F36 stringer repair

[Footeloose]

Hi everybody. I could use some of your knowledge & expertise, please. The subject is a 1972 Trojan F36, love these boats, & that's likely why i have the boat i do. I am in the middle of a stringer repair, of which some parts to me are a bit mysterious. The stringer i'm working on, is the inside on the Port side. The stringer was just mush at the transom, & very wet all the way forward. I chose to leave the sides of the fiberglass intact, thinking it might be better to fit the new one into the channel that remains, & the location would be as original. I did trim the fiberglass on the top, getting rid of the radius, & grinding the insides of the channel flush. But, i'm all the way forward to just behind the rear motor mount, & the lower wood of the stringer is wet, but not exactly rotted. I guess one of my questions is if I should keep removing old wood until i get to dry, solid, wood to lap the new stringer onto. Taking anymore out at this point will mean at least lifting the weight off the engine to continue. This brings me to another mystery, which is, that i have noticed the port engine is in the boat, leaning down on the inside, about an inch. I measured the height from the inside of the hull to the top of the stringer on both the starboard engine & the port, & there's about 3/4" difference, the port being lower. Also noticed there is a sawn block bolted to the top of the stringer with 3 lag bolts, under the motor mount plate, & the one on the port is somewhat shorter than the block on stbd, Some time ago, I disconnected the port shaft coupling, in the water, & the alignment seemed about perfect, no problem reconnecting the coupling. Has anyone ever seen anything like this on a F36 before? Could it be this way originally??? Also, as i was dismantling the lower part of the stringer, a big chunk came out, maybe a foot long, which had what appears to be a piece that was sawn out on a band saw, a nice rounded curve on it that must have been part of the joinery on the original stringer, & there is a 16 penny nail thru it from the bottom obviously up into the top part of the stringer. I have to believe these oddities aren't just on my boat, but do, especially wonder about the setting of the engines, & how far i'll have to go to get to good wood? Sorry this got so long, but am more than curious at what i've found here. Again, any help is appreciated, Thanks for reading, Dave

[prowlersfish]

There has been some good threads on stringer repair here. The round piece that came out sounds odd, photo? As far as the engines sitting a bit different I would not worry if in alignment I have seen it before.

[Footeloose]

Hi Prowlerfish, thanks for the reply, your advice on the engine mount is about what i was thinking, so good on that. the issue on the other piece i mentioned, was about 2 1/2" square, with a 90 degree radius made on it. if you've seen some of the joinery where they make a joint `with 2 of these curves that nest together to make a joint. i assume it may be for added glue surface at assy. Sorta like a ying & yang, if you are familiar with that form. Im letting everything dry out some more, but about ready to start fabricating the new beam. Its been quite a job, especially for a 79 year old guy, but im happy with progress so far. Again, thanks.

[Big D]

Ideally you want to get rid of all the moist wood. If you don't, you will not get a good bond between it and the new wood, and it'll be a weak joint which will likely delaminate. That will eventually lead to movement and other issues. Once encapsulated, you'll also be trapping that moisture in there for ever which will continue to deteriorate the assembly at an accelerated rate.

If I'm reading it right, you cut off the top of the stringer's fiberglass layer and left the side layers intact? I assume you then dug out whatever wood you could in the cavity. If that's the case, ideally it would have been better to cut out the entire inboard side of the stringer, leaving the opposite/outboard side and top glass layers intact. This gives you full access to the inside of the stringer, and allows you to prep/grind the inside of the layers left which is a must for proper adhesion. I don't know how you'll be able to accomplish that properly with the two side layers still in place. Cutting as I've mentioned also maintains the original height and shape of the top of the stringer. The only time I would cut the top away is if circumstances dictate that the entire stringer including all glass sides be removed, or I want to change the height and top shape of the stringer. Having said that, given that you have spacers under the mounts, you may want to consider doing that now so that you don't need the spacers.

You mentioned that you got rid of the radiuses which I suspect you mean the transitional corners from the horizontal top to the vertical sides. If so, you want a bit of a radius as glass mat doesn't do well on a sharp 90 outer or inner corner. It will lift off the corner and leave a void. The thicker the mat, the bigger the radius needs to be. So on an outside corner, you round it off and on an inside corner you fill it with putty and shape it so it's concave and is an gradual bend for the glass rather than a sharp one.

The piece I you found was likely a section with an S joint to connect two sections together. Trojan used that type of joint often. It's easy for production but more importantly, it provides for a larger bonding surface and that type of cut leaves no sharp corner cuts which is usually where the wood starts to split under stress.

Good luck with your project and keep us in the loop.

[Footeloose]

Hi there Big D. Just noticed your reply to my stringer issue. Thanks for the info. I like your idea of cutting away the one side, why didn't i think of that?Another thought i had in the night, was, why couldnt i just lay roving in strips into the 2 sided channel I have now, wet out with resin, & just build the new stringer out of fiberglass? You were right on, when you mentioned the "S" cut joint, that was what i meant. Thanks for the tip on the radius on top for forming the new cloth, I planned on that. Right now, I think i will proceed with my original plan, using the wooden fillers i have made to fit, but lay them in as you suggested. The old saying still applies, 2 heads are much better than one!! Gooday, Dave

[Big D]

The problem with trying to slide the core into a channel is that you have to apply a glass layer on both sides of the inner walls for proper adhesion. That's next to impossible to do and keep those layers in place while you slide the core in as this has to be done while it's still wet. You also can't clean/grind all areas of the cavity properly as access is limited that way, very important step. Make sure you lay the core in a base of putty/thickened resin along it's entire length. Good luck.

[Footeloose]

Hi all, well, it's been a while, but the stringer repair was a success.
all in & buttoned up. I did cut the center side of the old stringer fiberglas off about an inch from the botom, the fabricated the new stringer pieces in place. The layup went very well,& also reinstalled the fiberglas side back in place. The 20 oz. laid right into place with tabbing to the bottom, & over the forward joint near the engine mount area. With the Onan removed, i laid treated 2x4s across the stringers, & short studs vertical up & under the aft deck support stringers. Tying all that together is a half inch strip of plywood, 7" wide. I then used half inch plywood over the horizontal 2x4's for a large lazeratte storage, big enough to sleep in. I feel the repair is totally sound, & given that I'm 79 1/2 years old, it will likely outlast me. Thanks to yall for the support & advice, Dave Foote The only "real" Footloose!!!!