JunkFoil

Hi,
I've been a bit of a lurker, and haven't been sailing in years. But I was thinking of maybe building something small to get back into it. I think I prefer easy to exhilirating most of the time, so I've been looking at junk sails. The Aero and split junks caught my attention, but the aero junk reminded me of something I couldn't quite place- til a short while ago: It looks like the frame of a light plane wing. So this made me think a 2 skinned (cambered panel) foil sail could be made on a similar frame. More complicate to make, but it ought to be more efficient, and hide the mast aerodynamic interference, while retaining easy reefing and the nice fore-aft balance the split and aero junks see. I even got optimistic about schooner rigs and slot effects Thought I'd see what people thing of the idea. Honestly I mostly expect something like "O! that's absolutely out. In 1952 Sven Beardson ran a similar rig in his herring skin racing umiak and was devoured by rogue orcas 80 miles north of Svalbard. It has been taboo among serious sailors to consider any like this rig since." I guess we'll see. It currently seems useful

 

In principle, yes, but it was Robin Blain instead of Sven Beardson, it was 1983 instead of 1952, and it was a commercial product instead of a one-off. I had the same idea as you, and two weeks later I saw Robin Blain's ad for what he called the swing rig. And I am not sure Robin was the first.

More recently, David Tyler put articulated soft wing sails with junk-style sheeting and reefing onto Tystie. Join the junk rig association, and read about lots of varieties of junk rig: The Junk Rig Association - HOME https://www.junkrigassociation.org/

As for Tystie:

 

Good finds both. Tystie's sail had what? A "too much hardware" problem? I hadn't seen it, but approaching the contruction from the "not too much hardware" aerojunk foundation might find a way around that? It seems like the principle is sound and the implementation is the question. We see the aerojunk manages what it does at acceptable weight and strength. The idea was to build on that, and try to stay out of hinges and extra controls. Tyler'ssail suggest leech options that might be better than what I pictured. Thanks

 

Double skins don't really make sense unless you are sailing in very high winds at very low angles of attack where it becomes very hard to manage the camber distribution and span loading with conventional sails. They are just an expensive pain with out any benefit otherwise. It's the sort of thing where you pay somebody else to sail the things and put your name on the boat. And you would have to build in all carbon and have the twist control inside the wing and spar like AC boats, otherwise the line drag of the normal junk rig defeats the point. Boat needs to have aero and hydro like an AC boat before bothering with twin skins.

 

It doesn't seem like those assumptions are at all clear. "Things I belive make me think this is impossible" doesn't really help running numbers. Let's start with Twist control? Why is interior twist control plus traditional junk lines "necessary?"

 

Not plus traditional junk lines - in lieu of traditional junk lines. They have too much aero drag. It is far greater than anything you could expect to gain with twin skins. You need to do a ruthless assessment of lift and drag, both aero and hydro, and see where the trade-offs are that are within you financial budget, and within your sail control power budget. Junk rigs have relatively low tension on any given line compared to a high aspect Marconi rig, but the power budget for sail control is still pretty high to make them work well. They reef very well, but other than that, they don't have much going for them performance-wise. With modern diesel auxiliaries, there's no reason to avoid them as long as you don't ruin their virtues. They can be reefed well, the sails can be adjusted by one person without elaborate winches and tackle, and they can be rigged to self-tack if desired. You will diminish all of those features if you try to go twin skins with them.

When looking at sailing performance, adopting twin skins is literally the last step in line because it has the smallest payback compared to the added cost and added frustration. Making the keel about 2" deeper would probably have a greater performance gain. Changing bottom paint would also. Making the boat a few pounds lighter would be a bigger gain. Using a folding or feathering prop instead of a fixed prop would have 100 times the effect of twin skins. Twin skins just don't offer the gains you think they do.

 

I think we are looking at different junk rigs? The AeroJunk solves a lot of this already. Also I think we are at cross purposes here. I'm interested in the rig- if the details can be hammered out it could be tested on an ebay laser to start

 

A Laser has a bendy unstayed mast designed to depower on gusts. Do you think it is a good platform to test a complicated rig designed for a keel boat with a stiff mast?

 

Omg no. I was picturing aluminum pipe. Honestly an OZ Goose is probably a better platform. You're quite right, bending the core of the assembly like that would at best add a lot of potential complications, at least for testing

 

..but the "designed for" issue seems like a side issue? The Junk was designed for shallow draft scows without keels in Asia. Modern junks are already quite different. The split and aero junks already have a lot to recommend them. The "slow junk" seems like it's historical, and a product of the traditional rigs' virtues being really suitable to staid cruisers (and some drag and angle performance biases). jbwatercraft has some junk rigged proas that look handy enough . But I'm floating the idea that a standout virtue, reefing, might possibly be combined with a purpose built foil. It can't hit F50 drive or anything, I'd bet, but it might be more efficient than its predecessors if it can be done- and even a slow boat might want more efficiency and less sail, maybe; and a fast one might like some "o shoot" reefing. So the basic issues seem more like weight and complexity. I bet those can be solved

 

This made me smile because for those of us that started sailing the laser at 130 pounds or less before they came up with the radial rig, the 4.7 rig, or the concept of “too much wind to race”…. the laser WAS a platform for experimenting with a very unforgiving rig.

I was amazed when I first sailed to boat at 170 pounds and the mast actually bent sideways like it was supposed to. Totally different boat.

One major complaint I have with the laser is that it breaks too easily, and just about anything that breaks can make it very difficult to sail back in. Great for racing even in extreme conditions, but not so great for adventure sailing without a support boat.

A scaled up Optimist Pram rig would be a great way to turn a laser into an adventure sailing boat. You might still want to fill the hull with a bunch of empty 2 litre pop bottles.

 

I hadn't touched a laser since I was a kid. But, yeah, something a bit...more... in stitch n glue would be better. The laser came to mind as being sensitive to drive and heel and efficiency

 

I tried a simplified version. Thoughts?

 

Some drawings would be helpful. As a dedicated proanut I've come to appreciate simplicity which is not easily accomplished.