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3 Piece Box Spar Wing Modification For Single Seater SSDR

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buckie555

Member
Joined
Oct 21, 2019
Messages
10
I'm in the process of building a wood and fabric single seater of an established design that currently has a 1 piece cantilevered wing of box spar contruction. I am keen to modify this to be a 3 piece construction with a fixed centre section and two outboard sections, each approximately 2.5m long.

I realise that I will need to do a full structural analysis of my proposed modifications, however for now I would just like to get a rough ballpark idea of how heavy these modifications are likely to be. I am building to quite tight weight requirements and want to check that it's in the realms of being feasible for my airframe weight budget.

I have looked at a few different established 3 piece wooden spar designs such as the Chilton DW1 and the Falconar F11 however they have slightly different spar construction to mine. Namely solid plank spar and split caps.

My box spar is constructed of full, constant width, caps top and bottom that taper in thickness (height) and faced on either side with a ply shear web.
To give a sense of scale the spar is approximately 75mm constant width and where I envisage the joins, the spar cap thicknesses are approximately 35mm and 30mm top and bottom respectively with a spar cross section height of 150mm.

From what I've seen externally, I believe the Colibri MB2 3 piece wing was a similar construction but I could be mistaken.

My initial thoughts are for a fairly standard arrangement of vertical straps made of 4130 or 2124, reinforcement blocks, reinforcement ply doublers, etc for both the main box spar and, to a lesser extent, the rear drag spar.

Has anyone got drawings of the MB2 wing join arrangement or for that matter any other wooden aircraft of similar spar construction to above. I have an idea of how to proceed but I would like to see a proven example before I start doing structural calcs and FEA etc.

Any guidance, insight, gotchas or pointers to resources would be very much appreciated.

Thanks, Neil
 
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