Laurent Giles 'Jolly Boat' Exeter |
29er GBR 074 Tynemouth |
J24 (Sail No. 4239) Dartmouth |
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for 2 to 1 or not 2 to 1 |
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Alto-Tim
Newbie Joined: 23 Jun 11 Location: United Kingdom Online Status: Offline Posts: 6 |
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Topic: for 2 to 1 or not 2 to 1 Posted: 24 Aug 11 at 10:58pm |
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If you get less compression forces with a 2 to 1 compared with the 1-to-1,the issue of compression forces is due to the way you tighten the halyard before cleating it off.
So if you use a wire and a rack there is less compression forces due to the halyard tension. Tension on the halyard at is applied by the kicker or the Cunningham. So if you have high halyard tension will this mean the top of the mast will respond more to gusts quicker because the top part of the mast is under tension?. So by not having high loads on your halyard must mean the mainsail will power up because the mast will be stiffer and not bend off so much in the gusts. All these questions come about looking for more power out of the rig
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JimC
Really should get out more Joined: 17 May 04 Location: United Kingdom Online Status: Offline Posts: 6649 |
Post Options Quote Reply Posted: 25 Aug 11 at 12:34am | |
Its not just the static tension on the halyard, if any, its the effect of the downhaul loads pulling down on the halyard. Given a stable mylar sail one of the the main effects of the downhaul is mast bend, so in theory I suppose you ought to get more mast bend for a given downhaul tension/amount pulled down the mast.
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G.R.F.
Really should get out more Joined: 10 Aug 08 Location: United Kingdom Online Status: Offline Posts: 4028 |
Post Options Quote Reply Posted: 25 Aug 11 at 8:32am | |
Ah, think I get it now this is an Alto rig right? The Mk2 Sail? My thinking of 2-1 was the combination of a pulley at the head and the foot as mine has. The Alto is underpowered, at least the 2nd generations were imv, it also badly needs a mast head kite and a proper jib. The Solution would be for it to use a B14 rig, again imv. But the design criterion was for it to be used by skilled helms and semi to unskilled crews and it was originally going to be a hiker, which is why it performs so well in strong wind in capable hands. They really need to use the original main sail I'm still using, it wasn't much use on the original boat because they had a crap Gnav, but now it's got a Selden boom with the correct Gnav it works really well. Fantastic light wind performance yet depowers in stronger wind, maybe the designer might read this and take note, not that he ever takes much note of anything I blather on about or they wouldn't still have the silly cloth enclosed chute delivery system behind the forstay.
Edited by G.R.F. - 25 Aug 11 at 8:34am |
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Alto-Tim
Newbie Joined: 23 Jun 11 Location: United Kingdom Online Status: Offline Posts: 6 |
Post Options Quote Reply Posted: 25 Aug 11 at 4:51pm | |
Ah, think I get it now this is an Alto rig
right? The Mk2 Sail? ·
Yes you are right there, I think it's all in
the name.(Alto-tim) ·
We have a standard set of sails for the Alto
which works well in all wind conditions. My thinking of 2-1
was the combination of a pulley at the head and the foot as mine has. ·
????? The Alto is underpowered,
at least the 2nd generations were imv, it also badly needs a mast head kite and
a proper jib. ·
Underpowered??, We have
raced our Alto for a couple of years now. Depending what type of beer is for
sale, we are 30/31 stone and the boat goes well in all wind conditions. ·
Having sailed a 59er for
five years we found it underpowered., considering the 59er was built for heavy
crews. ·
And the mast head kite does not suit most of
the courses sailed at clubs and definitely not any river sailing especially
when the tide is out, nowhere to go deep,(and we broke two masts - no not in the mud (in a F3). The Solution would be for
it to use a B14 rig, again imv. ·
Don't know enough about the
B 14 to comment. But the design criterion
was for it to be used by skilled helms and semi to unskilled crews and it was
originally going to be a hiker, which is why it performs so well in strong wind
in capable hands. ·
I think you'll find that
the hiking idea was very soon discarded in the very early days of the
development. ·
We have had loads of people
test the Alto at different skill levels from novice to competent and found it a
well-balanced well-behaved racing dinghy. ·
I think any boat goes well
in strong winds as long as you can keep it up and pointed in the right
direction. They really need to use the
original main sail I'm still using, it wasn't much use on the original boat
because they had a crap Gnav, but now it's got a ·
I think the designer is
open to very sensible ideas and is not blinkered, we have worked with Mike for
two years. ·
I think the front foredeck
cover works well, covers up the
spinnaker, pleasing to the eye, practical plus economic . This discussion came about
over a couple of beers, about controlling masts bend and main creeping down. Although my name is Alto
Tim I hope coming on this forum doesn't mean to say I have to be talking about
the Alto. I do keep looking outside the box only to find the Alto is the best
well-behaved racing dinghy I've ever sailed. |
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RS400atC
Really should get out more Joined: 04 Dec 08 Online Status: Offline Posts: 3011 |
Post Options Quote Reply Posted: 25 Aug 11 at 6:17pm | |
In RS400's a 2:1 is favoured.
It's normal to pre-tension the halyard as much as possible, so that the shackle stays right at the top of the mast, even with a fair amount of downhaul and leech tension. Until the leech and luff tensions exceed twice the preload, the head does not drop at all, even if the mast bend shortens the path the halyard takes inside the mast. In this case, a bit of stretch in the rope is actually good! Even using a kevlar 1:1 halyard, the sail drops significantly as the load comes on. The kevlar halyards tend to be a bit un reliable, 2:1's fail eventually too, due to chafe unless you cut a bit off every few months. It pays to be careful rounding off all sharp edges at the masthead, and make sure the shackle goes on the sail the right way round. If the shackle capsizes, the halyard running around the pin can undo it! |
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oldarn
Far too distracted from work Joined: 10 Apr 07 Online Status: Offline Posts: 440 |
Post Options Quote Reply Posted: 25 Aug 11 at 8:41pm | |
On your <original,AltO you have a Superspar mast with a normal 1 to1 system, and I assume a three year old main halliard. Whether kevlar (most likely) or other I guess it was chaffed. I would stick with a 1 to 1 8platt pre-strethed terrylene and put up with some stretch on the first few outings. Much cheaper and at least the cleat is holding the whole halliard and not just the outer surface. |
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thefastexcitingrunningasymmetric
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RS400atC
Really should get out more Joined: 04 Dec 08 Online Status: Offline Posts: 3011 |
Post Options Quote Reply Posted: 25 Aug 11 at 10:09pm | |
That will stretch a few cm. May not matter in the Alto, except of course if your head is within a few cm of where you expect the boom to be! You could always use good old wire. The trouble with stretchy halyards is that pulling on the mainsheet or kicker effectively loses luff tension, like letting off the cunningham. So you pull on more cunningham to counter it, then you have too much, possibly even damage, when you dump the main or kicker at the windward mark. If money is tight or you want to use what's on hand, you can always splice a cheap tail into a mast-length of dyneema, this can even save a bit of weight. Also stretchy rope can chafe more, because it moves across the wear points more. |
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JimC
Really should get out more Joined: 17 May 04 Location: United Kingdom Online Status: Offline Posts: 6649 |
Post Options Quote Reply Posted: 28 Aug 11 at 6:25pm | |
Conducted a little experiment today... My Canoe mast is a much lighter section than most, and although it is beefed up more than the standard tube I've still been suffering with the leech opening up too early no matter how much kicker I use. I've been mulling over beefing it up some more, but this morning I simply lashed the sail to the top of the mast to see what happened. I have to admit I am gobsmacked by how much difference it made: I estimate I could get my 15 stone of lard out another 8 inches out along the plank. So I suppose I am going to have to sit down and design a halyard lock of some description.
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ham4sand
Far too distracted from work Joined: 27 Jul 09 Location: United Kingdom Online Status: Offline Posts: 452 |
Post Options Quote Reply Posted: 28 Aug 11 at 10:52pm | |
always nice when something discussed is showed to help!
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John Hamilton
cherub 2645 - cheese before bedtime cherub 3209 - anatidaephobia laser 176847 - kiss this |
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Jack Sparrow
Really should get out more Joined: 08 Feb 05 Location: United Kingdom Online Status: Offline Posts: 2965 |
Post Options Quote Reply Posted: 28 Aug 11 at 11:06pm | |
Jim, have a look here: Blog link this is what I have on my Farr 3.7 and it works a dream, with none of the safety issues of mast top lashing I / we used to do on the Cherubs. Edited by Jack Sparrow - 28 Aug 11 at 11:08pm |
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