joeydonutz

Just starting a 4*60 and noticed that the main spars for the wings not only have bows in them but they are hooked pretty bad. I know that I can work with the bows by matching them top and bottom with the bows facing each other but what about a hook in the spar? Can I work with it, bend it, pin it down? My intuition says to replace them but I don't want to shell out the money if I don't have to. I'm including a pic of just how bad it is.

I'd also like to say "thanks!" to all for the great posts. I'm a semi-new builder and I've learned a lot from the members here. Your experiences are well appreciated.

Redback

Go with your intuition.

Better to spend a few $$$ now than have a plane that doesn't fly as well as it should. The 4*60 doesn't have a sheeted LE that could help to lock the wing straight.

My $0.02 worth

Terry

Lightfoot

My Feedback: (1)

You could easily get new spars from Sig just by letting them know of the problem. Personally, I would go to the LHS so I could pick out the pieces I want to use. The spars are the pieces that I absolutely would not use if they are bowed. You can work around just about any other piece with a bow but there would be no guarantees with a bowed spar. That would be my advice but don't forget that advice is worth exactly what you pay for it.

mcarleno

Warp Spars = Sorrow

Looks like a couple of bucks worth from the LHS. Mine carries Sig and Midwest Balsa (mostly Sig). My LHS the Midwest is great for spars -- it seems to be a little more dense (a little more expensive too 10%). Beside this way you get to pick the best, straightest ones, you'll be happy you did.

My first kit was a Super Sportster that had a warped spar and a warped leading edge. I kepted it pinned down until I got the D-tube built. I looked good, but I had a 1/8" offset on my ailerons and she spun like a pig to the starboard side. I took care of that by doing a kart-wheel at 50 mph and Karate Chopped that right wing into million (they all appeared to be straight) pieces.

10 New ribs from Great Planes, a couple of new spars from the LHS a new right wing (+ a little carbon fibre and epoxy ... well a lot OK) and she fly's perfectly now.

joeydonutz

Thanks, guys. I figured that I would probably have to buy new spars but I also know that one can do some weird things with wood as far as making it fit. But yeah, in a case like this better to not have any doubts.


mcarleno-your story made me laugh. Not because of the results but just trying to imagine how a pig spins. Too funny!

Kaos Rulz

It ain't pretty.

papermache

My Feedback: (35)

go with Lightfoot. Call Sig and they'll take care of the problem. They're good about that kind of stuff.

papermache

britbrat

When you get your new spars, it would also be a usefull thing to sheet the LE's of the wing up to the main spar. The small additional weight penalty is offset by a slightly better shape & much greater strength. Even 1/32 balsa sheet adds substantial strength.

RCVFR

My Feedback: (7)

Doing so will redesign the wing. The original design. open bay with spanwise stringers is a "turbulator" design which contributes greatly to the remarkable slow flight capability of the 4*. If you want to give up some of that flight envelope, the choice is yours.

britbrat

It does indeed re-design the wing --- and it flies better (sharper response at high speeds & less float on landing), as well as being stronger.

MinnFlyer

My Feedback: (4)

I wouldn't bother Sig. Between the phone call, and the postage and the TIME spent waiting for a replacement to arrive, you could have the wing finished.

Just lay the spar on a workbench and place a nail at both ends.

Then bend the spar against the nails till it's bent slightly the other way.

Add another nail to the center to hold it there, and lay some weights on it to hold it flat against the table.

Let it sit overnight (You could dampen it if you like, but I would try it dry first)

By morning it should be fine. Whatever minor bow might still be there, will build out.

joeydonutz

Thanks, guys. All great advice with options, too! I don't think I have the patience to wait for new spars from Sig. I will try to reshape as per MinnFlyer (great graphics!) and if not then it's off to the lhs.

I also like the idea of sheeting the LE up to the main spar and will do so. Thanks much!