It should be possible to put a footpump and UV cure resin to vacumn bag without power. Only need to hold it for 3 mins in the sun right?
Get pumping!
The reason I’m thinking about this is that anywhere I can use to make boards are places without power. Most places with power aren’t places I can make a board.
But the whole idea seems a bit farfetched…
What are you trying to accomplish with the vacuum bag?
You might want to make sure that whatever plastic you use is transparent to the wavelength of UV needed to cure the resin. If it is, I assume the bag will get hazy with such concentrated exposure to UV and it being made of some type of plastic.
But also, are you doing an infusion process or something? I would imagine between all the stuff tha goes into making an infused part you’d end up blocking some UV? Otherwise more people would be vac bagging with UV resin since you basically have forever to lay things up and get it in the bag, then you just turn on the UV and cure it. I don’t know though.
You can totally pull a fine vacuum with a hand pump though. I’ve made many longboard skateboards this way. As long as the bag is actually airtight it holds for more than enough time, and if it doesn’t you give it a few pumps every so often.
If you’re looking for cheap and simple…
$20 aquarium pump with the diaphram reversed + 1/4" vacuum line that comes with the pump + a trimmed down lid off a cheapo plastic condiment bottle. You can run that vac continuously (pulls ~10#) and it’s so quiet you won’t be able to hear it 10ft away. I’ve laid a bunch of veneers and wet lams with this rig.
Reversing the diaphram turns this pump into a vacuum. Takes ~5 minutes. There are youtubes on it.
@ kookie
I like the idea a lot. Low-tech vac bagging.
Don’t know for sure. Thin LDPE (polyethylene) and vinyl plastics without UV blockers may allow enough sunlight UV to penetrate.
Simple test, place a piece of the plastic you want to use over a test panel coated with UV resin, while inside. Then take it out into the sunlight and see if it cures.
I’m almost positive the UV will work in a bag because smothering the lam with clear plastic film is one of the methods that are suggested to get a bone-dry cure.
The hard part of bagging a wet lam is getting the film smooth/tight enough to avoid wrinkling. I did it by running the vacuum and breather on the dry side of the board and wrapping the rails.
We still have the question of “why do it?”, though. Unless you’re using a cloth that floats on the resin or a planking/veneer or some thick stack there’s not much weight to be saved. In terms of a conventional fiberglass layup, it’s pretty hard to significantly beat a well-laid hand lamination. I especially wouldn’t bother with a PE or VE resin, not when use of epoxy is so much stronger to begin with. The consumables for vacuum bagging will far exceed the extra costs of swapping epoxy in for a PE resin.
Thanks for posting that Aquarium Pump stuff. I recently brought that up in another thread. Couldn’t remember the details and am glad that you confirm what I thought. Reverse the diaphragm. And you reminded me of using the mustard lid from a squeeze bottle. I was glad to hear you speak about which side you pulled the vacuum from. Dry side. These are a few little details I must remember in the future when I try it myself. I would like to try using the Aquarium Pump to apply a deck veneer after I have cutlap the bottom onto the deck. When I was on Maui, Kenny Tilton used to do this. The glass shop would do the bottom with a cutlap onto the deck. Then Kenny would take the board home and Vacum a Veneer onto the deck. Then he would bring the board back to the shop to be finished off. Laminate the deck over the veneer, hot-coat, fin box, gloss and polish.
Kind of you to say but, no original thinking on my part; I am strictly derivative. I have shamelessly appropriated the techniques of smarter people before me.
I got the tip about aquarium pumps from an “instructables” vid. I don’t remember how I got to the condiment lid except that they’re one-piece and the vac nipple fits a 1/4" air line perfectly. I reinforce the spot where I run the nipple through the bag with a short strip of packing tape on the inside and again on the outside, then cut a hole for the tip of the nipple to come through. Then I spritz the top of the lid with some spray adhesive so the bag would seal under vac and not leak at the nipple. Tape a narrow section of yoga mat of even some paper towels on the rest of the dry side to distribute the vac a bit more evenly and tape a folded towel or rag under the nipple to get the vac flowing.
Obviously I ran a couple of dry runs on my blank (prior to shaping it) to test everything out before I tried to use it with a veneer. It’s strictly a low volume ghetto garage style rig but it’s sufficient to lay a veneer without any drama.
What’s cool about this type of rig is that the pumps are super quiet and are designed to run continuously. The vac they pull is just enough to get the job done without having to get involved with reserve tanks or vacuum guages or switches or whatnot; and also not enough to crush EPS. If you were working on a longboard or SUP you might consider running two of them; one at each end.
For wet lams, Greg Loehr said a long time ago that they tried every combination imagineable and settled on using a fresh raw bag with no peel ply, and no breather on the wet side. Just run the lam a little wet and it would come out of the bag with a semi-finished texture so you could go straight to wet sanding or to a gloss coat. Which also means no burn throughs. The only caution is to not run the lam dry at all or you’ll get pinholes. Oh yeah, and an EPS blank has to be completely sealed or it will act like a giant beather under vacuum; good for a veneer but horrible for a wet lam.
The vac lam without peel ply/perf ply/breather only works well for flats lam on strictly sealed surface. I do it a lot for RC airplanes wings on xps core, never work well on surfboards because of wrinkles. This use of bag is only to get finish surface, or near, out of bag.
With plys and breather bag is use to increase fiber/resin ratio by compacting lam and drain resin, which improve tensil strength/weight ratio but except with lighter than resin fiber, it reduce flexural strengh/weight and shear strengh/weight ratios and give a less watertight surface (ie need more resin to cover for water tightness). When you know that surfboards skins was ruined by puncture (shear stress) and buckling (flexural stress) and skins have to protect foam core from water…
This is why McD’s concrete sealer tip can be so useful – sealing pinholes.
BTW The newer Whisper aquarium air pumps are more difficult to reverse the diaphragm on.
