Would you be kind enough to share your experiences on their performance?

​@@johnq.public2621 Perhaps the easiest way of responding to your question is to refer you to a video I posted a few months ago that draws on three short seasons of sailing my Mana 24 equipped with wing sails. For the type of sailing I do, which is for pleasure and not for racing, I am rather fond of the Wharram windsail. My boat is certainly not the fastest on the lake but in the right conditions, it can hold its own. I can count it to be one of the safest on our prairie lake which, having been formed by flooding a wandering river, is prone to very strong gusty winds which change direction unexpectedly. The sails are easy to reef when sudden weather swings dictate it to be necessary. The best way to judge the Wharram windsail is to sail on a boat equipped with them. kzfaq.info/get/bejne/rNR7krCT1p2ldmQ.html

it might give old wharram a conniption

Hello Michael - it looks to be a 'vang' that can be useful for adjusting the sail twist in some circumstances - clearly not being used today! Might also be a line for hoisting a burgee or other flag? My guess would be a Gaff Vang: en.wikipedia.org/wiki/Gaff_vang

Its a vang, not used for the demonstration ;)

Its the vang, a line at the gaff to control the twist ;)

How about some wind tunnel testing?

No wharram simply advice to buy it from jeckels. No diy for the sail unfortunately :( We will release the plans for this cat soon: kzfaq.info/get/bejne/g817dtqgtZu2nXk.html The plans will be free most likely and include the sail. If you have one or two months I would wait and build the traditional marshallese sail.

Yes, that's a kind of gaff sheet for twist control.

At 2:29 ? It is the Cunningham, to tighten the luff of the sail to make it set prperly.

I'm picking that those rings are at the reefing points.

Any reputable sailmaker will do the job.

Wharram was one of the earliest Western catamaran designers. Perhaps that will help you find a reference. Given that most Wharram catamarans were home built, most of the sails were probably home sewn, although today I think sailmakers know how to make them.

It seems like you would always be able to luff the sail. There is no boom and no spreaders. But I am curious if there is ever any problem with binding.

just lower the top boom

the same way you reef any sail. there are two sets of reef points on the main, one on the jib. so you lower and tie, just like always

I doubt that the airflow over a soft flexible surface is ever smooth but wharrams are known for good performance

Good performance??? Compared to what?

any sailing vessel of a similar length and weight,vortex generators are used on all modern stol and low speed aircraft,all wing or foil surfaces have flow comprimises

@@cartmanrlsusall Thank you. The slot between mast and leading edge of the sail would improof performance. Soft wing sails demand great attention to trim and are not practical for cruising. Traditional sails using hoops or leacing generate more drive and are more forgiving in finding the fine trim automatically, says my father.

@HappyandAtheistthere is a video of a tiki 38 called pilgrim, during it's first Atlantic crossing the crew intentionally steered down swells just for the thrilling ride that they called surfing. If that's not a demonstration of a strong design, then what is.the sail having turbulence is irrelevant it works