Monday, August 22, 2005

In Search of the Perfect Shape

While aboard our boat in race 7, the our on-loan tactitian/foredeck person remarked (rather unfavourably) on the shape of our spinnaker. He insists that it is not a J/24 spinnaker. His comments were based on the odd pear shape that the spinnaker seems to have.

My first reaction was that the spinnaker was most likely a cruising chute. And since it was inherited with the boat I have little information on the sailmaker and or reasoning behind the shape. A little more research has left me even more unsure. From what I can gather it may well be a J/24 spinnaker. I read some posts which indicated that in 2000 the class rules for spinnakers only set one measurement (maximum centre width) which apparently spawned these odd pear shaped beasts. The foot of the sail can be as wide as the sailmaker seems fit to make.

I have begun to dig a little deeper into the matter but can not find much information on these odd-shaped sails and whether they perform better than the tri- radial spinnakers or not. I assume the basic premise of the wider foot is that it will help stabalize the boat. Most designs I have seen are wide top shoulders and a straight leech.

The Sobstad website does not seem to shed any light on the subject. There were a few other sites that I did investigate in regards to overall spinnaker design and funcition

I did however find a link to what I think is a rigging and or sailmaker shop that refers to the J/24 and identifies the design rationale for the full radial sail. It sounds very similar to the one that is in our inventory:

Full Radial Spinnaker

The Full Radial represents the latest thinking in running spinnaker design. The J/24 class rules specify only one spinnaker maximum width, in the middle of the sail. Above and below this girth the spinnaker can be as wide as the sailmaker can make it. This often results in odd shaped spinnakers with a "pear" shape. These sails can often be difficult to fly especially for less experience trimmers.

To design the Full Radial we took our own ideas about fast J/24 spinnakers and talked to the best designers North Sails has, many of which have been deeply involved with the build up to the America's Cup. What resulted is an easy to fly sail with maximum projected area in the bottom sections. The Full Radial's even shape makes it easy to fly even in the most difficult conditions.

I need to take a closer look at the sail and see if there are any identifying marks (other than the sobstad marked spinnaker bag that it came in) on the sail that will help me get to the bottom of this quandry. In the mean time our competition has graciously offered us their spare spinnaker to test fly. Should be an interesting test. I think the best way to benchmark the sails is to flake both of them and fly them in the same outing to see if there is a huge difference. Stay tuned.


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