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Old 05-02-2009, 15:19   #76
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There has been talk about seakindliness to include comfortable motion, ease of reefing, safety and comfort, going forward for sail changes, even size of cockpit for partying. I would also include not being pooped, not having your mainsail hard against your rigging from a sudden bullet, sun protection and wind protection in the cockpit, little tendency to broach, being able to sail upwind in comfort.

Having an unstayed easy or aero rig reduces many of these hazards if on a multihull as you don't have to go forward for sail changes or worry about a roller reefing stuffing up and there is plenty of room to work on the main. If struck by a bullet or simply not reefing in time as you don't notice the wind building up going downhill, you can simply let go the sheet and the rig weather cocks.
A central cockpit avoids getting pooped and it can then be made reasonably large.



For the size I haven't come across a better motion than a Harryproa. Because there is no tacking, there is no need for rocker and thus can have a very high prismatic coefficient. It has extra long bows that slice through waves and gently rise rather than bouncing up and stalling the rig. Cockpit central and as the weather always comes from the same side, is nice and dry and little motion. No need for going out on a pitching foredeck as modifying sails is all done from the centre of the deck and the anchor can be set over the crossbeam and tied to a bridle. No worries about changing from a drogue to a sea anchor. It can all be done over the stern as it is truly double ended. No worries about being pooped as the cockpit faces to lee and is in the centre of the boat. Two rudders gives amazing manoeverability and along with the ability to easily reverse gets you out of all sorts of awkward situations and makes man overboard drills much easier (though the likelihood of needing them much less)

In cruising mode it can also do windspeed in 10 to 15 knots with ease and safety
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Old 05-02-2009, 15:44   #77
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Is it correct that the people who engage in this discussion on seakindlyness have an interest in ocean-crossing yachts? Is it also true that most cruisers are not sailing 50-60 foot yachts with a crew but single-handing or couples cruising on boats in the 30-45 ft. range?

Given those caveats, I would presume to define "seakindly" as a boat whose lines and form allow her to give to the stresses of sea and wind with a motion that is smooth, without jerkiness and remains somewhat predictable in a given set of conditions.

The biggest and most significant variable is the condition of the sea, as it is the waves that affect the kind of motion I'm discussing. How the waves hammer a boat's hull and create turbulence against the rudder, whether she lifts to a following sea, or surges into a trough, these are all design issues that affect the motion in the cockpit, on deck and while your'e trying to get some sleep below.

On a smooth bay, seakindliness isn't an issue. I don't think I would ever consider a boat that couldn't heave to in a gale to be "sea kindly." As to what makes one boat behave well when others are behaving badly, ask the naval architects. I know that I can look at a boat out of the water and "see" where her problems will lie. Beautiful curves present a surface that disperses the force of the waves.

Bob Perry could speak to the physics of drag, water weight, righting moment and so many of the variables that affect a design--the equations that allow him to see how a boat will behave. Any one who's interested can read books on the subject and see how their boat measures up to the criteria.

If you spend time in the cruising crossroads: Panama, Tahiti, Durban or Capetown, you can take your own survey of which boats are rough on their crews and on which boats the seas have been rough. There are boats you will never see in South Africa or Australia because they sea won the bet long before they got that far. Lots of wives and crew jump ship in Panama. Boats get shipped back from Tahiti. There's a lot of atrition. But there are other boats you see again and again with happy crews who sail safely and with reasonable comfortable. I think they would
call they boats "seakindly."
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Old 05-02-2009, 16:07   #78
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Very nice. Now can you put that in objective terms?
Just for the sake of argument. Sometimes it's best to define one's terms just so we can all speak the same language. I'm just asking.

Amgine:
I suspect you may be on the right track.

Robert:
You seem to be a zealot for proas and I can appeciate the thought you have put into the subject. We can talk about usable interior volume of proas later. But for now, how big would a proa have to be to have the usable interior volume of a typical, 40'LOA, moderate displacement monohull cruising boat?
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Old 05-02-2009, 16:20   #79
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:: Points again at Marchaj:: I believe someone has already done so, better than I could. The title, iirc, is Seaworthiness: The Forgotten Factor, and covers such details as the US Navy's studies regarding sea sickness, motion accelleration, and other elements of seakindliness as intrinsic to the concept of seaworthiness.

I also think I recall correctly that you have a copy on your shelves, but not in your office.
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Old 05-02-2009, 16:57   #80
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Seaworthiness is a laudable attribute, but it is not seakindliness.

Seakindliness can aid seaworthiness by helping the crew from being more fatigued than necessary, but the two remain separate concepts. A seaworthy boat can be an unkindly sea boat. She'll get you home, even if you never want go out with her again.

Seakindliness cannot be defined in objective terms because it's too complex and it's analog, a sliding scale with no definite line crossed when you have it. Lady Circumnavi has described what a seakindly boat does.

Define a beautiful boat, in objective terms. Can't be done. Too complex. The exercise is futile. You can describe, but you cannot define beauty.
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Old 05-02-2009, 17:07   #81
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Bob,

are there .... " objective terms" that aren't formulas and drawings?
for example...Is jerky motion an objective term? Is heave-to-able? ...

Or does the language already exist...like...Righting moment and Displacement etc ?

I guess, what I keep returning to, is that...The boats exist out there that people feel are sea-kindly...Lady, can you name the boats that you see again and again with happy crews?

Good designs evolve through trial and error....the errors die off.. the successes live on...and hopefully get improved upon, tweaked...So what are the enduring successful Sea kindly boats out there..? What makes them so? What would make them better?

I'm reading a cruising guide for the Caribbean...the author says..to cruise the caribbean..."you need a powerful hull to punch through the seas.."

So would my Sabre 34 ..not be up to the task.?...Do I need another Boat?!!!
I think these are the questions most of us ask...? What boat do I need to head offshore..and have one of those Happy Crews Arriving.........I'll await the Beer and Rum Jokes..
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Old 05-02-2009, 18:02   #82
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Quote:
Originally Posted by bob perry View Post
Very nice. Now can you put that in objective terms?
Just for the sake of argument. Sometimes it's best to define one's terms just so we can all speak the same language. I'm just asking.

Amgine:
I suspect you may be on the right track.

Robert:
You seem to be a zealot for proas and I can appeciate the thought you have put into the subject. We can talk about usable interior volume of proas later. But for now, how big would a proa have to be to have the usable interior volume of a typical, 40'LOA, moderate displacement monohull cruising boat?
Rare Bird
Visionarry Cruiser Specifications:
Leeward hull length: 15 m / 50'
Windward hull length: 10 m / 32'8
Beam: 8.3 m / 27'
Empty weight: 3.0 tonnes / 6,720 lbs
Payload approx: 1.7 tonnes / 3,808 lbs*
Sail area: 72sq m / 774 sq ft
Draft: Rudders Up 400 m / 1'5"
Draft: Rudders Down 1.5 m / 5
Righting Moment: 18 tonne metres
Berths: Master Cabin 1 x queen size, Second Cabin 1 x queen size, 1 x single in the windward hull; 2 x pipe cots in the leeward hull; also the option of converting saloon table to double berth.
The Visionarry sport is 800kg lighter. These are measured weights. Empty weight includes rig.
Some of the weight of Rare Bird is the dinghy ramp which can very nicely be turned into a swimming platform. Ther is also loads of deck space
There are some videos of Rare Bird doing wind speed in 10 and 15 knots in extreme comfort. YouTube - Visionarry Sailing.
The mast is probably a little flexible for the weight of the boat but the owner wanted some extras through the build and added a bit more weight than originally designed for.
The free standing mast means that in gusts the upper section of the sail spill in the gusts
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Old 05-02-2009, 19:26   #83
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I suddenly realised that this was a mono thread. Sorry to have hijacked
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Old 06-02-2009, 07:28   #84
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Robert: Your contributions are valuable. I'd prefer you to stick around. Is there a link where we can see a dwg of that big proa?
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Old 06-02-2009, 09:19   #85
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Originally Posted by Robertcateran View Post
I suddenly realised that this was a mono thread. Sorry to have hijacked
So what, love that proa.
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Old 06-02-2009, 21:06   #86
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Thanks for the invite.
Check out Harry.com. It is a little behind but has lots of construction pictures from frames to sailing for some of the boats including the boat on the video. (And even a picture of me working on the female moulds for the 7.5m 5m version.) There is also the Harryproa yahoo group with more up to date material. Hopefully Doug on Sidecar will keep us up to date on his journey half way round Australia.

One interesting aspect that I feel adds to comfort at sea is being able to reduce rigging in a blow and to have low windage rigs. The 12m/7m trailerable racing model being built in Chicago for the Chicago-Mac race is designed with a telescoping wing mast. Details are in the latest newsletter on the website. The boat is designed for easy and quick building rather than looks. A single panel does for half a bottom and most of the sides with no cutting and shutting. The compound curvature at the lower part of the bow is taken up by having a couple of collision bulkheads and filling in with carveable foam. This gives good protection from running over things (and imagine the reduction in fairing time). I reckon its looks would be improved with a reverse stem and the motion marginally improved

Imagine cruising along and a cyclone warning comes up. You find a shallow mangrove Creek, telescope in the beams, telescope down the mast and tie yourself in. You could easily remove the mast completely and lash it down in the mangroves. I reckon that would certainly be a good claim for improving motion, rather than being out in it.

Leeward hull length: 12 m / 40'
Windward hull length: 7 m / 24'
Beam: 6m/20' telescoping to 3.7/12'4"wide for marinas and 2m/6'8"
wide on the trailer.
Empty weight: 420 kgs
Payload approx: 330 kgs/726 lbs with overload capacity of another 330
Sail area: 47 sqm/505 sq'
Draft: Rudders Up 200 m / 8"
Draft: Rudders Down 1m/40"
Righting Moment: 2.1 tonne metres

The boat should handle chop and swell, motion being damped with the long skinny bows and no rocker or flare. Maybe a bit light on stores for a Pacific crossing but you wouldn't need to be at sea for long. It should go to ww well with the efficient low drag rig and good foils and not losing drive through excessive pitching.
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Old 08-02-2009, 07:13   #87
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Thanks for the invite.
Check out Harry.com.
that should be harryproa.com

regards,

rob
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