CUTTING Ribs  
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All Forums >> RC Airplanes >> Scratch Building, Aircraft Design, 3D/CAD >> CUTTING Ribs
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CUTTING Ribs - 6/2/2008 10:40:50 PM   
WhiteRook



Posts: 863
Joined: 11/3/2002
From: westbrook, ME, USA
Status: offline 		IS the stack method the best , or is there a better way?

also how much can you be out without effecting the airfoil?

thanks RCU
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RE: CUTTING Ribs - 6/2/2008 11:16:55 PM   
IL2windhawk



Posts: 387
Joined: 4/7/2006
From: Ogden, UT, USA
Status: offline 		Through my small experience at making ribs, I think the stack method works about as well as anything else possibly could. As long as the ribs don't shift or move while you cut, you should easily be able to get them close enough for aerodynamic consistency.

I used an exacto knife to cut each rib to the approximate shape, with extra material. Then I used two C-clamps to pinch the balsa between the plywood templates and a block sander to do the rest. Then I used jeweler's files to cut the spar slots, etc.

Hope all this helps.

< Message edited by IL2windhawk -- 6/2/2008 11:18:05 PM >

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RE: CUTTING Ribs - 6/3/2008 12:12:34 AM   
flipstart


 

Posts: 653
Joined: 8/14/2003
From: Andersonville, TN, USA
Status: online 		I cut two rib patterns from hard ply and drill 2 holes, usually 1/4", in rib patterns. Stack all rough cut ribs together with patterns top and bottom. Drill through entire stack and clamp together with 2 -1/4" bolts and nuts. Tighten enough that no shifting is possible. Then sand down until all ribs are flush with both patterns without cutting into the patterns. I end up just lightly sanding on my belt sander with the sander turned off to get a flat surface across both patterns.
I make my tapered wing ribs the same way. One tip is to coat the edge of the rib patterns with black magic marker-this will let you know when you get down to pattern. I have done as many as 14 ribs with no problem.

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RE: CUTTING Ribs - 6/3/2008 1:06:46 AM   
WhiteRook



Posts: 863
Joined: 11/3/2002
From: westbrook, ME, USA
Status: offline 		flip, thats a great way to stop them from shifting, since i'm doing a tapered wing with a non tapered center section , i'll only have 6 center ribs to make alike , the rest will be in twos

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RE: CUTTING Ribs - 6/4/2008 11:56:27 AM   
pahtreek



Posts: 122
Joined: 4/21/2002
From: Woodstock, GA, USA
Status: offline 		I have been working on a 1/3 scale biplane, it has 52 ribs top and about that on the bottom. For the ribs, I used an old set of .60 size plans blown up, and the rib profiles overlapped on the plans, so I could not cut them out and glue the profiles to the wood, so I had to place the wood under the plans, and with a pin, dot dot dot along the lines of each rib and then "connect the dots" with a pen to scroll saw cut them out. Then I used my disk/belt sander to sand down to the line. Now THAT was a lot of work.

I have always scroll saw cut each rib and used my sander to sand down to the lines. This is a quick and easy process. But I only do 2 at a time. Cut out the paper rib profiles from the plans, use 3m spray to "glue" the paper to the wood (3m a 2nd piece of wood to the back for the left and right rib to be cut together), then use a scroll saw to rough cut them out (except for where the top and bottom spars go in to the ribs...cut that exact) Then just push it against your sander and you'll be done in no time. I always scroll saw out two large ovals inside the ribs to save weight. As long as you leave 3 times the wood thickness along the edges, everything else is dead weight.
Everytime I tried to "stack" ribs, any more than two (one left side and one right side rib), the sander would always put a little bevel so that the top rib was sanded more than the bottom.
If you dont want to cut up your plans, my friend swears by a method where he places the plans on the wood, ink facing the wood, and Irons the plans. The ink gets transferred to the wood. I will probably try that next time I build a plane.
Good luck,
Patrick
www.putfile.com/pahtreek


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RE: CUTTING Ribs - 6/5/2008 10:24:24 AM   
excaliburmaxi


 

Posts: 17
Joined: 3/28/2007
From: Villa Adriana, ITALY
Status: offline 		I've tried the method of ironing the plans on the wood and it work. You have 2 option: 1) if you use a cad program when you print pay attention the printer is a TONER printer or you have to make some photocopies and then put the paper ink facing the wood and with iron set to cotton transfer the toner to the wood. use a lot of perssure and do rapidly. if the wood star to deform when it cool it retur in shape. I suggest sone experiment on a little piece of wood. Pay attention the photocopier some time deform the design. Before cutting check against the original. The best way is Cad program toner printer and then transfer. regards Max.

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RE: CUTTING Ribs - 6/6/2008 2:08:04 PM   
vicman



Posts: 6026
Joined: 12/8/2002
From: Valdese, NC, USA
Status: offline 		Similar to Flipstart, I will cut at least two at a time on the bandsaw leaving extra. Then I stack them all up and clamp the whole lot of them (tapered too) I usually fit a short piece of spar material in the slots before sanding this also keeps alignment for when I take the clamp off. Sand to shape and go to gluing. It's a lot easier than you might think.


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RE: CUTTING Ribs - 6/6/2008 2:52:57 PM   
WacoNut



Posts: 1438
Joined: 1/1/2005
From: Blanchester, OH, USA
Status: offline 		I use 3M spray adhesive to stick my rib pattern to the wood and I use the adhesive to stack up to 6 ribs at a time. I run the stach through my band saw leaving approx. 1/16" then finish them off with my disc sander. I always make numerous copies of my rib templates.
Anthony

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RE: CUTTING Ribs - 6/6/2008 3:40:37 PM   
CoosBayLumber


 

Posts: 2914
Joined: 1/20/2002
From: San Bernardino Calif
Status: offline 		Going back to original question....

The stacking method may be fast, but it leads to excessive taper in the edges to each part. An often slots for spars are not accurate then too.


Wm.


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RE: CUTTING Ribs - 6/6/2008 3:55:09 PM   
WacoNut



Posts: 1438
Joined: 1/1/2005
From: Blanchester, OH, USA
Status: offline
quote:

ORIGINAL: CoosBayLumber

Going back to original question....

The stacking method may be fast, but it leads to excessive taper in the edges to each part. An often slots for spars are not accurate then too.


Wm.

If you take the time to tune your band saw and disc sander to make sure everything is square then taper is no longer an issue. I have not had a problem with spar notches or taper in the rib surfaces at all. If you are stacking ribs for a tapered wing then you will have taper in the rib edges. I only stack ribs that are exactly the same.
Anthony

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