Flatform hull construction WB 173

[Bob P]

Been awaiting comments about this technique, guess not enough subscribers have received their issue. Looks like an interesting technique for stitch and gluers.
Old Bob

[Tom Lathrop]

This fellow has had this method out for several years. I don't find anything wrong with it provided the bottom chamber is well protected and sealed.

On the other hand, I don't see any real reason to build a boat this way either. I think it stems from the presumed difficulty of building anything other than a flat bottomed boat. Another claim is that it makes building chine flats easier. Don't think that is true either.

[Bob P]

This was not an addition to an old boat, it was an entirely new approach.

Bob

[Paul Scheuer]

Looks to me like a good way to kill several birds. He's got the V hull, flat cockpit deck and light weight, and doesn't sacrifice much in the way of accomodations. It probably could have been lighter.

A similar honey comb structure was to be my entry into the single-sheet paper boat contest last year.

[TomRobb]

It looked like a rather round-about system to me. And all those unventilated chambers looked like a good place for rot to start. :rolleyes:

[Eric Sea Frog]

I had suggested this for the Weekender a few years ago, to no avail. Changing a hull that way won't solve all its problems, though.
It would hide the keelson, but it could house a jack-the-knife device and some lead ballast.
But you'd still have but two chines.

[Bill Perkins]

I've read that some early V bottom craft on the Chesapeake had a related construction .Wide thick timbers were set athwartship from chine to chine creating a flat floor .The dead rise was then hewn out of the solid timber below.I've thought of substituting high quality closed cell plastic foam blocks, fiber glassed top and bottom after shaping ,and with wood frames and topsides then bonded to it .

The bottom glass would run up onto at least the garboard to help tie things together .Chine flats could be worked in if wanted ,and there'd be no rot issues .Plus the shape of the bottom wouldn't be limited to what can be developed in sheet ply .You could have a sharper forefoot for instance .

Stations on the lofting could be struck the same distance apart as the thickness of the foam blocks .The individual blocks could be formed to their stations square across with a hot wire cutter that's available, then faired to each other after being glued together ,sort of like a lift model.

Maybe such composite construction will come into vogue when the best boat building woods get a bit scaircer.The wood used would be up above the chine where rot is less of an issue so a wider variety of our native lumber could be expected to last well .

I'd guess this approach in wood or foam is limited to boats with a small amount of dead rise in order to maintain stability . The foam of course could be hollowed down on the inside to lower the weight of passengers and equipment .This brings to mind a grander vision I have of hewing out one of the smaller documented Chesapeake log canoes in foam .The topsides on some are brought up to sheer height with lapstrake planking , the first strake being lapped over the hewn hull .I think this could look sharp and I need to make another pilgrimage to the Eastern shore to check some such boats out .As this is all above the waterline one would have no qualms about using sawn lumber lap planking even on a trailored boat .

[ 07-02-2003, 07:43 AM: Message edited by: Bill Perkins ]

[brian.cunningham]

Originally posted by TomRobb:
It looked like a rather round-about system to me. And all those unventilated chambers looked like a good place for rot to start. :rolleyes: Ditto, that's the part that scares me.
It could be addressed with drain plugs, but it's not.

[walleye]

I see two advantages to this double bottom method of building. First, you are creating a torsion box bottom- very rigid and strong. Second, the airspace would seem ideal for electric boats ( not just for outboard runabouts) by eliminating or at least reducing the requirement of a large amount of flotation foam in the interior of the boat necessary for safety. This would free up interior space for spatial comfort.

[Scott Rosen]

I'm with Tom and Brian. The method seems outright dangerous. What about leaks? First of all, there are no pumps in those chambers, so you wouldn't even know you had a leak until it started to affect the boat's performance. By then it may be too late.

but whatdoeyeno? I've only been hanging around wooden boats since I was four years old.

[Mark Van]

Phil Bolger has been using a similar method on the bow sections of flat bottom boats, check out "Topaz"

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