Square rig variation

An interesting interpretation of a Viking Ship

 

Camber Spar Dynarig

Im just reminded myself that I have yet to finish that 'bare bones' discussion and dwgs I promised quite some time ago.

But in the meantime I might bring to your attention this idea of incorporating Camberspars into a Dynarig configuration.
http://www.boatdesign.net/forums/motorsailers/dynarig-motorsailer-ala-maltese-falcon-16276-6.html#post376468

 

DynaRig Test Vessel

I have been looking ALL OVER the place for this photo of one the test vessels for the Maltese Falcon. I finally found it this morning....enjoy

 

Awsome prototype!

 

Nice pic, thanks Brian

 

Square Rig Pointing Questions

I posted a video presentation on the subject of square rig pointing capabilities over on this other subect thread:

http://www.boatdesign.net/forums/sailboats/square-rig-pointing-questions-5991-2.html#post537770

 

Stayed Dynarig

I had previously posted this reference discussion by Philip Goode on 'weatherly square riggers'.

Just today I ran across his discussion of a 'stayed dynarig':

Most practical proposals for sailing cargo vessels today are based on the Dyna-rig developed for that purpose in Germany in the 1960s and brought to outstanding culmination in the rig of the 2007 built Maltese Falcon. This rig is based on a rotating mast, the yards being fixed to the mast and rotating with it. This means that the masts had to be unstayed, leading to enormous cost not only in the bearings at heel and deck partners, but also in producing a spar strong enough to bear the bending load.

What brings Goode’s design into the realm of commercial viability is that, instead, it utilises a rotating mast stepped on deck and supported by wire rigging. The spar can thus be much lighter and, aside from a thrust bearing at head and heel, there are three simple bearing collars along the mast’s length. Practical experience of the 226gt sail training vessel Pelican of London has shown that lateral staying of the mast can be safely carried out by backstays which are anchored much further aft than usual and do not hinder horizontal yard swing until the yards reach 20º from ship’s centreline. Because none of these backstays hinder the yards, there can be as many of them as required. Even the conventional lower shrouds, which would normally be in the ship’s transverse plane, can be replaced by backstays to the lower hounds.

...more here...
http://www.motorship.com/features101/ships-and-shipyards/hybrid-square-riggers-the-ultimate-green-ships

 

It's nice to see this interesting thread come to life again. Have any of the participants gone ahead with building a dynarig or other square rig for a small boat?

I still have material and hopes to proceed with mine now my health is back again . . .

 

Hi Terry,
I am going ahead with the boat, but haven't really done any more work on rig design.

 

I was looking thru some subjects related to full battened sails and ran across this forum entry over on SailNet

 

I won't hold my breath any longer then . . .

I had a few more thoughts about the midget Dynarig scheme I posted earlier http://www.boatdesign.net/forums/at...ig-variation-sailingdirectlyupwinddynarig.jpg - rather than increase sail area to accommodate light airs I can add a few extra mast sections at the bottom of the telescopic mast.

They would not carry spars and sail like the upper sections, just enable the fully- or partially-extended rig to be hoisted to a greater height in light conditions, or when river banks or trees interfere with the wind, to catch a stronger breeze. My boat is very stable for its size and will handle the increased heeling moment, provided the skipper retains his hold on sanity in a breeze . . ..

It would be very simple to do and would not interfere with the rest of the rig. It would provide additional sail rigging options and reduce the effect of wind layering and compensate for the inability to twist this kind of rig.

When, you might ask? Yes, well, there's a backlog of projects . . .

 

tacking a single masted square rigger

Looking at how a square rigger tacks, I am thinking one will probably either need a jib to keep pushing the bow around - especially in a cat - or maybe att a second small mast for something akin to a square rigged ketch or even yawl.

the moment I am talking about is when the main and mizzen are already sheeted home and provide a forward force and the foremast is still backed, pushing the bow around. I foresee difficulties with a single mast, especially tacking in confined waters, where you won't want to wear.

 

Sliding, square ,dyna ,junk ?

A while ago I was looking at some videos of a model proa sailing with a Dyna rig, and was impressed, both with its ability to both shunt rapidly ,and to sail close to the wind. I thought that it might be beneficial to address the rigs inability to twist or feather, as well as it's tendency to oscillate without active control . It occurred to me that traditional junk rigs were similar and that by adjustment of the luff parrel the sail could be moved fore and aft changing the relationship of the ce and the clr, but also changing the rotation axis. I reasoned that with a sail that exchanged luff for leach , with the addition of another luff parrel on the opposite side of the sail , during a shunt the sail could be hauled so that it's axis of rotation would be in the most favourable position for balance and stability. I am still intrigued with the concept and have contrived a system that is probably too dependant on rig tension provided solely by the parrel lines that in addition must function as both reefing lines and down hauls. Significant mechanical advantage would be required to maintain sail tension if the rig could be made to work at all .and even if carbon were used for the yards it might be that the scantlings required to assure adequate stiffness impose a weight penalty that would render the concept impractical. Rather than try and describe the mechanism in detail attached are three drawings (not to scale) that illustrate how I think sail camber and draft could possibly be controlled. and a rendering of a proa from above that shows the rig with twist. I have also attached a very brief animation of the same concept altered to be similar to the Omar wing sail except with a Clark y section, in that the sail wraps completely around the yards.

 

The old square riggers allowed a lot of progressive twist in their rigs for one major reason.

The sails on top were a great deal smaller than those near the bottom.

The top sails were sheeted closer to the wind, so they would flutter first, giving the helmsman warning to steer down wind a bit.

The rudders on those ships were tiny compared to those on sail boats today.

If the helmsman didn't steer down wind a bit, in time, the whole rig could be 'taken a back' and the ship would be out of control.

The MALTESE FALCON doesn't have that hazard, as her yard angles can be quickly adjusted due to her automated sail handling gear.

I would worry about such a rig on a catamaran. If it were taken aback at the wrong time, it could easily capsize, due to the sails suddenly pushing backwards, while the hull is moving along quite quickly forward.

Another problem to consider is the mast will twist more at the top than the bottom, causing the lower sails to be 'sheeted' closer to the wind than the top ones, particularly in a strong wind.

The same is true if the sails are ever taken aback.

They concept for the 'dyna rig' came about in the 1970's. It wasn't actually built until carbon fiber spars became available.

The rig you have in mind seems fearsomely expensive and prone to mechanical break down and likely wrong for the type of boat you are considering.

What advantage do you hope to get from it over, say, a biplane Chinese lug?

 

I thoroughly agree with your observations and opinion and think the original quote was 'fewer strings', which means re-inventing the wheel because you don't like the tread on your tire. Here's a very traditional Chinese rig from a 'Big Eye Chicken' junk adapted to a western hull, the 40' yawl BERTIE. Having logged many thousands of miles at sea, her gear is well worked out since everything that hasn't worked well has been modified until it does, 200 miles offshore, at 2 am, in a gale, with an injured arm.....
I personally have a great deal of experience with square rig, both working in maritime museums and at sea, and think this whole idea is interesting, but ludicrously expensive and far too experimental to take to sea without the backing of MALTESE FALCON style. The Chinese rig on the other hand, has a very long history and many different guises, for vessels from light displacement to heavy. In other words, IT WORKS, and is not experimental. I like experimental, but not at sea when my personal life is at stake. Then I want something stone-age simple and so overbuilt it'll never break.
In the late '70s a couple of strange boats sailed out the Golden Gate laden with bibles to preach the gospel in the owners' idea of the world. One was a 36' steel lifeboat and the other a pod on pontoons. Both had a 2 masted rig like... hm how to describe this. There were curved yard/battens in front and behind the mast, joined on their outer ends. On this hoisting frame would be a 'square' sail (in that the wind is always on the back side of it) made of two actual sails, one in front of the mast and one behind, fastened to the curved battens by being in pockets, sewed together on the vertical edges, with a lot of camber in it. An ingenious idea really, but too small a sail area to really work well, and only worked over certain wind strengths. These intrepid missionaries got about 400 miles before the pontoon boat started sinking and its crew of 6 joined the others in the clumsy monohull, and then they called the CG, cost everyone a lot of money, and abandoned the two experiments at sea.