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Old Feb 12, 2014, 01:01 PM
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United States, WI, Rib Lake
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Gull wing, Compufoil, ribs at the "bend"?

I have been working with the trial version of Compufoil.

I generated the wing panels for a gull wing (as on the Corsair).

Is there a way to generate a special rib profile, for ribs to be installed at the "bend" where the two panels join?

Assuming, for example, a 30 degree angle, between the two wing panels, a rib placed at the mating ends of the two panels, would be angled 15 degrees from the vertical. These ribs, because they are "tilted" would need a different profile in order to align with the profile of the other ribs.

Indeed, you would like to have the program generate a special rib profile at any time one panel has a dihedral different from an adjoining panel.

How do you handle this?
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Old Feb 12, 2014, 02:49 PM
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all i do is add balsa all round the two rib if you are going to have two wings panels that join then put a spacer in between the two ribs then glue them in place then sand the balsa using flat long sanding block and flowing along the ribs on one panel then the other when you are happy with them i like to put lots of super glue on the balsa first then i use a hacksaw blade to cut the two joining ribs apart
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Old Feb 20, 2014, 09:44 AM
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Or, make those inner ribs from a much thicker wood, like 1/4 or thicker balsa. Then sand in the angle like above. This also allows a radius to the curve, since full size didn't have really sharp bend on the underside.

But, if you want to keep it really light then, yes, you do have to change the size of the rib a bit. IIRC all it takes is "stretching" it vertically. Use a trig function to find out how much. For 15deg it isn't much.
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Old Feb 20, 2014, 10:14 AM
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Roger that, but what does the abbreviation IIRC mean?

Compufoil rep has advised me that their program does not generate a special rib shape. They suggests methods that have been suggested here.

I am very impressed with what Compufoil can do. My initial impression is that it will save me hours of work in creating the wing including the files needed to laser cut parts.
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Old Feb 20, 2014, 12:24 PM
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I have CompuFoil but I havent tried anything like this. Im wondering if you could add dihedral to create the "gull" section and let CompuFoil calculate the rib shape. I think you might be able to add a separate dihedral for each panel you create in CompuFoil.
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Old Feb 20, 2014, 12:44 PM
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it is not that hard to do allthou building a gull wing and cuting all the parts is a lot of work with out computofil
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Old Feb 20, 2014, 05:19 PM
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Ok.. so I jumped on CompuFoil to double check and drew a wing real quick to illustrate. I think this might be what you're looking for. I created a gull section using two panels. I added negative dihedral to get the panel to point down. In the screen shot example I used negative 10 degrees. I then created a second panel and added positive 20 degrees to counteract the original negative 10 and then add some additional dihedral. I used the numbers but you can try different ones to suit your project. Hope this helps.
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Old Feb 20, 2014, 08:15 PM
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Quote:
Originally Posted by dpot View Post
it is not that hard to do allthou building a gull wing and cuting all the parts is a lot of work with out computofil
Dare I say "tres bien"?. That is an absolutely beautiful airplane.
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Old Feb 20, 2014, 08:19 PM
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Quote:
Originally Posted by funkworks View Post
Ok.. so I jumped on CompuFoil to double check and drew a wing real quick to illustrate. I think this might be what you're looking for. I created a gull section using two panels. I added negative dihedral to get the panel to point down. In the screen shot example I used negative 10 degrees. I then created a second panel and added positive 20 degrees to counteract the original negative 10 and then add some additional dihedral. I used the numbers but you can try different ones to suit your project. Hope this helps.

Oh funkworks, that is way beyond my paygrade.
I guess what you have done is to put all the ribs an angle.
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Old Feb 20, 2014, 08:52 PM
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IIRC is If I Remember Correctly
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Old Mar 04, 2014, 03:48 PM
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Take also a look at devWing, it takes care automatically to generate the right angled ribs where the panels are joining
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Old Mar 04, 2014, 09:26 PM
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Grazie, Durone!
I will look into that.
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Old Mar 04, 2014, 09:27 PM
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does that program generate a solid model like an .igs, .stp , etc.? If it does my CAD software can slice through any portion of the airfoil, then "extract edges" to create a wireframe profile for cutting
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Old Mar 07, 2014, 12:21 AM
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Bill, I don't know. I know very little about CAD.
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Old Mar 08, 2014, 05:15 PM
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Quote:
Originally Posted by bill clark View Post
does that program generate a solid model like an .igs, .stp , etc.? If it does my CAD software can slice through any portion of the airfoil, then "extract edges" to create a wireframe profile for cutting
Bill, the Compufoil program only exports screen shots while in the 3d view, it generates all the ribs for single / multipanel ribs, just as GoNavy suggested, 3d section is a preview style system, for the 2d parts.

GoNavy, your inclined rib, don't know, I think you would have to generate that rib separately, but ask the support section in Compufoil, Eric has been very helpful for a long time on my part.
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