waterlogged hull

S

sunfishtoronto

New Member
I just bought a sunfish. It has the new style rudder. My biggest concern is that the hull is waterlogged. Two of us had a hard time carrying it to the lake. O.K. I'm an old fart however my son in law is young and strong.

So far the general consensus seems to be to open up the inspection port and let it dry out.
In Ontario it still is pretty cold and are there other suggestions that may help.

My wife says I should light a fire inside it to dry it out. Hmmm is there a message hidden here?

Any help would be appreciated.

Larry
 
Well first thing I'd do is get out the bathroom scale and set the edge of the fish on it to see just how water logged it is.
"standard" hull only weight is 130 pounds. Anything over that is as the fat lady says "just water weight".
Our record weight (after opening the deck drain and propping up the fish so any "loose water" would drain out over night) was IIRC 185 pounds the next day. It took again IIRC about 4 months with two inspection ports and a shop vacuum cleaner hooked up to blow into one port several hours a day to bring it down to 140 pounds.
 
The hull will dry out in the cold as well even if the water is ice. Ever see an old timer hang up wet laundry when its snowing out? The same happens with food that's not sealed well in the freezer. Once you dry the hull make sure you find and fix any leaks or you'll be right back to waterlogged.
 
We tried putting a small fan mounted to an inspection port, and running that off a solor pannel when it was at the club, and a small power supply when it was home. I think it worked some, but what I've heard a lot of people do is suspend a light bulb inside the boat and just leave it. I have also tried this and it works really well, and fairly fast.
 
Think of the physics. Closed cell foam won’t let in liquid H2O. Water crossed through the foam’s cell membrane as H2O vapor. The attraction that made it cross over was dryer air in the cells, aka lower vapor pressure. Once inside the cell it condensed back into a liquid state. Now you have to get the liquid back into the vapor state and coax it back across the cell membrane by energizing it then reversing the pressure differential.

Changing the air inside the boat helps if the incoming air is lower humidity than the vapor in the foam cells. Heating the air expands it giving it greater moisture carrying capacity, in other words lower relative humidity. That air needs to be vented as it starts to saturate with vapor coming out of the cells or it will reach a point of equalization and the transfer process will stop.

The quickest drying will happen when three conditions are met. The water in the cells is converted to a vapor, the vapor pressure outside the cell is lower than inside, and the vapor pressure outside the cell is not allowed to equalize with the vapor pressure inside the cell.

As the cells give up moisture the vapor pressure in the cells lowers and the process slows requiring more and more energy to vaporize the remaining moisture and keep the vapor pressure up. At the same time the outside vapor pressure needs to be lower and lower to maintain enough differential for the transfer process to keep working.

Applying what I have read here, the solar heated black wrap with forced air circulation method should produce the best results.

In a humid climate low volume circulation would be more effective than high volume because the solar input would then be allowed to act as a dehumidifier for the ambient air drawn into the hull.
 
Megan,

I think I'm in love with you! This explaination is so detailled and scientific even I can understand the cause, effect and cure.

Thank you so much for your message and I hope that one day I can reciprocate.


Larry
 
Larry,

I have had good luck with drying out a boat with two 6" inspection ports,
one installed just aft if the "V"of the splashrail centered between the "V" and the forward edge of the daggerboard trunk and the other on the rear deck, centered about one inch forward of the transom and right under the tiller. Turn the boat upside down outside on saw horses, cover with black plastic to absorb sunlight/heat and then install a 6 inch duct fan (available at Home Depot for about $17.) Let it run 24/7 and it should dry out in several weeks if the abient air conditions are warm and dry. In the winter, same drill but also put a 40 watt lightbulb inside the hull. When done, do a leak test by blowing air into the hull with a small pump and covering the hull with a film of soapy water looking for the bubbles. Fix leaks with thickened exoxy resin or your "goop of choice.

Good luck.

Alan Glos
 
Larry,

Shhhh… don’t tell my husband :eek:

You are welcome, but I can’t take all the credit. The description was adapted from my daughter’s 7th grade science project on osmotic transfer through a semi-permeable membrane. She recognized the condition as we read your post and dictated the reply while reviewing her project write-up.

Alan Glos, Sounds like you are right on the money with your approach. I’m surprised you got results so quickly considering the cell to cell movement deep inside the foam must be crossing through thousands of cell walls and each successive cell must have a lower vapor pressure than the last. I was thinking Gail Turluck’s estimate of a year or longer was what could be reasonably expected.
 
Actually my big success with this two port and fan/lightbulb rig was over an entire Upstate NY winter (November - May) and the curious thing was that the 40 watt lightbulb never had to be changed for the entire 7 month period, reinforcing the idea that what kills regular lightbulbs is turning them on and off a lot. That said, the dry-out time in a very warm/dry enviromnent (read: Arizona in July) should be a lot quicker.

Alan Glos
Cazenovia, NY
 
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