New Stringers Big Question

Hello,
this is my first boat that i've had to restore and i have to floor up and the stringers out, they are very short (the tallest area is about 4 inches) my question is as of right now the stringers i took out were 1 " x 4" and would i be able to replace them with normal treated 2 "x 4" for additional strength and than glass them over? any advice would be much appreciated.

 

What you have to do, in my opinion, is to deduct the maximum load that could support the old profiles and replace them, the way you want, but considering that the new be able to withstand at least the same charges. If you put a "core" of any material, and clothe it with glass, is very likely that the glass has to bear, alone, the bending and shear loads. Therefore, consider the thickness that you give the coating and how to weld it to hull.

 

did the old stringers fail, or did they just rot out? No reason to go bigger, they were likely strong enough, they just had water trapped between the wood and glass and caused it to rot. A larger stringer will not help that. You might use preservative treated wood to replace the same size stringers, that should make it last longer. And you should make some efforts to make water intrusion less likely.

Making the hull heavier and stiffer generally makes it stronger. but you have to consider making it stiffer in one place (where you replaced the stringer) could put stress elsewhere in the hull that it was not designed for, so the failure would just move to another location. It just depends on the design of the hull.

The most likely effect is you would add weight without making much of a change in durability.

 

Might help if everyone knew your LOA, Beam and type of boat for better sound advice
Otherwise, in my opinion, the above replies should suffiice

 

I'd not use the PT lumber. Most PT treated lumber is of fairly poor quality and flat sawn, so it lacks dimensional stability and has defects. The USA is now using CA treatments for retail PT stocks, which can cause bond issues with the usual choices in our industry. Lastly, bonding a big hunk of solid lumber is bound to cause delamination at the bond line in time. Thick pieces, like a 2x4 will have sufficient internal mass, that dimensional changes as a result of environmental differences (moisture, temperature, etc.), will pop off hard plastics pretty quickly. Simply put, the best way to get a 2x4 from solid stock on a boat, is to bond two pieces of 1x4 together.

My recommendation is to not bother making it heftier, but do make the laminate better, which is likely what failed in the first place. Concentrate on the bonds and tabbing and just replace the wood as it was, with a clean, defect free, preferably quarter sawn, piece of 1x4. Douglas fir in your neck of the woods should be readily available.

 

Sounds Good

very good i appreciate the help guys. sounds like i will just stick with the same wood. yeah and also when i opened the floor it looked like someone had replaced them before me, and did a poor job at that. it looks like they did one layer of cloth, and one solid peice, so it cracked down the middle and allowed water in.

 

and Petros, yes they did. the fiberglass split down the center and the middle of 6 stringers roted.

 

What do i use?

Oh and also if i decide to laminate the two 1x4's what do i use to laminate them?

 

do all your repairs, coating and bonding with epoxy resin.

Steve

 

Epoxy would be my recommendation as well, for the novice. A single layer of fabric over a stringer isn't going to hold diddly, so "tab" it well and you'll not have to do this again. I'd suggest a 12 ounce biax for the tabbing, with generous overlaps and hull shell contact over at least 6" on each side of the stringer.

 

All good advice.

The most common mistake people make is to build it bigger and stronger than the original design. A hundred small increases ends up with a too heavy boat.

Odd they split down the center. Post a photo.