Here is where I got the formula on the Harken site. About 2/3 down the
page:
http://www.harken.com/winches/wnchpower.php

It is also in Brion Toss's Riggers Apprentice on page 42. (Almost
verbatim from the harken site.) OTOH, when you look at the tables a 56
or 64 is the recommended size for a 500 sq ft foretriangle.

I wish to heck I knew what a Newton is. All the really authoritative
modern texts are metric!



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On Tue, 16 Sep 2003 19:41:47 -0400, Glenn Ashmore
wrote:

Here is where I got the formula on the Harken site. About 2/3 down the
page:
http://www.harken.com/winches/wnchpower.php

It is also in Brion Toss's Riggers Apprentice on page 42. (Almost
verbatim from the harken site.) OTOH, when you look at the tables a 56
or 64 is the recommended size for a 500 sq ft foretriangle.

I wish to heck I knew what a Newton is. All the really authoritative
modern texts are metric!

Hold a good sized apple in your hand: that's a force of 1 newton
you're holding it up with - a little under a quarter pound.

Brian W

On Tue, 16 Sep 2003 19:41:47 -0400, Glenn Ashmore
wrote:

I wish to heck I knew what a Newton is. All the really authoritative
modern texts are metric!

It's a brown, square little cake stuffed with Fig guts about 1/2"
thick and cut square on two sides like it's made in one continuous
tube and they slice it ever' so of'n.

They also got 'em in Strawberry, Blueberry an' Raspberry, but I
suspect the Fig ones'll always win out from the traditionalist buyers
who are addicted......and my two parrots.


Larry W4CSC

3600 planes with transponders are burning 8-10 million
gallons of kerosene per hour over the USA. R-12 car air
conditioners are responsible for the ozone hole, right?

"Glenn Ashmore" wrote in message
...
Here is where I got the formula on the Harken site. About 2/3 down the
page:
http://www.harken.com/winches/wnchpower.php

In this case I think Harken is just off. They use an example of a 300 sq.
ft headsail (nearly the size of the genoa on my last boat, a 30' cutter) and
conclude you need a 50:1 winch. I don't think so. The winch was a 2 speed
32:1 and was fine. Yes, it was a bit of effort in a stiff breeze - but you
could still wind it in.

The usual formula for sheet loads is

F (lbs) = 0.00431 A(sq. ft) V^2 (knots)

There are some frictional losses through sheet blocks but not that much,
perhaps 10%.

I think 56's would be more than fine for your 505 ft foresail. If they are
self tailers, and you use a 2 handled winch handle, they will be a breeze
for smaller crew members.

by the way in case you were not kidding:
1 N = .0981 kg i.e. about 0.1 kg force or about 0.2 lbs


--
Evan Gatehouse

you'll have to rewrite my email address to get to me
ceilydh AT 3web dot net
(fools the spammers)

On Tue, 16 Sep 2003 19:41:47 -0400, Glenn Ashmore
wrote:

snip
I wish to heck I knew what a Newton is. All the really authoritative
modern texts are metric!

Try....

http://www.savardsoftware.com/masterconverter/

....a good little software converter that allows you to quickly change
variables to begin to grasp the units of measure.
---
Max and Hillary, sitting in a tree; Cay-eye-es-es-eye-en-gee.

I agree with Evan -- Harken is way off.

The formula Evan quotes is the same one I quoted above. As I noted,
it's been used by Skene (Kinney), Van Dorn, Henderson, Marchaj, and
many others.

The trouble with the Harken formula is that it doesn't specify a wind
speed. Since sheeting force varies with the square of wind speed,
that's a vital part of the choice of winch size. If you really expect
to carry a full foretriangle at 40 knots, then the Harken formula is
fine. That, however, suggests that at ten knots you'll be grossly
undercanvassed -- that you could carry sixteen times more sail than
you have.

Put another way, the difference between a 56 and a 66 is 18% in power.
Since the sheeting force varies with wind speed squared, a sail that
is easy with a 56 at 20 knots would require a 66 at 21.7 knots. Since
this is a very subtle difference, the only way to do this is for you
(Glenn) to do the math. Look at the rig you'll be carrying at each
wind speed, calculate the sheet loads with the Evan's formula and make
a decision.

Your naval architect can provide a table of her ability to carry sail
at various wind speeds up to bare poles at around sixty knots.
Beware, these are probably high -- my experience with several boats,
including Swee****er (Swan 57 by Sparkman & Stephens) was that we
never carried as much sail as they said we could. We were, of course
cruising shorthanded, not racing.

For my money, they are far better places to put money in a cruising
boat than in big winches. Dee (wife and crew for 37 years) would
agree, and she's the one who has to be perfectly happy reefing,
tacking, whatever, alone at night, in a blow, without waking me.

(I should add, however, that there are limits. The sailor who goes
out with grossly undersized winches and tacks by luffing while
sheeting, risks breaking the winch or ripping it out of the deck in
puffs.)

Jim Woodward
www.mvfintry.com

"Evan Gatehouse" wrote in message ...
"Glenn Ashmore" wrote in message
...
Here is where I got the formula on the Harken site. About 2/3 down the
page:
http://www.harken.com/winches/wnchpower.php

In this case I think Harken is just off. They use an example of a 300 sq.
ft headsail (nearly the size of the genoa on my last boat, a 30' cutter) and
conclude you need a 50:1 winch. I don't think so. The winch was a 2 speed
32:1 and was fine. Yes, it was a bit of effort in a stiff breeze - but you
could still wind it in.

The usual formula for sheet loads is

F (lbs) = 0.00431 A(sq. ft) V^2 (knots)

There are some frictional losses through sheet blocks but not that much,
perhaps 10%.

I think 56's would be more than fine for your 505 ft foresail. If they are
self tailers, and you use a 2 handled winch handle, they will be a breeze
for smaller crew members.

by the way in case you were not kidding:
1 N = .0981 kg i.e. about 0.1 kg force or about 0.2 lbs

On Tue, 16 Sep 2003 23:52:22 -0700, in message

"Evan Gatehouse" wrote:


"Glenn Ashmore" wrote in message
...
Here is where I got the formula on the Harken site. About 2/3 down the
page:
http://www.harken.com/winches/wnchpower.php

In this case I think Harken is just off. They use an example of a 300 sq.
ft headsail (nearly the size of the genoa on my last boat, a 30' cutter) and
conclude you need a 50:1 winch. I don't think so. The winch was a 2 speed
32:1 and was fine. Yes, it was a bit of effort in a stiff breeze - but you
could still wind it in.

You need to check the page again. The recommendation is based on the
size of the *foretriangle*, not on the size of the headsail. My
*foretriangle* is just over 300 square feet and the Lewmar 46s are a
good match for the loads all the way from the blown out 150% down to
what some of my chums refer to as my "cocktail jib" (short hoist for
about 80% of the foretriangle area).

The usual formula for sheet loads is

F (lbs) = 0.00431 A(sq. ft) V^2 (knots)

Both the sheet load and the driving forces will scale with V^2. If one
assumes that one will shorten sail at higher wind speeds to maintain
similar power levels, then the sheet load will remain similar as the
wind speed increases. If one then assumes that boats will carry
foresails with size being a similar fraction of the foretriangle at
similar wind speeds, then the loads will scale with foretriangle size
from boat to boat.

I think 56's would be more than fine for your 505 ft foresail. If they are
self tailers, and you use a 2 handled winch handle, they will be a breeze
for smaller crew members.

Probably. Note that a 505 square foot genoa would be 150% of a 335
square foot foretriangle and match the recommendation pretty closely
with a 56:1. OTOH, the 505 square foot storm jib of a MUCH bigger boat
would carry much higher loads and require more mechanical advantage.

by the way in case you were not kidding:
1 N = .0981 kg i.e. about 0.1 kg force or about 0.2 lbs

9.81 N is the force of gravity on a 1 kilogram mass near the earth's
surface, so 1 N is the weight of a mass of 0.10 kg or 0.22 lbs.

Ryk

--
Unfortunately this address has been overrun by SPAM.
If you want to be sure I see email from you, then
please include the words "Ryk says it's OK" somewhere
in your message.

On 15 Sep 2003 23:58:55 GMT, in message

ospam (Ilv2sl) wrote:

My question should have been, Has anyone with a 1sp. main halyard winch, found
they would like to have a 2sp winch. Just refering to mailsail luff tensioning,
not hoisting aloft, etc.
I have both a Barient 16 ss 1sp. winch, and a Lewmar 16 chrome 2sp, and have to
decide which one to install, and which to sell. The Barient is in excellent
condition, and the Lwemar is new.
So, do any of you 1sp. users feel a 2 sp. would be the way to go?

I have a 35 footer with E=39.25' for the hoist of the main. I find a
single speed direct drive winch quite adequate to the task with an
advantage of about 10:1. Then again, I also find it quite adequate for
hoisting my 180 pound son to the masthead.

If both your winches have the same ultimate advantage (16:1?) then
there's probably no bonus to having the faster speed on the two speed
winch unless you are grinding your sail up the mast rather than hand
hoisting it nearly to the top.

Ryk

--
Unfortunately this address has been overrun by SPAM.
If you want to be sure I see email from you, then
please include the words "Ryk says it's OK" somewhere
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Ryk wrote:


You need to check the page again. The recommendation is based on the
size of the *foretriangle*, not on the size of the headsail. My
*foretriangle* is just over 300 square feet and the Lewmar 46s are a
good match for the loads all the way from the blown out 150% down to
what some of my chums refer to as my "cocktail jib" (short hoist for
about 80% of the foretriangle area).

The foretriangle is what we are talking about. Acording to that formula
your 300 sq ft foretriangle needs a pair of 52s. My I = 58.8 and J =
17.25 so my foretriangle is about 507 sq ft. The formula comes up with
80+ which is obviously out of line.

I think the problem is the 6 factor. It is supposed to be a combination
of 30 knots of wind and all the friction load. It must have been chosen
by a winch salesman. :-)

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Holy Cow. By that formula, the boat I race on with the 660 square foot
foretriangle (and it's a 12 ton boat to boot with lots of stability and big
loads) has winches about half the required size. We race with old
Barient 52s, and while short tacking with the #1 requires us to swap
out grinders on occasion, I don't think a 110 power ratio is what the
boat wants. I'd say something in the 60's would be better than what
we've got (the Barients were the biggest thing going when the boat
was built).

Use the formula Evan gave you (assume full foretriangle at about 30
knots) and go from there. Use a 35 pound load on the winch handle.
That gives you a 56 which is probably in the ballpark.

"Glenn Ashmore" wrote in message
...


Ryk wrote:


You need to check the page again. The recommendation is based on the
size of the *foretriangle*, not on the size of the headsail. My
*foretriangle* is just over 300 square feet and the Lewmar 46s are a
good match for the loads all the way from the blown out 150% down to
what some of my chums refer to as my "cocktail jib" (short hoist for
about 80% of the foretriangle area).

The foretriangle is what we are talking about. Acording to that formula
your 300 sq ft foretriangle needs a pair of 52s. My I = 58.8 and J =
17.25 so my foretriangle is about 507 sq ft. The formula comes up with
80+ which is obviously out of line.

I think the problem is the 6 factor. It is supposed to be a combination
of 30 knots of wind and all the friction load. It must have been chosen
by a winch salesman. :-)

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com