1971 Larson Rebuild

[Sonoma]

I am starting on a new project, a 1971 Larson Tri Hull. After some work she will be my rat fishing boat, nothing fancy, but sound and seaworthy. Its intended use will be bass fishing up in the creeks full of snags and stumps, where I wouldn?t want to take my bigger boat. It will also double as a swimming platform for the kids and grandkids. I will be adding casting platforms fore and aft and plenty of storage.

I knew the boat needed work when I bought it, the price was $200 for everything. At least the trailer is in good shape but I will have to replace the stringers and transom in the hull before I do anything else. In addtion the foam on the starboard side is soaked and the port side is damp so I am planning on tearing it out as well.

I have been reading the forum for a while and have picked up a number of good tips. I do have a couple of questions that someone may be able to answer.

The stringers in my boat appear to be approximately 1? thick and set on top of foam. They start at the edge of the center tunnel and are about 8? wide. I don?t see how they would stiffen the hull much. I assume that is the function that stringers provide in a fiberglass hull?

What material is best for stringers? I saw mention of pressure treated wood in one post, is that the standard in restorations?

I also read where someone suggested abandoning the stringers and pouring expanding foam into the void below the deck after it had been replaced. I haven?t been able to find much more about that. Has anyone tried it?

Here are some pictures:

 

[tallcanadian]

Re: 1971 Larson Rebuild

good looking boat there sonoma. different manufacturers used different kind of wood for stringers. mine used 4 2x4 and 1 2x6 for the main beam in the center. others use plywood. i used kiln dried 2x4 and 2x6 spruce wood. the only problem with treated woods is that the fiberglass doesn't adhere very well or not at all. the wood i used for my transom and floor was marine grade 5/8 plywood X 2 lyers for the transom and marine grade 3/4 plywood for the floor. i think you will find that your stringers are actually fiberglassed to the floor of your boat, or at least they should be. remove any wet foam and replace it. the foam will never dry. as far as foam in place of stringers, i don't have the answer. but i would want it to be as strong as ever. more for safety than anything. hope this helps. keep us informed on your build. i love tri hulls.