Affordable, long-term liveaboard?

Discussion in 'Projects & Proposals' started by Filmdaddy, Aug 4, 2005.

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  1. Sailor Alan
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    Sailor Alan Senior Member

    This boat is one of the most remarkable i have ever seen. I am truly astonished. Other than wondering how it would perform in the NW pacific, it could be an ideal boat for your purposes, build it as is!

    I understand the logic behind the 10:1 L/B ratio, fair enough. If you do a kind of shortened Tlinget (from Bill Garden), you will get 40’ long by 4’ WLB, and flair to a true dory style. As long as you do not exceed 6’ total beam, this should be acceptable, and safe, with a very limited section of light cabin with 6’ headroom. I will discuss light weight building later. Though tender, it will roll like mad, it will be safe, but require good handling in rough weather. Built well, with a near continuous (sealed) deck and frames for stability, this should take any weather as long as the crew is in charge.

    My personal preference for your solution was something like

    http://www.yachtworld.com/boats/201...nge-Trimaran-2696204/New-Zealand#.U6HG8BZvXzR

    Not so much a dory with trainer wheels, but a central hull taking full advantage of the increased height above the water allowed by the training wheels. It need not have this 'wave piercing' bow, but will be fast enough to need fully enclosed steering station. I wonder if, at speed, under power, the 'training wheels' could be retracted safely to reduce resistance still further?
    At the risk of repeating myself, i might buy a ‘time expired’ square jump parachute, and ‘fly’ it as a sail. Launched and retrieved using a single central line, just like a spinnaker ‘shooter’, from a 6-8’ high, bell mouthed vertical mast or tube, one static and control line would lead to the top of the mast, the other to the bottom. Each would have a separate mainsheet system for control. The ‘square’ parachute will fly LE to the wind, ie vertical, and its ‘lift’ can be controlled by the ‘flair lines’ as part of the standard package. You do not need a new ‘para-glider’ wing, they are trying to get the last possible speed toward the wind direction, and utilizing some very sophisticated controls to do it.

    Now we get the most astonishing boat of all, the one above. The power dory/sharpie with extremely wide spread and low buoyancy arma’s. Clearly it, like the boats with ‘training wheels’ cannot take a lot of rolling force, so would not be very suitable for reaching, or beating under a high aspect ratio main and jib. But i could see myself setting a Gunter Lug main on each of those masts as is, and getting quite a lot of speed and power under certain limited conditions. The amas certainly fold, but not for road transport as is, i can only assume this is for docking space. Ill bet it sips fuel too, and could be very fast if it wanted too. I suspect hitting a wave at high speed might damage an ama, but perhaps at such a speed they simply hoist the ama’s overhead?

    Truly Amazing.
     
  2. Sailor Alan
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    Sailor Alan Senior Member

    Water jets are not necessarily efficient, merely expedient when in very shallow water, or where human body parts can become entangled.

    The MOST efficient are VERY large diameter propellers turning very slowly. I just consulted my (very old) propeller book, and it recommends 30+ inches for a propeller on your size boat. I suspect clearance, draft, and other factors have driven boats propellers smaller and faster, just as marina fees have forced boats to be shorter and wider, and less efficient that way too. Big propellers also regenerate better too, though at what efficiency i do not know, though far better than almost anything else.

    Someone on this forum (you?) suggested turning the propeller by electric motor at exactly boat speed for zero drag and thrust. Perhaps worth thinking about.

    Using ‘long tail’ type shafts, with lifting propellers is not a bad idea, and allows several propellers, and engines, to be available as spares, for maneuvering, or all together for emergencies. They need not steer, merely tilt. Not necessarily neat, but effective. Even the main central shaft could be treated this way.
    A reminder that propellers set too far behind the center of buoyancy do tend to lift out and spin uselessly.
     
  3. NoahWannabe
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    NoahWannabe Junior Member

    Motion Sickness at Sea

    Aren't you lucky, no sea sickness! Yes, diesel fume (old charterboat diesel type), one whiff of that in the morning gets me nauseating instantly.

    In my experience, it isn't a light ship or a heavy ship. It is all in the motions dictated by the shape. A catamaran snap roll maybe dangerous but it doesn't make me sick. A heavy trawler with a flat fore-foot in 8-12' swell got me very ill recently. As we cruised 8-12 knot speed, it would accelerate down the swell then quickly decelerate as it climbs next swell. This deceleration is just as bad as a constant rolling during drift/anchor.

    The light ship is good, as long as it has low acceleration of all repeating motions. A sharp bow with some upper buoyancy is good. A sharp V hull in bow-wave zone is good. Rounded stern, hence the bartender transom, is good. Roll stabilizers like trimaran amas with V-shaped hull is good. Sharp V hulls make contact with wave easily and continue to dig in until buoyancy balances things out. The high buoyancy V hull is good for reaching and windward sailing too. Reduced bow slap is good. Thus, narrow long dory hull with sharp bow and some overhang, narrow rounded stern, and long amas with high deadrise, high buoyancy V hull. Another thing is extremities should have some masses to absorb initial accelerations, contrary to common weight distribution of heavy items near COG.
     
  4. NoahWannabe
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    NoahWannabe Junior Member

    No need to respond at all. I am here for brainstorming my next boats and just to have fun while learning from others. I lurk most of the time. Comment on things that interest you.

    Only involvement I had with the airplanes were designing LED dot matrix displays for 747,767 and F16 variants. The fighter jet display was fun, LED can dim brightness for the night vision compatible displays. Back in the days.

    1. What is c**p?
    2. Do you have any picture of Hobie glider? That must've been fun :D
    Seriously, which is more efficient, a wing or a single sided foil with adjustable AOA? If one is significantly better then by how much?

    Parasol position as in "T" or ~50 degree canted sail wing?
    Aileron and flap? Haha, I had to think about this. I guess I won't make it as an aeronautic engineer :) Couldn't you have some kind of limit switch/sensor to automatically adjust ailerons and a flap to reduce lift? Or, make underwater foil to change its AOA for downward pull as bow rise above water? It can be an expensive hobby :)

    Which trimaran? The Blakewell red power trimaran?
    Actually, this can work. I go back and forth between a power cruiser and a motorsailor. Pure economic calculation will favor small twin diesel engines but a motorsailor just gives me better feel for cruising.
     
  5. Sailor Alan
    Joined: Mar 2014
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    Sailor Alan Senior Member

    1. Something bad.

    Yes, the trimaran i was indicating was the red hulled Blakewell from NZ.

    My understanding is, the greater the flair, the greater the increase in displacement over vertical movement, the more sudden the motion. You are getting into areas of pitch motion i don't know much about.

    My own experience with my Trimaran was; the ama’s were a very deep simple “V”, 30deg?, so they did not produce a ‘quick’ motion, but immersed enough so the boat would not ‘rock’ at anchor. Owners requirement. This was fairly successful, but reaching, they were buried nearly to their decks. I should have made them higher, and next time would. To be honest, i was probably overpowering the boat, too much sail in too much wind. I was quite young, and it was certainly fast.

    You are almost defining your own boat here, classically “V”d sections, at least on the ama’s.

    Just thinking aloud; how about a classic Thai ‘long boat, or power dory type hull, 38-40’ LOA, 36’ LWL, and 3’9” BWL. The bow is flaired and raked, like any classic dory. The stern pinches in at the waterline, like a ‘box keel’ but there is a transom above this. In fact the stern could be a regular tombstone type.

    This hull has a bottom of 1/2” Douglas fir plywood with lumber yard stock 2” X 2” cedar stringers at 8” centers, and lateral intercostals every 3’. These intercostals are notched for water to escape as necessary. Classically, these hulls are 1.5" solid plywood.

    This structure is covered by a continuous layer of 3/8” fir plywood, the floor you walk on, though spaces are cut for access to the areas between the stringers, at the lowest point at least.

    The flared, dory like sides up to 4’ only are from 1/2” fir plywood, supported by 2” X 2” lumberyard cedar stringers every 12” and lined inside with builders foam. Where a ‘frame’ is, another vertical 2 X 2 is supported by a 3/8” ply ‘cap’. The gunwale is a lumberyard cedar 2” X 4”.

    Above this gunwale, the cambered deck, cabin sides and roof structure is foam sandwich of 1/4” plywood outside, and 1/8” plywood inside a regular 1.5” (nominally 2”) builders foam. You may cover this with fabric, though avoid any Kevlar or nylon derivative please.

    So far the boat looks rather like the central hull of the yellow “Sun Express” Divers boat in your earlier post.

    Internal accommodation will be similar to the Kurt Hughes -38 power trimaran.

    Now begins the discussion.

    I want to have small, low buoyancy ama’s, but have enough room inside for a Rabbit Diesel in each. Each engine drives a generator, and can be used independently or together. Each ama also contains the bulk of the fuel, so oder is diminished as well.

    We have 4 electric motors, and 3 or 4 shafts. Each ama has one shaft and motor each, and the center hull has, either one shaft and two motors, or two shafts and motors. All shafts may be lifted clear of the water, Thai long tail style. The center hull shaft/propeller's may be lifted into recesses in the underside of the hull for convenience, but they are simple lifts.

    The roof of the cabin sports PV cells, as do a few other surfaces, not enough to be objectionable. There are two wind generators on the quarters, and at least one propeller can regenerate whilst the boat is sailing, or at anchor in a current. There are normal lead acid batteries in a row along the keel line of the main hull.

    The ama’s are attached via aluminum mast sections, and can be slid in an out, adjusting beam as necessary. The deck between the ama’s and main hull is fabric, and can be rolled up and stowed in bad waves and weather. This trimaran will never ‘fly’.

    A 15’-20’ high mast will be installed in front of the cabin, probably deck mounted.

    From this can be flown a 20’ long Gunter yard, giving a 36’ hoist mainsail, and smaller jib, allowing windward work when necessary. The hull could handle 2 such masts, probably identical.

    For downwind work a square, or round parachute will be flown, one riser from the deck, the other some 10’ up the mast. This is to reduce the load on the ama’s, so they can be significantly smaller.

    The ama’s i have in mind will be flat bottom dory style with rocker, steep flared sides, but wide enough to contain the rabbit engines, 10' LWL and 1' WLB, sounds about right. These engines need not be mounted low down, they are stabilized buy the whole craft, and are only generators. They could be mounted quite high for easy access. The ama’s would be 3/8” fir ply over stringers and builders foam, except on the bottom where moisture might collect.
     
  6. Sailor Alan
    Joined: Mar 2014
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    Sailor Alan Senior Member

    The difference between these two totally depends on their use.

    http://www.boatdesign.net/forums/multihulls/sails-vs-wingsails-34944.html

    A classic aircraft wing needs to develop just enough lift to overcome the weight (and downward thrust of the empenage) of the plane, and no more. As it reaches this lift, it changes AOA until it maintains this at minimum drag.

    A sail is intended to increase it's lift, thrust, as high as possible, regardless of wind direction and boat direction. On a boat a wing works extremely well for work close to the wind, or when the apparent wind is brought forward though speed etc. The faster the boat, the more useful it is. Sometimes a limited sail area, class restriction, makes a difference.

    Boat wings have a large range of adjustment and develop higher lift (thrust) per unit area than a soft sail, and generally allow higher aspect ratio too. Hence their use where area is restricted, Little Americas Cup, development classes etc.

    Double sided 'soft' sails, the Lungstrom, Freedom, and Wharram wing, all spring to mind, have not enjoyed wide popularity, but this could be due to excessive chafe, a cruisers nightmare.

    http://www.boatdesign.net/forums/boat-design/wing-sail-design-12417.html

    A modern single sided, full batten, square topped sail is very efficient and also can be reefed, or doused completely. Because of this, it is more efficient over a wider range of conditions and especially wind directions.

    Were I to design a sailboat that flew, a bit pointless as one uses no fossil fuel, and the other uses lots of it, I would start with this wing form.

    http://en.m.wikipedia.org/wiki/Platz_glider

    http://jossresearch.org/2011/02/13/joss-research-institute-web-report-7/

    It would be slow, but 10X faster than the sailboat. This sail could be folded up for weather, or set vertically for sailing. I might even consider leaving the propeller in the water, on a long shaft. Kind of like a super Thai Long Tail, or a flying fish's tail.
     
  7. NoahWannabe
    Joined: May 2014
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    NoahWannabe Junior Member

    Propulsions

    I was thinking 1 diesel engine, 2 AC electric motor powered and backed up by a small portable generator (2-4KW).
    The diesel is the main power for the main propeller cruising at optimal engine RPM. No conversion losses and simple mechanism. Forward and neutral gear only. Alternators on this diesel engine will recharge the battery bank. The AC electric motors of 5-12 KW each on amas will be used for harbor maneuvering and to generate apparent wind in light wind condition. And, hopefully be able to regenerate with AC motors in heavy wind and in tidal current at anchor. AC is less popular but it gives much more options and less wiring issues. Solar panels, a wind generator and a small portable generator for house uses and back up propulsion.

    Which diesel engine would be optimal for 12 knot cruise and 30knot top speed? How much power do I need for 4000-8000# boat?

    Twin Rabbit engine as in twin 1.6 Rabbit/Caddy (60-80 hp) or 1.9 TDI (80-120 hp)? Marinized or car engine?
    200-300 hp should be proper depending on drag (hull + wave). I like cummins. My dodge cummins ISB-CR 5.9 is best I've had on any land diesel. 300+hp, 600+ torque, 1200#, rated life 300k miles with regular maintenance, 1500-2000RPM is optimal fuel efficient range. Does 300+ hp engine sounds like NOT-environmental? Why not? The weight is little heavy but fuel efficiency is good. It will last my life time :rolleyes:

    Simple single handed sail with twin unstayed masts with single or twin jibs sound good. Twin junks, lug or sprit rigs are all good. Low aspect rigs for easier mast handling and stability. As a fast cruiser, I don't need high upwind ability, I will motor instead. I won't give up on windward capability if the design results in that way, but no need to design it in if difficult.
    I will probably add lifting strakes or lifting foil underwater for speed improvement. Large lifting/retractable rudders on amas but no dagger/lee boards. I hope amas will provide enough lateral resistance for downwind and reaching.

    I thought about soft wingsail but storage was a concern, but if chafing seems to be a bigger issue then it isn't worth it. I see your point about parachute-sailing for downwind sailing. But wouldn't it add more gears if square sails are already onboard? How does parasailing compare to a genaker or large furling jib(s)? Compare them for sailing performance, cost, ease of use, maintenance and multifunctionality. If parasailing can eliminate standard sails for downwind and reaching then it will be a definite possibility. Since the boat already has sails, wouldn't it be more complicated to add parachute(s)? Maybe, I am just not familiar with it yet. If taking advantage of higher altitude wind with parasailing is easy as sailing in most condition and especially if it can replace standard unstayed sail rigs then it is an easy alternatives. I need to research more on this.

    A rectangle parachute on each amas bow instead of any sailing rigs sounds real good. Then I can have pure power boat design.
    Better yet, make a remote piloted platz glider and tow the boat with shock absorbing solid collapsible links. You can make it fly as much as linkage allows and still call it a boat. :D
     
  8. Yobarnacle
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    Yobarnacle Senior Member holding true course

    A short length of nylon line attached between boat and kite tether is all the elastic shock absorber you need.
    We use a nylon strap between tow wire and the chain bridles on barges, for shock absorber. Tug has more than 4000 HP.
     
  9. NoahWannabe
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    NoahWannabe Junior Member

    Yobanacle, how much did a barge weigh? What size nylon strap (length and width/# rating) and tow wire (steel? length and diameter/# rating) did you use?
    How do you determine the best size towline to use? Say for 4000# boat and 8000# boat?
     
  10. Sailor Alan
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    Sailor Alan Senior Member

    Question for Yobarnacle.

    A tug was towing a barge across Puget sound, beautiful sunny day. A sailboat was approaching the tug/barge combination in such a way as to be in danger of sailing between the tug and barge. The tug crew waved, the sailor waved back.

    A WSDoT ferry was passing, and sounded its siren/horn, whilst someone on the bridge waved. the sailor waved back.

    Poor tug captain watched helplessly as his barge port bow struck the sailboat, and rolled it over. No loss of life, but i guess the sailboat at least was damaged.

    Question. Should the tug captain have used a ‘very’ pistol or other flare to try to warn the sailor, and are these signal devices encouraged, or even available now.

    Comments from other sailors concluded the sailor was probably drunk, a common enough problem here on these rare sunny days with wind.

    Please note; statistics have it that sun, 12kt wind, and a weekend, happen simultaneously in Puget sound about once every 2 years. I think we say this to discourage people moving to the area.
     
  11. Sailor Alan
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    Sailor Alan Senior Member

    A very full and complete specification here, nearly enough to go to a NA.

    Large diesel engines as you describe, 300hp+ have an issue with “idle’. When they have enough power to drive the boat at, say, 30kts, their idle speed, not a very economical RPM i might add, is still too fast for economical ocean crossing speeds.

    If you have this kind of power installed, then the simple weight of the engine will discourage speed, and fuel available might discourage ocean crossing. Read Bebe’s book, and/or the posts below.

    Rather than having a large 300hp main motor, consider having a 150hp main motor, with 2 X 75hp 3 phase electric motors in series on the same shaft. At slow speed, the vessel absorbing perhaps 50hp (typical of a long, slender, 6,000lb vessel) whilst the 2 electric motors generate 50hp power each for the batteries.

    Now a pirate comes along, and you want speed. The batteries now drive a PWM (Pulse Width Modulation) inverter feeding the 3 phase electric motors, and you have 300 hp at a slight overspeed of the diesel, AND both the 3 phase motors. They are being driven at 250V AC 75hz, so their flux density is correct. Same propeller. Under these circumstances, you can activate the Ama motors as well, but propeller pitch choice will be a trick (manuvering, or 30kts). Fortunatly these motors overspeed quite comfortably, though the V/f curve will need to be changed.

    If the batteries are full, the diesel is only producing 50hp @12kt, and fairly ineffectively at that, but thats another story.

    A fixed pitch propeller has a power absorbency curve, typically cubic in nature.

    http://www.boatdesign.net/forums/boat-design/downeast-hull-design-11736-3.html Post #42.

    You are correct, parasails are really just a ‘soft’ kite. During WW1, and the Boar war, man carrying kites were used when the wind was too much for early observation balloons. Modern parasails are really just a soft development of these, complete with ‘stacking’ principles.

    In essence you trade ease of launching (the ‘kites’ with some structure) for ease of stowage (the ‘soft’ versions). As in everything, people are always trying to improve, and these sophisticated high aspect ratio parasail’s get a few more degrees of glide angle. In my opinion, not enough to justify the expense, and complex control system, on a boat.

    If you are providing sails anyway, then use the sail, in every direction. I was thinking of using time expired parachutes as cheap reaching and running sails only, no other sails, but that was the concept.
     
  12. Sailor Alan
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    Sailor Alan Senior Member

    At the most fundamental level, aluminum is dirt and electricity. Steel is slightly more expensive dirt, and electricity. A wood boat on the other hand, is partly renewable wood, but most of the rest is mineral oil. Yes i know glass fiber is sand and heat, the best (aerospace) carbon fiber comes from Bitumen, and some soy bean oil might be used, but its basically mineral oil.

    The coating are the real issue. Aluminum need not be painted, and though it looks a bit industrial, i quite like it. Steel must be protected, and though you can ’passivate’ steel, the final coats still rely on mineral oil. What happened to ‘Corten’ steel? Wood must be coated, and all its coatings start life as mineral oil.

    Had i the money, i would build in aluminum, but wool is my passion. A good case can be made for a used fiberglass boat, the damage has been done, but i doubt we can find something totally suitable for you (though a big Panga might come close).
     
  13. Sailor Alan
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    Sailor Alan Senior Member

    Pwm 101

    PWM 101; 3 phase mains power enters the ‘box’ and is immediately rectified into DC, from 220V 3 phase, you get ~300V DC. This 300V DC is then ‘inverted’ by producing a series of ‘square’ pulses of varying widths, wider in the middle. These pulses of voltage are integrated by the inductance, the copper and iron, in the motor windings to form a quasi sign wave of current. Now normally the rotation of the shaft, the rotor, lags slightly behind the phase rotation of the electric current in the windings, and this ‘slip’ produces the power of the motor. If the motor shaft is ‘pushed’ or over-sped the electric power thus generated will travel back through the inverter (completely automatically, its physics) and try to raise the DC bus voltage. IF a bank of batteries of 300V is placed across this bus, then all this excess energy will be absorbed by the batteries. A fantastically efficient system. Were your boat to slide down a wave, slightly exceeding its then nominal speed, the excess energy created would be absorbed by the batteries, no switching or electronic magic needed. Were some trick of wave and wind to overspeed your Flettner rotor, its excess energy would also be absorbed by the batteries. The trouble is, you are dealing with 300v DC, and salt water, not necessarily easily compatible on a small boat.
     
  14. Yobarnacle
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    Yobarnacle Senior Member holding true course

    I copied this to my collapsible rotor thread
    http://www.boatdesign.net/forums/projects-proposals/collapsible-flettner-rotor-project-50587.html
    hope you don't mind. :)
     

  15. Sailor Alan
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    Sailor Alan Senior Member

    The ‘rabbit’ diesel i was mentioning was the 1.6L naturally aspirated version, thousands of which were used in Europe in every conceivable marine installation. Perhaps they didn't cross to America.

    If you are insistent (wrong word) on the 300hp diesel, you could do this. Install the 300hp diesel, with two 75kW 3 phase electric motors in series on one shaft. When ‘cruising’ the diesel is using less than 100hp for propulsion, and 100hp each for the two generators. This charges a battery bank.

    If you want to go fast, you have 500hp available on tap, without counting the thrust from any auxiliary thrust from maneuvering motor/propellers.

    Hull shape is an issue if you want these kind of speeds, 12kt, cruising, 30kt maximum, you will need to keep the boat narrow.

    I know from airplane design that an airplane designed for very high speed (the Sonic Cruiser) can also have lower drag than a 737 at 737 speeds, but is uneconomical to sell because it is too long, and a bit too heavy (though overall lower fuel burn?). As far as i know, boats do not really do this very well. At 12kt you are semi-planing, and at 30kt you really are planning. Most hull shapes good for low drag at 12kt (usually minimizing ‘base drag’), squat too much as they come properly on plane. Perhaps this is where the retractible horizontal ‘planning boards’ come in.

    To get this disparity in speeds, you could use a box keel for low speed, low drag, (see Tad Roberts “Passage maker Lite” series), but its drag rise would be prohibitive at high speed.

    http://tadroberts.ca/services/new-design/power/passagemakerlite39

    A sort of long slim Bartender (40-45’ X 8-9’) would do the high speed, but have too much wetted surface for slow speed efficiency. If low speed efficiency was not much of an issue, then this kind of old fashioned “Deadrise’ or warped bottom could be excellent. See Tad Roberts efficient light power cruisers.

    http://tadroberts.ca/services/new-design/power/pont44

    I have now discovered that these Philippine trimarans, just like the Thai long-tails, are really for use in fairly benign conditions. These conditions seem to prevail in the Gulf of Thailand, and the South China Sea. I am not sure how suitable these boats would be in rougher conditions.

    Clearly the Philippine boats can be capsized, i sent out a web address showing one upside down, but how they did it, i cannot imagine.

    I also notice that many of these Philippine trimarans have fairly stable main hulls, and may have fairly good initial stability without the outriggers. Statements from people using small, very slim outriggers on western boats like kayaks mention how the outriggers still require a good balance in the kayak. I have also seen photos of Proas with the outrigger nearly buried, usually because someone was standing on it. i.e. they have pretty marginal buoyancy in themselves, and rely on distance from the centerline for effectiveness.

    My question would be, why do the Philippine boats have such stout cables holding their outriggers UP. I would have thought the strain was up, from rolling, so this rigging is the wrong way. I can see no photographic evidence that they lift these outriggers up vertically, even in a crowded anchorage.
     
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