[BOAT] What's special about sail winches?
Wallace Crawford White
sailboat for a Mechanical Engineering class. I'm planning to use my Futaba
4-channel radio gear. In fact, I've just about installed the stuff,
cinluding some S48 servos for the rudder and sails.
I'm planning to just connect a long equal-ended arm on the sail servo and
connect the sheets to each end of it. I keep hearing about "sail winch"
servos, and I'm also afraid to ask what the difference is. I ought to be
able to get by with a normal servo, right, on this small a model? I'd like
to avoid buying another servo if at all possible.
Thanks,
Wallace White
Dave Mainwaring (Northeast Resources)
IMHO the term sail winch simply indicates the servo you choose is stong and
fast enough to be used for controlling the model's sails. Any servo can be a
sail winch if it is strong enough. sail winch servos are a variation of the
landing gear servo. When they get designated "sail winch" it means that they
have a common application and usually they have been beefed up for a
particular application. The sails on a model are generally controlled by a
line from some attachment point on the boom to a winch. When the sails are
full of wind and the skipper manuevers the model so that the sail suddenly
cchanges sides the sheet yanks the winch. I have seen postings about the
loose gears onm some of the sail winches, Tyoically this is due to the
sheets yanking the gears so hard that they break free of their shafts. After WWII the most
common sail winch was a converted servo gear motor from surplus military
ddrones because they were the only gear motor around that would not fall
apart. The first R/C sailing models were big, it wasn't until the 1970's
that the small transitorized sets became common.
Your small model probably won't sail in very high winds and it is OK to try
out a regular servo as a sail winch..it won't cost you your amatuer
status:-) If you find the servo is stalling out while it pull in the sails
or it is breaking down then try a bigger servo.. If you were building a
model such as a Star 45 or an EC-12 you you would find yourself needing a
lot of electric power since the sail winches do work hard and often. The you
get into the servos and sail winches that have a isolated battery pack. My
sail winches typically have four "D" cells or a jell cell and run anywhere
from six to 12 volts. On a big sail winch you have to design the size of the
sheets or the arm to break under tension because the big sail winches can
pull on tangled sheets so hard that they will break up a model before they
stall.
Good luck with your model...worry more about keeping it watertight than
about the sail winch. The model should be able to tip flat on its side in the
water and not let water in. :-)
--
Dave Mainwaring
Northeast Resources
(617) 455 9920 FAX 617 449 1826
Steve Andre
force available at the tangent to the radius of the drum is greater than
the force available at the end of an arm.
First, figure out the sail area of the model.
Second, every 3 sq ins needs one ounce of force.
Third, figure the force available from the servo for the length of arm
required. Divide the torque of the servo (in oz.in) by the length of the
arm.
Fourth, use a double purchase on the arm---belay the end of the sheet on
the hull and run the sheet through the end of the arm and then to the
boom---this doubles the length of sheet that can moved while keeping the
arm short and the available force doubled.
Conclusion: standard servos still won't move diddly if there's any wind at all.
OR:
Convert your servo to a drum winch by replacing the 270 degree (5K) pot
with a ten turn precision potentiometer. A good 1/4 scale servo with 165
oz.in of torque can be converted to a drum winch, with a 0.75 in radius
and 220 oz of force, that cranks in 10 inches of sheet in 2.50 seconds
with a load of 750 sq in of sail in 5 mph winds.
Even a std servo converted to a drum winch will provide 3X the force of a
std servo with an arm (about 55-60 ounces of force---which means you can
move only 150 to 180 sq in of sail in a moderate breeze)
Get back to me if you need more info, or dust off that Newtonian mechanics
textbook.
Steve
Markus Imhof
(Wallace Crawford White) wrote:
:-)As you may have read from my other recent posts, I'm making a 22" RC
:-)sailboat for a Mechanical Engineering class. I'm planning to use my Futaba
:-)4-channel radio gear. In fact, I've just about installed the stuff,
:-)cinluding some S48 servos for the rudder and sails.
:-)
:-)I'm planning to just connect a long equal-ended arm on the sail servo and
:-)connect the sheets to each end of it. I keep hearing about "sail winch"
:-)servos, and I'm also afraid to ask what the difference is. I ought to be
:-)able to get by with a normal servo, right, on this small a model? I'd like
:-)to avoid buying another servo if at all possible.
:-)
:-)Thanks,
:-)Wallace White
Well, from what I've seen so far (I don't race sailboats - I just have one
for fun) the main differences are space, speed and power.
space: with the servo, you need the space under deck to swing the arms
around. With the winch, you just need the space for running the lines. I
cna't explain better in text, but essentially I have a stick with the
winch on one end, some rollers on the other end and one endless line
running from the winch to the rollers and back. The sail's lines are
attached to that endless line. So the space required is essentially 15"
long and 2" wide.
speed: a servo will give you full throw in well under one second, my winch
needs someting like 3 seconds for full throw
power: the inverse goes for the power. The pulling power of the winch is
(at the same throw) much higher than the power from the end of the servo
arm.
So, to answer your question: Yes, you can use a servo, if you can find the
space for the movement of the arms. The power requirements depend on the
wind you'll have when sailing.
Bye
Markus
Dave Mainwaring (Northeast Resources)
How did you come up with the "every 3 sq ins needs one ounce of force." ?
--
Adam Skwersky
I have one for each sheet (two for the jib and one for the main). These
servos are speed controlled rather than position controlled. That means
if you move the transmitter stick slightly, the servo will start taking in
or giving out sheet, and continue to do so until you center the stick
again. I think the advantages over the arm winch are that you can just
about control any length of sheet, whereas the arm winch has a certain
range of sheet length that it can control (because length of its arm is
fixed). Also, the winch for each sheet allows me more control over each
sheet. If you tie both the main the jib to a single arm winch servo then
you cant control each sail remotely and independently.
Adam Skwersky
In article <3qiq24$5...@nntp.Stanford.EDU>, whi...@apollo0.Stanford.EDU
(Wallace Crawford White) wrote:
> As you may have read from my other recent posts, I'm making a 22" RC
> sailboat for a Mechanical Engineering class. I'm planning to use my Futaba
> 4-channel radio gear. In fact, I've just about installed the stuff,
> cinluding some S48 servos for the rudder and sails.
>
> I'm planning to just connect a long equal-ended arm on the sail servo and
> connect the sheets to each end of it. I keep hearing about "sail winch"
> servos, and I'm also afraid to ask what the difference is. I ought to be
> able to get by with a normal servo, right, on this small a model? I'd like
> to avoid buying another servo if at all possible.
>
> Thanks,
> Wallace White
--
Adam Skwersky
Graduate Student Department of Mechanical Engineering, MIT
askw...@mit.edu
Steve Andre
main...@k12.ucs.umass.edu (Dave Mainwaring (Northeast Resources)) wrote:
> How did you come up with the "every 3 sq ins needs one ounce of force." ?
I made mechanical winches for years, then switched to Whirlwinds when
boats started to get lighter and narrower. After being DNF and DNS in two
heats during the nationals and losing a trophy position due to winch
failure, I vowed to make a digitally proportional sail winch of my own
from readily available materials.
I bench tested existing models of servos and winches from major
manufacturers and cottage industries (including my own version of a
modified quarter scale servo) over a three month period using a scope
emulating AD computer, a reduced friction table, and calibrated weighted
sleds. Data was accumulated on speed, torque, force, current draw in both
loaded and unloaded modes. This was done to determine the validity of
claims made by manufacturers in their pamphlets and to establish a common
denominator for comparison of different models. The servos and winches
were also tested for lifting capability of 5.5, 9.5, and 16 pounds.
The servos and winches were then field tested in a US One Meter and a
50/800 in wind conditions that varied from 1 to over 30 MPH. Under the
most severe of wind conditions, I was uncomfortable sailing with any servo
or winch that provided under 1 ounce of force for every 3.0 sq in of sail
area. Some servos broke gears (plastic), burned up FET's on their boards,
stalled, or just couldn't hold the sails under wind pressure. With
greater one ounce of force per 3.0 sq in, I felt safe running a boat in
conditions that had the boats buried off the wind and heeled 50 degrees
or more going to weather.
I was one of three model yachters consulted by Futaba upon the design
of their "new" sail winch to replace the old S-10/110. What came back
from Japan was a sail servo....again! All or parts of the data
accumulated from my tests and a couple of the winches were provided to two
of the manufacturers.. let's do some reverse engineering. Others were not
interested in the comparisons... let's all bury our heads in the sand!
My own design with 165 oz in of torque (225 ounces of force at the
tangent to radius of the drum) is still running after 5 hours per week for
4 years (52 weeks a year) in salt water. It may weigh almost 4 ounces,
but I trust it more than other servos or winches that I've owned or tried.
Enough said,
Steve Andre
Dave Mainwaring (Northeast Resources)
>boats started to get lighter and narrower. After being DNF and DNS in two
>heats during the nationals and losing a trophy position due to winch
>failure, I vowed to make a digitally proportional sail winch of my own
>from readily available materials.
What did you finally come up with?
>
> I bench tested existing models of servos and winches from major
>manufacturers and cottage industries (including my own version of a
>modified quarter scale servo) over a three month period using a scope
>emulating AD computer, a reduced friction table, and calibrated weighted
>sleds. Data was accumulated on speed, torque, force, current draw in both
>loaded and unloaded modes. This was done to determine the validity of
>claims made by manufacturers in their pamphlets and to establish a common
>denominator for comparison of different models. The servos and winches
>were also tested for lifting capability of 5.5, 9.5, and 16 pounds.
Solid stuff! Did you also do any sort of drop test or shock test to see how
the servo-gear trains stood up to constant battering?
> The servos and winches were then field tested in a US One Meter and a
>50/800 in wind conditions that varied from 1 to over 30 MPH. Under the
>most severe of wind conditions, I was uncomfortable sailing with any servo
>or winch that provided under 1 ounce of force for every 3.0 sq in of sail
>area. Some servos broke gears (plastic), burned up FET's on their boards,
>stalled, or just couldn't hold the sails under wind pressure. With
>greater one ounce of force per 3.0 sq in, I felt safe running a boat in
>conditions that had the boats buried off the wind and heeled 50 degrees
>or more going to weather.
>
I like your rule of thumb 3 oz per sq inch, do you think it will hold for
the big models? 2000+ sq in sail area.
I don't really care if the winch is digital or proportional, but i do care
if the winch breaks up because it can't stand the beating or if the sails
are constantly draging the line back out when the servo is "off".
>accumulated from my tests and a couple of the winches were provided to two
>of the manufacturers.. let's do some reverse engineering. Others were not
>interested in the comparisons... let's all bury our heads in the sand!
You like that nont-invented-here syndrome, no :-(
Was you work limitted to drum type winches?
>
> My own design with 165 oz in of torque (225 ounces of force at the
>tangent to radius of the drum) is still running after 5 hours per week for
>4 years (52 weeks a year) in salt water. It may weigh almost 4 ounces,
>but I trust it more than other servos or winches that I've owned or tried.
>
The proof is in the pudding :-).
I have been out of the AYMA circle for several years, so I admit to being a
bit obsolete. What are the current sources of sail winches that meet or
excede you criteria?
How abour some instructions on how best to set up drum winches?
To bad there aren't more skippers on the Net. The boat people have had to
rely on the fliers to fight the FCC and to accept so much of the radio
equipment design. what is the current population of the AMYA, did they ever
break the 3000 member mark?
Kerry David
I am currently using a TONY ABLE drum winch in my new 36/600
racing yacht (36 in. hull/600 sq. in of sail area). This winch has a 1"
diameter drum and produces 140 oz./in. of torque according to the specs.
I have sailed it in winds up to 18 kts. with no loss of sheeting control
due to wind pressure. After sailing a Futaba S-125 "swing arm" in my first
racing, boat I have now become a convert to drum winches. There are however
some
other important considerations when deciding on a winch. First, drum
winches work best on a flush deck yacht. If, because of the deck layout
(raised hatch, cabin structure, etc.) you have to use through-deck fairleads
for
your sheeting exits (exit guides) on the jib and main sheets, then a
swing arm is much easier to rig below deck. However, in order to
generate the same "sheeting power", swing arm winches will be heavier,
and probably require a bigger battery pack, thereby increasing the weight
of the vessel. On the other hand, drum winches seem to require more power
when in "transit" because of the greater number of servo motor
revolutions required to operate the drum winch. Also, I like the greater
flexibility in
rigging the drum winch. All in all, for racing, I have now become a drum
winch "convert".
Steve Andre
main...@k12.ucs.umass.edu (Dave Mainwaring (Northeast Resources)) wrote:
> In a previous article, ste...@jeeves.ucsd.edu (Steve Andre) says:
I vowed to make a digitally proportional sail winch of my own
> >from readily available materials.
>
> What did you finally come up with?
I took a HiTec 700 1/4 scale servo, replaced the potentiometer with a
Bournes 10 turn precision wirewound pot (5/8" sq, 20K, small shaft). The
pot, middle section of the servo case, and the final drive gear were all
slightly modified.
The drum was a two section, circular alum heat sink from a surplus store
that was just the right size to fit the largest round horn. Once
production began, the drum was turned from solid delrin with the horn
inserted in the center, quite nice
I also modified the 705, metal gears and higher torque.
HiTec is making a sail winch (the 725) that has the torque of the 705, a
molded drum, but plastic gears for about $65.
I have the two prototypes of the 735 and 745 with more powerful and faster
motors for indefinite "testing".
They also will sell a 300 oz.in servo for the big gas cars that can
modified into a drum winch.
The servos and winches
> >were also tested for lifting capability of 5.5, 9.5, and 16 pounds.
>
> Solid stuff! Did you also do any sort of drop test or shock test to see how
> the servo-gear trains stood up to constant battering?
The lift test was really a lift and release test. Metal and plastic gears
all survived. An older Whirlwind Olympic had a phenolic gear fail.
> I like your rule of thumb 3 oz per sq inch, do you think it will hold for
> the big models? 2000+ sq in sail area.
> I don't really care if the winch is digital or proportional, but i do care
> if the winch breaks up because it can't stand the beating or if the sails
> are constantly draging the line back out when the servo is "off".
As far as the force per sail area "rule", it holds for all sail sizes.
However, the larger sail plans, the components better be stouter, since
the total force exerted is greater. The AC Class, 1" per 1', has around
2,000 sq in, but the winches used are usually ones used in the Santa
Barbara class (smaller sail area). They include mechanical arms
(Dumas-style, Probar, ORCO), proportional arms (Probar, Seiko), and drums
(Andrews)
What are the current sources of sail winches that meet or
> excede you criteria?
For one meter's, I prefer my own, of course. For S/B and A/C, I like the
Seiko (it's expensive) proportional and the John Andreson mechanical
version of the old Orco (it's around $100). I trust only the prototype
745 f or s for the 50/800. Whirlwind will have to go a long way to earn
my respect, again.
> How about some instructions on how best to set up drum winches?
Send me your mailing address via e-mail (direct not through the newsgroup)
and I will supply instruction sheets that I send out with winches--labeled
diagrams included.
what is the current population of the AMYA, did they ever
> break the 3000 member mark?
Not even 2000 yet. There's an AMYA R/C sail group on Prodigy, since
that's where the directors have connects. A few of us were on the net,
but we lost out when no one else wanted to switch to the net.
Steve
Steve Andre
>
> Not even 2000 yet. There's an AMYA R/C sail group on Prodigy, since
> that's where the directors have connects. A few of us were on the net,
> but we lost out when no one else wanted to switch to the net.
>
> Steve
My mistake, the AMYA is on Compuserve.
Steve
Dave Mainwaring (Northeast Resources)
In a previous article, ste...@jeeves.ucsd.edu (Steve Andre) says:
>
>>
>> Not even 2000 yet. There's an AMYA R/C sail group on Prodigy, since
Back when I was real active along with Manny Costa, Jack sullivan and all
the "old timers" as I recall jack and I came up with a list of 1000 modelers
sailing in the six New England states, granted many were not into AMYA.
Perhaps because some of us got tired of the yelling and screaming
by the so called serious racers. what got to me was the skippers who showed
up with their magnetic models and metal board to lay out their protests.
Guess that why I like classic gaff rigged models and Star 45's, they're to slow to get
up tight about :-)
>> that's where the directors have connects. A few of us were on the net,
>> but we lost out when no one else wanted to switch to the net.
>>
>> Steve
>
>My mistake, the AMYA is on Compuserve.
>
>Steve
>
--
Warspite2
model (Bugeye - 77" overall - three sails)? I have been checking on
geared motors prices - seems to me that a geared motor, machined color and
a couple of micro switches is the most reasonable way to go. But there is
always theproblem of how much power do I really need. I have an "Os???"
from 12 meter racing in it now and it handles the sails on lighter wind
days but seems to bog down even then.
I like arm type because you can control several sails with different
demands of the amount of line fed out easily.
Marty Hayes
Dave Mainwaring (Northeast Resources)
IMHO its not how much power you need but finding the inexpensive light
weight gear motors. I have a couple of sail winches that have Brevel model D
gear motors with 12-36 volt ratings. They can crunch up a model if they get
tangled<grin>. The micro switch control is a challange since not only do you
want he winch to stop between limits but when it does reach its limit you
want to be able to reverse its direction and get it to run again.
Bugeye, now that must be an interesting model. 77 overall and weighs how
much?
--
Dave Mainwaring
Northeast Resources
EMAIL ADDRESS Nresources @aol.com phone(617) 455 9920 FAX 617 449 1826
Adam Skwersky
I saw you posting about R/C sailboats on netnews and wondered if you knew
any good places around Boston to sail my boat? Preferably where others are
also doing R/C boating? I live on the MIT campus, and was thinking of
bringing my boat to the Esplanade and sailing it in one of the lagoons but
was afraid it might get stuck somewhere and I'd have to brave the waters
to retrieve it!
Thanks,
Adam
Warspite2
reversal for the end of travel of the winch is easily accomplished by use
of diodes ala Dumas sail control. I got cheap motors (555's) surplus but
still don't know if on 1000:1 ratio will be enough for bugeye's three
sails.
Marty Hayes
Dave Mainwaring (Northeast Resources)
In a previous article, wars...@aol.com (Warspite2) says:
Care to explain about the "diodes ala Dumas"? I haven't seen a Dumas around
here ( I have been very inactive in the sailing arena, been building model
fishing boat and tug). How do they use diodes to reverse the travel when the
winch is not at the end of its travel?
Warspite2
stop the motor at the end of travel but allow the reverse power to turn
the motor in the opposite direction. As always reversing the voltage to
the motor leads reverses the motor direction at any location of travel.
The diodes are place across the switches NO and NC leads (power lead to
the NC contact and the power is allowed to travel to the NO leads when
polarity of that direction will move the motor in the correct direction.
At any midpoint of travel the power comes through the NC leads and
contacts (not through the diode) allowing normal operation.
Hope this is clear enough - I really write better with diagrams.
Marty Hayes