AYRS/Bolger meets Maltese Falcon

If my title makes any sense to you you probably know where I'm going with this. Shunting Proas are such a different beast from conventional tacking craft. Some success has been had with modified Bermudan designs - they certainly shunt faster than dragging the crabclaw from end to end. But - with all due respect to the work of Russell Brown and others - a rig finely tuned and evolved for tacking is going to be suboptimal for shunting.

The AYRS/Bolger rig has held great promise as a reversible rig (ie with alternating leading edges, leech for luff) but I've yet to hear of a successful implementation (please correct me). Todd (tsstproa) has stunning little reversible wingsail model - it shunts on a dime. But its a solid sail.

The Dyna rig as implemented in Maltese Falcon is a tacking rig. Yet its symmetrical dual leading edges seem to be ideal for shunting!

Is the Dyna rig the reversible reefable sail that proa sailors have been looking for?

 

What about the Harryproa balestron with freestanding mast ? About as simple and reversible as it gets.

 

The great thing and also the biggest problem with the Dyna rig is that the center of rotation and the center of the rig are the same. Conventional sheeting won't work.

 

Anything Denney comes up with is, in my opinion, well thought out.

But - any rotating rig has big bearings and big (point) loads somewhere. This means heavier structure. Some of the rotating masts use 737 rudder bearings - neither cheap not simple.

A modern Bermudan rig is by definition high stress. A Dyna rig with a fixed mast seems to keep forces distributed and low, not unlike a junk or other balanced lug sail, only moreso.

The Maltese Falcon Dynarig is a high-tech beast, of course, with 60m masts! I'm thinking of a similar geometry but smaller with lower tech solutions.

 

care to elaborate? 'conventional' sheeting for a square rigger would be sheets from the ends of the yards...

 

Your comment about high load points being an automatic weight penalty is an unfounded assumption.
A fixed free standing mast has the same point loads as a rotating free standing mast and in the same place . The structure is different of course.

The only reason 737 Rudder Bearings would be so expensive is the requirements caused by aerospace testing. You can get the same bearing not certified for a lot less.

How long does it take Russell Brown to shunt? You make some general statements with nothing to back them up. That is not going to move this discussion forward with any confidence.

If you just slam everything you don't like with a general dismissal will you ever get a well thought out change?

Lastly, the AYRS elliptical sail has failed to be a "successful implementation". As far as I know this is absolutely true and the same for Bolger.
Can you tell us the design differences between the Dyna rig and AYRS or Bolger?
So far I really don't know what your point is and don't agree with some of your implications.

 

"Slam? " I'm not in this for an argument or to push some hobbyhorse.
I thought my presentation of the matter was fairly neutral, with credit to pioneers.
If it wasn't perceived by you in the manner intended, I hereby clarify.
My question is serious and well reasoned and I have no personal preference.
I'm here to learn and discuss.

>Your comment about high load points being an automatic weight penalty is an unfounded assumption.

Perhaps. But in the real world, engineering a rotating mast involves more sophisticated engineering solutions than a fixed mast. Without exotic and expensive materials and processes, it is unlikely to be lighter and it will not be cheaper.

> You can get the same bearing not certified for a lot less.

I'm sure that is true but its beside the point. I doubt anyone wants to accommodate a large, heavy and still expensive bearing below deck if they don't have to.

>Can you tell us the design differences between the Dyna rig and AYRS or Bolger?

Obviously they are many. But the design _similarities_ are that they are all symmetrical around the vertical axis. That they alternate luff and leech. Conventional Bermudan rigs are optimised for tacking non-reversible boats, just like their hulls. A reversible rig is harmonious with the nature of Proas. That is the basis on which I raised the question.

>don't agree with some of your implications

which implications are those?

 

Spot the difference.
Here is the Russell Brown proa Kauri going through a shunt.

https://www.youtube.com/watch?v=claP8d1RKY4

And here is a Harryproa with Balestron. (Being sailed by blind people)
Shunt is about 9minutes in.

https://www.youtube.com/watch?v=wftyqI2aJlo

 

Call me a perfectionist, but picking up the jib and carrying it to the other end of the boat just doesn't seem ideal. But, lets me clear, I'm NOT trying to set up some sort of silly Jzerro vs Harry war. The Aero clearly works but it seems overly complex.

 

I was answering upchurchers question about how long it takes Russell Brown to shunt

I'm sorry I'm not following you on the over complex with a free standing mast I thought it was pretty simple. If you are referring to the 737 bearings I think that is complexity for the sake of it.

 

I watched the Russel Brown shunt, again.
Did not look like anyone was trying very hard to make a quick shunt.
4 people sitting around and talking in the cockpit while one person did the work.
What I saw was an almost casual disregard for how long it took.
Realistically once the jib was on the deck, they could have sheeted in the main and been underway. That would have caused the jib to stream to leeward when they hoisted it on the other end but it doesn't seem difficult unless you were in a high wind situation. In which case you might not have wanted it up at all, or a small jib in its place.

In any case this does not seem to represent the best time, nor could I see how much time it took.

In the case of the Harry Proa, the time it took was clearly very little and it was very easy. They did appear to be trying to show just how quick it could be done.
Not much of a comparison then, but the Balestrom seems to win over any concept I've seen before, except possibly Newick's Cheers while not using a jib. That possibly was just as fast as the Balestrom - but you had to "tack" two booms instead of one.

So the Harry Proa is probably the winner on shunting time, but you casually dismiss it as "overly complex"?
Complex in amount of gear? or operation? or what? The only thing complex is the rotating rig (I assume that is for Aero efficiency) and the extended boom (Balestrom) used for a reduction in sail handling.
If you don't care about those two issues, I suppose you could call it complex.

If you wanted simplicity, Russel Brown could have put jibs in place on both ends on a furler. Roll up one, unroll the other and you are finished. Is that too complex? Or he could have simply kept a jib hanked on at each end and hoisted which ever one he wanted.

From what I see of MF, having multiple square rigged sails which furl into each of 5 booms per mast seems pretty complex. Someone help me and describe how you set the booms angle to the centerline of the boat.
All this looks like complexity for complexity sake. How do they control the leading edge of each of the square sails? One of the reason the AYRS sail failed was that the leading edge could not be reliably controlled to not collapse or roll up thus ruining the aero of the sail.
Anyone have any data about how close winded MF can sail? This is not sail rig independent of course, but I thought I understood the boat did not go into the wind very well. Given the engine in that boat they might not care about close windedness.
Given that the curved yards don't seems to allow you to adjust sail shaped, the yard curvature might not be optimum for all wind angles.
Aircraft wings and Bermudian sails are not that simplistic of a shape.

Help me again, do you have any information on the 737 bearing geometry? I only work on smaller aircraft designs and don't know how that one is set up - I assume this is a typical ball in a swaged race? If that is the design, that is as simple as possible.
Someone educate me.

I don't think I accused you of setting up a war, I agree that is a waste of time. I just think your comments are overly simplistic, and have no clear basis for your conclusions.

I'd like to understand in detail what your requirements are and how you reached your conclusions.

 

Todd's models are brilliant. As is his 16(?)'ter. But I would be a little cautious about scaling them up. As with all boats, you should consider the worst case scenario. With the AYRS rig (and with the stayed rigs) it is being caught aback. Sort this out, and the AYRS rig might be worth a look, although keeping the leading edge straight is a challenge. If the geometric centre of the sails aligns with the mast, the aerodynamic centre will be ahead of the mast, so you have to pull on the sheet (which is attached to the front of the sail) to depower. OK for racing, not so much for cruising.

An unstayed rig has very high point loads in 2 places. It is quite easy to strengthen them and spread the load. A stayed rig has high (frequently very high) loads on both ends of the boat and the sides. Therefore, the whole boat has to be made stronger. This is why harrys are the lightest boats for their length/accommodation/price. The materials and solutions do not need to be exotic. If the boat is designed for it, an unstayed mast is cheaper than a stayed one (eg 20m mast, 60 sq m sail, 24 ton metre righting moment, $US12,000).
It also requires no maintenance and has nothing to wear out. My next unstayed mast will not have a sail track or a luff pocket, further reducing the complexity.

The crew on the harry in the video were all handicapped, visually and/or otherwise. The only person who had been on the boat before was the guy standing next to the helm giving instructions. The shunt at 9 minutes was their second attempt and they were still learning. At 13 minutes they were getting pretty sharp.

Ballestrons are great for well balanced shunting and tacking boats. Almost no deck gear, soft gybes, low sheet loads, no foredeck work, etc.

John Pizzey used a variation on an AYRS rig on his proas. Basically a jib wwhere the sheet and the luff downhaul swapped role each shunt. Worked, but luff sag was a problem.

 

Controlling the leading edge is the reason these sails are not readily adopted. When the leading edge is sharp, the angle of attack must be very tightly controlled. Too little and the edge will flutter, ruining the flow. Too great and the flow will detach on the leeward side, ruining the flow. However, with a flexible leading edge it is very difficult to control the angle of attack reliably all the way along the leading edge. This is why square riggers have the sail broken up into several discrete section vertically, and why a Chinese junk has sheets from every batten, not just the yardarm and the tack. Both pay a penalty in windage and handling.

 

simply, a fixed mast is structurally simpler than a rotating one.

right, Others have done this. Downside - added windage. But again, its the adaptation of a tacking rig to shunting. My basic point is the Bermudan rig is optimised for tacking. We ought to be thinking about how different a design needs to be to be optimal for shunting.

All very good questions. I agree. And I do not know the answers. Bear in mind, mechanical solutions for a 300' superyacht are not right for a 30' boat.

 

On a Bermudan main, the mast stabilises the leading edge (with generally disastrous drag consequences). The jib luff is maintained by the forestay. How is the jib luff not analogous to the leading edge of a squaresail - in prinicple I mean. Surely running a luff wire down the luff and keeping it tight would work?