7075 Al alloy pole/carbon fiber arrow/foam external frame w/ UHMWPE fabric + bag

Hi Nathan, here’s a pic.  The black coloring on the poles, i think, is not paint, but the extra thick Al oxide layer created by the hard anodization process–you should be able to see where it’s been removed, at least on the outside.  The white fabric that the poles are on is the UHMWPE fabric.

Hi Clifford, i did pack them with sand before bending.  If you look at the first pic, the curved pole has vinyl end caps on it–that was used to keep the sand in them while i was bending them.

I think the problem was with the technique–previously, i very slowly and carefully bent them.  The next day, i was less careful and almost jerked pulled it.

I can see your point about the greater forces than typical being applied when i bend them by hand.  If it was more weight than just a couple ounces, for a lot more strength, i would probably skip the carbon fiber/foam core part.  But it’s so light and easy to do, i figure why not.

Yesterday, i prepped the fabrics and put a coat of adhesive on one side of each.  Today, i put another coat of adhesive on, put the fabrics together, put a bunch of books on top and let it set and cure for a few hours +.  Then i took an iron on low and ironed it on the Silpoly side.  Let it sit for a bit more, then threw it in the dryer on medium low heat setting to speed up the curing.

Then i sewed it around the perimeter and then an X.  I don’t think the adhesive bonded very well though.

Yesterday i put the frame together.  As mentioned, i’m now using the Easton Carbon FX poles.  I had bought the 90 degree Al elbows that normally go with them, but when thinking about it and trying different things, i noticed that the carbon poles fit pretty well inside the .49 Al elbows that i had ordered previously.  I figured going with extra strength of these elbows was a wiser idea.  I also like the carbon poles going inside the Al, rather than the Al going inside the carbon.  The Al has a little give/ductility which may help protect the carbon fiber during possible impacts. I’m also hoping that the foam core provides a bit of absorption and wall protection to the carbon fiber for impacts.

Most of the frame was epoxied together.  But, i took some 3+” spray foam and sprayed foam inside, so i wasn’t able to epoxy two of the connection points.  To make up for that, i took FiberFix and wrapped these connection areas the most with it.  I used some of the rest on some other joints, but the stuff doesn’t last long once unsealed.

Because i originally prepped the .49 elbows to be epoxied with the .49 Al poles, i had exposed areas where i had sanded off the hard anodization.  To give those areas of the Al a little extra protection, i wrapped them in some self adhesive silicone tape.

After the foam fully cured, the frame is surprisingly stiff for a simple, square structure.  I’m still wrapping it with dyneema or spectra cord, but i guess due to the foam/carbon fiber combo, i need it less for the structure/stability. It has a little flex/give but really is fairly stiff considering the simple structure with no cross supports etc.

So far, the frame weighs 7.5 oz.  The horizontal/vertical stringing with with dyneema cord will add maybe about an ounce.   The main pack material weighs 8.6 oz.  Tomorrow i plan to attach the frame to the pack material and start making and attaching the shoulder straps, hip belt, etc.  Might not finish since it’s a friend’s B-day tomorrow and i’ll be out and about later on.  Since the upper and lower poles are not being bent, i plan to sew some Evazote foam/fabric over key parts of the frame.  I’m guessimtating it to weigh around 1.5 to 1.75 lbs total after shoulder straps, etc are added.

Pic of the frame (it’s very slightly skewed and not fully level on one part):