Stone cold sober,

I was just browsing boat design net. I enjoyed the thread you started about ply versus infusion you started and Rob contributed to. I learned some things and was more convinced of intel infusions benefits. So i just looked for your otgher posts and saw where you seemed to say that you had no intention to build a boat but was going to buy instead.
This was one where you asked about paylaod and finished weights and Woods replied.
So was that whaf you meant and have you changed uour mind? Did the sound of using intel infusion make building seem not such a bad idea?
Personally i would stay with idea of buying unless you wanted an HP which could not probably be bought second hand anywhere yet.

Doug
--------------------------------------------
On Tue, 26/6/18, StoneTool owly@ttc-cmc.net [harryproa] <harryproa@yahoogroups.com.au> wrote:

Subject: [harryproa] cedar strip versus infused sandwich
To: harryproa@yahoogroups.com.au
Received: Tuesday, 26 June, 2018, 11:43 PM


 









    I'm sure folks are getting tired of
hearing about my proposed cat

project.   I'm still sort of going in circles as far
as deciding exactly

what to build, and have acquired several sets of study
plans.   The boat

that comes closes to fitting my criteria "out of the
box" so to speak,

is the Woods  Sagitta, which unfortunately due to it's
cedar strip hull

and knuckle, does not lend itself well to any sort of
"intelligent

infusion".  There is no "easy way".  The
choices are to build using

strip planked foam (or cedar), hand finishing, and infusing
the interior

and exterior separately, or building a half hull plug, hand
finished,

and pulling a female mold off that............ NOT an
attractive

proposition, and one that would require a huge amount of
labor that

could only be justified by molding multiple hulls from
that.........

Something I have no desire to do.  I want to build a boat,
not a business!



    In looking at  Richard Woods designs, I stumbled
across an

interesting thing.    Two boats that are in his
description essentially

the same boat, one in cedar strip (hull and cabin top), and
one in

plywood.   The cedar strip boat was 12.5% lighter than the
plywood

boat.   The boats are the next size up from what I'm
looking at.  

Slightly different in length due to different bow shape, and
ranging

from 14" longer to 2' longer than Sagitta.   The
shorter boat (Tamar),

at 14" longer than Sagitta and very similar in many
ways is 1200kg

(2640) heavier than Sagitta, offering nothing that is of
interest to me

except 300kg additional payload.  It is of plywood.   The
Eclipse being

the longer of the two is lighter than Tamar by 250kg, and
the only thing

I can point to that would explain the difference is plywood
construction.



    The implication here is that cedar strip construction
offers about

half as much weight reduction potential as infused foam
sandwich, at a

far lower cost in terms of materials (here), but a far
higher cost in

terms of labor (presumably)  That suggests that the
potential savings on

Sagitta's empty weight using strip plank infused foam
and infused foam

panels as compared to strip planked cedar and plywood should
only range

somewhere between 135kg and 225kg (about 300-500 pounds). 
That hardly

justifies the additional cost in materials (all else
aside)



                             
*********************************



    On a parallel track, I've been working out how to
stretch the KD860

to 30' without getting into a lot of highly complex
calculations,

etc.    It is not a simple matter of adding a percentage
between each

bulkhead or some such strategy, as the construction is flat
sheet, and

the end result is that the skin must lay properly on the
bulkheads. 

Essentially the hull sides must be some part of a
theoretical cone

shape.    The process begins with laying out the flat
hull bottom at a

reduced scale. For convenience 10%, maintaining the straight
slope of

the forward end, and very slightly increasing the aft
radius, setting up

the widths as appropriate at the bulkheads, and using  a
piece of light

weight plywood or heavy construction board to adjust and
ensure that

everything lays properly.  The bottom as laid consists of
horizontal

sticks where the bulkheads will be, and a vertical central
rib at right

angles to each of these members gives a reference to work
from.    Once

the bottom is laid, construction board is laid against the
bottom

members, and flared to the desired width at the sheer line
from bow to

stern.  Once the desired shape is achieved and made fair,
verticals and

horizontals are added at each bulkhead location, creating
half bulkhead

templates to scale.  Actual scale bulkheads are made from
these and

mounted inverted, using a strongback screwed to the
workbench, and the

actual scale model made from them.  Once a satisfactory
result is

achieved, the 10% bulkheads can easily be scaled up to full
size.



    As I'm not actually ready to build the boat, I
have plenty of time

to mess about with this.   I don't do TV, etc, so my
spare time is

dedicated to projects anyway.   It's my nature to work
with my hands and

brain, and calculator.   I'm not quite set up to do
this model project

yet..... I intend to build a project table specific to this
model.     I

tend to spend a lot of thought time, working out the methods
before

cutting wood.    In the end I've found that this
saves me a lot of time

going down "blind alleys" and redoing things.



H.W.













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