| Official Luthiers Forum! http://w-ww.luthiersforum.com/forum/ |
|
| Lets talk about vacuum pressing Braces http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=2162 |
Page 1 of 1 |
| Author: | LanceK [ Sun Jun 12, 2005 10:08 pm ] |
| Post subject: | |
I'm going to be bracing up my next batch of 3 guitars shortly after the ASIA Symp. I'd like to use a vac clamp for them. I understand how you build the box to hold the rubber sheeting, but what do you do to the dish that the top/back lay in? Do I need to cut channels in the radii dishes, leave them unchanged? Thanks L |
|
| Author: | Don Williams [ Sun Jun 12, 2005 10:26 pm ] |
| Post subject: | |
Cutting slots in the dish will help evacuate the air under the plate, and help hold the plate in place. At least that's the theory. |
|
| Author: | crazymanmichael [ Sun Jun 12, 2005 10:46 pm ] |
| Post subject: | |
i didn't groove mine and they work fine. also making/buying a pair to cut to a rough guitar shape allows for keeping the frame size smaller. saves working and storage space. also made two frames so that i can do top and back at the same time. |
|
| Author: | LanceK [ Sun Jun 12, 2005 11:02 pm ] |
| Post subject: | |
Michael- did you make an enclosure like Dons or just a top? I suspect that if you have a nice flat bench, with a smooth top, you could just make a top frame, and slap it down on the bench, no? |
|
| Author: | Don Williams [ Mon Jun 13, 2005 12:57 am ] |
| Post subject: | |
Why not? The big issue is getting a good air-tight seal. That's the crucial element. If you had a frame that you placed down over a polished steel table, or a polished Corian table etc, it should work fine. I assumed that the dishes would work ok without the grooves, but that's the way I first saw it done, so I followed suit. |
|
| Author: | crazymanmichael [ Mon Jun 13, 2005 1:04 am ] |
| Post subject: | |
mine are self contained, a bottom with a hinged top. can't see any reason why just a top on a smooth base wouldn't work. |
|
| Author: | Brock Poling [ Mon Jun 13, 2005 1:04 am ] |
| Post subject: | |
That is EXACTLY how Frank Finocchio does it. His dish is corian, and the top plate simply lays on top of it. The vacuum part is made of MDF that has a few layers of finish on it. One nice thing about his is that the membrain is clear so you can see if anything shifted and how much squeeze out you are getting. He just used part of an old vacuum bag. I thought this was a really slick set up. 
|
|
| Author: | Mjoy [ Mon Jun 13, 2005 6:19 am ] |
| Post subject: | |
I believe the issue with slots depends on whether the vaccum membrane is on a frame that is place over the piece, needing a seal around the bottom, or being a bag that the entire dish and top are placed in. If you are using a vaccuum bag, the slots are a definate plus for a tighter seal. Otherwise the vaccum is more likely to seal against the edge of the form and trap air in the space between the bracing and the form edge. The slots eliminate that and give you a much tighter seal, especially if on runs under the soundhole. A lot of people use these bags which are sold for veneer work. I have access to a cabinet shop that lets me use theirs. The slots are much better using these bags. --Mark Joy |
|
| Author: | Joe V [ Mon Jun 13, 2005 11:55 am ] |
| Post subject: | |
These look really slick! Did you build your own system or purchase one? Any advice on how to put one together or where to get one? Joe Volin |
|
| Author: | tl507362 [ Mon Jun 13, 2005 12:17 pm ] |
| Post subject: | |
Joe, I'm working with several builders on building the base unit for this type of setup in the picture above. If you visit my website, you can see the radius dishes that I offer. It is basically the same dish, except with a backer piece of mdf, and it is square, and has the lip that you drop the top part of the vacuum piece onto it. Also, it is covered with a fiberglass resin that will allow you to have a smooth surface to clamp on just like corian. These are custom jobs, but we only charge a $25 extra fee per dish. As for the complete vacuum system, I'm still trying to get my partner to start offering these, but it is a little more involved. Tracy |
|
| Author: | Sprockett [ Tue Jun 14, 2005 1:49 am ] |
| Post subject: | |
You don't need to have any slots, when you pull the vaccum there are little airways along the edges of the braces (where the rubber curves at the edge of the brace) and that's all you need. I use standard dishes on my vaccum press and have a high-end venturi that a friend gave me so I can vaccum out the press very quickly, that's a must when working with Hide Glue. I like franks idea of the clear vac bags, Brock any idea where you can get that stuff?? I'm using the sheeting from LMI right now, it works great but I can't see anything... Cheers -Paul- |
|
| Author: | LanceK [ Tue Jun 14, 2005 2:01 am ] |
| Post subject: | |
Paul, how long do you wait before releasing the vacume and cleaning up the squeez out? I fear the top would what to pop out of the dish, and maybe stress the brace glue joints. For vac clamping bridges, I wait 10 minuts, remove and clean up, then replace for 45 more. |
|
| Author: | Pwoolson [ Tue Jun 14, 2005 2:08 am ] |
| Post subject: | |
Davis, I've got some that has a slight green tint to it but is very transparent. I bought it from a composite place who's name is escaping me now. (And of course I don't have it bookmarked). But if you search for carbon composite vacuuming you should come up with something. Let me know if you don't and I'll dig through my invoices. Lance, About 10 minutes for me too. That's a good time to scrape too because the glue is in the "leather hard" stage and pretty much just rolls off the wood. |
|
| Author: | crazymanmichael [ Tue Jun 14, 2005 2:40 am ] |
| Post subject: | |
paul clear vacuum bag matierial is available from a number of sources including joewoodworker.com. |
|
| Author: | rlabbe [ Tue Jun 14, 2005 2:47 am ] |
| Post subject: | |
I remember over on MIMF David Berkowitz suggested adding a vacuum line to the bottom of the form, so that when you lift the top to clean the glue squeeze out the top will keep the shape of the form and not stress the braces. I haven't tried it myself, but it makes sense. |
|
| Author: | crazymanmichael [ Tue Jun 14, 2005 2:51 am ] |
| Post subject: | |
to be effective it would require sealing tape be applied to the form. i've thought about it a bit but i can't see how to do this when clamping thin plates without introducing distortion. and i've never had any problems without it, so.... |
|
| Author: | Brock Poling [ Tue Jun 14, 2005 3:42 am ] |
| Post subject: | |
[QUOTE=Sprockett]I like franks idea of the clear vac bags, Brock any idea where you can get that stuff?? I'm using the sheeting from LMI right now, it works great but I can't see anything...[/QUOTE] Nothing definitive. I have thought about calling a few cabinet shops around town to see if they have some old veneer bags that are out of service or need replaced. |
|
| Author: | Jim Watts [ Tue Jun 14, 2005 5:47 am ] |
| Post subject: | |
One method to ensure an even vacuum distribution is to include a layer of some type of fabric between the top/back and the membrane. This is standard practice in the composites world and what I do. Works well but kills the advantage of a clear bag. It may not be necessary as some one pointed out. There is a specific material for this called "air weave" (it's a non woven, go figure), but most material will work. It creates little spaces every where so the vacuum never chokes itself off. I also release the vacuum after 10-15 minutes to clear the squeeze out, and then reapply it. |
|
| Author: | John Mayes [ Tue Jun 14, 2005 6:12 am ] |
| Post subject: | |
I've used it in the past, then switched back to go bar's, and now I'm getting some stuff to vacuum again. never used any channels and it works great as long as your pulling good Hg. I'm setting up a tandem vacuum system that will daisy chain 4 presses in a row and I can activate them with ball valves. this is just or ukes though as I'm going to be making a lot of them. |
|
| Page 1 of 1 | All times are UTC - 5 hours |
| Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/ |
|