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rch701

Traveler strength over span

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I am dropping my traveler from the top of the coaming to bench level and possibly forward to the companionway to make it easier to move about. I have an extruded aluminum traveler that is 1" tall. I originally planned on leaving the 4-1/2" teak backer on it, but after fitting the traveler where I want it I was stumped on how to attach the wood to the cockpit and be able to one day refinish it. Can my traveler span the 26" wide footwell and only bolt on the benches? My sails are similar in size to a J/24 to give you an idea of stresses.

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I wouldn't.

But then I never stayed in a Holiday Inn Express.

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 I had a fractional 27 footer - slightly bigger than a J/24 with the traveller spanning the cockpit tub.

IIRC, it had a track with about a 4 " deep teak backer.  The backer was radiused on the bottom side - about 3" deep at the ends   

I believe there were about 1/4" thick metal L brackets with about 4" legs at either end of the backer.  I can't exactly how it all went together, but I believe the brackets were double bolted to the cockpit walls - creating fixed end rigidity.

I might have a photo or two lying around at home and I will see if I can dig them up in the next day or two. 

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Your 1" tall track is unlikely to work well, but the devil is in the details and you need to speak to your track/car vendor to be sure. Be certain you have details information about overall track length, number and spacing of fasteners you will be able to install as well as the unsupported length.

Harken makes High Beam track specifically for applications that have long unsupported spans. Stiffening can be done with backing blocks or T or L section.

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I will bust out a micrometer this weekend and calculate a moment of inertia to see what a safe load would be. If I can pull 50lbs on a 4:1 then the point load on center would be 200lbs. Double that for a rough gybe. I think I will back the spanning length with 1" square tube with 1/8" wall and have some beastly backing plates under the benches

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Harken has a nice mainsheet load calculator on their website. On the traveller parts page.

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1 minute ago, El Boracho said:

Harken has a nice mainsheet load calculator on their website. On the traveller parts page.

Also in the Harken print catalog there is a chart showing sail area and unsupported span which is acceptable for each type of track. I could not find it on their website .

In this catalog it's on page 94 for the small boat track: http://viewer.zmags.com/publication/285b6223#/285b6223/94

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I have a J24 main at 153sqft and I need a 30" span...so the chart says no-go. Thanks.

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2 hours ago, rch701 said:

I have a J24 main at 153sqft and I need a 30" span...so the chart says no-go. Thanks.

The chart indicates for a mid-boom arrangement with a 30" span, you can go up to about 260 sq ft with the Harken High Beam track (1 5/8" high).  Remember this is unsupported span, so no need for a backer.

Backer is only required if you want to use the Low Beam track and the span is  otherwise unsupported.  As your track is only 1" in height, you can consider yours to be  similar to the low beam track.  That is, it will require backing.

Remember - beam height or depth is the prime driver of stiffness for a given material.

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I probably overdid it but the calculated loads for multis seem to climb fast, went with 32mm, need more purchase at times for 1 handed ease. About a 24" span, I think, seems pretty solid to date.

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