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making ribs from scratch?

Old 02-11-2004, 06:10 PM
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Dago Red
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Default making ribs from scratch?

I am thinkinf of building a balsa wing for my (Top Secret) design I cant seem the get the foam to work the way I want it to. My question is, how do i cut ribs ranging in size? I need to start from a 20 inch rib to a , say 10 inch rib. Not to sure how to do this. thanks for looking and helping.
Old 02-11-2004, 06:40 PM
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Default RE: making ribs from scratch?

A commone way is to clamp a stack of rectangular slabs between two plywood templates and then carve it all to look like a very short foam wing blank. The taper sizes being set by the two templates. But this doesnt work well when the taper is so radical. The edges of the ribs are angled and the "true" size is masked by the angles.

I think it may be time for you to learn how to use CAD software. With that you can bring in your DXF rib file and then cut and paste as many as you require. Just do a chart of the scale sizes you need for each rib position and reduce each rib copy by that much until you have a screen full of the tapered ribs. Number them so you don't loose track of them and then draw a 4 inch wide "sheet of balsa" and lay the ribs over that in the best layout for fit. Print that and attach it to some sheet balsa using Post It glue stick or other temporary stickum. Cut out the ribs from there.
Old 02-11-2004, 07:59 PM
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RCPAUL
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Default RE: making ribs from scratch?

Dago

Even if you had each rib laid out (via CAD or other means), the stacking balsa blanks between plywood templates is both easy and fast. When you cut individual ribs, they never come out just the way you want them.

RCPAUL
Old 02-11-2004, 09:32 PM
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Default RE: making ribs from scratch?

Tell me what airfoil you want to use, rib spacing, total number of ribs, tip chord, root chord and I'll CAD it up for you.

I'll let you size and place spars though. A guy has to have his limits.
Old 02-11-2004, 10:35 PM
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aimmaintenance
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Default RE: making ribs from scratch?

I'm lookin at plans currently that has ribs that are curved sticks so to speak.
The ribs are 1/4" high made of 1/8" balsa and are the profile of the fully symetrical airfoil.
2 piece ribs. The leading edges are set the same and the trailing edge is criss crossed to achieve the cord that you want along the span.
Imagine a full airfoil rib with the center cut out leaving 1/4" edges all around. cut this in half cordwise and then criss cross the trailing edge to achieve the cord ya want.
Is this what your askin?
Old 02-11-2004, 10:48 PM
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b17mik
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Default RE: making ribs from scratch?

Go to www.compufoil.com Its all you need to know..Its a beautiful program for design of ribs and planforms..Free trial down load and it is worth every penny for the price for the full program..If you can think in your head it is easy to get it on your computer..Michael
Old 02-12-2004, 09:16 AM
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CafeenMan
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Default RE: making ribs from scratch?

A little more detail on the sandwich method.

It is very accurate, but only if you understand how it works.

First, it only works with equally spaced ribs. Second, as has been mentioned, it puts an extreme taper on the ribs. Do the left and right set and then put the pairs of ribs together. Sand them to the edge of the taper so that the edges are square. You sand just to the lower part of the taper.

The first and last ribs are not the root and tip ribs. To make the root and tip ribs, use the templates to cut them out directly.

It works very well, but takes a couple hours. I agree that it is generally more accurate than cutting out individual ribs. Another good thing about it is that you can interpolate between two different airfoils automatically.

BTW - if you use a wing jig and you want washout, then stack the ribs and templates together but align the tip rib on the stack at the correct angle. When you slide the ribs on the jig, the washout will be correct.

- Paul
Old 02-12-2004, 01:28 PM
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Dago Red
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Default RE: making ribs from scratch?

SeditiousCanary
Ill have to put it up on paint and psot it, the wing is like a P-51 wing, each side is 60 inchs, but will be capable to break down into 2 peices. Ill try to post it later tonight for ya. Thanks for the help guys!!!!!!
Old 02-12-2004, 01:57 PM
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Dago Red
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Default Here we go

heres what I plan for.
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Old 02-12-2004, 07:18 PM
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kdheath
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Default RE: Here we go

Looks like the aspect ratio of the outer panels is pretty high. Are you gonna be able to build in enough stiffness? How thick is the airfoil? Just curious, looks like it might become a structural issue.
Kelvin
ORIGINAL: Dago Red

heres what I plan for.
Old 02-12-2004, 09:51 PM
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SeditiousCanary
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Default RE: Here we go

Do you know:
What airfoil you want to use?
The chord is at the first 20 inch mark?
Old 02-12-2004, 11:43 PM
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Dago Red
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Default RE: making ribs from scratch?

Well, Im going to redesing the wing to a more scale looking, so bear with me whileI redo the wing, sorry.

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