Building the Po' Boy Bending Brake

Most roofing suppliers or contractors have sheet metal breaks. Most
of these place will do your bends for you(10' long, upto .063")for
about a buck a piece plus $0.15 cents for additional bends on the same
pieces. If you tell them you only need 10 to fifteen pieces and its
for a homebuilt airplane, they might even bend them for free.

Bryan

(bryan chaisone) wrote in message om...
Most roofing suppliers or contractors have sheet metal breaks. Most
of these place will do your bends for you(10' long, upto .063")for
about a buck a piece plus $0.15 cents for additional bends on the same
pieces. If you tell them you only need 10 to fifteen pieces and its
for a homebuilt airplane, they might even bend them for free.

Bryan


True, but most of the operators know nothing about aircraft tin
bending. Get them to bend up a small piece first and check the bend
radius before you give them your good spar material. Drip rail and
heating ducting don't care if they get bent a bit tight. 2024 tends
to complain.

Veeduber wrote:
How do you think the wooden brake would do on 8 foot lengths of .032
2024t3? I suggested something almost identical a while back on the
Bearhawk list for bending the spar webs and was met with much skepticism.


-------------------------------------------------------------

Dear Del,

'Think' or know for a fact? :-)

As a general rule the upper limit for wooden brakes is about .063 for tempered
stock but a lot depends on the quality of the wood and workmanship.

Although the load per unit of length remains the same the overall magnitude of
the load naturally increases with the length of the bend. It also becomes more
difficult to keep the leaf in the same plane as its length increases. There
are fairly simple solutions to each of these problems and I would have no
qualms about making up a long brake for .032 myself but I've got a lifetime of
mistakes behind me :-)

I couldn't find any .032 scrap but I did come across some .040 under the bench
and put a 1" flange on a piece just to give you some idea what a wooden brake
will do. (See the pictures WOODEN_BRAKE 05 thru 08 in the file previously
mentioned.) Other than adding a bar and a couple of clamps this is the same
set-up for .016 meaning the radius is all wrong. But what I wanted to
illustrate was the fact that a wooden brake is more than adequate
strength-wise. The real problem is maintaining the uniformity of the bend as
the length increases. It can be done but the solution will depend on your
tools and experience, the quality of the wood you use and how well the brake is
secured. For an eight footer you're talking some loads that will throw the
typical workbench all over the shop; it needs to be secured to the deck.

-R.S.Hoover
Why not visit your local scrap yard & pick up a couple of
large-dimension steel angles in the length you need. At under 20 cents a
pound, you probably won't spend much more money & the strength would be
a lot higher.

Charlie

Why not visit your local scrap yard & pick up a couple of
large-dimension steel angles in the length you need. At under 20 cents a
pound, you probably won't spend much more money & the strength would be
a lot higher.
---------------------------------------------------------

Dear Charlie (and the Group),

In fact, most guys probably do, as I alluded to in the original article. Of
course, this assumes they can weld (and cut) steel, have access to suitable
hinge(s) and so forth.

The result is a more or less permanent part of your shop. Which can get a bit
silly if you're only building one airplane and only need to brake a couple of
bends.

-R.S.Hoover

"Morgans" wrote in message


Perhaps I missed it. Where are the pictures?

http://groups.yahoo.com/group/Fly5kf...SIC%20BENDING/

Or

http://25th.com/t2/viewfull.php?index=621
http://25th.com/t2/viewfull.php?index=622
http://25th.com/t2/viewfull.php?index=623
http://25th.com/t2/viewfull.php?index=624

For a brake I built with Veeduber's inspiration. This is an 8 ft'r.