I am in the process of putting the floor back into a 1992 Twin rig hull. I pulled 460 pounds of sand out of the bow of the boat. I was thinking of putting concrete below the front floor section, reducing the amount of sand bags above the floor, by the gas tank. Good idea, or not?
That sounds like a bad idea to me. The sand is soft and will conform to the shape of where ever you put it which distributes the load evenly. Concrete is hard and will create stress concentration points in my opinion, and it will probably not be removable. jim
Late night, wrong word. Instead of "put" I meant pour. The concrete would conform to the cavity under the floor. I would glass in a bulkhead to hold the concrete in place, in the forward section of the hull. I also thought of mixing the concrete in 60 to 90 pound batches, and separating them with plastic, so if you ever had to remove it, you could do it in pieces.
My answer is the same. I don't believe the concrete will adhere enough to be stable against the hull. If you are building a partition, I would use sand. Then there is no expansion problem. You could even put it in plastic bags. I believe on the twenty there is ventilation front to rear under the floor also, and drainage. jim
I would not do it. You might think the boat will never be used as anything but a twin, but if it is ever used as a single, it won't run. The motor will cavitate like crazy with permanent weight up front. Unless you are pulling monster acts, a twin rig should not need more than about 350lbs up front if you keep your tank full. That is 5 70 lb sand tubes. Even if you go to 490 lbs that is 7 sand tubes max. Just make sure you get the sand tubes as far forward as possible.
It is a means to an end, but a scary one at that. I agree about the fixed shape that the cement will take. I would also consider resale, even if you are not. Would you want to buy a boat with concrete poured into it? There was an old waterski magazine where they talk about making forms to pour concrete in. Then putting carpet around the forms. You could even install handles. You will still have the stress points mentioned by the other commenter. There are also considerations like trailering, it will definitely affect your tongue weight. I think sand and or water are both better and safer alternatives. If and hopefully it never will, but if your boat starts to sink, water is a neutral weight once it is in the water. With all of the great versions of water ballasts now, you may be able to find the custom fit you desire. When I first read your title, I thought you were thinking of using cementious, AKA Hardi Backer, for something. Chad
All of this is true. I would keep the sand. I know of plenty of Termite companies that use sand tubes to hold down the tenting that they do, you might look into something like that. They would be removable and would conform to what ever bend you want them to do. Daniel
You could also consider large metal weights. Old car cylinder heads, bolt on tire weights like the ones used for garden tractor snow blowers, the weights farmers hang on the front of their tractors, large free weights or dumb bells from "Play It Again Sports" and such may be easier to remove. I'd figure out a way to keep them from shifting around though! Sand bags are the favorite although they can break or open up making for a big mess and sand everywhere . . . . . . If you can mount the gas tank lower as that will help also as would a bigger gas tank. If you want less weight don't fill it up the bigger tank. This works for trailering also. Run the gas tank low when you are going to tow to reduce tongue weight. You can always siphon the gas out if you have to. To error on the light side is better than over doing it and trying to lighten up a heavy nose some how . . . . . . . .
