Sail winch calculation

[Paul Davenport]

Greetings from the UK,

I have a 3 metre long mother of a schooner, including all sails. Is there
any way to calculate the sail winch torque needed from the square meterage
of the sail area. I ask this because most manufacturers will lie about their
winches ability to haul what is a vast area in and out!

So far RMG in Australia look to be the best bet but they will not guarantee
their 380 series is grunty enough!

Ta for any response...as always a virtual beer for the first correct answer!

Paul Davenport

[Trevor George]

Paul Davenport wrote in message ...
> I have a 3 metre long mother of a schooner, including all sails. Is there
> any way to calculate the sail winch torque needed.

Mike's yer man at http://www.WaverleyModels.co.uk in Clevedon, Somerset.

He's very helpful and specialises in that sort of thing.

Cheers ..... Trevor George, Bristol, UK. http://www.OnMyWindow.co.uk

[A.T.]

Whirlwind have a selection chart.
http://www.whirlwindwinches.co.uk/winches.html#choices
However as all boats will vary according to the type of blocks and pulley
systems used and conditions under which model will be sailed, most charts
are way out.
refer to http://homepages.ihug.co.nz/~atong/ and scroll down to "Reviews,
Plans, FAQ & Tips"
under "Boats, Yachts, Submarines, Warship Combat and Nautical reviews" for
good information e.g. http://www.amya.org/us1mpt4.pdf

You may wish to consider the Hitec HS805BB
http://www.hitecrcd.com/product_fs.htm which has tremendous power,
especially on 6V. NB: People frequently forget that many servos last longer
on 4.8V as they want the power of 6V so run a 5 cell pack. Straight off a
fast/field charger 5 NiCad cells can hold 7.7V and some 8.1V which will
sooner or later blow the board on a servo rated as 4.8 - 6V unless that
float charge has been allowed a few minutes rest to dissipate the float
before use. This especially applies to the Futaba winch servo which
recommends a 7.2V pack but has had frequently blown expensive boards when 6
NiCads are used - runs well on 5 NiCad an no blown boards.
regards
Alan T.
Alan's Hobby Web Links
http://homepages.ihug.co.nz/~atong/
.................................................. .............

"Paul Davenport" <Davers00@btinternet.com> wrote in message
news:bbg0lb$9i3$1@titan.btinternet.com...
> Greetings from the UK,
>
> I have a 3 metre long mother of a schooner, including all sails. Is there
> any way to calculate the sail winch torque needed from the square meterage
> of the sail area. I ask this because most manufacturers will lie about
their
> winches ability to haul what is a vast area in and out!
>
> So far RMG in Australia look to be the best bet but they will not
guarantee
> their 380 series is grunty enough!
>
> Ta for any response...as always a virtual beer for the first correct
answer!
>
> Paul Davenport
>
>

[Fly Higher]

For what it's worth, I just picked up a pair of RMG 280 winches. Very nice
units! Well made and a decent price. I'll be using them in a "sorta scale"
boat about the size of an EC-12 (60 inches or about 1.5 metre and 2000
square inches of sail). I suspect I could get away with one winch but, I'm
going with two.

Sail area is a consideration as well as how many sails but I think their
shape would play into it as well. Is a tall, skinny sail easier to handle
over a short wider sail of the same area? I would think a schooner would
lean towards the latter.

One place you might check though is the J Boats. Try:
http://www.cs.unr.edu/~arnold/jclass/ (You'll have to copy and paste the
link into your browser for it to work) In case you don't know, these boats
are 100 plus inches long and are modeled after the America's Cup boats of
the 1930's. They carry 4000 plus square inches of sail, have masts as tall
as 116 inches (or more) and weight upwards of 100 pounds. I'm sure what
they use for winches would work on your schooner.

F.H.


"Paul Davenport" <Davers00@btinternet.com> wrote in message
news:bbg0lb$9i3$1@titan.btinternet.com...
> Greetings from the UK,
>
> I have a 3 metre long mother of a schooner, including all sails. Is there
> any way to calculate the sail winch torque needed from the square meterage
> of the sail area. I ask this because most manufacturers will lie about
their
> winches ability to haul what is a vast area in and out!
>
> So far RMG in Australia look to be the best bet but they will not
guarantee
> their 380 series is grunty enough!
>
> Ta for any response...as always a virtual beer for the first correct
answer!
>
> Paul Davenport
>
>

[Bernd Mludek]

Hello Dave

You won't find a more powerful proportional sail winch anywhere than
the Dumas 3703. It'll lift a 16 pound bowling ball off the floor at
the end of a 12 inch arm.
I use an older non-proportional (bang-bang) model in my Santa Barbara
yacht, which is a 27 pounder 72" long and about 1200 sq." of sail (I
don't remember exactly) but it is a One-design.
Check out the following website for more info.
Good luch on your schooner.
http://www.dumasproducts.com/cgi-bin/dumas.storefront/3edea56802fa7d26271d40d40968069f/Product/View/3703

Bernd


On Mon, 2 Jun 2003 17:14:19 +0000 (UTC), "Paul Davenport"
<Davers00@btinternet.com> wrote:

>Greetings from the UK,
>
>I have a 3 metre long mother of a schooner, including all sails. Is there
>any way to calculate the sail winch torque needed from the square meterage
>of the sail area. I ask this because most manufacturers will lie about their
>winches ability to haul what is a vast area in and out!
>
>So far RMG in Australia look to be the best bet but they will not guarantee
>their 380 series is grunty enough!
>
>Ta for any response...as always a virtual beer for the first correct answer!
>
>Paul Davenport
>