Making a mainsheet traveller track curve to fit cockpit.

[fredrussell]

I have a Barton mainsheet traveller to fit. I would like to fit it on bridge deck which is (along with adjoining cockpit seats) curved. The curve is gradual, the centre of the 1.4 metre track being 50mm higher than the ends. The track (which is manufactured straight) will curve without vast amounts of pressure being applied to it, and the car runs along the curved track happily. I'm aware that its not ideal, in that as the car moves outboard it will also be moving down away from the boom, but I'm wondering if anyone on here has a curved mainsheet track of this fashion and if it has been a problem at all. The car is a recirculating ball bearing job and my concern is that if track is curved like this only some of the ball bearings will be in contact with the track and doing their job.

Just to head some of you off at the pass, so to speak, I'm aware of the pitfalls of mounting a traveller there (lost crews fingers etc), but thats where its going - so if we could avoid a discussion on that I'd appreciate it.

 

[Boathook]

Could always make some wedges for either side to keep the track flat. Years ago some of the track manufactures gave figures for how much the track could be curved.

 

[fredrussell]

Thanks Boathook. That’s what I did on last boat and it worked well, but on that boat the centre ‘third’ of the track was on flat bit of bridge deck, and where seat areas slanted down they were also flat, so wedges easy to make and fit. On current boat it’s a gradual and constant curve from one coaming to the other, which is why I’m tempted to curve track to fit. I’ll ring Barton and see what they have to say on the matter.

 

[vyv_cox]

Thanks Boathook. That’s what I did on last boat and it worked well, but on that boat the centre ‘third’ of the track was on flat bit of bridge deck, and where seat areas slanted down they were also flat, so wedges easy to make and fit. On current boat it’s a gradual and constant curve from one coaming to the other, which is why I’m tempted to curve track to fit. I’ll ring Barton and see what they have to say on the matter.

My son and I tried this for the track on his A-class catamaran. The curves are quite major, more than you are attempting. Our efforts were not successful using a press. The right way to do it is with rollers, which a decent engineering shop should be able to do for you quite cheaply.

 

[Spirit (of Glenans)]

Yes, on both my previous boat and my current one, the track runs across the middle of the cockpit and is horizontal (or straight) from end to end. The seats obviously slope from front to back, and the gap on each side is filled in with a hardwood wedge, shaped to fit.
It should be easy enough to do, but make up a template and produce a mock-up in softwood first. The curve should be easy enough to reproduce with an electric fretsaw. I would be inclined to bed it in a non-setting sealer and slightly countersink the bolt-holes through the bridge deck, for an enduring seal that will cope with the tensions and shock loads involved.

 

[lw395]

My son and I tried this for the track on his A-class catamaran. The curves are quite major, more than you are attempting. Our efforts were not successful using a press. The right way to do it is with rollers, which a decent engineering shop should be able to do for you quite cheaply.

Very often, these tracks come in two flavours, high profile which is a big stiff section capable of bridging a cockpit, and low profile which is a skinny section which can be curved and must be supported/bolted down along its length.
As for the issue of the car only putting the load on a few of its 'wheels' due to the curve, that will matter if the car is taking anywhere near its rated load. It can be got around by linking two short cars together instead of using a long one.
Unfortunately to get the full versatility, you may have to pay Harken prices...

 

[Deleted member 36384]

This may help for technique but they are bending to fit fore and aft, not athwart ships: -

Bending a Mainsheet Track

Also Harken, iirc, sell pre bent main sheet tracks.

 

[fredrussell]

Thanks for all replies. To answer a few points, the track will be mountable without any use of a press (Vyv and BOB) as it’s the less chunky version LW395 refers to. There’s a pic below showing cross section and it’s 27mm by 15mm or so. The T cut-out is for the hidden M6 bolts, which are to be spaced at 100mm intervals, say Barton.



...and Spirit, I know it’s not rational but I really want to avoid adding anything wooden to exterior of boat. I love it inside boats but one of the joys of this boat is a complete lack of the stuff exterior-wise, bar the tiller. To have a mount made for the straight track out of acetal or similar will be high I’m guessing. This is another reason I’m thinking of curving the track.

 

[Daverw]

You could make an acetal section to fit with simple tools and would not cost very much

 

[fredrussell]

You could make an acetal section to fit with simple tools and would not cost very much

I could make it, no problem, but a piece of nice thick acetal 1.5 metres long would be very expensive.

 

[anoccasionalyachtsman]

Mine stands on a number of varying length tubes.

 

[Daverw]

Acetal sheet, 1000x100x20 about £30

 

[fredrussell]

Acetal sheet, 1000x100x20 about £30

really? Where from? The stuff I was looking at on eBay was a lot more.

 

[john_morris_uk]

Our main sheet track is curved down either side but not by more than three or four cm at each end. It’s bolted to the deck/coach roof just aft of the helm (it’s a centre cockpit boat). I replaced it a few years ago and found the old one came off and sprang back to almost completely straight. New machine screws and backing pad with penny washers and the new track just squished into place. I’ve never noticed the curve causing the slightest problem with sheeting the main or using the traveller.

 

[Daverw]

really? Where from? The stuff I was looking at on eBay was a lot more.

Direct Plastics | Engineering Plastics | Large Stocks In All Sizes

 

[LittleSister]

Check the traveller you have, Fred, to see how it bears on the track. It may not be suited to a curved track.

My 'old' mainsheet track (Italian make, forgotten name) has a slight curve to fit the shallow arch of the aft deck on which it is mounted. The traveller ran on four wheels (one at each end, front and back). That track and traveller was destroyed in a violent accidental gybe, so I'm having a new one fitted.

The 'new' mainsheet track, which is a Barton one, was also going to be bent to fit the deck (the boatyard said they can easily do this using a press) until I noticed that the new traveller runs on two straight lines of about twenty plastic ball bearings, front and back (i.e. about 40 balls in total). If the track was bent it would be running on a few of those balls, and clearly would have only a small fraction of the strength and probably would not run easily. Therefore I am going to keep the track straight, and mounted on a shallow wooden base which accommodates the curve of the deck.

Probably not relevant to you, Fred, but IIRC Barton will supply the track curved (vertically or horizontally) if you provide the relevant dimensions. (I was considering doing this on a previous boat.)

 

[William_H]

My mainsheet track is also on the bridge deck and I like it there. However one annoying aspect is that it dams up dirt and sand between the track and the cabin wall. I would like to mount the track up a bit to allow sand etc to easily be washed out. (but can't be bothered) However it seems to me that you could do well bu putting some spacers under the ends of the track to bring it closer to flat but also to permit easy cleaning under the track. So I would advocate a compromise bend it as necessary but do give it spacers at the ends.
Just on the subject of track mounting. I found when my son grew up to be very strong he would haul on that mainsheet on my trailer sailer, to the point where the middle of the bridge deck started to rise. Got the main flat but did make the primitive traveller pretty hard to move. Anyway I added stay wires under neath the bridge deck onto the through bolts down to the side of the bunks One each side from near the middle. This at least strengthened the bridge deck against main sheet loads. ol'will

 

[fredrussell]

Daverw - cheers for the link, much cheaper than the stuff I was looking at, saved...

...and Little Sister, the same thought occurred to me re the amount of balls in contact with the track if curved. Sounds like you have the same one as me. You still at Southwold? I’ll pop up when restrictions eased.

Ol’ Will - had the same problem with muck accumulating forward of track. On this one I’ll be leaving a gap between track ends and coamings to improve the situation (hopefully).

I’ve decided I’ll make a wooden mount that I can try out for size and also use as a template for an acetal one later on. Thanks again to all respondents.

 

[knuterikt]

Removed my ball bearing one from Lewmar as it was eating balls at an insane rate. Replaced with one from Rutgerson with the roll-link. I got the track curved from the factory 56mm difference between middle and ends, length 1800mm. This one is with sliding bolt attachment so no problem aligning with existing bolt holes.
I believe the roll-link is better suited for a curved track.
Roll Link vs Ball Bearings - Rutgerson Marin