Proa design

Discussion in 'Multihulls' started by Tcubed, Sep 13, 2008.

  1. rwatson
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    rwatson Senior Member

    I could say good luck, but its the silliest idea I have seen.

    Thats what I meant by most Proas are designed with egos - not good design principles.

    Oh well - keep the proa flag flying Rob.
     
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  2. Tcubed
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    Tcubed Boat Designer

    Please define "silly". Are you saying Russ's design's are "silly" too? He uses a very similar rig configuration.
    I don't see the ego connection either. I just think that the advantages of a proa outweigh the disadvantages for my particular needs. You see, as i've already explained, i don't mind a boat that is a bit more work to sail than other's if it gives me other advantages.
    Ever heard of the dipping lug? For centuries this was one of the most favored rigs by the Scots, Irish, and Bretons. Ever tacked a sixty ton dipping lug schooner? Yet those old boys did it every day in every season of the year. I don't think they were silly, they obviously had their reasons. After all they could just use the gaff sail and tacking is a whole lot easier. But the dipping lug is one of the most efficient sails (and still is) and they knew it. So like me they were prepared to put in a bit more effort to get a bit more speed. To shunt a proa is child's play in comparison.
     
  3. rwatson
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    rwatson Senior Member

    Purely in the spirit of stretching some design ideas here, and not trying to rubbish you, I'll do the right thing and explain my terse comments.

    1) As soon as you mention "heavy, hard, tricky" in the operation of a proa you lose me. I dont think this needs to be the case, and the fact that your rig will be hard to shunt makes it much less attractive for you and others to use. No matter how tough you are, after 3 weeks at sea, I am sure you will agree.

    2) In high winds optimum sail performance in a Proa is not a big concern. Your biggest problem is keeping the boat upright - the sail will can produce more power than you will need. Dipping Lugs will produce a lot of power in a decent wind - they were designed to drive heavy, cargo laden monhulls at under 12 knots. In light winds, they are bad performers. You need to generate lots of lift with well shaped sails. When the apparent wind goes forward, and the hull gets into the low teens of speed, the lug sail plan is super innefficient. I havn't seen a lug sail on a cat since the first experimental cats appeared on the Thames in the late 1800's.(No, I wasnt there, just saw the pictures :) )
    I feel you need to consider a much more aerodynamic sail plan.

    3) The hull layout - without detailed plans, it appears the ama is way too close to the main hull. Since it doesnt put accomodation or control out where the weight is needed, it will either need artificial and unneeded ballast, and/or putting all your stores in hard to get at locations.

    4) Your daggerboard and rudder configuation appears excessive. Rob Denney controls 33 foot of proa with two rudders, and doesnt need to think about shifting 3 or 4 boards. (by the way, I cant see any rudders on your plans, but lets take them as read)

    5) It looks like the boards in the main hull will impede the sails when raised.

    6) There is little all accomodation on a boat that will be "doing long trips with few tacks". What accomodation you can put there will get mixed up with sail controls. Even if you stick to the tropics, shelter from the elements is a big thing.

    I would strongly disagree with your intial comments "most production boats nowadays have grave performance and seaworthiness issues". I think you are starting from an incorrect premise.

    Consider, there are more production boats scooting around the world, wasting money and stuffing up the environment than at any time in history. The few wrecks and crashes that make it to the news are few and far between.
    Modern designs on the whole are very seaworthy and great performers.
    If you ever try to insure that proa design - you will find that Insurance companies are very sensitive about this sort of thing.

    It would be great to get you into a really good Proa, and start the revolution to civilised sailing machines, because they really are the most sensible design as you very rightly pointed out.

    I hope some of these comments make sense, but hey, feel free to debate any and all points. Whats a forum for eh? :) Viva La Debate!
     
  4. rob denney
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    rob denney Senior Member

    G'day.

    RWatson, Thanks for your support. Everything you say is on the money except all my boats use only two rudder/leeway preventers. More than this just adds complexity, cost and drag, You can see an old version of the 2 rudder set up in the video at http://www.youtube.com/watch?v=8chR6DAFjGA. This 50'ter/15m weighs 3,500 kgs/3.5 tons ready to cruise. It is almost twice the weight of the standard version, one of which regularly takes sight impaired people sailing in Holland http://www.harryproa.com/BlindDate/Jan_9.htm. Both boats have 2 big double bunks, covered cockpits for 8 people and all amenities.

    Tcubed,
    You may have reached the same conclusions as me, but your implementation of them is very different to mine. Your boat looks like a copy of Russ Brown's work.

    I have regularly debated the Russ Brown vs harry style of proa on the Yahoo proa-file list for the last 5 years or so. I suggest you look through those archives if you are interested in improving your design. You should also contact Russ and get his opinions on the boats.

    Couple of opther points:
    Shunting a harry is easier than tacking an overlapping headsail boat and easier and safer than gybing any boat.

    Headsails (apart from those on ballestron rigs) are hard work on proas. See the shunting video at http://www.wingo.com/proa/brown/video.html#video. This is the one at the bottom of the page, the other one shows how much these hull shapes hobbyhorse.

    Accommodation in the lee hull is wet and in the wrong place on a boat with limited righting moment.

    Leeward pods are weight in the wrong place, involve large hull cut outs in highly stressed areas, excess drag and unless they are set high will have the same affect on stability in extreme conditions as small lee hulls on old trimarans.

    Proa resale value is poor for 2 reasons:
    1) there are so few of them sailing. This will not change until more boats are out there sailing. This may not be so far away. The third 15m/50' harry has just been launched and the first has just been sold (first owner died just after the launch). I have just sold the 38th set of plans, the largest of which is 66'/20m. Almost half of these have been started in the last 12 months, and there is now some interest from a cruising version production builder, so maybe things are picking up.

    2) Russ' boats have had some diabolical press from people who have sailed on them.

    I am happy to advise you on your boat regardless of what design you finally settle on. But the best advice you will receive is to build a smaller one first so you can find out all the things that are wrong before it costs you a lot of time and money to fix them. I have built half a dozen prototypes. The first had a lot in common with yours. It was rapidly superceded.

    regards,

    rob
     
  5. Tcubed
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    Tcubed Boat Designer

    Alright, that's more like it!

    First i regret not having started out a little more precise with my topic objective. The design in this case is purely for me (selfish *******, heh?) and my top design priorities are performance in as wide a range of conditions and seaworthiness. Seaworthiness, by the way, i think is best defined, as retaining full control of the craft in all weather conditions.. The rest is low on the list of priorities apart from relative ease of construction.

    1* If i could think of an easier way to arrange things for shunting i would. Harry's system is a marvel of ease of operation, but i have certain reservations about the aero rig. Firstly unstayed masts on a multi has never made engineering sense to me (on a mono, yes, unstayed is great) as the the multi's are so stiff, and why throw away that huge staying base? With a couple of lightwieight wires the mast can be suddenly much lighter. Of course the aero rig can be stayed. So maybe i should consider it. It would eliminate the dump one jib, raise the other, portion of the events, a considerable savings in effort.

    2*I'm sorry to have confused the issue with my analogy with the luggers. It was only meant as an illustrative example. My proa will not have a lug rig. What you're seeing is a fully battened gunter rig, which as far as handling is concerned is pretty similar to a marconi sail. I must however disagree with your statements on the lug rig. It is a superb airfoil at all angles, and works very well in light airs, but that is definitely a topic for a different thread.
    I must say i don't understand why you say rig performance is not so important in high winds. I would say that that is when it is the most important, as the hull windage cannot be reefed, its contribution to the total aerodynamic forces becomes ever greater as the winds increase and one reduces sail correspondingly, eventually making the boat unable to make good to windward. This ceiling on +ive VMG i feel is very important to have as high as possible for seaworthiness.

    3*Here i need to explain the drawing better. The way i see it, the only way a proa will have superior performance to a cat is if the windward hull is the heaviest, therefore i have all the stores in the ama-Drinking water, food, clothes, tools, gas for cooking, batteries and solar panels, spare sails, books, bicycles, the tender, as well as water ballast tanks for trim. The main hull must be buoyant so it makes sense to use that one as accomodation. The ama does not have to be buoyant so it can be reduced as much as possible to reduce windage. It still has enough reserve of buoyancy to not get pushed under if caught aback. In the main hull, there would be a minimalist kitchen at one end with enough food for three days or so and a simple desk at the other. Sleeping is in the wing, or sponson. People are light, cargo isn't. Every few days one would go across to the ama and open the apropriate watertight hatches and get more supplies, exchange books, whatever. The water, gas and electricity gets piped across. Harry has both accommodation and cargo in the windward hull which is even more optimized. Although the cargo removes some of the living space but one's stuff is conveniently at hand. Pros & cons.
    The leeward hull should have plenty of flare so it resists immersion strongly and plenty of volume in the bows, so its volume really lends itself to living in, i think. Excess volume in the windward hull is pointless-might as well just go back to having a catamaran-and possibly dangerous. A high windage ama can flip you over if you allow it to fly too high and could turn you the wrong way if lying a-hull. With my design, i can leave it drifting and with all the windage on the leeward hull, i'm confident it will stay where it needs to be; to leeward.

    Having said all that I take your point about hull separation. Right now it's 6M and lenth WL ama 15M and about the same for the main hull. I want to have a pretty high factor of safety against pitchpoling but no doubt i could as you say make it wider. Just how wide is optimum?

    4*There are three boards, one amidships in the ama, and one at each end of the main hull which contain the rudders. The midships board is used for balancing and beating: upwind down (clr forward) then progressively raised as the wind frees (clr moves aft). The bow board does nothing till it's needed again. The aft board is all the way down whenever it is used, with its rudder, which can be hooked to a windvane. (the windvane would be set out in clean air on the ama).

    5*No they don't, they're to windward of the jibs.

    6*I don't quite understand what you mean. In my sixty thousand miles bluewater experience, i found that the vast majority of my time was spent belowdecks. Why be outside, where the sun beats down ferociously, the tireless breeze buffets one around and just when you're starting to dry another blast of spray crawls under one's oilies, when inside it's all calm and peace? I would pop my head out every little while, check the horizon's clear and get back to my book or radio show. If the wind changes, i adjust everything and get back inside. The only other time i'm outside is to take the sextant sight.
    I plan on also having a number of hatches where i can steer and trim sails from but have half my body inside. For shunting and reefing or sail changes i must go out completely, of course, that's what oilies where made for.
    I'm also hoping the flare on the main hull will make that hull pretty dry, although no doubt when the ama's bow catches a wave that will send serious spray blowing across to the main hull. This then is where Harry's proa really shines!

    Now to the other point of production boats..
    Have you seen those black and white photographs of ports in the middle of the 19th century? They were crammed full of engineless workboats which actually got used every day even when it was blowing blue murder. They had families to feed and a boat sitting in a harbour is a liability, not an asset. So those boats HAD to work.
    Nowadays sailboats are almost all for pleasure use and do not leave the harbour in anything less than optimum conditions and even then the stats show the average modern yacht spends more than 95% of its time in the harbour.
    Considering that it is not surprising there are less sailing accidents now tan then.
    I do agree that most modern production boats are very well designed for what they are meant to do. Cheap to mass produce, very comfortable in the harbour with all the luxuries of life on land and lively performance in good conditions, and meant to be motored in and out of harbors or when the wind is light. They are very poor performers in light airs and in heavy conditions, because they are not designed to do that stuff. In light winds the designer expects the engine to be used, hence the typically very small sail area to displacement ratios of modern boats. In heavy conditions, the heavily asymmetrical hull with the extremely tall rig creates serious handling problems. I also find most modern production boats to be pathetically weak. None of this is surprising though, because they are not designed for punishing conditions. You're supposed to listen to the forecasts and be in the harbour when its like that. I knew this would be a controversial point when i made it, but really if people want to follow this thread we should make a new one!!
    And just to be absolutely clear i am not misunderstood i want to say there are a lot of astounding designs out there which are a pride to humanity.. I'm just referring to the majority of mass produced modern boats ( almost all of which are inspired by the obsolete race boats of the IOR era ).
     
  6. Tcubed
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    Tcubed Boat Designer

    Hello Rob, good to hear from you! Our messages crossed. I'll be right back with you...
     
  7. Tcubed
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    Tcubed Boat Designer

    Rob , Thanks for those very nice links. The construction is A1!
    Good to hear the 3500 kg for 50 foot figures almost the same as mine. Very reassuring. This gives about 32 as disp/LWL ratio. I had seen that the IDEC tri has 10.5 disp/LWL ratio, which also reassured me, but not as much because it's really quite different.

    <<You may have reached the same conclusions as me, but your implementation of them is very different to mine. Your boat looks like a copy of Russ Brown's work.>>
    That's exactly right, and yes i draw heavy inspiration from Russ. But it is not a copy as there are two main points in which we differ: My ama is heavier than the main hull whereas his was quite a bit lighter, and my ama is as long as the main hull and semi surface piercing, his were shorter with a lot of sheer.
    I have started looking at the yahoo forum, very interesting, although the format is not quite as user friendly as this forum, or maybe it's just me...

    Accomodation in the lee hull i think is preferable for the reasons of windage and volume distribution i've already mentioned, although the rig on the lee hull is probably enough to keep the machine always the right way round anyways. The biggest advantage is staying dry and having one's stuff at hand, although on the other hand i quite like the idea of all one's junk completely out of the way. I'm kind of a minimalist freak..

    I very much liked to see how you set up the rudders. Very nice. I was toying with the idea of a rotating cylinder that goes right through the boat with the daggerboards going through these, but it means cutting a huge hole through the hull and is a real pain to build. I've heard people say your system looks weak but i don't agree. I think it can be engineered with the supports far apart vertically and be plenty strong. Also they are easy to inspect, maintain and repair. Further, catastrophic impact to these boards cannot rip the bottom of the hull out.

    The leeward pod or sponson is nescessary in my case to be able to sheet the sails. From all my research they do seem to give a little buffer between flying the ama and whoops over she goes.. It of course makes a fabulous place for sleeping, but that is a secondary consideration. The engineering of it is tricky due to the sheetloads, especially the mainsheet. However the mast is stepped on the windward edge of the main hull so does not affect the sponson. It is also so placed that it is essentially sitting on the leeward gunwale so no hull gets reduced really. There i don't think there is any problem, just the mainsheet, which i expect will pull in the order of 15000N to 20000N as a rough guess so yes it would have to be very strong. With a balestrone rig i get rid of all that but then i need to make an even more rigid boom.

    As for prototyping, i was already planning on doing a ten to one scale radio control model just to make sure it all works as anticipated. It is my standard procedure whenever i feel it is outside of already tried things.

    Thanks for your input and offer, Rob.
    I will have some specific questions i want to ask you in the next post.

    Tcubed
     

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  8. RHough
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    RHough Retro Dude

    Puuuuurfect! ;)

    I've been following the proa threads with mild interest. I decided that life is too short to sail slowly. :)

    At first glance the proa idea looks very attractive. I admit I have not looked real hard, but I have never seen anyone address sailing dynamics and crew motion comfort in any detail.

    All motion acts through the CG. The greater the distance is between the CG and the CB the greater the RM is ... so wider is better (in general). It is the distribution of weight around the CG that concerns me. As mass is moved father from the CG, every excursion from steady state requires greater stability in that axis to resist and damp the motion.

    Again very generally, most people are more comfortable when subject to lower accelerations than greater. That means put the people close to the CG.

    I've never seen anyone show how the drive and drag forces interact on a proa. For a proa to have equal performance on both tacks, the longitudinal CG and CB must be at 50% of LOA, correct? The sail plan will have the CE aft of the CB correct? The rudder moves the CLR aft, does it move the CLR aft far enough so a single dagger board can be used? How efficient is a dagger board foil that must have equal lift slopes when the flow direction is reversed?

    Lots of unanswered questions.
     
  9. terhohalme
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    terhohalme BEng Boat Technology

    You should read these too until final decision.

    Terho
     

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  10. Tcubed
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    Tcubed Boat Designer

    Rhough ,
    <<<All motion acts through the CG. The greater the distance is between the CG and the CB the greater the RM is ... so wider is better (in general). It is the distribution of weight around the CG that concerns me. As mass is moved father from the CG, every excursion from steady state requires greater stability in that axis to resist and damp the motion.>>>

    Just a quick summary. Proas just like any multihull have very high initial stability and tend to conform to the local water surface very quickly. This can indeed produce quite high accelerations, but in practice it's not nearly as jerky as one might expect. No, the axis of rotation of motions does not necessarily pass through the CG, although it tends to pass in the vicinity. The analysis of a boats motion in a seaway is actually possibly one of the most complex facets of boat design and highly worthwhile to pursue but in another thread...
    Mass should always be concentrated as close to midships as possible in all boats so as to reduce the boats' rotational moment of inertia about the transversal axis to allow the boat to follow the surface of the water as closely as possible. This is important and yet rarely followed with horrendous pitching the result.

    <<<I've never seen anyone show how the drive and drag forces interact on a proa. For a proa to have equal performance on both tacks, the longitudinal CG and CB must be at 50% of LOA, correct? The sail plan will have the CE aft of the CB correct? The rudder moves the CLR aft, does it move the CLR aft far enough so a single dagger board can be used? How efficient is a dagger board foil that must have equal lift slopes when the flow direction is reversed?>>>
    I suggest you just make some vector sketches. As for cambered foils that have interchangeable leading and trailing edges, i don't have data on these unusual foils, but i'd guess the L/D ratio becomes about 5% worse than a similar non reversible foil.
    Any one out there with graphs of this type of foil?
     
  11. Tcubed
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    Tcubed Boat Designer

    Thanks Terho . Those attachments sum up the fundamentals perfectly.
     
  12. RHough
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    RHough Retro Dude

    I won't try to argue merits of one proa style over another, however, what seems obvious to me is that the number of things that have to happen when a proa shunts introduces a complexity of structure and construction that tend to offset the simpler, cheaper, lighter mantra.

    Since this is your thread, and you have already convinced yourself that a proa meets your design brief, I'll wish you all the best and continue to lurk.

    cheers,

    R
     
  13. rwatson
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    rwatson Senior Member

    That was a good link to the clips in shunting the KB proa.

    It was enough work with someone balancing out on the skinny end of a hull with a handfull of jib in their hands, in great conditions.

    Imagine doing it in 2 metre waves or more with severe winds!!! It doesnt bear thinking about. You would be crazy to do a long distance voyage short handed. As captain of that boat, the fact that the crew wasnt wearing a safety harness would worry me. Sure, the conditions were great, but look at the scenario of the poor guy bumping his head on the way under the boat, and he could be wrapped up in the jib. Now the boat doesnt have a jib to maneuver, and it stated these were strong tidal areas.

    Proas have to be able to shunt quickly and often in some situations, and as most disasters occur near land, the ability to handle uncomfortable and rapidly changing situations is paramount to survival.

    The performance analysis is very interesting. It boiled down to "put the most weight out to windward for the safest configuration". I could say duuuuuh!!

    When there is a racing fleet of heavily sponsored Proas on the water, all the finesse of performance calculations will be required. For the average world cruiser, being able to comfortably and safely average 15-20 knots is plenty of performance. Until then, easy and safe to control, comfortable to pilot in all conditions is the big challenge. Thats why traditional monohulls "rule the waves". It doesnt matter that you are ten knots faster as you rapidly succumb to hypothermia after 6 hours in an open cockpit. And Catamaran and Tri owners, dont even have the speed differential to be envious of.

    Now, consider just weekend sailing. How hard is it to get experienced and enthusiastic crew for an average day sail, let alone getting crew fit and able enough to walk out the slippery end of a hull every say, 30 minutes to and hour, and change the foresail ?

    The idea of spending much less money on a high performing, safe and comfortable world cruising machine is the end goal here. Take away "safe and comfortable " and all you are left with is another experimental sailing machine that will end up sitting on the moorings year in and year out, as another "priced to sell" object amongst all the other design dogs.

    Thats why I said initially that most of the Proas are designed by "egos". The talk of whether you are two percent faster on a broad reach with a dipping-lugsail, northern hi-aspect cantilevered folderall is all pure ego - and crap!!

    When a designer puts safety, comfort and sheer usability first, *then* I will start looking at the comparative performance.

    Lets get some good quality safe Proa stock out there on the oceans, and prove the concepts. Go Proa Go :)
     
  14. Tcubed
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    Tcubed Boat Designer

    Questions for Rob

    Rob,
    If you feel you'd be compromising your designs by answering feel free to not answer some or any of these questions. I will use the term ama for the windward hull and vaka for the leeward hull, irrespective of their size or weight.

    1* I notice you use a surface piercing bow on the vaka, how does this not concern you in the sense that it has very little extra buoyancy to prevent submerging?
    2*I notice you like a "hump" in the middle of the vaka, why the extra volume in the middle?
    3*What sort of weight distribution do you favor between the two hulls?
    I have 39% vaka, 61% ama.
    4*What prismatic coeff. do you recommend for the ama & vaka respectively?
    I have a prismatic of just under 0.6 for both hulls and the vaka's prismatic remains almost constant throughout the range of possible heeling moments. The vaka submerges about 17.5 cM by the time the ama is just out of the water.
    5*What sail area/displacement would you recommend?
    I have it at about 70 and have calculated that the ama starts coming out at about 15 knt wind. Keep in mind i don't plan on any engine so i want to make sure it has plenty enough sail for light winds. This is one of the reasons i drew it with a gunter mainsail, as it allows me to put more sail but without a dangerously tall mast. Excessively tall masts can be very bad news when winds get to the shrieking stage, i find. Much rather have spars i can lash down on deck and just be left with a compact and strong mast that is not so much windage or so vulnerable whipping around where the wind is even fiercer..
    6*What are your thoughts on a best compromise CLbeam/length for a 61/39 mass distribution considering the need for speed and the avoidance of overpowering (pitchpoling)?
    7*Have you any stories on your proas or any proas, in big storms?

    Tcubed
     

  15. rob denney
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    rob denney Senior Member

    G’day,

    Tcubed,
    Russ’s boats are light(ish) compared to same length cats, but still heavy compared to harry’s. I suspect you will have the same experience. Stayed rigs, big headsails, lee pods, rudders, daggerboards, cockpits and accommodation in stressed hulls are not light, nor is the structure they require to support them.

    Pumping water ballast while sheltering in the lee hull when you could be sitting comfortably under cover in a windward cockpit with righting moment to spare does not make sense to me. You should also read Steve Callaghan’s account in Cruising World of the effects of an over ballasted, under buoyant windward hull in a seaway.

    The rc model is a good idea and will show you a lot about the boat’s sailing characteristics, particularly when you have to ballast the windward hull, lift and lower rudders and change the jib to shunt. It will not model the hard work of living in the lee hull for extended periods, nor the slapping of the water on the underside of the pod when you are trying to sleep. Where abouts are you? There are some rc model (and full size) harrys around the place which may be of interest.


    R Hough,
    There are some unanswered proa questions, but not these. Harry crew (and everything else) is located in the middle 50% of the boat. The motion is far less than on a cat. The Multihull World journalist and his sea sick prone wife who did a boat test wrote that the motion in a harry is far less than in any cat they had been on. My very seasick prone wife agrees as do the sight impaired people who sail on the 50’ter in Holland. The harry format was specifically chosen so these people could move around confidently, yet still experience high speed sailing.

    I use a single daggerboard/rudder combo mounted on the beam and it works very well. Use both of them (one on each beam) if you are too lazy to lift the front one or want steering that is superior to any sailing boat, plus the ability to crab sideways off a jetty or to pinch to a windward mark. The boats are balanced on all points of sail. I suspect this is a function of the rockerless hulls as well as the location of rig and rudders. Beam mounted rudders mean no holes in the boat and as they kick up in a collision, no damage from hitting things.

    Shunting is safer and easier than tacking an overlapping headsail, and far easier and safer than gybing. The harry structure is less complex than, and about half the weight of, any other multi type. There is a video of a 25’ ter shunting in light air at http://www.harryproa.com/ShuntingVideo/ShuntingLg_st.wmv The technique and ease are the same for the bigger boats. The maneuver is even easier with a una rig and easier again with a ballestron.

    Terho’s numbers are excellent, but do not allow for the fact that harrys are considerably lighter than Pacific proas of similar accommodation. I suspect that making the windward hull big enough for all the extras, but still having the crew and galley in the lee hull will exacerbate the poor numbers of the Pacific proa without achieving the good ones of the harry and equalL configurtaions. I see no benefit in equal length hulls if one of them is just for storage.

    R Watson,
    I agree again. For “safety, comfort and sheer usability” it is hard to beat the harry set up. There are few if any cruising boats capable of wind speed in 10-15 knots with as little fuss or crew discomfort as the boat in the harry video.

    T cubed,
    Happy to share what I have learnt, as I am sure you are honest enough to pay me for any ideas of mine you ask for and use. However, I would be very careful about too much mixing of Russ’ and my ideas in the same boat.

    1) Harry bows are not surface piercing. They have more buoyancy further forward than modern tris with the same size rig. This is due to the high prismatic, long lee hull, low weight and small rig possible with the harry format. Flared bows, imo, are asking to be tripped over and cause hobby horsing.
    2) The leeward hull (Polynesian terminology is great for Polynesian craft, but a bit pretentious for western craft with little or nothing in common with them) hump is to support the unstayed mast. Stayed masts are absurd in any cruising boat, but especially so in proas.
    3) I have used many balance variations, depending on the boat use. 60/40 will be fine, but suspect you will need water ballast to achieve it with the crew and galley in the leeward hull.
    4) Harry’s have prismatics over 0.8. See the Russ video on hobbyhorsing for why Cp of 0.6, high cog rigs, V hulls and weight in the ends of the lee hull is a bad idea.
    5) I use Bruce number as a performance indicator for proas, but it does not tell the full story as harrys tend to outperform cats with similar numbers due to lower windage rigs, easier driven hulls and less draggy water foils. The 15m/50’ harry has 50 sqm/537 sq' of sail and weighs 2.5 tonnes/tons. The one in the video weighs 3.5t as it has a bunch of add ons.
    6) I prefer to look at the righting moment rather than the beam to length ratio. 15 knots is dangerously low hull flying wind for a cruising boat. Harry’s are in excess of 25. Gunters are good for dinghies, but draggy when reefed and dangerous when swinging around. I prefer a telescoping unstayed wing mast.
    7) No proas in storms stories apart from Russ in his first boat, which fell apart. This was in Wooden Boat magazine. Harrys have been sailing in 30 knots in the Tasman Sea and gone in and out of some pretty gnarly river mouth bars and behaved exactly as predicted (ie no problems).

    Sorry for dumping on your ideas. Even if you go ahead with what you have drawn, you may still have a more suitable boat than many of the standard production and stock plans cats currently available. Just won’t be as good as it could be. IMO.

    Regards,

    rob
     
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