question about fabricating long(20'+) stringers

Hi all, I posted some questions earlier about my project boat. It is a 28' Master Marine center console. I have recored and closed in th transom and am moving on to the rest of the boat finally. Right now I am working on the stringers. I have removed 16' so far and will be cutting out the bow fishboxes to see how much furthur I need to go to hit dry wood.

My question concerns the actual building of the new stringers. This is my plan as of now, unless someone gives me a better idea. The orginal stringers are 3/4" or 5/8" plywood encased in woven roven and tabbed to the hull. My plan is to use 3/8 or 1/2 plywood laminated together with the joints stagered every 4 feet, then bed the stringers to the hull using cabosil thickend resin. After that I plan to cover the entire stringer and extend the material at least 6" on each side of hull using 1808 biaxial and vinylester resin. Sound good? Or would I be better off using 3/4 plywood scarfed and glassed in?

If I go the 1/2" laminated route, do I need th scarf the joints? If so, how long of a scarf and what is the best way to scarf them?

Thanks for the help,
Patrick

 

Have you considered simply adding (epoxy and screws) cheek blocks to one side of the stringers where the joints fall? You can bevel the edges of the plywood blocks to allow the glass to flow around. A single 3/4" plywood stringer would then make the most sense.

 

The stringers in the one I majored and others I assisted were poorly laid to begin with, cut up, core exposed. I debated lifting the entire liner off and, in retrospect, it would have been the thing to do but the owner kept saying, "minimum necessary", "go ahead and do this one more thing, then start to wrap it up..." It definately would have been cleaner, easier to repair, and maybe even cheaper to remove the liner, repair it where it was too thin or damaged, get rid of every bit of wet foam, and better reattach the halves. I could have made the boat better than new and wouldn't have to repair so much of my own cutting. You are STILL going backwards! Others will answer about the stringers. I would just make new beefy ones and know that they weren't the weak link.

 

Mark, I understand what you are saying about the liner, but I have no way to lift the entire cap off of the boat. The other problem I could see with pulling the cap, is that the gunnels are filled with foam. So I really do not feel that I am going backwards. I have planned this out and am following my plan. The forward fishbox needed to be removed anyways. I am raising the deck 1.5", so the box needs to also be raised. While it is out I will have access to the remaining sections of stringers.

Alan, so just using a single piece of 3/4" with the blocks on one side of the joints would be fine? If so, that would save ALOT of time and trouble and materials.

 

Either that or a layer of 3/8" on each side, well bonded with epoxy and screwed. Do you have any photos? How was the original joint done?

 

Alan, it will be this weekend before I get back to the boat to get pics. I didnt pay close attention to the joints when I cut the old ones out. It kinda looked like the just butted the pieces together and glassed over them with a piece of 6" or 8" woven roven. I will check it out further once I get back to the boat. I will have fuel tanks inside the stringers and I dont think I will have room for the 3/8 on the inside.

Thanks for the help and ideas