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The formula to height |
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ClubRacer
Far too distracted from work Joined: 26 Sep 15 Online Status: Offline Posts: 210 |
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Topic: The formula to height Posted: 29 Aug 18 at 5:36pm |
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correct me if I'm wrong here but my belief was
Jib luff tension (not rig tension) - would kill height by messing with the entry to the sail but open the leech of the jib. This when windy would help the slot and balance of the boat when the kicker moves the COE aft Jib Leech tension (non boat specific, for example if you had a meter long jib car track you could go from a really tight foot to and next to no leech tension to tight leech no foot)- This is the one I'm struggling with, leech tension helps with the ability to point higher. But on the jib the leech has a second function to accelerate wind over the back side of the main, so would a tight leech disrupt this flow and kill your height more than you've gained? Mast rake- this opens the leeches of the main and jib and moves the COE back. All i can see is this is a massive height killer, what is the purpose of raking the mast back as it gets windier? Kicker, Moves the COE back but holds a tight leech when you need to sheet out, surely this is a big height killer too Downhaul, Moves the COE Foward in exchange for messing with the entry to the sail. Also opens the leech at the top. So for maximum pointing ability you want; up right rig so neutral helm jib on hard with tight foot and near tight leech jib luff tension just taking the slack so as to clean the entry to the sail up No kicker but mainsheet tension on hard but not so hard it hooks the top leech No downhaul- possibly to take the creases out the sail out and tidy the entry? In terms of spreaders i presume; More length = stiffer mast, meaning you can point higher More deflection= more pre-bend which would open the leech and kill height Obviously with spreaders too much or too little can break the mast so this is theoretical only
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Oatsandbeans
Far too distracted from work Joined: 19 Sep 05 Location: United Kingdom Online Status: Offline Posts: 382 |
Post Options Quote Reply Posted: 29 Aug 18 at 6:06pm | |
On this one most sailors will have their own idea on how to get that extra height.
Here's mine-95% of what has beeen said alreday I would agree can be used to give you better pointing but ther is one thing that has not been mentioned- sail depth. It is simple -for lots of reasons flat sails will point higher than full sails. Why do you see so many sails with different fullnesses around if flat sails are so good? Its because they are awful to sail with. They have no feel, no acceleration, power, and are completely gutless. The thing is that if you sail with them a lot you learn to manage these "problems" so they are not too much of an issue as you are pointing higher than the rest and you can rely on this as your "get out of jail card " on the racecourse. Bethwaite knew about this -have a look at his 29er sails compared to other similar dinghies-not much shape there at all! |
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davidyacht
Really should get out more Joined: 29 Mar 05 Online Status: Offline Posts: 1345 |
Post Options Quote Reply Posted: 29 Aug 18 at 6:07pm | |
I was told by someone much better than me, that some weather helm is good, since it generates lift from the rudder, therefore some of your list like rake, induce weather helm, which then induces lift.
I would suggest that a National 12 May be the ultimate pointing boat, and I think the key differences with the rig to many other boats is a very narrow sheeting angle and a very controllable mainsail leech.
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Post Options Quote Reply Posted: 29 Aug 18 at 7:24pm | |
Kicker flattens the sail. Coupled with moving the max depth back it creates a much tighter angle of attack. Kicker is good for pointing IMO.
More pre-bend would open the leech, but nothing that can't be shut back down with shorter strops and main tension. But pre-bend will set up a flatter sail, and a flatter sail has a narrower angle of attack. But like I said, most of these things move the draft further back, which aids pointing, but harms the efficiency of the sail, and can choke the slot, which kills VMG. I point best with a fairly neutral sail set up, with a nice progressive curve, then build speed and feather for height.
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zippyRN
Far too distracted from work Joined: 14 Sep 06 Online Status: Offline Posts: 437 |
Post Options Quote Reply Posted: 30 Aug 18 at 12:01am | |
however the near vertical bow and fine entry of the National 12 ( and also the Merlin Rocket ) help with that as well
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Fatboi
Posting king Joined: 09 Aug 16 Location: Hampshire Online Status: Offline Posts: 189 |
Post Options Quote Reply Posted: 30 Aug 18 at 8:30am | |
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ClubRacer
Far too distracted from work Joined: 26 Sep 15 Online Status: Offline Posts: 210 |
Post Options Quote Reply Posted: 17 Oct 18 at 8:43pm | |
Have had a reasonable amount of weather-helm for a long time but had the rig setup as per the guides etc so decided to do some on the water tuning this weekend
We raked the mast forward bit by bit until it slowly removed the weather-helm and did a race like it I found the entry to the jib seemed to be a lot more flat but couldn't get my head around how. By raking forward you move the jib sheet tension more towards leech tension which would surely make the jib fuller? What ever I did it seemed to help as i was able to point a lot higher than everyone else and the boat felt like it was in a nice groove. Although now i think about it, it may have been more to do with getting my bow above the tide. It also meant the mast rake was nearly 100mm more than the average of the class tuning guides but the rudder still didn't feel like I was used to in the 200. Could this be more to do with rudder rake? I remember I broke mine a few years ago at an open and borrowed someones new style rudder which felt completely different, so am debating re-drilling mine so its raked more forward. What is the correct position for the rudder to be raked at? My best guess would be a line from the top pintle to the bottom gudgeon extended, this line would be parallel to the trailing edge of the rudder or at least a little more raked forward |
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Sam.Spoons
Really should get out more Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3398 |
Post Options Quote Reply Posted: 17 Oct 18 at 9:25pm | |
Parallel to the leading edge of the rudder surely? You definitely don't want the leading edge raked forward of vertical, that gives a very light rudder but little feel.
From an earlier 'Club Racer' post :- "Mast rake- this opens the leeches of the main and jib and moves the COE back. All i can see is this is a massive height killer, what is the purpose of raking the mast back as it gets windier?" I don't get this, raking the mast has no effect on mainsail leech tension (and I can't see how it affects jib leech tension but less sure about this one). Agreed that it moves CoE back. Edited by Sam.Spoons - 17 Oct 18 at 9:26pm |
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Do Different
Really should get out more Joined: 26 Jan 12 Location: North Online Status: Offline Posts: 1312 |
Post Options Quote Reply Posted: 21 Oct 18 at 7:00am | |
It is all so multi factored and different for every boat. Whatever you state someone will be able to find a situation that contradicts it.
Raking the mast back in wind demonstrably makes boats easier to sail and therefore faster for probably most classes but maybe for subtly different reasons. Pointing the boat high is not the only or always the best way to get to the windward mark first. Think VMG and also remember that the boat doesn't necessarily go exactly in the direction it is pointing.
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