Some more on pitch and roll.

Do the calculations for motion comfort have any worth seeing as how
they don't seem to take hull design shape into consideration?
Or is this calculation only good to compare similar hulls.
Full keel to full keel etc
For instance, an Endevour 32 has a motion comfort of 30.29 while an
Endevour 33 only has a motion comfort of 23.48. Is this apples to apples
or apples to oranges?
Gordon

http://www.image-ination.com/sailcalc.html

....
Do the calculations for motion comfort have any worth seeing as how
they don't seem to take hull design shape into consideration?
Or is this calculation only good to compare similar hulls. ...

The basic premise of most comfort numbers is that boats with narrow
water planes are more comfortable than those with wide ones. All else
being equal (ha, ha), this is probably true, but I don't think the
differences are profound. Generally, comfort ratios are put forth by
folks who want to suggest that cruising boats should be narrow and, by
today's standards, heavy. It turns out that, as a class, multi-hulls
with their very narrow water planes tend to have good comfort ratios.
I'm a big fan of multihulls, so I get a kick out of this result.
However, I'd say that comfort rations are pretty much total garbage
because they ignore the dynamic nature of comfort. The trick to
getting a comfortable motion out of a small sail boat at sea is to go
slowly while carrying a good press of sail while avoiding sailing deep
down wind. Virtually all boats are comfortable when hove to with
enough sail up to keep them from rolling. As you let the boat head
reach it will get less comfortable as the speed increases. The
primary, indeed, as far as I can tell, only significant comfort factor
is speed as long as roll is controlled by keeping enough sail on.
So, if you have a slow boat it will tend to be comfortable because it
can only operate at comfortable speeds.

Folks with faster boats will notice that some speeds are more
comfortable than others. The reasons for this doubtlessly have
something to do with water plane loadings, pitching moments, reserve
buoyancy, wave periods and so forth. I'm sure a good naval engineer
could predict what speeds would give the best comfort to speed ratios
given enough time and a clear definition of comfort. However, the
problem is hard and I am extremely skeptical that a simple ratio will
be of much practical use. Also, the amount of comfort a crew will
demand may well depend on many factors (like the time to a hot shower
or the desire to win yet another silver plated punch bowl). In short,
no I don't think comfort calculations have any worth either for similar
or different hull types.

-- Tom.

The Endeavour 32 certainly deserves it's high rating. It's one of the most
comfortable boats I've sailed and certainly the most comfortable for it's
speed.

--
Roger Long

For what it's worth, I just checked his speed predictions and my E 32 goes
significantly faster under power than he predicts.

--
Roger Long

The Endeavour 32 certainly deserves it's high rating. ...

Oh aye, who could argue that the 32 anything but 6.81 more comforts
(pounds per feet to the two-thirds) than than the 33?

Seriously, the E 32 is a fine boat but the comfort number in and of
itself is BS. Brewer talks about the CR on his web site
http://www.tedbrewer.com/yachtdesign.html and says "This is a ratio
that I dreamed up, tongue-in-cheek, as a measure of motion comfort.."
He goes on to rationalize about how it might be valid anyway, but fails
to note that he is not at all disinterested in this since his narrow
heavy and slow designs compete directly with the notably wider, lighter
and faster designs. His formula puts "super heavy vessel[s], such as a
Colin Archer ketch" at the top of the comfort scale. Such vessels are
unlivable running deep in a seaway or riding out a calm, and they
manage to be slow and unweatherly as well. Can they really be the
pinnacle of comfort?

-- Tom.

I agree. Looking at the link to Brewer's explanation of CR, I would consider
it a measure of *potential* comfort that may or may not be lived up
according to other aspects of the design.

Did you read my piece on research vessel comfort linked to in the "Rocking
and Rolling" post? Same situation with sailing vessels. Comfort is highly
subjective and situational.

When our E32 arrived on the truck I noticed the full bow lines and started
thinking, Oh, my gawd, did I buy a pig? How did I not notice that out in
Detroit? Would I have bought her if I had? After two seasons of watching her
working her way through seas and finding her the driest as well as the most
comfortable boat of her size and speed I've ever sailed, I'm convinced those
bow lines have a lot to do with it, especially the dryness.

I'd always wondered why the British, sailing in such challenging and
unforgiving conditions, seemed to favor boats which seemed to have such
unsuitable characteristics. Cutting my cruising teeth in catboats as I did,
I had always favored powerful, asymmetric, hulls. When you positively,
absolutely, must be somewhere to windward overnight, something like a
Friendship sloop seemed just the ticket. How did the Brits all avoid getting
blown to France?

Strider has a lot of those British characteristics, modest stability, narrow
symetric and easily driven hull, and apple cheek bows. She heels much
farther than the boats I'm used to but the knotlog hardly changes as she
heels from 20 to 30 degrees. Heel creates almost no steering effects on the
hull although helm force does increase. The comfortable motion preserves the
crew's strength and the fact that large heel angles don't slow her down
makes her quite forgiving. Failure to head up enough to maintain a modest
heel angle doesn't cost much in speed and keeping the water flowing briskly
over the rudder helps maintain control. With her modern quick helm response,
she is an easy and enjoyable boat to keep moving to windward in tough
conditions.

It's been an education sailing her and challenged a lot of assumptions I'd
carried with me as a designer for decades.

--
Roger Long

Roger Long wrote:
....
Did you read my piece on research vessel comfort linked to in the "Rocking
and Rolling" post? Same situation with sailing vessels. ...

Yes I did. Very interesting, it was, too. I have not looked at OSV
designs. Aren't they typically moderately narrow semi-displacement
boats? I assumed that, given the daily rates, speed in a seaway was
of primary concern rather than comfort.

Comfort is highly
subjective and situational.

Absolutely!

....
I'd always wondered why the British, sailing in such challenging and
unforgiving conditions, seemed to favor boats which seemed to have such
unsuitable characteristics. ...

Are we talking Cornish Crabbers or foiling Moths?

-- Tom.