Today was fluting day- the forward portion of all the ribs need to be fluted. Here's the tools I use- fluting pliers, flat pliers, triangle and a wood block with slot and rounded nose for bending the flanges.
When the flanges are formed in the factory, they warp slightly as seen in this photo.
Flutes have to be added to the flange to pull the rib back to flat. There is a real art to fluting- if you flute too deeply, the rib bends in the opposite direction. Each flute needs to be approximately half way between each rivet hole. I've found that you need slightly deeper flutes towards the middle and shallower flutes on the ends of the ribs. In general I make two passes- the first pass I just lightly flute so the rib will come close to lying flat on the table. Then I hold the rib down on the table and adjust each flute until I see the end of the rib lift slightly off the table.
After fluting, I go around and check all the flanges to make sure they are 90 degrees to the table. Often the flanges are slightly splayed outwards and have to be bent back using the wood block shown below. I initially just eyeball the adjustments.
After getting the flanges close to 90 degrees using the wood block, I check all the rivet hole locations to make sure the flange surface is very close using my drafting triangle. I'll make small adjustments using my fingers to get the final alignment.
Here's the stack of 28 ribs with flutes added. Woody is double checking the instruction manual to make sure I didn't miss anything.
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