canoe design and paddled boats in general

Discussion in 'Boat Design' started by fabrice, Mar 29, 2010.

  1. fabrice
    Joined: Mar 2009
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    fabrice Junior Member

    Hi,
    Sorry if i'ts a bit long to read, but I really need some backup to be sure :

    I ran into a major interrogation yesterday, thinking of a way to build a small outrigger canoe for 3 paddlers :
    My thoughts based on what I saw so far :
    outrigger canoes are very long and narrow boats.
    canadian canoes are short and wide.
    Both of them try to minimize the draft.
    I understand that the major issue is to give enough buoyancy to support the crew and its fret.

    I wanted to keep the narrowest hull possible, because I really like the symmetrical paddling style (for efficiency purpose, you then need to reach the water from both sides, setting the hull beam around 50 cm)

    In my first attempt at designing my hull, it became obvious I could shorten the hull (outrigger canoes are merely competition machine, It's not my goal)

    I then tried a deeper hull with the same beam. I now have a fully immerged hull, my draft is way more important, but my hull is half the lenght of a race one. (5,2 m LOA for a 50 cm beam, draft being 25 cm)

    So far, trying this combination in carlson's hull designer and kayak foundry, I don't see any flaw in my idea, with a target highest speed of 5 to 6 knots. (I'm used to 3 knots trips in solo kayaking, with a top speed around 5 knots, I really don't need to go faster !)

    Am I thinking right ?
    Otherwise, what's the issue and how to deal with it ?

    Thanks !
     
  2. Guest625101138

    Guest625101138 Previous Member

    Have you set out the seating positions. The length is not much when you consider three people swinging paddles about. They need to be seated within the hull so they cannot be at the very ends unless they are sitting on a deck wider than the hull. Minimum width for bum is about 400mm and for feet is about 300mm. Each person needs about 1m. So 3m before you start to taper too much.

    Also 25cm is quite deep compared with other outrigger canoes.

    Outriggers are built for speed. If you are not concerned about speed then you might be able to build the stability into the hull without the need for outriggers - 500mm will be borderline though. OC1s and OC2s are too narrow to sit inside - less than 400mm.

    The 6kts will take a lot of effort for a boat of 5.2m and the load of three people and gear. I expect 3 to 4kts would be sustainable.

    Length counts if you want to go faster. A longer canoe with a single paddler will get to 8 to 9kts with a strong paddler in a sprint and 6kts is sustainable.

    Rick W
     
  3. fabrice
    Joined: Mar 2009
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    fabrice Junior Member

    Thanks for your quick answer rick.
    So, to sum up things : I consider while reading a KAPER prediction, that working against 3 lbs by paddler is sustainable, and 5 lbs a short time max.
    A hull with the design specs formerly said will perform a 4,5 knots around 9 lbs, minus a rough guess of 0,5 knots for the ama drag.
    I assume we are going in the same direction : A gentle pace on the long run gives 4 knots (3 paddlers with a bit of training, though).

    On the other hand, this short and "deeply" ploughed hull computes a mere 2 lbs to run at 2,5 knots (ama drag should be very light then) : piece of cake for a family day tripping.

    No race hull can be that "friendly" at low speed : longer is not always better :D

    50 cm is my club's outrigger hull beam.
     
  4. Guest625101138

    Guest625101138 Previous Member

    The KAPER numbers look OK. The power is roughly related to speed to the power 3 until you get into heavy wave making. So dropping to 2.5kts takes very little power. I find it hard to hold at 2.5kts because there is virtually no load.

    The one problem with a boat that cannot get to 5 or 6kts is that you can get stuck in tidal currents where flows are often of that order. In this case you will go backwards. However it is only a matter of planning. Some locations have currents above 10kts so any paddled craft can get caught out. Even large sailing boats in these currents go backwards. If you know the waterway then you factor such things. Point is if there are currents then make sure you allow for them. Even currents as low as 1 to 2kts is going to have a big impact on the time difference going with and against if the boat is doing only 3 to 4knts.

    Rick W
     
  5. fabrice
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    fabrice Junior Member

    You're totally right !

    I'm lucky enough to paddle in a friendly environment : equinox tidal currents are rarely more than 1,5 knot. Average is about 0,5 to 0,9.
    Combined with wind, it can make your journey a hard time, but not really a life gamble.

    Not to mention engaging a trip at sea paddle powered only should always be prepared.
     
  6. Easy Rider
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    Location: NW Washington State USA

    Easy Rider Senior Member

    Rick,
    Another reason for outriggers could be safety. If one ventures into bigger water, have children or perhaps a power canoe that can go great distances the greatly increased stability of one or two outriggers could turn a questionable adventure into a comfortable outing. I intend to put outriggers on my 18' power canoe. I could still carry the canoe, outriggers, outboard and fuel ect over logs or through the woods to a remote launching site and go to some really wonderful wilderness places perhaps 20 or 30 miles away.

    Easy Rider
     

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  7. Guest625101138

    Guest625101138 Previous Member

    The outriggers certainly give more freedom of movement in the boat in most conditions.

    If I was venturing a long way offshore in a little boat I would want it self-righting. So it has to have the CofG low enough in a hull that can be fully sealed.

    I have experienced a couple of flips with a single outrigger so I do not regard them as particularly useful for improving stability. If it is lightweight it does not offer much righting moment one way. If it is heavy it adds considerable drag. Two outriggers that are mounted just above the static water level offer good righting moment either way and do not add much hydrodynamic drag. They do add windage.

    Rick W
     
  8. fabrice
    Joined: Mar 2009
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    fabrice Junior Member

    Rick, solo outriggers are really tipy, it's true.
    team outriggers are definitely more stable, but when a wave comes on the ama side, it's a tricky situation anyway...
    water motion sucks the hull to the right, wave lifts the ama on the left aaaaaand .... wait for iiiiit : huli ! (pretty polynesian word for "capsize") :D

    single outriggers are not perfect for capsize prevention, but for ease of reentry.
    Even alone in a solo (definitely not my advice).
    Easier though in centre pacific summer waters than north atlantic winter ones.

    That's the very reason why I abandonned kayak paddling at sea : Reentry is a pain in the *** at best, a real security issue at worst.

    double outriggers : Yes, I am thinking of something like that. Nevertheless, I wonder why pacific people sticked to the single outrigger ...
    1000 years of practice and evolution mean something I guess ... or are they bind to traditions, and a bit lazy ? ;)
     
  9. Guest625101138

    Guest625101138 Previous Member

    A small slow boat for use in open water needs to be self-righting. It is also better if you do not get wet in the process of righting it so needs to be fully sealed.

    A twin outrigger is really easier to right than a single providing an outrigger supports less than the crew weight. Stand on one of the outriggers until it submerges then grab the high one and pull it overhead to ride it to water level. You can remount from either side.

    A kayaker, Andrew McAuley, got within a few Kilometers of New Zealand from Australia in his kayak. It had a sealable lid for the cockpit but a hinge ultimately failed on it. During the voyage he weathered conditions similar to those that decimated the 1998 Sydney Hobart fleet. He roiled many times without drama. One of the big keel yachts in the 1998 race proved to be stable upside down even with the keel attached.

    Rick W
     
  10. fabrice
    Joined: Mar 2009
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    fabrice Junior Member

    isn't twin outrigger subject to stress, more than a single ?
    It's often said that, on short but rough waves, a single will follow the wave while the twin can be stuck between two wave cliffs, with the hull in the trough.
    Iatos (connecting spars) need to be quite strong then.

    Andrew Mc Auley was a great adventurer. A tough guy, I guess, and a sharply trained sportsman.

    Not really the casual kayaker, and definitely not an example to follow on the loose :eek:

    Heroes doing unbelievable things with a kayak doesn't mean a kayak is safe :D
     
  11. Guest625101138

    Guest625101138 Previous Member

    The support beam only needs to be strong enough to submerge the outrigger. That is the limit of the force. Once submerged the boat will more than likely roll anyhow.

    I was not suggesting what Andrew did was safe. In fact it proved to be very unsafe in the end. But he went through severe conditions. If he used an outrigger canoe it would have stayed upside down. His condition deteriorated because of the confinement. The boat was too small to move in. He could not even stretch out to sleep.

    Rick W
     
  12. fabrice
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    fabrice Junior Member

    interesting. a low buoyancy ama should fit your description.
    The choice will then be single high buoyancy ama, or twin low buoyancy.
    Of course we are still speaking of a paddling unit. A sail could change drastically the ama configuration.

    Andrew's death is a mystery.
    Don't know if you've got more informations from the official inquiry, I can rely on internet facts only ...
    He told his kayak was sinking but actually it wasn't, Coast Guards found it !
    looks like a combination of rough conditions and sheer exhaustion, leading to lapse of reason and hallucinations. Just my theory.
     
  13. Guest625101138

    Guest625101138 Previous Member

    Twin outriggers are best to have less buoyancy then that required for the crew to submerge one. Weight does not matter.

    A single outrigger needs enough weight to provide adequate righting moment. If it is heavy enough then righting is also done by submerging it.

    If you look at the video they produced from the footage retrieved from the kayak and what he sent through you will see how debilitated he became. The lack of space really got to him. This is a short extract:
    http://www.youtube.com/watch?v=KvCt3AVWr2s&feature=fvsr
    The documentary shows more of the development of his fatigue. I do not know if you can still buy the disc.

    Rick W
     
  14. fabrice
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    fabrice Junior Member

    What a heart breaking sight. The man weeps from the beginning, as if he knew ...
    In his last message we hear a very tired man fighting in order not to pass out.
    I just came to know that a team succeeded a few months later ... with a quite different material !
     

  15. fabrice
    Joined: Mar 2009
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    fabrice Junior Member

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