Help advise needed

01/04/2010 16:04:09
Okay some advice needed please hopefully some one who has a thin ice and would be able to give me some measurements (or some one who has stepped a superspars carbon rig). I am trying to step a carbon rig onto my thin ice and I have a few issues with how to get it right

1: Mast foot position from the transom to the back of the mast, I have the settings from the ally rig but was wondering what yours is

2: the distance from the back of the heel to the point that the shroud goes through the deck (the ally rig I had on her had a pulley at the bottom of the shrouds, which was made up of a wire coming of then a fixed point on the deck through the pulley at the bottom of the shrouds then through the deck to a pulley system on top of the buoyancy tank I want to do away with the pulley at the bottom of the shrouds but by doing this it is altering the position the angle of the shrouds and it doesnít look right)

3: the distance from the back of the mast to the point at which the lowers go through the deck (The alley rig had fixed carbon struts going up to a track on the mast and I would prefer to get rid of this as I donít want to put a track onto the carbon rig.

4: Finally I have tried to level the boat up off the transom but I feel that the bow is far to high up so I have levelled her off the bow is this okay because it looks like she is pretty level?

Sorry if this has all been asked before but I donít want to start cutting holes in the deck to have to do it again and unfortunately there are no over modern Merlinís at our club. I have looked at pictures and read all the tuning guides but to no joy on these areaís

Thanks in advance


01/04/2010 16:30:46
Stuart Bates (MR3615)
If I remember correctly, when Julian Parry had the boat built the Transom was not vertical, so checking it off the bow would be the correct method.  If you contact Julian I'm sure that he would let you know his thoughts on the boat.

01/04/2010 20:15:42
I seem to remember that the mast foot position on a Thin Ice was very differant to a Canterbury Tales. It depends on the position of the centreboard and the rig in use will not affect it.

01/04/2010 21:03:18
Would moving the mast foot fore or aft by 10mm or so make a noticable difference to the 'helm' of the boat? with the CB moving around as it does, a 10mm or so change to the mast doesn't seem like much, especially when the centre of effort moves around the sail with each of the sail controls being used and the board swinging back and forth. I've wondered about if for some time!

02/04/2010 08:47:37
hi paul, see if you can get some info off pete scott, he had the original with all sorts of masts on that ,i'm sure he would be a mine of info!

04/04/2010 00:33:35
Have you read the article in the library by Dave Fowler on "Deck Stepping"? He says 2730mm from top of outside transom to back of mast (including "sail groove"). Doesn't say what boat this was. Doesn't say where centreboard was, but could be a start.

04/04/2010 08:19:03
We have a thin ice in the yard at the moment, i'll try to remember to measure it today or tomorrow.

04/04/2010 08:29:41
From memory the boat was an NSM II. I measured a number of Canterbury Tales designs by various builders and they were all (From hazy memory!) 53 inches from jib tack to front bolt on the step. The Thin Ice was differant, might have been 49 inches i can't remember i'll measure later.

04/04/2010 09:59:47
I've had the opportunity to measure a couple of Thin Ices and the jib tack to front of mast(mast not step bolt) varied between a bit more than 49 inches and just over 52 inches.  Didn't get the distance to centreboards on those or the 'tales but for comparison, the turner tales and winders I've compared are all 53 plus a bit, by my measuring points, but they weren't intended to be mm perfect.
To complicate things further, some of the Thin Ices had 'larger' spin chutes, meaning the jib tack started further back to begin with, so presumably the jib/mast slot was different on all.

I'd be really interested in the mast dimension of another Thin Ice, if secondhandman has it, and the front of mast/centreboard measurement to compare to mine. Would be nice to compare to a winder fom/cb measurement.

04/04/2010 19:23:50
Peter Scott
I did indeed have the original 'thin ice'design (3490 - Wing and a Prayer)which started life with a wing mast - all 22' 6" of it - and a tiny 1.8 m2 jib. The mast was originally quite a way forward due to the small jib. 3498 was laid out in much the same way. WHen the wing mast project was abandoned the mast foot was moved back and Julian Parry undertook a similar 'mod' on 3498. He went on to win various opens with the boat. I can't recall any of the dimensions - too long and too many pints ago - however if 3498 was as Julian left her I would not be over fussed about the numbers. 
The boat carried weight (!), won Silver Tiller meetings and was vice free - enjoy!

04/04/2010 20:03:03
I've measured 3510 (Rowsell Build) tonight, 52 inches from the jib tack. Winder CT is 53. I'm absolutely certain 3497 was 49, but maybe i'm wrong.

04/04/2010 21:00:49
Richard Battey
Gosh 3510! (clear ice) I remember accidentally holing that boat port side bow just below deck level, at Bewl Water, right on the start line, having got well and truly hemmed in with no where to go!! At the time circa '94 a very angry Mr Bramley cursed me as the boat was pretty much damn well new!! Richard continued the race, I immediately retired and the insurance bods sorted everything else out.

07/04/2010 09:13:30
julian p
Pabs  As I remember the mast  should be as far back on the mast step as possible,the jib halyard sheave is on the last hole on the mast step and the mast butts up to it with just enough room for the rope
To move it forward will upset the shroud base /mast measurement which was set up to replicate the JT Canterbury tales and is the standard set up on the Winders.
Hope this helps

07/04/2010 09:16:30
julian p
As Stuart states the transom is angled  so the pivot line passes through the rudder leading edge the give it balance


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