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Old 18-10-2014, 12:29   #1
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Question re Mast/Boom Tracks

It seems that everybody has a track in the boom and the mast for affixing the foot and luff of the mainsail respectively. There are various methods of connecting the sail to the tracks (e.g. sail slugs or boltrope) but everybody has tracks. At the same time, jammed tracks seems to be a frequent problem.

My question is this: would it be feasible to run one line along the boom and another line along the mast, and then just hank on the foot and luff to those lines, just as you hank on the luff of a headsail to the forestay? If so, hanks on a line would be less likely to jam than slugs in a track, no?

I suppose this is more or less how it was done in the Age of Sail, as I don't think they had finely machined steel tracks running up the wooden mast. Time for a revival? ...or maybe there's some very obvious problem I'm missing?

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Old 18-10-2014, 16:00   #2
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Re: Question re Mast/Boom Tracks

Loose footed sails are common so don't require anything to hank on to.
The problem with the main would be getting the line tight enough to keep the luff behind the mast rather than having it bellying out. In the "age of sail", they generally used mast rings or parrell beads to keep the alignment with the mast. (Edit: or luff lacing)
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Old 18-10-2014, 16:13   #3
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Re: Question re Mast/Boom Tracks

In the real world, jams in the mainsail track are not so common as you suggest. If kept lubed, even simple slugs work well, and the more modern systems (Strong Track for example) are trouble free.

Using a "line" up the aft side of a mast, and using hanks thereon would result in horrid sail shape. Using a wire similar in size and strength to ones forestay could reduce that part of the problem, but would put very high compression loads on the spar, loads that were not part of the design criteria.

I reckon that this is a bad solution to a non-problem!

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Old 18-10-2014, 16:51   #4
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Re: Question re Mast/Boom Tracks

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Originally Posted by StuM View Post
Loose footed sails are common so don't require anything to hank on to. The problem with the main would be getting the line tight enough to keep the luff behind the mast rather than having it bellying out.
By "line" here you mean the main halyard? So you'd have the tack fixed permanently near the gooseneck, and then just pull like hell on the halyard after raising the main until the luff was tight? That's not what I had in mind, but that's interesting. I take it you think that's unworkable, because the halyard couldn't be kept tight enough? If so, why do you think so? Stretch in the halyard, not enough winching power, hard to tie off?

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In the "age of sail", they generally used mast rings or parrell beads to keep the alignment with the mast. (Edit: or luff lacing)
Gotcha. That's probably worse than a track, looks very friction-y.
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Old 18-10-2014, 16:55   #5
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Re: Question re Mast/Boom Tracks

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In the real world, jams in the mainsail track are not so common as you suggest. If kept lubed, even simple slugs work well, and the more modern systems (Strong Track for example) are trouble free.
Since everybody has them these days, I'm sure they're just fine most of the time, and I'd have no problem using them if that's the best option. But this alternative occurred to me and I'm curious about it.

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Using a "line" up the aft side of a mast, and using hanks thereon would result in horrid sail shape. Using a wire similar in size and strength to ones forestay could reduce that part of the problem
I had in mind either a wire or a non-creep synthetic like dynex dux, PBO, etc.

Quote:
but would put very high compression loads on the spar, loads that were not part of the design criteria.
True. The loads would now be concatenated at the mast's top and bottom where the line is attached, instead of dispersed at several points along the length of the mast where the slugs/etc are attached. I guess I'd have to ask the mast manufacturer or a N.A. to find out for sure whether that would be an issue.
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Old 18-10-2014, 18:00   #6
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Re: Question re Mast/Boom Tracks

Well, we have a groove ...

I do not like tracks. I would not buy a boat with one.

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Old 18-10-2014, 18:09   #7
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Re: Question re Mast/Boom Tracks

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Well, we have a groove ...

I do not like tracks. I would not buy a boat with one.

b.
Could you explain the difference? To me it sounds like the same thing - some gizmo (e.g. slug) sliding up and down in a groove/track/whatever. And why do you prefer grooves?
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Old 18-10-2014, 19:56   #8
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Re: Question re Mast/Boom Tracks

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Could you explain the difference? To me it sounds like the same thing - some gizmo (e.g. slug) sliding up and down in a groove/track/whatever. And why do you prefer grooves?
A groove is like a slit that widens towards the bottom, it takes many shapes but it just as the name says it - a groove inside the spar.

A track is like a tee bar attached with its narrow end to the spar.

I prefer grooves because they do not detach from the mast in the middle of a windy night.

I think on bigger yachts when loads and friction become monumental only a track is the way (?).

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Old 18-10-2014, 20:00   #9
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Re: Question re Mast/Boom Tracks

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Originally Posted by KISS View Post
By "line" here you mean the main halyard? So you'd have the tack fixed permanently near the gooseneck, and then just pull like hell on the halyard after raising the main until the luff was tight? .
No, I mean the "line" you talked about as in:
"and another line along the mast, and then just hank on the foot and luff to those lines,"
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Old 18-10-2014, 20:08   #10
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Re: Question re Mast/Boom Tracks

That guy needs to go sailing...
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Old 18-10-2014, 20:47   #11
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Re: Question re Mast/Boom Tracks

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Originally Posted by barnakiel View Post
A groove is like a slit that widens towards the bottom, it takes many shapes but it just as the name says it - a groove inside the spar.

A track is like a tee bar attached with its narrow end to the spar.

I prefer grooves because they do not detach from the mast in the middle of a windy night.

I think on bigger yachts when loads and friction become monumental only a track is the way (?).

b.
Ah, I understand. There's no difference in terms of friction/jamming, but the groove can't fly off the boat in a gale. Makes sense.
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Old 18-10-2014, 20:53   #12
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Re: Question re Mast/Boom Tracks

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No, I mean the "line" you talked about as in:
"and another line along the mast, and then just hank on the foot and luff to those lines,"
Gotcha, but I was talking about a wire or non-creep synthetic, fixed just like a stay, so that's not an issue.
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Old 18-10-2014, 23:55   #13
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Re: Question re Mast/Boom Tracks

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Gotcha, but I was talking about a wire or non-creep synthetic, fixed just like a stay, so that's not an issue.
You really haven't sailed at all have you?

Get out on boat in a decent wind and see how much the forestay sags to leeward.
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Old 19-10-2014, 00:48   #14
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Re: Question re Mast/Boom Tracks

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You really haven't sailed at all have you?

Get out on boat in a decent wind and see how much the forestay sags to leeward.
Taskers - Stainless Steel Wire Rope Specification - Perth, WA

As you can see in the chart, 8mm 1x19 316 stainless wire stretches .1853% of its length under 1000kg. A 40' stay, for example, would stretch less than an inch. If a stay is visibly sagging, it's because it was loose to begin with, not because it's stretching under the load. There may be good reasons not to do what I'm inquiring about, but stretchiness of the wire is not one of them.
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Old 19-10-2014, 01:27   #15
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Re: Question re Mast/Boom Tracks

In theory, there is no difference between theory and practice. In practice, there is.

Simple trigonometry will tell you that a 1 inch stretch is not the same as a 1 inch deflection over 40 feet.

Lets take your 1 inch over 40 feet.

Looking at the mid point, we can treat it as two triangles each with an adjacent side of 240 inches and a hypotenuse of 240.5 inches. What's the length of the opposite side (the deflection)?

b = Sqrt(c^2 - a^2)
= Sqrt (240.5^2 - 240^2)
=Sqrt (57,840.25 - 57,600)
=Sqrt(240.25)
= 15.5 inches.

So your 1 inch stretch will allow well over a foot of deflection at the centre point

If you want, we can do it using hyperbolics instead of straight lines, but it won't make that much difference.
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