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Old Feb 28, 2012, 05:26 PM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
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Wing Structure Question

I am in the middle of an 80" DC-6B scratch build and the wing structure seems to have a weakness between the inboard nacelles and the center where it joins the fuse. The rest of the wing seems stiff enough especially once covering will go on but I am worried about the center section since at this point before covering it seems to flexible (torsional strength...twisting). All the weight of the nacelles, motors etc outboard of this area seem to be putting quite a load on the inboard sections.

I am thinking of adding some shear webs to the other spars in that section and/or sheeting these areas. Just looking for advice, any thoughts?

Thanks,

Dave

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Old Feb 29, 2012, 11:47 AM
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Herman Munster's Avatar
United States, Mt, Libby
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I think sheeting both the top and bottom in that area would help significantly. I take it you have shear webs on the main spar.
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Old Feb 29, 2012, 01:04 PM
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how much's Avatar
United Kingdom, England, Wigan
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Dave
just been looking through your build log http://www.rcgroups.com/forums/showthread.php?t=1597461

very nice work!

i noticed you built the wing in two halfs... did you put a ply brace accross the centre vertical join of the main spar? doesnt need a lot... just a 1/32" ply plate accross the join on one side

i would definately sheet the centre section in 1/16" balsa top and bottom too

i will be doing the wing next on my balsa sunderland

David
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Old Feb 29, 2012, 01:16 PM
ich bauen groß modell flugzeug
Keenan smith's Avatar
United Kingdom, London
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Carbon fibre!
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Old Feb 29, 2012, 03:01 PM
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United States, NC, Rutherfordton
Joined Jan 2002
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Sheeting & cap strips will help tie the structure together.

Matt
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Old Feb 29, 2012, 03:24 PM
ich bauen groß modell flugzeug
Keenan smith's Avatar
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carbon fibre!
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Old Feb 29, 2012, 06:54 PM
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United States, FL, North Port
Joined Mar 2004
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I'd suggest putting the top or bottom sheeting on first and then re-examining your original concern. The sheeting will add a substantial amount of torsional rigidity.

If after adding one side of the sheeting, you find that it still isn't torsionally stiff enough for you, you can add ribs Diagonally between the wing ribs to help as well.
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Old Feb 29, 2012, 11:31 PM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
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Quote:
Originally Posted by how much View Post
Dave
just been looking through your build log http://www.rcgroups.com/forums/showthread.php?t=1597461

very nice work!

i noticed you built the wing in two halfs... did you put a ply brace accross the centre vertical join of the main spar? doesnt need a lot... just a 1/32" ply plate accross the join on one side

i would definately sheet the centre section in 1/16" balsa top and bottom too

i will be doing the wing next on my balsa sunderland

David

David,

the main spar consists of shear web with a top and bottom spar of a spruce like wood (paulownia wood). The remaining spars are just 3/16" paulownia top and bottom. I was thinking about adding some reinforcement plates on either side of the spar in the center section.

Thanks,

Dave
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Old Feb 29, 2012, 11:34 PM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
2,797 Posts
Thanks all for the advice,

I had not thought much about carbon fiber but I had seriously considered more shear webbing and some limited sheeting. This was designed to be an 80" plane that was to be under 3 to 3.5 lbs. so it is a game between strength and weight. I still feel like I will make the goal and when the wing is bolted on the center section under the fuse will be much stiffer. It is a bit of a guessing game trying to figure out how much to add and how much the fuse and covering will help as well.

Dave
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