This was as a response to the idea that one should chuck a handful of salt into interior areas of a boat to prevent rot.
Not a good idea.
The problem is that salt sucks moisture. So it will remain almost perpetually moist.
Then on a warm day the moisture will evaporate. At night the air cools and the moisture will condense over all the internal surfaces of the tank. So you end up with pure distilled water droplets gradually removing salt from the upper areas of the tank and rinsing the salt down to the bottom.
So in the end you end up with a permanent supply of fresh water for the upper reaches of the tank – so you may end up with rot around the deck structure.
Seal the Timberwork
Don’t leave the timber raw – coat it preferably with epoxy – an excellent moisture barrier. Not coating the interior of the boat prevents you from doing an effective job of mopping out the interior – the raw wood will absorb any water that goes in the tank and then you can’t get rid of it through either a bunghole or by mopping out. So you end up with lots of water vapour in the hull when it gets warm again.
Rot: the Ultimate Solution
The only thing that prevents rot is preventing one (or both) of moisture or air.
Epoxy is one way of doing both. I have seen so many boats built in the last 25 years using epoxy that are in excellent condition compared to my own boats of similar age which were only sealed with varnish or everdure over the same time frame. In the end the epoxy is worth the expense.
It is easy to apply while building the boat.
However with a boat that is already finished it is sometimes not worth it in terms of LABOUR – ie you cannot do a good enough job once the decks are on and there is often heaps of paint to be removed.
The relevant question to ask someone who is about to undertake this process is … “How much do you love the boat”
The Value of Ventilation
Another way from tradition is to provide good ventilation for the interior of the hull. Larger boats need to have it designed in – read some of Francis Herreshoff so hear someone banging that drum!
Or for smaller boats…
Inspection ports at opposite ends of the tanks left open when the boat is not in use – of course with the boat under cover to stop rain going in
If not in use and if you dont have a garage – store the boat upside down on the trailer or some bricks to keep it off the ground with all the inspection ports off. A tarp over the top, but clear of the ground so air can blow under. If the boat is too big to turn over or has ballast that makes it difficult then build a wooden structure over the deck to hold the tarp off so air can circulate up the sides and along the length of the boat. If the boat has a drain hole the plug should be removed and the boat propped up so any water WILL drain. Check that the hole isn’t blocked from time to time.
That’s very best way to long term store a boat if you don’t can’t swing it up under a carport or put it in a shed.