wing bow

[Simon Williams 2]

Hi there. I mentioned in the newbie section I was rebuilding an old kit from scratch. Ive just completed the wing this week but ive noticed there is a definate curve in the left wing near the root. Not a twist but the wing certainly looks bowed. Will this have a severe effect on flight or will it just alter the angle of deheidral slightly, and can it be trimmed out if need be? Thanks.

Edited By Simon Williams 2 on 02/07/2011 07:41:39

[Martin Harris - Moderator]

Without a picture it isn't possible to give a definite answer but the probability is that it would be trimmable.

 

It's surprising what you can get away with on a model and if it's a straight bow (if you see what I mean) the effects should be more visual than aerodynamic but try and assess whether the cause of the bow would have any effect on the strength of this very highly stressed area. A clubmate built a DH61 with a wing twisted like a propeller but with a large amount of aileron offset when I test flew it - and even more after the flight - it's flown happily for the last 7 or 8 years.

 

Even full size can be less than perfect. I used to have a share in a vintage Rhonbussard glider that had been refused a German C of A due to a 1 degree twist in a rebuilt wing - the more flexible British Gliding Association (who administered gliding matters in a similar manner to the LMA although European legislation is changing this) passed it for flight with a pair of aluminium trim tabs and it flew delightfully.

 

 

[Peter Miller]

Martin.

 

Did you know that Slingsby built a glider (can't remember which) IT was a pig to fly, really nasty. Then they found that they had built in washin enstead of washout. I believe that it is still flying and still a pig.

 

Simon. A straight bow without twist will not be a problem. If it has a twist it may be possible to get it out. Or possibly add the same twist to the oposite wing BUT it must twist the right way. The trailing edge should rise towards the tip, That si washout and prevents tip stalling. If the trailing edge goes down towards the tip the wing will tip stall.

 

Hold the wing up with the trailing edge in line with your eye and your eye in the centre of the wing. Without moving anything sight along the wing and you will see which way it is twisted or if it is straight.

[Simon Williams 2]

Thanks fellas. Ive covered the wing regardless and now found there is a slight twist in right hand wing! Destructions said this may occour during covering and shows how to remove twist with iron but as it is slight iI may just try it and see rather than risk making it worse.

 

Thanks for the advise. I think I need to be a bit more patient with my builds, or else go ARTF. Cheers

[Peter Miller]

Remove that twist. You should be able to gently twist the wing while heating. Keep checking. If you know the wings are straight that is one thing less to worry about.

[Alan Cantwell]

do you have access to a wing incidence meter? like the robart one? well worth an investment ?

totally agree, remove the twist if possible, there are various ways of doing it, some more extreme than others, whats the model?

[Simon Williams 2]

banana 2000. Tissian Haifa. I think its a company from Israel.

 

[Ben B]

A kind of fitting name Paint it yellow and black and say you did it on purpose

[Peter Miller]

Ah yes. The Tissan Haifa kits are probably the best ever made. Everything fits to perfection. On the Condor glider they even chamfer the rear fuselage formers to allow for the tapered plan view. On that model the piece of sheet that covers the top of the fuselage behind the wing has a rebate so that half the thickness goes inside the sides and the other half extends to the outside of the sides. The wing spar webs are cut to the taper on the wing and the fits are so perfect that you can assemble to wing and move it round without and glue.

 

The last Banana also came with everything in the kit, even a building board, plastic gloves and pins and the engine.

 

That wing should respond to twisting and applying heat.

 

I had the pleasure of reviewing most of the Tissan Haifa range.

Edited By Peter Miller on 04/07/2011 09:11:14

[Simon Williams 2]

Afraid I never got to fly the original kit. Had it years ago and threw it away thinking "Im never going to get into that again". I know! Im kicking myself now!

Found the plans and instructions at my mums house recently and thought it would get me into the park behind my house as my other model is a precedent flyboy and a bit too big to fly there, especialy with my small experience!

 

So I dont think mine will be so well put together. In fact Im expecting it to disintergrate on 1st landing attempt .

[Simon Williams 2]

Yellow and black Ben??

[Simon Williams 2]

Ok. Ive got rid of that twist. It was easier than I thought. Just weighed wing down on flat surface and with iron on low heat ironed out wrinkles made by the twist being straightend. It still wasnt quite right so I did it again proping up wing tip at trailing edge with a small wooden block, hey presto straight wing!

Cheers guys.

Edited By Simon Williams 2 on 17/07/2011 08:39:41

[John Olsen 1]

Keep an eye on it as it may continue to move for a bit...it will probably stabilise given time, eg just repeat the treatment as needed.

 

One thing I have learned is to try to avoid building stresses into things. For instance on a wing with an elliptical leading edge to the tailplane, I originally followed the plan and just sprang the balsa to the shape. That tailplane always wanted to move. On a recent rebuild I replaced the leading edge with a laminated one, eg 6 layers of 1/16 instead of one piece of 3/8 square. It hasn't flown yet, but indications so far are that it is much more stable, eg it didn't go out of shape as soon as it was covered!

 

regards

John