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Vacuum pump sucks water out of board!! Thank you Boardlady!
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thombiz



Joined: 25 Jun 2007
Posts: 618
Location: Corpus Christi

PostPosted: Sun Oct 27, 2013 1:39 pm    Post subject: Reply with quote

I'm taking the gurgling sound as a sign of "bubbling water". Once that sound stops, I will definitely set the tail (vent end of the board) higher. As for the temperature limitation of 110 degrees, most boards are constructed using heat to set the resins, especially those from the Cobra plant. These boards can definitely deform when they experience temperatures above 110 degrees. (Makes me wonder about those boards left in a hot car all day.) My board was made the old fashion way...resins and hardeners and Corecell. It can withstand much much higher temperatures.

I hadn't seen that series of posts by the Boardlady, but they seem to be spot on with what I'm seeing. Thanks KMF and also, again, Eva Hollmann.


Last edited by thombiz on Sun Oct 27, 2013 11:08 pm; edited 1 time in total
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kmf



Joined: 02 Apr 2001
Posts: 336

PostPosted: Sun Oct 27, 2013 2:57 pm    Post subject: Reply with quote

I poked a hole in a polyester board once, and to speed the patch job a bit I set it out in the sun to dry. Four hours later I had a delamed mess on the side of the board facing the sun......just saying.....

KMF
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thombiz



Joined: 25 Jun 2007
Posts: 618
Location: Corpus Christi

PostPosted: Sun Oct 27, 2013 3:36 pm    Post subject: Reply with quote

KMF, the point is well taken. I will keep it in mind to avoid a delam. Bob T.
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AndreiA



Joined: 14 Apr 2013
Posts: 38

PostPosted: Sun Oct 27, 2013 11:06 pm    Post subject: What would happen if you bake the board at 110C Reply with quote

I wonder if anyone tried to put a 'wet' board into an industrial oven with set temperature a little above the boiling point like 110C.
In theory, water should evaporate and get out Wink
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Brian_S



Joined: 11 Jun 2005
Posts: 149
Location: SE Michigan

PostPosted: Mon Oct 28, 2013 9:12 am    Post subject: Reply with quote

thombiz wrote:
I pulled a vacuum of 15 psi, and the pump shut off and didn't cycle back on. It is built to cycle back on when the pressure drops to 12 psi, but with a perfectly sealed board, that didn't happen. I'm of the opinion than it might be necessary to ad a tiny hole at the opposite end of the board from the vacuum pump hose connection to let a small amount of air into the board, to carry away the water molecule staturated air. If the hole is too big, you can't create a low enough atmospheric pressure inside the board to pull the water molecules out of the styrofoam.


Bob,
Atmospheric pressure is rarely above 14.6 psia, so it's impossible to pull a vacuum of 15 psi. I suspect your gauge is off quite a bit, because even at a vacuum of 14 psi (absolute pressure less than 1 psia) you'd have a compressive force on the board equal to over 2000 lbs/ft2.
Overall, I think your strategy is good. Years ago, I did exactly the same thing: vacuum, board in the sun and small breather hole on the end of the board. I also used a collection jar to keep water from entering the pump. I contacted Eva before applying the vacuum to get a recommendation. I wish I could remember, but I think she told me only to pull about 4 psi vacuum.
Brian
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thombiz



Joined: 25 Jun 2007
Posts: 618
Location: Corpus Christi

PostPosted: Mon Oct 28, 2013 11:47 am    Post subject: Reply with quote

Good catch on the atmospheric pressure thing! I don't know where my head was! I just looked at the guage and noted the reading not giving a single thought to the point you can't exceed 14.6 psi. And you're right about the pounds per square foot being around 2000 lbs. For sure, the guage has to be off bigtime. Embarassed
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thombiz



Joined: 25 Jun 2007
Posts: 618
Location: Corpus Christi

PostPosted: Mon Oct 28, 2013 6:43 pm    Post subject: Reply with quote

I looked very closely at my vacuum pressure gauge today. The numbers aren't PSI at all, they're inches of Hg or Mercury (written in little tiny print). The 15 inches of Hg is equivalent to about 7.36 psi. This is one of those things, you look at it for years and you forget what the units mean, you just say to yourself.....set it to 15 cause that's what I usually use!

Thanks Brian for the heads-up. I'm hoping this post will be a good resource for some time to come and it can only do that if it is credible and your catch helps give it the necessary correction.
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Brian_S



Joined: 11 Jun 2005
Posts: 149
Location: SE Michigan

PostPosted: Tue Oct 29, 2013 8:29 am    Post subject: Reply with quote

You're welcome Bob. It's a great post - what this forum should be about.
Brian
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