Backward-looking at the cable traveler

Technical discussion of ARC products
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revintage
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Backward-looking at the cable traveler

Post by revintage »

Stumbled on the Supercat cable traveler in another forum, where SC19 owner Jonathan discussed converting from cable to track.
Anyway I am building a small supersimple 4.8x3m 14sqm SA cat as complement to the others. The build is lowbudget and made from stuff already in my workshop, except for a pair of hulls that I recently found.
Want to try the cable traveler as I have all components and it is lightweight. Used ballpark figures for calculating the forces involved.

One question remains: How much slack should it be? Used 200mm slack height in the middle, with 2000mm width.
cabletravelertest.png
Matt Haberman
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Re: Backward-looking at the cable traveler

Post by Matt Haberman »

Revantage,
I would say you want to keep it to a minimum. On the old cable traveler, the slack was sufficient so that when under load the traveler car cleared the beam when near the ends. This meant that there was an inch or two of extra clearance when near the center of the beam.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com
revintage
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Joined: November 24th, 2021, 3:46 am
Boat Make/Model: No Supercat, just admirer!

Re: Backward-looking at the cable traveler

Post by revintage »

Thanks Matt,
This explains the low profile of the underside of the original traveler. What was the diameter and width of the sheaves used? It rises another question though, how close to the ends of the cable, could the traveler move and be used?
Found a close up of the cable attachment of the SC17 and it seems to be a little inward of the center of the hull sideways. This should be in the ballpark of 200-210cm cable length.
Was it ment that the traveler trim should take a part of the load when centered?
If lowering max height in the middle to 150mm with 2000mm width, the force in either direction of the cable/rope will be 1500lbs with an upwards force of 450lbs from the sheeting, without help from the traveler trim. Still no problem for the 5mm DUX though :wink: .

If anyone wants to part from a dust collecting original traveler, feel free to ask for an offer. No need for it to be fully working.

Cheers
Lars
Car.jpg
Matt Haberman
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Re: Backward-looking at the cable traveler

Post by Matt Haberman »

Revintage,

The cable was 1/4" Diameter 1x19 SS. Not sure on the diameter of the sheaves off hand, but I believe they were 2" diameter. If I am not mistaken they were a standard catalog wirerope sheave with a plain bore, ie: no bearing. Or if there was a bearing it was just a plain bushing, I don't recall for certain.

I was not around when Bill did the calcs on the loading of the cable, but I suspect that he would have assumed the cable was taking 100% of the load and the traveler line was only used for positioning of the traveler car, not for carrying sheet loads. Keep in mind that the static sheet loads are probably not really an issue, the issue would be the shock loads that could be seen in an uncontrolled jibe situation.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com
revintage
Novice
Posts: 3
Joined: November 24th, 2021, 3:46 am
Boat Make/Model: No Supercat, just admirer!

Re: Backward-looking at the cable traveler

Post by revintage »

Thanks again Matt!
Think I have got the tools now. Will come back with the results when built.
You always have to begin your calculations with the static forces to get a reality check, then add a substantial security factor. Not worried though, as the boat will only be sailed by our lake house, not open sea.
If I decide to add a jib, I will take a closer look into Bill Roberts straight track self-tacker.
Cheers
Lars
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