Small Tri's under 20', any mention of foils is banned..

Discussion in 'Multihulls' started by waynemarlow, Jan 13, 2015.

  1. Doug Lord
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    Doug Lord Flight Ready

    weight varies as the cube of length

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    If you doubled the A, the new boat would weigh 8 times as much (8X 75=600kg) . 2^3=8 ; 4^3=64.........not including FOILS, I mean F***s. Or maybe it includes F***s?
     
  2. Gary Baigent
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    Gary Baigent Senior Member

    Wayne, agreed, Sid is a minimalist but my point was you can build with basic materials and still have a light boat. Also, old mate, your A is 5.5 metres, not 6.5m. And you can't go down below, which is cramped on Sid but possible.
    Interestingly I'm drawing up a 6.5 right now, accommodation below for two; quite luxurious compared to Sid. And yes, has a type of unmentionable design on the end of the beam.
     
  3. patzefran
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    patzefran patzefran

    To Gary Baigent

    I agree a stressed plywood hull is lighter than a Strike 20 doris slape stringer and frames.
    My firts A class cat built in stressed plywood from Gougeon / Lindahl plans weighted 119 kg with aluminium mast and 2.52 m aluminium beams (not to the class rules !). Strike 20 designed waterline displacement is 585 kg wich corresponds to 4 heavy crew aboard. Structure is designed to use rotating arms and fly the main hull, as well as using a F18 or 19' catamarans hulls and rig(Around 180 kg by himself). I have built several stressed plywood hulls including 20' Tremolino outriggers (much lighter than Nacra 5.8 hulls !), but I will not build again as the method gives unpredictable results unless you are an artist or use proven shapes like Tornado (my Gougeon A class cat as well as Tremolino outriggers had unwanted chines !). I agree the 8.50 Foiler is (perhaps !) light but do not correspond to a regular Trimaran use. To my knowledge,the lighter 20' tri seems the Warren ULD 20 claimed at 130 kg which seems oustanding. However its rig and sails seems minimaristic, ready to blow up at the first strong wind (compared to my Bim V1 A class cat !).
    To finish, like Richard Woods, my philosophy is to bulid easily, quick and cheap, wchich not necessarily corresponds to the lightest weigt !
    Cheers.

    Patricl Gallais
     
  4. Gary Baigent
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    Gary Baigent Senior Member

    Bonjour Patrici, Yes the 8.5 Sid could have been built lighter (but not by much) because the gain (in obtaining lightness) is in the small floats and the lifting foils. However I've never had any real sail and control problems with this approach.
    My 6.5m will have a proportionately larger main hull than Sid - but will still be 14.8 to 1 beam/length ratio. Sid of course is much finer. The 6.5's rotating beam (for transpor) will be over square and that wide beam has to able to take the sailing and foil loads, therefore some weight will accumulate. But the result is still lighter than a two beam design with full length floats.
    Second image is the very neat Patterson 6.5m.
     

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  5. waynemarlow
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    waynemarlow Senior Member

    Totally agree guys you can build with basic materials and still get a light boat, I certainly are of the believe though at about 20ft there is an equalisation of materials and at this point in length, it is really what the builder prefers to build in.

    Although it maybe preferable to build in a rough crude way and get a boat faster on the water, I do like really sleek and modern looking shapes, the modern shape of the latest gliders have to be one of the most pleasing shapes to my eye of any modern structure. Sadly most wood built boats just cannot get that really nice look, well to me anyway.

    I have had over the years some discussions with some pretty good aircraft designers, to a man they always say, if it doesn't look right to the eye, then it probably isn't.
     
  6. upchurchmr
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    upchurchmr Senior Member

    You can have as sleek as you want with strip planking.
    A combination of strip and tortured ply gives other options.

    As you say, it is probably largely up to the builders bias (not a nasty comment, given that my bias is wood and yours obviously is not). My being cheap is another factor, personally.

    It is interesting that many modern molded "sleek" shapes are initially built on a male strip planked mold before the decision is made to go to female molded.
    CNC capabilities may now change that path. :)
     
  7. patzefran
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    patzefran patzefran

    Hi Gary

    6.5 LWL and 14.8 L/B gives roughly 380 kg WL displacement.
    Assuming 150 kg boatweight , load carrying capacity is about 3 x 75 kg crew. No place for gazoline, outboard motor, anchorline and security equipment !
    Cheers

    Patrick
     
  8. Jetboy
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    Jetboy Senior Member

    I've been working on a Scarab 18 for a while now. It's a lot of work for sure, but should be a great boat for what I want.

    For me - I wanted:

    Daysailer
    faster than what I had - a Venture 17
    as comfortable as a venture 17 for non-sailers ie. dry and ability to haul a cooler of snacks/beer.
    ability to carry an outboard for returning when the wind is down
    fits in my garage with the trailer - I'll trailer most of the time
    fast assembly from trailer to water in under 30 minutes - ideally 10 minutes if I prep what I can at home. Basically simple rigging + lazy jacks + boomless fully battened main sail with slugs + roller furling + easy assembly of floats = quick prep time.
    And safe. I want a very safe boat that I can take my friends who are often not sailers out without scaring them. For this reason I have acquired two masts. One 30' mast that I will have custom sails made for for my own enjoyment. I also have a 22' mast that I may replace with something like a 25' or so, and small sail set. The short mast will be used with small sails for when I go to the lake with the larger family if I ever let someone take the boat out to learn on. For this purpose I think small sails will make it nearly impossible to capsize and easy to learn on.

    To get on the water sooner, I'm using a pair of Nacra 5.2 hulls until I finish those drawn in the original plans. Other than buoyancy forward I think they are an OK choice - light, cheap, all fiberglass so they're easy to repair and reinforce for this, and did I mention cheap? That was my primary reason for picking the pair of hulls up. They also allow the use of dagger boards, although my center hull already has a centerboard, so I probably won't acquire/build daggers. We'll see how it goes.


    Those are my wants. Basically a fun, reasonably quick boat for lake cruising. I will likely buy and keep a code 0 or some type of asym. spin and a set of performance sails for my own fun. But I don't intend to make speed a primary goal.
     
  9. Gary Baigent
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    Gary Baigent Senior Member

    Patrick, mon ami, who said I was going to have a motor? - carbon oars instead, anchor will be alloy with a few metres (small) chain, light warp, you're dealing with a minimalist crazy here, crew (total of 2 by the way) are only allowed T shirts and thongs. Cheers.
     
  10. cavalier mk2
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    cavalier mk2 Senior Member

    We'll have to call you Capt. Thigh instead of Bligh, Gary....It's enough to keep me in big boats....the cruel imagery of it all on my artistic sensibilities!
     
  11. patzefran
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    patzefran patzefran

    Excellent program, Gary ! I wish I coulld built that light, but I can't achieve ! Wil you use stressed plywood again ? keep us informed of your building progress, I shall do for my Strike 20., Some photos of my last build :
    https://www.dropbox.com/sh/eyvyt831b3eynxd/AABmqcvCQ4Wxz48YHiHDOcoDa?dl=0
    Too high weight for my taste, but very competitive compared to beach cats and much more geriatric to sail !
    As you can see from the rig I am also anactive A class cat sailor, unfortunately near retirement as I am getting close to 7 first digit ! full foiling without regulation is a younger matter !
    Cheers

    Patrick
     
  12. Gary Baigent
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    Gary Baigent Senior Member

    Neat and very attractive design, Patrick.
    Really I should not be posting my 6.5 stuff here in the under 20 foot thread - so will move across to the 6.5 to 7.5 thread. Where I can mention the unmentionable foil words.
    By the way, I'm an old farter too ... and should act my age.
    Cheers.
     
  13. waynemarlow
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    waynemarlow Senior Member

    No us older farts never should act our age, the older ladies wouldn't find us attractive if we did.
     
  14. cavalier mk2
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    cavalier mk2 Senior Member

    Who's talking about age? I was worried about sunburn....
     

  15. Corley
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    Corley epoxy coated

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