SAIL ATTACHMENT TO CARBON MAST-NO TRACK OR BOOM

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DONRICARDO
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Joined: Sat Dec 27, 2008 12:49 pm

SAIL ATTACHMENT TO CARBON MAST-NO TRACK OR BOOM

Post by DONRICARDO »

Anyone ever use beads or hoops to attach a single ply sail to a freedom mast? I'm replacing the wrap around and have been told that mast track should not be screwed into the mast. Plus I have the problem of getting the sail over the wishbone hoist tackle about 10' above the deck. I probably need to devise a protective device to prevent hang ups.
scott
posted this the other day but don't see it???

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GeoffSchultz
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Re: SAIL ATTACHMENT TO CARBON MAST-NO TRACK OR BOOM

Post by GeoffSchultz »

I don't have an answer to your rigging question, but I will say that it's easy to hit "save" instead of "submit" when trying to post. If you did that, you'll see "Load" as a button below.

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a1john
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Re: SAIL ATTACHMENT TO CARBON MAST-NO TRACK OR BOOM

Post by a1john »

You should look up "Forth and Back" sail lacing as it works remarkably easy and never jams. There are lots of references to "Sail Lacing". Probably you can try taping over that up-haul fitting for the wish-bone. Good luck John Jones

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Michel
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Re: SAIL ATTACHMENT TO CARBON MAST-NO TRACK OR BOOM

Post by Michel »

DONRICARDO wrote:Anyone ever use beads or hoops to attach a single ply sail to a freedom mast?
Have a look at the G10 rig in the files section. What you're suggesting is done several times in the NL's; two F33's. There's a lot of knowledge about optimising parrel rigs here; we have an active racing community with classic Dutch fishing Lemsteraken that have such sails.
Michel Capel, Freedom 44 #4 1981 'Alabama Queen', NED8188, cat ketch with wishbones, home port Enkhuizen, the Netherlands, 52*42.238'N 005*18.154'E.

katorpus
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Re: SAIL ATTACHMENT TO CARBON MAST-NO TRACK OR BOOM

Post by katorpus »

You're right that the sail track shouldn't be screwed into the mast, but the factory installed mine with about a bazillion pop rivets. Use the ones made from Monel. Google up an online source. I've replaced a few, but the masts don't seem to be any the worse for it...and my boat was built in 1981, then re-rigged at the factory with goosenecks, booms & sail track in late 1981.

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Michel
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Re: SAIL ATTACHMENT TO CARBON MAST-NO TRACK OR BOOM

Post by Michel »

On my original 1981 mizzen the strongstrack is riveted with stainless rivets. On my 2000 GMT built main mast with a 12mm wall, the Antal track is screwed with stainless machine screws. The screws seem to hold better than the rivets, but that is probably because of the bigger wall thickness.
Michel Capel, Freedom 44 #4 1981 'Alabama Queen', NED8188, cat ketch with wishbones, home port Enkhuizen, the Netherlands, 52*42.238'N 005*18.154'E.

katorpus
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Re: SAIL ATTACHMENT TO CARBON MAST-NO TRACK OR BOOM

Post by katorpus »

I think there's more to consider than just "holding power" here.

Unless you're using machine screws with a constant shaft diameter (which would require "tapping" into the mast wall), then every one of those holes, if filled with a screw, is going to be stressing the mast wall radially outward from the hole...trying to "grow" toward the next hole...with the wedge shape of the screw trying to "expand" the hole, aided by the tension of the sail.

Sheet metal screws, self-tapping screws, and wood screws all serve as a "wedge". The resin-infused carbon fiber mast wall is a "friable" construction, and the screw, when inserted, is essentially fracturing the resin around the pilot hole and shredding the fibers in the process...multiplied times however many screws are being installed (in what amounts to one or two essentially "straight lines" up one side of the mast, depending on whether the track has offset holes or "aligned" holes.)

Beyond that, the greater strength of a screw (in anything) is in "shear", rather than "tension" (It's more likely to "pull out" than to "break" from the force of gravity on whatever it's holding up...in this case, the weight of the sail & track). A machine screw, tapped only into the mast (no backing plate of harder material) is not going to have a lot of strength in tension.

The "mushroomed" pop-rivet is compressing the walls of the mast on both sides of the hole that it's in. The force in tension is spread over a much larger area, and the rivet isn't trying to "enlarge" each of the holes.

When the screw pulls out, the solution is to replace it with a larger screw, a larger hole, on and on with more of the same radial stress. When a rivet fails, it will likely be from the head popping off, and the solution is to bore out the shaft and replace it with a (same size) rivet in the original hole.

I'll stick to the rivets, thank you. You are, after all, essentially putting a screw into a "tube made out of glass", except that this "tube" is designed to flex, which is only going to serve to significantly "enhance" the bad aspects of the whole "screw thing"... fore & aft flex will tend to alternately "open" the hole and compress it (around the incompressible screw), while side-to-side flex will tend alternately open one side of the hole while compressing the other side against the screw. This isn't happening on just a purely "microscopic" basis (or theoretical basis), and is ongoing and continuous, whether sailing or not.

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