Hi,

I would like to know what is the difference geometrically between a full
ended and a fine ended hull? I was reading the John Winter's webpage
(http://www.greenval.com/jwinters.htm...cal%20articles) Part1
(Frictional resistance) in the effect of shape section and could not
understand what was the difference between these two types of hull. If you
have an image that could help me understand it would be great. Thanks for
your help in advance.

Pablo
remove213 for mail

On Tue, 28 Oct 2003 21:56:48 -0500, "Pablo"
wrote:

Hi,

I would like to know what is the difference geometrically between a full
ended and a fine ended hull? I was reading the John Winter's webpage
(http://www.greenval.com/jwinters.htm...cal%20articles) Part1
(Frictional resistance) in the effect of shape section and could not
understand what was the difference between these two types of hull. If you
have an image that could help me understand it would be great. Thanks for
your help in advance.

Pablo
remove213 for mail


A fine ended boat has a fine angle of entry and exit - meaning the bow
and stern, the ends, are pointy.
A full-ended boat has a wider angle, which means the ends are stubby.
That's all.

-m

As an amatuer boat builder, not having been properly schooled in the
mathamatics of nautical architecture, I would offer the idea that,
in general, a full ended hull would have a "U" shape to the cross
section at or near the waterline entry point and a fine ended hull would
have a sectional shape that is "V" shaped at the waterline entry.
The relationship of the sectional area at the waterline entry to the
flair and/or fullness of the bow is something that has provided me with
countless hours of thought and speculation. To reduce it to a numerical
quantity would seem to take the fun out of it.(just my approach)
I have been particularly intrigued with the effect
that these shapes have in controlling bow lift and boyancy and the
effect of throwing off spray with small boats...canoes, kayaks, etc.
The bow shapes of several of the designs of L.F. Herreshoff seem to have
mastered this effect and his balancing of fineness and flair at the bow
apparently work very well for the particular conditions designed for.
If you have access to the book "Sensible Cruising Designs" , look at
design number 98,"Rozinante" and design number 101"White Water Racing
Canoe" to see two variations on this idea.

Pablo wrote:
Hi,

I would like to know what is the difference geometrically between a full
ended and a fine ended hull? I was reading the John Winter's webpage
(http://www.greenval.com/jwinters.htm...cal%20articles) Part1
(Frictional resistance) in the effect of shape section and could not
understand what was the difference between these two types of hull. If you
have an image that could help me understand it would be great. Thanks for
your help in advance.

Pablo
remove213 for mail

The best single look at the fine/fullness of a hull is by calculating
the prismatic coefficient. This is a little complicated, so hang on:

a) determine the area of the largest midship section of the boat.
Multiply this by the waterline length. This gives you the volume the
boat would displace if it were as full as possible -- no taper at all,
bow or stern.

b) take the actual displacement volume -- usually you can get this by
dividing actual weight (not registry tons) by the weight of seawater
in the same units (64 pounds per cubic foot or 1025 kg per cubic
meter)

Divide a/b and you get a percentage. The naval architecture books
will tell you what the ideal prismatic coefficient is for boats at
each speed. It typically runs around 54% in displacement boats in the
size we usually talk about here.

Fintry's PC is 58.6%, a little larger because she's a little larger
boat. During our search for Fintry we turned down one boat,
Flintstone, primarily because her PC was very high. She was very
spacious, but would have had very high fuel consumption and been
uncomfortable. see http://www.mvfintry.com/boatsnotbought.htm

Steve's comments about "U" and "V" shape are only half the story --
you have to look at the plan (top) view as well as cross sections.

Jim Woodward
www.mvFintry.com


stevej wrote in message ...
As an amatuer boat builder, not having been properly schooled in the
mathamatics of nautical architecture, I would offer the idea that,
in general, a full ended hull would have a "U" shape to the cross
section at or near the waterline entry point and a fine ended hull would
have a sectional shape that is "V" shaped at the waterline entry.
The relationship of the sectional area at the waterline entry to the
flair and/or fullness of the bow is something that has provided me with
countless hours of thought and speculation. To reduce it to a numerical
quantity would seem to take the fun out of it.(just my approach)
I have been particularly intrigued with the effect
that these shapes have in controlling bow lift and boyancy and the
effect of throwing off spray with small boats...canoes, kayaks, etc.
The bow shapes of several of the designs of L.F. Herreshoff seem to have
mastered this effect and his balancing of fineness and flair at the bow
apparently work very well for the particular conditions designed for.
If you have access to the book "Sensible Cruising Designs" , look at
design number 98,"Rozinante" and design number 101"White Water Racing
Canoe" to see two variations on this idea.

Pablo wrote:
Hi,

I would like to know what is the difference geometrically between a full
ended and a fine ended hull? I was reading the John Winter's webpage
(http://www.greenval.com/jwinters.htm...cal%20articles) Part1
(Frictional resistance) in the effect of shape section and could not
understand what was the difference between these two types of hull. If you
have an image that could help me understand it would be great. Thanks for
your help in advance.

Pablo
remove213 for mail

Thanks for the answer, I really appreciate it.

Pablo,
"Pablo" wrote in message
. ..
Hi,

I would like to know what is the difference geometrically between a
full
ended and a fine ended hull? I was reading the John Winter's webpage
(http://www.greenval.com/jwinters.htm...cal%20articles) Part1
(Frictional resistance) in the effect of shape section and could not
understand what was the difference between these two types of hull. If you
have an image that could help me understand it would be great. Thanks for
your help in advance.

Pablo
remove213 for mail

Jim Woodward wrote:
Steve's comments about "U" and "V" shape are only half the story --
you have to look at the plan (top) view as well as cross sections.

I agree. The request was for an "image" though.