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Another question, spinnakers , alt/assym/sym

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Do Different View Drop Down
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Post Options Post Options   Quote Do Different Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 18 at 11:21am
Interesting as it is all this talk of speed gains from kites is focussing on what is for me a lesser benefit. 
Admittedly I've not tried to master the handling of a kite on a single hander but on two person one wire boats both assy. & sym. the kite adds a whole heap of stability off wind.  
I know on the Contender there a very busy point of sail between power reaching and deep running that it can get very squirrelly. With a kite up that point becomes a lovely easy series of flowing S curves.

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Post Options Post Options   Quote eric_c Quote  Post ReplyReply Direct Link To This Post Posted: 19 Feb 18 at 5:37pm
RS800 is easily 50% faster with the kite up sometimes, provided the kite takes you in the right direction.
It's hard to make valid comparisons, there are not exactly a lot of well-founded PYs for comparable boats with and without kite.
RS 600 vs 700? 8%
RS300 vs 100? which main size would you like, one is slower.....
But RS100's struggle on anything that's not a broad reach or a floater.
So it's significant we are talking about a trapeze boat that will more often be underpowered downhill without a kite.
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Post Options Post Options   Quote watermouse Quote  Post ReplyReply Direct Link To This Post Posted: 22 Feb 18 at 10:57pm
Hi Guys.
First post on this forum but this thread was brought to my attention through FB.

I was the builder and first owner of Farr 3.7 #385. The one with the green gennaker in the video on page 8. Although that is the second owner sailing the boat in that clip.

I built it early 2003 from the class association molds with the intention to run it both in class as a fully measured 3.7, mainsail only, but also with provision to run a fixed prod and gennaker. The inspiration was boat #376, a carbon/foam boat with prod and gennaker built by my then employer Alex at C-Tech.

#385 is fibreglass/epoxy/foam sandwich and came out well under weight. This was a bit of a problem as with the maximum allowable corrector weight on the bulkhead it still was 3kg under. At the 2003 3.7class NZ nationals and AGM it was discussed (#376 carbon boat had the same issue) and agreed we could make up the weight with lead equally distributed inside the prod socket and on the rudder gantry. Hence why #376 was named Lead Mine.

I sailed it in class spec for a season before finishing the gennaker system. I was offered a gennaker made from leftover material by Chris Skinner at Fyfe sails in Auckland. There was no choice, Green it was. It cost me a box of Steinlager. I think Chris should have asked for more.

The gennaker was stowed in a sock on the foredeck reaching back into the cockpit with a continuous halyard retrieval system. I created a new snout that allowed the gennaker to be set and retrieved on either tack under the forestay.

I only once sailed against #376 in gennaker mode and that boat was clearly quicker. I think a slightly more open leech. Mine was a bit choked, but I was also the lighter sailor. 
The boat was much more stable downwind, much less inclined to nosedive and significantly quicker than without the gennaker. I found that with the main backing from the kite I could sail controlling only the gennaker sheet without the main in hand a lot of the time. I could stand further forward on the trapeze. Gybing could at times be a bit messier but not that difficult. I found retrieving the kite was the hardest. Impossible to do from the wire as it required standing in the boat and these boats are not the most stable. So setting up for a mark rounding took a bit more planning and precision.
I did sail against other 3.7's in informal races and the gennaker clearly showed it's advantage downwind. I let a few other people sail the boat and they were generally impressed.

In terms of allowing it as part of the class the only solution I could see was a class split which is not what the class needed. It was fun for mucking about and learning (I was also sailing 12ft skiffs at the time) But it was impractical for existing boats to retrofit a system like this and add unnecessary complexity to a class that is already challenging to sail.

I sold #385 in 2006 before travelling to the UK and Spain to work on AC and Open60 projects as well as a small stint with Kevin Ellway on one of his skiff projects and shore crew for Pindar.
I have done little sailing since, I do miss that boat though. Lots of good memories.
 
Hope that info is applicable to this thread.

Cheers,
Neil.
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Post Options Post Options   Quote Do Different Quote  Post ReplyReply Direct Link To This Post Posted: 23 Feb 18 at 7:31am
Many thanks Watermouse, a very informative post.  Thumbs Up
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 23 Feb 18 at 12:24pm
Hey Watermouse thanks for your input, excellent. I've got a couple of questions, what size is the gennaker and was it modelled on any other particular class?

Also you talk of a looser leech on 376 I'm assuming that's the main sail, or were you both using kites?

Edited by iGRF - 23 Feb 18 at 12:24pm
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Post Options Post Options   Quote watermouse Quote  Post ReplyReply Direct Link To This Post Posted: 24 Feb 18 at 2:31am
The size of the gennaker would have been about 7or 8m^2 but I cant remember exactly. It was modelled off the gennaker Alex had made for #376 by Fyfe Sails to his specification.

In testing I sailed against #376 with both boats with the gennaker setups. I was referring to the leech of the gennaker which I felt mine had too much of a hook and caused the main to backwind. #376 seemed to have a looser leech in comparison. This kept the top of the main powered up though. It was enough work keeping the small twitchy gennaker from collapsing the luff while working waves on the reach to really worry about the main. Any extra mainsheet would overpower me in moderate winds so I would just let it go until I needed to gybe.

The other aspect was the massive lee-helm with the kite up. It took a bit to get used to with weather-helm upwind and until the kite was set, then it was constantly pushing the tiller away to aim the boat. A rigid tiller extension was necessary, dropping the tiller at any point resulted in an immediate and catastrophic death gybe.


Edited by watermouse - 24 Feb 18 at 2:33am
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Post Options Post Options   Quote Do Different Quote  Post ReplyReply Direct Link To This Post Posted: 24 Feb 18 at 7:42am
An outsider question. Did you have a transom hung rudder or a gantry? Much do you think increasing the distance between rudder and board would dampen helm sensitivity?
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Post Options Post Options   Quote watermouse Quote  Post ReplyReply Direct Link To This Post Posted: 24 Feb 18 at 8:06am
As originally designed the rudder was transom hung but the more modern 3.7's including the one I built have a rudder hung from the gantry about 300mm behind the transom to slow the steering down. 
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Post Options Post Options   Quote Neptune Quote  Post ReplyReply Direct Link To This Post Posted: 24 Feb 18 at 9:54am
Massive Lee helm comes from not sheeting the main in enough, probably just need to sail lower
RS300, ex Musto Skiff
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Post Options Post Options   Quote I luv Wight Quote  Post ReplyReply Direct Link To This Post Posted: 24 Feb 18 at 10:26pm
With a big T-foil, you get massive lee helm if you windward heel, and massive windward helm if you heel 'normally'. so downwind it's OK because it's easier to heel over with a kite up / more power, and it balances. But less draggy to keep it flat if you can.
Lee helm helps offwind so you can go deep without too much steering, light rudder forces.


Edited by I luv Wight - 24 Feb 18 at 10:30pm

http://www.bloodaxeboats.co.uk
Andy P
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