B.Matt

Recently started building a sig four star. I notice the spar wood was warped but figure it would pull togehter an be strait. It wasn't, after speacking to several experienced kit builders i was told to always check wood for warpage before you start. The wood should be strait. I called sig and they said it doesn't matter if the wood is warped and i did something wrong. I ended up buying a new wing kit from sig. My building surface is perfectly flat so i dont't think that is a problem. What do you guys think?
Thanks
B. Matt

FLYBOY

My Feedback: (11)

If you start with warped wood and don't get it all supported right, it will be warped. 9 times out of 10, the warps are not enough to matter a lot, but if you use lines when sheeting and get it as perfect as possible, you can build with the warped wood. How bad is your wing? Chances are you can get twist out with the covering.

B.Matt

It has about a 3/16 bow in the trailing edge. From what i was told the wood should not have been warped to begin with

FlyingPilgrim

My Feedback: (26)

Frequently the wood is warped- fact of life. Think of all the changes in temperature and humidity between the factory, shippers, distributors, retailers, and your shop! If it is structurally supported by other parts, you can usually "build out" the warps (support it to straighten it) just by assembling the other parts around it. If the spars are warped, they need to be warped (roughly) in the same area and same amount so if you assemble the warps opposite, they cancel each other out. Frequently I have had to take a trip to the LHS to buy some replacement wood when the kit supplied stuff is not up to par. No big deal unless it's a major component or the majority of the kit. You could try soaking your warped area with windex or water/alcohol mix and weighting it down to see if you can correct some of the warp in your wing. As said above, if it is a twist in your wing, you may be able to straighten it with the shrinking of your covering. Good luck.

Pilgrim

MinnFlyer

My Feedback: (4)

A Bow and a Warp are two different things. If it bows top to bottom, or front to back, You'll never notice it in the air.

What is bad, is when the airfoil is twisted. This will make the whole wing act as an aileron (And even THAT is ok as long as both wings are twisted the same. Some wings even incorporate this as wash-in or wash-out)

gwk

I think I've found a solution to warped spars. What I do is wet all four main spars, and place them, length wise over a dry sponge or other firm surface (approx 3/4 to 1 inch in height). The sponge or what ever you use should be in the center of the spars. Allow to completly dry!!!! You then should have 4 spars all bowed the same way. Then when building the wing make sure the arc of each spar ( use in each wing panel ) face each other. Maybe miniflyer can do a sketch.

Greg

w0mbat

My Feedback: (1)

Unless every piece of wood warped in the same direction and the sheeting is warped sideways (which I have never seen happen), your plane will come out straight - as long as everything was pinned straight to the building board and glued properly. If it does end up warped even after you insured that it was pinned straight - then the best thing to do is throw it away and get something else, because the wing was not designed correctly and will never hold up in flight. We go through thousands of pieces of balsa every week and the degree of warp in each piece directly relates to the weather conditions. We get calls all the time from people who want replacement wood because the wood they received in the kit was warped. They don't realize that even if it is straight when we send it, it will warp by the time it gets to them because it is traveling though different climates.


Mike Grey
Skyshark R/C

gwk

Mike
Mike
Your kits are top quality! When someone buys a kit with bowed spars that bow at random, you definitely have a tendency to bowing (not forward and back wards), but tip to center. Most kit manufacturer want you to assemble the wing dihedral before sheeting, and bottom first, so sometimes control is lost. I'm building two Topflite Giant P 51's, and you have to be very careful when sheeting to avoid warps. I used my method of spar reworking and both are right on.

Greg