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Log Entries for Ribs

Log Entry Date: Jul 31, 2012


Flange Block Part 1
Here is my step by step approach to flanging ribs. It's modified from Eric Newton's wing's manual and includes a little more info on exactly how to build the form blocks.

Step 1: You'll need two nose rib forms cut from MDF. Unlike the originals you used to bend the nose ribs, these don't have to be perfectly shaped. I rough cut them with a jig saw. The reason you don't want to simply re-use your original nose block forms is because if you have any imperfections in your lightening holes they will crack when you press the flanges and you'll need to make a replacement nose rib. That's an easy thing if you still have the original forms laying around.

Step 2: Lay your bent aluminum nose rib over one of the MDF nose rib forms and trace the lightening holes.

Step 3: Since you want a 3/8" flange on the nose ribs per the plans you need to put some marks 3/8" outside the circle you traced in step 2.

Step 4: Set up your drill press with a circle cutter so it will cut to the marks you made in step 3. Remember you're measuring to the OUTSIDE of the cutting blade.

Step 5: Clamp both nose rib forms together and make sure the edges are all flush. You will drill the top nose rib first, but drill as far as possible so you create an alignment hole in the second nose rib form. This will insure that the holes in both forms are perfectly aligned.

Step 6: Cut the flanging hole using the circle cutter. When the hole is cut you should be able to lay the aluminum back on the block and see 3/8" of aluminum all the way around the hole.

Step 7: After drilling the first form block as far as you can, un clamp everything remove the scrap plug and the top nose rib form block, realign the bottom form block using the centered hole created from drilling the top block and MAKE SURE you've got some scrap wood under that second form block or your circle cutter will hit the drill press table.

Step 8: Save the plugs you drilled for later. You can use one of them for the completed plug, but you can't simply make your plug out of these because they're too small and they don't work (trust me).

Step 9: Take the nose rib form blocks and use the holes in them as a template for the flanging plugs. Trace a circle inside each hole in the form block (big and small) onto another piece of MDF. These circles will become your flanging plugs.

Step 10: Back to the circle cutter, set it up to cut out the circle you traced from the last step. Ideally the plug needs to be 1/16" smaller than the holes cut in the form block, so if you set it up so your cutting away the pencil mark you traced onto the MDF you'll be in good shape. MEASURE THREE TIMES and get it right. Again remember you're measuring to the inside of the cutting tool.

Step 11: If your circle cutter is like mine you'll end up with a circular plug that has a little flange on it due to the shape of the cutting knife on the circle cutter. Screw the plug into a sawhorse or other sturdy piece of wood with this flange up.

Step 12: Using a 45 degree chamfer bit route all the way around the plug, taking off the little lip left by the circle cutter and producing an angled plug.

Step 13: Nail the plug from step 12 to one of the scrap plugs from step 8 to create the finished plug.

Now you're ready to start flanging. I did a test and it worked great. See tomorrow's entry for the flanging instructions along with pictures of flanged ribs.
Nose rib form block with flanging holes cut and the finished flanging plug. The plug is two pieces of MDF. The top piece is routed at 45 degrees and will be used to flange the aluminum. The bottom piece is just nailed on and used to give enough clearance when pressing to make the flange.
Flanging plug before routing. Notice the orientation.
Flanging plug after routing.

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