has cured out is usually the cause,what also happens is that stresses are inbuilt which when you cover the model can excaberate the problem,damp balsa will also cause warps.
Back to your problem I would suggest that you always pin down any structure in future whilst covering or water shrinking,however all is not lost,you could try steaming out the warps by holding over the spout of a kettle and allow the steam to do its job,simply twist the opposite way to the warp,take away from the steam and hold for a few minutes,keep doing this until the shape is right.
Another common cause of warps after doping apart from not pinning down to the board, is the application of too powerful a shrinking dope,always thin down your dope with thinners,add a small amount of castor oil to the dope,this has the effect of flexing the dope which becomes brittle with age,a tiny drop of castor oil with a smidgin of oil of wintergreen will stop the dope from blooming,I learned this trick when doping up full size airplanes as a airplane engineer,it really works.
But I stress only a tiny amount of each otherwise your dope will not dry out at all !
Always take care with these light structures,also cosider the use of thinned PVA glue as your dope,only slightly heavier it does not warp your structures as badly as ordinary clear dope can,I now use this on all of my models because in about five years time cellulose clear dope will be taken off the market anyway as it has been found to destroy the ozone layer.
We are just going to have to live with alternatives just as the automobile industry are adapting to alternative and superior finishes on vehicles.
Remember now the golden rule,always pin down any structure and leave well alone until the adhesive sets properly,re-pin if you can whilst covering on these frail structures,and flex your dope if that is what you are using.

bartley · 14-03-2005

Quote:

Originally Posted by wonwinglo

Scale modellers,most warps start during the build on the board,the temptation to lift off before the glue really has cured out is usually the cause,what also happens is that stresses are inbuilt which when you cover the model can excaberate the problem,damp balsa will also cause warps.
Back to your problem I would suggest that you always pin down any structure in future whilst covering or water shrinking,however all is not lost,you could try steaming out the warps by holding over the spout of a kettle and allow the steam to do its job,simply twist the opposite way to the warp,take away from the steam and hold for a few minutes,keep doing this until the shape is right.
Another common cause of warps after doping apart from not pinning down to the board, is the application of too powerful a shrinking dope,always thin down your dope with thinners,add a small amount of castor oil to the dope,this has the effect of flexing the dope which becomes brittle with age,a tiny drop of castor oil with a smidgin of oil of wintergreen will stop the dope from blooming,I learned this trick when doping up full size airplanes as a airplane engineer,it really works.
But I stress only a tiny amount of each otherwise your dope will not dry out at all !
Always take care with these light structures,also cosider the use of thinned PVA glue as your dope,only slightly heavier it does not warp your structures as badly as ordinary clear dope can,I now use this on all of my models because in about five years time cellulose clear dope will be taken off the market anyway as it has bennfound to destroy the ozone layer.
We are just going to have to live with alternatives just as the automobile industry are adapting to alternative and superior finishes on vehicles.
Remember now the golden rule,always pin down any structure and leave well alone until the adhesive sets properly,re-pin if you can whilst covering on these frail structures,and flex your dope if that is what you are using.

Thanks for all the tips. If done gently would the steam trick work on a wing already covered with Solartex?

Thanks again, Steve.

**wonwinglo** · 15-03-2005

Bartley,you can at least give it a try,nothing to loose here,what you will probably need to do is check for further warping after giving this treatment,they have a nasty habit of re-appearing if not checked,you could also try this idea below additional to the above-
Pin the wing firmly down to a flat board,thick MDF is excellent but you will probably need to lash it to the board with masking tape to get the wing flat again,take your heat gun and play the heat over the entire wing evenly,do this a few times and leave overnight before removing the tape.
The problems with Solartex pulling structures out of line due to uneven initial shrinkage is well known,usually what causes this is one surface is covered with the material and shrunk up before covering the opposite side,to do the job properly loose cover both sides and play heat equally either side with the gun,lay onto a flat board and place weights onto the wing protected with some pop wrap film,allow to cool and lift off after several hours,any awkward wrinkles can be removed with the iron.
Failing removal of the warps I suggest that you strip the wing of covering,pin back down onto the building board,gusset up any stress spots and recover,a major job but better and quicker than having to build another wing.
I hope that this assists you solve this problem.

**wonwinglo** · 15-03-2005

The steam trick should still work,its leaving the wing to cool naturally fully flat on the board that counts,no harm in trying.