Wharram style “soft wing sail” viability on a monohull

Hi Steve,

I am designing a rig for a 42′ cruiser (monohull). Due to the nature of the hull I need a lot of sail area and a low center of effort. James Wharram, about 20 years ago, developed what he calls a “soft wing sail”. It is a gaff rig with the leading 1/4 of the sail made up as a sock which slides over the mast, in place of hoops, lacing, etc.
It’s obviously efficient aerodynamically.

My concern is that friction between the sail and mast could cause problems with reefing/dropping the sail. Wharram has been using the design now for decades and says that there is no problem, that it can be dropped on any point of sail. He has lots of boats sailing with this rig.

It seems to me that if this works on a cat it should work on a mono as well. I’ve crunched the numbers on rigging loads and mast compression and these can be made to work.

I’d greatly appreciate your thoughts any any experience you have to share on how this rig might work on a mono.

Regards, Paul

Leading edge socks have been around for many years. We used a versionĀ  of this on a C-class cat in 1968. They are efficient, but bring a lot of baggage with them in termsĀ  of reefing, friction, cost, and complexity.

Some of the early free standing rigs tried to develop this approach, but ran into the practical problems above. If you are cruising locally, and into tinkering, might be an interesting project with which to play.

But my feeling is that for a long distance cruising boat they are not suitable.

Posted by Steve Dashew  (June 23, 2009)

2 Responses to “Wharram style “soft wing sail” viability on a monohull”

  1. Noel Anderson Says:

    HI… If I remember rightly, did not the Freedom 40 cat rigged ketch have a type of softwing sail, with a “whale bone” boom….I understand that it performed quite well….

    My kind regards Noel in Kiwiland

  2. Paul Schweikert Says:

    Hi Noel,

    Sorry for the late reply. Yes, I remember the early Freedoms did use a sock type, softwing sail. But the later Freedoms changed to a conventional slide/track arrangement. I don’t have any experience with these boats, so can only assume that the sock approach had problems. But, it was good enough that they used it, at least for awhile. I’d like to know what specifically the problems were, and whether there is an approach that might overcome them now.

    Regards, Paul