Hello Roy,

Thank you very much for the extensive information. I never new there was so much to learn. Perhaps I should have stuck to fishing! 😁

Greg 👍

Hi all, servo winches, the rotating kind, have their place. They do need an end pulley to allow for the travel available for the sheets. They can also supply a greater pulling power and the strain on the servo mechanism is also greatly reduced. The winch cord will wind around the winch and it is the winding in against the wind which is the only 'side' to use.

The return cord can be part elastic to keep the tension up or just cord with a spring pull for the end pulley. When making up these units have the pulling cord on the lower part of the winch pulley and the return on the top part. Why? Well if using elastic which is not as durable it is easier to replace it on the top winch and lkewise if you are allowing for some stretching it is easier to loop another turn on the top pulley portion.

To make the unit easier to maintain consider having the end pulley on a length of dowel so the whole unit can be assembled and easliy removed for maintenance. I use knotted loops in the cord for attaching the sheets. The winch servos can be standard size servos and there are more powerful but larger ones available.

There is another version of the rotating winch where the winch cord is contained in the sealed winch pulley. These have 2 separate pulley sections and 2 opposite exit holes for the cord. I find that a light tension can be applied by using a couple of cms of solder wire looped around the sheet which gives some pull to the cord coming out of the sealed winch.

I have one in use now and after some experimentation I route the main boom cord through a tube but the jib cord I leave hanging. On a first installation of one of these winches I had trouble with the jib boom cord and then realised I was trying to push string up a tube! To save uneven winding on the drum it is best not to adjust the sails when there is no wind.

Several yachts have a small fore sail and they do not require much energy to pull in and their movement is not quite the same as for the boom. I have a yacht with a small fore sail and I run it with a yoke of cord through an eyelet in the clew of the sail. This sail may overlap the jib and this works reasonably well. The 'fixed' end can be adjusted at the pond side for varying wind speeds. The other end goes into the deck or cabin and is terminated on a 8cm arm on a standard servo.

When tacking the servo arm is fully out allowing maximum length to the yoke to let the fore sail pass across the jib. When running into wind the arm is pulled in and this enables this small sail to focus the wind across the jib and you can see the boat pick up speed, it is quite remarkable and well worth the using the 3rd channel. You can see this yacht in my harbour and the above is fitted to the modified Bella Yacht called Pelican, with the gaff sail rig.

Regards
Roy

Hi, the main difference with the arm sail servos and a standard servo is the angle turned through. The sail winch arm servo goes through about 180 degrees and the standard servo just 90 degrees.
However if you measure the distance the sheet travels it is very small for the last 20 degrees of the extreme movement. So 140 degrees has the most effect. There are two options, the easy one is to use a small pulley with the sheet tethered to the inside somewhere and this doubles the movement of the sheet.

If you are happy with small electrical work put a very small 1K ohm resister on each side of the potentiometer in the servo and that will extend its movement to roughly 180 degrees, but you may have to experiment with resistor values.

There is an electronic way using a servo extender, they are very small and plug into the rx and the servo plugs into the extender. A servo morph, will have the facility to slow the movement down and save a too fast adjustment to the sails. The basic extenders vary a lot in price £10+ in the U.K. but the last purchase I made was for 4 of them for £10. via ebay and China.

Remember that the torque quoted for servos is given per cm so halves at 2 cm and at 3kgrms/ cm which is a standard servo an arm winch with a 12cm throw has only 0.25 kgms pull. If you go down this route with a standard plastic geared servo the gears will strip their teeth off at the first gust of wind.
This is why we use the metal geared 15Kgrm servos where there is still 1.25 kgrms available at 12cms.
The position of the sail servo arm winch is usually at the side of the hull giving the hull width for the arm. If you need more pull then a second similar servo could be connected via a Y connector lead to the receiver. The signal from the rx is all that is needed and splits easily with no loss, there is no current used at this point.

It is worth checking that when the sails are pulled in that the sheet lies across the centre of the servo rotation point this means that if there is a gust of wind pushing the sail boat over the pull is not through the gears but straight across the servo, which is a mechanical connection. The same applies to when the sails are fully out. This will determine the length of the extension arm.

The point of exit of the sheet from the hull is crucial, the sheet exit point should be directly under the attachment point to the sail boom otherwise the equal angle movement of the booms will be compromised.

It goes without saying that you should never angle a sheet through a metal eye the losses can halve the pull available. There were tiny pulleys available from Grapner but they may have gone now. However there is a neat and cheap solution.

At the point of exit from the hull use a hard plastic tube. I use a small length of solder wire slipped inside the tube to keep it open while I pour boiling water over it and bend it through a small arc. When you have it right, cool it in cold water and remove the solder wire and cut to length and you have a nice smooth low friction outlet.
Hope this helps, it was all gathered over several years of operation.
regards
Roy

We all use servos on our Wee Nips. Some very creative extension arms. A variety of 10, 15 and even 20k but 15 is the preferred.

My 1m Emma which has a jib and main is also specified with an arm servo rather than a winch, works well.

Hello Roy,

That's great. That will do me just fine. I'll go to Howes and see if they have stock.

Best regards,
Greg 👍

Hi, The Bella kit contains a wooden extension arm for the servo which I used. The advice is good, use a 15 kgrm servo £9.99 in Howes. This is the recommended method, just follow the script!
regards
Roy

Hello John,

Thank you for the sound advice. I see I have a lot to consider when I come to build the yachts that I have purchased.

Greg 👍

Hi Firefighter, my Bella has a servo it controls the sails very well and is more than adequate power wise.
I have the same setup in couple of my yachts.
stay safe, Jim.

Hi Greg,

Please don't forget my previous advice about using a heavy duty and metal-geared servo such as the widely available 996.

With some 17kg\cm of torque, these are around four times more powerful than standard servos and although quite a bit heavier, are exactly the same size.

In a smallish sailboat such as the Bella they are far easier to fit than a sail winch and at less cost to boot!

With best wishes. Dr John F Leeds & Bradford BBC. 😊😊😊

Hello Roger, Thank you for the advice

Greg 👍