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Wing struts

Old 05-30-2008, 12:06 PM
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Default Wing struts

In the tradition of spad building, how would you build wing struts for a large 96" wing span coroplast wing? A mistake was made in building the main spar too weak and now the wing flexes in flight especially when windy. To avoid building a new wing, I want to add struts to the existing wing.
Old 05-30-2008, 01:21 PM
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rrh
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Default RE: Wing spars



I have had great results on big wings with the I-beam spar. You can kind of see the end of it in this pic. Split a yardstick and glue the halves to the top and bottom of another and it really adds a lot of strength. I think the pic is a 72" wing but I've built them up to 96" using this spar. Stagger all your joints. Glue 4" or so reinforcement pieces on both sides of the main spar splices.
Old 05-30-2008, 03:40 PM
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Default RE: Wing spars



Thanks Randy:

That's what I did on the original wing which I totally overbuilt and rejected because of its weight. I underbuilt the second wing which is causing my problem.

Clarence

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Old 05-30-2008, 04:38 PM
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rrh
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Default RE: Wing spars

Find that happy medium and you'll be good
Old 05-30-2008, 07:24 PM
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Default RE: Wing spars

Billbabe
My big Cub has a 110" span (96 + two 7" wing tips) and it's good and stiff. I cut spars from a dead straight, knot free, bone dry, spruce 2 x 4. There's one piece of 4mm on the bottom and two pieces of 2mm on top, 1" overlap at the front with a balsa leading edge. The main spars are 1 1/2" high, rear spar is 3/4" high, all are just under 1/4" wide. I hot glued spacers to make a ladder so it all held together during layup....then I punched the spacers (ribs) out with a long stick. Wing weighs 5 lbs. and unfortunately is in one piece so hauling is a pain (fits in my Matrix though!). Lots of work but a rigid coro monster wing is doable.
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Old 05-31-2008, 07:22 AM
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Default RE: Wing spars

Gary:

How do you attach your struts to your wing and fuselage?

Clarence
Old 05-31-2008, 10:26 AM
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Default RE: Wing spars

This has been a very confusing post as I meant to say wing struts instead of wing spars throughout.

Clarence
Old 05-31-2008, 03:19 PM
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rrh
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Default RE: Wing struts

hmmm struts, never attempted em. How bout a mast in the middle with flying wires like an Eindecker or are you going for the Cub look?
Old 05-31-2008, 04:08 PM
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Default RE: Wing struts

Clarence
The struts are bolted to 1/16" thick aluminum plates which are screwed into the bottom of the fuselage and are bent to match the angle of the struts. The struts are attached to the bottom of the wing via 3/32 or 1/8" thick aluminum brackets. These brackets are 1/4" wide and 1/2" long drilled with 2, 1/8" holes. The brackets are anchored inside the 4mm coroplast with 1/8" piano wire which run through the flutes chordwise. The stress is transfered over a big area of coroplast and will never tear out. That's the way I do it on the Cub (they're made of 6mm coro and aren't funtional).
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Old 06-10-2008, 11:19 AM
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Default RE: Wing spars

Bent,

Do you have plans and/or construction photos of that plane? I woudl love to build one like it. That plane is really well made and looks great!

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