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Log Entries for Ribs


Log Entry Date: Jan 26, 2012

Ribs

Prep aileron nose/pocket and flap nose rib bending blocks for cutting.
IMPORTANT NOTE: Sometimes you just over-think things. Below is a prime example. Read to the end and you'll find out why.



It's time to take the original form blocks used to cut out the parts and create some "final" form blocks. This entry just covers the steps of preparing the ribs, not actually cutting them. That and the backing blocks will be tomorrow.

The original form blocks have 1/2" tabs and flanges on them. That's great for cutting out the parts, but we need to bend those tabs and flanges over at 90 degree angles. In order to do that we need to make some new form blocks that don't have the tabs and flanges on them. As you have noticed, Chris created two form blocks (front & back) for each of the rib shapes so we could sandwich the pieces together for routing and band saw cutting. I'll be using the "back" form block as my base for this process.

There are two blocks needed. A bending block which the metal gets bent around and a backing block which is used to clamp the metal tightly to the bending block so it doesn't bulge out.

Here is the process of making the bending block:

  1. Make a copy of the original form blocks using whiz bang all in one copier. BE CAREFUL... I had to tweak some settings to get a copy that came out to be the same size. Plus or minus a few thousandths which is more precise than I can cut :)
  2. Cut the copied shapes out of the paper.
  3. Take a 3/16" drill bit and make holes in the paper right where the copy shows the original holes.
  4. Put your 3/16" bolts about a half inch through the holes you just made.
  5. Spray some adhesive glue on to the block.
  6. Put the paper onto the block by inserting the bolts in to the holes and then sliding the paper down onto the block.
  7. Rub the paper on to smooth it out and let it dry.
  8. Now using a band saw or scroll saw cut to the appropriate lines on the paper.


QUESTION: Why go to all this trouble? Honestly you could just use the top block which already has the paper glued to it and save yourself the trouble of copying paper and gluing it on the block. Either way you want to preserve one block in case you screw up a rib and need to make another on that's the same size as all the rest. I chose to use the bottom block because the holes are counter sunk just a bit which allow the bolt head to be sunken in so the form lies flat for routing and cutting. I'm hoping I can use that to help speed up the bending process (check out that entry when it shows up). Besides, I figured it would be "quick" to make a copy, cut it out and paste it to a block. I didn't figure on running out of black ink or scaling issues with the copy, help from a small child, etc, etc. In hind sight, it would have been faster to use the top block and counter sink the hole just a bit. Oh well, it's nice to have that paper glued on the top block just because it looks cool sitting on a shelf when you want to show someone later on :)



REAL ANSWER: I'm an idiot. You need to bend left and right versions of every rib and I wasn't thinking about that. By far the best and fastest way to do this is to simply take the original block with the drawing on it, cut to the OUTSIDE line which represents the final shape and then using a spade bit counter sink BOTH sides about 1/4" or enough so a nut and washer can sit in the counter sunk area without protruding. See the entry on bending aileron ribs to see how it all fits together.

REMEMBER that those three lines together represent a curved edge. See later entries for how to get the 1/16" rounding on the edge.
Ribs ready to be cut.

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