MERLIN ROCKET FORUM

Topic : Spreaders

OK - the last thing I need, I think, is spreader set-up. How do I decide how long to make the spreaders and how much deflection to give them?

~400lb [180kg] crew, on a good day, speedsails main and jib, carbon deck-stepped mast. Wider stiffens the mast laterally [?] and is better for heavier crews [?] is that right? And approx 8" [200mm] deflection?

Yeah, yeah, yeah I know, we should be in the water by now but 95%+ humidity turned quoted 24 hour per coat varnish drying time into 4-5 days per coat! Aiming for week ending 19th June.

Thanks

John in NY
where we have 85+ degree F air temperatures and rising, 55 degree water temps! Its usually late July before water temps become reasonable!


Posted: 06/06/2005 16:57:24
By: John, NY
John

Have a look at batt sails tuning guide. Look for merlin rocket pages and go to tuning guide at bottom of page

http://www.battsails.com/

Posted: 06/06/2005 19:09:23
By: Miles
are you going to take it over here to see if it is competitive?


Posted: 06/06/2005 19:54:38
By: Peter Rhodes
Trouble is the whole thing is relative to the shroud base.  Starting point would be with mast at proper rake for light/moderate winds to have the spreaders deflect the shrouds out by about an inch and pretty neutral fore and aft.  Set the whole thing up.  If there's too much bend angle spreaders forward (& vice-versa).  If you are bending the mast to leeward in the middle when powered up the spreaders are too long & vice-versa

I think...


Posted: 07/06/2005 15:35:07
By: Andrew M
Thanks Andrew and Miles.
The Batt sails stuff goes most of the way. I got an answer off Speed Sails too which tells me my prebend should be 25mm rather than the 30-40mm Batt suggests.
And Andrew, you match what I have just researched and what I got out of Speed Sails reply so i'm going to go with your first answer. This WWW thing has all sorts of info on it!

The Batt sails stuff talks about rig rake also. Now am I getting this right... A heavier or fitter [provided they ain't too skinny] crew requires less rake because they can keep the boat flatter for any given blow?

Once I work out where to put all this string and stuff we can get out on the water!

Having fun with my Rocket in NY

John


Posted: 07/06/2005 19:06:43
By: John, NY
John, if it helps
my Winder Tales with Chipstow carbon, has spreader length 14 inch mast to shroud, and seperation of 27 inches between shrouds. My Who's a Prett Boy (about 1 inch narrow bean than a Winder) has spreader lenght of 14 inch and seperation on 27.5 inches.

MAybe a good starting point for you.


Posted: 07/06/2005 20:45:19
By: Alan
* narrower BEAN!!**
Who's a Prett!! ** can't ytpe!!


Posted: 07/06/2005 20:47:15
By: Alan
Rake is a rig control for depowering, so essentially a heavier crew will not start to rake the rig to depower till it's blowing a bit harder than the light crew.  Your starting point is the same & you don't touch it till you want to shed power on the beat.  See Dan Alsop's article on the website


Posted: 08/06/2005 09:46:28
By: Andrew M
Your spreaders are to control side stiffness of the mast and place controllable for/aft pre-bend into it.
Starting point measurements
dist between tips 700-710 mm
depth 140-150mm (depth is measured using a batten placed on the shrouds and measured from the luff groove to the battern
this is a good datum starting point.


Posted: 08/06/2005 14:28:54
By: Huf n Puf
How much you rake and when depends on how stiff your mast is.Raking a  mast in a blow reduces sail hight and reduces leach tension.(Bad news if you have a soft mast).


Posted: 09/06/2005 22:28:16
By: Broz
All these spreader measurements are fine if all spreaders
are at the same height above shearline & the shrouds are at the same measurement aft of the mast. Also the measurement at shroud to shroud at deck point must be common (one design we are not). Otherwise a safer bet is to look at sideways & aft deflection of the spreader tip and it's relation/effect on the rig you have.
In escence this means seting up your rig with the spreaders unattached to your shrouds, then making appropriate measurments etc, not a easy quick fix i'am afraid but ultimatly more accurate. Unless your lucky to have an identical boat/rig to a-n-other top yachter!


Posted: 09/06/2005 22:52:39
By: Barry Watkin

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