Flute question for tipup canopy F-631A rib

[Buggsy2]

I am at the top of page 9-5 (Canopy) for the RV-9 but I'm sure this is the same for an RV-7, a tipup canopy.

The instructions for the F-631A "ribs" (I like to call them hoops) call for the outer flange to be bent to an angle of 92.5 degrees (bend flange to inside the channel). OK, I'm doing that and sure enough the hoops no longer lay flat on a table. But Vans anticipates that and says to flute the hoops to make them lay flat. This last part puzzles me.

There are 4 possible ways to flute: outer or inner flange, and flute depression inside or outside of the flange. All these choices! I don't know which choice to use to make the hoop flat.

I tested on a bit of scrap 0.025 angle but couldn't see it any consistent pattern to fluting direction ==> bending. So I'm asking here for hints.

TiA!!

[Mel]

Lay the part on the table with the flange facing up. Fluting the flange where it is "up" off the table will lower that point.

[Buggsy2]

Originally Posted by Mel

Lay the part on the table with the flange facing up. Fluting the flange where it is "up" off the table will lower that point.

Thanks! Will it matter what direction it's fluted? That is, which side of the flange (inside or outside) the single bar of the flute tool is on? Or maybe it should always be fluted in the direction of the hoop's curve so single bar inside?

[WenEng]

You don't want any ''hump'' e.g. flute, sticking up. The single flute bar on the squeezer should face where the canopy would be so when you squeeze, it forces the indent downward away from the canopy.

[flion]

I would recommend a metal shrinker, if you can lay hands on one. Lay the web on the table and mark where it is 'up' off the surface. Shrink the flange around that area, checking often to see when you have done enough (and to be sure you don't do too much). That will keep the flanges relatively smooth; once painted they will look absolutely smooth. Much better looking than flute 'dents' everywhere.

[WenEng]

http://www.vansairforce.com/communit...ad.php?t=79243

If you Sikaflex your canopy, you have options..

http://www.vansairforce.com/communit...ad.php?t=68902

[Buggsy2]

Followup.

Thanks to all who replied. After bending the outside flange inward a bit to get the 92.5 degree angle, the two ends of each half-hoop (quarter-hoop, if you think in full circles) were raised on the inside flange. I didn't see @flion's post about the metal shrinker in time so fluted the outside flange, single bar of fluter on the outside bend.

Didn't see much improvement! So I fluted the inside flange. Still little or no improvement. So, reasoning that if bending the outside flange made it raise off the table from flat, maybe bending the inside flange to the outside would do the trick. And it did! At least for one half-hoop.

For the other hoop, I first tried bending the inside flange; some improvement but not enough. Fluted inside and outside flanges; no improvement. So finally clamped one end of the half-hoop to the table, clamped wood scraps to the other end, and twisted the whole thing. Voila: flat. Matches well to the already-made rear cabin frame too.

Building on.