14' cruising Proa based on 'Paradox'

Discussion in 'Multihulls' started by DanielConti, Apr 19, 2015.

  1. DanielConti
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    DanielConti Junior Member

    Hello guys :) I have been reading this forum for a while, harvesting the knowledge for my own ends! ;)

    So basically, I am going to New Zealand in about 6 months to travel and it is my dream to own a boat. Long story short, this is a design I have for a Proa.

    image.jpg

    For those with a keen eye, you will notice that the main hull is two front ends of 'Paradox' joined to make a bi-directional vaka for shunting (14').The ama is essentially a 2' x 2' x 10' cuboid. She will have large symmetrical rudders attached to the aka near the lee hull, like on some harryproa.

    "Why the hell does he want a proa with such a grotesque prismatic coefficient?!" I hear you cry in unison. Well my design brief is for stable, comfortable cruising at average speeds. If that means average for a monohull then thats fine by me as long as the stability is good. I don't want a big boat.

    Soooo....with the intro over my question is: Will she sail?
    From my understanding, because I have more wetted surface than 'Paradox' that would make me slower, but then the proa design allows for more sail than the 100 sq ft on 'Paradox'. Would it be feasable to carry the extra sail? What are the chances of safely reaching planing speed?

    With about 150 sq ft of sail, what I think I have is a stabilised, multihull 'Paradox'. Am I right?

    Construction is 9mm stitch and glue. 200kg displacement, plus me and my stuff probably around 300kg. I want to use a single junk rig.

    Many thanks!
     
  2. DanielConti
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    DanielConti Junior Member

    Just realised that it isn't obvious, but the red box on the vaka is a 2' high by 3' wide lee pod for extra space.
     
  3. lucdekeyser
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    lucdekeyser Senior Member

    Daniel,
    Grotesque prismatic not stability give. Longer lee hull does.
    Free Radical seems close to what you want without the headaches. Good luck.
     
  4. luckystrike
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    luckystrike Power Kraut

    Hi Daniel,

    do you want to sail the boat inside from the big hull or do you want to sit on the trampoline. Do you have a view from the side?

    Do you want to build the boat in the UK and ship it to NZ or do you want to build it there?

    For me your concept looks not right. Why do you want to mix two boats with such different approaches. In my eyes either you build a Proa or a Paradox. Or switch to another succesfull small multihull, like the Duo 480 C, the smallest cat with "sence".

    http://www.ikarus342000.com/DUO480Cpage.htm

    If you want to stay with the Proa, here ist a possible single hander.

    http://proafile.com/multihull-boats/discussion-forum/viewthread/60/

    Good luck! Michel
     
  5. DanielConti
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    DanielConti Junior Member

    Re-design

    Thanks for your thoughts guys!

    I had been thinking about sailing from the trampoline in good weather. I see what you mean about the design looking odd. I was worried that it would be terribly slow and hobby horse a lot.

    I have drawn up a new design more akin to the 25' harryproa beach cruiser. What I lose in accomodation I more than gain in speed and stability.
    I will look at those new links just now.
     
  6. DanielConti
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    DanielConti Junior Member

    I like the look of those catamaran, though I am a little concerned about their sea worthiness due to the relatively narrow beam.

    I will draw up my newer design in freeship CAD when I get the chance.
     
  7. DanielConti
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    DanielConti Junior Member

    Oh, and to answer your question Mike, I will be building it in NZ, probably near Auckland because thats where there is likely to be a wide variety of shops and workshop options.
     
  8. raf pali
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    raf pali Junior Member

    Daniel, your design has bad problems: The aka length is proportionally so very long that will cause an enormous weather helm. The main hull, "vaka" is so blunt that the boat will pitch "hobby horsing" wild. Take my suggestion, when you are in NZ visit as many Museums as you can and watch the ancient local proa the way they were made.
    Take your hat off to the old masters builders and learn how proa should be designed.
    Good luck.
     
  9. DanielConti
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    DanielConti Junior Member

    Yes. Thanks for your comment, it would have been a shame if I had wasted time building it. My newer design has a 20' lee hull and a 14' windward. Each hull also has a much higher aspect ratio. I think this will sort out the problems you mentioned?
     
  10. ThomD
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    ThomD Senior Member

    I get that you are learning with all this, but to the extent you think the boat you originally designed should have been built in 9mm ply, you have so much to learn that you should consider starting with a designer. There are tons of good boats out there. Self-built owner designed things designed to square some unused circle are normally a bad idea. They also normally take at least one rebuild. I designed an entirely successful 16 foot motor cat 10 or 20 years ago. It was pretty much perfect out of the block, but just two minor issues led to huge delays. Getting the motor mount right, and needing to add some kind of keel to the boat for greater bite, even though the hulls were pretty sharp as it was. These were incredibly minor diversions yet they took years to work out. There are major issues I occasionally consider to this day, but I am waiting for the need for a major rebuild. At the time I wanted the motor boat to be displacement, so I built that kind of hull. I think a longer flatter run boat would have been better, though it has been fine. But my point is even when you have the skill to design 99% correct boats the devil is in the detail.

    One of the design briefs was to have enough deck space for a tent somehow despite getting everything dead right in the build, that item got lost when I carried the rear beam forward thereby narrowing the inter-beam space. I had a scale drawing of that view, so I don't really know how that happened.

    If you want to go to NZ and sail, even getting a second hand boat would have strong points. Designing and building is great fun, but it is a whole separate world of ambition.

    Look up sidecar proa blog. He was a lot closer to getting everything right, and having very significant access and support, but it still took several revisions, to get as far as he did.
     
  11. DanielConti
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    DanielConti Junior Member

    @ThomD: Thank you for your comment. You seem to know what you are talking about so I would really appreciate if you looked at this:

    http://www.boatdesign.net/forums/boat-design/21-proa-design-new-zealand-53182.html#post735394

    I get what you mean about squaring the circle. I flat out abandoned doing anything unusual with my design as you will see if you follow the link.

    I am determined however to build my own design and I take full responsibility for any crashing and burning that happens.
     
  12. peterAustralia
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    peterAustralia Senior Member

    4m is too short. My first multihull was an 18ft dory with an outrigger, waterline length was only 13ft or so. It did not work well. I was craving longer waterline length.

    There is the Kir-8 outrigger canoe, an update of teh Kir-2 canoe that sailed 400 ocean miles (fiji to tonga). It was designed by a professional naval architect. Plans are free. I have done a little doodle showing the Kir-8 with a small cabin and a junk sail.

    The other one was my TO-18 sketch. Looking at it now with a fresh eye, I think I would narrow the hull by 8 inches to so, make is faster and make it sit in the water more.

    below u can see some sketches that took me 2 mins. Note the Kir-8 plans (free) can be found here. Kir-8 is about 7m long

    http://www.spc.int/coastfish/en/publications/posters/boat-plans.html

    [​IMG]

    [​IMG]
     
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  13. DanielConti
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    DanielConti Junior Member

    @peterAustralia: Wow! Thanks! That is an excellent resource. Can't believe I didn't come across it during my hundreds of hours of research.
     
  14. DanielConti
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    DanielConti Junior Member

    @peterAustralia: I think seeing as how I have never built a boat before I will stick to the plans as written for the main hull. However I want an ama with more displacement than this one. I should be alright designing an aka.

    Would you think 9mm ply is an absolute necessity? I would rather 6mm or 4mm and plenty of epoxy.
     

  15. peterAustralia
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    peterAustralia Senior Member

    Epoxy does not make the hull stronger, it simply keeps the water out and allows the boat to be durable, last decades if done properly. For an ama 4mm ply would be fine. For the main hull, whatever the designer specifies. I have not studied the plans for a long time for KIR-8, if I had to guess 6mm for main hull would be OK. I dont know what Ovylind Gulbrandsen specficied for this canoe, however whatever it was ... I would go with what he said. I think 4mm is definitely too thin for main hull.

    As far as a bigger ama? The KIR-8 is 7.1m which is a large boat (23ft). I looked at the plans, and the ama is 4.75m, or about 15.5ft. It seems a reasonable size. Remember this is not a high powered trimaran which will sail with only the ama in the water. I think 15.5ft is fine. Plus you can make it out of 2 sheets of ply. 4.5m ama looks totally fine to me.

    Your main question is, will a 23ft canoe be too big? Maybe a shorter canoe, say only 20ft long suit you better? My guess is 20 to 23ft is around about right. Do you have the skills to modify a design? I am worried that a 23ft canoe will cost too much and be too big of a job for you to build. Nothing wrong with the boat, but to build it for 3000 pounds would be tricky.

    I would start by printing out the plans for KIR-8 and use that as a starting point for what you want to do. If in doubt follow the designer.

    I would use KIR-8 as a starting point, making changes from there. 23ft is about 3 sheets of plywood long. Please note that the fellow, Robert Gillett, that built the KIR-2 canoe 25 years ago and he is still using it. His was built out of composite to this design. If your still serious in a few months, I might forward on Rob Gillett's email address to you as a private message. (tacking-outrigger.com is my website). You can question Bob Gillett on how his canoe performs in ocean conditions.

    Other option is buy a large dingy (day boat) something with a little ballast, 16ft dinghy, go sailing with that. The 16ft Wayfarer dinghy sailed to Iceland from Britain. So buying a large dinghy second hand and doing coastal sailing would be your fallback option.

    Looking at the sections of the KIR-8, you would no doubt have noticed the half breadths are around 310mm at mid hull, giving a width of roughly 2ft. Even allowing for some frames that might narrow it a little, thats wide enough to sleep in. You have eight pages of detailed and free designs,,, study them, then make your next move

    Steps = download KIR-8 plans, print them out, think about it, go from there
     
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