Scott Dufour wrote: Hey Eric,

Referencing Sleive's files, I have to ask the question:

Doesn't your approach - at least in step 1 - put the curve at exactly the wrong spot?  The aft section of the sail is usually kept as flat as possible because a hook in that area contributes mostly drag.  It's camber in the forward 1/3 that makes the lift to windward.

Michael - are your forward sheets constantly getting hung up on something?

Sorry I missed that answer.

The idea is not to add some camber at the rear but to limit the camber at the rear when the wind is increasing. It allows more flexible battens in light airs. I'm convinced that, while efficient, rigids battens are contradiction to the natural adaptative flexibility of junk rig.

The main issue I (re)found is that you can't have flexible battens on the forward part of the sail. It leads to "S bending" (PJR fig 1.8) (I tried and it is not confortable). At best, with a flat sail, with a rigidified fisrt third forward batten, you optain a flat entry (where you would like to have camber), a cambered middle third (similar bu smoother to articulated battens) and a rather flat third rear area (which is good). It's far from optimum. It may be improved by a forward barrel-cut for example.

But the flat sail is not the point. The point is the junkwing ; with a thick rigid profile (build up out of flexible battens maintained by a limited structure), around the mast, on the first two thirds of the batten and a lambda sheeting at the end of the wishbone part and at the rear in order to use the rear third of the sail to provide the profile camber.

I tried it on the demonstator, in light wind, and it worked very well.

I tried it on the ground in heavy wind (25-30 kts gusting) and the very light build sail was not too bumpy and resisted well.

The next step will be to build a sail for Mingming and try it at sea....

Eric

noob question here, would adding a gurney flap to a fanned sail simplify passing the sheets over when tacking? 

I've occasionally wondered if i could use one of those dog leashes that automatically wind in the leash to keep the tail end of the sheet rope up and out of the way. I suppose salt water would destroy them though.

Bill

I have double sheeting on my 20 foot cruising boat, and I like it quite a lot. It keeps the cockpit clear of the mainsail sheets, and makes for much easier backwinding of the mizzen. I would honestly hate to give it up, though I do understand your concerns about lots of lines. Such trade-offs!

Shemaya

Eric Andlauer wrote:

Michael Young wrote:

 Any thoughts?

Bonjour

On Mingming, on a slow process, i'm experimenting what I called Lambda sheeting. The iidea is to have a two sheeting points on the batten one at the aft end and the other about one therd of the batten length forward.low tec- low cost-wingsail demonstrator

With a flexible (aft part) batten it allow to have a curved profile with a flat sail.

It's a two step experimentation, the lambda sheeting is limited, as such, on a "flat saile" as the forward part of the sail (the most important) must remain flat to prevent "S-bending". It could be used, for example, in conjonction with a forward barel cut sail and flexible rear battens.

the second stage of the experimentation deals with a junkwing with a profile on the forward part of the sail and a flap at the rear. Then the lambda sheeting would allow a flexible junkwing.

With a lambda sheeting, the sheets are separated by the sail and are less messy than if both sheetings are linked to the leach.

Eric

Referencing Sleive's files, I have to ask the question:

Doesn't your approach - at least in step 1 - put the curve at exactly the wrong spot?  The aft section of the sail is usually kept as flat as possible because a hook in that area contributes mostly drag.  It's camber in the forward 1/3 that makes the lift to windward.

Michael - are your forward sheets constantly getting hung up on something?

I agree that there is enough spagetti on deck without adding a whole additional set. So I am looking at reducing it to a single. I see the longer batten I think Arne does. Maybe this would make it feasible. If I can’t ... I might go to a gaff foresail. One advantage to that would be educational for the scouts who charter the boat. Any thoughts?