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Wittman D-12 Bonzo


cymaz
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Jon

What Scale was your build? You’ve read my mind! I too was thinking of reducing the number of wing ribs, easy to do on the computer. 

We’ve drawn  1/3 scale, although it would be feasible to do 1/2 scale given the size.

At 1/3 scale the wing panels are 30” but we’ve drawn in 21 ribs!

What rib spacing could I get away with based on other wings ( well proven plans, artf etc). It is designed so that the ribs slot down over the front and rear spars. There are a couple of locating wing tubes as well.

If you can see the plan ok, I’ve been lucky enough to get copies of the original plans, signed off by Wittman, when the plane was restored in the mid 80’s.

Best wishes ...Pete

B8AE1E14-3C16-455B-98C8-A03D163ACAF3.png

8CE4D38E-43F8-44A6-8A15-2336A9A93783.jpeg

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6 hours ago, cymaz said:

Jon

What Scale was your build? You’ve read my mind! I too was thinking of reducing the number of wing ribs, easy to do on the computer. 

We’ve drawn  1/3 scale, although it would be feasible to do 1/2 scale given the size.

At 1/3 scale the wing panels are 30” but we’ve drawn in 21 ribs!

What rib spacing could I get away with based on other wings ( well proven plans, artf etc). It is designed so that the ribs slot down over the front and rear spars. There are a couple of locating wing tubes as well.

If you can see the plan ok, I’ve been lucky enough to get copies of the original plans, signed off by Wittman, when the plane was restored in the mid 80’s.

Best wishes ...Pete

B8AE1E14-3C16-455B-98C8-A03D163ACAF3.png

8CE4D38E-43F8-44A6-8A15-2336A9A93783.jpeg

Pete,

 

Signed plans!   Wow, that is really cool!

 

I built Chief OshKosh to 1/4 scale so the 16ft wingspan became a 4ft scale model.   Over the years, Wittman kept reducing the wingspan until is was 12ft in 1937 when it crashed (can you say “not enough lift!”).   Undeterred, Wittman took the Chief’s wreckage and created another successful pylon racer called Buster.

 

To answer your question if you do 1/3rd scale, you probably only need 1/4 of the ribs structurally, but one of the characteristics of Bonzo’s wings is the ridiculous number of ribs.

 

As a result, you could consider reducing the number of ribs by 1/3 since the spacing would still look tight, laser or CNC cut from 1/16” balsa sheet with lightening holes, and wing tube holes.   

 

Include 1/8” or 3/32” ply ribs at connection points.   Rather than a wing tube, have you considered carbon fibre tubes?   Super light.   The Chief OshKosh wings is way more rigid that necessary, so I would reduce the structure if I built another.  Shockingly the 4ft wing weighed 1lb….I am sure I could build another doing in under 3/4lb with no struc compromise.

 

The pic of my over structured Chief OshKosh wing below should be significantly reduced.   Really only needed 1 carbon fibre tube with one built up spar.   The leading and trailing edges provide a lot of stiffness as well.  I would have more lightening holes cut too.

 

Enjoy your build.

444D4F73-B257-4CE2-BEBD-F30CABED6140.jpeg

Edited by Jon Harper
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