Recommended vacuum pressure for drying water out of board?

[Wind_Boarder]

Hi Guys,

For those who have experience with this. What is the recommended vacuum pressure (inches or mm Hg) that should be used to evacuate water out of a windsurf board? I want sufficient pressure to achieve a good drying rate without risking damage to the board.

Also what heating temperature range is good to use along with the vacuum?

Thanks!
Alak

[dllee]

LeeD here...
Depends on size of holes on each end, density of the foam core, location of the actual hole, and size of, warm days complete drying much more than fogland cold. Thin boards require less pressure.
Foam density can be 3/4 thru 1.25 per cubic foot, and it's hard to find out exactly what.
If the waterspots are nose or tail, might be better to spin or gravity on hot days, but control temps below 120, use black visquine to heat, remove and vent to cool.
Take your time on this one.

[keycocker]

Excellent advice. To be clear he means sunshine and black plastic or even a black cloth or towel .Before you vac arrange the board hole down for days in the sun. It will lose water in the day and suck in air at night to blow out with water the next day. Weigh the board first if you can so you know when it isn't working with vac or sun. You need not heat at the same time you vac.That- as the man noted- can go terribly wrong.[/url]

[thombiz]

I keep coming back to this thread because it makes me nervous. The OP didn't say what kind and construction his board was and that's important before you start adding lots of heat. More specifically, some boards are thermal formed in the Cobra plant. When you start putting them in black plastic and putting them in the sun, you can hit some very high temps. In intense summer sun, in the right place, you might hit internal temps of 185 degrees. This should be enough to warp the board into a very nice permanent Dali melted clock style lamp base. I've seen some thermal formed boards distort when injected with two part urethane foam used to replaced delamed EPS. This urethane foam is exothermic and may hit 155 degrees when kicking off. Just be cautious, check the construction, if you think it's thermal formed, don't put it in black plastic bags where you guess at the temperature inside.

Now.....vacuum pressure. When I'm building a board, I use no more than 11 psi vacuum when bonding resin, high density foam, and reinforcing on 1 lb. density expanded polystyrene foam. If I am using 1.5 lb. density EPS, I boost it up to 15 psi to get thinner, less resin, tighter layups. These numbers should work for you if you are using a vacuum pump to pull the water out of a waterlogged board. For the record, almost all boards are 1 lb. density EPS so 11 psi vacuum should be the max used.

Now to using vacuum to pull water out of a board, ala "Board Lady". I have the utmost esteem, respect and admiration for Eva Hollman. In my book, she is the tops, the best, and if she says it works, you have to believe it. I haven't tried it, but then I haven't been successful getting water out of a waterlogged board, either. My solution has always been to remove the waterlogged EPS and fill the void with 2 part, 2 lb density urethane closed cell foam.

[Wind_Boarder]

Hi Guys,

Thanks for the advice so far. I am vacuuming water (if any) out of a slightly impacted nose on a 109 liter 2005 JP Freestyle board (regular non-pro edition). The impact only affected one side of the nose and isn't very large. While there should not have been any temperature differential in the board at the time of impact there might still have been a slight vacuum in the board due to cooling from the temperature when I screwed in the vent screw at the beginning of the session. That could have been enough to pull in some water but I'm not sure.

I just finished building a vacuum system which is essentially the same as Eva's vacuum system. I started the board on the vacuum this evening at 4 inches Hg but maybe I should increase this pressure based on the suggestions in the postings.

I remember advice (probably from Eva's site?) saying never to put the leak side down when drying a board in the heat. The water in the board vaporizes and wants to escape upwards and will permeate through the board. The openings should face up and can be wicked with paper towel to help the drying process.

Thanks,
Alak.

[thombiz]

You can convert your inches HG to PSI here: http://www.engineeringtoolbox.com/pressure-units-converter-d_569.html

Looks like it comes out to 1.96 psi so you should be able to safely increase the vacuum pressure.

I went here for guidence in making a vacuum pump system, mine is about half way down the page: http://www.joewoodworker.com/veneering/visitorspress.htm

Here's a pic of the pump system I made: http://www.joewoodworker.com/veneering/visitorspress/thompson1.jpg

[sergem]

I tried -27 PSI through the vent on 2007 JP FSW 93 with no ill effects (sailed for more than a year after)

Same board, water though the vent again, just left the board in the sun in my car in office parking lot in Pleasanton, CA for a few weeks, even better results.

[sergem]

Also, looks like Eva's system pictured lacks dry ice/alcohol condenser, you might screw up your pump as the water WILL condense on its discharge port.

[dsgrntlxmply]

If you're trying to save a $1500 board with a $110 Harbor Freight air conditioning refrigerant service vacuum pump or some other clunker pump, I wouldn't be too worried about water vapor in the pump. Especially if the one of the other things that you use the pump for, is to degas resin without a cold trap.

The situation is different if you have a good two-stage lab pump and intend to use it again for lab work.

There also are vacuum pumps specifically designed for wet service.

[thombiz]

I've often thought that something like this medical aspirator pump would work to pull the water our of a board: http://cgi.ebay.com/Air-Shields-Dia-Pump-EF-Aspirator-Compressor-w-Jar-/150633156111?pt=LH_DefaultDomain_0&hash=item23126f8e0f