40F Folding Proa Harryproa

Discussion in 'Multihulls' started by Zulu40, May 2, 2016.

  1. Zulu40
    Joined: May 2015
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    Zulu40 Junior Member

    Impressed by the appearance last week of this 40ft folding proa design by Denney. Follows on from the Cruiser series
    Thought Id pass the info link on since boats of this nature are somewhat rare


    http://harryproa.com/?page_id=1568
     
  2. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Has some really good features for sure

    "The prime requirements were for a low cost, easily handled boat that would sail well in light air, be safe and easy to sail in heavy air and be suitable for the client and his wife to live on for extended periods. Secondary requirements were an open saloon that could be closed up and the ability to fit in a mono slip, a container or onto a trailer. Plus a tender that was capable of long trips at high speed in adverse conditions."
     

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  3. Gary Baigent
    Joined: Jul 2005
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    Gary Baigent Senior Member

    Hey Rob, that rig belonga me.
     

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  4. rob denney
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    rob denney Senior Member

    This was taken in 2004. '-) Worked really well, but was a handful (and 2 feetful) when I was sailing solo in a breeze with 2 sheets and 2 rudders, so I went from schooner to una and put one of them in the middle. All the cruising harrys now have them. With a wishbone boom, they are safe and simple and extremely easy to sail, primarily as there are no leech loads on the mainsasil. Instead of busting your balls winching the main in to get leech tension, all the mainsheet does is alter the angle of the sail. A winch is barely required, even with a 2:1 mainsheet.

    Newick beat is both to it with Cheers. By about 40 years!
     

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  5. Gary Baigent
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    Gary Baigent Senior Member

    Yeah, just joking.
    We can go back a long way further than Cheers with the rigs of the Papuan, Torres Strait and Niningo Lagoon designs - how old are they, one, two millennium, more? The 4th and old photograph is very interesting, a Daru trimaran.
    Just being a smart arse - because I have a copy of Haddon and Hornell. Cheers.
    Actually rethinking the Cox's Bay Skimmer (which was sailing pretty much the same time as your twin rigged proa); sailing that boat was easy ... ha, ha, becuse it was conventional monohull ... with one dagger, one rudder. Sailing solo I had to reef foremast main early but with two aboard and the hull being so flared, you could carry full sail into around 15 knots true. Yes, the rig overpowered the boat but it was simple enough to sail. I shouldn't have given it away ... but have too many boats.
    Sorry for the hijack,
     

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  6. sigurd
    Joined: Jun 2004
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    sigurd Pompuous Pangolin

    Hey that rig looks like it could be similar to the one I'm working on. I made a thread in 'sailboats' called 'how much kick'. Maybe you want to look Rob. Maybe you don't want to divulge too much about your rig details, just put me down as interested. I think I have got mine sorted out on a basic level, not including scantlings and such but trimline routings and such. Nice boat as always Rob, only, why not 3 more meters in the lee? That a marina thing?
     
  7. rob denney
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    rob denney Senior Member

    Lee hull length is limited by having to fit the whole thing, including the tender, in a shipping container and being able to tow it a couple of miles for winter storage with the family car.

    The rigs are similar as they are both tall and high aspect ratio. Yours should be more efficient, but heavier and more expensive. Both require twist control. We are doing this with a wishbone boom and the outhaul" for the main leading to the base of the mast. ie, tension the outhaul, the foot and the leech both get tighter. A second control limits the foot movement. This is simpler than a wishbone attached to a wing mast, which has a lot of control issues, as others have pointed out. Easiest structurally is to use a snotter and trim the mast separately from the sail. Use a sizable purchase so that as you trim the sail in and out, you can also change the aoa of the mast.

    To control twist with a vang or gnav will require big loads and a strong boom. An end of boom mainsheet would work better. If you can't use one, then a wishbone is best.

    Look forward to some pictures!
     
  8. sigurd
    Joined: Jun 2004
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    sigurd Pompuous Pangolin

    It would be an incredible selling point for me to have a boat where I could command 'release the snotter!'
    But I don't really see what you mean with that suggestion.

    'end of boom mainsheet'
    Like Groucho Marx you mean, sheet from end of boom to large round track, looks super, just not when the mast is stepped in a narrow lee hull.

    To critique 40F's twist control (if I understand correctly): Two different trims, camber and twist, are on the same rope, and moreover, the camber goes down as the twist goes down, and vice versa, which is the opposite of the dependence you'd want. IE when you want to depower, you want to increase twist and decrease camber.
    Or maybe your rig is working more like a windsurf rig, utilizing the bendiness possible with a round mast?

    'A second control limits the foot movement'
    What does that mean? A downhaul? Or a rope pulling the foot forward toward the mast?

    What do you mean the sail is tied to the mast, instead of a track, is it like a mast sleeve but with lacing?

    EDIT: I put up a pic of the hull bottom, very inspirational I know. Hope to put more up sooner rather than later.
     
  9. rob denney
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    rob denney Senior Member

    The boom is 1.8m/6' above the deck and ~horizontal. It is slightly longer than the sail length from mast to clew. There is a single line from the sail clew, through the end of the boom and down to the bottom of the mast. When this is tightened, the leech stands up, the mast bends and the bottom ~quarter of the sail is flattened. To control the flattening effect at the bottom, a line runs from the mast at boom height to the clew. Tighten this to increase the draft.

    With a bit of fine tuning of boom length/angle, adjustment of this line may only be required in light air. It may even be redundant, which will be a saving as otherwise it has to be tacked.

    Most wishbones require the boom to ~bisect the angle between the leech and the foot which means the lee side of the sail has a large impediment to the air flow and the attachment point is way up the mast, requiring extra mast stiffness. Hopefully, we can avoid some of this.

    The sail is tied to the mast with a lacing similar to a sleeve, but less friction. The lacing tension is adjustable for the tapered mast and reefing and it has a halyard lock at each reef point which doesn't require a string to release or lock and can be released if the halyard breaks. The attachment of the end of the square top diagonal batten to the mast is a possible problem, which may need a fitting to make it work.

    From your other thread: If the boom is attached to the mast with a snotter and the sheet and leech controls are attached to the other end, any bending is because the boom is too small in section or doesn't have enough material. Booms vanged (or gnav'ed) from the middle and curved booms (wishbones) need a lot more material/size than straight booms.

    I built a wishbone boom for Bucket List, weighs 15 kgs. The replacement straight one will be <5. This shunts to windward of the mast, all going well. Neither has been tested yet.
     

  10. sigurd
    Joined: Jun 2004
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    sigurd Pompuous Pangolin

    Doesn't this increase boom compression more than necessary?
    Why not 1) Vang from near boom end and 2) Outhaul, route it however you want for dependency on other trims (if you route it to mastfoot, along vang rope, camber will increase when vanging on).

    Why can you put the wishbone more horizontal than 'most wishbones'?
    The reason they go downwards is to reduce compression on them, due to vang/leech tension? Do you just compensate with more boom material/cross-section? Or what did I miss.

    Wow, how does that work?

    Do you mean it ('gaff batten') is the only batten that presses against the mast? Camber inducer windsurfer style, would that work?

    'Gybeshunt'? Cool! Oversheet, which will stop, then reverse and help turn the boat - sail gybes - pay out sheet on new tack. If you never do the 'ordinary shunt' (leading edge towards wind) you only need the one sheet?
    But you can't then use 90' (boom pointing to leeward) sheeting angle...?
     
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