Jim,
Do you know what the outermost lamina is? Glass or something
more exotic?
Tod
Jim,
Do you know what the outermost lamina is? Glass or something
more exotic?
Tod
The outermost laminate is the standard mat but using vinylester resin. The
difference is the belting of the entire hull with Kevlar 49 in the third
layer and in the innermost layer, along with overlapped Kevlar collision
mats at the stem and the leading edge of the keel. We are also decreasing
panel size in the hull by adding longitudinal stringers, aprons and adding a
collision tank in the forepeak.We will use Vinylester for the entire
laminate. Total additional hull weight is 400 lbs which we calculate to sink
the hull by one inch. Hope to get it back by foregoing pressure water and
lightening up the interior
“htmills@bright.net ” wrote:
Jim,
Do you know what the outermost lamina is? Glass or something
more exotic?Tod
BRISTOL CHANNEL CUTTER OWNERS ASSOCIATION
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Jim,
I was surprised to hear that 400# was expected to sink the hull by 1" so I
did some quick calculations. Obviously, since I am not privvy to the details
of the BCC lines I had to guesstimate at some numbers.
Working backwards, I calculated the waterplane area required:
64#/cuft x ?sqft x 1ft/12in = 400#/in
or, 400x12/64= area of waterplane in sqft
area of waterplane =75 sqft
Then, from the Sam L. Morse web page I got a waterline beam of 10’1"
and an LWL of 26’3". Those two numbers multiplied give an area of about
265 sqft.
That would mean that the waterplane area acually occupied by the boat is
75/265=0.28, or 28% of the circumcribing rectangle. That number strikes
me as low, although I don’t have anything handy to compare it to. I would have
expected something more than twice that big. (or conversely, that the boat would
sink less than half as much)
Tod
I think that the factor that you need to reassess is the waterline beam. 10’1" is
deck beam not waterline beam, which is actually considerably less, leading to a
lower prismatic coefficient.
The 1" sink is based upon design displacement which probably has little relation to
reality because of all of the changes made to the boats over the years.
It would be fun to actually see what has happened to the waterlines of all of the
boats out there
I understand that one Gentleman put 2000 lb. of books onboard before he took off.
It’s been an interesting experience working with Ray Richards. He was the designer
of the Alajuela series of sailboats. Very much of an "old school " designer. Lots of
sea miles and well versed in what works at sea.
He is most impressed by the BCC and its structural integrity.
I also own a Valiant 50 and Richards believes that boat for boat the BCC is
considerably more rugged. I don’t know because the Valiant is built like a brick but
my point is that the BCC is a very honest and tough little boat. Originally I
purchased a new Contessa 32 to make this trip in. Also a nice little boat but not in
the same league as the BCC.After putting a few thousand miles on the Contessa I sold
her and focused on the Bcc to do the Arctic trip.
Jim
“htmills@bright.net ” wrote:
Jim,
I was surprised to hear that 400# was expected to sink the hull by 1" so I
did some quick calculations. Obviously, since I am not privvy to the details
of the BCC lines I had to guesstimate at some numbers.Working backwards, I calculated the waterplane area required:
64#/cuft x ?sqft x 1ft/12in = 400#/in
or, 400x12/64= area of waterplane in sqft
area of waterplane =75 sqft
Then, from the Sam L. Morse web page I got a waterline beam of 10’1"
and an LWL of 26’3". Those two numbers multiplied give an area of about
265 sqft.That would mean that the waterplane area acually occupied by the boat is
75/265=0.28, or 28% of the circumcribing rectangle. That number strikes
me as low, although I don’t have anything handy to compare it to. I would have
expected something more than twice that big. (or conversely, that the boat would
sink less than half as much)Tod
BRISTOL CHANNEL CUTTER OWNERS ASSOCIATION
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I suspect a better approximation may be calculated by multiplying the beam X the waterline length in feet by the prismatic coefficient. Let's assume the prismatic coefficient is 0.55
Then
10.08 X 26.33 X 0.55 = 146 sq. ft. "water plane"
Displacement for 1" of immersion is 146 sq. ft.X 1 in./12 in/ft X 64 lb/cu. ft = 779 lb.
If we assume the prismatic coefficient is less, let's say 0.53 then displacement for 1" of immersion is 750 lb.
Based on these calculations, I believe a good approximation of displacement for the first 1" of immersion of the hull above the water line is between 750 and 775 lb. As hull immersion increases, displacement increases.
S/V IDUNA
P.S. IDUNA is scheduled to be "splashed" the week of July 9th, 2001.

Jim,
beam…ah, yes, I misread the web page. Thanks.
Even assuming a waterline breadth of just 8’ still gives what
seems like a low ratio, but oh well, no matter.
Tod