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The formula to height

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ClubRacer View Drop Down
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Post Options Post Options   Quote ClubRacer Quote  Post ReplyReply Direct Link To This Post Posted: 29 Aug 18 at 5:36pm
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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Post Options Post Options   Quote Oatsandbeans Quote  Post ReplyReply Direct Link To This Post 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 View Drop Down
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Post Options Post Options   Quote davidyacht Quote  Post ReplyReply Direct Link To This Post 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 Post Options   Quote mozzy Quote  Post ReplyReply Direct Link To This Post Posted: 29 Aug 18 at 7:24pm
Originally posted by ClubRacer

Kicker, Moves the COE back but holds a tight leech when you need to sheet out, surely this is a big height killer too
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. 


Originally posted by ClubRacer

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 
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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Post Options Post Options   Quote zippyRN Quote  Post ReplyReply Direct Link To This Post Posted: 30 Aug 18 at 12:01am
Originally posted by davidyacht

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.  

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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Post Options Post Options   Quote Fatboi Quote  Post ReplyReply Direct Link To This Post Posted: 30 Aug 18 at 8:30am
Originally posted by ClubRacer

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
This is incorrect. Tightening the Jib luff will do a few things though.
1) tighten the luff and it moves the draft right forward, this can give you a bigger 'groove' to steer in when windy. If you have a loose luff the entry to the jib is much finer and you will be able to get closer to the wind. 
2)Tighter luff will also close the leech more as it stretches the jib upwards and pulls the leech tight. 

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?
Generally you will want to match the leech shape of the jib to that of the main and have the slot profile matching. If you have it set like this you will be good for most of the beat and get the hull and foils working in tandem, however there are situations where you would sacrifice speed for height over a very small period of time - say pinching for a mark  for 3-4 boatlengths where you may benefit from pinching as opposed to two tacks.

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?
Depowers the boat and makes it easier to sail. In big wind, you often struggle to get the bow down and go fast as by being overpowered it forces pinching to lose power and you point high, but slide sideways as the foils are not working efficiently. 

Kicker, Moves the COE back but holds a tight leech when you need to sheet out, surely this is a big height killer too
Actually no. The kicker holds the leech firm and if you eased the main without it on, then your boom would rise and your leech would open. This would spill power and the height. 
With mainsail shape you want return on your leech when trying to sail in a high mode and point well.
You need to be careful though. Too much kicker means mast bend and a flatter sail, which wont help pointing either. 

Downhaul, Moves the COE Foward in exchange for messing with the entry to the sail. Also opens the leech at the top. 
Yes, only want this when depowering. Often the last control to be pulled on. 


So for maximum pointing ability you want;

up right rig so neutral helm
If you have a bit of weather helm it will mean that you can feel the pulling on the rudder and sail the boat flat but still have some feeling on the rudder. Often people set the boat up with no helm, but then heel the boat to get feel - so many things wrong with that!! 
jib on hard with tight foot and near tight leech
Would make a flat jib - might be good for flat water if you have lots of power, but if you are struggling for power you will need a bit of depth in the jib to drive the boat. If the leech is too tight, then it will backwind the main and close the slot - def not ideal! 
jib luff tension just taking the slack so as to clean the entry to the sail up
Spot on
No kicker but mainsheet tension on hard but not so hard it hooks the top leech
Depends on conditions. If lighter wind and you do not have to ease main to depower then spot on. 
When easing main to depower - start to kicker
No downhaul- possibly to take the creases out the sail out and tidy the entry?
Spot on - even some creases are fine



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ClubRacer View Drop Down
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Post Options Post Options   Quote ClubRacer Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Quote Do Different Quote  Post ReplyReply Direct Link To This Post 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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