Can a Pacific Proa Benefit From Lifting Foils ?

Discussion in 'Multihulls' started by mcm, Feb 5, 2015.

  1. cavalier mk2
    Joined: Mar 2010
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    cavalier mk2 Senior Member

    "Yeah, but not much point in riding over the logs only to have them wipe out the rudders, daggerboards and foils! Plus you get more pitching and less waterline length, which is less speed. I prefer vertical bows with foam collision pads and angled bulkheads. And of course, kick up rudders and no daggerboards."

    Hey Rob, I was hoping this thread would catch your eye. Lots of good insights.

    Up here in the land of forests to the sea we get to slalom a lot, the #1 best thing to do is miss. This is what I've noticed with conventional bows up to a certain point. They roll the drift under and the forward sections roll it to the side before it contacts any daggers etc... A flat bottomed punt wouldn't do it but anything with a reasonable shape does. Of course a ama without foils is safer yet. Crush boxes or centerboards and kickups take care of the rest. Believe me we do get to practice. To me slide on foam noses make sense for plumb bows because if you do go crunch the drag really increases and a yard can be a long way away.

    For rudder T- foils they should be on whichever hull has the rig, vaka on a Atlantic, ama on a Pacific or Harry to reduce the pitch and diving.

    I still think these boats should be set up to tack for short boards, the proa concept seems best for long hauls. How fast do Harrys shunt ? I'm presuming you stop and set up for the new course ?
     
  2. cavalier mk2
    Joined: Mar 2010
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    cavalier mk2 Senior Member

    Forgot to mention the other challenge with surface piercing rudders, foils etc... in the PNW. 95% + of everything you will encounter is riding on the surface (assuming you avoid the bottom, rocks etc...) Most of it is sticks, logs and large banks of seaweed and kelp.
    If the foils, rudders etc...go through the hull or are on a transom they are protected from most impact and fouling. Of course flying hulls negates this feature.
     
  3. rob denney
    Joined: Feb 2005
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    rob denney Senior Member

    Thanks. Most of them have been learnt the hard way. Today was a good example. We were testing the foil on the kite proa. Flew at about 8 knots (as expected) and could be steered very easily by moving the take off point for the kite, so no rudders required. However, the side loads were more than anticipated, so we punched a sizable hole in the small hull. Fixable, but by the time we got home, the hull was almost submerged.

    For sure with slow boats, not so much at 20 knots, particularly with crush boxes where the rudder is likely to impact the hull when the crushing happens.

    This is usually the hull that does not lift, so I agree, but given a choice of the hull that stays in the water or the hull with the rig, I would put the rudder foils on the one that stays in the water. A loaded rudder foil leaving the water has interesting results.

    To tack, you need equal length hulls or one tack will be slower than the other. And more dangerous.
    I solo shunted a 12m harry in 8 seconds, from dump sheet to sailing at full speed. The first timers 13 minutes into the video at https://www.youtube.com/watch?v=wftyqI2aJlo took about 15 seconds for a shunt. This will be quicker (and drier) with the new rudders they are installing. Shunting downwind (gybing) is slower and has more time pointing the wrong way. With a good crew both are reduced, and if you were racing, there are a number of tricks to speed them up further.

    Maybe. Kelp banks, seaweed and plastic bags won't be shifted by a long skinny hull going fast and twigs etc are not an issue for surface piercers. One of the benefits of beam mounted rudders is you can see anything on them, and easily remove it with a notched stick. Far less hassle than lifting a blade that you cannot see, "just in case" something is on it.
     
  4. cavalier mk2
    Joined: Mar 2010
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    cavalier mk2 Senior Member

    Thanks Rob, we aren't terribly slow for an antique cruising tri and the amas are skinny so I'll hold out for conventional bows, better to slow and roll an impact rather than hit square and push for me.

    The tacking I'd still rig for the tight channel options, reducing sail if needed would be easier and quicker than the stop and goes.

    Excuse the poor copy but what do you think of this proa rig?
     

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  5. rob denney
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    rob denney Senior Member

    Fair enough, and the right thing to do for outriggers with no boards, rudders or foils.

    Easier and quicker until something goes wrong such as tacking a cat up a narrow channel and getting caught in irons or an override on a winch. Shunting a well sorted proa it is very difficult to get into a situation you cannot easily get out of. Hopefully i can take you for a sail in Bucket List when we have one up there and show you how it works.

    Apart from all the usual problems with stayed masts, it is good for small proas, not so good for big ones.
    It works by tensioning the front edge of the jib and sheeting the back end. When you shunt, the sail does not move, but the lines swap roles.
    The problems are the same as for any headsail. Large forces (particularly compression in the mast) and difficulty keeping the luff straight. The bigger the boat, the worse these problems become. I also worry about placing the boat side on to a big breeze during a shunt, when the sail would either flog or fill, although 2 of the owners who have these rigs reckon neither is a big problem.
     

  6. cavalier mk2
    Joined: Mar 2010
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    cavalier mk2 Senior Member

    Thanks Rob, really good point about shunting safety, having forward and reverse in a tight spot is good. I was just thinking about speed and convenience with the tacks and jibes.

    I would be interested in seeing how it all works when you get up here. If you like I'll take you for a retro sail, we have preserved Oz history in the Northern hemisphere.
     
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