Single-handed Skiff

Discussion in 'Sailboats' started by nacra5.8, Jun 17, 2012.

  1. nacra5.8
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    nacra5.8 Junior Member

    These should work Doug
     

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  2. Doug Lord
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    Doug Lord Flight Ready

    singlehanded skiff

    Alright! My opinion-first impression-is that perhaps the bottom is too rounded?
    However, the rudder T-foil will help with dynamic stability and could allow this hull to work well giving you a low wetted surface hull for light air and reduced displacement and increased stability in wind. The low wetted surface hull would compensate for the extra t-foil wetted surface in light air. The t-foil on an I-14 produces over 90lb(400N) of lift upwind @ 10k boatspeed allowing the crew to move back and reducing wetted surface. Looks like you may be close.
    I'm with GG on mixing wood with carbon/foam and I'm not too excited about mixing kevlar in there either. I'd go all carbon and foam if possible.
    Good Luck-keep us posted!

    You might consider posting some of the design ratios-see Eric Sponbergs gift to us all below. The Bieker page is just part of a much larger document that is too large to post here(I can try e-mailing it if you want it). It has a lot of tech info on the I-14 foil.
    The T-foil article is by the guy that designed the SK skiff.
     

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  3. nacra5.8
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    nacra5.8 Junior Member

    Alright, as I said definitely I'll go carbon/foam for the hull. kevlar I can get at really low prices compared to carbon, or even s-glass, so I wanted to take advantage of that. It sounds like you want the volume a bit lower in the boat though, more of flat bottom? I'll play around with it, thanks.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    =====
    Just looking at Biekers I-14 hull I think maybe you're ok. Your boat is much lighter and for the reasons I mentioned earlier you may be ok-if you're going to use a t-foil. Look at the SK hull... What is the entry angle of the bow at the waterline?

    Kevin Ellway's Arup skiff: http://arup.com/Home/Homepage_Skiff.aspx
     
  5. nacra5.8
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    nacra5.8 Junior Member

  6. JRD
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    JRD Senior Member

    It looks to me, like the proportions of an international canoe. Without having squared off chines i think it may get a bit leary at any kind of speed. (Ever steered a laser fast off wind in waves?)
    Theres lots of online technical discussion about ICs which will guide you if thats the direction you want to take.

    I'd steer well clear of Kevlar, you will regret every single cent you saved when you are trying to cut the stuff and the second you find you have a high spot and need to sand it down.

    The RS700 is a pretty well developed racer. To beat one that is well sailed will take more than just more sail area, more length, wider wings. Its the whole package that counts. Unless you are a very experienced dinghy / skiff sailor (im not suggesting you aren't) the wings and narrow waterline will probably make you slower around the course, as its going to be harder to keep it dialled in all the time. (Have a read of the thread on SA below, which details a similar idea with some outcomes very much unexpected to the purchaser)

    http://forums.sailinganarchy.com/in...4&hl= rogue skiff&fromsearch=1&#entry3196664

    PS - Dont get me wrong, I think its a great idea, its just not as easy as it sounds and you can spend alot of time and money finding this out if you dont get off to the right start.
     
    Last edited: Jun 17, 2012
  7. nacra5.8
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    nacra5.8 Junior Member

    JRB- Thanks for your input. Kevlar-wise, I have the special shears, and it's going on the inside of the hull, which should mean less sanding, but I think I could just substitute glass if needed. About the narrower waterline, I've always heard that it's generally better to go longer and skinnier- as I mentioned I also worked on a 12-foot long, wider design- maybe I should split the difference at make it around 14 feet? About sailing it, I'm a fairly experienced dinghy sailor- and actually the rig is a highly developed setup off of a different boat- really high aspect for its size... the kite is also significantly bigger than the RS700s (225 vs 160)- the T-Foil should come in handy again here. I really just want to be somewhat competitive with this guy, so that I have someone to sail with. The only other oft-sailed high performance boat at our club is a Weta, I'm not sure where I'd fit in with that. Again, thanks for all of your guys help.
     
  8. JRD
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    JRD Senior Member

    Hi again,

    I have two questions - what is the rig off? A Nacra 5.8 by any chance..... (just guessing here).

    Have you sailed the RS700? If not, see if he will let you take it for a blast. Thats going to be your baseline for performance and more importantly sailability. I may have missed it in your original post, but are you planning to trapeze as well?
     
  9. nacra5.8
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    nacra5.8 Junior Member

    yes, definitely a trapeze. Rig is not off of a 5.8, it's from an I14 (if I can find one) with cut down sails.
     
  10. Steve Clark
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    Steve Clark Charged Particle

    Look carefully at your stability curves.
    Make sure you have enough freeboard so that your beam doesn't fly out the window at low heel angles.
    Make sure you have enough volume aft to have some stability when you are back in the bus. On a renegade vessel such as this, nuances of hull shape will not have much of an effect one way or the other because you will not be sailing against anything. So as long as it floats high enough and is more or less boat shaped, you will probably be fine. What will kill your dreams is weight and improper structure.
    There is a bit less freedom in designing within a development class rule, but there is more support and people to sail with when you are done. Both the IC and 14 are active on SF bay out of Richmond.
    For projects like this, 200 g/m^2 carbon cloth and 55kg/m^3 foam is just about all you need.
    SHC
     
  11. gggGuest
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    gggGuest ...

    It strikes me as a light airs lake boat sort of shape, but I'm not sure I can really define why.

    Pay considerable attention to what SHC has to say as he has been down this sort of road a few times.

    Personally I would have chines and flare aft, at least partly for stability when heeled: if you are heeled over and trying to maintain control its helpful if the boat gets more stable rather then less. Most extreme exampple is the Kiwi 12 foot skiffs.

    To my mind you get nicer lines forward with a raked bow, and less tendency to go into hollows. If you are having a bowsprit on it the extra length comes off the sprit, so the structure isn't wasted weight.

    Weight carrying is an important issue: if you are substantial I would go longer than 14 feet.

    I think there's a possibility that you may be a bit too V'd on the centreline. Although Bethwaite goes that way no-one else does, and I think you're more Veed than Bethwaite.
     
  12. Cheesy
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    Cheesy Senior Member

    Im guessing you are talking about these 12s/Rs
    http://www.leechboats.com/data/L3/L3_render.jpg
     
  13. JRD
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    JRD Senior Member

    Agreed that the flare will help with reserve stability, but the wing angles will need to be quite high to allow that stability to be enacted as the boat heels before the wing tips hit the water too.

    Hey Cheesy, good to see another kiwi here. Im not sure which design of 12 GGGuest is talking about, but in my mind the older 12s (Woof and Aero hulls) had even more noticeable flare along the whole length. I havent sailed any of the later 12s, but I'm certain the Aero shape was alot more forgiving than what they sail now for that reason.

    A thought for Nacra5.8. With a single hander you need to think a bit more about launching and capsize recovery, as there is no one to hold the boat steady when you climb on board. While you may have the right body position in the boat when you are sailing, you will need enough bouancy and stability to get back on board from the water, which can be from some pretty funny angles at times.
     
  14. CutOnce

    CutOnce Previous Member

    Hi Nacra5.8!

    We've talked by PM, but I think it worth mentioning a few things on the open forum.

    I've built a similar boat with similar goals, and was happy with the results.

    Would I do so again? I don't think so, based on the lessons learned in the process. I should have listened to Steve and Willy Clark when they tried to convince me to build an International Canoe. Not that my boat wasn't great compared to similar efforts - it is and was comparable to SwiftSolos, Mustos and RS700s. But sailing alone is not easy or fun without a group of people sailing similar designs.

    Ramp launching and retrieving the boat is a REAL challenge, especially in a crowded venue. Things that are trival in two man boats or more stable designs are a real problem. My boat can't stand up on it's own for two seconds. Therefore you can't let go of it to pull a dolly off the ramp, or even easily climb in.

    Capsizes were incredibly tough - climbing up on the board was an Olympic class athletic event - until I figured out a better way and added foot loops on the rails for capsize assistance. It was not unusual to go through five or six capsizes in an hour - and in high winds the boat would be back over a few seconds after you got it righted. Exhaustion is a real problem.

    Really spend a lot of time figuring out and refining systems -the kite sock/tube, the launcher mouth and the angles involved are critical in a single hand asm boats. If gggGuest is who I think he might be, he's built a very fast single hander as well.

    Much as you may like (as I do) sailing alone, sailing a single hander trap/asym boat is NOT an activity that is easy alone. Rescue boats are a welcome presence, especially if exhausted and in cold water. Launch - retrieval help is incredibly welcome - certainly better than having to intentionally capsize your new rig across the dock while putting your own dolly down the ramp and in the water - and having to right the boat from the dock to jump in and guide it on to the dolly alone.

    --
    CutOnce
     

  15. Doug Lord
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    Doug Lord Flight Ready

    N5.8, have you calculated the lift you're looking to get from the rudder t-foil
    upwind at "X" speed? Will you be able to adjust the angle of incidence from the tiller or ext. tiller?
     
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