Ed 143 Posted February 14, 2012 Share Posted February 14, 2012 I'm embarking on a boat building project, 28' mark, and need a vacuum pump for bulkheads, hulls etc. I'm just using it for vac bagging, not infusion. I've had a bit of a look around for vacuum pumps but need a bit of advice The gold plated answer would be something like the 20/2 from vacmobiles, but one of these things can infuse an entire 60' hull in one hit, so a little overkill for a home build At the other end of the spectrum there is the $450 2.5cfm chinese vacuum pumps on tardeme, but I don't know if this is going to be enough to do the job Any comments or advice would be appreciated Cheers Link to post Share on other sites
chic014 0 Posted February 14, 2012 Share Posted February 14, 2012 I can highly reccomend vacmobiles pumps and all the associated fittings they sell or can make up for you. It's really nice to have an elegant, simple solution without everything being held together with tacky tape. They guys there know their stuff and are really helpful. We use a 20/2 and a bigger style pump along with lots of their catchpots and fittings and sensors. A 20/2 is around $6k if I remember correctly. Although if you're just doing homebuild stuff, especially not infusion it probably is overkill. I have heard of people doing stuff with fridge compressors but not entirely sure what vacuum thaty can pull. A Vacmobiles 20/2 can typically pull 10mbar. Remember the power of a pump is pressure times flowrate. So for the same power you can get a pump that has high flowrate but doesn't get very low pressure e.g. a vaccum cleaner, or something that has low flowrate but can get to a very low pressure e.g. a super high vacuum pump. So it is a balance of getting to low vacuum but in a reasonable time. Vacmobiles pump has a free air displacement of 10.6cfm (i.e. that is the flowrate when there is no load, when you first turn on the pump, it will slow down as the pressure in the bag gets lower) and that trademe one is 2.5cfm but you really need to see the pump performance curve to see how they perform at lower pressures. Whatever you do make sure you use a catchpot as the last thing you want is resin getting in the pump Link to post Share on other sites
Ed 143 Posted February 14, 2012 Author Share Posted February 14, 2012 Fridge compressors are a bad idea as they are never designed for continous duty and tend to go pop after running for a couple of hours I know I need a vane axial pump, just a bid of guidance about what size and who from. Link to post Share on other sites
Guest Posted February 14, 2012 Share Posted February 14, 2012 I bought a $500 chinese pump off trademe for doing all the flat panels and other stuff on my Farrier 32 and it has been great, no issues. Can't remember the specs though. Link to post Share on other sites
Ed 143 Posted February 14, 2012 Author Share Posted February 14, 2012 Did you do the hulls with it as well? Link to post Share on other sites
Guest Posted February 14, 2012 Share Posted February 14, 2012 No, decided it was too much hassle short handed. Link to post Share on other sites
wheels 543 Posted February 14, 2012 Share Posted February 14, 2012 A simple and cheap compressor is all you need. Fit a tube to the suck side where the airfilter is. A proper vaccum pump can be expensive. Link to post Share on other sites
Guest Posted February 14, 2012 Share Posted February 14, 2012 a fridge compressor or a battery of them will work funnilly enough if theyre well used, as a vacuum is created all your left with is ozone which is superconductive.......hence burnout, learnt this the hard way when a sparky turned on a new system in vacuum...... under 3secs and poof burned out compressor, however, did use , as have several others, a dome compressor as a vacuum pump for sucking out systems trick was to always use a used comp as a vac pump as they apparently varnish up and insulate....... so get a few and battery em up Link to post Share on other sites
Ed 143 Posted February 14, 2012 Author Share Posted February 14, 2012 A simple and cheap compressor is all you need. Fit a tube to the suck side where the airfilter is. A proper vaccum pump can be expensive. Won't this end up knackering the compressor?, they are designed to blow not suck, and discharging to atmosphere, not a load for hours on end can't be healthy either! I'm happy to buy the right piece of kit, it's small change in comparison to the rest of the build, and I can either flog it afterwards or use it on the next project. I just don't want to spend more than I have to Link to post Share on other sites
Guest Posted February 14, 2012 Share Posted February 14, 2012 There are quite a few pumps drifting around the marine scene. I'd think if you asked around, didn't want one for a long time and had a stray bottle of rum or 2, you may just be able to borrow one short term. Or I hope so as that's the plan I'm targeting next month Tried Adhesive Technologies. Something in my head says they have a couple you maybe able to rent. But my head could be wrong. Link to post Share on other sites
wheels 543 Posted February 14, 2012 Share Posted February 14, 2012 Won't this end up knackering the compressor?, they are designed to blow not suck, and discharging to atmosphere, not a load for hours on end can't be healthy either! No they will handle it just fine. They are simply a piston going up and down. A valve at the top which makes sure the air sucks in one port and gets blown out the other to the tank. In fact in manyways, it is easier on the compressor because once the vacumm has been created, not alot of air moves through the cylinder and so not a lot of heat is developed. Heat is mostly developed by compressing the air. No air, no heat. The only thing that will happen, is that instead of oil being pushed down past the rings, it will get sucked up past the rings and pushed along to the tank. No biggy and in fact quite good for the cylinder. But you will want to keep a closer eye on oil level. The tank drain valve wants to be left open so as the air can escape and also any oil/water can escape and you will want a catch tray or container under the valve so as you don't have oil on the workshop floor. I have used this method to suck moisture from a hull. It ran for a week. Link to post Share on other sites
TimW 1 Posted February 15, 2012 Share Posted February 15, 2012 About 20 years ago I got myself an Oil Cooled Rotary Vane Vacuum Pump. It has a capacity of 48 cubic metres an hour, is a 3 phase unit and cost about $3500. I have used it hundreds and hundreds of times and its been fantastic. If I was getting a Vacuum Pump I would go the same way but it could be smaller 25 cu m/ hr is sufficient and you could contact Gardner Denver in Silverdale who are agents for Elmo Rietschle. They have some nice units which are not that expensive. Vacuum Pumps work best (i.e. the Oil Cooling works best) when they are pulling a decent vacuum. If the Vacuum bag is leaking badly they can over heat. They also can overheat when vacating a large amount of air from a bag. To get a good Laminate with the least amount of air you want a really good vacuum. Compressors with Venturis are good for Vacating Air but do not work as well at pulling a really good vacuum. Another erasy way to vacate air is just a regular vacuum cleaner. Link to post Share on other sites
wheels 543 Posted February 16, 2012 Share Posted February 16, 2012 Only problem with the vaccy cleaner is that they must have air to keep cool. Once the vaccum has been created no air is moving through it and it will overheat. Link to post Share on other sites
Guest Posted February 16, 2012 Share Posted February 16, 2012 Interesting topic, I had a look on trade me and this would be my buy for what you want to do http://www.trademe.co.nz/business-farmi ... 957056.htm Mines single phase and most likely the next size up ( or two ) size stickers all gone but does have a .75kw motor. I got mine from richmann engineering in rylock pl east auck. Link to post Share on other sites
chic014 0 Posted February 16, 2012 Share Posted February 16, 2012 That pump is what's in the vacmobile 20/2 I think without all the nice, well made chassis, connections, catchpot, bleed valves etc PVR made in italy I think And no I don't work for vacmobiles, I just highly recommend their products and service. A simple thing done well that work's reliably, that doesn't require ANY tacky tape to remain leak free! Link to post Share on other sites
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