Veneer Vacuum Question - Woodworking Talk - Woodworkers Forum
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post #1 of 23 Old 01-26-2020, 12:11 PM Thread Starter
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Veneer Vacuum Question

Hi All, first post here.

Background: I'm planning a project for a new cylindrical coffee table, that'll be roughly 40 inch diameter and roughly 36 inches tall. It'll be a hollow 2x4 frame and bendable mdf or lauan plywood wrapped around it to form the cylinder. I plan to veneer the exterior of the cylinder, ideally all at once and after the substrate is attached to the frame so I know the bend is round and fitted to the rest of the table.

I'm new to veneer, but not to woodworking generally. I'm planning to shop for a vacuum/bag setup.

1) Will something this large, in this shape be suitable for bagging in one piece?

2) Any recommendations on a decent setup that doesn't break the bank? I imagine if this works out I'll make one or two more pieces with veneer, but I don't usually have time or the space to regularly woodwork, so I'd like to keep it fairly affordable as I won't get a ton of use out of it, but I also wouldn't want to buy something inadequate for this project either.

Thanks in advance, I'm happy to have found this site!
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post #2 of 23 Old 01-26-2020, 01:32 PM
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If you try this the wrong way you could have a disaster on your hands.It seems you are new to vacuum bagging and it is a great technique,with all sorts of uses.It works best on solid objects without voids within.So that in the example of your table,you would ideally need to apply a bag to the inside as well as the outside.If you just bagged the entire piece and applied a vacuum,the crushing force would be huge and may well collapse the cylinder.If you do the calculation it soon becomes apparent.A full vacuum would exert about 14 pounds/sq inch and you have a lot of square inches.If you can get a bag inside as well as outside and join them it still won't be easy but you ought to avoid the risk of catastrophe.Good luck.
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post #3 of 23 Old 01-26-2020, 05:25 PM
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Try www.aitwood.com for cylinders. Prices look very reasonable.
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post #4 of 23 Old 01-26-2020, 09:06 PM Thread Starter
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So another idea... Vacuum bagging does sound fantastic for most things and I regularly read that it's not worth bothering with anything less for veneering, even pressure and all that. But, does being round open up other opportunities for me? I'm thinking, given it's round, wrapping it in something soft and lining it top to bottom with ratchet straps would give me some pretty damn even pressure as well. Thoughts?

If sticking with the vacuum, the post about not smashing my hollow new table in a million pieces was great information, thanks for that. I could of course make a few jigs and vacuum two half circles before attaching to the frame, but I'd be concerned about the seam on two sides.
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post #5 of 23 Old 01-27-2020, 05:24 AM
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You could also vacuum bag the entire base before attaching the top.That way you could use a corresponding vacuum bag inside and join it around the rim.Mastic tape makes this quite easy and instead of crushing the base,you are exerting a balancing force that shouldn't do any damage.
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post #6 of 23 Old 01-27-2020, 09:38 AM Thread Starter
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Can you clarify this two bag idea I'm having a hard time visualizing it.
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post #7 of 23 Old 01-27-2020, 11:47 AM
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Quote:
Originally Posted by Clearlynotstefan View Post
Can you clarify this two bag idea I'm having a hard time visualizing it.

I'll do my best-imagine vacuum bagging a hat.If you put a bag over the outside and seal it down to a flat surface,atmospheric pressure will make it collapse when the vacuum is applied.If you use a second bag inside the hat and conforming to the surface and joined to the outer bag around the brim the force is applied to the material only and doesn't collapse the hat.Is that clear enough?
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post #8 of 23 Old 01-27-2020, 01:05 PM
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There are alternatives.
1 MDF or Plywood - Cuts to make bending possible
2) SonoTube - Round columns used for woodowrking Look Exactly like the kind they use for concrete forms to make concrete columns.
3) Contact cement using veneering with a backing - much easier than you think
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post #9 of 23 Old 01-27-2020, 02:13 PM
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I know this isn't what you asked, but if I was doing this, I would switch to paper-backed veneer and use a good contact cement (not the waterborne stuff).
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post #10 of 23 Old 01-27-2020, 02:50 PM Thread Starter
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Quote:
Originally Posted by Tony B View Post
There are alternatives.
1 MDF or Plywood - Cuts to make bending possible
2) SonoTube - Round columns used for woodowrking Look Exactly like the kind they use for concrete forms to make concrete columns.
3) Contact cement using veneering with a backing - much easier than you think
Thanks, I'm not concerned about making the substrate work, flexible mdf or lauan plywood will easily give me a nice clean cylinder. The veneer though, that's all new to me. I had been reading up, possibly in this very forum and saw a lot of people saying not to bother with contact cement or any other "half-assed" approach and skip veneering entirely if not using a vacuum, which of course seems extreme, but hey I'm not the expert on this process!

Obviously if I could get away with cement and ratchet straps and still get a high quality long lasting result, that'd save me good money and time.
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post #11 of 23 Old 01-27-2020, 03:41 PM
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No ratchet straps. Once contact is made - thats it.
Nothing else to do except trim off the overhang. With contact cement, it dries on contact. No waiting time, just apply your finish if your want to.
It will take some practice, but not all that much. Just take your time . Flexible MDF or Bending Luan usually still need a sub-straight or some kind of framework to attach to.
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post #12 of 23 Old 01-27-2020, 03:44 PM
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@Rick Christopherson is correct. I forgot to add that part - the Solvent base stuff NOT the water base.

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post #13 of 23 Old 01-27-2020, 06:16 PM
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I think you will have a lot of trouble trying to vacuum bag a full cylinder in one shot. Try traditional veneering with hot hide glue. Much more forgiving. If you must try the vacuum method, look at Vacuum Pressing Systems information on line. You can buy plywood or paper cylinders. I wouldn't use bendy plywood over a frame. It rarely bends uniformly. We do use kerfing mdf on some curved work.
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post #14 of 23 Old 01-28-2020, 03:48 AM Thread Starter
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Quote:
Originally Posted by Tony B View Post
No ratchet straps. Once contact is made - thats it.
Nothing else to do except trim off the overhang. With contact cement, it dries on contact. No waiting time, just apply your finish if your want to.
It will take some practice, but not all that much. Just take your time . Flexible MDF or Bending Luan usually still need a sub-straight or some kind of framework to attach to.
Indeed there's a fairly robust frame including a few "tiers" of full solid circular wood at the bottom top and middle. The rest of the frame is an octagonal frame . 2x4. Just trying to figure out the best way to get veneer on something in this shape and size. Will look into the other non-vacuum suggestions below.
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post #15 of 23 Old 01-28-2020, 11:18 AM
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Quote:
Originally Posted by Rick Christopherson View Post
I know this isn't what you asked, but if I was doing this, I would switch to paper-backed veneer and use a good contact cement (not the waterborne stuff).
Agreed-and it would eliminate the difficulty of joining lots of leaves of veneer.I also like to go over such a piece with a veneer hammer to be sure it is really down.
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post #16 of 23 Old 01-28-2020, 09:08 PM
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Your easiest option would be to get PSA backed veneer. If you haven't done any vacuum pressing before, you're starting at advanced calculus instead of basic addition. If you still want to go that route, I'd suggest you check out Darryl Keil's books and videos.

I personally wouldn't use contact cement for veneer but to each their own. It can be hard to not get lumps, especially with the thinner 10mil paper backed veneer.

I do not prize the word "cheap." It is not a badge of honor...it is a symbol of despair. Cheap prices make for cheap goods; cheap goods make for cheap men; and cheap men make for a cheap country. ~ William McKinley
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post #17 of 23 Old 01-28-2020, 09:59 PM
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Quote:
Originally Posted by J.C. View Post
.......................I personally wouldn't use contact cement for veneer but to each their own. It can be hard to not get lumps, especially with the thinner 10mil paper backed veneer.
Contact cement is as easy as it gets. Just do a dry run or two before you add the contact cement. Then when you apply the CC to both surfaces with a contact cement roller, you will know exactly how you are going to do it.
If by chance you really screw it up, pour some lacquer thinner into the gaps and peel everything right back off. Wait about 15 to 20 minutes and re-apply more contact cement to both surfaces and try again.
As for lumps and bumps, I have no idea what you are talking about. If you use the proper roller for contact cement, all should go well. A roller for contact cement looks just like a paint roller, but it is made for contact cement. Even if you plan to roll it on, buy the 'spray grade' stuff It is thinner and easier to roll. If you never did this before, dont buy the regular roller or brush grade and thin it yourself. You wont know how much thinner to use and how thin is thin.

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post #18 of 23 Old 01-29-2020, 02:49 AM
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Thanks for the tip on lacquer thinner, I could have used that in the past
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post #19 of 23 Old 01-29-2020, 01:03 PM
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Contact cement will always desolve and soften up even after 20 years. Part of my arsenal was always a bunch of hypodermic needles of various sizes to inject into cracks and peel off old veneer or plastic laminate, or to repair an old glue bond. The needles are also good for injecting adhesives into small cracks.

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post #20 of 23 Old 02-01-2020, 04:20 PM
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I buy my syringes and needles at the farm store. Available in many sizes.
Never use contact on un-backed veneer!
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