Re: [bolger] Hulls for lapstrake vs stitch and glue

The moment of enlightenment for me came with a little sketch in the corner
of one of the Chebacco drawings. The table of offsets defines a smooth
hull. The inside of the lapstrakes are tangent to the outside of this shape
at their bottom edge. Their top edge, after beveling, is inside the defined
hull shape.

I laid out the strakes with Hulls and then added 3/4" to the top on the
plywood before cutting them out. I left an inch or so at the bottom edge
for error correction once they are hung on the molds. Tedious and maybe
overkill, but I don't have much faith in my "lining off" skills.

We'll know soon.

Roger (still spreading epoxy and fiberglass on the strake blanks and
sanding and sanding and sanding)
derbyrm@...
http://home.earthlink.net/~derbyrm

----- Original Message -----
From: "Bruce Hallman" <bruce@...>


> On 9/25/05, Rob Mouradian <r_mouradian@...> wrote:
>> To interject a question here, if you input data from a table of offsets,
>> do the
>> expansions assume that the panels wll just butt up against each other, as
>> you
>> would want for stitch and glue? If so, how do you account for the
>> over-lap of
>> lapstrake construction?
>
> For my Cartoon 5 experiment, I actually had the flat edge of
> each strake input as a surface. I didn't input all the data
> from the table of offsets, but rather mostly just dragged the
> lines around with a mouse. [using Hulls.exe]
> Spot checking for reasonableness against the table
> of offsets.
>
> I know it sounds tedious, but with practice is it quick. The
> Hulls.exe data entry for Cartoon 5 took less than three hours.
>
> In truth, I suspect that the thickness of the strake is
> inconsequential, as I used 1/8" luaun plywood.
>
> Also, as a though experiment, it has crossed my mind that the
> strakes could be laid out without thought to the strake
> overlap, and then the curvature could be adjusted by 'eye'.
>
> Imagine each strake with it's general 'banana' shape, you
> could compensate by increasing the depth of the 'banana'
> curve by one inch to allow for the increased curve caused
> by the overlap.

On 9/25/05, Rob Mouradian <r_mouradian@...> wrote:

> To interject a question here, if you input data from a table of offsets, do the
> expansions assume that the panels wll just butt up against each other, as you
> would want for stitch and glue? If so, how do you account for the over-lap of
> lapstrake construction?

For my Cartoon 5 experiment, I actually had the flat edge of
each strake input as a surface. I didn't input all the data
from the table of offsets, but rather mostly just dragged the
lines around with a mouse. [using Hulls.exe]
Spot checking for reasonableness against the table
of offsets.

I know it sounds tedious, but with practice is it quick. The
Hulls.exe data entry for Cartoon 5 took less than three hours.

In truth, I suspect that the thickness of the strake is
inconsequential, as I used 1/8" luaun plywood.

Also, as a though experiment, it has crossed my mind that the
strakes could be laid out without thought to the strake
overlap, and then the curvature could be adjusted by 'eye'.

Imagine each strake with it's general 'banana' shape, you
could compensate by increasing the depth of the 'banana'
curve by one inch to allow for the increased curve caused
by the overlap.

To interject a question here, if you input data from a table of offsets, do the
expansions assume that the panels wll just butt up against each other, as you
would want for stitch and glue? If so, how do you account for the over-lap of
lapstrake construction?

Regards

Rob