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Old 19-03-2008, 03:51   #46
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G'day Alan. Firstly, she isn't my boat, but a good friend's. I'd say we were probably just a little under the design displacement, maybe 4 tonnes. I was very impressed with how she sailed too.

For my build, (photo's here: http://www.cruisersforum.com/gallery...00&userid=3477 ) I got composite staunchions, rudder posts and tubes from:

Steve Holdway
Exel Composites Pty Ltd
15 Ada Street, Coopers Plains, Qld., 4108
Phone: +61 7 3274 1099 Facsimile: +61 7 3274 2041
Web site: www.exel.net - Exel Group

(I have no connection to this business)
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Old 19-03-2008, 04:10   #47
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Gideon


OK - I'll come clean; I want the Harry with the same comfort and safety as the FastCat - but cheaper and sooner. It'll be impossible but I'm very interested in what a compromise might look like.
G'day,
Why impossible?

A harryproa is safer than a cat.

There are 3 types of comfort on a boat.
One is the motion. harryroas pitch, heel and corkscrew less than cats.
Two is the quality of your surroundings (air conditioning, plushness of furniture, etc). Money will decide this.
Three is all the little things like not having to go up and down stairs to get to the toilet, not having to clamber into bed from the end or over your wife from the side, having a self depowering rig so you don't have to reef so often, not having to go on the bows to change headsails or lift the anchor, being able to see where you are going from the cockpit, sailing or lounging outside in the shade while staying dry, a dining table with proper chairs and accessible from all sides, all your living space on the same level. All of these are done better on a harryproa than a cat unless the cat is 60+'.

Discussion of any of these points is welcome. Any that aren't obvious, please say so and I will give details.

I can't think of any compromises. It will be a lot cheaper and probably available sooner.

regards,

Rob
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Old 19-03-2008, 05:14   #48
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comfort formula

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Originally Posted by Rubicon View Post
Alan - the formula is

MCR = Disp / (2/3*((7/10 * LWL)+(1/3 *LOA))*Beam4/3)

It's not my formula but one I found at US Sailing Course and Online Sailing School
I have no idea on what basis this formula is justified. It says a heavier boat and smaller is more comfortable. I am not sure which numbers are scalar multiplication and which are powers, but even with all possible permutations, still can't make sense of it.
Much of comfort depends on avoiding hobbyhorsing plus yawing, and the different length hulls and high prismatic coefficient, with the relationship to the driving force give it the flattest ride of any boat I have seen for its size.
It makes more sense to look at the result and contrast the movement of equivalent boats,
Robert
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Old 19-03-2008, 05:39   #49
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From Ted Brewer, creator of the Motion Comfort Ratio:

COMFORT RATIO (CR): This is a ratio that I dreamed up, tongue-in-cheek, as a measure of motion comfort but it has been widely accepted and, indeed, does provide a reasonable comparison between yachts of similar type. It is based on the fact that the faster the motion the more upsetting it is to the average person. Given a wave of X height, the speed of the upward motion depends on the displacement of the yacht and the amount of waterline area that is acted upon. Greater displacement, or lesser WL area, gives a slower motion and more comfort for any given sea state.

Beam does enter into it as as wider beam increases stability, increases WL area, and generates a faster reaction. The formula takes into account the displacement, the WL area, and adds a beam factor. The intention is to provide a means to compare the motion comfort of vessels of similar type and size, not to compare that of a Lightning class sloop with that of a husky 50 foot ketch.

The CR is:
Displacement in pounds/ (.65 x (.7 LWL + .3 LOA) x B1.333)

Ratios will vary from 5.0 for a light daysailer to the high 60s for a super heavy vessel, such as a Colin Archer ketch. Moderate and successful ocean cruisers, such as the Valiant 40 and Whitby 42, will fall into the low-middle 30s range.

Do consider, though, that a sailing yacht heeled by a good breeze will have a much steadier motion than one bobbing up and down in light airs on left over swells from yesterday's blow; also that the typical summertime coastal cruiser will rarely encounter the wind and seas that an ocean going yacht will meet. Nor will one human stomach keep down what another stomach will handle with relish, or with mustard and pickles for that matter! It is all relative.

Goto “Ted Brewer Presents A Primer on Yacht Design”
Ted Brewer Yacht Design
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Old 19-03-2008, 08:03   #50
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I can see some value for a monohull, but not much for a multi as the beam implies beam of a hull rather than beam of a boat. There is nothing about the effect of prismatic coefficient in sailing comfort, nothing particularly relevant about overhang, and nothing about distribution of the mass. I feel the proof of the pudding is looking at boats such as Sodebo or Rare Bird as to flat comfortable sailing at moderate speeds. A formula that predicts the comfort of a multihull in various seaways would be an interesting exercise
Robert
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Old 19-03-2008, 09:31   #51
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Here's a very short video I took on an Oram 38 "Mango" sailing at 12-13 knots in around 15. Not quite 100% TWS, but not far off. The boat was quite heavily loaded
Dang, she sure scoots! Goes to show you don't have to spend $1,000,000 for a cruiser that performs. Kudos to Bob Oram.

MIke
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Old 19-03-2008, 13:38   #52
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Rob

Thanks for the reply – I would be interested in seeing the 60’ design. My email address is d.quixote@ntlworld.com.

A short mast on the ww hull does seem to make good sense but I noted Gideon commenting on his experiments with the Fastcat that reported; better generation on top of the mast, lower noise and less likelihood of a bird fouling the system up. Not too sure about the last point – I’ve often seen a bird perched on the top of a main. Perhaps a folding ww mast is the most sure way of addressing the issue.

I hope you’re successful in finding a yard. Once you do could you keep me posted? I expect others here will also be interested.
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Old 19-03-2008, 22:16   #53
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Harryproas and big waves?

I love Rob's creativity and daring, but the concept as executed to date makes me uneasy in 2 ways - those low bows and low rudder quadrants at the end which is currently the bow. I see videos of these proas having a great time in sheltered water-I just saw the video on Youtube.com - and they were sailing at high speed in perhaps 2' seas. I wonder how these low, fine bows and these low steering quadrants would perform surfing down 12 to 25 foot waves-both of which I have experienced. 12' waves are commonplace in trade wind zones, and they get steeper and shorter in channels between islands in the trade winds.


I see these low, fine bows as having a real possibility of burying and causing pitchpoling. Indeed, Rob wrote of pitchpoling one in a harbor once, without the aid of big waves. Further, I visualize that horizontal rudder structure being ripped off either running hard in big waves or in beating to windward in big waves.


To me, Harryproas come across like fast motorcycles - fun, sporty, light, with little carrying capacity, and maybe much more likely to take a spill than a car. Some may take these comments as a criticism, but aren't intended as such. To make an analogy-I don't see why sailboats shouldn't run the gamut from bicycles and motorcycles, through sedans, to trucks and SUVs, just as wheeled vehicles do.
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Old 20-03-2008, 01:56   #54
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I love Rob's creativity and daring, but the concept as executed to date makes me uneasy in 2 ways - those low bows and low rudder quadrants at the end which is currently the bow. I see videos of these proas having a great time in sheltered water-I just saw the video on Youtube.com - and they were sailing at high speed in perhaps 2' seas. I wonder how these low, fine bows and these low steering quadrants would perform surfing down 12 to 25 foot waves-both of which I have experienced. 12' waves are commonplace in trade wind zones, and they get steeper and shorter in channels between islands in the trade winds.
Thanks for the compliment. Harryproa design is not daring, it is logical. If you start with a cat or a tri and remove everything that makes them slow and expensive, you wil end up with something very similar.

The bows are low compared to catamaran bows as they do not have to keep a forebeam clear of the water. They are high compared to trimaran bows. They are fuller compared to both. A Corsair 36' tri has 36" high float bows and weighs 2.5 tonnes empty. This is between the two 50' proas currently sailing which have 40" high bows, which are much fuller (higher prismatic), are further away from the rig which is smaller than the tri's. The tri is also slower, more expensive and less roomy.

Yesterday you were telling me the hulls were box like, today they are too fine. Make up your mind. Thanks for sharing your experiences. I have raced half a dozen Sydney Hobarts, so know a little bit about big waves.


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I see these low, fine bows as having a real possibility of burying and causing pitchpoling. Indeed, Rob wrote of pitchpoling one in a harbor once, without the aid of big waves. Further, I visualize that horizontal rudder structure being ripped off either running hard in big waves or in beating to windward in big waves.
Jeeze, you are getting as bad as your silly mate (Catty) with the out of context quotes. I have also pitchpoled a Tornado, does this make your big cat prone to pitchpoling? The boat I pitchpoled can be seen at harryproa/elementarry sailing photos where it is being sailed conservatively (first sail) in lightish air by two people. The day I pitchpoled, it was 25 knots and I was solo, pushing the limits to see what it would take. It took a lot. It was possible to immerse the hull back to the beams and still recover with a small ease of one of the sheets. It was also perfectly maneuverable as long as there was enough rudder in the water. No bow steering. I have not pitchpoled it since.

The rudders work well. The first ones needed some beefing up, they are still draggy, but it would take a lot to break them. I have since designed new ones which mount on the beams. They have been trialled on my boat and a set are currently being built for the Dutch Visionarry. Once they have been tested, they wil become the standard.


Quote:
Originally Posted by BigCat View Post
To me, Harryproas come across like fast motorcycles - fun, sporty, light, with little carrying capacity, and maybe much more likely to take a spill than a car. Some may take these comments as a criticism, but aren't intended as such. To make an analogy-I don't see why sailboats shouldn't run the gamut from bicycles and motorcycles, through sedans, to trucks and SUVs, just as wheeled vehicles do.
If comparing a family cruiser to a fast motorbike isn't criticism, I don't know what is. I strongly advise you to go for a sail in one before setting yourself up as an authority. If you are smart, you will do so before spending any money on the junk rigged cat. Persuing your analogy, Harrys combine the speed and handling of a sports car (have another look at the video) with the space and comfort of an rtv at the cost of a family sedan and the safety of a tank. There is far less chance of a harryproa taking a spill or any of the crew being injured than on any cat with more than half it's performance. They also have huge carrying capacity if that is what the owner requires. The one in the video is fitted out for long term coastal cruising.

Rubicon,

Drawings sent today, the difference in generation between the top of the mast and 10' above the windward hull are negligible, especially when sailing. Noise is much less of an issue on a harryproa as the generator can be further away from the crew. If cats had any deck space not adjacent to the cockpit they would use it for a stub mast. Will certainly keep you posted on build progress.

44' cruising cat.

Nice video, you got any more? Bob and I go way back, he is the cat designer closest to my philosophy and a nice guy as well.

Gideon,

Quick note on the weights and sail areas. You use a harryproa weight of 5,000 kgs, of which 1,500 is payload. The Dutch one weighs 2.2 tonnes in sailing trim, so the weight would be 3,700 not 5,000, and 72 sq m of sail. Therefore there is 22.5 sqm of sail per ton, not 12. And compared to the Fastcat's ratio of 17, it explains why harryproas sail at windspeed so easily. The flexible rig allows them to do this safely, and with less stress than a stayed one.

regards,

Rob
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Old 20-03-2008, 02:16   #55
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Hallo Rob

I understand the ducht one is an almost empty hull but if one is used for ocean cruising it cannot be empty and items like a watermaker more battery power life raft dingy etc will have to be included. Our FastCat 435 in its bare weight of 5500 kilo,s includes all themse items and more . in this weight it is ready to do a circumnavigation and I feel with yachts in the sizes of 40 ft and up, these items need to be included to make them complete.
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Old 20-03-2008, 05:40   #56
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Originally Posted by BigCat View Post
I love Rob's creativity and daring, but the concept as executed to date makes me uneasy in 2 ways - those low bows and low rudder quadrants at the end which is currently the bow. I see videos of these proas having a great time in sheltered water-I just saw the video on Youtube.com - and they were sailing at high speed in perhaps 2' seas. I wonder how these low, fine bows and these low steering quadrants would perform surfing down 12 to 25 foot waves-both of which I have experienced. 12' waves are commonplace in trade wind zones, and they get steeper and shorter in channels between islands in the trade winds.


I see these low, fine bows as having a real possibility of burying and causing pitchpoling. Indeed, Rob wrote of pitchpoling one in a harbor once, without the aid of big waves. Further, I visualize that horizontal rudder structure being ripped off either running hard in big waves or in beating to windward in big waves.


To me, Harryproas come across like fast motorcycles - fun, sporty, light, with little carrying capacity, and maybe much more likely to take a spill than a car. Some may take these comments as a criticism, but aren't intended as such. To make an analogy-I don't see why sailboats shouldn't run the gamut from bicycles and motorcycles, through sedans, to trucks and SUVs, just as wheeled vehicles do.
I also have had a fair idea of what a wave looks like after many years commercial fishing off the coast of NSW, down to Tassie and across to the great Australian Bight as well as big wave surfing on and off for over 40years. I have a pretty good feel for how a boat behaves when it is in those conditions.
The stress on the rudders quadrants from the sailing loads is orders of magnitude greater than that from splashing through the water. There is less chance of problems with these rudders when they are set up right as they can release if they hit anything.
Sodebo didn't seem to have too many problems with the bows, so I don't see why a Harry should. They are a lot more forgiving to running into the back of waves than lower prismatic bows with flare. My experience with a bow bulb on a small tri in Torres Strait and observations of a power fishing cat in Bass Straight convinced me of the importance of low down bouyancy forward when keeping stable in tidal races and overfalls. I suggest you do the relative stabilising torque calculations of bows such of these compared with boats of finer bows and flare above, especially considering the extra length relative to the weight.
I have given my not so humble opinion about this in other threads. Consider the dynamics of a flatter riding vessel where the bows pick up the wave at least a couple of metres earlier than similar weight cat, giving good hydrostatic lift, and giving a smooth rise. Compare with a bow down boat (as there is insufficient forward bouyancy) suddenly hitting the back of the wave, dramatically increasing the width of the bow. The bow will either bounce up and the boat will stop suddenly, increasing apparent wind or plow in and not be able to rise easily because of hydrodynamic resistance.

I do not feel you have made any sort of case of the boats not being suitable for offshore use
I would feel much safer on any of the Harrys compared with the commercial fishing boats I worked on and would be a lot more comfortable with faster passages,
Robert
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Old 20-03-2008, 06:55   #57
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Comparing proa (lopsided catamaran ) to catamaran

Mark stephens (robs right hand man) puts forward a few of his thoughts on the subject.
quote
"Where a proa saves weight is in not having so much material as they don't have such an extensive fitout, and not so much solid bridge-deck and saloon. I think a proa built with the same accommodation and appointment as a cat will weigh about the same. Where a proa gets it's performance is in the extra waterline length. It's pretty pointless comparing proas with cats as they are such different beasts fulfilling different rolls." unquote

So when mark speaks of performance he's comparing what to what. For a boat thats never lined up against anything else to prove its performance, other than in robs mind there seems to be a lot of long bows drawn.

Surely with all the accomodation jammed in one hull, it would be more meaningfull to compare it to a 10m mono?
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Old 20-03-2008, 07:00   #58
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Exercises in sophistry are right up there with parliamentary debate as meaningless pointless wastes of time. I am sure I can find quotes by catty's right hand man - JOLI that will defeat catty's line of argument or at least undermine Jolis lines of argument.

What precisely is your point here -
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Old 20-03-2008, 13:46   #59
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I am not "making a case" that Harryproas are dangerous offshore, I am expressing a concern. My concern is not dispelled-those bows look very fine and very low to me. Rob misunderstood my comments and decided that I had said his boats were 'boxy.' I didn't say that, and I didn't mean that, but some people will hold onto a grudge, even when it is founded on a misunderstanding. I think it is fascinating that his proas perform well with prismatic coeffecients of .8, and I feel that Rob has made a contribution to yacht design by discovering this. What this means to me is that the more slender a hull, the higher a prismatic can be without harm to its sailing characteristics. I don't disbelieve anything Rob says about his experiences, but when it comes to predicting future performance, for example, surfing in big waves, we are all merely speculating. I wonder if Rob will tell us just how big a proa of his design would have to be to carry 149 passengers, with six completely private compartments, four of which are doubles, and four private heads and showers? My design isn't junk rigged, exactly-It has a wing sail which looks very much like a drawing by Tom Speers of a very efficient wing shaped mast and sail. See Aerodynamics of Teardrop Wingmasts
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Old 20-03-2008, 15:20   #60
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I wonder if Rob will tell us just how big a proa of his design would have to be to carry 149 passengers, with six completely private compartments, four of which are doubles, and four private heads and showers?

I think you might have the wrong guy for that setup. For that kind of capacity i would reccomend checking these designs:

Incat Home

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