Flexing wings

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Andy Wallace
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Joined: 05 Sep 2017, 13:11
Location: COLERAINE Northern Ireland

Flexing wings

Post by Andy Wallace » 26 May 2019, 17:27

Recently I was given this scale Capstan that was scratched built by a good friend of mine about 20 years ago
Today I flew it off our only westerly facing slope
I was amazed that it flew straight out of my hands but I soon noticed that the wings were starting to flap like a seagull
The main wing joiner is a 15mm steel bar and brass box
How do I stop the wing flexing so much
Thanks
Andrew
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B Sharp
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Location: Perthshire

Re: Flexing wings

Post by B Sharp » 27 May 2019, 10:38

More info needed Andy.
Span and weight of model. Spar dimension? How much flex? ( a couple of inches each way?)
Brian. :)

Nigel Argall
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Location: Cornwall

Re: Flexing wings

Post by Nigel Argall » 27 May 2019, 19:27

Andy, I'm not sure if you are implying the wings are flexing or are actually loose and moving on the joiner?

Andy Wallace
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Joined: 05 Sep 2017, 13:11
Location: COLERAINE Northern Ireland

Re: Flexing wings

Post by Andy Wallace » 28 May 2019, 10:52

I've had a good look at the model this morning and I think the wing joiners not heavy enough for the size of the model, it's 4.2m foam wing unsure of nature of the main spar, the model weighs approximately 15lb and the wing joiner is 15mm x 2mm steel bar inside a brass box
I'm thinking of doubling up the steel bar or possibly a tube of some sort
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Peter Balcombe
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Location: Clevedon, North Somerset, U.K.

Re: Flexing wings

Post by Peter Balcombe » 28 May 2019, 11:51

Andy,
I’m sure someone else will comment, but I have an idea that this model is supposed to have a double joiner & the 15mm strip system sounds the correct size for a design of that vintage.
I have rigged a 1/4 scale Capstan in the past & I seem to think it had a double joiner, but can’t remember for sure.

Cliff Evan will have access to a drawing, so maybe he can help.

Andy Wallace
Posts: 16
Joined: 05 Sep 2017, 13:11
Location: COLERAINE Northern Ireland

Re: Flexing wings

Post by Andy Wallace » 28 May 2019, 12:35

Good man Peter thanks 👍

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Peter Balcombe
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Location: Clevedon, North Somerset, U.K.

Re: Flexing wings

Post by Peter Balcombe » 28 May 2019, 20:45

I will see if I can get a peep at the wing joiner arrangement on the one near me tomorrow evening.

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Cliff Evans
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Re: Flexing wings

Post by Cliff Evans » 28 May 2019, 21:15

Two 15mm joiners are needed. I had one a similar size. I used 2 x 15 mm joiner boxes and never had any flex problems at all. Jilles has done 1/4 scale version. Will have a look at the plan when I get home on Saturday.

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chris williams
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Location: Blandford Dorset

Re: Flexing wings

Post by chris williams » 28 May 2019, 21:44

A single 15mm joiner works well enough at 13 AUW. My Bergfalke 4's wings do flex when viewed from the air, but look normal enough from the ground.
15lbs might be pushing though...(Motley put two joiners in his version)


Jolly Roger
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Re: Flexing wings

Post by Jolly Roger » 28 May 2019, 22:49

I agree with Chris; my 13.5lb PT ASW20 loops and rolls on a single 15mm strip joiner, although I think the plan called for 2. For scale flight, I think it should be fine, providing....the wing panels are locked very firmly against the wing roots, so that flight loads result in pure up and down bending. Any fore-aft flexing hugely increases the risk of twisting and buckling - the mode of failure for a strip on its edge.

My fave attachment method is Multiplex winglocks, although I often use a 3mm tie-wrap between two cuphooks. It has a tiny bit of give and I hope would fail in a serious arrival (tho' not tested yet).

Rog

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