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soul searcher 03-29-2007 05:27 PM

rig tuning and weather helm
 
I need a little advice on rig tuning.
I recently tried to just take the slop ot of my standing rigging an didn't do a very good job of it and got the mast a little S shaped. wich after a lot of cursing I finally got back straight. But still wanted to know that the rig was all properly tensioned and the mast was were it was supposed to be in relation to the boat.
I loosened all the rigging and started from scratch cheked rake foud center
and tightend it down with equal tension keeping the mast in collum.
We went for a short sail yesterday and the boat performed a lot better than it did before a lot less weather helm and faster.
but Here is the problem on the starboard tack close hauled in 10knts app I could balance the boat to zero weather helm(or close to it). same wind speed and point of sail on the port tack The best balance I could get left me with about Five degrees of rudder(which I like better).
So what did I do wrong:confused: Did I not find dead center with the mast head? that is realy the only part of the set up I'm skeptical about.

Here are the paticulars, Single spreader mast, single forestay(tacked with stay sail on and off no difference.)split back stayes at the mast head, forward and aft lowers and fixed running backstays. modified fin keel and skeg hung rudder.

What do you think?

Thank you
Matt

Giulietta 03-29-2007 05:36 PM

Assuming your mast is equally balanced and correctly set from Stbd to port, right now what I can come up with:

a)Keel is not centered
b)boat has more weight to one side than other
c)rudder is not correctly marked or centered, giving you false zero
d)you're too picky!!!
e) all the above

This assuming the traveller was centered.

soul searcher 03-29-2007 05:54 PM

Quote:

you're too picky!!!
I Can't Help It.:o I like symmetry:)

Cant move the keel:mad: :D
rudder is straight :D
Boat is heavier on one side but thought it was the other side:rolleyes:
Guess I'll sail it for a while as is:cool:

Hey Gui just out of curiosity I know you have the jack up mast how much tension are you useing when you cruise and when you race?

Matt

Giulietta 03-29-2007 07:31 PM

MAtt, I use a Loos metric gauge for tensioning my shrouds, my Mark I eyeball, and model 3a seat of the pants.

When I adjust shrouds, step 1, I want around 1000kg (2000lb) force on the shrouds, (the stay is furling so not accounted here, but around 20% of cable breaking load), to start with when setting the mast in “neutral”. This is calculated in function of shroud breaking strength. Which in my case is almost 10 000Kg (20000lb). So I use 10% for shrouds and 20% for stay.

Setting the tension is a dynamic thing, normally I like the maximal tension possible (except downwind) the limit is breaking point of attachments, etc. when the wind is high (above 18 to 20kts), and loose rigging when bellow 15 kts.

Tension depends on the sailing you will be doing, we want loose rigging in low winds and tight in higher winds.

Since the stay is fractional, and I don’t have a diamond mast top, and if I see the bend is too much, I reduce stay tension, but this is also affected by backstay, so be carefull

Normally I like a tension that keeps the leeward shrouds slightly tensioned, not too loose, I don’t like them flapping when not tensioned due to wind power on sails, so I adjust jack accordingly.

The intermediate shrouds are more complicated to tune, because you need to climb the mast, so normally I use 20% breaking point as a start. And that is done as the wind changes, only adjusted when racing, we send a monkey up the mast to adjust.

So when sailing, the more rake makes the boat weather helm more when upwind, and because I need all help at low winds, to power the boat, I want maximal rake, of course now the boat has more weather helm, but steers better.

Please note this, my mast has 2 levels of spreaders, so the low shrouds I can control tension in middle of mast, and some lower mast bend, not too much because my mast is keel stepped and more ridgid bellow, the high shrouds control stay tension and how much the top of the mast falls to leeward, and the middle shrouds, control the middle of the mast

The back stay controls the bend on top and the tension of the stay.

Generaly if the wind is lower than 15kts, I let the mast down to make less tension, this causes more bend to the mast and more bag to the sail, but also reduces the space between the genoa and the main sail!!! Ehehehe;)

Then as the wind picks up I tension the mast, the number exactly I don’t know..I use my ears and my eyes to feel the boat…and go to the shrouds and feel them, tense with high winds, not so tense in lower winds....its ahrd to tell, but next time, I will measure and let you know, OK?? Promise.

I do mast tension play even when crusing…its fun…Fred already knows how to jack mast!!

But generally its done in function of the wind...

Did I help?

Giulietta 03-29-2007 07:56 PM

Soul,

check also if your stbd and port shrouds have the right tension, if you don't know what it should be pm me I'll tell you.

Different tensions in the shrouds, will cause the mast to "fall" more to one side under load then to the other, affecting rake and affecting weather helm.

chris_gee 03-29-2007 07:57 PM

If one side is heavier than the other the boat will not be horizontal and the mast not vertical depending on whether you adjusted on land or in the water. In any case the underwater boat profile will not be the same on both tacks as you will be heeled different amounts which also alters the wind power and your speed so a 5 degree rudder difference is minimal.

astraeus 03-29-2007 08:57 PM

You may want to check out the tuning video by Brian Toss. Very informative about rig tuning.

Weather helm can also be created by the draft being too far aft in the main sail.

Giulietta 03-29-2007 08:59 PM

Quote:

Originally Posted by astraeus
Weather helm can also be created by the draft being too far aft in the main sail.

Wouldn't it be the same on either tack???:D :D

astraeus 03-29-2007 09:32 PM

Quote:

Originally Posted by Giulietta
Wouldn't it be the same on either tack???:D :D

You caught me :D I'm an AFOC (Ass full of crap), didn't read his entire post.:rolleyes:

soul searcher 03-29-2007 10:08 PM

That helped A lot Gui. Thank you!
the way I set it up is as follows.
Cap shrouds 12%
forward lowers 12%
Aft lowers 10%
Runnig backs 10%
back stays 15%
I set these with a loos guage they are equal side to side.
Ive been thinking and maybe the increas in backstay tension is where the over all reduction in helm came from I pulled alot of the forstay sag out so I
moved the genoa forward a bit. I may need to let off on that a little. I like to feel the rudder and Im not getting that on the starboard tack. I point better though.:D
So if the mast head is to far to port I would reduce helm on the starboard tack. I think its pretty close. how far off would it have to be to loose five degrees of helm?
While sailing I was carefull to sheet in the main and genoa and keep the same apperent wind angle (also thought maybe my windex is off).
every thing was the same boat speeds and angles. or as near as I could make them.
what Im really looking for is just a good all round setting that will give the best performance but not overstress the rig I would prefer reduced performance to be in the light air side than in the heavy air side.

This is a photo looking up the head stay in about 15 knts app.
http://i38.photobucket.com/albums/e1...r/DSCN1525.jpg

I cut this amount of sag in half. ( and the boat she took off:eek: :) :D )
Matt


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