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Why Rake the Mast on the 4.3


shy thunder
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First off thanks to catsailor.net for offering maricatters their own column.

Why rake the mast back?

To the novices there are a couple of reasons,

1. Helps with pointing ability. Why?

Helps the hulls produce lift to weather that assists the boats pointing ability. MAybe other reasons that some one else knows about?

2.Helps prevent nosediving when pushing to the limit downwind . How? By moving the centre of effort back and produces upward lift to also assist.anyone else with an idea?

3.Best of all makes the boat look fast so as to scare those without rake? lol.

examples: Prima Facie = over the back beam!

Wayne weighs approx 82kgs runs an Adams sail.

Sweet Sixteen = approx 30cm in front of rear beam. John Merle weighs a bit more maybe 88kgs (come on john tell us the truth?)only kidding but he used a new Flower Sail at states.

Cygnet = about 40cm approx in front of rear beam, Lachlan is below weight and has to carry weights on the boat to make up the min skippers weight sailing cat rigged, he usesd his sloop cut mainsail which is ok for his light weight and allowed him to outpoint all in the light weather.

hope this helpful to all who want to go faster.

cheers

d

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just thought of the most important reason why we rake back...

this is so the leach of the main can open under the power of a gust and provide a burst of acceleration instead of overpowering the boat...

how?

opinion is that: the angle that the shrouds attach to the mast allow a larger purchase to bend the mast helping to loosen the leech, not much but more than a boat that has no rake where the shrouds are more parallel to the mast and try to pull it through the front beam.........

anyone else for reason?

cheers

d

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  • 3 weeks later...

John

Nice light boat weight. Is it one of the original 14 footers or is it a 4.3? I am told by the old Maricaters that the original 14 footers were light and fast. Unfortunately the locals here had broken them all before I joined the fleet in 1978.

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Pete,

Yes, my boat is an original 14. It is number 16 out of the factory, hence the name Sweet16. It is solid with no cracks in the hulls and no leaks. I bought it for $400 just prior to the State titles last year at Lake Munmorah. Since breaking the front beam there, have replaced almost everything on it including the original rudders. I have also fitted the Mark 2 style rear beam. The boat seems quite quick. Previously I raced a mark one (sail number 1828) which I bought new some time back. Have not yet owned a mark 2 but am considering to try one.

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I have not seen one of the originals. How different are they in shape?

My poor Maricat is a mass of hairline cracks - particularly where I sit on the deck. No serious ones under the front beam as yet. Some of the sloops down here have huge cracks under both beams but keep on sailing. These old boats are quite amazing.

For some reason the clubs that race cats here often have quite a large shore break. I don't think you guys have this problem as I gather many of you sail on the coastal "lakes". Over the years I have had a couple of ripper crashes trying to get off the beach.

John you will need to increase your body weight to get an invite to the Maricat worlds. I will try to get back to double figures to make myself a bit more competitive.

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The original Maricat 14 is more narrow in the front and less bouyant (nosedives easier). It is also more narrow and curved on the rear deck though the hull here at waterline is not so obviously different.

The side rubbers on the original 14 are not wide enough to put fingers under for lifting the boat, this makes it more awkward to carry.

The join between hull and deck internally is different from the 4.3, glassed together with about a 2inch strip of E glass.

Have not sailed Sweet16 in the surf as yet. Mostly I sail at Mannering Park Sailing club which is quite a protected part of Lake Maquarie (good for the old mari's).

I did sail the mark one (Flashback) in the surf quite often with the only damage from this being a broken rudder. Flashback was a solid boat though and had been ordered from new that way. It was strong enough to pull a waterskier in a blow without any noticable damage to the hulls around the rear beam. Not really sure if I would like to try that with Sweet16.

Gaining a few kilo for a competition should not be so difficult.. the reverse is much harder. I lost 12 kg for the Hobie 14 worlds last year (mostly as I was scared of capsizing the thing backwards). loosing weight is much more difficult that gaining it.

See you at the next Mari worlds smile.gif

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The main advantages for raking the mast are;

a) the potential to nose dive is reduced because the CEO (centre of effort) of the sail is moved aft.

b) the sail presents to the wind differently in as much as the cord length, luff to leach, is increased the further back the top of the mast goes. This essentially makes the sail appear bigger to the air passing over it which increases the efficiency of the sail.

As far as I can ascertain these are the only real advantages. They are however quite significant because they allow the boat to be driven harder in heavy conditions, and the VMG (velocity made good) is improved by the added speed from the more efficient sail.

How far to rake it?

This is controlled by the boom end height over the rear beam. You need to be able to fit your mainsheet blocks between the boom and the rear beam and have the sail sheeted on hard with a tight leach. Low profile triple blocks are used fitting into the shortest distance. The sail also needs to as far up the mast as is possible which increases the available space. A newer sail which doesn't have a stretched leach will also help.

One problem with raking the mast is the mast base and mast step come together and tend to lift the pivot pin from the step hole. Both need to be worked, removing metal to allow the pin to sit properly in the mast step particularly when the mast is rotated.

The other problem is the weather helm created by the COE being pushed further aft of the CLR (Centre of Lateral Resistance) of the hull as the top of the mast moves back. This places additional leeway pressure on the rudders and because there is more rudder blade behind the pivot axis than in front, the rudder blade goes out of balance.

The way to fix this is to push the rudder blade forward leaving the pivot axle static which puts more blade area in front of the pivot axis and balances the blade. This is done by removing blade material where the blade contacts the bottom of the rudder case allowing the blade to swing in further under the hull. It's best done in small increments or if too much is removed you can end up with lee helm, not good.

I parked my trailer on a sandy beach (Forster) so I could remove blade material, test sail the boat, remove a bit more, test sail the boat, each time lifting it onto the trailer for the work until I got it the way I wanted it.

The 'pulldown' line needs to tensioned each time to make sure the rudder blade is fully down.

The aim is to leave a very small amount of weather helm to give the tiller some 'feel' and to make the boat 'head up' in the event you fall off the boat.

Bern

[This message has been edited by berny (edited 02 June 2004).]

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CAUTION

When removing metal from the mast step please be aware it is not a solid moulding!!!!!!!!

The casting has hollows within the "horns" of the step and notches.

If you are not careful you will need to replace your mast step and start with a new one again.

If not sure what I am talking about remove step and look underneath for guidance as to how much metal can be removed.

Also I'll let you know Prima Facie has the step done for his radical rake and he has also modified the stops on the mast (thinnner) which allows his mast to over-rotate some more degrees.

I have noticed that my mast with my crew weight(96kgs) in heavy winds twists allowing the top to lay off sideways with a loss of leech tension, this season will see me make a similar mod. to my rotation as well to suit the new mainsail from Adam's.

cheers dave

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I discovered early on that the mast steps were hollow. An angle grinder sure does make a mess of one. Ended up using builders bog (polyester filler)to fill the gaps. I sure use more rotation than you guys. A retro tuning technique from the early 80s. Garry Robinson used a heap in the early 80s and was very quick. My step is cut through to where it is hollow and the mast base ground to about 1cm thick. Unfortunately I am not sure if it is fast or not, but the sail(s) behaves ok. I guess there is about 80 degrees of rotation as against say 50 in the standard form? When Warrior gets his new gear up to speed I may well have to revert back to far less rotation. I would be interested to know how much rotation Wayne Barry is using.

Havent ground down the step to allow more rake (yet) but I wonder if the whole step can be moved slightly on the beam to allow more rake without the problem of binding metals?

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I modified the mast plug by removing the stop altogether and fitted a spanner to my Maricat (illegal) to see how various angles of rotation affected the performance. I went back to the standard 45deg. because this was definitely fastest.

I also modified the beam step by removing it and thinning the flange from the bottom at the back. I think I was also able to move it aft a tad but I'm not sure just how I did this.

All these things are helpful but your biggest advantage will come from speed smarts such as being able to sail the boat to windward by the seat of your pants, being able to feel the correct angle to the wind for the best VMG (a burgee or compass is helpful for this), and knowing if and when to tack on a shift and knowing which side of the course is advantaged, and if you don't get a good start you're struggling from the get go.

Bern

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Guest The Walrus

Taking into account my rather small knowledge of the physics of sailing, I'd still like to put in my 2 cents and say that raking the mast really makes a huge difference. I took mine to the water after raking back to about 20cm forward of the back beam, filing back the step and cutting 20cm off the clew and rounding the foot. Even without changing the rudders I noticed a huge difference in speed and pointing ability on a work.

Took my rudders off 3 weeks ago to smooth them out and adjust them to the rake, but found they had expanded around the drill holes because they hadn't been sealed properly. Explains why I was having difficulties getting them down, so now I've got a bit of work fixing them up.

Thanks for the warning on steps being hollow, but I'm curious as to how much advantage you get out of increasing the rotation. It would help on runs and reaches, but doesn't it make a bad angle for when you're working?

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but I'm curious as to how much advantage you get out of increasing the rotation. It would help on runs and reaches, but doesn't it make a bad angle for when you're working?

Had you read the previous post above you'd have some insight into the answers you want!

You are right in that, 'increasing' rotation generally aids off wind performance and can be counterproductive to up wind performance. Many gains can be made on the wind so inhibiting beating ability in any way is not good.

The Mari mast is a 'tear drop' section not a wing, and becomes only marginally more efficient with rotation. However, as the mast rotates it's tendency to bend 'across' it's vertical axis over it's entire length is increased with main sheet tension. This is because it has no diamond stays. Bending the mast changes the sail shape, flattening it significantly. The more mainsheet tension that is applied, the more the mast bends, and the more it changes the shape of the sail, making correct sheet tension critical.

This taken to extremes can do horrible things the sail shape so as I said previously, after a significant amount of testing with spanner controlled mast rotation, my conclusions were, that the standard rotation works best on most angles of sailing, and no significant advantage was evident with increased rotation.

Bern

[This message has been edited by berny (edited 06 June 2004).]

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  • 3 months later...

I was just wanting to join this conversation as a newbie myself. I have a nacra 16sq and don't know if this makes a difference or not.

As a learner i have found that raking the mast may not be such a good thing for a couple of reasons... One thing i have found is that it gives me more weather helm which is not such a good thing to have when learning to tack and getting stuck in irons while almost getting swept out the river mouth....next is that downwind speed is increased which is the last thing i want sometimes..especially after staying out too long while the wind picks up and you are trying to come back to port with boats on one side and a jetty on the other.....makes for a very fast landing and you can almost get to the trailer... my pick would be to leave the stays at an even keel and work from there and leave the fine tuning to these other masters or when you are confident in your own abilities in all conditions

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YES WEATHER HELM IS PRODUCED.

This is what helps with upwind pointing ability, not too much in a centreboard boat but is desiraeable.....

to counteract this you need to negate the weather helm effects , in the mari's we undercut the rudder blade to balance the blade but the w'helm is still there....

read the other posts re getting rid of helm "pull"

cheers d

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