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Doing A redesign, please help

Old 02-01-2004, 05:04 AM
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iflyrc82
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Default Doing A redesign, please help

This is a cad drawing of a wing for a B-29. The drawing is not complete, i drew it roughly from a old set of blue prints i have, then scaled it up and made some modificaitons. Please let me know if this looks like it will be satisfactory. Also, i would like ideas on how to connect these wing halves to the fuselage. I would also like help on selecting the wood to use for the wing ribs, and maybe changes in my spar design. This wing will most likely have 2 .25 two stroke engines, or two .40 four stroke engines mounted on each side, the mounting pods are not on this drawing. The wing will also house the main landing gear whitch will be retracts, so please keep these facts in mind when giving me ideas for wood to use. Thank you every one for your help so far! Please excuse the word demo, i had to use a demo program to convert this to a jpg, if you would like the full cad file, please e-mail me at [email protected] and i will send it to you.
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Old 02-01-2004, 09:45 AM
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FHHuber
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Default RE: Doing A redesign, please help

I can't read the planned wingspan... so can't give a lot of help.

If its a light airplane... it should be OK like that with minimal wing sheeting. If going for a detailed scale model of course the wing will be fully sheeted (can't simulate a metal skin with open bay structure)

I didn't see any notation on sheer webs. You need them with that structure. (sheeted or not) Sheer webs help keep the wing from blowing up JUST from the high pressure inside and low pressure outside. (pressure on top AND bottom will be less than inside) Among other things the sheer web helps with...

Mounting... I would use the CF tube in aluminum sleeve as per a lot of Pattern planes. Wing slides on easilly. Very strong. (a bit expensive...) If its light... you can do with and aluminum tube joiner instead of the CF.
Old 02-01-2004, 11:27 AM
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Default RE: Doing A redesign, please help

There is a B-25 .dxf plan avaiable as a free download at http://perso.club-internet.fr/courbafo/Plans_e.html It's a .zip file at the bottom of the list. It's probably the wrong size but you can scale it easily enough and it should give you some ideas.

Good Luck!
Old 02-01-2004, 01:31 PM
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iflyrc82
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Default RE: Doing A redesign, please help

Here is a better view
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Old 02-01-2004, 08:30 PM
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Default RE: Doing A redesign, please help

I may be reading it wrong, but otherwise it looks too flimsy. The material sizes are more suited for rubber power than glow.


Wm.
Old 02-02-2004, 01:10 AM
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Default RE: Doing A redesign, please help

I agree. The picture is a bit small in the print and fuzzy but I think I see 1/32 sheeting. That's too light for 25's. 1/16 would be much better.

That airfoil looks like it came off the side of your shoe..... Get Profili2 at www.profili2/com and use it to save a DXF file of the Selig 4233 airfoil and use that.

The spars should not be placed like they are. Spar lines should blend with the taper of the ribs. That is if the spar is located at the 27% point of the root rib then it should be located at the same % at the tip rib. If you want to use two separate removable wings then you'll want the carry through tube(s) to be located at the spars such that the bending loads in the tubes are transffered to shear loads of the upper and lower spars. To do that the joiner tubes need to be located right between the upper and lower spars just like sailplanes do it.

Because the engines will be pulling like blazes on the mounts you'll also need some way to lock the wings to the fuselage at the trailing edge or rear spar at the flap hinge line.

You're also going to want to work your rib spacing around the placement of the engine nacelles. There should be two ribs of 3/32 plywood to carry through the engine nacelle loads to the main spar.
Old 02-02-2004, 01:17 PM
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Default RE: Doing A redesign, please help

The actual B-29 airfoil resembles a Brogan 12.
Outer side.
The construction on the plan looks suitable for a non-flying display model.
Consider where the loads will be when assembling and disassembling the model also.
Nothing worse than hearring the balsa crack when you tugging on the thing.
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Old 02-03-2004, 02:53 AM
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iflyrc82
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Default RE: Doing A redesign, please help

Ok, obviously i have things all wrong, i am working on a revised version, and i will post it soon. I thank all of you for helping me, i am somewhat of a novice as im sure you all can tell.
Old 02-03-2004, 08:50 AM
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Default RE: Doing A redesign, please help

ORIGINAL: iflyrc82

i am somewhat of a novice as im sure you all can tell.
Sorry, I didn't even read your post correctly; I saw B-25 not B-29 and posted the link to the B-25 plan.....I must be a novice reader! []

Hey, keep on plugging away; that's what's nice about CAD. You can keep on changing and changing things until you come up with something that'll work! Look around at the various downloadable CAD plans to get a feel for the structure requirements for a .40 size aircraft. That ought to get you started down the right path. Good luck and keep us posted!

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