Official Luthiers Forum!
http://mowrystrings.luthiersforum.com/forum/

Using vacuum to laminate sides
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=53060		 Page 1 of 1
Author:  James Orr [ Tue Mar 31, 2020 11:29 pm ]
Post subject:  Using vacuum to laminate sides
A few months ago I promised to video my method of using vacuum to laminate sides. I laminated a cutaway today, and lets just say I have new respect for legit YouTubers. Laminating a full side uses the same process, but sliding the mold in the bag takes a bit more work.

I chose to do a real-time video, capturing all the quirks, and didn't narrate anything. I have another cutaway to glue-up later this week and will try to talk through the process a bit more there. And hopefully I'll be able to find the vacuum valve on my pump a bit faster. [:Y:]

This was actually a good set to laminate because the walnut had some considerable spring-back. My sides usually fit together much better and I'll tape them to the mold with some light tack tape to keep everything in place while the vacuum pulls. I wasn't able to do that here, and everything still came out just fine.

I'm using a continuous run vacuum pump, a 2x4' standard vinyl bag from Joe Woodworker, breather mesh, and Unibond 800 mixed for quick set. The bags use a brass insert to connect the vacuum hose---I used silicon to permanently set the insert in the bag in order to prevent leaks, and it's a huge improvement (I'm able to pull 25-28 hg).

This is really easy. I always say it's more complex to write about than to actually do. Paint the glue on, fix the sides on the form, slide it in, and let the vacuum pull. [:Y:]

https://www.youtube.com/watch?v=6G6VG475ftQ

[youtube]https://www.youtube.com/watch?v=6G6VG475ftQ[/youtube]
Author:  bcombs510 [ Thu Apr 02, 2020 8:29 am ]
Post subject:  Re: Using vacuum to laminate sides
James, thanks for the video. We talked about this on the phone a while back, I have the same setup. A couple questions:

1) For the brass connector, just some silicone around the outside of the fitting?

2) I expect you left it there for an hour?

3) I use a sheet of breather mesh that is the same size as the bag. I seem to pull 20-21 OK, but I see you used just enough breather around the piece. Would you expect any issues using a full sheet of breather?
Author:  James Orr [ Thu Apr 02, 2020 9:33 am ]
Post subject:  Re: Using vacuum to laminate sides
bcombs510 wrote:
James, thanks for the video. We talked about this on the phone a while back, I have the same setup. A couple questions:

1) For the brass connector, just some silicone around the outside of the fitting?

2) I expect you left it there for an hour?

3) I use a sheet of breather mesh that is the same size as the bag. I seem to pull 20-21 OK, but I see you used just enough breather around the piece. Would you expect any issues using a full sheet of breather?

No problem! I filmed another yesterday where I talked through it more.

1) I specifically used E6000, but I think silicon would work just as well (couldn’t remember the name of E6000 in my initial post). I realized that if the hose were leaning to the side at all, I’d have leaks at the inlet. Sealing it in made a huge difference. I just ran a bead around the insert and pressed it in. I was pulling 28 hg when I pulled it out of the bag!

2) However long it takes the epoxy to set. I leave the cup on the bench and check periodically. Once the epoxy in the cup is hard I’ll take it out of the bag. These two cutaways actually took a few hours because our ambient temperature is still 70 or so.

3) I think you’re fine with the mesh. I used that thin strip because I positioned the mold right under the hose.


Sent from my iPhone using Tapatalk
Author:  James Orr [ Fri Apr 03, 2020 12:31 pm ]
Post subject:  Re: Using vacuum to laminate sides
I thought I’d try working without the breather mesh this morning. Clamping pressure is totally sufficient, but I’m only pulling 17 Hg. I still won’t have any gaps, but it goes to show why the breather is important. I did it’s sister side last night with breather, pulling 22 Hg.

Image
Image


Sent from my iPhone using Tapatalk
Author:  Jim Watts [ Fri Apr 03, 2020 10:45 pm ]
Post subject:  Re: Using vacuum to laminate sides
I would highly recommend using a breather ply, making sure it it covers the area of the vacuum inlet and the area to be bonded at a minimum. It's possible for the bag to shut off on itself and not get much vacuum past that point, even though the bag may look like it's suck down. It only takes a small amount of vacuum for the bag to look good. Also, your gauge will read just fine since it's before the shut off area. It may not mater much in clamping wood, but you can destroy a composite layup without a breather.
The closer the gauge is to bag the better. If you really wanted to know what's going on in the bag you can put a separate port for the gauge in another location on the bag.

Good tutorial, thanks James.
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/