Sailing outrigger canoe

Discussion in 'Multihulls' started by Michael Farmer, Aug 23, 2021.

  1. Michael Farmer
    Joined: Aug 2021
    Posts: 14
    Likes: 1, Points: 3
    Location: Uk

    Michael Farmer Junior Member

    I have been reading up on the Marshall Island Proas, does anyone know how the amas are attached to the cross beams. I can see they are usually lashed into place with cords to give some flexibility, in the description, they say it's a unique system that absorbs shock loads but no more detail than that. I'm wondering if the crossbeams are used in a torsional suspension roll as video clips show the amas moving at a different rate to the main hull in a seaway, any comments or thoughts would be welcome
    Michael
     
  2. gonzo
    Joined: Aug 2002
    Posts: 15,934
    Likes: 1,284, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    If you look at the boats built in ancient times, they were lashed together. By modern standards, it is a sloppy, loose connection. However, it worked well. They had diagonal braces to keep the connections from racking too much. Are you building a proa?
     
  3. fallguy
    Joined: Dec 2016
    Posts: 6,368
    Likes: 1,298, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    If you get a chance to get Gary Dierkings book, he also shows the connection. I am a fan of his...built a modified set of akas and amas based on his book.

    Mine are probably not what you want..so I won't bore you!
     
  4. Michael Farmer
    Joined: Aug 2021
    Posts: 14
    Likes: 1, Points: 3
    Location: Uk

    Michael Farmer Junior Member


    Thanks for the reply, not a proa as such, a tacking outrigger canoe around 16 feet to launch and recover from the beech. I have no experience of proas, but I don't think shunting would be suitable for the varied wind conditions in the UK

    Michael
     
  5. Michael Farmer
    Joined: Aug 2021
    Posts: 14
    Likes: 1, Points: 3
    Location: Uk

    Michael Farmer Junior Member


    Thanks for the reply, have you any photos of your setup, I would like to see your interpretation
    Michael
     
  6. fallguy
    Joined: Dec 2016
    Posts: 6,368
    Likes: 1,298, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    No good pic, but I can explain.

    I made xps outriggers, about 5' long for my canoe.

    I used a skipped size of pvc pipe. I bedded the pipe in the ama in two places in pb epoxy.. Then I used a pvc tee on the aka end. Then fit it all together and let it all cure. I have two screw positions and use a pin on each for loaded, heavy loaded. The amas are not supposed to be deep in the water.

    btw, I rubber lash the aka to the boat and it is super string tied right. The reason for the outriggers is the water is 39F and we can't afford to go over. We are doing recreational netting and come out with 50-100 pounds of fish in November. Pulling nets in a canoe is a bit dangerous and the boat can go over easier.
    6EB1E1E0-E2DB-4100-8D7C-021FD7202A66.jpeg
     
  7. fallguy
    Joined: Dec 2016
    Posts: 6,368
    Likes: 1,298, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    If you really like the method, I can get better pictures for you. The pipe is not a toght pipe fit because we skipped a size, but it wirks great and is not sloppy. I spent hours planning it.m

    I didn't want it to be one big giant unit for hauling in the truck.
     
  8. Michael Farmer
    Joined: Aug 2021
    Posts: 14
    Likes: 1, Points: 3
    Location: Uk

    Michael Farmer Junior Member

     
  9. Michael Farmer
    Joined: Aug 2021
    Posts: 14
    Likes: 1, Points: 3
    Location: Uk

    Michael Farmer Junior Member

    Thanks for sharing your ideas

    Kind regards Michael
     
  10. garydierking
    Joined: Sep 2004
    Posts: 182
    Likes: 55, Points: 28, Legacy Rep: 174
    Location: New Zealand

    garydierking Senior Member

    [​IMG]

    Here is a good view of the Marshallese method of ama attachment.
     
    fallguy likes this.
  11. Michael Farmer
    Joined: Aug 2021
    Posts: 14
    Likes: 1, Points: 3
    Location: Uk

    Michael Farmer Junior Member

    Thanks, what a lot of parts! The centre crossbeam looks heavier than the outer ones. I imagine the ama rotates around the centre one in a seaway as the amas are considerably longer than the beams fixing centres creating considerable torsional stress in the whole structure. This would account for the amas ability to move independently to the main hull, impressive as its a development in engineering that's evolved over time using available materials before we knew how to calculate these forces mathematically.
     
    Last edited: Aug 26, 2021
  12. fallguy
    Joined: Dec 2016
    Posts: 6,368
    Likes: 1,298, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I think the magic is that they spring back.

    The systems are springs and bend; not break.

    When I rubber lash the akas to my hull, the catastrophhic failure would be of the aka or the ash gunnel. Instead, when a heavier than normal load is applied, the rubber springs a bit, just as I expect the rope lashings do here.
     
  13. peterAustralia
    Joined: Mar 2006
    Posts: 432
    Likes: 54, Points: 28, Legacy Rep: 233
    Location: Melbourne Australia

    peterAustralia Senior Member

    no, no, no, no, no, no

    Sailing canoes come in shunting types, and tacking types. The flexible ama technology is brilliant for the pacific proa type. It gives the ama a suspension mechanism that allows the ama to pivot in pitch independently of the vaka. This is suitable for shunting with the ama to windward. It is totally unsuited to ama to leeward, which happens half the time on a tacking canoe. You need a fixed attachment, for when the bow of your ama goes into a wave. In this scenario the bow of your ama is pushing up and trying to raise the entire boat so that it does not faceplant right into a huge wave. Imagine a trimaran flying along into a wave, and just forget for a moment that the other outrigger is not there. You want the outrigger in the water to be strong, and to push the bow of the ama up.

    The upside is that your ama does not need to be huge, say for example it weighs 30kg, and has a volume of 130L, which is 15kg of ama, and you add an extra 15kg of stores, be that chain, water, food, spare anchor, camping gear etc. On one tack you only have 30kg of weight. On the other tack, ama to leeward (trimaran tack), you only have a maximum upward force of 100kg (130kg - 30kg). You ama cannot push up more than 100kg otherwise if would sink.

    Of course apply a factor of safety.

    To sum up, the flexible ama technology is not suitable for tacking canoe (only shunting), the maximum loads are proportional to net ama volume, and for a ama of moderate volume, maximum loads are modest

    For more information see here
    tackingoutrigger.com -- tacking outrigger sailing canoes http://www.tackingoutrigger.com (my website) or the newly formed facebook group on tacking outrigger canoes
    Facebook Groups https://www.facebook.com/groups/217818223302263
     
  14. fallguy
    Joined: Dec 2016
    Posts: 6,368
    Likes: 1,298, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    What are you saying no to?
     

  15. peterAustralia
    Joined: Mar 2006
    Posts: 432
    Likes: 54, Points: 28, Legacy Rep: 233
    Location: Melbourne Australia

    peterAustralia Senior Member

    The no relates to the idea of a flexible ama in your application (tacking)
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.