If you vacumn bag a board with water in it, what is the longest you would go if the board had a moderate amount of water(say 1-3 lbs)?What sort of vacumn pressure?
I will answer my own question. Eps boards absorb water and faster than PU boards. There is approximately 10% of volume air between the cells. This amounts to about 6 lbs for each cubic foot of foam. A cubic foot of foam is about 32 liters. Six pounds of water is about 3 quarts.A short board is around 30-40 liters of volume hence it can theoretically absorb double its weight in water. An SUP of around 150 liters can absorb 15 litres of water or about 30 lbs. These numbers rarely happen in the real world but 20% of this number will still give you 6 lbs. All that water in the core is very mobile. Just take a piece of eps and blow on it and you will feel your breath come out the other side. Being mobile will allow it to heat up and expand. And since water vaper is denser than air, the force is greater. Remember all those ships powered by steam boilers? Now to answer my question. I had a 9’8" fun gun 3" thick by 22" wide that got gashed by a rock on the bottom with water seeping out. I don’t know how long it was used in this condition, but water seeped out for more than i day before I vacumn bagged it. This was with a sweatshirt to absorb the water, 25" mercury for 4 hours. I weighed the board before and after and took out 2 lbs or water. The board is now not weeping any water and now I can repair. Hope this can help someone out there. PS I used to vacumn bag 40 foot sailboats to dry out absorbed water. Just imagine what the logistics of that big board are like!