What is the 'speed to length ratio"? Are you referring to square root of the
waterline?

Paul
www.jcruiser.org
"Tom Webb" wrote in message
om...
Glenn Ashmore wrote
Matt/Meribeth Pedersen wrote:
In passagemaking, I don't see the moderate displacement boats
burning up the miles significantly faster than the heavy displacement
ones.
I do think that you need to have adequate sail area to make a decent
passage, but when you're cruising, trying to keep the boat speed up
over
about 1.2 sqrt WL is just too much trouble. As long as you are
powered up, then waterline length is going to govern.
Half a knot to a knot means a lot on a passage. That is 12 to 24 miles a
day which adds up pretty nicely on a 5 or 6 day run. Most of the time
you are not going to be driving at hull speed so a boat that can easily
be driven in light winds has a definite advantage. OTOH, the quicker
motion of the medium displacement boat can get a bit tiring.

I have spent the last three years cruising the Pacific in my 42 foot
medium displacement catamaran and I have observed the cruising fleet
closly. A speed to length ratio of 1.2 is very fast for passages
outside of the trades (eg. the islands to New Zealand). Most couples
sail and motor their boats to an S/L of about 0.8 over time, but many
are slower and few are much faster. Heavier boats are typically
motored more often and at higher speeds than lighter ones, so the
daily runs are similar. Some couples who don't like sailing as such
and aren't very advanced sailors love long term cruising and some very
good sailors don't. Most cruising is done at anchor anyway. It's
hard to know what kind of boat will meet your needs best before you
get into the life style, and, given all the boat modification that I
see in New Zealand, I'd guess that most folks don't guess exactly
right. I think a cruising boat should at the very least have a dry,
warm place to stand watch and the ability to make ground to weather in
20-25 knots of wind without beating the crew up very much. However,
given the right attitude and a bit of good luck, most any boat will
get you where you want to go.

BTW, motion in a seaway is largely a function of a small waterplane
area to displacment. Multihulls, with their narrow hulls, can make
comfortable sea boats even at light displacements.

Cheers,
-- Tom.

"Paul L" wrote in message ...
What is the 'speed to length ratio"? Are you referring to square root of the
waterline?

Paul


Yes, the speed to length ratio is the speed of the boat divided by the
square root of it's sailing length. The units are feet and knots.
The ratio gives a feel for how fast a boat is when corrected for
length. A speed to length ratio of 1.34 is the speed of the wave that
has a length equal to the sailing length of the boat and is called the
"hull speed". Hull speed is a topic that has been discussed to death
on this board in the past, but you could google it if you really want
to know. Anyway, the speed/length ratio comes out in weird units
(feet per radical knots) so it has been replaced by the Froude number
in most new work...

Cheers,

-- Tom

In article , Bart
wrote:
I have a TY37, so consider that I have a bias towards them.
Are boats like the Tayana 37 still popular and still a good choice for
ocean crossings?
Yup, they are still popular. A 'good' one will only take a week or two
to sell. The Tayana yard just delivered a new TY37 pilothouse - still
in production but obviously not as in demand as before .... design is
getting a little ' long in the tooth' and is subject to poor prior
maintenance.

I've crawled in and out of a few boats during the past couple weeks
and it looks to me that the heavy displacment boats are just built a
lot better than the mid to light displacement ones. This is
especially true in the price range I can afford (less than $100k).
I would say that 'heavies' are too overbuilt. The laminate schedules
are probably waaaaaaaay to thick and were produced in a non-continuous
process resulting in a much thicker but ultimately weaker structure
than by todays standards of good yards. Until recently, yards would be
on an ~8 hour basis, leaving the uncompleted laminate to cure overnight
before starting again the morning. The result is a weak bond between
the partly cured layers. Ultra-modern layup is vacuum bagged, almost
continuous, and may even be done under refrigerated conditions to
ensure a complete bond between layers. The result is vastly stronger
and much lighter weight structure.

Most of the heavy displacement boats also have more storage because
the tanks are usually located in the bilge leaving the settees free
for storage. This appears to be another plus.
Nah.... most of the heavies NEED tank-ballast in the bilge because they
have encapsulated keels (of cement and iron, etc.) ..... making the
the underwater profile of keel ***width*** to length somewhat
ridiculous by todays standards. Personally, I think most of the
'heavies' are too 'top-heavy' also.

When comparing open ocean vessels, Is the performace between a heavy
and mid displacment boat really all that much different? If not, then
maybe I wouldn't get bored with a lower performance heavy displacment
vessel. I'm not sure about this and would like comments.
Yes there is a significant difference. An easily driven lightweight
hull typically depends a lot on form stability (beam, etc.) while the
'heavy' depends more on ballast. The lighter weight is more easily
driven, allows a vastly smaller sail plan (usually a fractional rig),
accelerates faster when tacking, etc. Heavies are usually old fashioned
spoon bowed - resulting in a shorter waterline length, while light
weights are usually 'knuckle bowed' - longer water line length =
FASTER. A heavy will usually have a slower roll period while the
lightweight will be have a much faster roll period .... choice depends
on which roll period makes you puke. Especially when loaded in the
ends, a short water line length heavy will hobby-horse more than a
knuckle-bowed, fat assed lightweight.

Most heavy displacement boats have bow sprits. If a boat has a 5'
bowsprit, do you add that into the total length of the boat when
computing moorage charges? It would be ashame to get charged for 42'
when the boat is only has 37' on deck and 37' of living space.
Huh? you live in the cockpit.... the 'living-space' is for stores.
A TY37 is ~43 LOA .... but when coming into a marina, I just tell them
its a Tayana 37 and let the sprit hang out in the fairway, most marinas
are too lazy to look ... all they hear is 37. I have a 'fold-up' stern
davit that removes another 4 ft.
Buy a good set of anchors and dinghy in.

As you can see, I'm still having trouble finding a suitable boat. I
want something to liveaboard here in Alaska and in 3 years take off
and at least sail the S. Pacific if not farther.
If you're not out to beat any trans-ocean speed records, a heavy will
do just fine. Its the total miles not the speed of passage that
counts. Need to get there faster, take a plane. If you need to show
off, get a Donzi or a Hobie.

A well prepared heavy: faired hull and keel, baby's-ass smooth bottom,
feathering prop, well cut and well set/shaped sails, etc. will be an
incredible performance boost on any 'heavy', especially for light air.
A cutter rig with a removable jibstay is great for 'coastal' work, just
dont believe ANYTHNG you've ever read about the disadvantages of a
staysail. .... all BS. If you opt for a cutter, get a staysail boom,
just keep your knees and head clear A boomed staysail (needs a vang)
is self-tacking, keeps its shape on a reach, run, etc. - learn to
become an instant flat-spot on the foredeck if all goes wrong.

Most 'heavies' you find will have the bottom smoothness of a hand-laid
tarmac or dirt road - bottom paint put on with a GD thick knapped
roller, through-hulls sticking out all over the place like carbunckles,
a 3 or 4 blade fixed prop (might as well drag a wash tub), the sails
will usually be beyond blown-out bed sheets, all the weight in the bow
and stern ..... typically Winnebagos with sails.
Light winds.... no problem for heavy with a smooth/fair bottom and good
sails. I occasionally race my TY37 'tub' with quite surprising results
(boat is highly underated by PHRF). Once you get up to hull speed, it
doesnt make any difference if its a heavy or a light weight, although
the modern lightweights can point MUCH better.

If you have any racing experience, apply that to a 'heavy' and you have
a secure, relatively fast (not a racehorse), safe passagemaker.
Consider Robert Perry, Robert Harris, etc. designs .... proven designs.
More Perry designs have circumnavigated than any designer: Tayana,
Tashiba, Baba, Valiant, Passport, etc. etc. .... that ought to tell
you something.
If I had it to do all over again, I'd opt for external ballast, split
underbody with a balanced spade rudder. If I were in the market for a
brand new blue-water boat, I really lean towards a deep fin external
keel (with a not-so-flat bottom), with a balanced spade rudder (perhpas
giving up the supreme advantage of being able to totally heave-to in
quiet stability). I dont think that 'weight' buys you anything.

My ultimate 'dream boat ' would be a Millennia (or Tollycraft)
**FastPassage 39**, (PHRF ~115). A faster boat can 'avoid' the
weather a little better.
Stay away from the old 'rule beaters' - narrow / short waterline
lengths, etc. Once you narrow your choice, go to the design-specific
email discussion groups on Sailnet, etc. and do a detail archive search
for the 'problems'.

;-)

Bart wrote:
Are boats like the Tayana 37 still popular and still a good choice for
ocean crossings?

It depends on who you ask.


I've crawled in and out of a few boats during the past couple weeks
and it looks to me that the heavy displacment boats are just built a
lot better than the mid to light displacement ones. This is
especially true in the price range I can afford (less than $100k).

Bzzt, sorry to disagree, but I can offer positive proof that it ain't
so. Chipboard bulkheads and chopper gun fiberglass are very heavy and
can be very thick but will never be strong for marine structures... and
you see a lot of that kind of thing on the lower priced heavy
displacement cruisers.


When comparing open ocean vessels, Is the performace between a heavy
and mid displacment boat really all that much different?

Depends very much on the sailor & on the conditions.


maybe I wouldn't get bored with a lower performance heavy displacment
vessel.

Well, it sounds to me like you are very much in favor of the heavy
displacement boats and are trying hard to stretch a point. Go for it.

BTW don't think I am being insulting, I am a racing sailor and generally
see no use in heavy displacement boats except for people who would be
better off with a trawler. I happen to also own & cruise in a trawler.

Fresh Breezes- Doug King