V-Berth Question

[richfriend]

I have finished removing the rotted wood from the forward 2/3rds of my Kells 28 project. There was an assortment of non-marine, exterior grade plywood that had survived fairly well for 30 years but was rapidly being consumed by deferred maintenance. The v-berth platform was supported by the vertical panels at the aft end (they were missing the bottom several inches) and was tabbed to the sides of the hull forward to the chain locker for the whole length of each side. The space beneath was occupied by a poly water tank (loose) and only acessible through a cutout hatch in the aft starboard side of the v-berth, leaving a substantial amoount of dead space.

I plan on installing a short bulkhead forward of the water tank creating some useable storage. Should I tab the new v-berth platform directly to the hull as the original, or would I be better served to attach longitudinal stringers to the hull and fasten the platform to them?

I know that the fabrication of the stringers will be challenging due to the compund curves/angles but it seems like a better method of building. In addition I like the concept that I can take parts apart with a screwdriver rather than a skill saw, sawzall, and dremel tool.

[bcooke]

I know that the fabrication of the stringers will be challenging due to the compund curves/angles

I wish I had known that before I put in my V-berth! :-) I think the tabbing is strong enough but the problem I see is in positioning the panels while you are tabbing them in. The panels will want to move around and if you have to crawl onto them to tab them up forward then I can imagine some complications. The stringers provide a stable base for the panels while you secure them. They also help stiffen the hull which is probably not a bad thing.

While unscrewing the panels seem like the easiest way of removing them, cutting through the tabbing is pretty quick too. I keep an old chisel and hammer in my toolbag just for this sort of thing. A grinder/cutting wheel combination or a skilsaw can make quick work of tabbing and the chisel will get the corners and other tight areas.

In my case, I glued in stringers, screwed down the panels and then tabbed the panels to the hull. They don't call me Captain Overkill for nothing! The tabbing has the added benefit of not allowing any water to accumulate in the crevices between the edge of the panels and the hull which was a factor in my decision.

And just for reference (your situation will vary), had I bowed the stringers up about half to three quarters of an inch in the middle I would have had a perfectly flat V-berth. I can see the discrepency if I look for it closely but I don't feel it while sleeping or anything.

-Britton

[Tim]

If you foresee a need to remove your v-berth panels for regular access to anything beneath, then screwing them down is the only way to go.

A better way, though, is to plan your access during construction so that full removal wouldn't be necessary. While the idea of an easily removable interior is tempting, it brings its own compromises. Screwed-down panels like this tend to shift and move, squeak and groan, and might be less than satisfactory in this way. It's easy enough to build in some decent-sized access panels or hatches that will give you all the access you need, until 30 years from now when someone wants to reconfigure once more.

From a structural standpoint, you don't need the strength afforded by tabbing. But tabbing in your platform does make for a nice, stable, sturdy platform that won't make noise when you sleep on it, and also avoids the dirt-collecting crevices as Britton mentioned.

If you can tab the platform without any sort of support against the hull (such as to support you leaning over to do the tabbing), then you don't strictly need the stringers. In most cases, though, this will be a challenge, so some sort of support at the hull edge will probably be required. It may not need to be a full-length, continuous stringer, though the additional support doesn't hurt. Remember that if you tab only the top side of the plywood, your weight over time will tend to try to pull the plywood off the tabbing during normal use; tabbing beneath as well can eliminate this problem, but may be difficult to do.

I'd go with partial to full lightweight stringers (you can make them out of foam and glass them to the hull) for platform support with tabbing on the top surface of your platform for the final connection.

[richfriend]

Thanks for the replies. I hadn't considered the use of foam for support stringers, but that seems the way to go. Easy to work and shape and readily available since I have a billet of blue dock float foam up in the rafters of my workshed that has been gathering dust.

regards

richard

[Tim]

A couple notes about the blue foam:

First, acetone will dissolve it, but epoxy resin will not. So you can use it as long as you take care with the solvents.

Second, of course, the foam has no structural properties and serves only to be a formwork for the fiberglass that you will lay over the top. In this capacity, though, for insignificant interior supports like this, blue foam will work well, and is cheap and easy to work.

Structural applications and purebred jobs require one of the excellent structural foams out there--Corecell, Airex, etc.

Good luck!