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 Post subject: Vacuum bag technique
PostPosted: Tue May 07, 2019 7:08 pm 
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Contributing Member
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Joined: Sun Feb 17, 2013 4:58 pm
Posts: 1077
First name: Ed
Last Name: Minch
City: Chestertown
State: MD
Zip/Postal Code: 21620
Country: United States
Focus: Build
Status: Amateur
I have never used a vacuum bag before but had a veneering project. I am a hand tool user and found a hand operated vacuum pump. It was cheap - under $30 for the pump and fitting - and worked perfectly for the 4 panels I veneered at 11" X 30". They even have pictures on their website of a set of braces being glued on a top.

1) 30 seconds of pumping and here is what I had. I had to pump 2-3 strokes every 10 minutes with a couple of panels, but a couple were OK after the first pumping. This will depend on the seal you get at any openings

2) a close-up. The texturing is the surface of the veneer which is flamed ash

Made by Roarocket, no affiliation, yada, yada, yada

https://www.roarockit.com/woodworking-tutorials-categories

https://www.roarockit.com/tap-parts.html

Ed


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 Post subject: Re: Vacuum bag technique
PostPosted: Wed May 08, 2019 6:26 am 
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Koa
Koa
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Joined: Tue Feb 26, 2008 6:19 am
Posts: 567
I like this technique and have wondered if a simple space bags would work. I just might try it.

_________________
Hutch

Get the heck off the couch and go build a guitar!!!!
That's a reminder for me.

"Alan Carruth, IMO the 12-fret 000 or 14 fret OM size (15" wide lower bout) is god's size for the steel string guitar, especially for fingerstyle. I would also try to get away from scalloped bracing and lean toward 'straight' or 'tapered' bracing. Scalloped emphasizes bass and 'punch', where straight bracing, and especially 'tapered' (sometimes called 'parabolic') leans more toward treble and sustain."


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 Post subject: Re: Vacuum bag technique
PostPosted: Wed May 08, 2019 7:00 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sun Mar 30, 2008 8:20 am
Posts: 3517
Hi Ed,
Did you buy the "super pump" or the regular pump? How difficult was it to evacuate the bag?
I made some side laminating forms by thermoforming corian. Presently I use kerfkore and a multitude of clamps to compress the veneer and hold it against the form. Since the laminating form is only 1/2 inch thick it may be possible to fit it in a skateboard bag and vacuform the sides.


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 Post subject: Re: Vacuum bag technique
PostPosted: Wed May 08, 2019 8:33 am 
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Cocobolo
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Joined: Mon Mar 17, 2014 1:27 pm
Posts: 286
First name: john
Last Name: shelton
City: Alsea
State: Oregon
Zip/Postal Code: 97324
Country: usa
Focus: Build
Status: Professional
Clay S. wrote:
Hi Ed,
Did you buy the "super pump" or the regular pump? How difficult was it to evacuate the bag?
I made some side laminating forms by thermoforming corian. Presently I use kerfkore and a multitude of clamps to compress the veneer and hold it against the form. Since the laminating form is only 1/2 inch thick it may be possible to fit it in a skateboard bag and vacuform the sides.


Clay, I have a vacuum press set-up which I use for laminating double tops and backs but for laminating the sides I prefer clamps. I know other people use vacuum for sides but I just don't trust the vacuum to apply the force needed to press the multiple lams on the sides together. I use an inside mold.


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 Post subject: Re: Vacuum bag technique
PostPosted: Wed May 08, 2019 5:04 pm 
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Koa
Koa
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Joined: Mon Nov 24, 2008 12:17 pm
Posts: 938
City: Escondido
State: CA
Zip/Postal Code: 92029
Country: USA
Focus: Build
Status: Semi-pro
Funny how we all develop our own ideas. I’m the opposite. I don’t trust clamps to give me even pressure to laminate multiple layers in a side. So I vacuum it flat for 2 hrs. Once I feel confident the epoxy is set but not cured I take the sides from the bag and press it into a mold. It cures to the proper shape in a mold.


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 Post subject: Re: Vacuum bag technique
PostPosted: Wed May 08, 2019 8:51 pm 
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Contributing Member
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Joined: Sun Feb 17, 2013 4:58 pm
Posts: 1077
First name: Ed
Last Name: Minch
City: Chestertown
State: MD
Zip/Postal Code: 21620
Country: United States
Focus: Build
Status: Amateur
Clay

It took about 20 seconds of pumping to empty the bag. With the curved/coopered doors there was planty of air space in there, but your sides will have more volume to evacuate.

I sprung the extra $2 for the super pump. I won't be using it anytime soon - you are welcome to take it and the bag to try out when we see each other next.


Ed


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 Post subject: Re: Vacuum bag technique
PostPosted: Thu May 09, 2019 8:26 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sun Mar 30, 2008 8:20 am
Posts: 3517
Hi Ed,
Thank you for the kind offer. I will probably take you up on it. It is always nice to "try before you buy". I understand John's reservations about using vacuum, and he may well be right. The corian molds I have made are only 1/2 inch thick so they may fit in the bag better than the block molds I also use.


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