crazy vacuum bagging ideas

If you have a pressurized tank on top of your prebuilt skins, you get higher pressure than what straight vacuum can provide, but a professional setup like that (autoclave) is kind of expensive. Building a pressurized metal tank that will take a surfboard or a skin is not easy either. So what if you just placed the whole vacuum bag when prebuilding skin inside another plastic bag made out of a thicker material, sealed the outer bag and attached a compressor to it? Any extra pressure in this bag is extra pressure on the skin. And if it fails with a small leak or explode like a balloon, no harm done to the skin in the bag, it’s still under vacuum pressure. Also, since the pressurized bag does not have to conform to any shape, it can be made out of really thick material.

High pressure crushes foam. Vacuum infusion require high pressure. but if you build out rails and skins you have sealed the foam off. If you have a vent this sealed core, you can attach a compressor to it. Now you have a pressurized container, put it inside your vacuum bag, now it supports the high pressure from high vacuum required to do resin infusion.

Any takers?

yeah i love the idea of having the core at normal at pressure while vaccing skins

ill have to digest that some more

but i think your onto something

It would be difficult to keep the core at regular pressure, as it would not be sealed until the resin had cured,(The air could just bubble out into the bag) and that woud defeat the purpose of vacuum bagging it wouldn’t it?

High pressure crushes foam.

And makes surfboards that deflect bullets, but ride like shit.

Vacuum infusion require high pressure.

Not necessarily. The process is dependent on several variables including the most important one, resin viscosity. RI can be done with moderate pressures but it requires a good strategy and careful planning.

Ive said it here many times…high pressure is way over rated.

There, Ive said it again :wink:

Haavard! You have too much spare time to be thinking up crazy things like this!! :wink:

Seriously though, I think you’re on to something… on to something neat… I think it would work well on infusion to perimeter balsa rails… Especially if you are infusing them into a mould under pressure… (as in, wood in bag, infused vacuum, vac bag in rail mould under pressure… )

Sorry to be a fun killer, but where is the benefit?

I love this kinda stuff, and if you can give a real benefit of making a board this way, then i’ll probably think about it 24/7 until i’ve got it figured out, or I go (more) crazy… :slight_smile:

Cool stuff, but what problem are you trying to solve?

I sort of hope you don’t have a good reason, cos my brain is wizzing around so much I can’t sleep as it is!!


P.S oh man, now you’ve got me thinking about it, trying to solve something I don’t have a use for… got some ideas already!

I have to agree. RI is easily accomplished at low enough pressures to avoid crushing the core. No need for higher pressures at any rate. The best you can realistically hope for over a well planned low pressure RI is another couple % fiber volume. Not worth the trouble.

Haavard, you are on a roll with all these ideas (fins, vac, etc). Too much caffine? Keep 'em coming!!

Oh Boy, my pet subject!! One big benefit of infusion is that it removes the need to sand rails and laps. Get the setup right and all you have to do is take the board from the bag and add glosscoat. OK it is fiddley but I REALLY HATE SANDING!

I could not agree more…sanding sucks.

But you can still RI at lower vacuum levels.

well id rather pay someone 40 dollars to sand the whole board

then to muck around with that extra stuff

i use a bag once and that it

i can jump up and down on my boards

they dont pressure dent

and ive built as light as 2 kg/4 pounds

also i dont need to use any disposables

in fact i reckon if they were just sanding the rails i could prolly get it done for 15$nz

u do the sums

if sandings the only reason your prolly wasting your time

what pressure?

low density styro deforms between 7 and 10 hg

can you do infusion at that pressure?

I’d love to hear more about low vacuum infusion… can you elaborate?

Despite my negativity in my previous post, it does intrigue me, but I don’t have the R&D budget (try zero $!) to spend.

Unless there is a very attractive advantage.

Infusion will give you a slightly lighter stonger laminate, and little sanding, but at the moment, my time as labour is worth less than the cost of a new vacuum pump, equipment, and many many test panels worth of materials!

Savings in build time are negligable unless you can figure out how to do a lot of steps in one go.

I’ve decided on my mission in the field of compsands: The poor mans path to performance!

Should be fun figuring out backyard ways of doing things that result in production speed/quality boards.

Wish me luck…

I tell you what, give us the run down on low vacuum infusion, an i’ll adapt it to fit the budget board builder :slight_smile:


I am sure I’ve missed something…

My understanding of compsand boards (which is not great!) is that a higher density foam is vac bagged onto an EPS core, the shaping is completed and the balsa rails attached, shaped and the whole lot is glassed.

If this is right then you must have a vacuum pump, if so you too can use infusion.

You’re right it is a fiddle, it takes a lot of practice and yes, there are comsumables. However how does this scenario grab you…

4 boards shaped and dry glassed, in a bag, no rush with resin cure times. Suck the air out and make sure all is set-up OK. When you are happy mix 1 pot of resin, open the feedlines and 10 minutes later you have perfectly resined boards. Allow adequate cure time (previously worked out for the temperature you’re working at). Open the bags, glosscoat and there it is…4 boards in the time it takes to make 1.

It’s not for everybody, but if you are already bagging stuff have a go on a sample and see how good life can be.

PM me if I can help.



4 boards shaped and dry glassed, in a bag, …open the feedlines and 10 minutes later you have perfectly resined boards. …4 boards in the time it takes to make 1.

Hey Rik, Re the first comment - how long does that take? Re the second comment - 10 minutes seems damn fast! (Im assuming your resin front flows from one side (rail) to the other?) One thing that seems missing is the comparison to PE resin. Speed of production is excellent, thats why glass shops resist changing to epoxy. Not promoting its use here, just trying to keep things in proper perspective.

Polyester, vinyl ester, epoxy… you can get any resin you want for infusion. I infuse boats with polyester and boards with epoxy. With experience (and lots of experiments) you can modify an epoxy’s gel time to almost whatever you want. Loads of data from experiments is needed. Vosper Thorneycroft (V.v.v. serious ship / boatbuilders in the UK) record every infusion they have done going back 15-20 years. They look up the flow rate for a given laminate stack for a given resin and temperature and sequentially infuse big stuff. The resin injected first may have gelled before the final section in injected…

So far as to how long it takes to dry lay-up a board…I’m still an amateur at boards but reckon I could glass (2 layers top and bottom) and bag a board in 1 hour. 10 minutes infusion, 20 minutes gel time. I might be lying!! I’ll time myself (and use a GPS…ooooooooooops that’s another thread) next one I do and post pix and video.

You do have to use a low viscosity resin don’t you though? I remember your infusion thread you mentioned that?

So you wouldn’t be able to use say Resin Research or any of the other surfboard specific resins that are out there. I read a while back that Greg Loehr was working on a surfboard specific infusion resin but I don’t know if anything came of it.

Or can you modify a given resins viscosity by applying heat as it’s injected, or…?

I’d love to be able to use RI, just for a cleaner working environment if nothing else. The extra consumables you use might be offset by not having to hotcoat. Just done some experiments with cheap polyester fabric as perf-ply, and it’s the best finish results I’ve got so far, next up is a full vac bag lam with perf-ply, blotter and breather.

Yes, you will need lower viscosity resins (PE, VE, or Epoxy).

Yes, RI is possible at 10 mm Hg, with the right setup and resin. You will need an extended gel time and would need to place the distribution media strategically, but those are minor modifications.

Yes, it will take a bit of trial and error and fiddling, but it is time spent that may pay off for you in the long run. If you have a vacuum already, then it may be worth a couple hours of experimentation. Low viscosity resin with an extended gel time, 3’ of glass fabric, small simple bag setup and a stopwatch.

The resin manufacturer or vendor may prove invaluable as a source of R&D. Many of the resin tech guys are top notch and most can easily steer you to the right mix and may even suggest methods for thinning their resins. Don’t hesitate to call and pester them. They act like they don’t love it, but they do :wink:

Certainly low viscosity resins are best. However I have used standard WEST resin with a slow hardener and raised the temp by standing it in a warm water bath. The laminate stacks used for boards are so thin that with thoughtful mesh positioning (and using a good mesh) you should be able to infuse with standard resin. Part of the trick is to infuse ACROSS the board not along it’s length. Get the resin to travel the shortest distance possible. Best of all is to infuse along the centreline on both sides, sucking along the edges, resin only travels half the board width (plus a little for the rails). You have to be clever doing this as the resin injection pipe cannot lie directly on the board or it will leave a surface impression. A trick here is to put a thick “tube” of mesh on top of the distribution mesh which in turn has peelply between it and the glass. This acts as a artery along which the resin flows before spreading out in the distribution mesh. I’ll try and post some pix if people are really interested, otherwise you’ll just have to wait 'til I do the next one and cash shortage will delay that!!

Have a look at this site:

Give it a try, it is so cool.


You’re thinking Haavard…don’t let others think for you…if it doesn’t work…then you know to change the formula or dump the project all together,but you have to get there first before you can make a valid decision on it…R&D My man ! Herb