Stringer replacement question

[DualCore]

I am currently in the grinding phase of a stringer job on my 16 foot tri-hull and I'm having a little trouble finding the lumber to replace it with. This boat only has one stringer (right down the center above the keel) that is 1" wide by 7" high by 12' long and stops 12" short of the transom. The original was made out of 1 piece of dimensional lumber which I was able to remove mostly intact for a template. I was planning on replacing it with the same kind of wood (1 piece dimensional) but I am having a hard time finding good lumber in that size. So far the only thing I can find is either pine (which I don't think is very good to use, right?) or PT boards (which I'm unsure about, lots of differing opinions...). The closest I've found in fir is a 12' 2x8. So I'm wondering if it would be OK to replace a 1" wide stringer with a 2" wide one?

 

[92excel]

Re: Stringer replacement question

So I'm wondering if it would be OK to replace a 1
" wide stringer with a 2" wide one?

yes.. just extra weight..

you could always use ply.. the resin and glass work better with ply then dimensional lumber..

 

[PiratePast40]

Re: Stringer replacement question

I just got done making plywood laminated stringers and transom this weekend. To give yourself a little wiggle room, cut the plywood a little wider and longer than necessary. During the laminating process, things might slip a little and the overlaps can be squared up on the table saw. Cutting the angle for the bottom and for the transom butt joint is relatively easy but if you have the extra length and width, errors can be corrected easily.

For those people who don't make mistakes - disregard what I just said

 

[erikgreen]

Re: Stringer replacement question

Don't bother using dimensional lumber.

Replace it with a stringer made from 2 half inch pieces of plywood laminated together. It'll be stronger than the original stringer and probably about the same weight.

You can make it as long as needed by cutting stringer-width pieces from plywood and overlapping the joints... so join 4 and 8 foot pieces side by side like so:

484848
848484

and you get a nice, strong stringer. Use exterior grade ply and cover thoroughly with waterproofing, preferably poly resin and mat, or epoxy.

Erik

 

[DualCore]

Re: Stringer replacement question

Sounds like plywood is the way to go. Can I use PL Premium to laminate the pieces together or would something else work better? Is there an easy way to round off the corners of the plywood so the mat will take the wrap over the top better? I was thinking to use a router with a round over bit on the dimensional, but would a router work on ply...?

 

[PiratePast40]

Re: Stringer replacement question

I used resin and mat for mine and then screwed them together as a clamping mechanism. After the resin cured, I took out the screws and filled in the holes with resin. For just the stringers, I don't see why PL premium woulnd't work. If you haven't used it before, it has the consistency of taffy so you might just want to split the tube and use a putty knife to spread it around. Just keep in mind that it's the fiberglass and not the lumber that provided the strength.

I wouldn't worry too much about the edges. A block plane or "cheese grater" type of plane should do the trick. A grinder/sander would also work. But again, the edges aren't really a big deal.

 

[BobsGlasstream]

Re: Stringer replacement question

A router with a roundover bit will work fine on Plywood. Rounding off the corners will just allow the glass to conform easier. If you use stainless steel screws and countersink them like the last post suggest, I don't think you would even need to remove them.
good luck on the project.