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PostPosted: Wed Aug 08, 2012 7:41 pm 
Site Rank - Captain

Joined: Wed Feb 09, 2011 6:41 pm
Posts: 71
Location: Cape Coral FL
I am doing a pylon repair as specified in the spring 2010 hotline. My question is how important is it to vent the hulls with the vent tube? When glueing the pylons into the corning castings won't i most likely clog up or seal off the vent tubes when i stick the pylon into the epoxy?

I understand that a non-vented hull will expand and contract and lead to de-laminatioin, but what if i always remove the plugs when the boat is out of the water?

Before the repair, when i would remove the drain plugs one hull always let out a "whoosh" and the other would not. So i assumed one of the vent tubes worked, and one did not.

But both hulls are ok, and I always remove the drain plug.

PostPosted: Thu Aug 09, 2012 6:49 am 
Site Rank - Old Salt

Joined: Mon May 09, 2005 10:25 am
Posts: 3306
Location: Jersey Shore
As long as you always remove the drain plugs when not sailing, you should be fine.

If the hulls are well sealed, you may still occasionally get a woosh of air from the hull when pulling the plugs, even if the vent tubes are working. Consider for example, you're sailing on a hot summer day but on a body of water that's relatively cool. While sailing, the air in the hull is cooled by the surrounding water to say 70 degrees. When you remove the boat from the water, the outside air (say at 90 degrees) is going to cause the air in the hull to expand quickly and build up some pressure before it can fully vent through the small, 1/8" vent hole. So the air is likely venting, but this doesn't happen instantaneously when there's a large temperature swing.

This baffled me for a while because I would come in off the water (on a hot day) and pull the drain plug and I'd get that woosh of air, but I'd also get some water draining out and wonder how the heck the boat could leak water but be air tight.


PostPosted: Thu Aug 09, 2012 3:03 pm 
Site Rank - Deck Hand

Joined: Thu Aug 09, 2012 2:34 pm
Posts: 3
One of my sailing buddies just delaminated about 6 feet of the forward outside of a hull. We don't know the cause but I'd be cautious about creating unnecessary stresses. I'd include the vent and use care when gluing.

I used to sail where the water was really cold, Colorado. Putting a hot boat into cold water would create a significant vacuum when the air in the hull went from 110 degrees to 70 in minutes. That is a 40 degree drop which results in a force of about 1.1 psi. Let's round off to 1 psi and think about the impact of 1 psi on a square foot of hull (144 sq inches), therefore 144 pounds of force on each square foot of hull. Over 6 square feet of hull you have 864 pounds of force.

PostPosted: Fri Aug 10, 2012 12:58 pm 
Site Rank - Old Salt

Joined: Fri Jul 15, 2005 10:43 am
Posts: 779
Location: St. Louis, MO
The vents are there for a reason. It is best to keep them open and functioning. You can get condensation inside the hull when the air is cooled so water will come out even if the hull is air tight. The whoosh means you are not venting at all.


Current Boat
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Previous boats owned
'74 Pearson 30
'84 H16
'82 H18 Magnum
St. Louis, MO

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