Thread: Basic sturctural question

This depends on the design and type of boat you are building,.

In older designs where you have plank on frame this is an issue as they were designed before EPOXY Resins were discovered. That means that they relied on the glue (if used), paint(if used) and bilge ventilation, to stop rot.

Newer designs like my Mangrovejack 3.65, and all of Mark Bowdidge's Designs, the bilge and or under floor areas are either Glassed or given a saturation coat of Epoxy Resin .
Most Plywood and Strip plank construction use Glass cloth and EPOXY Resin to encapsulate the ply/timber, and create a composite hull material, this then means that any water/moisture is effectively, prevented from being absorbed .

Older hulls can be retro treated after stripping and cleaning (depending on the design), Clinker is a bit more of a challenge, but it can be sealed and glassed, Carvel plank is similar, with an older boat , with clinker hulls you must watch for hogging if left on a trailer for long periods(keel starts to deform from weight of the boat) Clinker hulls were originally designed to stay in the water and for the water to cause the individual planks to swell and seal ( this is also true of CARVEL to a lesser degree)hence the caulking , between the planks.

I believe that I have this right, if not then P.A.R , will correct me I'm sure.

Jeff

[QUOTE=ozsmithy;1401246] With hull drainage being important for the long life of a hull why would the bottom of the frames in a timber boat touch the ply? would it be better to put more fairing strips on the bottom and have the frames miss the ply so water can run back easier? [QUOTE]

First off, why might you do that? A nice large area to glue/nail to, I'd guess, and may also aid in the stiffness of the hull? Depends on the design I think, but I get the feeling it's a somewhat old-fashioned way to do it.

Second part, about options, it really depends on the design, but all decent designs will have some provision for the exodus of bilge water, assuming the boat isn't small enough to just tip over to empty it - and even then usually. Either a pump, bungs or so on.

If you've got a design in mind that isn't reliant upon bilge pumping, there'll probably be a detail that allows a small hole to be drilled in said frames to let water travel - They're called limber holes, and are usually at the lowest-point in the frames, near the centrelines. Once the ply (or timber) is fixed to the frame, it's unlikely the small hole will cause a structural issue, and it fixes that issue of sitting water you noticed.

That said, there are a range of designs that do what you say, using fore-and-aft "Stringers" to glue the ply to, which means the frame hovers off the ply somewhat and water can move around more freely. Just depends what you prefer, and what the design calls for.

I'm still on a big learning curve so thanks for the eludication
also have you found any epoxies that better UV resistance over feature timbers?

Opps, just saw the tread on this four lines down

Some epoxies have better UV resistance, but all will need to be over coated with something, like varnish or polyurethane to fully protect them.