a ultimate MotorSailer idea, Dynarig motorsailer

Its tough to make a large catamaran aesthetically pleasing, and even tougher sometimes in the really big ones. I was always a fan of some of Peter Wormwood's work, which had evolved from Peter Spronks' work. This one was a favorite,..Indigo





...and some Spronk designs
https://www.boatdesign.net/threads/classic-catamaran.19366/page-5#post-336645

For the pure enjoyment of sailing I think there is nothing better than tiller steering, and that is even more difficult to experience as the boat size increases. I found as I got older that the smaller vessels with tiller steering were the more pleasureful. And to rig the boat where the forces of the rig allowed for a natural enough balance that would allow for that was challenging itself.

Anti-Capsize

It appears that HTMO9 is very concerned about the subject of capsize,...as have many multihull sailors since multihulls became increasing popular. I have been away from direct involvement with multihull design for a number of years now, so I am unaware of developments in anti-capsize hardware that likely has been in the works for a number of those years, particularly considering the large number of big foiling multihulls that have been racing the oceans. Surely these guys pushing these boats right at the 'edge' have developed some systems?....particularly the French sailors that seem so involved?

So I thought I would see what google had to offer, and this came up most immediately.

Anti-Capsize Technology and Systems
The purpose of this thread is to post systems available, discussions of the technology and reviews. This is a serious subject. Please back up statements with facts. Some systems monitor rigging structural condition as well so while most of these discussions might concern catamarans, owners of monohulls could be interested.

This one really caught my attention as it was somewhat like a rotating cleat system I employed long ago on the kick-up centerboards on the Lousiane 37 cat I imported, and our Firefly trimaran's centerboard.
ACS system
https://www.boatnews.com/story/29460/acs-an-anti-slip-system-for-multihulls
"Even today, multihull skippers still admit that they cannot do without it. At the start of this 2018 Route du Rhum, there are 9 boats equipped with ACS: both Ultimate and Multi50 (where this type of system is even made mandatory by the class). But ACS is also present on some boats entered in the RhumMulti category"
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This posting I started to agree with, BUT when I reread it a second time, I had problems with it.
"If you do get caught out, the least stress solution is to depower the boat completely, stop and quietly drift. Unfortunately, this is impossible with stayed rig multis. Dumped headsails and their sheets flog, shaking the whole boat, the mainsail gets pinned against the shrouds or flogs and steering becomes difficult as you have no speed, but must keep control. Any extras become a nightmare, especially if they don't furl properly.
These scenarios usually happen at 3 am with associated rain, change of wind direction and half asleep crew. They are rare, but only have to happen once to spoil your trip. What is not rare is worrying about them, which really should not be a part of an enjoyable cruise when the solution is so obvious."

You don't have to depower it totally,.. just reef it down to a safe size that is still balanced. That is what my 'mainstaysail' does. In the first place my aft mast rig is designed to carry the same sail area as a sloop that requires a considerable taller mast. My rig can be shorter to begin with, and even shorter at night, with just the simple act of rolling up that big genoa and sailing with the smaller, lower 'mainstaysail'.
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"I think the capsize of Anna is really instructive because it is an example of a large (57ft) well designed and built (Chris White) catamaran. The crew were doing things well up to the point they capsized. They were monitoring the weather by radar and using Mk1 eyeball. The great thing is that the skipper was gracious enough to write a journal about the capsize. I think the sailent points are in the paragraph attached."
https://www.cruisersforum.com/forum...hnology-and-systems-267200-3.html#post3663939

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I got a kick out of this one,..ha...ha
"Capsize is a risk with high performance. Just like crashing that new Lamborghini after it rains is a risk.

That’s what makes it fun.

I’d also rather have risk of capsize in the 2% of sketchy moments than wishing for more wind in 98% of my other time on the boat."

Kick-up Cleat
BTW, I saw a lot of references to some sort of kick-up cleat systems in the anti-capsize discussions.

This was the first one I used LONG ago for the kick-up centerboards on the Louisiane 37 catamaran and our 26 Firefly trimaran. I think it came from Germany?

https://www.boatdesign.net/gallery/pfeiffer-adjustable-tension-cam-cleat.4907/

Some Up-Side-Up installations on big French multihulls

Interesting how the sheet (line) seems to be 'captured' by that secondary winch in addition to the primary one,...so not all is totally lost on the headsail's re-sheeting

I found another old discussion i started on 'Capsize Prevention Devices'

https://www.boatdesign.net/threads/capsize-prevention-devices.41340/

Sailing with family and kids:

Sounds like you need something like this,...Douce France
https://www.sailingdirections.com/catamarans/doucefrance.htm

schooner rigged and LOTS of privacy in internal spaces, BIG saloon, lots of smaller water toys

some more pics of Douce France
https://www.charterworld.com/index.html?sub=yacht-charter&charter=catamaran-douce-france-961

Perhaps charter her one time, and see if see meets your needs?

perhaps Kajan can redesign her in a manner you would like

Dynarig support analysis

Just wondering who might have performed the analysis that the Dynarig could not work on a catamaran?

I went back and looked at the very thoughtful analysis the Shuttleworth did when he was designing the free-standing Aero-rig 52 catamaran. I patterned my design after his structural work.

I wasn't suggesting a single masted Dynarig for that 165' catamaran you were seeking, and certainly not a 150' tall free standing rig. And I don't think Kajan's twin dynarig had mast(s) near that height.

I added that 'dynarig support analysis' posting to this discussion just to say to some future reader that it was not going to be impossible to put a dynarig on a multihull, ...just likely impossible to put one on a much larger catamaran where the burial depth does not increase in proportion to size of the vessel.

Square Rig Variations

There was a period of time in the past when I was looking for variations on the square-rig theme. This little video (and some others that are no longer viewable) presented one of those variations,..
a youtube clip of a model proa with a Dynarig type sail on it.


How about scaling up this 'fenced yard' idea for a simplified Dynarig that would allow for hoisting and lowering the sail area (and yards) for various wind strengths?

I would divide my ‘concepts’ into two groups; 1) as simple as possible non-automated version, 2) automation and furling of the sail sections by mechanical or electrical means. In both cases I’ve sought to eliminate the need for ‘in-mast’ furling of the sails (MF). That requires a more hi-tech mast and practically dictates a carbon fiber mast.

For your project and this discussion lets just think about the most simple version of my thoughts,

I would choose to utilize an elliptical mast section, in fact likely an exaggerated one that might be fairly long for its width. You might find this type in an old ‘mast junk yard’, as a number of early alum-masted vessels tended towards this shape to minimize the aero disturbance to their attached mainsail. As a bonus this style tended to be rather heavy-walled, an advantage for the free-standing nature of the ‘variation on the square rig’ and/or the dynarig.

My yards would differ from yours in that they would be relatively flat plate ‘sickle looking shapes’ built to the idealized 12 degree arc curve. They would be one piece across the entire span and taper at the outer ends. They would be wide enough at the mast such that an elliptical whole cut into the yard would slide down over the mast,

My yards slide up and down the mast like yours. To facilitate this sliding I would utilize several possible materials. The least expensive one would be UHMW polyethylene. In a thin sheet form it could be wrapped several inches wide around the two ‘proud sides’ of the elliptical mast section and attached with countersunk screws. Sliding against this ‘mast surface’ would be ‘blocks’ of UHMW cut and fit to the adjoining hole in the yard(arm). This UHMW material is cheap, workable with std wood working tools, tough, slick, and sea-environment friendly. Alternatively, there is a more expensive sheet and block Teflon material that could be similarly fashioned.

NOTE: The alum (or whatever) mast with thin sheets of UHMW attached at the ‘pointy ends’ would be a relatively clean structure to the wind and to other rigging lines, etc, as opposed to ‘channels’ or a ‘rail’ projecting from the mast surface.

Each sail would reach across the entire span of the yard’s forward edge and attach to the yard via a bolt rope arrangement in a track/groove on the surface of the yard. The sail material could be extremely light-weight cloth as it is supported along the full two longest edges. Aerodynamically this gives a very clean outer surface to the aerofoil…the most important of the two sides. The inner surface of the ‘sailfoil’ is interrupted by the slim side of the mast at its center, but likely the airflow will re-attach to the inner curve of the sail’s inward arc…. (and helped by the end plate effect of the flat yards top and bottom).

The ‘flat plate’ yards need to be constructed of a very stiff material that will resist bending from their ‘arched shape’, and from their tips bending up or down. Their ‘sickle shape’ (top view) should help significantly with maintaining their arch shape. There will need to be a cross wiring of their tips to attachment points at their center reinforced ‘holes’ that surround the mast. This likely could be accomplished with small tough, pre-stretched spectra line. Not only does this keep the tips from bending, but also it contributes to the yard itself riding a straighter line up the mast and resisting cocking and binding.

NOTE: There would be the temptation to build too much vertical depth into the bearing/sliding material to prevent jamming of the yards as they slide up and down the mast. This should be avoided as too much depth could actually increase the binding when the mast itself bends slightly under sail loading. It would be better to have proper cross-wiring (bracing) of the yards themselves, then a two part halyard pulling on the top yard, and a proper two part restraint on the bottom yard in a reefed configuration. Too much depth in the slide bearing would cause additional problems with stacking the stored sail rig

reference discussions
https://www.boatdesign.net/threads/square-rig-variation.30031/page-2

Royal Clipper Uses Furling Square Sails,

https://www.oldsaltblog.com/2018/01...bvious-technology-behind-modern-clipper-ship/


Here is a look at a modern sailing ship, Star Clipper’s Royal Clipper, a high-tech square-rigger whose technology is not always obvious. Click here for a photo tour of the Royal Clipper recently featured in USA Today.

We recently posted about the high-tech three-masted square-rigger, Black Pearl, which features a next-generation Dynarig with automated sail trimming and furling. Flexible solar panels are also incorporated into the sails to help meet the electrical needs of the vessel.

Compared to the Black Pearl, the five-masted fully-rigged sailing cruise ship Royal Clipper looks almost entirely traditional. This is no accident. The Royal Clipper is modeled after the famous Flying P Liner, the five-masted ship Preußen of 1902.

According to the Guinness World Records, the 439′ Royal Clipper is the largest square-rigged ship in service, with 5,202 square meters of sail area (or almost twice that of the Black Pearl.)

The Royal Clipper sets 42 sails, set on yards and stays in what at first glance looks like a wholly traditional rig. In fact, it is anything but. The 26 square sails can all be set or furled from deck at the push of a series of buttons. The square sails are furled inside the hollow aluminum yards with a hydraulic roller furling system. The yards are trimmed with electric brace winches.

Furling square sails is not a new idea. Variations on the concept date back at least to at least 1861, with H.D. Cunningham’s Patent Self-Reefing Topsails. The advent of hydraulics, electric motors, lightweight spars and stainless steel cable, however, make it possible to fully automate the handling of the square sails carried on the five masts.