Bill,
Thanks for putting the brake on line. I might as well give everybody
some background info on bending leading edges. My first attempt at
bending a leading edge was to take a 4' x 10' piece of alum and bend it
until the 4' edges touched. Almost impossible, especially by yourself.
First attempt to fold it resulted in a kink on one side. I figured that
could be the bottom, and tried again. Another kink. Trash one piece.
Second attempt, I screwed a 1" x 4" piece of wood to one edge. Folded it
over and screwed the other edge to the 1 x 4 (not easily). Then I took
a
2 x 8 and started mashing the whole mess down. Eventually, it looked
like it might be OK, so I took the screws out, marked a leading edge
centerline, laid out all the holes and the shape, then cut it to size.
Cut a template to check the leading edge radius- found much more bend at
the ends than in the middle. Trash #2 attempt. Decided it was time to
quit wasting alum and come up with something that would work on the
first try. I made a 4" press brake to experiment with spacing on the
female die. After a few attempts, I was able to get the radius and bend
angle called for in the plans. Cut another leading edge to final shape
and drilled all the holes, popped it in the brake, and out came a
perfect (at least I thought so) leading edge. When somebody is ready,
I'll write up how I chose to install it. Did some experimenting to
determine size for the dies for the tailfeathers, amd made a four foot
version of the big brake. Also cut tail skins to final shape and drilled
holes before bending. Any questions, give me a holler.
Tony Spicer, Sonex #32
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Message: 2
Date: Tue, 23 Feb 1999 13:00:32 -0700
From: Bill Von Dane <bvondane@atmel.com>
Subject: Sonex Press Brake
Press Brake for Wing Leading Edge Bill of Materials:
1 1/4 EMT conduit (1 1/2 OD) Lowe’s part# 72717
1 each 2 x 10 x 10’
1 each 2 x 8 x 10’
1 each 2 x 4 x 10’
2 each 3/8 drop in concrete anchor (Lowe’s part #76422)
2 each 3/8 coupling nuts
2 each 3/8 threaded rod 3’ 1 1/2 x 1 1/2 x 1/4 scrap alum
2 each 2 1/2” drywall screws
Select the straightest lumber available.Draw a centerline on 2 x 8. Measure
15/16” on either side of centerline and draw two lines. Using drywall
screws, attach the 2 x 4’s to the 2 x 8 on the 2 lines. This will leave
a
3/16” gap on either side of the conduit. Draw a straight line down the
conduit. Measure halfway around (2.36”) and draw a second straight line
(make two marks 2.36” apart on a piece of card stock to measure). If you’ve
done it right, the two lines will be 180 deg apart. Measure in 4” from
each
end and drill a 1/2” hole thru both sides of the conduit. Drill a 3/16”
hole
every 12” down both sides of the conduit. Countersink one set of holes.
Drill 1/2” holes on centerline of 2 x 8 to line up with holes in conduit.
The next step is to drill 1/2” holes in the ends of the 2 x 10. It can
be
very difficult to drill a straight hole thru the 2 x 10. The easy way is
to
have a 2” x 5” hole on the side at each end that is centered on where the
1/2” hole will be. With that, all you will need to do is drill a short
1/2”
hole down from the top and another up from the bottom. Screw the conduit
to
the 2 x 10. File any protruding screw heads. Lay out two holes on the floor
that are the same distance apart as the 1/2” holes. Drill 1/2” holes in
the
concrete floor deep enough for the anchor to sit flush. Whack the anchors
with a center punch and big hammer. Cut the threaded rod in half and insert
into the anchors. Bend rods until plumb. Do not try to anchor the 2 x 8
to
your workbench. IT WILL BEND THE BENCH! Place 2 x 8 over threaded rods.
Shim
any low spots between floor and 2 X 8. Drill a 3/8” hole thru the 1/4”
aluminum. These will be heavy-duty washers. Place the 2 x 10 on the threaded
rods, then add aluminum plates and coupling nuts. A regular nut might work,
but I wanted the additional contact area the coupling nut provided. Put
blocks under each end of the conduit to provide clearance for the skin.
At
each end of the skin, make a mark 15/16” on either side of the skin
centerline. Put skin on press and line up marks with the edges of 2 x 4’s.
Remove blocks and allow conduit to rest on skin. Check marks again. Tighten
one nut just until the skin edges start to raise, then go to the other
end
and repeat. Alternate 3 turns at each end until everything bottoms out.
You
can either start out with the press and get it right the first time, or
trash several pieces of aluminum, then build the press (like I did).
Changes for Tailfeathers
Use a piece of 1/2” conduit (5/8”od) screwed to a 1x8x4’ for the male die.
Use 2x4’s spaced 1 5/16 apart for the female die. Make sure male die centers
in female die and that it is perpendicular to female die.
Tony Spicer Sonex #32
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