stringer repair

Why use such a heavy foam for the core of sole/deck? If you use it for stingers/frames you still need glass for stiffness. 26lb PU foam (with or without chopped glass inside) cannot replace the stiffness of wood in ALL applications.

High density inserts - yes
transom - yes
stringer/frames/sole - you can make those parts much lighter with a 5lb PVC foam core, save a lot of weight

 

Mike S,
I'm reinforcing my transom (adding bracing that is foam core with glass and epoxy over that) because I've removed twin inboards and I'm mounting a 4 engine outboard bracket on the back. I've already increased the transom thickness to 3" with 6 plys of okume plywood/glass mat. Now I'm adding some bracing to tie the stringers to the transom, just for good measure.

 

I am new to all this. Can you use treated lumber for stringers and decking? I live in north Texas and it is hard to get marine plywood.

 

I just use ply from Lowes as I can't afford Marine ply for as much as I need. As long as you glass it correctly- with no openings for water to get it- it'll last forever.

 

pt wood needs time to dry, it's always sopping wet when i see it in the store

 

Yep, I find the same thing - soggy wood in the store. I'd say the best thing to do is to buy some plywood, let it dry out really good. You can test it for dryness by cutting some into small even size pieces, sticking one into the microwave, cook it for a while - if it gets hot and steamy, it still is full of water. You can weigh it if you have a small scale, or make a balance beam out of a ruler and a pencil - put the pencil down on a table, lay the ruler on top of the pencil - centered on the pencil to make a see-saw, balance the see-saw, put the blocks of wood (one side has the baked piece, the other the unbaked), now add some drops of water to the baked one to see how much water was in it. You'll probably be amazed how much water wood can hold.

Wood will never dry to near 0% moisture content in normal conditions, unless you're in the desert. You should have the wood at somewhere in the 7% moisture range (my swag) to use in a boat.

Once you have it dry enough, test some for adhesion to your resin by coating one side of the wood, then after it cures, try to peel it off. If the resin comes loose without having wood imbedded in it, you do not have a good bond, and your boat will delaminate and probably send you crashing to davey jones locker. Or something like that.

 

for you guys using plain ply,,,,,paint it with resin first,,,,after its all cut and fitted,,,take it out and paint on a couple (slow kicking) resin,,,even tho theres big disagreements,,,,i think resined wood is better then marine grade crap.,,and all this talk bout foam,,wood,,,core,,,stringers,,,is simple to show everyone why its done,,,,get 2 pieces of resined glass,,,,nice flat ones,,,a couple square foot,,,lay 1 on top of other,,then put 2 or 3 small blocks of wood maybe 2"x3",,,stick them between the sheets,,,,,now JUMP on em,,,,,,what a cracking smashing sound huh,,,,,now,, take same set-up , minus the blocks,, instead fill with foam,,wood,,,sand,,,whatever,,,now jump on it,,,no breakage huh?

 

the1much,
Yep, if you're gonna jump on em, the wood is definitely the stronger of the two, and be heavier. If you don't have a concern about weight, then use wood.

If you're not going to jump on em or put force on the side of the piece, but you're going to put force on the edge of the piece, then foam may be just as strong, and lighter. If you have a triangular brace between the transom and the stringers in the bottom of the hull, then the forces acting on the brace are going to be compressive or tensile forces acting on the edge of the brace.

 

what im trying to say , is that ANYTHING is alright to use,,,,all it is, is a filler...is like punching your sheetrock walls in ya house,,,,,hit between the studs,,,smacko,,,ya hand goes through the sheetrock easy as hell,,,,,now in between those studs fill with foam,,sand,,,water,,,,,now hit it,,,,your hand dont go through,,,why?,,is it because the water is strong??,,is it because the sheetrock got stronger?? maybe both,,neither,,i aint no smarty,,,all i know is it works out that way,,,,now take a piece of fiberglass 1/2 inch thick,,jump on it,,its breaks kinda easy,,,,now take 2 pieces of glass 1/8 inch's thick,,spread em apart and fill with whatever,,jump again,,,they seem to be like steel compared to the 1/2"

 

P.S.
thats not to say wood core isnt stronger then foam core,,,,i would imagine wood is stronger,,,,,,and would opt to use wood in deck and transom,,,,that being said,,,,some boats are made with foam just for the flotation value,,,,like some of those make believe boats,,,i mean bass boats,,,,and things like bayliners hehehehe,,,,,some boats are full from hull to deck with the stuff. for stringers,,i always opt for foam,,,,,the insides dont really matter,,the important part is the glass strength, and the bond between boat and stringer. is like making a "bead" in aluminum,,the alum. piece with the bead is "stronger" then one without the "bead"
k.k.,,have i rambled enough for ya to figure out i know absolutely nothing about boats?,,in fact i hate the damned things