Vacuum Debacle

Well my first foray into vac bagging has been a bummer. \

I tried to bag a balsa deck onto a PU shaped blank. Titebond III was the adhesive attempted. “Dry run” went great. Balsa was sucked down great, pump worked great, bubble wrap breather great. Wet run… not so great. I can’t seem to get nearly the same vacuum pressure, the open time of the glue was probably too short also. It will be salvagable but, oh well. Pump running at 7-8 hg–continuous run and preset pressure. One thing I noticed was that the balsa warped alot after applying glue. I wonder if this is contributing to the problem?

Ok… the glue was still soft enought that I peeled the skin off and applied more glue. I prepped another bag and we’re off again. Perhaps there is hope. Damn, that first vac looked so good! Oh well.

Success!!! The new bag works much better! The only problem I perceive is that is the warping effect of the glue cause some of the balsa pieces to overlap and stick up a little.

Here’s what I’ve learned so far:

  1. Keep the vacuum line connector a good distance from the edges of the bag.

  2. Mastic vacuum tape sucks–I’m going to invest in a quick sealer

or two.

  1. the ACP vacuum tubing works really well.

  2. A continuous run pump that is preset to 6 hg gives sufficient vac pressure for applying balsa to foam.

  3. Pull down time with my little pump is quite slow. Consider that when choosing an adhesive. The shop vac initial pull is probably a really good idea.

  4. Try to avoid super tight butt joints as they might create balsa overlap in the bag.

How long should I let it stay in the bag, I wonder. Glue is titebond III. It’s inside my office at approx 72 degrees.

It’s hard not to stare at the bag. hehe.

titebond site says clamp time should be 24hrs for a stressed joint? WTH? Do you guys think I need to do that? Benny? Widow Maka? Smart glue people?


"4. A continuous run pump that is preset to 6 hg gives sufficient vac pressure for applying balsa to foam.

  1. Pull down time with my little pump is quite slow. Consider that when choosing an adhesive. The shop vac initial pull is probably a really good idea.

  2. Try to avoid super tight butt joints as they might create balsa overlap in the bag. "

  3. Yup…depending on the thickness and density of the balsa. Slightly higher pressures and you won’t have to worry about hte “warping” you observed.

  4. Easiest way to do this iz via a “vacuum reservoir”. Basically, a big tube/canister/leftover air compressor chamber that you evacuate down to the pressure you’re planning on working at; place this in-line between the pump and the bag; put a valve that can cut off airflow to the eventual bag in after the reservoir and light up the vacuum. Set-up and connect your bag; flick the valve and watch the air go away faster than you can say shazam.

  5. Nope. Set your joints tight or get ready to patch your work and fill the voids afterwards. A little tape or superglue goes a LONG way. Trying to get the wood to wrap around too tight a curvature causes problems as well; plan your laminate carefully. The dry run was a good idea.

question…why are you using tightbond? better off using the same resin you plan on lamming with…either epoxy or poly…


Cool… thanks for the insight. One thing I’ve noticed about the vac bag thing is that people really share alot of info in certain areas and then clam up in others. I wanted to try to give insight into my experiences as I went. I was hoping more experienced baggers would step in and clarify my misconceptions.

I know there are many lurkers out there agonizing over how to go about their first bagging effort. I read and read and read and still have numerous questions. I want to contribute to this body of work.

Now, I must clarify that this effort represents an experiment. I have been accumulating supplies to build an eps/balsa sandwich board for some time. I wanted to wade into the arena gingerly so…

I happened to have a shaped blank in my shed that I was making for a friend and I figured it my give me a nice little vacuum test run. I asked my buddy if he’d like a wooden deck inlay and he was stoked so I went out and got more balsa. This gave me some experience in assembling a skin, setting up and screwing up my bag, and operating on ‘the clock.’ I didn’t want to burn any extra glass or resin on this ‘trial run’ vac bag. It certainly would’ve yeilded a better result I would think. I did a similar board awhile ago. On that project I did a balsa deck over an eps homedepot blank. I applied the deck with elmers white glue and bagged it with tape. It came out well and really impact resistant.

My goals on the instant project are mainly experience related and aesthetic. Additionally, I think this feature will make the deck more impact/dent resistant. I chose titebond III because it seemed similar to the elmers white in consistency and spreadability, has a water resistant feature, and a decent open time. My archive search on the subject indicated that certain members had used the glue for stringer and tailblock glue ups with success. I did a few tests with scrap balsa and scrap PU foam with mixed results. Ultimately I just charged it. We shall see. As for pics, well I’ve been derilect in that respect but I’ll grab my camera later this afternoon and pop a few.


I’d go along with Great White on all this. We use a low tack tape to ensure edge alignment when doing veneers under a vac bag. Everything gets rather slippery when the glue is applied and vacuum pulled. As a last resort I’ve stapled through a piece of webbing, through the veneer and into the blank to stop slipping. One then pulls the webbing and out pops the staple. The holes left virtually disappear when resin and glass applied.

The Gougeon Brothers do good stuff on vaccing veneers.

Love the idea of using a vac reservoir, will also try that next time.

That sounds alot like the way Cobra in Thailand does vac’ed windsurfers, they staple Peelply over the laminate and vac it, when epoxy is hard, just rip the peelply and there you go…

Will the titebond glue cure properly in a sealed vacuum? Seems like it might need some air.

Oh man, I just gotta share one of my attempts with you, just to make you feel better!

So, I was attempting to bend quite a thick piece wood around the rails, thicker than usual, about 5/8".

Did a dry run, tape would roughly into place with cloth duct tape, shove in bag. worked great.

So on with the real thing…

Was using Gorilla glue, so I put my gloves on. Of course I didn’t use gloves for the dry run, there was no glue.

What I didn’t realise is that duct tape stick to the latex gloves like nothing else… so funny trying to pull it off my fingers.

Oh, stuck one hand, now it’s stuck to the other. scratch you head, now it’s stuck in you hair.

After struggling for a while a got rid of the gloves, and up to my elbows in GG. That stuff never come off your hands.

So I tape on the rails, and i’m almost done, i’m on the ground wrestling the thing crocodile hunter style, and I manage to drop the roll of tape, which does what rolls do, and rolls away…

I have to let go of the board, which promptly springs apart again, while i retrieve the tape.

Eventually get it into bag, pull vac… pull vac… pull vac… oh crap, the breather is not over the hose attachment!

Open bag again, tape comes apart, wood springs off rails. Swear and kick something. fix breather.

Tape up rails AGAIN, then… run out of tape!

So I jammed it all in the bag, the G Glue bubbling away everywhere by now, and suck that puppy down as hard as I could, in anger.

squeezed and push the rails pretty much into position eventually, not too bad.

But I destroyed my vac bag by being violent with it on a rough concrete floor, so theres pin holes everywhere!

Spend the next hour putting tape over all the holes, desperately trying to hold vac and keep those rails sucked up tight!

Anyway, when it came out of the bag there where gaps everywhere, so I had to pull those in with G clamps, pretty slow process.

Don’t feel bad, my next stuff-up is sure to be just around the corner.


If you check out my “EPS plwood fun gun” thread you’ll see photos of my vacuum attachment to the bag. It was the top of a glue bottle with the spout thingy pulled off. It worked absolutely perfect, both for the shop vac (initial pull) and then for the vacuum pump. Just a stroke of luck, not ingenuity on my part. Also I did everything on the cheap- 4 mil Depot plastic sheeting, masking tape, bubble wrap…and everything went without a hitch. Beginner’s luck? I’ll find out when I try my next project this coming summer.

Why are you using glue instead of epoxy? I found that the glue once for once was more expensive.

Also, I’m not sure if this is sound advice (maybe an expert can agree or disagree) but you could try damping the balsa on the side you’re not laminating to prevent it from warping or curling. Remember wood when it gets wet will try to straighten out the grain.

Been there did that and worse…

oh the trial and tribulations…

the horror the horror of it all

not being prepared that is…

some notes from the sidelines…

  1. I think John may be right about titebond and air kind of like elmers

  2. a couple of strips of blue or green tape to temporarily hold everything togethor especially those “delicate seams”.Then a

sheet of thin 2-3mil plastic around the whole thing pulling tightly from rail to rail down the middel to pull the rail edges in and securing with more blue tape or like Tom Sullivan demonstrated, brown packing tape on a roller. The thin plastic will pull in all the loose wood semi tightly until the vacuum can take over.

  1. Shop vac the initial pull and have your tank primed with a stop value (locking pliers) use the shop vac to prime the pull so you get a clean even seal over the wood and around the rail line. Making sure you don’t have any plastic getting sucked up under the wood. (this happens alot along the rail, nose and tail seams). Pull the vac pipe and seal the bag.

  2. hook up your pump and release your stop valve and place the whole contraption on your racks so you can pull the plastic down and under the curve or the rail joints so you can get maximum pressure on the wood surface your binding to the foam. Make sure you smooth out the bag surface as smooth as possible over the wood surface. And don’t be afraid to suck. We pull 10-15lbs some times to merge the 3-4 lemenets togethor.

  3. a slower binding agent (like system-3 slow epoxy) helps but I’ve done this with 5 minute epoxy glue as well you gotta smoke thru the steps though before the glue start smoking… This weekend my bro just did his balsa top on his new HD hull old school CMP style with just resin and no glass. He want’s to put more glass on the outside instead.

any where from 10-12 hours preferable over night with epoxy and glass I don’t know about white glue but probably shorter with expanding PU glue. When I bagged koa veneer over balsa boxes last year with 5 min epoxy it took about 15 minutes before I unbagged them and did the next one.

Probably half the folks here understand what I’m talking about

For those that don’t go get Tom Sullivan’s video on vacuum bagging and you’ll see how it’s done.

Great suggestions, thanks. I appreciate the condolences as well.

The titebond website discusses vac bagging with titebond iii so hopefully its cool.

I wanted to use roo glue for this… that stuff seems great but difficult to get in my area.

i think mastic rocks

if it dont have cloth on the inside it not actually a sandwhich btw

have you guys actually read berts post

thats the start !

everything he does is done for a reason

get that right and you will figure it out

just use epoxy and cloth

Sorry for the confusion, but as I indicated, this project is intended as practice for a sandwich board. The timber deck is on a PU blank and I glued it on for aesthetic reasons. I’ve done it successfullu in the past with tape but wanted to play with my new vacuum bag stuff. The glue cost me a dollar or two. I agree that a sandwich construction would yield different properties.

The board is now out of the bag. I left it in for 23 hrs after speaking with a titebond customer service person–thats really nice. We talked about the project and she gave me her thoughts. It appears that it worked. The balsa seems well adhered and is conforming to the more aggressive curves. So perhaps this thread is inappropriately titled. So… further observations:

  1. Next time I assemble my skin, I’m going to try CA glue rather than the blue tape. I peeled it all off after I got the board out of the bag, but it had been on there about 2 weeks and it messed up the wood a little. Some of the more recently applied pieces were fine.

  2. I believe I’ll limit my titebond III use to rail application henceforth. I don’t know if I could’ve gotten away with less time in the bag, but 23 hrs is a long time.

As far as the setup I used, it was the EZ-Vac from ACP. It came with a short piece of tubing and bought a cool little bag connector. The mastic tape certainly works well, but it takes time to apply properly (at least at first). No gauges, tanks, or anything. The pump ran for 23 hrs and seemed fine. It was alittle warm but not anymore so than 4 hours into the job. It is extremely quiet (not quite as loud as a refridgerator) and it seemed to be ‘idling’ once full vacuum was achieved.


nah its all good with the experiments

i want to try some hell crazystuff myself

i was just surpriuzed you know

styro and epoxy are cheap

pu blanks are not

pu or xps do not have desirable qualities for sandwhich cores

experiments snd practice are all good though

hey the CA glue idea is a good one

i just cant seem to buy it in tubes bigger than 2ml

I made a balsa deck on a poope blank.I used CA glue on the butt seams. And Elmers version of GG to glue to the blank.The Elmers Ultimate urathane glue was the winner in all of my stregth tests, stronger than epoxy, Tite Bond, poly,white Elmers, and CA glue.And the bag time was three hours@9HG.

I had one home made bag that didn’t work and had to through away the bottom skin.Some 40grt sand paper will smooth out the balsa in no time.Do you have any pictures?


Here’s the board 24 hours after removing from bag. It’s sitting on my conference table. Everything still appears to be well adhered. The continuing plan will be to mask the deck balsa with tape and butcher paper, then lam the bottom with six ounce and dark blue tinted RR. Lam the deck double 6, set fins, hcoat, light blue pin, gloss coat and so on.

The finished product will go up on the hohar research section.