Proa Shunting in Heavy Weather

Discussion in 'Multihulls' started by NewSalt, May 3, 2021.

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  1. NewSalt
    Joined: Apr 2021
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    NewSalt Junior Member

    I have a technical question which would likely apply to all styles of proa:
    On occasion I have read concerns with regards to shunting in heavy weather; specifically, lying abeam with no way on. The proa defences I've read focus on lying beam on not being as dangerous as trying to tack through under similar conditions (although I'm not so sure about that).
    But, I don't understand why this would ever be an issue to begin with; can someone please explain this to me?
    Most pictographs of shunting do indeed have the proa turned down to a beam reach, likely to make the concept easy to understand.
    But, close-hauled on a proa in one direction is a broad reach in the other.
    It would stand to reason then that the proa could simply have the sheets loosened, then once almost stopped, they could be hardened in the other direction. Now on a broad reach with speed and complete control, the boat can be only briefly swung through a beam reach up onto the other tack - timed with a lull in waves/wind.
    This may lose more ground so not be ideal if beating off of a lee, but does seem to me to be much safer than a tacking boat.
    So, what am I missing?
     
  2. Blueknarr
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    Blueknarr Senior Member

    Welcome to the forum.

    Shunting usually takes longer than tacking. A shunting vessel spends a longer time at little to no propulsion or steerage than one tacking. A proa's stoping point is broadside to waves; a most dangerous position. A tacking vessel is slowest while pointing directly into the waves; with much less risk of being rolled over.
     
  3. NewSalt
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    NewSalt Junior Member

    Hi Blueknarr,

    Thank you for your response.
    Yes, that seems to be the accepted wisdom.

    That was kinda the jumping off point for my question. Why is that the belief/practice? Under normal circumstances it makes sense to head down to shunt while beating to reduce distance travelled for VMG, but I don't see it as necessary and I tried to describe an alternative. Is there a reason why this is not feasible? Perhaps it's necessary to prevent back-winding due to rounding up once the aft board is raised (which could be managed in rigs with moveable CE)?

    Your comment about length of time at idle is interesting. Do you think that this is inherent or the result of current rig choices? It would be stressful, but a cat schooner should be able to have reverse thrust on prior to actually coming to a stop.

    Thanks
     
  4. Blueknarr
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    Blueknarr Senior Member

    Shunting always involves a complete stop. Tacking can be completed while maintaining forward motion.

    Favorable vmg is not an element of the tack. Vmg only determines when a tack occurs
     
  5. NewSalt
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    NewSalt Junior Member

    I think that we're talking at cross purposes. I understand already what you are saying... I'm asking beyond that.

    I never spoke of VMG with tacking, only with shunting in either scenario (typically described heading down onto a beam reach, reversing onto a beam reach, then heading up vs. my suggestion of reversing from closehauled onto a broad reach, and then rounding from broad reach to closehauled when safest to do so).

    Similarly, yes, of course reversing direction involves a moment, whether a split second or minutes, of stopping - but if you reverse thrust before actually stopping, it will be clearly be closer to the former. Let's discuss this scenario instead of a 'just in case fallacy.'

    It is also simplistic to say that tacking maintains movement. In the conditions we're talking about, a large number of tacking boats will not be able to come through the wind and will wallow and backslip if they try. This may necessitate gybing around which can be dangerous to the rig and presents the beam to the waves twice. (I'm not promoting shunting by this statement, only saying let's compare like to like, so if we're going to discuss worst-case shunting...).

    I'm sincerely trying to appreciate this topic and I feel my questions remain unanswered.

    Thanks for the input.
     
  6. fallguy
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    fallguy Senior Member

    @rael dobkins

    is the guy who loves shunting..we'll see if he sees his name called
     
  7. Blueknarr
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    Blueknarr Senior Member

    Shunting from reach to reach puts the least stress on the rig.

    Reversing from closehauled would result in running not reaching.

    If faced with being rolled mid shunt: I would consider stuffing it up into the wave or turning down while I still had steerage. Then complete the shunt.

    A wallowing tacker doesn't have to jibe. It could return to it's previous course and tack later or continue tacking. Back winding sails and using the steerage provided by being pushed backwards has helped me thru many tacks
     
  8. NewSalt
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    NewSalt Junior Member

    Okay perfect - this is the sort of input I'm curious about. Can you elaborate please?

    Sorry about my terminology. To me a run is opposite being in irons, and a broad reach is opposite close hauled, but maybe that's because I've been on poor pointing boats.

    And yes, another option shunt-wise would be to point from closehauled way down to a broad reach/run, then reverse direction to closehauled. Functionally it avoids being stopped beam-on the same as what I proposed; if it can be ascertained that shunting is feasible on angles other than beam reach to beam reach, a discussion of merits between either of those options would be interesting.

    Theoretically, when you do your back-winding and reverse steerage manoeuver, you've just shunted twice in that "tack" - at least a proa is designed for it. :p
     
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  9. Blueknarr
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    Blueknarr Senior Member

    I've learned the art of sailing backwards. For years I had an upwind slip in berkeley, took a bit of practice backing into it. Never learned how to back upwind out of it.

    Tacking can be from any point of sail to any other as long as the bow passes thru the wind. Chicken jibing is tacking.

    Too many variables involved to argue the pros and cons of off angle shunting. They would certainly take longer both in time and distance. There would also be greater strain on the vessel, rigging and crew. Their usefulness is limited.
     
  10. NewSalt
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    NewSalt Junior Member

    Okay if you aren't interested in discussing offbeam-reach shunts that's fine, but that is literally the whole reason I started this thread.

    Anybody else able to explain why shunting while not on a beam reach would inherently cause more stress to the boat? (I'm not intuitively seeing it) Is it just that the shunt would have to be done more quickly before the proa reorients itself, so that you'd get more of the sudden full power, kinda like with the AYRS rig but less extreme? And are we talking orders of magnitude more, or within the ability to engineer for?
     
  11. Blueknarr
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    Blueknarr Senior Member

    The more off angle the greater the strain.
    Starting to shunt while slightly pointing up wind should be manageable.
    Shunting from a run would be similar to an unmanaged jybe and could be orders of magnitude greater strain.
     
  12. Clarkey
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    Clarkey Senior Member

    This could be a really interesting thread. I think that shunting from close-hauled to a broad reach is probably a very practical proposition with more 'westernised' rigs but may be difficult to achieve with an oceanic lateen?

    I suppose the other thing I might question is why is it so bad for a proa to lie beam on to the seas? A decently beamy proa with an ama of appropriate buoyancy and weight may even be better off like that than bow on?
     
  13. Blueknarr
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    Blueknarr Senior Member

    Yes.
    One of the problems with generalized discoursions is that the devil is in the details.

    Some sail plans would allow for better off angle shunting than others.
    Some masts and rigging would endure more abuse than others.
    Some proa's are at greater risk of pitch-poling or broaching than others.

    Too many variables.

    I have yet to see a vessel that I would like to spend time beam to the seas on.
     
  14. NewSalt
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    NewSalt Junior Member

    Good point. I think if I had a crab claw, I'd be lying to a sea anchor long before waves would threaten dumping me.

    I keep coming back to either an unstayed schooner or possibly a Gibbons (+/- pivoting mast, but without Dierking's sailboard mods to allow for reefing). I think that both should allow for gradual feathering on of power and the former would provide CE control.

    Everything in a proa is so interconnected. An Atlantic(ish) with a >120% ama should be very difficult to roll if not overpressed since whenever the vaka lifts it should skid on the shallow ama. I love the purity of the Pacific concept, but I can't work my mind around a leepod being ideal for wind capsizes but a tripping hazard for wave-induced ones.
     

  15. rael dobkins
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    rael dobkins Senior Member

    How about a mono lying a hull? It's beam to, and it's rocking your world... Yet some sailors use this technique.

    Multies actually don't roll at all, so being beam on is very different to a mono beam on. Multihulls are rafts and they can sit pretty level in rough weather. On my small Proas I have been in pretty rough conditions here in the Black Sea. I remember the same conditions years ago, with a mono were much harder.....

    My rig shunts fast, then I have to move over the steering oar. The boat, after the rig has gone over and landed on the new bow (that takes under 5 seconds) is already oriented bow to the wind, just a little, say 70 degrees, once I sheet in it heads off to windward on it's own, that's when I move over the steering oar ( during the shunt it has been lifted out of the water) and then I can get the boat cooking, as I sheet in and steer the acceleration is like a sport bike, it takes a couple seconds and you're flying again.

    Shunters are the strongest of multies and the stablest of monos. A properly rigged shunting rig is never stressed, the stay and shrouds are so widely based that it's never coming down. (back winded is another story, and each rig is different under thaose conditions, my 'LaSHuNK' keeps sailing back winded on a close reach, and I just gybe back to Pacific Proa mode) Proas are strong! That's why they shunt, they don't shunt because it's cooler than tacking. They do so because they receive the wind, from the same and only side, yet mast is placed on Vaka, leaving bridge unstressed and free to flex... A low profile yet buoyant ama, as it lays beam to, will let the wave ride over it rather than take the full impact like a Catamaran hull would. That's the Amas job truly, to flatten the ride for the Vaka, and it does it well.

    From a close reach to a broad reach??? Complicated.... Traditional shunting rigs cant do it. Since vessel is sailing forward, the rig is loaded, There's no way that sail could be moved aft since it's full of wind. That's why Proas bear away to a beam reach, and let sheets fly, the free sail can now be easily moved.

    On Paper a Bermudan rigged Proa with lifting rudders could go from a close reach to a broad reach. It would role up the head sail, probably head up till it's luffing, switch rudders (the lifting type) sheet the main in and head off then unfurl the new head sail.... BUT would it work on water??? Probably not, a single sail at mid ship will act like a windvane, so as you pull the sheets the hull would rather swing around the sail than the sail would swing round the hull....

    Meaning, a boat that is not sailing, and a sail aloft stuck in the middle of a breeze, while you are pulling on sheets attempting to change sail angle to weather. What will truly happen is, the hull will turn as the sail stays oriented to the eye of the wind developing zero drive.

    I have noticed how fast my boats turn around my sails when I'm not sailing, and that here is the problem, I think, in order to shift rudders and change sail angle, this boat must stop, since it's in water, a wind is blowing, I doubt it wont end up on a beam reach once you sheet the sail over.......

    Keep Shunting,
    Balkan Shipyards

    Proa "Make O'Break" in a big Black sea gusting in the 20ies and over 2 meter steep waves piece o'cake, I even heave to beam on and the boat becomes a very comfortable platform.... It's a multihull, No it's a Proa!
     
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