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Author Topic: Simple method of fabricating diagonal ribs!  (Read 591 times)
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PantherM100
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« on: October 25, 2020, 04:59:25 PM »

Hi Guys and Girls:
I have been building model airplanes
Pretty much my whole life.  Lately, I’ve
Been drawn to the P30 class of rubber
Powered free flight.  One problem that I
Encountered is fabrication of diagonal wing
And stab ribs.  Are there any 21 century methods
Fabrication?  I guess CAD would be one way (Draw
The 2D profile with spar grooves, and then
Give a thickness, then change the view port
And rotate the axis, the print the resultant profile
and Voila!, just transfer to sheet balsa and start
Cutting.  Or, the and cut and fit trial and fit is the other.  Also the
Spars intersect the ribs at a complementary
Angle.
Sincerely,
Jon B. Shereshaw
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lincoln
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« Reply #1 on: October 25, 2020, 06:11:48 PM »

I don't know if P-30 airfoils would be thick enough, but one could do regular ribs with triangular diagonal ribs in between. The diagonals might only go back to the spar, and wouldn't actually touch the covering, or at least not on top. As seen in the Chrysalis 2M RC glider.
 
If you don't have CAD, you might persuade me to do it for one model. At the ènds, you'd have to decide whether to match the longer side and trim or match the shorter side and fill. Plus a similar decision for spar slots.

Maybe you could make a jig to cut the ends of the ribs at the right angle.
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Starduster
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« Reply #2 on: October 25, 2020, 06:58:27 PM »

I dunno, but for a P-30 size wing I'd just use a F1B stab method:

cut 1/32 (or 1/16) sheet a constant width of the highest point of the airfoil (for example 1/16 X 3/8 X 36) and just cut the lengths and glue them in place. once dry, you can rough-trim from the high-point down to the trailing edge. then use a long sanding block to sand down to the existing ribs.

Easy peasey.
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OZPAF
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« Reply #3 on: October 25, 2020, 09:23:03 PM »

Agree with SD. I have used the long sanding block or trammel to sand the diagonal ribs to shape and it is quick, easy and accurate. The end ribs were cut to the airfoil shape, protected with a layer of masking tape (also a layer on the same section of the sanding block) and then used as a guide for the sanding block.

I also made a quick to produce the correct bevel on the ends of the ribs.

John
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PB_guy
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« Reply #4 on: October 25, 2020, 11:37:41 PM »

This is another way of making 'diagonal' ribs out of square stock, with the top 'rib' running in the opposite direction to the bottom 'rib'. When covered, it makes a very strong wing.
ian
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Re: Simple method of fabricating diagonal ribs!
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PantherM100
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« Reply #5 on: November 23, 2020, 08:13:35 PM »

Hi Guys:
Okay, that sounds like a plan,  however,  what’s your
Preferred method of fabrication of Diagonal
Undercambered wings?  Build it upside down with
Tabs locating the ribs and lower spars in the correct location.
And then using a longish formed sanding block to form the
Undercambered profile. 
Thanks in advance for your help...
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Starduster
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« Reply #6 on: November 23, 2020, 08:20:08 PM »

Hi Guys:
Okay, that sounds like a plan,  however,  what’s your
Preferred method of fabrication of Diagonal
Undercambered wings?  Build it upside down with
Tabs locating the ribs and lower spars in the correct location.
And then using a longish formed sanding block to form the
Undercambered profile. 
Thanks in advance for your help...

Two words: 3d CAD
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