Having a leaking vent plug is for sure not a good thing, but it may not be
as disastrous and detrimental to your board as you are currently thinking.
I’ll try to answer your questions one at a time and give you some solutions
To dry up the interior of your board and once dry, keep it sealed.
I have a Kombat 106lt model of 2006. A few days ago as I was getting ready to get into the water, I noticed water coming out of the air vent which was closed. After unscrewing the valve, I noticed the O ring was in a bad shape. I put the board in the sun and I let the water boil and evaporate through the valve.
Good thinking! The only thing you could have done to improve this would be to make a “wick” from some absorbent paper toweling. Roll the paper towel into a kinda cone shape
And stick the pointed end down into the vent hole all the way to the bottom if possible.
If the towel sucks out a lot of water, replace it.
The heat inside your board on a warm day will indeed cause the water to vaporize and the moist air will be pushed out of the interior foam of your board.
Then, I replaced the O ring with another O shaped black rubber fitting on the screw (probably not an O ring) and after 1 hour on the water, much more water was evaporating through my open air vent afterwards.
Hard to say if the vent plug was still leaking or not, but if you put something other than the correct size O-ring in the vent plug chances are it did not seal.
Part of the problem with the O-ring is sailors want to tighten them up way too much.
Just put in a new O-ring and snug it down until it slightly compresses the O-ring and tight
enough so the plug won’t back out.
Overtightening the O-ring just crushes and deforms it, and ruins it’s sealing properties.
Is the damage on the board from the water that came in, repairable?
You should be able to get most of the water back out so you can use your board this summer, and then when you store it for the winter, look for a very low humidity storage
place so it can dry out over a longer period of time. Keep it inside your home where it’s warm and dry if possible. If not, store it near something warm that circulates the air.
Does this look like a valve problem or the board might have a hole somewhere else? If we are talking about a valve problem, is it important to use exclusively O ring rubber seal? How often should I replace the O ring?
First you need to get as much water as possible out of your board.
Then you can test around the fin box and mast box to check for leaks.
How can I test if, after replacing the O ring with another O ring the vent is watertight?
You can use the “change in temperature” from morning to the highest temperature time during the day.
With a new O-ring (apply some soap to the threads of the plug and wet your fingers and put some soap on the o-ring before installation) properly seated, in the morning, as the day warms up, you can slightly loosen the vent plug.
If the O-ring is sealing correctly, you will get a little hiss of pressurized air that builds up inside your board.
Do not leave the vent plug tight for a while during the heat of the day until you are sure you have as much water as possible out of the core of your board.
As soon as you come off the water, turn your board over to let the water drain out around the plug the turn it right side up in the sun with the vent plug out so that any water inside will be vaporized.
How can I test if there is a hole somewhere else on the board? (Other than the vent problem, the board is intact and in a very good shape, no scratches, hits etc.)
The only likely places for there to be other leaks are the fin box and the mast box as these are the only places that extend from the outside and into the core of your board.
To test them, make a solution of soapy water and put your board in the direct sun for half an hour with the vent plug closed. The board will develop internal pressure and you can dribble some of the soap mixture on the mast box and fin box to see if any bubble develop.
If you get bubbles, that’s where the leak is.
You can also use the soapy water to check to see if your vent plug is leaking.
How can I extract all water or moisture from the interior of the board? Is there some sort of test to see if there is still water left inside? ( I haven't weighted the board before this incident, so I cannot compare weights)
As I said, unless you are a professional with a vacuum pump; vacuum regulator; and you know how to use both, using thermal expansion is the best method available to you to get the water out of your board.
Place your board in the direct sun, with the vent plug out and a wick stuck down the hole.
Change the wick frequently!
When you aren’t getting any more water at the bottom of the hole, you’ve gotten about all the water out that you are going to. Do this with the deck of the board facing up into the sun. If you turn it over, since warm moist air rises, you would be spreading the water vapor
inside your board toward the bottom. So remember vent plug out, deck up, in the direct sun.
You may have to do this several times to get all the water out.
If you are not sure if the vent plug is sealing correctly, I’d suggest putting a piece of duct tape over the plugged vent fitting when you are taking the board on the water. The tape will add another barrier to water intrusion.
Thank you for reading this. Apologies for the long list of questions. I am very frustrated, since this board is my first -and expensive- buy of a new board and I was very happy with it until now.
If you live in the Western Part of the USA, you could ship your board to Eva Holiman during the winter for a complete vacuum drying out.
Check out http://www.boardlady.com
/water.htm for more information on drying out your board.