Straightening mainsheet traveller

[sailoppopotamus]

My 30ft boat has a next-to-useless pin-stop mainsheet traveller so I bought an Antal traveller to replace it with. The track is supported across its length, but unfortunately follows the curvature of the cockpit in the vertical direction. While the radius of curvature is not too great (the center of the 1300mm track is around 30mm higher than its ends, so not more than 19m following Harken's formula) I think I will get much better performance and robustness from the system if the track is straight. So, having measured the profile of the current track, my plan is to use a friend's CNC to fashion a support to go between the track and the deck to take up the curvature. Any suggestions as to what material to use for this? Options are:

1. Wood, which will inevitably rot and degrade well before the rest of the system is due for replacement.
2. Acetal, which seems to have poor resistance to UV, leading me to think that it will also not last long.
3. HDPE, variants of which are apparently resistant to UV, but which is apparently very difficult to glue onto anything. Since it won't be glued to the deck, I would effectively be adding a massive washer between the track and the deck. This makes me worried about how the fasteners will cope with the loads involved, which will now exert a larger torque to both the fastener and the deck.

Any suggestions as to how to proceed? If possible I would prefer something that is black so that it doesn't stand out visually under the black track.

 

[mrming]

I’m assuming these are effectively shims to go under the ends of the track.

If they’re not huge, there’s a UV resistant flavour of Delrin (527) in black that might suit. It comes in rod or sheet form.

If I’m visualising this correctly the shims will be in compression, in a sandwich with the track bolted through them. There would need to be enough bolts to hold the shims in place securely.

If that’s roughly right, the fixings need to be adequate (and have backing pads or large washers) for the load of the car / mainsheet (think sheet cranked on, or crash gybe), and these shims would not alter that in any meaningful way imo. I would use a non adhesive sealant such as butyl to seal the bolts in the normal way.

 

[PabloPicasso]

Why not fibre glass the infill? That'd be strong, UV resistant, and permanent.

 

[ithet]

I fitted a centre mainsheet track which had to be raised about 20mm. I used blocks of cast nylon which is easy to work and the natural white colour is unobtrusive. I ordered from one of the eBay sellers who cut it approximately to my required size.

Edit ofter re-reading post - also available in black, bedded down on sealant ok.

 

[sailoppopotamus]

I’m assuming these are effectively shims to go under the ends of the track.

If they’re not huge, there’s a UV resistant flavour of Delrin (527) in black that might suit. It comes in rod or sheet form.

If I’m visualising this correctly the shims will be in compression, in a sandwich with the track bolted through them. There would need to be enough bolts to hold the shims in place securely.

If that’s roughly right, the fixings need to be adequate (and have backing pads or large washers) for the load of the car / mainsheet (think sheet cranked on, or crash gybe), and these shims would not alter that in any meaningful way imo. I would use a non adhesive sealant such as butyl to seal the bolts in the normal way.

I was thinking of a solid piece rather than multiple shims, sandwiched between the track and the deck as you say. I don't think I have any say in the number of bolts -- I haven't opened the package but I imagine the Antal track has holes for bolts 10cm apart as most tracks do. Strength is definitely a concern, having the track part from the deck would pose a serious threat to life and limb.

Why not fibre glass the infill? That'd be strong, UV resistant, and permanent.

Not sure how I'd do that. Are you suggesting I make my own fiberglass rod out of multiple layers of glass and cut that down to size on the CNC? I guess I could just buy a fiberglass rod, I don't know why I didn't think of that straight away.

 

[mrming]

I was thinking of a solid piece rather than multiple shims, sandwiched between the track and the deck as you say. I don't think I have any say in the number of bolts -- I haven't opened the package but I imagine the Antal track has holes for bolts 10cm as most tracks do. Strength is definitely a concern, having the track part from the deck would pose a serious threat to life and limb.

I probably used the wrong word with “shim”. I also envisaged one piece on either side. I had a similar arrangement on my last boat but spanning the cockpit to slightly sloping seats. I replaced an under-spec previous track which broke. We used hardwood wedges and Harken high beam track and never had any trouble with it despite racing hard in all conditions.

 

[sailoppopotamus]

I fitted a centre mainsheet track which had to be raised about 20mm. I used blocks of cast nylon which is easy to work and the natural white colour is unobtrusive. I ordered from one of the eBay sellers who cut it approximately to my required size.

Edit ofter re-reading post - also available in black, bedded down on sealant ok.

How long ago was this, and have you noticed any deterioration over time? I'm no materials expert, but according to Google nylon seems to also be susceptible to UV -- nylon 12 less so. But I'm not sure how it compares against UV-resistant Delrin.

 

[PabloPicasso]

Strength is definitely a concern, I could just buy a fiberglass rod, I don't know why I didn't think of that straight away.

Glass up your own, build it up in place, buy a rod peice. Whatever works out easiest. Sure the boat is made of the stuff isn't it?

 

[Tranona]

Don't know why you think wood will rot. Profile a bit of hardwood (teak, iroko or mahogany) to give you a flat top and curved underside, protect the exposed sides with epoxy (although to be honest a good woodstain would be almost as good) and bed down with a polyurethane sealant adhesive. Presumably you are through bolting the track, in which case the wood spacer with be almost totally encapsulated.

 

[William_H]

I find on my traveler track that water and debris collect in front of the track. As all load will be upwards ie on bolts regardless of what you have as a spacer I would advocate using a stack of washers or similar small spacer just at the bolt location. ie don't try to fill the gap. Use all the holes for bolts and note it is the support under neath the GRP deck that matters. ol'will

 

[sailoppopotamus]

Don't know why you think wood will rot. Profile a bit of hardwood (teak, iroko or mahogany) to give you a flat top and curved underside, protect the exposed sides with epoxy (although to be honest a good woodstain would be almost as good) and bed down with a polyurethane sealant adhesive. Presumably you are through bolting the track, in which case the wood spacer with be almost totally encapsulated.

The track will be through bolted, so only the sides of the wood spacer would be exposed. If I were going down that route I think the woodstain would be a safer option -- maybe I'm wrong but I don't know how well the epoxy would stick to the wood before separating or going a nasty yellow. But still I'm not too confident that I wouldn't have to touch this up every now and then. Maybe I'm wrong.

I find on my traveler track that water and debris collect in front of the track. As all load will be upwards ie on bolts regardless of what you have as a spacer I would advocate using a stack of washers or similar small spacer just at the bolt location. ie don't try to fill the gap. Use all the holes for bolts and note it is the support under neath the GRP deck that matters. ol'will

Debris collect all over my track, so I think they'd just get stuck under the track in this configuration. The loads will be taken be the bolts, but won't be exactly upwards on anything deeper than a beam reach. I don't mean to be dismissive, this would certainly be a far easier solution than fabricating a whole wedge.

 

[davidmh]

Why do you think the 30mm vertical dip will make the system less robust. The mainsheet take off angle varies hugely depending on the boom setting so will the 30mm effect make any difference. Many yachts have a curved deck where the traveller is mounted and seem to have no problems. What is the maximum mainsail/load capacity of your track and how does it compare with your likely loads.

David MH

 

[Spirit (of Glenans)]

My boat was fitted from new by the previous owners with a mainsheet track in the cockpit, necessitating wedge-shaped teak infills under the ends where the flat shape of the track diverged from the sloping profile of the cockpit seats. This arrangement has worked perfectly for 22 years, the only upkeep required being the same as that for the other teak on the boat. The only flaw I can comment on is that there should have been a gap designed in at the lowest point at each end, in order to allow water to flow away freely towards the aft end of the seats.
I would recommend to the OP that rather than making his infill in one piece, that he makes two wedges, with the centre of the track in direct contact with the structure of the boat.
This would be easier to achieve with a couple of bits of scrap hardwood begged from a joinery works for instance. It would have a lower profile than a one-piece structure and would be more elegant than something concocted from a stack of washers or similar.

 

[dansaskip]

I'm with davidmh on this 30mm is nothing, I can't see that would make it any less robust or perform poorly. My mainsheet track is curved like this and never had any problems with it. My advice would be to save yourself the trouble and leave as is.

 

[Spirit (of Glenans)]

I'm with davidmh on this 30mm is nothing, I can't see that would make it any less robust or perform poorly. My mainsheet track is curved like this and never had any problems with it. My advice would be to save yourself the trouble and leave as is.

To my mind, the traveller car would tend to 'dwell' at the point where the mainsheet is perpendicular to the curvature of the track for a given state of trim, i.e. it will not go all the way to the end of the track willingly, if the sheet is not eased, which is not what is usually desired, whereas a flat track will allow the car to travel all the way to the end when released.

 

[mrming]

I find on my traveler track that water and debris collect in front of the track. As all load will be upwards ie on bolts regardless of what you have as a spacer I would advocate using a stack of washers or similar small spacer just at the bolt location. ie don't try to fill the gap. Use all the holes for bolts and note it is the support under neath the GRP deck that matters. ol'will

Good suggestion this - no actual need to fill the gap. Some nicely shaped spacers could do the job well.

 

[sailoppopotamus]

Why do you think the 30mm vertical dip will make the system less robust. The mainsheet take off angle varies hugely depending on the boom setting so will the 30mm effect make any difference. Many yachts have a curved deck where the traveller is mounted and seem to have no problems. What is the maximum mainsail/load capacity of your track and how does it compare with your likely loads.

David MH

The SWL is 880kg, which seems enough for a 18 sqm mainsail. The manufacturer presumably quotes this for a straight track, with curved tracks reducing this by an unknown amount. Which is logical, since the car will be effectively running on fewer ball bearings. While 30mm might not sound like much, my track's minimum radius of curvature (i.e. most of the deflection) is at the centre, with its ends being relatively straight. I make the radius of curvature to be around 5m there, which seems like a lot, so I'm worried that the car will be quite stressed at the position where it will be most of the time. Either way, a curved track means more friction and more stress on the bearings, which I would prefer to avoid.

I'm with davidmh on this 30mm is nothing, I can't see that would make it any less robust or perform poorly. My mainsheet track is curved like this and never had any problems with it. My advice would be to save yourself the trouble and leave as is.

I'm definitely replacing the track, so there is no 'leave as is' option. The other options available would be to get a shop to bend the track to the desired shape, or just let it bend into place when bolting it down. I imagine that the former option is just as much work as making the wedge, as I'd have to make the wedge anyway so that the shop can match its profile. The latter option is the least appealing as it will exert unnecessary strain on the bolts and would leave me permanently stressed about the ability of the track to survive a crash gybe without tearing itself off the deck.

 

[sailoppopotamus]

My boat was fitted from new by the previous owners with a mainsheet track in the cockpit, necessitating wedge-shaped teak infills under the ends where the flat shape of the track diverged from the sloping profile of the cockpit seats. This arrangement has worked perfectly for 22 years, the only upkeep required being the same as that for the other teak on the boat. The only flaw I can comment on is that there should have been a gap designed in at the lowest point at each end, in order to allow water to flow away freely towards the aft end of the seats.
I would recommend to the OP that rather than making his infill in one piece, that he makes two wedges, with the centre of the track in direct contact with the structure of the boat.
This would be easier to achieve with a couple of bits of scrap hardwood begged from a joinery works for instance. It would have a lower profile than a one-piece structure and would be more elegant than something concocted from a stack of washers or similar.

Thanks for that. Maybe I was too quick to dismiss wood as an option, perhaps because the 35 year old wood on the outside of my boat is in pretty poor shape. There will be a few cm of space on either side of the track where water can flow around and drain onto the seats/cockpit floor.

 

[ithet]

How long ago was this, and have you noticed any deterioration over time? I'm no materials expert, but according to Google nylon seems to also be susceptible to UV -- nylon 12 less so. But I'm not sure how it compares against UV-resistant Delrin.

About three years I think. No sign of degredation. It is a big lump of nylon about 50 X 20 X 20 mm.

 

[bristoljim]

My 30ft boat has a next-to-useless pin-stop mainsheet traveller so I bought an Antal traveller to replace it with. The track is supported across its length, but unfortunately follows the curvature of the cockpit in the vertical direction. While the radius of curvature is not too great (the center of the 1300mm track is around 30mm higher than its ends, so not more than 19m following Harken's formula) I think I will get much better performance and robustness from the system if the track is straight. So, having measured the profile of the current track, my plan is to use a friend's CNC to fashion a support to go between the track and the deck to take up the curvature. Any suggestions as to what material to use for this? Options are:

1. Wood, which will inevitably rot and degrade well before the rest of the system is due for replacement.
2. Acetal, which seems to have poor resistance to UV, leading me to think that it will also not last long.
3. HDPE, variants of which are apparently resistant to UV, but which is apparently very difficult to glue onto anything. Since it won't be glued to the deck, I would effectively be adding a massive washer between the track and the deck. This makes me worried about how the fasteners will cope with the loads involved, which will now exert a larger torque to both the fastener and the deck.

Any suggestions as to how to proceed? If possible I would prefer something that is black so that it doesn't stand out visually under the black track.

I used bobbins of black Nylon 6 for each bolt & did not see any degredation over 10 years - very easy to make from round bar slightly bigger diameter than the width of the track - a lathe makes a better job but I think you could manage with hacksaw & drill. The track is not bent with different size bobbins.
Jim