I’ve been doing a little reading on vacume bagging both for laminating and for sandwhich construction (thanks Bert), but still don’t have a good sence of what I need and what I can get by with.
I found a used vacume pump that will pull agout 22.5"HG when connected to a 40gal tank. If I understand this correctly that is about the same as the 75kPa that Bert talks about using.
Does this sould like a good pump for the job?
Incase this one gets away from me, what sources are there for cheap pumps?
How much should they cost?
Please note I want a velatively trouble free system. I want to use it not tinker with it
Harbour Frieght has a pump that attaches to a compressor. It’s quite inexpensive and pulls plenty for surfboards. You probably won’t want to pull much more than 10, especially if your using 1# density EPS. You’ll just crush the blank with more.
You’d want a pump that can pull more than 10"Hg because if you are reusing your bag and it leaks a bit, a pump that can pull more vacuum can make up for it. You can setup a higher vacuum pump to have a relief valve so that your not pull more than 10"Hg.
Also another consideration is the cubic feet per minute (cfm) the pump pulls; how fast it can pull the air out and reach full vacuum. If you have a really leaky bag the more cfm your pump can pull also helps.
But if the bag is good and you’ve got a pump that can pull say for example 24"Hg but only 1cfm, you can pull the bulk of the initial air out with a vacuum cleaner real quick and then switch over to the vacuum pump to keep the vacuum during the cure cycle of the resin.
Dry pumps can’t pull as high a vacuum as oil rotary vane pumps.
You can get good deals on a pump from eBay with patience, but it takes some effort. I have a fairly good understanding of pumps if you need help email me.
hello 4est, i’m no industrial expert but can report from a hobbyist pt of view.
HG is the units I work with and have on my gauge. Even 10 will slowly but surely crush #1 density eps - symptoms are surface of shaped eps will start to become bumpy with the beads becoming prominent. Whole length will shrink a little bit of a period of hours.
However it will definately withstand 10 for a short while. I think there may be some merit in setting to 8 for the first hour and then reducing to 5 or 6 afterwards. I do this for the skin attachment where i am trying to do a strong initial squeeze resin from the glass into the skin to get a good bond. Any comments from the expert sandwich builders on my technique welcome.
however i am very happy with my diaphrapm pump which pulls low cfm but capable of quite a decent vacuum (i got about 14 HG out of it). For the current state of my art, 14 is not needed. I have tested XPS under 14 with no crushing at all, but the problem with the the higher density cores is that achieving a very light board (and strong of course) becomes difficult. So a core containing a reasonable % of #1 seems to be the go for HP surfboards. So right now i don’t need to pull my pump max but at least i have my options open - vac of 14 will also produce a very dry lam. For the non skin attachment outer shell procedure i use just 5 or 6.
maybe i’m neurotic but i take the attitude that a leaking bag is disrtibuting uneven pressure. I have a dedicated shaping room but prefer to vacuum in my residence for lots of reasons - air con, heating, ceiling fans, turbo fan with air sucking thru open windows etc plus ease of checking up on my incubating creation and gloat [sly]. so another problem with the leaky bag hi cfm approach is that pump will cycle a lot and is noisy (i have a fairly quiet pump but its still a bit annoying).
i do an initial suck with a vacuum cleaner to collapse the bag (the low cfm pump takes ages), then in minutes i can achieve my desired pressure with the vac pump.
a nylon bag will last about 3 vacs before its starts to get leaky. I need a minimum of 5 vac procedures per board so 2 or 3 bags per board for what i am trying to achieve i consider affordable.
i have been getting very good results with vacuuming Resin Research epoxy with no additive F and using peel ply. I do use additive F for the fairing procedure tho.
I got my first vac pump off a refridgerator at the dump, for free… works fine, about 24"Hg Max but low CFM so I used to use a regular vacuum cleaner to pull all the air out of the bag first… back then I didn’t use a reservoir tank so I would just let the thing run for hours at a time… it would get hot but that’s ok. I’d just squirt WD40 in the vac line from time to time and elevate the exhaust line so that the oil doesn’t leak out.
Hicksy, Dont butcher the bar fridge mate, summer is coming and beer hydration will be critical! I have just taken possession of one fully opertional fridge compressor today. Hopefully getting in amongst it and bagging a fin over the next week, start small and work up.
I got mine off a fridge repair guy, this avoided butchering a fridges and letting any freon loose in the atmosphere.
I had tried unsuccessfully to get one off another fridge, not that pump was the problem, its the electrics that come with it, that gave me the grief. If your an electrician, the wires make sense and you can simply modify it and hey presto the pump still works when you plug it in. If your like me, you pull it apart, are left with a few wires more than you should have (give yourself a zap here and there) and it doesnt work when you plug it in.
Got sick of trying so I sourced the gear further up my food chain.
I reckon, with the potential to get 1:1 glass / resin ratios (when you know what your doing) it will take some serious weight out of the board. As you know on the hollows, weight becomes a real issue when you are trying to go smaller.
Brennan, good to see Berts post is getting everyone excited about vacuum bagging. I was looking at that very site the other day “cheap little sucker” and have just got a fridge pump and in the throws of getting some bagging done, fin first board to follow.
Let us know what you end up using for breather materials etc, there seem like so many variations on the theme. As usual a picture says it all. I will be buying some plastic irrigation line and valves today to get mine started. A friend adopts this technique, so no need to rush out and buy expensive hydraulic pipinng if the budget wont stretch.
I’m up to corking the rails on this current board so I’ll weigh it when it’s fully shaped and then again with the glass and epoxy on, just to see the difference.
The last board I used 1x5oz each side and total of 400ml epoxy. Really didn’t think that would add too much weight.
I supposed what I should be looking at is using lighter wood, I’m not too sure if vacuum bagging would be much of an advantage to me but I’m sure to try it some time.
Don’t worry I won’t kill the fridge yet, christmas is just about here and I need the room, got a great recyling dump just down the road though.
Gray! Good luck with your set-up. Thank you for safeguarding for Hicksy’s beer! Hicksy, I’m glad you got your priorities straight. I love exploring dumps - people throw away the greatest junk. I just got a sewing machine the other day.
Packaging style bubble wrap makes good breather material… I’ll make sure to post pictures soon… Everybody is trying new things, I’m stoked, I can’t wait to see what people come up with.
hello Brennan that’s great info of how you made the “little sucker”. the more methods we post the better the choices will be for the prospective swaylock vac enthusiast.
as you illustrated on Keith Melville’s R/C (radio control) thread all the info is already out there, but unfortunately very little is in the hands of the board builders who are clinging to traditional methods (not that there is anything wrong with enjoying tradition).
i chose to go with an off the shelf pump coz i made a conscious decision to make that aspect of sandwich construciton easy for myself, but i can see how much pleasure and satisfaction can be gained from making your own vac setup. Fridge pump would be nice and quiet too. Regarding heat buildup, i place a table fan next to my pump.
i did however construct my own hotwire bow. The dimensions/tension I came up with shown on this page.
although the acceptance of the new technology has been dissappointingly slow, i agree that it does mean we are in quite an exciting era - so many ways of doing it and a convention hasn’t been established, so its going to be interesting to see what ppl come up with.
i look forward to seeing your pics, i’m about 2 weeks away from getting my latest project in the water. Final bog tomorrow then start painting. After that i’ll post pics too
hi Mr. J, I agree - I think it’s great everybody is interested in trying something new… and you’re right, if board builders will look around them at what others are doing outside the surfing world, you’ll find some neat stuff. I almost bought vac set-up similiar to yours from Aerospace Composites.
I read your post a long time ago when you vac’ed your first board with that system… thanks for taking the time to write as you went - very informative.
Another note on heat build-up, the fan sounds like a good idea. I haven’t tried this because I don’t need more than 24" Hg, but people are putting fridge compressors in 5 gallon buckets with a little water in the bottom - a cooler compressor is more efficient and will draw a higher vacuum (if you try this, please be careful not to electrocute yourself!).
Also for anybody else out there, if you want your pump to have a longer life and not have to run continuously you can build yourself a set-up, like Mr. Js, like this:
***If your pump is powerful enough to restart under pressure… you won’t need a Mac valve and sub-reservoir. The the vacuum controller is adjusted for your desired pressure and wired to your pump to turn it on and off. You can get the vacuum controller for about $25 and a check valve for about $13. You can use anything solid for your reservoir… schedule 40 PVC, an old fir extinguisher, etc. I bought all the components for my set-up at www.veneersupplies.com - Joe there is great.
one step at a time… swaylocks is ushering in a new era of board builders… lovin it.
On that note, a general note to fellow ebay’ers like myself… this comes from Joe at veneersupplies.com so he is biased 'cause he sells pumps but he’s a good dude and I trust him.
Quote:
“Be especially careful about pumps sold by eBay seller “jenn_bebe_24K”. These pumps are repainted (not too well) and have dry rotted components. Also, most pumps have rubber gaskets, seals, and diaphragms that can dry-rot. Though a pump may look brand new, the rubber components could be rotten. A typical rebuilt kit including a new diaphragm costs $29** (not including shipping).”
Does anyone see a problem with using 6" sched 40 PVC? I already have a bunch of 6". Will the extra diameter make it too week?
Any suggested deviations from the plans described at Veneer Supplies?
How much resevior is recommended for bagging 2 boards at a time?
Note: after you get to the instructions page at the bottom of the index on the left side there is a link to “downloads (pdfs)” this gives you the entire venturi system article in pdf form. Majority of the article is the same for both systems described.
i have been thinking about upgrading my setup from continiouse run to the setup that you described but i am a bit confused about how you regulate the vac… it seems that for wood working they want a vac around 20" but this would crush a foam blank… so i take it you dial in the vac controller to your desired vac, but the info on the controller says it cycles based on + or - 4" of your setting. will this cause a problem with the low vac pressure used for boards? or i guess a simpler way of asking is are you using the system for boards with good results?
