Small trimarans under 20'

Discussion in 'Multihulls' started by Doug Lord, Jun 24, 2012.

  1. Gary Baigent
    Joined: Jul 2005
    Posts: 2,913
    Likes: 73, Points: 48, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    19 grand US is around 29 grand NZ - for an 18 foot boat.
    But I forget, you've an abundance of wealth, hence your fleet of toy sized pond fantasies?
     
    Cholsson likes this.
  2. Manfred.pech
    Joined: Apr 2010
    Posts: 541
    Likes: 55, Points: 28, Legacy Rep: 319
    Location: EU

    Manfred.pech Senior Member

    The Ausralian Ian Smith has built this little folding and planing Trimaran with a split surf board and a planing main hull (AYRS, project Windrigger PROJECT WINDRIGGER http://fionamsinclair.co.uk/yachts/smith/page25.htm ).

    [​IMG]

    [​IMG]
     
  3. revintage
    Joined: Nov 2016
    Posts: 51
    Likes: 4, Points: 8, Legacy Rep: 10
    Location: Sweden

    revintage Junior Member

    Manfred, the split surfboard must be the way to go. Actually got inspired by the split surfboard from Waynefarlows F16 tri on page 63. Found a dirt cheap short surfboard and have just started collecting the other stuff for this Frankentri project. No carbon needed ;-) .

    Used aluminium tubing when building new beams and wings for our two Nacras, so those parts will be easy to build and the workshop capacity is good. I also have a Tornado and a Nacra mast to cut down, even if they probably are to stiff and heavy for this. Was also thinking of cutting down a Tornado main I have.

    My main concern at the moment is what foils to use. Will either use Hydrotroptere style or V-foils like Doug Halsey, the latter type seems to be easier to build.

    IMG_20180727_201505_95398143_thumb.jpeg IMG_3247 2.jpg unitop.jpg
     
    Last edited: Aug 10, 2018 at 9:08 AM
    Cholsson likes this.
  4. Manfred.pech
    Joined: Apr 2010
    Posts: 541
    Likes: 55, Points: 28, Legacy Rep: 319
    Location: EU

    Manfred.pech Senior Member

    Yes, that is the other way - to take two smaller boards as Waynemarlows did - and Randy Smythe in Everglades Challenge 2018 with a special bottom profile. The tri
    SYNERGY was very fast but seemed to have not enough buoyancy for sufficient static lift (besides hydrodynamic lift) with the surfboards. He capsized.

    [​IMG]

    [​IMG]

    [​IMG]
     
    Last edited: Aug 10, 2018 at 4:27 PM
    Cholsson and Doug Lord like this.
  5. Dolfiman
    Joined: Aug 2017
    Posts: 421
    Likes: 203, Points: 43
    Location: NICE (France)

    Dolfiman Senior Member

    I think that we can develop the necessary volume on the upper side of the surfboard to provide the needed lift by buoyancy when the speed is too low for some reason, here attached 2 examples.
     

    Attached Files:

    Manfred.pech and Doug Lord like this.
  6. waynemarlow
    Joined: Nov 2006
    Posts: 397
    Likes: 29, Points: 28, Legacy Rep: 134
    Location: UK

    waynemarlow Senior Member

    You have to decide whether you want the wind surf boards to act as training wheels and you want to rely on other means of stability such as a trapeze as I have done, or you want to utilise the full stability benefits of high volume ama's with a smaller central hull.

    The plus for the full size Amas are well known on larger vessels, but my gut feelings are that in this under 20ft zone, the benefits of light air sailing on the central hull, only with the RM of a fat arsed body out on the trapeze, far overcomes the beach handling issues of a full on weight of 3 hulls. Its a real joy to have some stability when things go wrong, but to be mainly sailing on 1 hull only with the Ama just skimming the water, something that we try to achieve at all times in beach cat racing, I think its as fast around a course and yet with appreciably smaller sail area.

    Something we need to consider more is to consider placement position of the surf board. Back opposite the skipper is probably halving the best RM of these minimum volume boards, than if we had them much further forward, Tris like to have the Ama buoyancy as far forward as possible.

    Certainly from my own boat its clear that more volume is needed to the rear than usual as I have now moved the mast base forward by nearly 300mm and although its much better I still need a tad more. I think a blade jib would overcome that last bit of issue I have. Although the tiller is feather light and balanced, the waterline is still down at the back end. I have two options, widen the back end or lengthen the hull.
     
    Corley and Manfred.pech like this.
  7. waynemarlow
    Joined: Nov 2006
    Posts: 397
    Likes: 29, Points: 28, Legacy Rep: 134
    Location: UK

    waynemarlow Senior Member

    Be aware by upping the volume of the Ama, you have less chance of righting the boat unless you make them hollow and you can sink the Ama as per the Weta.
     
  8. upchurchmr
    Joined: Feb 2011
    Posts: 2,681
    Likes: 64, Points: 48, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Once upon a time, larger tri's were proposing recovering from a capsize by sinking the bow and rotating about the front beam.
    Is this a possibility?
     
  9. Gary Baigent
    Joined: Jul 2005
    Posts: 2,913
    Likes: 73, Points: 48, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    Lock Crowther tris like the Kraken 33 and 40 had low volume floats for this reason. However I watched from close behind, Krisis (a Kraken 40) get hit by a williwaw off the city and the crew all fell downhill with flailing arms and legs before they could reach and release the cleated? sheets. Actually it happened very slowly, float buried slowly but the crew stood like zombies and let it all happen. The highly competitive skipper on our boat just laughed ... and we won the race after the the Krisis crisis. Here is a shot I took of the Kraken 40 before race start.
     

    Attached Files:

    Last edited: Aug 11, 2018 at 5:32 AM
    Manfred.pech likes this.
  10. revintage
    Joined: Nov 2016
    Posts: 51
    Likes: 4, Points: 8, Legacy Rep: 10
    Location: Sweden

    revintage Junior Member

    As Waynefarlow points out the amas are just to be used as training wheels which means you have to contribute to RM with your own body. They are not for sailing with lifted center hull. As I pointed out earlier, my intention is to adapt foils in a later stage which means the amas will only be used before lift off and should be of planing type.

    Synergy looks interesting using the same concept as Sizzor.

    Waynefarlow: I note your beams are not very wide and the tri needs trapezing to get enough RM. As I, due to age, no longer have the stamina to use the trapeze, my choice is wider beams with the weight penalty this gives. Do you have any data of your boat(sail area, sailplan CoE-height, and beam)? You might have given them before, but I can´t find them. Have made a simple Excel spreadsheet for comparing non-lifting tris, that show design wind when balanced(no amas touching water). A little coarse, but good enough for comparing.
     
  11. Gary Baigent
    Joined: Jul 2005
    Posts: 2,913
    Likes: 73, Points: 48, Legacy Rep: 509
    Location: auckland nz

    Gary Baigent Senior Member

    And Noel Fuller built angled floils (he called them, half foils, half floats) on his 4.5 metre Sabrina way back in the late 1970s - and sailed it from Auckland to Bay of Islands.
     

    Attached Files:

    Last edited: Aug 11, 2018 at 6:08 AM
    revintage likes this.
  12. revintage
    Joined: Nov 2016
    Posts: 51
    Likes: 4, Points: 8, Legacy Rep: 10
    Location: Sweden

    revintage Junior Member

    Anyone here who knows what foil profiles where used on the hydroptere first and later prototypes? Question is also windward performance with this type of foils?
     
  13. Doug Lord
    Joined: May 2009
    Posts: 15,161
    Likes: 187, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    Manfred.pech likes this.
  14. waynemarlow
    Joined: Nov 2006
    Posts: 397
    Likes: 29, Points: 28, Legacy Rep: 134
    Location: UK

    waynemarlow Senior Member

    13.5sqm main on 8m mast, 2.4 wide beams so outer of the floats are about 2.7m as to CoE height, the sail is pretty "oblongish" so I would be guessing 4m or so.

    Don't give up on using a trapeze, when they are set at the right height ( you can clip in whilst still sitting ) and you trust them you can simply push out with your feet and you swing outwards, very little energy needed. Once out you use less effort to maintain stability as well. Hey I'm 62 and find it easy :)
     

  15. revintage
    Joined: Nov 2016
    Posts: 51
    Likes: 4, Points: 8, Legacy Rep: 10
    Location: Sweden

    revintage Junior Member

    Haha, I´m 67 and quit Tornadoracing 1985. At that time it wasn´t even allowed for me as skipper to use trapeze, so I am still at that stage ;-) . Anyway rebuilt a Nacra 5.5 this winter with wider beams and provision form singlehanding, third picture from top. So I might try soon.

    About design wind you have done it like it should be, at ca 6,5 m/s about the same figures I get for a 29er.
    wings.jpg
     
    Last edited: Aug 11, 2018 at 10:50 AM
    Cholsson likes this.
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.