Hi,

I'm currently investigating the idea of building a carvel hull
completely out of plywood. Ribs, strakes etc all from plywood. The
interesting thing to me is can I do all the work up front and have the
plywood milled on a CNC machine. The hull should then be easy to
assemble.

I've seen various clinker/lapstrake hulls built for small rowing skiffs
that seem to implement the idea pretty well.

I've also played around with scale models I've designed and everything
seems to work out.

The current problem is how to work out bevels for both the ribs and the
strakes. Is there a formula for this? Ideally the more general the
solution the better e.g. would work for a scale model as well as the
full size.

If I suggested that the cross-product of a vector tangent to the edge of the
strake and one on the surface will be a normal to the strake at the point of
tangency, and that the cross-product of the two normals will give the angle
between them, would it help? (Half that angle is the bevel unless you
intend to shape the seam for later caulking.)

Roger

http://home.insightbb.com/~derbyrm

wrote in message
ups.com...

The current problem is how to work out bevels for both the ribs and the
strakes. Is there a formula for this? Ideally the more general the
solution the better e.g. would work for a scale model as well as the
full size.

Barend Migchelson shows how to do it for dories with just the Pythagorean
formula. He's in Dorval (Montreal), Canada and has a website
I worked it out for skiffs using analytical geometry and put it in a
program for flat bottom skiffs at www.ncf.ca/~ag384/Boats.com.
You should be able to do quite well with a protractor and a wire frame
diagram produced by a (free) hull design program like the one at
www.carlsondesign.com which is for plywood boats and will draw and list the
points to plot for cutting out the plywood panels as well.

Hi

It is offcaurse interesting to be able to make these ,but what
equipment do you think will be able to cut and at the same time angle
the cut ?
Also With my experience it is allright to project a boat with huge
panels ,but expecting the most fragile part of the plywood ,-- the
edges -- to work as how real wood worked in the old day's ; that I find
unrealistic.

With small boats these bevls are much easier done on site --------
beside I don't belive you when you say you looked at various lapstrake
designs, as esp. with lapstrake the bevels are done just before you
place the next plank and the material are removed from only one plank,
the one that is there before you place the next aso..

BTW. --- untill this day I havn't seen one single lapstrake design that
as 3D model been used to unfold the planks ; most tradisional plans _do
not_ show the overlaps ; then emagine you unfold planks from a smooth
surface 3D model ,they will be another shape than if unfolded from a
real 3D lapstrake model; they will proberly build a boat but not the
one in your plans.

The exception are Cyber-Boat search for that and you will find
free.download plans that is generated from real 3D lapstrake models.

http://groups.yahoo.com/group/Cyber-Boat/

The current problem is how to work out bevels for both the ribs and the
strakes. Is there a formula for this? Ideally the more general the
solution the better e.g. would work for a scale model as well as the
full size.

Sorry, I misread the OP and thought it was plywood stitch-and-glue
construction. On these boats people tend to putty the seams and ignore
bevel. Some run a saw along the seam to get a closer fit.

Carvel hull boatbuilders took bevels off the lofting diagrams.
I think you could get them off the drawings from hull design programs.
There are some free ones you could try. Do a search on Blue Peter Designs
for one that I knwo of. Or go to ww.boat-links.com.