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Nacra 5.8 spreaders


HooD
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Recently I noticed our forward spreader arms have split, and I think the tubing has jumped over the thread. I have very little idea where they would have started originally. I anyone could give me a good starting place in terms of rake and diamond tension, I would be grateful.

p.s. we are a fairly heavy crew.

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we have ours at 30mm if you place a straight edge across the wires at the spreader arms and measure the distance to the saile track.

We have our diamonds tight in all conditions but no prebend.

Loose in fresh to frightning conditions.

P.S. Do not mess around with not replacing damaged wires/spreader arms - they are a lot cheaper to replace than a NEW MAST !!!

[This message has been edited by Andrew Holden (edited 20 June 2002).]

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Thanks Andrew!, I just measured them now, they are 70mm behind the track, but not for long smile.gif as soon as I recieve the new one's, I'll adjust them smile.gif BTW our next winter series race is in 2 1/2 weeks, hint hint smile.gif altho if it is anything like last weeks race, I think I'll stay at home, it rained most of the day, and no wind, took an hour to get over the start line.

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Thanks Goose, My email is darren@lyccat.net, and yeah we are around 200kilo crew total, and yes we are on a diet of exercise and low food intake.. I can live with the exercise, but the dieting isnt much fun...

edit:

I do have access to a gauge, and my diamond adjusters are marked, so i can find my way back to any spot.

[This message has been edited by HooD (edited 20 June 2002).]

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  • 3 weeks later...

After todays sailing I thought I had better give some feedback.

Firstly I would like to thank catsailor.net for supplying me the parts to repair my spreaders in time for todays race.

we setup the rake of the spreaders to 30mm behind the track, and used a loos gauge to set the tension to 35, which was a lot more than was previously being used. with a lot of effort I can push on the wire and touch the mast about 18inches up the mast.

Todays conditions were 5-30knots with quite noticable 30 degree windshifts (talk about kept on your toes).

In the light to medium stuff, the boat was well powered up, and was a definite improvement. In the stronger gusts, the boat wanted to stall, and not accelerate. is this because the diamonds are too tight?

The other odd thing, was the lower mast wanted to bend back towards the rear of the mast, closing the slot between the main and the jib, the only thing i can think of to fix it, is give the spreaders more rake, or use more outhaul to reduce mast rotation. any ideas?

and for those interested, it was a beutiful day in Hobart today, sunny, 10 degrees, and the water was about 5 degrees, Ideal catsailing conditions! (why do i do it).

Lauderdale Yacht Club

www.lyccat.net

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Hey Hood !

smile.gif

great to see this forum being used for what it was created for ! smile.gif

In short you seem to have the boat set up fairly well for average winds obviously you can't set a boat up and hope it will perform in 5k as well as 30k... it just wont happen !

By backing off the diamond tension you allow the mast to bend more, this in turn flattens the sail because of the way the sail is cut along the bolt rope(ie- it is curved) and as we all know a flat sail= fast, fast to exhaust.

a fast exhausting, flat sail is what you need in strong wind and obviously a more "bagged" sail in light conditions.

Also if you have wind upward of say 25k you will benefit from over rotating which will allow the mast to bend more as well and flatten your sail.

Hope this helps ?

Cheers matey smile.gif

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Thanks for the tips coolJ, I think that with this forum, and Goose's help we have shaved about 2 years off our learning curve smile.gif.

The power of the internet can be a real help, In the past we would not have had access to to the good sailors in australia, and for that matter over seas.

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  • 1 month later...

Hi Coolj,

I was under the impression that in heavy air you wanted MORE prebend in the mast and thus obtain a flatter sail, but your post seems to indicate otherwise.

Dave

N6.0NA

Canada

Originally posted by coolj:

Hey Hood !

smile.gif

great to see this forum being used for what it was created for ! smile.gif

In short you seem to have the boat set up fairly well for average winds obviously you can't set a boat up and hope it will perform in 5k as well as 30k... it just wont happen !

By backing off the diamond tension you allow the mast to bend more, this in turn flattens the sail because of the way the sail is cut along the bolt rope(ie- it is curved) and as we all know a flat sail= fast, fast to exhaust.

a fast exhausting, flat sail is what you need in strong wind and obviously a more "bagged" sail in light conditions.

Also if you have wind upward of say 25k you will benefit from over rotating which will allow the mast to bend more as well and flatten your sail.

Hope this helps ?

Cheers matey smile.gif

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  • 1 month later...

Don't confuse "Pre-bend" with allowing the mast to bend, pre bend is achieved by tightening the diamonds so that the "fore & aft" bend is present before any other pressure is exerted on the mast.

There seems to be two quite differing schools of thought on this subject, those that subscribe to the pre-bend philosophy and those that believe in allowing the mast to bend school of thought.

Firstly let me say that BOTH ways work !!

having said that if you crank up yur pre-bend by tightening yur diamonds, then when yur on the water try pulling on yur downhaul, you don't get the same amount of downhaul because the diamonds are dead tight.

Also because when going to windward the mast bends OUT of "Collumn" and tightening the diamonds for pre bend only caters for "Fore & Aft" thus not allowing for the out of collumn bending.

and just quickly, rake on spreaders will accentuate what you are trying to achieve with yur diamonds, ie- if you have more rake and moderatly loose diamonds, yur mast will bend earlier than if you had less rake.

I could go on all day smile.gif

cheers

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  • 4 months later...

I just replaced my diamond wires. What is the definition of tight and loose in practical terms? How do know when they are at the desired tension. I can pull the wires on and off the spreaders by hand with a fair bit effort. Is this considered tight or loose.

I have about 60mm of rake with seized spreader arms.

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Rake should be 30-40mm, more rake with a lighter crew, say 30mm for 170+kilos 40mm for 160 down. if you can borrow a loos gauge, somewhere around 35 would be good, otherwise i can make my diamond wire touch about 18inches up the mast (from the bottom of the spreader wires), with a fair bit of effort.

important saftey tip: wire the spreader wires to the tip of the spreaders, when your going to windward, those wires flap in the breeze, if the drop out, you can kiss your mast goodbye.

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It will only affect performance, mine were @ 75mm for the first 6 months I had the boat, I didnt know any better, as where I sail there are no other 5.8's frown.gif just kick ass A-class's and a taipan 4.9.

The result will be a flatter main, that will go pretty good in a breeze, but be a little under powered in the middle stuff. If/when you get serious about racing it, you might want to soak the arms in WD40. I had to buy a new set a while back, I think they were about $100, so its not the end of the world.

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