Spinnaker Size ?

S

Smuggler

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I have a Newbridge Virgo Voyager and have enjoyed using my spinnaker on many a long run, however it is fairly small and out of proportion to the rest of the rig. I have two questions ;

1. Is there a standard measurement system for spinnakers ?

2. How do I determine the optimum size of spinnaker for my boat ? (without trial & error...and a few broaches !)

Any suggestions very welcome !


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You need "I" and "J" measurements. These are mast height above deck and the mast foot to forestay point. Then you can click <A target="_blank" HREF=http://www.sailsdirect.com/action/downwindsizes.asp?Sailtype=S>here</A> and input the dimensions. They will quote the size and price of a sail.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by robp on 05/08/2004 18:59 (server time).</FONT></P>
 
I'd suggest before determining size, you work out what you want to use it for. If it's racing, then you probably want to add a symetrical spinnaker. If it's just cruising, then you need to consider whether you go sym, or asym (also called Gennaker, Cruising Spinnaker, Multi Purpose Sail 'MPS', and others).

Regardless, sailmakers seem to recommend something like 102% to 105% of forestay for the luff(s), and something in the order of 160% to 175% of "J" (the horizontal distance from mast to forestay attachment point). Next you need to determine what shape you're after - if racing, then full with big shoulders is the go, but if cruising, flatter cut with less shoulder makes the sail easier to manage, and allows you to reach higher on the breeze.

I'd go ask a sailmaker for advice, evenif you plan to buy secondhand.



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Agreed, talk to your sailmaker. We'd reckon somewhere around 37 square metres. We'd design it based on what you were going to use it for. Broad shoulders and a fat kite are useless when sailing on a broad reach but brilliant when deep etc. etc. Also the weight's fairly important - on a Voyager more from the point of view of handling - no more than 0.75oz though (a lot of guys recommend 1.5oz but this is useless until about 15 knots of breeze on a boat your size)

You might want to measure yours to see where you are using:

0.83(luff+leech/2)(4(spin mid girth)+foot/5)

Finding the mid girth is fairly easy, it's the distance between the two leeches at the halfway point.



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Hey Racingron - how can you spare the time to respond here when the sa discussion is underway? ... :-)

Re the spin formula, can you post one for asyms as well?

Taa
Rick

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