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Vacuum bagging

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Flem:
So last summer I said I would share some info on how I press my bows. Thought I better keep my word and since I am semi documenting my swap build, thought this is a good opportunity to do so.
First I want to say that this is only one way to press a bow, no better or worse than any other method, just where I have ended up.

So anyways I start with a vacuum pump.
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There are lots of plans for these, Joe Woodworker has a big section of examples people have made and they are all much nicer than mine. You need a vacuum pump(bottom left), pressure switch (#1), solenoid valve(#2) and the tanks. You could just run a pump without anything else, but the pump would almost have to run continuously. The tank setup allows for a approx. 10min on/off cycle. I've yet to get a perfect seal with no pump cycling. Thats not to say it can't be done. I'm content with this one, but if I built another, I would not use any plastic tubing or PVC.

Flem:
Speaking of tubing. I started with reinforced vinyl, no good, it doesn't like heat. The green stuff is heat tolerant reinforced rubber (250F). I put a quick disconnect and a check valve in the line, because it nice to be able to pull the vacuum on your bench before going in the hot box. Originally I used the little brass connector to attach the vac line to the bag, but found that it got too hot and weakened the interface with the bag. I replaced it with a nylon bung for a plastic barrel (250F).
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Roy from Pa:
Pretty high tech there, Flem.

Looks cool.

Forwardhandle:
Thanks Flem I have been waiting on this one with great interest I have multipal uses for a vac press , that Joe wood workers page is very good I have been looking for a decent vac pump fo the right $$$ but a little skeptical of some I see for cheap & re builts I know you got lucky on the E box store but I'm not much of a gambler looking for some thing new !

Flem:

--- Quote from: Roy from Pa on March 20, 2019, 04:21:39 AM ---Pretty high tech there, Flem.

Looks cool.

--- End quote ---

Hillbilly tech

So where was I when I ran out of beer...
Bags. You need some sort of tubing or membrane to squeeze with. I was using 4mil LDPE tubing, because I had a roll left over from when I was making skis
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Its a bit wider than I need, but it works. Its about the most common plastic sheeting and its cheap. But above 160F it starts to get soft and distort.
Then I discovered this stuff;
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Its for food vacuum sealers and its good to 250F. If you look on websites that sell composites, there are lots of materials, some reusable for bagging. I'm still looking for the perfect reusable system. I hate to throw away all that plastic after 1 use.
Since most of you guys make curvy bows, I thought I better lend some relevance to this process, so I got out a old recurve form and put four 3/16" slats on to see how they would bend. They were too long for the form so all 4 overlap in the center, making it 3/4" thick. It looks like it did not pull the tips down all the way, but thats because the excess bag material pinched together before it could suck onto the form.
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I noticed later that I had left the pressure on the vac set to 12hg for another project. At my elevation I can pull about 25hg.

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