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Basic Modern Ultralight, BMU

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Protech Racing

Well-Known Member
Joined
Jul 10, 2020
Messages
441
I have started drawing my Modernized Demoiselle. BMU.. For today's market with airports and hangers getting out of hand cost wise, It has to have folding wings and fit inside of an 8.5 ft wide trailer.
So that is the first design parameter. Folding wings that nest on the rudder. A tow bar on the rudder post area. If Iget the landing gear right , it should be able to be towed under 40MPH, on it's own wheels. ( it requires the gear to be well forward ) .
I want to use the screen room rectangular and square tubing for the wing spars. That process is still in the stress test stage . I have found 2x5 050 wall ; http://americanmetals.us/wp-content/uploads/2012/02/patio_extrusion.pdf
American Metals Supply

I will add a 2x2 093 compression tube above it.,
It will have a V strut placed so that the wing swings to the rear. The main spar will have a pull down wire/strut inline with the loads .
This main spar is set at 26% chord to reduce twist , The 2x2 TE spar will be at the TE.
Foam ribs, with the 1/3 of the bays filled with foam drag plates .
The wing will use a flat bottom foil around 16%. with Gurney flap and tip plates. Vortex generators of course. This is due to the wing being a little small at 24 x4. At the low end of the density value( 4.6) for me . It should fly at right around 32-34MPH at 420#
The spoilerons will be spar mounted at 26% , if the model likes them there. If not , they may turn into one way flaps, TE mounted.

The fuse and tail will be 4130 5/8 and 1/2 round. The engine mount/ wing mount keel is 1.5 065 .
It will have about 30 HP 2 stroke to start with and I expect to test the small block Twin or the big single 4 stroke .. The weights are similar.
The wing will have a few mounting points for easy balance changes (to accommodate different engines).
I expect it to weigh around 230# with 96 Sqft. If it is too dense I will build a longer wing. The 96 is a known good value but a little fast .
 
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