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mast question #144730
06/03/08 08:12 PM
06/03/08 08:12 PM
Joined: Jun 2003
Posts: 56
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mitch Offline OP
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mitch  Offline OP
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somebody with some tech knowledge please illuminate: how much does a main halyard that goes over the top and cleats at the mast base cause compression, how much of a problem is this, can it or will it break the stick? Locking the halyard at the top is tough on some boats, reefing is a problem etc. the Hobie 21sc just cleats at the base... with new nonstretch line is the simple halyard cleat at the base a viable option? thanks for input

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Re: mast question [Re: mitch] #144731
06/03/08 09:45 PM
06/03/08 09:45 PM
Joined: Sep 2007
Posts: 224
Cincinnati, Ohio
Tri_X_Troll Offline
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I don't know much about the ones that cleat at the base of the mast, but the ones that cleat at the top usually have a second slug for reefing. At least the older H16's did when they still had reef points.

I know I wouldn't trust the cleat at the base of the mast on my 16. It just seems very flimsy.


Ryan - H16 I prefer to go sailing because baseball, football, tennis, and golf only require 1 ball!
Re: mast question [Re: mitch] #144732
06/03/08 10:53 PM
06/03/08 10:53 PM
Joined: Apr 2004
Posts: 713
WA, ID, MT
davefarmer Offline
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I used New England 1/4" V100 as the main hlyd on my SC20, cleated off at the base. It would stretch a bit in the 1st 10 min, I'd release the dnhl, tighten the main hlyd again, and I'd be good for the day. Need a serious cleat(Schaefer jam cleat?) solidly attached. Preferably one fastener into the cast aluminum base)drill and tap?). Also need a solid sheave at the masthead because it'll be under a lot of pressure. I never perceived any issues with the compression, but the SC extrusion is pretty beefy.

Dave

Re: mast question [Re: davefarmer] #144733
06/04/08 01:55 AM
06/04/08 01:55 AM
Joined: Jun 2006
Posts: 431
Netherlands
DennisMe Offline
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If I understand Newton's law (I'm always forgetting which one) it is that every action has an equal and opposite reaction.

I figure that means it makes no difference for compression where you cleat the main halyard. The loads on the halyard are no different, the mast must therefore provide the equal and opposite reaction. The only things I can see this affecting is mast top cleats will reduce halyard stretch and may help induce mast bend particularly in combination with rotation (but I'm not really sure on that).

Dennis

Re: mast question [Re: DennisMe] #144734
06/04/08 02:17 AM
06/04/08 02:17 AM
Joined: Jul 2001
Posts: 1,200
Vancouver, BC
Tornado Offline
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On a mast with the sail hooked at the top, the halyard line is unloaded during sailing...so the main luff is the only force making compression on the mast...and most of that is from the downhaul force.

Now if you run a base cleat instead of the top hook, now you've got two forces acting to make mast compression...the loaded halyard and still the sail luff. Input force is still primarily the the downhaul, but you get 2:1 purchase (halyard + luff) compressing the mast.

The extrusion can easily take this, assuming you've got reasonable diamonds and don't get crazy with >16:1 downhaul purchase. Biggest concern will be the top sheave & it's mount pin...not usually designed for these kind of loads.

The base cleat needs to handle at least as much force as you can put on the downhaul line..plus some margin for gusts, etc.

Mike.


Mike Dobbs
Tornado CAN 99 "Full Tilt"
Re: mast question [Re: mitch] #144735
06/04/08 06:55 AM
06/04/08 06:55 AM
Joined: Jun 2001
Posts: 12,310
South Carolina
Jake Offline
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Jake  Offline
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Quote
somebody with some tech knowledge please illuminate: how much does a main halyard that goes over the top and cleats at the mast base cause compression, how much of a problem is this, can it or will it break the stick? Locking the halyard at the top is tough on some boats, reefing is a problem etc. the Hobie 21sc just cleats at the base... with new nonstretch line is the simple halyard cleat at the base a viable option? thanks for input


It doubles. If you pull 100 pounds on the luff of a sail that is hooked at the top, you get 100 pounds of compression on the mast. If you pull 100 pounds on the luff of a sail where the halyard freewheels at the top and is cleated at the base, you get 100 pounds of compression from the sail luff and from the halyard = 200 lb of compression no the mast.

It still baffles me how the monohull world has yet to catch up to this novel concept (except for the America's Cup boats).


Jake Kohl
Re: mast question [Re: mitch] #144736
06/04/08 01:46 PM
06/04/08 01:46 PM
Joined: Aug 2001
Posts: 1,307
Asuncion, Paraguay
Luiz Offline
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Asuncion, Paraguay
The attached picture might help.

[Linked Image]

Attached Files

Luiz
Re: mast question [Re: mitch] #144737
06/04/08 02:08 PM
06/04/08 02:08 PM
Joined: Sep 2007
Posts: 571
Hamburg
Smiths_Cat Offline
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Hamburg
I am pretty sure, that the mast of most beach cats can handle the doubled load. But on some lightweight constructions (e.g. Acat) I would be careful.

However the luff tension acts not only as compression force on the mast, it bends it backwards as well, an effect which is normally desired. With a conventional halyard you will roughly double the bending for the same amount of downhaul tension, hence the leach will open more than usual, or with the same twist (leach opening), you will have less downhaul and with that a fuller sail. But maybe this aspect is of a lower importance if you don't sail races.

Cheers,

Klaus

Re: mast question [Re: Jake] #144738
06/04/08 03:44 PM
06/04/08 03:44 PM
Joined: Oct 2002
Posts: 1,226
Atlanta
bvining Offline
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Atlanta
Quote
It still baffles me how the monohull world has yet to catch up to this novel concept


How would you propose to hook and unhook a fixed (non rotating) monohull mast? I suppose you could rig some sort of a trip line, to a mechanical catch at the top of the mast, but that seems more complex than a halyard to hold the sail up.

Bill

Re: mast question [Re: bvining] #144739
06/04/08 03:57 PM
06/04/08 03:57 PM

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you could utilize a claw and bead system similar to the hobie16...

Re: mast question [Re: bvining] #144740
06/04/08 04:09 PM
06/04/08 04:09 PM
Joined: Jul 2001
Posts: 1,200
Vancouver, BC
Tornado Offline
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There is s solution for hooking a mainsail without requiring rotation.

The simple cable with stopper system used on a lot of dinghy jib setups could be beefed up to hold the main. These use a catch fitting that the stopper engages in. The problem is how do you un-catch it when needing to drop sail?

Well, we use a locking box with an interesting geometry on Afterburner...the halyard is pulled through the box until a swaged on stainless slug passes into the box...then drops into a notch & locks in place. To disengage, we apply more tension to the halyard, pulling the slug further through the box until it clears the notch. It is now unable to re-engage in the notch as we release the halyard.

This exact same design lock fittng is downsized and used on Marstrom Tornado forstays for jib halyards.



Quote
Quote
It still baffles me how the monohull world has yet to catch up to this novel concept


How would you propose to hook and unhook a fixed (non rotating) monohull mast? I suppose you could rig some sort of a trip line, to a mechanical catch at the top of the mast, but that seems more complex than a halyard to hold the sail up.

Bill


Mike Dobbs
Tornado CAN 99 "Full Tilt"
Re: mast question [Re: Tornado] #144741
06/04/08 04:54 PM
06/04/08 04:54 PM
Joined: Mar 2005
Posts: 160
claus Offline
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I would guess that the mast bending characteristics should be more or less in accordance with the load on the luff/halyard. If you modify the system, the mast will be bent back less or more, probably not desireable? Also, if the halyard is not in a rail (for example an a H16 you would have to run it outside the mast), if the mast is bent back, the distance from top to bottom gets shorter and thus the halyard tension would decrease.

Re: mast question [Re: ] #144742
06/04/08 06:12 PM
06/04/08 06:12 PM
Joined: Sep 2007
Posts: 224
Cincinnati, Ohio
Tri_X_Troll Offline
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If I recall, the C-Scow uses a system similar to that of the hobie 16


Ryan - H16 I prefer to go sailing because baseball, football, tennis, and golf only require 1 ball!
Re: mast question [Re: bvining] #144743
06/04/08 06:27 PM
06/04/08 06:27 PM
Joined: Jun 2001
Posts: 12,310
South Carolina
Jake Offline
Carpal Tunnel
Jake  Offline
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Quote
Quote
It still baffles me how the monohull world has yet to catch up to this novel concept


How would you propose to hook and unhook a fixed (non rotating) monohull mast? I suppose you could rig some sort of a trip line, to a mechanical catch at the top of the mast, but that seems more complex than a halyard to hold the sail up.

Bill


Who said the mast shouldn't rotate?


Jake Kohl
Re: mast question [Re: Jake] #144744
06/05/08 06:55 AM
06/05/08 06:55 AM
Joined: Oct 2002
Posts: 1,226
Atlanta
bvining Offline
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bvining  Offline
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Quote
Who said the mast shouldn't rotate?


I'm not saying they shouldnt, I'm saying they usually dont.

Re: mast question [Re: Tornado] #165073
01/15/09 07:02 PM
01/15/09 07:02 PM
Joined: Dec 2005
Posts: 55
Los Angeles, CA
chrisun Offline
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chrisun  Offline
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Posts: 55
Los Angeles, CA
Originally Posted by Tornado

Well, we use a locking box with an interesting geometry on Afterburner...the halyard is pulled through the box until a swaged on stainless slug passes into the box...then drops into a notch & locks in place. To disengage, we apply more tension to the halyard, pulling the slug further through the box until it clears the notch. It is now unable to re-engage in the notch as we release the halyard.


I like this system. Works well. Easy to engage and disengage.

However, there was an interesting point made about compression on the sheave. Unfortunately this system does not unload the sheave when it is engaged. The halyard still carries the load over the halyard sheave.

Last edited by chrisun; 01/15/09 07:05 PM.

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