Another Princess 22 under construction

[wkisting]

Now that you mention it, Ray, yes, I think that is what I've heard also concerning marine Fir ply... that it is more prone to rot because of voids, NOT because Fir is necessarily more rot prone than Okoume (I think you're right that in terms of the wood itself, Fir is more resistant than Okoume).

Is it really likely for a P22 kept on a trailer to rot if all surfaces are sheathed in fiberglass? I realize it will sometimes get rained on if kept in a yard, but even then, wouldn't the fiberglass offer plenty of protection? (Assuming, of course, the hatches are kept tight so water isn't allowed to pool into any shaded/enclosed compartments... where it would then almost certainly cause problems in the long run).

On a separate but related note (since I've mentioned fiberglass sheathing), maybe Graham or Charlie can weigh in on this question: When I built my Pocket Cruiser using the ply on frame method, I waited to glass until the boat structure was essentially in place. I see that Graham's plans for the P22 call for glassing the edges of the hull sides together before stitching it together, but would it cause any problems if I went ahead and glassed (sheathed) both sides of the hull panels completely in glass before stitch-and-gluing the structure together? It was a real pain trying to glass my Pocket Cruiser after the construction (especially interior surfaces). With the P22, I'm toying with the idea that maybe I would glass all surfaces prior to construction, use tape at the seams during assembly, and then apply a second exterior layer to the hull after assembly. I would end up with a hull with 2 layers external, and one layer of glass internal, plus reinforcing glass at the seams.

I realize this would increase weight a bit (due to the second layer on the exterior), but not too much, I don't think.... maybe 70 - 100 lbs. at most, if my estimates from the Pocket Cruiser are correct. The advantage is that I wouldn't need to lay glass on the interior later (just glue and tape the seams). Or would it weaken the boat structurally to not have a long, unbroken sheathe of fiberglass throughout the interior? Just tossing around ideas... let me know what you think.

[Charlie Jones]

I see no need to glass the interior of the boat. Three good coats of epoxy will seal the wood quite well. Glassing would just add weight. The interior of the Princess is not exposed to weather. It's all epoxy coated, then primed and painted.

If you did choose to glass the interior of the panels I don't think there would be any problem in taping later, provided you gave the filets and tape a well ground surface - you can't glass well to cured unsanded epoxy any more than you can to cured unsanded polyester. You run the risk of having contamination along the parts where the tape would go otherwise. I do frequently precoat panels and sand them out on the bench because it's much simpler to do the bulk of the sanding while every thing is lying flat. I pay particular attention to where the glass will go. I'll put on two or more coats (depending ) prior to putting the panel in place. Of course on canoes, etc, sometimes that changes the bending characteristics of the panel, so you have to be careful with that aspect.

I built a 35 foot tri in the early 80s, it was epoxy coated inside, then painted. As far as I know the boat has NEVER had the first problem with rot, save one place on the transom that got damaged and went un repaired for too long, allowing water to sit inside the ply edges. THAT required surgery to replace bad wood, but that wasn't the fault of the epoxy coating.

In articles I've read in Professional Boatbuilder, the Gougeons have investigated boats built back when they FIRST began the method- they found NO problems with rot, except in those instance where the boats were damaged and neglected.

By the way- one disadvantage of fir plywood on the exterior is that if left unglassed it tends to check from exposure to the sun and elements. Then it'll deteriorate from water intrusion through the checking. A layer of glass will stop that. I've not had the trouble on the INSIDE of boats though, but I hear a few people have. Again, I think 3 good coats of epoxy on the INTERIOR will do fine.

I should also point out here that I did not paint the BILGES of the boat. Only the rest of the interior. The bilges are left bright so you can see any possible water intrusion by seeing color changes.

[wkisting]

Thanks guys... that was a quick reply.

I'm a little surprised by your response. I was under the impression (obviously mistaken) that it's standard practice to glass the interior too. I wasn't envisioning a heavy glass... maybe just 3.2 oz. silk weave or something like that (which wets out as quickly as tracing paper and vanishes twice as clear)... but I thought it was necessary with Okoume. Glad to hear it isn't required, as it will save a lot of time and money if I don't need to do it.

On a kayak, at least, I've always heard that from a structural standpoint, glassing the interior is more important than the exterior (of course, you still have to glass the exterior, too, to seal it from water). A lot of those in the know about kayak building say that fiberglass performs best in compression (I think I have that right, or maybe I'm reversing my structural vocabulary here), which is why glassing the interior is a real boost to hull strength. Of course, maybe that doesn't apply to a S&G boat like the P22, which probably draws the majority of its structural strength from the bulkheads and compartment framing, correct?

With my Pocket Cruiser, I left the interior unglassed and haven't had any problems, but if I build the P22, I'll be trying to build it so that someday she'll end up as a museum exhibit somewhere on the Mars biosphere... as well preserved as a bug trapped in amber. kidding, of course... but wouldn't it be nice?

Is it possible to get a nice brightside finish on ply that has been glassed? I've never tried it, but I see that the first P22 ever built (on the B&B website) has a brightsided cabin exterior... Is it not glassed? Or is it glassed and varnished?

[Charlie Jones]

canoes and kayaks are a quite different animal from boats like the Princess and the Core Sounds. Those boats do have a lot of framing, etc for support, plus are built from quite a bit heavier plywood than the average canoe or yak. Those are built from the lightest material possible thus they sorta require that extra strength by the interior glassing. Although some of the canoes are only glassed on the interior in the areas where the paddlers would be.

And yes, it's very much possible to fiberglass then varnish. Canoe and Kayak builders do it all the time. Some of their boats are ALL bright, hulls included and all glassed. They go to ridiculous extremes sometimes too- wet sanding (with 600 grit) the glass/epoxy before varnishing it. Do your learning with the glass work on areas that you DON'T plan to have bright. But bear this in mind- Sunlight damages varnish- does it anywhere but more so as you move south. If you choose a bright finish, you're going to have a real job keeping it looking good. It means sanding and revarnishing BEFORE it starts to look bad. Otherwise you get to take it down to the epoxy undercoat and do the varnishing again. Plan on 6 - 9 coats of varnish, with a renewal coat at least every 6 months. Down here we touch up ( sand and add a coat) about every 3 months during the summers on our brightwork.

Of course if the boat is always stored indoors you get much longer life from the brightwork, and on the inside, it will last for years.

These two yaks were at the last Duckworks Messabout we attended- they are glassed

[wkisting]

Thanks for the info about brightwork guys.

I have done brightwork before on a kayak... I wasn't sure, though, if it works the same way when using ply... (cedar wets out really nicely, but I noticed when building my ply Pocket Cruiser that the layers tended to look a bit milky in a lot of places instead of glass-clear like the 'yak... maybe it was the glass I was using... didn't matter anyway since I painted the Pocket Cruiser).

Anyway, sounds like the same process I used to finish my cedar strip 'yak (all bright). That's encouraging.