nature to over engineer a solution I decided to try something a bit different.
Let me start by saying I did in fact go to quite a number of fall fairs in my youth, but never got into
playing whac-a-mole(*), hence my desire to come up with an alternate procedure.
There was also a desire to be able to work on this task at my own pace (read that as really slow)
without keeping the house and neighbourhood awake (a lot of my build time is after normal lights out).
What I came up with is using a custom made set of bending dies cut from Home Depot aviation oak.
- The two dies replacing the normal jaws in a vise. The male die is on the right and has a
protrusion to push on the vertical flange and a slot that is just deep enough to touch the
horizontal flange at the same time for the same width. The remainder of the slot for the
horizontal flange is an extra 1/4 inch deep simply giving vertical support to the flange while
allowing the flange to be pushed into it while bending. - The female die is on the left and holds the vertical flange from going up and down, but has a
recess that allows that vertical flange to be pressed into (i.e. the cut out is 3/4 inch high). There
are small sections on the left and right of the female die that are not recessed that act as the
pivot points during bending. - A test piece of 3/4 inch angle inserted into the female die.
- The same test piece inserted into the male half of the die.
along where the bend was to be created. Putting those ticks and numbers on multiple surfaces made
things go much faster. By sliding the longeron through the dies a half inch at a time and giving the vise
a tighten, a smooth curve was formed with surprising little effort, you really don't have to crank the
vise super tight. It turns out to be very easy to over bend, luckily with a few extra pieces of scrap oak
in the right place, the same setup can be used to remove a bit of bend if you happen to over bend, not
that I would know about that
.I used a stiff plastic template for the curve to get the aft section as close a possible, and then used the
aft canopy deck as a guide from where it starts until the forward end of the curve. I did this by putting
a line on the horizontal top flange of the longeron 7/16 of an inch from the vertex and then centering
the line in the pre-punched holes of the aft canopy deck (F-721B).
- The bent longeron in the custom bending jig. There was only about 1/8 inch of out of plane
bending that had to be corrected, and that was easy removed by hand.
- The aft canopy deck sitting on the bent longeron. The line on the top service of the longeron can
be seen through each pre-punched hole, definitely less than a 1/16 inch error. - A couple of clamps at the forward end since there is no bend there, it is a good place to start and
get that reference line in the center of the pre-punched holes before drilling. - Drilled and cleco'd.
- That reference line on the top surface of the longeron can be seen going through the newly
drilled holes that were made using the aft canopy deck as a template.
- After all the work doing the smooth bend, putting the sharp downward bend and twist in was
so easy. I used this tool to put the twist in rather than a crescent wrench, seemed to me it would
have less tendency to add any sharp bends or nicks. I used the smart tool in about four places
along the twist to make sure it was relatively smooth over the length of the twist.
know what they were for and someone tried to sell me some angle shaped like that, I think I might
tell them where to go
.(*) Whac-A-Mole - Smack a rodent on the head with a hammer only to have it pop up somewhere else.
CJ