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tuning a Nacra14sq


tonyquoll
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G'day,

This query is on behalf of my Dad, Richard, who races a Nacra 14 square at Fitzroy Falls, NSW. I've tried sailing it on my own and with Dad, but couldn't resolve the tuning issues.

How do you get the mast to bend? Most of the time the sail is too full and tell-tales stalled along the leech. Cranking on the downhaul helped, but I was worried I'd rip the foot off the sail before it got into shape.

How do you stop weather helm? The rudders rake back a little bit, so there is quite a firm pull on the tiller extension. Centreboards fill the slots, so no room for rake there. The mast is already quite vertical, seemingly more upright than other 14 squares we've seen.

My suggestion would be to first tweak the rudder blades to be more vertical, then look at replacing the centreboards with narrower ones that allow more rake. Is that within the class rules?

I'll email Dad a link to this thread, so he can access it. For some reason the menu pages produce a "server not responding" error on his computer. Any fixes for that one?

Regards

Tony Hastings

Paper Tiger 2128 "Pelikinetic"

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Have a look at Goosemarine.com.au tuning guide for the 16sq. I would assume the boats would be set up reasonable similar or though I have never sailed a 14.

Rudders are usually set up with around 20-30mm forward rake on most nacras (16's and 5.8's) Setting up the rudders properly will elimanate alot of your problems I think.

As far as mast bend some of the nacra guys used to rotate the mast to 90 when going to windward on the 5.8s so the mast would bend. But that would be a huge hassel on a one man boat I would suggest beefing up downhaul and pulling on as much as you need. 16sq use around 10:1 and often get the bottom of the main touching the tramp.

Don't forget to pull you outhaul car forward to flatten your main as wind increases. oh and don't bother touching the centreboards theres no room within the rules to adjust.

Leigh

[This message has been edited by Yachty Boy (edited 01 May 2009).]

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Probably only big difference is the lack of spreaders on the 14sq. I did try the 90' mast rotation trick, but i suffered on pointing ability. Trade offs!!! I found that they do best at somewhere between 30-45' rotation for speed and point combined, mind you that was in around 15knots with 85kgs on board.

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Have a look at a book called Catamaran Racing for the 90's by Rick White.

There is a chapter dedicated to tecking and advice on learning the roll tack.

This is a must on a 14 sq.

The 16 sq is a lot different because of the water line lenth.

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Thets Ok ralph, wuz unterpeting et weth a Kiwi exent.

Thanks for all the great advice and info. Credit to Gary from Goosemarine who has provided great advice & picture by email.

The Forestays are pinned in the 4th hole from the top. This rakes the mast just a few degrees back from vertical.

With the season now over, Dad will have a few months to dwell on all this before returning, faster than ever, to defend his Club Championship. He might even be able to chase down that pesky Paper Tiger at the Regattas!

Tony

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Thanks for that. In discussing this topic Dad & I agree that there are inter-acting variables to play with; rudder rake, mast rake, centreboard depth, sail shape, downhaul, mast rotation & even where the skipper sits/stands.

Sounds like you've hit a good setup there; stick with it. To reduce nose diving on reaches, you could try a fuller sail with more twist, to lower the centre of effort. This could be done by moving the outhaul an inch or so and not pulling the main in so tight.

Good luck with it!

Tony

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Thanks Tony, I had a bit of an issue with rounding up though, so i don't think she was well balanced, but i've only raced her twice. I broke the tie bar between the tillers and had to do half a race without the wire and steering with one tiller!!!! So she kept rounding up into the breeze and laid up in irons twice, I can't tell you how hard it is to steer while you have no momentum. It was like stalling a light aircraft and the controls go all mushy with little or no response, but you all understand why....

So i'll have a go at the 4th hole from the top next weekend and see if the girl is better balanced, it's amazing how different it is at altitude in freshwater.

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Cheers for the reply,

Dad also broke his cross-bar a while ago, and found that it was lighter gauge tube than the factory Nacra item that replaced it. He since resolved to ALWAYS remove the cross-bar and swing it out of the way before putting the mast up or down, as resting the mast on the bar is probably what broke it.

Interesting you mention the fresh/salt water difference; Dad also normally sails on fresh water & has only had weather helm issues on salt, which we attributed to the increased wind instead. Maybe you're onto something there. We've read how standing further back reduces weather helm, which must vary with the different flotation.

It might not be relevant to the Nacra, but on my Paper Tiger I've found it fastest to reduce weather helm and related drag, rather than try to gain pointing ability by driving the rudders hard.

By the way I lived in Kuranda, Cairns, Gordonvale and Walsh River from '92 to '98 and miss the place heaps. You're a lucky man!

best wishes, Tony.

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  • 2 weeks later...

We had light and variable winds on Tinaroo on Sunday. every time i chased a gust, i ended up getting screwed by a taser. Those guys know that lake backwards. wind was shifting up to 90' on occasions. Thought you'd make the mark, easily make the mark to not a hope in hell. Easily the worst conditions that i've ever experienced and the most frustrated i've ever been on a boat, ever.

Today the breeze kicked in ..#*@$#%!!!!!!

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  • 2 weeks later...

Thanks for your suggestions on tuning my Nacra. I am having computer

problems, I can open every site on the web except Catsailor, which is why I

am having to communicate through Tony.

Sailing in light winds, my Nacra performs as it should, and is well balanced

and much faster than any 14ft cat. So sailing at Fitzroy Falls Reservoir,

where winds are predominately light, I finish the races well ahead of

anybody else. But when I travel to a regatta on the coast, and the wind gets

over about 15 knots, the boat develops a huge amount of weather helm, so

that I have to haul on the tiller and the boat is very slow: I cannot even

keep up with Maricats.

It seems that tipping the bottom of the rudders forward is essential, and I

will do that over winter. I don't understand the theory of this, but as it

seems to work I will do it. Once I have done that I will rake the mast back,

pull on heaps and heaps of downhaul, let the traveller out a bit, and see

how I go.

Sailing in very light winds is difficult for any cat. I have found that even

in drifters the Nacra is faster in a straight line than a monohull, but when

a mono tacks it gains speed, which the Nacra certainly doesn't! So I watch

my wind indicator very carefully to keep the boat going in a straight line

as fast as possible, and let the monos go off chasing the gusts. I usually

still manage first across the line, but they kill me on handicap.

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interesting - rudder balance vs weather helm. They say that the rudder should be about 10% balanced (meaning for most that the front of the blade is forward of the pivot). That balances it, then you can tell if you have weather helm or not and that's about rig trim.

The Maricats have heavily balanced rudders, mine has a second pivot hole. This makes steering light but you can still detect weather helm if you rake the rig back too far.

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Thanks Toccata, I tried to steer as straight as possible, but when you were going well, then are pointing straight into the breeze without altering course, it can be difficult to hold your line. The tasers seem to hold thier own with me, but it is the first season skippering a Nacra.

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  • 3 weeks later...

Originally posted by cruiser:

Well, I'm still cruisin, I've had my mast at 90' rotation, and she seems to be really well powered, but it seems that less rotation will give me better pointing ability.

Which is the lesser of 2 wevils?

The lesser of the two wevils (weevils?) is to pick the one that gets you to where you want to go the fastest. Unless you are really, I mean really close to the mark then pointing is NOT the way to go.

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Thanks mate, I'm having trouble beating the state taser champs for line honours in lighter breezes, so I'll chase the sweet spot and try and balance the 2.

once we get over 15 knots, and i can get out on trap, they're busted, below 15 and i'm really struggling. Doesn't seem right with Nacra 14sq @ 84.5 and a taser @ 107.5???

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Don't feel bad about keeping pace with monohulls in light winds; happens to all of us. In very light winds at the Twofold Bay Regatta I chased 2 mosquitos, who have similar yardstick to the 14square, while Flying 15s & MGs kept up.

Once the wind came in at 15 knots, my Paper Tiger flew past everyone, all over the course, except the Mosquitos who were in a league of their own. Amazing to watch; hull flying, almost no wake, awesome speed.

On mast rotation, advice I've heard for the 14square is just let it do it's own thing & freely rotate upwind. On the PaperTiger upwind, the mast is rotated so that the track points at the leeward transom. This help reduces turbulence as the wind flows onto the sail.

Good luck!

Tony

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