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Old 20-09-2014, 05:15   #1
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Prout Snowgoose - Sail trim, autopilot and confusion

I have a 1977 Snowgoose 35 and after about 5000 miles of sailing her in all conditions (UK south coast last year and then down to the Med so far this year) I am rather confused...

Firstly, she has been modified from the original sail plan to have a much larger genoa - runs about a foot past the mast with new tracks set behind the mast and further outboard than the original coach roof mounted tracks. (As Snowgoose aficionados will know the mast is well set back on these so my genoa foot is around 6m on a 10.4m boat)

My first problem is this - downwind sail trim is as expected, close hauled trim is as expected but she is very much faster on a reach sheeted in very tight - maybe let out a couple of feet max from the close hauled position for a beam reach and a couple more for a broad reach - but always much much tighter in than any yacht or cat I have seen. The telltales do not always agree with this sheeting position but the speed over ground (checked on 3 gps) is always much better like this - sometimes over a knot better than when sheeted "by the book"...

Does anyone know why this would be?

I also seem unable to trim the sails ideally to give my old autopilot an easier time. I should mention that the boat has in mast furling and so a tiny (3m foot un roached) main

The autopilot is a system by a new defunct company called Global who were taken over years ago by the now defunct Cetrek. It is very basic -a hydraulic system which activates the two opposed pistons attached outboard to the two rudders.

In anything but flat calm it wanders about perhaps 20 degrees either side of course. It is worse under sail than motor. In big following swells like many autopilots it cannot cope at all really.

The boat seems to be drawn to windward on a reach and then the autopilot compensates, but over compensates, and back and forth we go. It does generally stay to track over time but the constant swinging is bad for speed.

Nothing I seem to do with sail trim helps - with such a huge genoa and tiny main am I on a loosing proposition from the start? I am planning to upgrade the autopilot this winter to the Simrad system (as we have their NSS8 chartplotter which can work as the control head) - is this likely to be any better or are their fundamental flaws to overcome first (such as changing the sail plan)?

Any advice form those with experience of these boats would be gratefully received
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Old 20-09-2014, 06:29   #2
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Re: Prout Snowgoose - Sail trim, autopilot and confusion

i would check the rudder response setting on the auto pilot,it may be that it is under correcting.
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Old 20-09-2014, 07:35   #3
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Re: Prout Snowgoose - Sail trim, autopilot and confusion

Its currently set on "automatic" but I'll try each of the manual response settings and see what effect it has... thanks
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Old 20-09-2014, 07:46   #4
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Re: Prout Snowgoose - Sail trim, autopilot and confusion

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Its currently set on "automatic" but I'll try each of the manual response settings and see what effect it has... thanks
you might also find with the further back sheeting positions of your genoa ,this has also shifted the center of effort further back,making the realitively small rudders more suseptible to weather helm on some points of sail.
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Old 20-09-2014, 07:53   #5
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Re: Prout Snowgoose - Sail trim, autopilot and confusion

I'm starting to wonder if I should go more back to stock sizes - the boat was designed for a 29m2 genoa - ours is around 42m2 - and the original No1 jib would have been 20m2

I'll get all misty eyed for hank on jibs in various sizes in a minute too...
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Old 20-09-2014, 08:04   #6
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pirate Re: Prout Snowgoose - Sail trim, autopilot and confusion

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Originally Posted by Snowgoose35 View Post
I'm starting to wonder if I should go more back to stock sizes - the boat was designed for a 29m2 genoa - ours is around 42m2 - and the original No1 jib would have been 20m2

I'll get all misty eyed for hank on jibs in various sizes in a minute too...
Naah... just start furling earlier...
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Old 20-09-2014, 08:05   #7
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Re: Prout Snowgoose - Sail trim, autopilot and confusion

Quote:
Originally Posted by Snowgoose35 View Post
I'm starting to wonder if I should go more back to stock sizes - the boat was designed for a 29m2 genoa - ours is around 42m2 - and the original No1 jib would have been 20m2

I'll get all misty eyed for hank on jibs in various sizes in a minute too...
the larger genoa should be ideal for down wind work where it is effectively pulling the boat,with little sideways pressure on the rudders,and ce well forward.

whereas once the boat is on a beam reach or beat, the keels and rudders come into play counteracting the force exerted via the center of effort on the cats forward motion hence more weather helm with a genoa that is further aft than the designed sail area.

as phil says furl earlier so the smaller genoa profile is further forward
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