Design Details for R/C Square Rigger Operating Systems - Page 6 - RC Groups
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Jan 24, 2010, 06:39 PM
meatbomber's Avatar
Dan Thanks for teh great drawing one question, is there an elastic or something that keeps the lines under tension before runing onto the winch drum ? Or is the sheet tight against the stay ?
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Jan 24, 2010, 08:28 PM
Registered User
DanL's Avatar

Crossover jib tension

The sheets, attached to the clew of a headsail, work as a pair - one moves forward as the other one moves back. The length is adjusted so they are just a little bit tight. As they move, not much slack develops, even with no wind in the sails. With any wind at all, the sheets are taught.
So to keep the sheets on the drum, no elastic is necessary. The flanges of the drum are big enough to keep he lines in place.
Jan 25, 2010, 12:25 AM
Damp and Dizzy member
Brooks's Avatar
John Dowd, of RC Bluenose fame in UK, says if the box around the drum is closefitting enough, even loose line will not jump the drum, nor tangle.

The text and diagrams of his RC winches (post #20 for the winchbox)
Last edited by Brooks; Jan 25, 2010 at 12:38 AM.
Jan 25, 2010, 11:14 AM
Paratrooper's Avatar
I checked the clearances in the hull of my frigate to see if I could install the cross over headsails with the servo in the well. It will be a very close fit to put the servo and winch drum down low because the keel tube is actually 4 or so inches behind the mast. When I installed my head sail winch I think I found it to be too tight a fit and I mounted mine on the main deck in a well ahead of the keel tube assembly. All this was done before the forecastle deck was installed and I had the system tested before covering it up.

The cassette assembly will work fine but if it is installed in the well it may have to be ahead of the mast because another cassette assembly must be installed on the aft side of the fore mast to rotate the main mast yards.

One thing for sure is that there is NO clearance between the two decks to rig anything after the decks are installed. I cannot get my hand between the forecastle and the main deck. All the rigging must be done before the main deck is installed for anything going in the mechanical well.

Also to be sure that my common sheets cannot come off the winch drum, I have a pully and block installed on my bowsprit to tension the two common sheets and I have the sail sheets tied to the common sheets behind that pully block.

I went out and took a few photos to try to relate what my build ended up being because of clearances.

P.S. If the winch drum and servo could be installed way down low with a smaller drum on it, Dan's general layout idea might work. The cassette and servo would have to be installed under the forward main mast servo but there might be enough room to do it. I did not think that a large drum would fit but a smaller one would as long as the common sheet lines stay taught all the time and with a block and pully on the bowsprit it would.
Last edited by Paratrooper; Jan 25, 2010 at 12:49 PM. Reason: UPDATE
Jan 25, 2010, 12:47 PM
Registered User
Not exactly sure how the sheet servo ( control arm) is rigged. Would it be possible to install the cross over servo winch where the sheet servo goes. Then install the sheet servo aft of the Main and Mizzen Brace servo on a lower plane VIA a different mounting block set up? Looks to me like you could still get to that servo for maintenance.
Jan 25, 2010, 04:17 PM
Registered User
DanL's Avatar

More detail on crossover jib rigging

The crossover headsail servo fits in front of and slightly lower than the forward squaresail servo. It is behind the keel rod tube.
The pulley cartridges are shown in the pics. The upper cartridge is a delrin body with pulleys in slots, as shown in previous posts. The lower cartridge, for the headsails, was made with brass stripstock soldered into shape - just an experiment. The solid one-piece plastic body cartridge is definitely easier to make.
Both cartridges are simply screwed to the face of the mast. They fit halfway around the mast, and that, with the screw, make them very stable in position.
I rig the cartridges where I can easily thread them and then screw them in place.

One pic shows the attachment hardware for the headsail sheets. I used both a brass ring and a brass jewelry snap to provide at least two weak points for breakage in case any sheets get snagged. Never have had a snag or a break, yet...

I really like Ray's common sheet traveller approach for attaching the sheets.
It keeps the common sheet tight and out of trouble, and provids a more inboard connection point as the shets are let out. I think I'm going to modify Syren to that design.

looking at all my drums again, the CD's are holding up well. I think I'll go with the drums as-is for next season. Have a lot of guns to prepare anyway....
Jan 25, 2010, 04:32 PM
Registered User
DanL's Avatar

Surprise jib servo placement

I would move the forward squaresail servo back just a bit and would put the jib (headsail) servo right in front of the forward squaresail servo, rather than between the two holes I see in the base piece. See the Syren pictures. That way you have easier access.
Could you show a pic of the whole servo and mast base and ID the holes (masts, keel tubes, etc)?

If you make cartridges for your pulleys, use two screws in the face of the cartridge rather than one. Not for strength, but for ability to drive the screws cleanly. One screw in the center is hard to drive because it's in alignment with the keel rod tube, servo, etc.behind it. Two screws can each be driven from a slight angle from each side. Look at the top cartridge in the Syren pics - it has two screws (you only see one) slightly offset to angle to the side to make them easy to screw in place.

You might want a simple arm servo (180 degrees) in the center for the driver. Save the drum servo as a backup.
Last edited by DanL; Jan 25, 2010 at 04:38 PM.
Jan 25, 2010, 04:37 PM
Registered User
Dan That might be possible. Depending on Flange diameter of the Jib servo. If the flange is the size of a CD then I am 3/4 of the way into the keel rod tube.
Jan 25, 2010, 04:42 PM
Registered User
DanL's Avatar
Trev - the jib servo flanges can be smaller than a CD diameter. The sheets don't see much slack.
What are those discs in the pics made of? Look like styrene. That would be good.
See you PM's.
Jan 25, 2010, 06:08 PM
Paratrooper's Avatar
Trevor: Dan is spot on with his engineering here. I do not think he had that invented when I was doing mine. I have been doing my rigging after Dan figures some of this stuff out and I have been pinching his engineering. I think my tops and courses would have even been better had I rigged mine similar to what he has done but I am satisfied with the way my ship sails. If you rig your head sails with the block and pully on the sprit you can use a smaller diameter winch drum because the common sheets will stay tight.
Jan 26, 2010, 01:11 PM
SCALE Sailor
JerryTodd's Avatar

Jib control

This just popped into my head, rattled about, and fell out here...

The arm pivots on the 'X' servo horn with stops to allow it to only pivot so far. I haven't tried this mechanically as yet, but the idea was to slack the sheet a little when coming about so the head sail would travel easier with loose sheets. Maybe it wouldn't require constant tension as Dan's set up requires?
Paratrooper uses a running loop that the sheets attach to - the loop keeps the tension, the sheets don't require it.

I show the sheets doubled below to increase the arms pull, but none of the drawing is measured or to scale.

Someone wanna see if this would do what I think it will?
Last edited by JerryTodd; Jan 26, 2010 at 02:49 PM.
Jan 26, 2010, 01:43 PM
meatbomber's Avatar
jerry i`m wondering why not just make along servo arm and use teh same geometry as on a square sail yard brace.So actually when you need the most pull, at the time you pull the cleat across the stay the sheet is the tightest, when sheeted fully to port or stbd the sheets go slacker like usually our braces do too due to the geometry of the servo arm / fairleads, that would keep the sheet from getting very tight but then too tight headsail sheets make them act as airbrakes and wind vanes rather than sails anways
Jan 26, 2010, 02:43 PM
SCALE Sailor
JerryTodd's Avatar
On a real boat, typically, when the "helm's-a-lee!" the jibs sheets are cast off. As the boat rounds into the wind the jibs luff their way across the stay. The old sheets are stood-by in case the jibs need to be back winded to their old position to help the head through the eye of the wind, otherwise they are sheeted home on the new tack just before the foremast squares are brought around.

There are several ideas for doing this with multiple servos - I'm interested in doing this with one servo. I think, the rocker-arm will put slack in sheets when the sheet is eased, allowing the jibs to luff a bit and more easily get over the stay, which a constant tension system does not allow.

Dragging the sheets and clew over the stay in a constant tension set-up creates chafing, which will lead to fraying, which could wind up causing snags, which will over-work the servo, which could snap a stay, sheet, a spar, or have some other catastrophic, or near catastrophic effect. Some sort of anti-chafe set-up helps, a roller on the stay perhaps, but any solution will likely be non-scale and something of an eyesore.
Jan 26, 2010, 03:17 PM
Registered User
DanL's Avatar

Crossover jibs

A rough check of arm geometry as it rotates indicates that tension is actually highest when the arm is at 90deg. I'm nt sure that's true with Jerry's second pivot point concept - looks very interesting.
Anyway, with teh system I showed (the one on Syren), the sheet tension is not very high at all when the headsail clews are exactly centered on their interfering stays.
It's at that setting that the sheet length adustments are made.
The sails tighten as they are sheeted to either side, but the sheet pressure on the crossed stays increases much more from wind pressure than from the sheet geometry effect. Even with wind, the sail clews don't tighten on the interfering stays as they cross - the system is pretty loose at that point. The only "event" that occurs is a slight bump as the clew-to-sheet knot crosses the stay. If the right knot is used to provide a smooth profile, the crossover is pretty smooth.
I've used the system now for three seasons and many hours of sailing and there is no sign of any wear on lines. (I did replace the braided lines last year with twisted line for better scale appearance, but I don't see wear being an issue)
Jerry - I'll rig your setup on the floor - I use balsa strips and pins to lay it out on the carpet and make the mesuements as I move the arms thru their ranges.
Ray's system also allows maximum center tension adjstment. It also has the advantage of keeping the clews a bit more inboard over a wider range of sheeting.
Jan 26, 2010, 04:48 PM
Paratrooper's Avatar
The reason I put the pully and block in was because several times I found that the common sheet on the loose side would tangle in other rigging making the next tack impossible. I also had the common sheet slip out of the winch drum which required the removal of the grating and re-rigging the line to the drum. Neither problem has reared its ugly head since I put the pully and block system in and Dan is right, the clews stay inboard over the whole range of sheeting.

Regarding the arm approach with attempting to rotate the yards. I found that even with the driver sail on an arm, I had to double back inside the hull to gain and hold the driver in a stiff breeze. I also have it doubled at the stern to act as a block and tackle and I have not had a single incident of blown fuses or the driver not holding in some of the seas I have sailed on. The arm works fine but it must have sufficient servo power to hold and my original installation did not. With the doubling both in the hull and at the stern I gain the advantage of a double block and sheave advantage which doubles the power of the servo without changing to a more powerful type.
Last edited by Paratrooper; Jan 26, 2010 at 04:54 PM. Reason: Add a comment

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