Bulkhead repair needed?

Hi all.

I've removed the two motor mount stringers on my 1997 Larson Cabrio 310 as they were soaking wet and cracking. The forward bulkhead next to the gas tank in the pics below (not the best pics, will work on getting better ones) is both wet where the stringers attached to it and the bond between the two board has come apart (top view). However, it's still very solid and very rigid.

It would seem the correct repair is to remove this bulkhead and put a new one made up of two laminated pieces of plywood. What's not clear to me is how it is attached at the outermost edges to the other stringers…does it simply abutt them and is tabbed to the sides of the stringers?…or does it run beyond what can be seen and the stringers actually end at the bulkhead? If it ends at the stringers, it would seem easy to cut it out.

Also, if this bulk head were to be removed, how would I glass the new one to the hull on the tank side since there is no room between the bulkhead and tank?…I assume it would not get glassed on that side but simply epoxied to the hull and glassed on the outside/bilge side?

Thanks for any info.

--Rick

 

Stringers are usually a solid run from the transom to the bow, but not always. As well, usually the framing sits astride them but not always. It's hard to know without intimate knowledge of your make and model. You may need to take the tank out in order to get to the back side to properly tab it in. I know what a pain all this can be, as I'm in a "stem to stern" refit myself, with stringers, engine mounts, transom, decking, bulkheads and cabin rebuild. It all started with a leaking gas tank, caused by soaked plywood framing laying against the tank.

 

Thanks Skua. Removing the tank, while certainly being the best way to tab that bulkhead in, is not feasible. It would involve destroying a good portion of the cabin in order to put it back in and frankly my patience for this boat is beginning to run extremely low.

Without removing the tank, if two pieces of plywood are laminated and glassed over to create the new bulkhead, then inserted into place into a thick bed of epoxy and then tabbed on the outside...that will likely have to do. Not ideal I know...and I'm open to other ideas...

 

Laying the frame into a bed of epoxy may lead to a hard spot, and stress cracking of the hull along the epoxy bed. Some say to lay stringers into a bog of epoxy or elastic, others say to leave a gap. I laid my engine stringers into a bog, due to their short run. Everything else I have done a gap, and successive layers of tabbing. Unfortunately when these problems are discovered, it's the onion effect, many layers peeled back to get to the center. Almost certainly the cause of the problem is water ingress from the transom. Unless you stop the water, you new repairs are likely to wet out and turn to mush as well. Usual suspects are swim platform brackets, leaking transom plates, trim tab mounting bolts, and transducer mountings. Don't overlook leaking thruhulls.

 

From what I read I thought I could embed both the stringers and the bulkhead with cabsoil mixed to the consistentcy of peanut butter. For the stringers, they will be then glassed over. For the bulkhead, the only bond to the hull on the tank side would be the cabsoil...on the bilge side it would be tabbed with glass to the hull and stringers. Please let me know if I'm overlooking something. And most if not all the water in my bilge is simple rain water that makes its way in usually from the engine hatch. My cockpit sole is removable and has a channel to catch water...but the hatch in the sole does not.

 

Rain water is the worst. It will rot the wood fastest. Salt water pickles the wood to a degree and slows down the destruction. Yep some recommend bedding the stringers others say to float them, so its hard to recommend a procedure. I looked at how i thought the stresses would build, and adapted from there. Anywhere where I thought a lot of flex and banging would occur, I floated on the tabbing. Where ever I could I built off of the original tabbing and framing. I will say I have seen many boats with cracks where the frames and bulkheads print through the hull. Can't think of any stringers, although I have seen photos purporting to be a Carver with stringer print and cracking, in the hull skin.