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Vacuum bagging and which adhesive
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=55745
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Author:  surveyor [ Wed Jun 28, 2023 5:10 pm ]
Post subject:  Vacuum bagging and which adhesive

I'm building a Gypsy Jazz Selmer style and have been researching this and will try to do "double sides" in a vacuum bag but haven't decided which adhesive to use. It's down to West Systems epoxy, maybe with a chopped fiber additive or a formaldehyde urea resin 2 part mix. I'm trying to find out if there will be a bad smell afterwards using the formaldehyde urea mix. From what I've read, there is less chance of "bleed through" using it.

Author:  James Orr [ Wed Jun 28, 2023 7:52 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

I’ve had extremely good results with Unibond. Absolutely no bleed through like you mentioned.


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Author:  bcombs510 [ Wed Jun 28, 2023 8:05 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

+1 I have been using unibond based on James recommendation for a few years. I use it to laminate full width lining sides when I then slice up to use for solid linings. It works great and lasts a long time.


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Author:  Colin North [ Thu Jun 29, 2023 5:36 am ]
Post subject:  Re: Vacuum bagging and which adhesive

Which Unibond are you using!?

Author:  Barry Daniels [ Thu Jun 29, 2023 6:41 am ]
Post subject:  Re: Vacuum bagging and which adhesive

You can get a bit of bleed through with either glue. But it sands off and doesn't really cause any problems.

Author:  Mike Thomas [ Thu Jun 29, 2023 6:56 am ]
Post subject:  Re: Vacuum bagging and which adhesive

Bleeding through with epoxy is not a problem if you were intending to pore fill with epoxy anyway.

Author:  surveyor [ Thu Jun 29, 2023 7:23 am ]
Post subject:  Re: Vacuum bagging and which adhesive

Ok, there's Unibond One (1 part ,PVA resin) and Unibond 800 (formaldehyde urea) . which would I need? Also, I usually pore fill with Z-Poxy finishing resin. The outside layer will be spalted Sycamore.

Author:  bcombs510 [ Thu Jun 29, 2023 7:45 am ]
Post subject:  Re: Vacuum bagging and which adhesive

Colin North wrote:
Which Unibond are you using!?

The 800 - https://www.vacupress.com/product-categ ... ibond-800/


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Author:  Barry Daniels [ Thu Jun 29, 2023 9:49 am ]
Post subject:  Re: Vacuum bagging and which adhesive

If you pore fill with epoxy then using it to laminate the layers would keep everything compatible. Any splotchy bleed through would be incorporated into the pore fill.

Author:  surveyor [ Thu Jun 29, 2023 11:32 am ]
Post subject:  Re: Vacuum bagging and which adhesive

So, I might as well use the Z-Poxy I already have instead of buying a gallon of Unibond 800?

Author:  surveyor [ Thu Jun 29, 2023 11:37 am ]
Post subject:  Re: Vacuum bagging and which adhesive

Also, about how much Z-Poxy will I need to do one guitar? I have about 5oz. on hand (resin and hardner). This is one thing I want to have more than enough to do the job once I get started mixing.

Author:  bcombs510 [ Thu Jun 29, 2023 12:57 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

Make sure that you’re using the zpoxy finishing resin for porefill. There is more than one version labeled as zpoxy.


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Author:  surveyor [ Thu Jun 29, 2023 3:00 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

It's the "Z-Poxy finishing resin and on the box "Laminates Wood & foam"

Author:  Barry Daniels [ Thu Jun 29, 2023 3:48 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

I would suggest a structural epoxy for the laminating instead of a finishing resin. I prefer a formulation designed for strength instead of surface quality. I like West Systems.

Author:  bcombs510 [ Thu Jun 29, 2023 4:44 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

Agree with Barry, that’s why I was asking about the zpoxy you had. I would be hesitant to laminate sides with it. It could work, but would be a problem if they decided to delam.


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Author:  surveyor [ Thu Jun 29, 2023 5:44 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

Ok, Thanks guys, I'll look into the West Systems products.

Author:  James Orr [ Fri Jun 30, 2023 5:38 pm ]
Post subject:  Vacuum bagging and which adhesive

Sorry guys, I’ve been traveling!

I’m not trying to sell anyone on products, but I’m a Z-Poxy guy, too. I haven’t had any issue with the combo bc the Unibond doesn’t bleed through.

If Unibond has a downside, it’s that the resin has a somewhat short shelf-life once you open it. My West epoxy just lasts.


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Author:  phavriluk [ Fri Jul 07, 2023 8:19 am ]
Post subject:  Re: Vacuum bagging and which adhesive

For those using West Systems epoxies, check the shelf life after opening, it's not infinite, but it may also not matter much for guitars as compared to structural assembly in boats and airplanes. Test first.

Author:  saltytri [ Fri Jul 07, 2023 11:55 am ]
Post subject:  Re: Vacuum bagging and which adhesive

I've done laminated sides, mostly three layers, on dozens of ukuleles, all with Titebond red and clamped mechanically with a closely fitting caul. I have a vacuum system and tried using it for sides early on but found that it was an unnecessary complication. Laminated backs are the opposite. It's easier to use a radius dish in a vacuum bag and the back will potato chip unless epoxy is used.

Author:  Terence Kennedy [ Fri Jul 07, 2023 2:24 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

Satisfied Unibond 800 user, have laminated lots of sides with it. Clamped over an inside caul. The resin is available in quarts or pints and refrigerating it seems to prolong shelf life. I like that it dries like glass, really hard.

https://nelsonpaint.com/search.php?sear ... on=product

Author:  bcombs510 [ Fri Jul 07, 2023 3:09 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

Thanks for that link Terry! The cost for a quart from them is the same as the 1/2 gallon from vacupress ($26), but at least I wouldn’t be tossing so much in the trash. The pint stored in the fridge might be the perfect compromise!


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Author:  surveyor [ Fri Jul 07, 2023 5:45 pm ]
Post subject:  Re: Vacuum bagging and which adhesive

I already ordered some "West Systems" epoxy , enough to do one guitar. I'm getting there, piece by piece. Got the pump (Gast brand) , ordered a gauge and check valve, made the inside "mold"/caul, outside mold and now all I have to do is figure out how to put that bend/pilage in the top. I've been reading the discussions in "Django books", seems like everyone doing these models have their own take on what is needed as far as that goes. Most of the time you want to get rid of a "belly", not make one, ha.

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