Official Luthiers Forum!

Does anyone here make their own vacuum press bags? If so, any tips...

I spent a couple hours on the Joe Woodworker site last night. Lots of ideas....

Here's the bag that started the wheels spinning... It's LexLuther's... I'd buy some, but, they are expensive, the available sizes don't quite suit what I have in mind, and I don't feel like waiting 2 weeks for them to arrive. Besides, I'm a roll your own kinda fella. Why buy what I can make and then customize further, right?

.

I've always made my own.
My local plastic store (Tap Plastic) has 10 and 20 mil vinyl that you can glue
3 edges with vinyl adhesive and roll/clamp the 4th side after putting your
work in.
The vinyl is a bit thick and clumsy, but it lasts well.
West system epoxy makes a very thin and heat resistant bag material that is
nice because you can put a heat lamp on it while it's running with out
melting the bag. They also sell a "mastic roll" putty tape that works for
sealing the bag up. I get these items at my local marine supply store.
I'm having some troubles with my site uploads, otherwis I'd post up some
pics.
-C

_________________
Freeborn Guitars
and home of BeauGuard©

Send your pics to me... I will post them. I am interested in this too.

brock at poling guitars dot com

_________________
Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Mario-
I've laminated a few guitar backs in my radius dish, and a bunch of panels over the years for boat projects and such, and I've done fine with a garbage bag - about as low-tech as you can get.
Some window screen for breather (something that's missing in the picture above, but the bag is stiff enough to allow air flow in the folds, I guess) and some glaziers's mastic (sticky black stuff on a roll, very handy- check with HD or hardware store) to seal around the hose- stick the panel and form in the bag, stick the hose in, lay the breather over, and twist the bag around the hose where you've put some mastic and put a few wraps of PVC tape to keep it sealed- that's about it. When you're done, just throw the bag away- no need to worry about cleaning squeezeout off your expensive bag.

It works for me.

BTW- the combination of heat (heat lamp or just the warmth from a 'desk lamp' on a dark garbage bag) and vacuum is a very effective setup for taking all the moisture out of the top layer of wood. I was laminating up a 'top' for a reso project a few days ago and it came out of the bag (after the epoxy had set hard) with quite a curl. I wet the surface and hung it up in the shop- it took a couple of days to flatten out. This would not be such a problem with thin veneers which would get completely saturated with glue, I'd guess.

Gougeon (WEST) produces a 50pp manual on vacuum bagging, which I'll probably buy ($5) the next time I see it.

WEST VAcuum Bag Manual

Cheers
John

Garbage bags work fine. When I use them, I have a Vacumagic Megaspider Ultradiffuser to make sure I don't get a false seal. The VMU is actually just a vacuum hose attached to a 4-way barb (a T would work) with two more short hoses attached to it. The short hoses have a bunch of holes drilled in them so the vacuum doesn't come from just one hole and isn't easily sealed off. Pulling the bag closed over the hose and using one zip-tie does the trick.

If you want to make a thicker, sturdier bag, then you can heat-weld most plastics including the vinyl. I just roll the two pieces over a bar and use a small torch. Requires a bit of finesse, but it makes a nice seam. I suppose you could always clamp them between two pieces of aluminum and heat one up with the torch, as well. I use the VMU either way.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

dang, John,  think you just fixed me up for the weekend's work! Thanks muchly! Never thought of window mastic....

I'll eventually get some vinyl and do a good setup, but I'm making something -now- that requires mucho improvisation.

Some of y'all have Tap Plastic stores, locally? And a Marine Supply store?!? Oh, for shame... I've had to wait days to get milk/bread/potatoes at times, because the stores ran out.

Then there's the time the Beer Store ran out of Molson Ex! widespread panic in the streets of Ansonville....!

Yeah, think I'll head down to Tap Plastics on my way back from Marineland... Ughh. <bg>

Ziplock is now making some large size bags (up to 2' x 2.7') that would be plenty big for a guitar top or back. You would need some type of air fitting to connect the vacuum line.

[QUOTE=BarryDaniels] Ziplock is now making some large size bags (up to 2' x 2.7') that would be plenty big for a guitar top or back. You would need some type of air fitting to connect the vacuum line. [/QUOTE]

IN the same vein, I saw an ad on TV for bags for storing quilts, etc - sold at WalMart- that use the vacuum cleaner to evacuate- they also have a zip seal, and could be a starter for a 'real' vacuum bag.

John

woohoo! Local hardware store had 30 mil vinyl....! Truck stop had screw on tire valves.. Lumber yard had both mastic, and butyl.

Couldn't find a Tap Plastics store anywhere, though <g>

 My little town surprised me today.

Off to the land of vacuum assit.

.

Mario, Are you laminating sides? If so consider making a small bag to slip the laminates into external to the mold. It works better.

Ken, no, not quite laminated sides. I 'double' my sides in the upper bouts as reinforcement for the soundport. Usually a solid piece that matches the ribs.

Now, on this current one, a quilt maple 12 fretter, we want to see "purfling" lines inside the soundport, so I needed to laminate a mahogany/maple/mahogany/flame-maple veneer sandwich.

All done, thanks to the help here. I;ll rwefine the setup later, but it worked well last night!

Can yuo explain what you're trying to say, though, please! i don't quite grasp it, and veneering like this is new to me.
 

Finally we've got our hosting/posting thing worked out!
So, here is my very quick and even dirtier vac bag for bracing tops and
backs.
I use the West Syst. film and "mastic putty on a spool" (that's the yellow
stuff).
I take one piece of film, fold it, seal the edges with the mastic, seal
around the vinyl hose at the same time, plug it into a really crude little
piece of pliwood with holes and grooves, the other end to a compressed
air venturi gizmo, plug 'er in and let it do it's thing.
I like the West Syst stuff because it's really tough and very thin, so it
conforms around the parts well. I also like it better than the opaque
rubber membranes because you can see if a brace has tipped or isn't for
some reason behaving (I prefer my unwrapping surprises on Christmas...)
I seal the bag with a piece of aluminum angle clamped to the edge of my
bench. I use a strip of closed cell neoprene foam weatherstrip tape(the
black stuff) along the clamped edge.
When I'm using a dish for the shape, I'll put it in the bag when I'm doing
the glue up. Otherwise I'll just back up the top or back with a piece of
stiff cardboard and let the braces pull the top to their contour.
Not very scientific, but hey, we're not building pianos!



As for the whole heatlamp controversy, I'm only removing moisture that
I've introduced by way of the glue. The lights are on and the top is in the
bag for 25 minutes tops, then it comes out and re-acclimates. I control
the heatlamps by way of a variac, so it's never a full blast exposure.
-C

_________________
Freeborn Guitars
and home of BeauGuard©

[QUOTE=grumpy] Ken, no, not quite laminated sides. I 'double' my sides in the upper bouts as reinforcement for the soundport. Usually a solid piece that matches the ribs.Now, on this current one, a quilt maple 12 fretter, we want to see "purfling" lines inside the soundport, so I needed to laminate a mahogany/maple/mahogany/flame-maple veneer sandwich.All done, thanks to the help here. I;ll rwefine the setup later, but it worked well last night!Can yuo explain what you're trying to say, though, please! i don't quite grasp it, and veneering like this is new to me. <div style=": ; width: 28px; height: 28px; : 1000; display: none;">

I should add that I put my veneers inside plastic sheet so no glue squeezes out making a mess of the bag, then surround them with bleeder cloth (nylon hardware screen) and then into the bag. The bleeder cloth needs to make contact with the exit hole for maximum evacuation of air. Etcetera and etcetra.

Ken, do you have photos you can post? I'm not "getting" it. If I place the laminations in a separate bag, outside the form, and vacuum that, they won't take the shape of the form. A photo would clear things up greatly. And be much appreciated!

You have a huge set up to make a little bent lamination.

Yessir! <bg>. It's the whole piece of vinyl I purchased. I just used those pieces of laminated flooring(great jig stock, and I grab scraps everywhere I can) to seal the 3 open sides for this "run". I left it full size, and my pump evacuated the whole thing in around 20 seconds, so it worked well, and there were no voids at all; very smooth on the form. I found some swimming pool liner adhesive yesterday, so will make the bag permanent soon. At the size i have there, I can just get a dish in if I want to try pressing braces or making a laminated back or something, so I think it'll stay that size. Didn't seem to hurt the little job here...

I need some screen. Not long ago, I found something that would have been perfect, but damned if I can remember where I saw it. It was like expanded metal, but in plastic. The stuff would be ideal as a mesh...

 Looking forward to photos and clarity.... thanks!

Mario,

Try googling "plastic hardware cloth" maybe that's what your looking for.

_________________
Horton, MI

I bought some plastic breather material from the Joe Woodworker site that is like expanded metal. Haven't used it yet.

"plastic hardware cloth"

 That's it! Now, where the hell did I run across it...

My way of doing it consists of using the bag "external" to the mold. When the vacuum is pulled, the bag can actually be removed from the form and it will stay in that shape. I just leave it until it dries though. Here are some photos

uggh sorry about the format of that last post.

Ignore the aluminum, I have abandoned using it as it makes things worse.




I have lost interest in making guitars and am heavily into violins and making a bass violin...can't get it out of my blood...
So I didn't even get this ES335 finished.

You can find most everything that you need at Aerospace Composite Products located in livermore Ca. Their catalog is on line.

Al

[QUOTE=grumpy] "plastic hardware cloth" That's it! Now, where the hell did I run across it...
<div style=": ; width: 28px; height: 28px; : 1000; display: none;">

[QUOTE=grumpy]"plastic hardware cloth"

 That's it! Now, where the hell did I run across it...

[/QUOTE]

Here is some.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Mario, I think what you are looking for is this rubber mesh they put in drawers bottom

Not no.

But HELL NO!

That stuff is soaked with silicone and plastisizers.... None, nowhere near my home or shop, not even the trailer.

ayee...


.

But thanks anyway <bg>

Waddy, yes, that's the stuff, but I saw some locally(or semi-localy0 not long ago. Maybe it was gutter guard...

Anywho, a good friend e-mailed and has lots a will bring some on the next visit..

Ken, still no idea how you get the laminates to conform to the form. Is the aluminum the form, and you then slide the bag and laminates over it?

At any rate, what I did worked. If I get to building plywood guitars, I'll just use the same form, but whole.

Are you laminating a double bass? Now, there would be a project I'd follow closely!