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Using HVAC pump for vacuum bagging (doubts)

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Al_Kiter
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Using HVAC pump for vacuum bagging (doubts)

Postby Al_Kiter » Wed Sep 19, 2012 3:07 pm

I recently bought a second hand HVAC pump for repairing compsand boards. It's a Wigam DIP 402EV and it pulls a very decent vacuum, so much so that i have to have a valve and let air into the system to regulate the vacuum.

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The problem is that these pumps are not made for pulling air and they start burning oil. Does anyone have experience with using these pumps for vaccum bagging and tell me if they can they keep on working for the time it takes the resin to set?

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Re: Using HVAC pump for vacuum bagging (doubts)

Postby BWD » Wed Sep 19, 2012 3:36 pm

The pump is made to pull what I, in my layman's understanding, call medium to high vacuum.
For bagging kiteboards (especially onto light eps foam) we only want low vacuum.
So, the pump wants to pull against 27"+ vacuum.
We only need 10-20" to laminate without crushing foam.
To keep us and the pump happy, put a reservoir between the pump and the bag, and a regulator between the reservoir and the bag.
Also, a pressure switch between the pump and the reservoir.
The pump will make vacuum in the reservoir and cut off, saving itself from wearing out. As vacuum drops, it will kick back on.The regulator will keep an even pressure in the bag.
It's normal for the pumps to lose oil (should be as vapor, not smokke though!)
You can put a filter/condenser thing on the exhaust to recapture it, or just make sure you use it outdoors and replenish with vacuum oil from an appliance parts/hvac supply store.
But the pump should last a while even if you abuse it, in case you don't want to buy and hookup all those extra components. :cash:

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Al_Kiter
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Re: Using HVAC pump for vacuum bagging (doubts)

Postby Al_Kiter » Wed Sep 19, 2012 7:22 pm

thanks a lot for the info, BWD. I actually did make a contraption from a used kite pump to serve as a reservoir with a vacuum gauge and a valve to control the vacuum. It's the cheapest looking thing but i'm not into making boards (yet). This is just for the occasional sandwich repair:

Image

I did a bagging test run today on a board that needs a deck repair and kept the vacuum around 15'' with the help of the valve. That's when i saw the oil evaporating (you're right about that too) and became worried that the pump would not be able to handle this kind of work for a couple of hours.

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The oil level on the pump is full so tomorrow i'll do the bagging of the pvc sandwich with fiberglass and resin. Let's hope the whole thing stands up to it :D

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Re: Using HVAC pump for vacuum bagging (doubts)

Postby BWD » Wed Sep 19, 2012 7:26 pm

Looks pretty slick to me, hope you get some more good rides in on that board!

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Re: Using HVAC pump for vacuum bagging (doubts)

Postby Al_Kiter » Wed Sep 19, 2012 9:45 pm

Thanks. This board (Dominator 5'8'') is actually my favorite surfboard and i had a lot of fun this summer kitesurfing with it on light wind days. But it's really not made to withstand the punishment of kitesurf and the deck delaminated and buckled. I'm gonna fix it now, but i'll just use it for surfing from now on.

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Re: Using HVAC pump for vacuum bagging (doubts)

Postby Bigdog » Thu Sep 20, 2012 1:35 am

If you are doing a twintip...no eps ...then pump it full blast. It is only 14psi. I press at 80 psi with a pressure bag.. Just take time to figure out a leakproof system...not something you will get right for a while ;)

With eps keep it 5-10psi as others have suggested.You will need a pressure switch if as you say it burns oil. I have a similar pump and I just put a valve between it and the bag where there is a gauge. Then set the valve against the leaks to set the pressure I need. Play with with you stuff without resin until you know what you are doing and let it run for the cure time you need for your resin.....proof it ;) Don't get ina hurry. A lot of stuff will mess up when you have made your sandwich and time is running out. Any experienced builder has had their "oh shit" moments.

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Re: Using HVAC pump for vacuum bagging (doubts)

Postby Johnny Rotten » Thu Sep 20, 2012 1:44 am

I use a robinaire HVAC pump, I got it for free so beat the hell out of it...I run it to full 30 in hg and squeeze the shit out of whatever I'm working on, given what autoclaves an presses run at this is SFA for pressure. It sprays oil at first then when the pump body heats up enough it starts smoking. I let her go outside with an oil catch. I have built about 6 boards with it and done lot's of other composites projects....still running.

keep meaning to put a switch in but this seems complicated and expensive.

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Re: Using HVAC pump for vacuum bagging (doubts)

Postby plummet » Thu Sep 20, 2012 1:46 am

i bought one of these adjustable vacuum switches. works a treat. ps i use an lpg bottle as a resevour.

http://www.ebay.com/itm/Adjustable-Vacu ... ef&vxp=mtr

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Re: Using HVAC pump for vacuum bagging (doubts)

Postby gbleck » Thu Sep 20, 2012 3:05 pm

For twin tips I have run my cheep China knockoff pump for hours no prob. It vaporizes a tone of oil into the air and you don't really want to coat your glassing room in oil. You'll get bonding issues. I tried a milk jug with paper in it. That cut it down a bit. Now I just pipe the exaust outside. My basement no longer looks like an opium den when I use the pump. Love the pump. I have a plastic thermos as a more of a resin trap filled with carbon. Might filter out some of the epoxy fumes and the carbon doesn't hurt the oil just makes it a little black. I replace it often with compressor oil. The office switched from an oil compressor to oil free so I have a big supply free. :) I think it's just castor oil so it's not fatal just might make you a bit to regular if you breath it long term. Oh and to cool the pump I spray down the case with a water bottle. Evaporates off and cools down the pump. Don't know if it's necessary.

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Al_Kiter
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Re: Using HVAC pump for vacuum bagging (doubts)

Postby Al_Kiter » Fri Sep 21, 2012 7:30 pm

thanks a lot, guys, for all the good tips!

Today i went ahead and laminated the pvc with the resin. I followed your advice and placed the pump outside. Then I left it pumping around 7'' for 6 hours, just monitoring everything from time to time. Everything went perfectly and in the end the oil level had hardly changed.

Really stoked with the result:

Image

Now it's sanding time.

:thumb: :thumb: :thumb:


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