Glen-L.com

Below is some PM correspondence between myself and Bob Perkins regarding vacuum bagging. I expect Bob's info could be of use to others and so am posting our correspondence as a topic. I look forward to hearing any information others can share regarding the vacuum wrapping technique.


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Bob, You sure did a beautiful job on your Biscayne.

I've looked at your site quite a bit along with the Joethewoodworker site and I've a couple questions for you regarding the vacuum wrapping. I've already planked my boat with 1/4" sheet plywood (not the 1/8" cold-molding strips) and now I'd like to veneer over the sheet plywood with 1/4" Sapele planks.
1) Are the 1/4" thick Sapele planks okay, or should I plane them down thinner?
2) Does it matter that I used 1/4" sheet plywood instead of cold-molded strips? The hull design is the Clarkcraft Mariner and the plans call for planking the sides with 3/8" sheet plywood, but I used a thinner plywood because I knew I'd be veneering over them.
3) If I remember correctly, you used GelMagic adhesive epoxy. I know you stated that you used less epoxy because with the vacuum wrapping you didn't need the gap filling, but how much less. Did you trowel it with any specific sized trowel or just kind of spread it on with some sort of flat edge?

Thanks for sharing your woodworking knowledge.

Jeff

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Hi Jeff,

The Joe Woodworker site was very informative.. That said - I did not use the pump that way.
You need a continuous duty vacuum pump with as much CFM as possible. Mine is 4.5CFM.. I wish I had a 10CFM pump. These are called rotary vane pumps. The higher the CFM - the easier it is to maintain vacuum.

I used System 3 epoxy (mostly because I worked at a store where I could get it at cost)
I slightly thickened with Silica to get it to a point where it would flow, but stay in place. Kind of like mayo...

I used a 1/8" notched spreader - You should be able to get them anywhere.

The 1/4" plank should not be an issue.

If you get the vacuum working right - the clamping pressure is very high.

Think - ~14 pounds per square inch.. = ~2000 lbs per square foot.

HTH
Bob

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Thanks Bob for your quick response.

I'm glad you brought up the vacuum pump. I was thinking about using the Venturi type system for the cost savings since I have an okay compressor. Of course cost is always an issue, but not the only issue. I'd hate to set up the Venturi system and realize I'd been much better off spending a little more and doing something else. Here's the press kits that VeneerSupplies.com are now offering - http://www.joewoodworker.com/docs/vacuumpresschart.pdf . My compressor could handle the V2 Plus without a problem, and probably handle the V2 Premium 5 without continuously running, particularly if I got an extra reserve tank. But it sounds like if you were doing this again, you'd just go with the Excel 5 kit (continuous run 5.5 CFM pump). I don't think my wife would be too understanding of spending the $$ for anything much bigger. So, is that your suggestion, go with the 5.5? This pump will be running continuously for many hours whiles the epoxy sets, would that be a problem?

Also, I'd wanted to post my questions to you directly to the Glen-L forum because I think others on the site are extremely interested in your knowledge and experience in this area, but was concerned you might not see the post there, and thus, I might not get your input. With your permission, I'll copy this correspondence on to a Vacuum Bagging topic on the site. I'm sure RobertCugini could add some good additional info to the topic.

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Hi Jeff,

Feel free to ask questions any time. I helped Robert with his vacuum too. It took me a while to figure out it is actually pretty simple. But I did not know that at first

Look on eBay or Craigslist for a Rotary Vane Pump. They are designed to run continuously drawing a vacuum.
Mine is a Gast. You only need a hose to connect straight from the pump to the bag.. No Joe Woodworker tanks, etc.

I do not think you could get a very high CFM with a venturi system.. but I'm not sure.
Feel free to repost. I've answered these types of threads in the past - I'm happy to see people giving it a shot.

The quality of the finished product is remarkable.
Ask Robert!

When I worked at United Airlines, we used the venturi system exclusively when doing smaller repairs to composite aircraft components. Provided you have a continuous air supply at a high enough pressure (say around 100 PSI) you can can get some pretty serious vacuum. That being said, it did require a lot of air and I think the vacuum pump would be a better approach for the home builder.

I did do some small repairs using fiberglass under vacuum. We used release material and bleeder cloth in the process. I remember we would wet the area with resin using a brush, lay the cloth down, wet it some more, add additional layers (usually 4 or 5 per repair) wetting each layer. The we would lay down the release cloth and bleeder material before bagging and bringing up the vacuum. We tried not to over do the amount of resin and for these types of repairs, 3" to 12" in size, this approach worked fine.

My best advice with vacuum bagging is to practice practice practice before doing anything on your boat. It can yield an excellent surface if done correctly and their is no better way to get that kind of down pressure.

_________________
Carl
a.k.a. Clipper

Crafting a classically styled cabin cruiser named "Some Other Time"

http://veracruise.blogspot.com/

Bob,

I'm about ready to start ordering stuff, or at least I thought. At this point I've looked at nearly every link I can find regarding vacuum presses and have seen quite a few threads where you've shared information. Seems you can do many more things with a vacuum press than clamp veneer onto the side of a boat, and I'm kind of looking forward to experimenting with some other vacuum press projects, but first, the project at hand.

What I felt like I needed was a simple vacuum pump or one of JoeWoodworker's systems, some type of plastic or vinyl, a valve stem assembly for hooking the air hose to the wrapper, breather mesh or quilt batting, sealing tape, and mortite (which by the way I bought some of today just to feel it's characteristics)

But I"m confused about the peel-ply. I'm also somewhat confused now about what I'm doing. My concept was that I was simply using vacuum pressure to hold pressure on the veneer until the epoxy cures, we're not fiberglassing here, are we? A few different sites I looked at such as this one (http://myweb.cableone.net/bcanderson/Boatz/Vacuum/Vacuum.html) involve using vacuum bagging over fiberglass mat and resin. I don't understand this application, what is gained? I understand the purpose of resin infusion for making fiberglass parts from molds, but for something like the paddle, it seems you could just squeegee in the resin. So getting back to the peel ply, I can understand why someone doing a paddle like this would need to use it to keep the resin from sticking to the breather material, but why would I need it for just veneering wood on plywood, will that much resin escape from between the joints? While I was thinking peel-ply wasn't needed, in your final post on the woodenboat.com thread (http://forum.woodenboat.com/archive/index.php/t-8602.html), you mentioned the order of layers as vacuum bag material, quilt batting (breather), Peelply, Outer layer of wood, Epoxy, base surface wood. So, I take it that the peel-ply is necessary, but please explain why.

Thanks a Bunch,
Jeff

So peel ply is polyester dress lining essentially. Quite inexpensive at a fabric store (JoAnn Fabric) with their 50% coupons, etc.)
The reason the guys use it on the big layups is that the excess epoxy will squeeze through it and into the breather fabric.
That creates a better glass to epoxy ratio (more strength) and reduces the weight.

The reason I used the peel ply is that I chose to use quilt batting as breather, and while in our construction - not a lot of epoxy squeezes out - when it does.. it glues the breather down. Removal is a pain.. you risk tearing the wood and you can get lumpy epoxy because instead of squeezing through the peel ply and being separated.. it just sits there..

The peel ply and quilt batting can often get a 2nd use too.

I'm not 100% sure it is necessary - it simplifies the work an creates a clean surface with excess epoxy removed by peeling instead of sanding.
If you try it the other way - let us know how it goes.

_________________
Regards,
Bob Perkins

My Current Projects
http://h12restoration.shutterfly.com/
http://nutshellpramconstruction.shutterfly.com/

My Completed project
http://biscayne22.shutterfly.com

I'm all for simple and less sanding. I'll set up my layers just as you did. Thanks.

A few notes about vacuum pumps. If you use a pump that uses oil, you will need a exhaust filter. I tried without one first and ended up with a oil fog in the workshop that was better than a smoke screen. You can find them on ebay, or new ones are not very expensive. I think I paid around 35 dollars for mine. The pump was from ebay as Bob recommended, Its from China, but it has worked well. I connected the output of the filter to a garden hose and snaked that outside the workshop.

Look for "Continuous Run" pumps, they are oil-less and intended to run continuously eliminating shut off valves and reservoir tanks. The K.I.S.S. principle.

If you have an oil fog in your shop, ... "EVERYTHING" has been contaminated with oil. I bought a duel and single Gast pumps off ebay for $90 each years ago, ... the prices haven't changed much.

_________________
Bill

TNT Build, ... On Going, ... http://tinyurl.com/abmae64

The Freebie Zip, ... On Going, ...http://tinyurl.com/at3udss

Super Spartan Build, ... Completed, ...http://tinyurl.com/b488wsz