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Scare_Rab · 22-08-2010, 21:47

The main sheet raveller was in his shed when I bought the boat.

Pretty standard ... a piece of galvanised pipe; bent into a wide "U" shape, with 90' holes off-set on the ends to attach to the deck:

Went to pick it up and find it to be 80% rusted thru at attachment points.

Without the facility to make another: I'm wondering about using another (simpler) main-sheet system

perhaps just a lenght of spectra tied across the rear deck to existing strong eyes: , with a block for the bottom pulley to attach to.

questions comments suggestions welcomed

Doodles · 22-08-2010, 22:14

I don't know why the spectra wouldn't work. I've seen it used in place of all sorts of standing rigging, especially on racing boats. Strong enough to take the loads for sure. I use it in place of shackles on deck blocks.

Stillraining · 22-08-2010, 22:34

Quote:

Originally Posted by Doodles

I don't know why the spectra wouldn't work. I've seen it used in place of all sorts of standing rigging, especially on racing boats. Strong enough to take the loads for sure. I use it in place of shackles on deck blocks.

Doodles:

If you don't mind me asking..

How do you do that exactly, as I was thinking of doing the same....However I do want to use the tennis ball trick for standing blocks though so it might be next to impossible to do..

On topic: The only problem I see with using a line over rigid is having to ease or tighten the sheet every time you adjusted the traveler...its going to slow you down trimming wise but it would work....But you probably could get a Community collage to fix the original for free...possibly even get a new one built for dirt cheap...they need projects for their students after all..

Doodles · 22-08-2010, 23:06

Quote:

Originally Posted by Stillraining

Doodles:

If you don't mind me asking..

How do you do that exactly, as I was thinking of doing the same....However I do want to use the tennis ball trick for standing blocks though so it might be next to impossible to do..

On topic: The only problem I see with using a line over rigid is having to ease or tighten the sheet every time you adjusted the traveler...its going to slow you down trimming wise but it would work....But you probably could get a Community collage to fix the original for free...possibly even get a new one built for dirt cheap...they need projects for their students after all..

Various ways, but something like this ...PracticallySailing presents Joe Cooper

osirissail · 23-08-2010, 20:15

Assuming that you are intending to mount the main sheet traveler track athwartships there are two common positions: mid boom and end of boom.
- - Your main boom has to be specially manufactured to utilize a mid boom main sheet attachment. Otherwise you use a main sheet attached to the end of the boom.
- - Then it depends upon where your cockpit is located. Since the main sheet will be coming off the end of the boom you need to place the traveler at or slightly aft of the boom on the cabin top. If that happens to be in the middle of the cockpit then it would be advisable to build a strong arch to hold the main sheet traveler up above the cockpit but still below the boom. If the end of the boom does not extend over the cockpit then attach the main sheet traveler somewhere on the cabin top below or slightly aft of the end of the boom.
- - If you look at many different types of sailboats you will see many different solutions to positioning the main sheet traveler. Pick the one that most closely resembles your situation and go with that.

Northeaster · 24-08-2010, 04:14

I am not an engineer, but beware of the loads placed on two attachment points, when the pull will be in the middle of those points.

For example, in building rock / ice climbing anchors, you can have a 100 lb person hanging on 1 anchor bolt or screw, which will exert about 100 lbs on that anchor bolt. (juts hanging there, static load not dynamic load falling, which would be much greater)

If you place a 2nd anchor bolt and then attach the climber, using rope, to both anchors, the angle of the rope that leads to the climber is key. You have what is known as the death triangle, and if the anchors are far apart, and the rope short to the climber this will create a large pull inwards on each anchor (towards the other anchor) as well as down towards the climber.
You can end up with nearly 200 lbs exerted on each anchor from a 100 lb climber, when you only had 100 lbs on the single anchor.
If a longer rope is used, which reduces the angle (creating a long, thinner triangle, instead of a short, wide triangle) then this force is reduced, and you end up with redundancy (2 anchors vs 1) and less force on each anchor.

Why did I write all of that? Sound like you would have the upside down version of that, where the boom pulls upwards on a fairly tight (bad angle) spectra line, which would then exert likley twice the force of the upward pull on each anchor point.
The old pipe traveller woudl have likely not passed on the same forces to the anchor points, as it would have pulled more upwards I think. The spectra will pull up and much more inwards towards the other side's anchor point. I see the need for large backing plates.

I would personally consider buying or having a simple replacement one made.

Stillraining · 25-08-2010, 00:53

Very interesting Northeaster...thanks for the enligenment..

Never knew that in my old climbing days..

FWIW my two youngest have been doing a bit of rock work lately with some older friends from church...They bugged me enough to go pull all my old gear out of the back of a storage trailer I have..mainly for my helmet and harness.

I could not believe the weight of the racks I use to climb with....must have been 40 pounds of chocks, biners piton's and crap.

And no ...I dont fit my harness anymore...

Northeaster · 25-08-2010, 15:31

StillTraining - I hear you. I have a couple of sets of cams and nuts (the rest of you never mind - they are climbing nuts!!) that have been in storage for a while. Most of my rock gear is only 8 - 12 years old, but still outdated by today's standards. I pretty much gave up rock climbing (not that I was ever any good at it, but still had fun) a few years ago when i moved to be with my then girlfriend (now wife). I still ice climb actively though, most weekends late December - late April on the coastal ice in Nova Scotia, or interior ice in New Brunswick.

I don't climb anything too scary, but it's aweful nice t oclimb up and see the view from up there!