1981 Seaswirl 16' stringer repair

[iflyboats]

I recently picked up this POS for $200, not realizing how much work it would be to get it up and going. Motor mount beds and stringers are all totally rotted out - to this point I've pulled out all the rot, built new stringers & mounts and have started tabbing it in. The boat has two foam-filled stringers on either side that are still solid, and made out of nearly 1/2" thick fiberglass. I've tabbed in the new stringers with 4 layers of glass, alternating CSM and 6oz cloth I was able to find locally. I've referenced "The Elements of Boat Strength," and according to my scantling number I only supposedly need 2.5-3mm of cloth for tabbing, which the 4 layers of CSM and cloth make up. I'm new to all of this though and am wondering if that's really enough - it seems most people use 1708 for tabbing, but all the posts I've seen on this topic tend to be for much bigger boats. Can I get away with just the CSM and 6oz cloth, or do I need to order up some 1708? The original stringers were tabbed in with purely CSM, a layer maybe 1/16" thick up to 1/8" in some areas.

 

[mickyryan]

welcome , as far as your tabbing goes i would tab it with 3 layers of 6 oz cloth going 2" 4" 6" in each direction that should make it plenty strong, and as far as original yep i have seen stringers only held in with 1 layer of csm and lasted thirty yrs but remember that was all done at same time as hull was made so they had a chemical bond where as your bond is mechanical.

 

[mickyryan]

i gotta ask what are you bedding the stringers with , that white stuff? also isn't that where your tank goes? and why the extra stringers?

 

[iflyboats]

i gotta ask what are you bedding the stringers with , that white stuff? also isn't that where your tank goes? and why the extra stringers?

Would the 3 layers of 6oz cloth have CSM between each layer? Or just one on top of the next?

As far as the “extra” stringers, that’s how the boat was originally built. I want to say they are just to support the floor and that the all-glass stringers are the real stringers, but I didn’t design the thing. SeaSwirl is a small builder in Oregon, not a whole lot of these hulls around.

The stringers are bedded with mainly peanut butter but I had some rather large gaps under some areas - i was trying to use peanut butter for all of it but it was taking a ton of resin. I used Loctite expanding spray foam to fill the majority of the gaps and then filleted over that with peanut butter (the polyester resin doesn’t melt the Loctite foam). The bulkheads are bedded in pure PB, and about 3-6” under the stringers at each end with the rest filled with foam.

The stringers and bulkheads I made templates for, sized up in the boat and then screwed & glued together outside the boat before dropping the whole thing back in. They’re way overbuilt, I put a couple oak dowels sideways through each stringer where I screwed into the end grain for better bite - trying to make this thing bulletproof.

 

[iflyboats]

And the fuel tank is up at the front of the boat on top of the deck, behind a (removed) kick plate under the dash. You can barely see the edge of it in that picture, just ahead of the most forward cut in the deck - it's angled sideways right now (needed access to make a cut to get out one of the walls of the ski locker).

 

[mickyryan]

i would not trust that bedding , bedding is usually a solid material making a even bed under the stringer , some place a piece of foam so the stringer stays off floor while they are bedding it in but i wouldn't trust what you did .

 

[iflyboats]

i would not trust that bedding , bedding is usually a solid material making a even bed under the stringer , some place a piece of foam so the stringer stays off floor while they are bedding it in but i wouldn't trust what you did .

The originals were glassed in without any bedding at all so I was thinking this would at least be better than that. The bulkheads were sitting on top of the flotation foam they used to fill the cavities and allowed to weep underneath.