Slickest folder ever

Agreed. High drag is a major concern. What interests me is Marchaj's wind tunnel tests on the crab claw sail, which did very well upwind. I was wondering if at smaller scales the gains seen with low aspect "wings" at high angles of attack outweigh the drag they create. The plane was only meant as an example of a successful low aspect ratio wing shape that has a very impressive stall angle at speeds that can be experienced in the form of apparent wind speeds by small multi hulls.

what I'm trying to say is there is evidence that support's frank's claim that his fan sail can sail closer to the wind than a Bermuda rig. The plane is an example of a low aspect wing with a high stall angle at a low speed. Marchaj's crabclaw wind tunnel work also supports frank's claim. All I'm trying to say (albeit poorly) is that perhaps in the case of a small tri the added drag of a high angle of attack is less of a factor than the gains provided be the better stall angle.

I could be way off base.. I was just thinking out loud I guess.

Both Boeing and Lockheed have "facet" flat panel low aspect fighters in the works.

 

Rapscillion,

I work for Lockheed, not in advanced design, but on aircraft structure. I sure would be interested in a reference, since I am on the program which is supposed to be "the last manned fighter" this century.

Flat panels would make a serious complication to how we build fighters for production - I expect it would cost a lot more.

You could call the F-35 wing a low aspect one but they are not much different in shape to many recent fighters. WW2 was significantly different.

I need to find the 3rd volume of Aero Hydrodynamics so I can see the discussion on crab claw

 

I would like to get back to the slickest folder ever.

Aircraft are boring.

Frank, have you ever tried to reef the Fan Sail? Do you rake the mast more after it is reefed?

 

Hi Marc - I originally had a brailing line on the fan sail, but it seemed to be in the way a lot so I removed it. I haven't tried reefing it per se, as there are no reef points or lines. But ultimately I plan to have full-length radial battens, which will make reefing a real possibility.
I have tried raking the mast back from its "normal" 78 degrees, but that only aggrivates my weather helm. Not sure what to do about the weather helm. It wasn't quite a noticeable on the double-ender hull. Actually, I did end up putting a small skeg on the double-ender, which eliminated the weather helm. Hope I don't have to do that on this hull.
I'm also considering some small skegs on the amas. Maybe I'll make some strap-on skegs that I can move fore and aft to see where they actually belong. I can't easily move me or the leeboard, and the sail can't get much more vertical. So a skeg on the main hull or the amas may be the best solution to correcting the weather helm.
- Frank

 

That's funny!
Sorry for the airplane tangent. I don't work for Boeing or Lockheed, but i have been spending a lot of time (3 years) working on composite panel for such a project... Send me a PM.

 

Frank,

I know you have a nice simple rig, but if you had a traditional mast with a sailtrack on the back would that allow you to reef easier? I guess you would need to add a halyard, a downhaul and an outhaul to get the sail to come down the mast. That would cause the sail to almost stay in the same position, just a little forward for a first reef. That should allow you to avoid the weather helm issue with reefing.

About the weather helm. You can't pivot the leeboards enough to compensate? Do you think a larger rudder could take the place of the skeg or boards in the amas?

 

Hi Marc - I'm sure a traditional sail track mast would allow for easier reefing, but I consider stayed rigs such an all-around PIA that I just don't use them any more.
I do use a leg-o-mutton sail rig a lot on our other boats, and those can be furled around the mast for reefing if you can work around the boom.
Even with the big leeboard pivoted aft, I still have too much weather helm on a broad reach or run. Yet close hauled, you don't even notice it. I'm considering a bigger but shallower rudder as well.
I'll report on my findings as soon as I have some
- Frank

 

DIY Guy,

I was thinking about an unstayed mast with a track.

How much trouble would it be to move the leeboard pivot? That might allow you to position the leeboard for both windward and reaching - finding the sweet spot. Do you use both boards at the same time?

Marc

 

Marc - I never considered an unstayed mast with a track because I've only seen them in carbon fiber, which is way out of my price range. Plus, I just generally don't like sail tracks because threading a sail in is a PIA. Also, since my battens are radial, a sail track wouldn't help with reefing.
As for the leeboard, there's only one (like in Laura's boat) and it would be tough to move it aft. It's now at the widest point of the hull, which means it's parallel to the keel.
I think my first attempt at a solution will be to try to move the sail COE forward by making the mast more vertical.
Won't be easy, but then, neither will any of the other potential solutions. But then, it's otherwise such a sweet sailing boat that I'll just have to fix the weather helm no matter what it takes.
- Frank

 

DIY Try Guy

I am also working on this sail that roller furls. It should be done this weekend to try out.

 

Looks sweet. How is this different from the previous setup?

 

Hi Chris

The two top batten locations, angle and diameter has changed. Little steps on trying to make the sail work better without the squartop blowing off in light air.

 

Looks great! I was thinking about how one could reef a sail like Frank's Fansail, and I'm not sure a furler would work. I think it would have to be reefed like a junk sail, and it would work better if the sail was fully battened, like Frank had suggested earlier in the thread. I'm eager to hear Marc's opinion on Marchaj's work on the crabclaw after he gets a chance to look at it. Those results have always fascinated me; perhaps even more so now that frank has developed such an interesting rig that has a similar shape.

 

Frank,
Increasing the "lead" to get rid of the weather helm should work. I think everything you have suggested so far would help. How hard would it be to move the sail forward by lowering the sail on the mast?

 

My plan for reefing the fan sail may or may not be practical (as I haven't tried it yet) but it would involve having a series of grommets along the trailing edge of the middle full-length batten and lacing a line from top to bottom through the grommets and around the mast. This design (basically a glorified brailing line) could quickly -- and most importantly, remotely -- reef the sail.
Un-reefing it might mean lowering the mast a bit so you can losen the lacing, but I think that's a tolerable trade-off for a sail that can be quickly and remotely reefed by 50%.
Of course, real-world testing may show it to be just another pipe dream. But I am pretty sure it will work.
- Frank