67 SN Resto/Mod rev. 2

Good luck on finishing the job and bringing her back to her former glory!

Looking forward to the progress and pictures!!

Gel coating isn't as hard as some think my advice would be use a gravity fed gun with a BIG nozzle size, something like 2.5mm, mix only 750g at a time and get it out the gun as quick as possible!
If working outside watch out for overspray (I got the neighbours car) and use wax, sanding between coats as bugs are a nightmare if going down the route of wet-on-wet.

That's the original interior. The back seat bottom cushion would have been vinyl covered foam (no base or frame). I assume it would have been 1-piece and not 3, but someone else can confirm. Not sure if the jump seat would have fit between the buckets, I've only seen it used behind the drivers seat like a modern jump seat... Pauly banana posted a picture of his 68 with the jump seat in use. Get some more pictures and dimensions off it- that would be a cool thing to reproduce! That single cushion with the straps is a throwable pfd and isn't part of the interior, ha.

One of the exhaust manifolds on my 273 has pin holes where yours are burned through, I'd like to hear about options to fix it. The good news is that there does not appear to be a water jacket too close to the runners.

Those are pretty significant holes. Pin holes like Tim is talking about could be brazed, or carefully welded with a high nickel rod, but holes like that…. I doubt they are worth the effort.   I would think you would need to cut and chamfer to a reasonable shape, find a similar thickness cast material, machine it to fit, and then weld it in without it cracking.   If I had a mill, some durabar, a preheat oven, a good set of high temp blankets, and a lot of patience… and those were the last manifolds left in the world it would probably take me about a case of beer to get one good one out of the two..

I would do what the factory did with those floor supports. Putting in ribs is a lot of time, and done wrong they can create stress concentrations that could possible crack your new gel cote. In that boat I wouldn’t consider them.   IF you really want to do them for some reason… we can talk about how to do them to limit the possibility of them causing more harm than good.

Awesome project- glad someone could take advantage of the work Mike already put in there!

You think they glassed those supports to the side of the hull from the factory? I'm not planning on foaming that area, do you think it will need a brace under it or just bed it & glass it to the hull sides.

Riley wrote: I wouldn't glass them to the sides. If you use decent wood like Douglass fir for your strapping and come within about 1/4 to 1/2 inch from the hull sides, and use good quality 5/8" plywood and come within 1/4 to 1/8 inch from the sides, it will be plenty strong enough.

Whether ply or glass over foam, the floors are usually glassed to the sides right? If so, what would be the reasoning for not glassing the straps to the sides as well if whatever is over it is already bonded to the side?

Im no naval architect, but I have broken a lot of boats that were designed by naval architects and I did sleep at a holiday inn last night (wasnt staying there I nodded off at the bar.. but I digress) so Ill take a swing..

The floor wouldn’t be glassed into the sides with that setup necessarily.   In this case without the foam I would recommend against it. Quasi removable vinyl wrapped plywood sections screwed down is what I would be expecting and recommending.   Whenever someone firmly attaches something dense (ie wood bulkhead or support bedded and glassed to the side and/or floor) to a relatively flexible hull that has some significant height perpendicular to where it attaches it yields a large radius of gyration of the now attached column. Meaning the for a given stress (load) the strain (deformation) is so much higher for the hull that you can basically envision the support as rigid.


When you are glass over foam the floor itself can create a pretty good stress concentration at the top of the foam, a nice fillet and a tapered joint can help blend from that locally very rigid section to the relatively flexible hull. I like to think of the boat rubbing down a dock board, (rock, trailer roller, what have you) the rubbing could be along the length of the boat like when you come in a little hot or vertically from the motion of waves or weight shifts. You don’t want to be rubbing down and flexing the side (or bottom) then reach a rigid point as that is when the flex turns to cracks and tears.   On a smaller level the same thing happens each time a wave hits… these boats are generally overbuilt so the hull doesn’t flex much and there is a very thick hull to deal with it but I am a little sensitive about it I guess due to the time I have spent on/working on racing canoes and sailboats (both of which I have had break in half on me during races). However even in these tanks it is not at all uncommon to see a set of gel cracks in line with where the floor meets the hull on a glass over foam boat.    In fact we see a lot of them where the floor then separates, water gets in, freezes, and causes havoc. Which occurs first, who knows, it is like the chicken and the egg.   

The other side of the coin is that you have to support the hull to a certain extent to limit the amount that it flexes both for longevity and performance. It is a balancing act. However on a boat like this one here, the factory didn’t need support here and history has shown that the boat will tolerate it pretty well, so there simply isn’t much to be gained by trying to rework the original methodology in this case. Glassing the strap itself rigidly to the hull is the worst case scenario, you basically end up trying to push the hull out in concentrated rectangular shaped zones.   If you don’t like the strap floating out there I like the idea of glassing a thin glass covered foam ledge to the hull that the supports can rest on but are not glassed/glued too..   or you can do whatever you want and avoid, docks, rocks, trailers, and rough waters and youll still be fine.

+1 with Joe. Also keep in mind these early glass boats were all built the same. My 69 Mustang has the same stringer structure as my old 64 American Skier, the only difference was the newer one had foam with a layer of 'glass over it rather than the older one's painted plywood floor and no foam. I think some sort of floor,composit or plywood attached only to the structure and then covered would be the way to go

But you are comparing an + 80's hull to a early 60's designed hull a lot happened in 20 years. 80's floor was structural 60's floor was something to keep your feet dry. Stringers did not start to rot until floors were foamed and glassed over. I have 1/4 ply under my fiberglass pan and no foam so far so good. The way I cut the glass over the foam to remove it left about a 1" flange around the stringers and sides,there is no more than roughly 6" of span not supporting the floor.

I redid the floor in my 65 using bulkheads in similar fashion to Joes, using bulkheads but my floors are individual pieces wrapped with carpet. Main reason is I didnt want to fiberglass in the exhaust

Foam was an option up until 68ish when it was required. I am surprised your hull is that thin, Mustangs and Skiers seem thick

Like HW said and Joe implied, there was likely not a *lot* of engineering analysis performed on the structures of these boats when they were designed in the early 60's (or possibly earlier). They simply leveraged the existing wood hull structures that they had built previously, made some changes that improved their manufacturability (prebuilt stringer systems, etc) and sent them out the door. That said, we now have 50 years of real world use to see what worked well about the original design, and what didnt. As Gary said, foam was optional in most boats until the late 60's- so there are examples of both foamed and foamless 60's hulls around that have been examined- the 1st gen SN and Mustang included. So, just because this particular boat was built with glass over foam construction doesnt mean it couldnt be rebuilt foamless, in the same style as other foamless 60's SN's... because we know those held up well. The earlier hulls do tend to be a bit thicker and smaller, and thus, dont require the same number of structural members to replace the strength of the hull/foam/floor sandwich found in later boats (like Joe's 2001).

Joe shared his points mentioned above with me when I was planning my BFN build, and it helped shape some of my design and layup schedules. For instance, while the boat was rebuilt with 3x the number of ribs and bulkheads as original, 2/3 of them are not bedded to the hull and have reduced layup schedules compared to the others. This should slightly improve the flexibility of the hull and reduce stress concentrations. Still, the boat is largely overbuilt- and I am ok with that. It is worth noting that the v-hull BFN has a very different structure to a small flat bottom boat.

I do have some Skier/Mustang/1GSN stringer rebuilds in my future, and my current line of thinking is to install a few strategically placed ribs perpendicular to the stringers to provide floor support. They will likely be glassed in with a very light schedule. I do not care for the straps that CC used, as they are a PITA to work with- they require a lot of extra cuts in the stringers and create a lot of corners that are tedious to glass around... but since the structure on this boat already has the notches cut, youre stuck with the downsides of that system already. So, you might as well take advantage of their upside- they will not cause any stress concentrations if theyre not tied to the hull or walls.

As far as tying the floor to the walls goes, I'd probably opt for a few thin layers of glass , just to keep water from draining down a crevice. But, no need to make that a structural joint, as you wont notice the increased strength. Chris's Promo was surprisingly solid and it had no structural floor to speak of.

TRBenj wrote: So, just because this particular boat was built with glass over foam construction doesnt mean it couldnt be rebuilt foamless, in the same style as other foamless 60's SN's... because we know those held up well.

This and Gary's comment about it being an option addresses my main concern that there was a reason CC foamed/glassed this SN hull and thus I needed to put it back that way. Now I'm convinced so I'll put that to bed.

Thanks for all the insight guys.

I've seen that on a few pictures posted over the years as well as fiberglass tape attaching the strapping to the hull. I believe these were on early glass boats that were not foamed. I'm not so sure foam was an option up until '68. It definitely was on the early 60's boats, but other than the Skier like Chris Mars has, has anyone ever seen a late '60s boat without foam? I haven't. I know someone with a Classic that says their original strapping has blocks at the ends that just about touch the floor, but are not adhered to the floor or the sides of the hull.

No matter what you do, I would not butt the plywood floor to the hull. Leave a small space.

wwchevy wrote: I'm confused about the floor- should it be a fiberglass pan connected to the hull along the sides to keep water out of the hull and capret wrapped plywood sitting on top of it? That was how my Mustang was when I bought it.

If you went with that route it would have to have either foam or possibly a layer of ply just to support the glass "pan". Correct?

I am leaning towards Joe's idea of a semi-removable floor which would be screwed down. There would still be a 1/8"-1/4" gap all around the perimeter of the floor (not glassed to hull). Water would still be able to get in there, but if the hull/stringers were shaped to drain accordingly, and everything is soaked in CPES, then what would the problem be?

I'm not saying this boat will be a trailer queen, but it certainly isn't going to be sitting out in rough conditions for any extended period of time. If you ever thought it was soaked under there, you could still pull the floor up and take a look.

But just when I start thinking along those lines, I read this from a while back:

TRBenj wrote: I agree with Pete, he's the expert. In regards to a removable floor, while it would be nice to access the entire structure to inspect for damage or water intrusion, I think such a concept has too many problems to become viable. The incorporation of the floor into the structure of the boat (essentially tying the stringers together to the hull walls in all directions) really adds to the structural rigidity of the boat. That requires a good bond down to the stringers and several layers of glass to the walls. You also dont want any water intrusion points, so the structural joints also serve to seal the structure off.