A proa and aero junk or split rig questions?

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  • 17 Jul 2018 19:09
    Reply # 6385800 on 6368944

    Hi Mark

    I was a bit surprised at how many members here have put some thought into proas myself, makes sense though I suppose, both the junk rig and the proa are way outside the box that most folks seem to be comfortable in.

    I wish there had been more development on the aero junk it's such an intriguing concept and a cool looking rig, I'd love to build one with cherry wood battens and a tanbark sail, it'd be a work of art :)

    I fell in love with Jezero the first time I saw a pic, what a lovely little boat, and only weighing 1000 lbs/450 kilos all up too. my dream proa looks a lot like her, but with a junk rig of course :) On the other hand, while I think harry proa is a brilliant Idea, aesthetically speaking it does nothing for me.

    I had read something about Russell using both rudders sometimes, they must be shaped like leeboards or the one at the front would be running backwards. I suppose that the rudder tab wouldn't move at all if the board was only part way down in the trunk so it would work fine to balance the proa.

    @ Graham, no, I'm sure you're right, I'm missing something fundamental, I thought it was all going too well :) I'm going to build a model of just the mast and rig fairly soon and see if I can't put my finger on it.

    what do you think of the idea of mounting a split junk directly on the mast like an aero junk rig would be? it'd eliminate the problem of where to run the tails of the halyard and yard hauling parrel, there's no reason you couldn't use a jib with the split junk.

    If it did work well unstayed there's no reason one couldn't run a stay to hang a jib off of just for light air I suppose.

    I'm still undecided on what the bottom should look like, I'd like to have a flat bottom, it seems like it would keep the bows from diving as much, but I know what one sounds like hitting a wave a 4 knots, I can only imagine what a flat bottom sounds like hitting a wave a 17 knots and it's a bit scary :)

    At the moment I'm thinking a shallow V for the first foot or two at each end widening into a round bottom and finally a flat bottom for about the middle half of the proa would be a fairly decent middle ground of wave piercing, smooth sailing, and minimal wetted surface, if I do build my dream proa it'll be in strip plank or more likely cold molded so it'd be doable.

    I suspect Russell would have to beef up his foils considerably if he had a flat bottom.

    I think the steering oars would work fine, better than fine with the tiller pilot and if you carry a yuloh it could always stand in if you did lose a steering oar.

    hmm, time for some serious thinking, I'd better go out to the shop so I don't set off the smoke detector :)


    Bill

  • 17 Jul 2018 13:52
    Reply # 6385035 on 6368944

    I did not realise there were quite a few other Proa-junkies lurking around here.  My ideal would be a Russell Brown type proa, junk rigged.  Yes a big compromise on accommodation but the most sailing smiles for your ££s.

    Russell can sail under main only, by balancing the rudder-boards - so any type junk rig will do, though largely balanced Aero-junk is the preference.  No jibs, though a ghoster to play with ok.  Un-stayed mast, though light stay to the ama is possible.

    Rudders, Russel (Newick) are well proven, though in shallow water a steering oar could be brought into use.

    Manoeuvring in tight spaces - what other boat can sail up to a quay, casually pick up from the bow, then shunt and sail out 'in reverse'?

    Interestingly one of his - Pacific Bee (ex Cimba) was for sale in Belgium recently, unfortunately a few to many Euros for me.  I am seriously tempted to build one, especially after watching the video Jzerro at 17knts - completely smooth and relaxed.  That said I am not sure If I would wish to commit a year or two to such a project, missing out on sailing, and ending up with a boat of no value to anyone else.  So will I?  Probably not, though if funds and somewhere to build come my way, perhaps.   I did have a 16' proa which i rigged with a windsurfer sail (curtsey of Robert Beigler) which was great fun.  If I get a sensible cruising catamaran sorted, a day / weekend size proa, similar, maybe a bit smaller to the original 30' Jzero would be a fun, doable project.

     

  • 17 Jul 2018 12:24
    Reply # 6384878 on 6368944

    I might be missing something too, since I am a proa novice, but I have a fair bit of junk rig experience and a clear idea of what is needed there.  On Russell's proas, of course, his mainsail is on a track behind the mast, whereas a junk sail is alongside the mast.  As I understand it, and according to the sketch I am looking at now, assuming the mast is fixed  and not rotating, a Pacific proa's junk sail will be on one side of the mast on one "tack" (for want of a better word) and on the other side of the mast after you have shunted and alternated bow and stern.  So you don't have PJR's "chimney" available. 

    If the mast did rotate through 130 degrees, then the chimney would be available, and the masthead positions for halyard, topping lifts and mast lift could be in the usual places.  But their tails could not be attached to the deck, as those positions will change when you rotate the rig.  Because the mast is right next to you in the cockpit, however, they could be cleated to a pinrail that clamps to the mast below the boom.  Then their tails will rotate with the mast. 

    But the pivot of a rotating mast is at the leading edge, and the forestays and shrouds terminate there too, to keep them all on the same axis when the mast rotates.  The mast swings behind this pivot point like a rudder on its gudgeons.  That would also apply to a round junk mast section.  The mast could not have any bury, therefore, but would have to be decked stepped like any other rotating rig.   You could not use the RB stayed rig with a round section that rotated around its own centre, as the rigging attachments on the mast would shift too much. 

    But it can be done.  It would be better if the leading edge of the mast was straight, to make sure the axis remained aligned all the way to the masthead.  The sides and back could taper.  If you used a standard taper alloy section like a flagpole, you can rake the mast forward slightly to keep the leading edge aligned with the pivot point.

    None of these issues will be of consequence if you use an unstayed rotating mast, as you are considering.  The challenge then is to get enough sail area forward of the mast, combined with daggerboard variability, to balance the rig.  But I'd love to have that jib, for light airs in particular

    I think steering oars can be made robust enough for ocean sailing.  They would pivot on custom-made, captive oarlocks, and use rope downhauls forward and aft of the oarlock to hold them in the correct position, either for steering or to lift them.  I envisage the rope being attached to the oar several feet aft of the oarlock, then going down through a turning block at the cockpit floor, through a rope clutch, then through another turning block and up to the inboard end of the oar.  To either raise or lower the oar, you just open the rope clutch, move the oar to the desired position, then engage the clutch again.  Modern ropes and clutches are massively strong.   I can see no reason why a simple tiller pilot would not work with this system.  You also need a way to stop the oar from rotating (ie keep the oar blade vertical when in use).  The Polynesians used a vertical stick at the inboard end.  I'm still thinking about this. 

    With RB style rudders, you could carry a spare, or use the other one alternately, as you say, but you might also damage the daggerboard case.  However, it is no riskier that sailing with spade rudders, as so many boats do.  I've seen people haul up the daggerboards on their cats with lines led aft, so that might work.  And you could carry an oar as the ultimate backup.

    12:1 length to beam ratio sounds about right to me for a cruising proa, too.  Russell firmly believes his rounded V-sectioned hulls are best for ocean sailing (we had a long discussion about that) but I remain interested in a narrow flat bottom.  Lots of cats and tris have this sort of section and are fast and comfortable.

    My money is still on the fixed, round mast.  When I get the time later this year I might build a model to see how it works.  But I will follow your ideas with interest.

    I know what you mean about discussing this rig outside of the JRA fora.  I took a retired professional sailmaker friend for a sail yesterday and he was horrified by my flat sail.  Discussing methods of putting camber into a junk sail only added to his dismay.  All wrong, he said, as we sailed blithely along...

  • 17 Jul 2018 05:55
    Reply # 6384607 on 6368944

    I hate that, I wake up in the middle of the night and it's a long and busy day tomorrow and I'm building a boat in my head instead of going back to sleep :(

    I wonder if there's a list of special jargon for proas somewhere, it can make things confusing to discuss.

    I tend to think of the ends as port and starboard, when the end of the proa on the skippers left is forward the wind is coming in over what would be the port rail in a tacking rig, so port tack, port shunt, port bow, same for the starboard bow, not that it really matters among shunters, but we need to keep in mind that tackers aren't going to know what's going on :).

    I never thought of the topping lifts either, in fact I decided early on that since a shunting rig has a shorter range of roatation, about 160 degrees (Close hauled to close hauled both on the leeward side) rather than 180 degrees like a tacking rig (port beam reach to starboard beam reach) that there was no reason to rotate the mast, hmm.

    I must be missing something, in the picture I've got in my head the "Chimney" that Blondie Hasler talks about in the PJR on the side of the mast opposite the sail should still be viable on a shunter, about the only problem I can see would be when you need to take the sail bundle off the mast.

    I'm not sure how Russell works his rudders, but I've seen daggerboards with a block above them with a line down to the handle, give a tug on the line and the board comes up, a second line tied off at the deck on one side of the board runs up and through a deadeye at the top of the board and down to a block on the deck on the opposite side of the daggerboard, give a tug on the line and the board goes down, lines could be run to the cockpit, should work well on the rudders Russell uses.

    Russell has said he's never had any damage to rudders an any of his proas, I suppose if  one did get wrecked you could move the other back and forth till you made repairs if they're not single sided like a leeboard, but they are bloody expensive, the ones for Wet N' Wild were $1400 usd each if I recall, and tough to DIY. I don't think I want to try them either, there's a 50 acre log boom about 100' from where I put my boat in the water, the main reason my leeboard'll kickup :)

    I kind of wondered about the asymmetrical hulls, I've read why they started using them but it seems like there are easier ways, I suppose there weren't at the time someone came up with the idea.

    I'm still not sure what I'll need for a rudder, if the sliding leeboard works well then I can probably get by fine with a steering oar, but if I ever want to use an autopilot I guess I'll need real rudders, and probably something fairly robust, and probably two auto steerers...

    I'd like to have a yuloh. just makes sense since the proa already has the raised deck you need to use one well, be nice for quietly leaving a marina early in the morning.

    I've been playing around with what to use for a rudder, oddly enough much what you're thinking, a pair of "kick-up rudders on sticks"  but deployed off the trampoline between the hulls and operable either from the "Bench" or a hatch like Blondie Hasler used on his boats to handle the rig from inside the boat.

    I actually don't post anywhere else, this seems to be the only place I can ask questions about a rig I'm interested in without someone telling me I'm an idiot and to just go out and buy the most expensive bermudan rig I can afford...

    I'll probably go a bit wider too, I think most of Russels proas have a length to beam ratio of around 20/1  I'm thinking maybe 12/1, so if I build the 29 1/2 footer I'd like to it'd have a 28' waterline, and a 28" beam.


    Bill

    Last modified: 17 Jul 2018 06:02 | Anonymous member
  • 17 Jul 2018 05:32
    Reply # 6384602 on 6368944

    Hi Bill,

    Thinking more about the halyard with a fixed mast, and doing some rough sketches, I believe you can get away with the fixed halyard point directly above the yard (and the halyard tail coming down outside the sail) when the sail is feathering to leeward, as long as there is at least 1m of drift between the halyard blocks, and provided you move the halyard sheeting point on the deck each time you shunt.  Assuming the sail is rigged with the mast to the right of the luff when feathered, you would move the deck cleating position towards the ama when the sail was going to be to windward of the mast, and towards the leeward pod when the sail is to leeward of the mast.  I'd just have two cleats and move the halyard from one to the other.  There is little load on the halyard, even on my 35sq m junk sail (it just hangs there!), and shifting it will take a second while you are shunting.

    The sequence would be (on my proa) - 1: roll up the jib;  2: dump the mainsheet and come beam on, letting the mainsail feather;  3: lift up and secure the steering oar; 4: lower and secure the opposite steering oar;  5: shift the main halyard to its new cleat;  6:  sheet in the mainsail again with the other mainsheet; 7: roll out the other jib at your leisure once the boat is underway.  It might sound like a lot of things to do, but only the jib will take more that a few seconds of effortless work.  And you will never, ever miss stays!

    I find it amusing writing about proas because I cannot talk about port and starboard in any permanent sense.  This fluidity is what flummoxed my thinking initially about how to rig the sail.  It all becomes simple when you consider that the sail feathering to leeward is its natural, "at rest" position, rather like the fore and aft position is the" at rest" position for boats that only go in one direction.

  • 17 Jul 2018 00:40
    Reply # 6384318 on 6368944

    Hi Bill

    I woke up in the middle of the night and thought, what about the mast lift and topping lifts, if the sail is rotating around a fixed mast?  At first I thought it was an intractable problem, until I realised I needed a paradigm shift in my thinking, a Pacific proa shift if you like.  I was thinking of them being attached to the sides of the masthead, as in a boat with one bow, but in fact the defacto position for the proa sail, the "at rest" position, is with the boat beam on to the wind, ama to windward and sail feathering to leeward.  So the mast lift and topping lifts would be attached to the masthead at the fore and aft centreline (of the mast, given it is offset to windward of the cockpit).  The tail of the main halyard also requires lateral thinking.  It will come down to the deck on the outside of the sail (the mast being on the other side), not on the opposite side of the mast as with a one-bow boat.  With at least 1m of drift between halyard blocks I think the halyard would have enough room to move.  I'd want to make a model, possibly a proa dinghy utilizing a canoe, like Russell's first proa (he used a South American dugout) before committing to a big boat.  The other option, still setting up the rigging as above, would be to make the mast rotate through about 35 degrees either side of the "at rest" feathering position, as Russell does, but if I could avoid that expensive complication, and i think you can, I would.   But yes, it will work.  I think my big project days are behind me, though if I could find an affordable place to build, I might consider a 9m "fattie" version of Madness.  I wouldn't dream of crossing an ocean in it, not being tough or brave enough, but fully intend to spend my last days afloat mooching in sheltered waters.

    Rudders are the other thing that interests me.   Russell's lifting rudders in cases work well, but I am not sure if anybody has developed a system for raising and lowering them from the cockpit.  And they are vulnerable to damage. The Polynesians use a long oar.  The rudders don't need to be inside the main hull.  I have in mind something that looks like a yuloh in profile (angled, not straight) but with a steering blade on the end, mounted on the beams, with the steering arm coming back into the cockpit.  When you shunt, you push the inboard end down to the cockpit floor, lifting the blade out of the water, secure it, deploy the other one, and away you go.  I'd have a rope attached several feet aft of the fulcrum that went through a turning block in the cockpit floor to a cleat, to hold the blade down when in use.  To raise the steering oar, just uncleat this line, push the inboard end down and tie it off on the same cleat.   And you always have a spare.  Being the super cautious guy I am, I'd probably have another one lashed on deck!

    So, with a Russel Brown stayed rig, junk main, roller furling jibs, and Polynesian oar rudders, I'd have a Pacific proa that could be handled entirely from the cockpit.  It would have about 30% more displacement than a Russell Brown proa, but still sail very well.

    All of Russell's later designs had symmetrical hulls and amas and that is certainly the path I would take.  He came to the conclusion that there was no advantage to asymmetrical sections.

    I am not involved with any proa groups, but if you want to share my communications to others who are, please do.

  • 16 Jul 2018 16:56
    Reply # 6383301 on 6368944

    I think it would work Graham, really well actually, what you describe is pretty much what I have in mind if i can't make a single unstayed junk rig work, I'd really like to keep it simple if I can, and I'd like to have the option of tacking just in case.

    I can just picture it with a big Reddish rig and a huge jib, you could put a stupid amount of canvas on her and still keep it pretty low.

    If I went the stayed route I think I'd want a mast prop any time I wasn't actually holding on to the sheet in case she got backwinded.

    so are you thinking asymmetrical hull? I notice Russell Brown has got away from that on his last couple of proas and Madness is symmetrical too, seems to me that a symmetrical hull would be roomier.

    I like the Russell Brown style of proa, even more after I read about him hitting something at night and tearing off his ama in Jezero, she floated well enough on the lee pod that he was able to tow her in for repairs, not sure you could do that with a HP. I'm not sure if that was happy coincidence or careful planning, good design though.

    I read an article by Jim Brown about them trying to trying to capsize Cimba over the lee pod, they ran a rope from the mast head and hooked it up to a station wagon and still weren't able to get her to come over.

    Mr. Brown might have kittens, but before they got their eyes open he'd be wanting to know how it works, not long after that he'd be making plans, the simplicity of the Junk rig would appeal to him I think

    @ David:

    I'm planning on trying the split junk unstayed with a sliding leeboard out on the ama to change the balance, as I see it a split junk with a medium to high aspect ratio shouldn't shift the  balance by more than 25% of the WL, and lead should eat up about 12%-20% of the change, an aero rig might be even better.

    On a pacific proa you need to put leeboards on the ama if you put a leeboard on the main hull when you turn the ama to the wind to shunt the proa tries to rotate around the leeboard and balance with the ama on the lee. you could use weatherboards on the main hull I suppose.

    you could also use a Hasler/Mcloud on a revolving raked mast, the rake in the mast would bring the CE closer to the mast on all points of sail, mast would have to be curved above the partners, not sure how one would go about that though.

    The leeboard I'm working on slides 8 feet and since it's a kickup could be rotated another foot or so either way, so 10 feet on a 15' waterline. It saves a bit of weight over 2 daggerboards and daggerboard trunks and I should be able to balance my boat on any point of sail so rudder loads should be minimal, with a bit of luck hands free sailing should be doable.

    But just in case I've built in anchor points on my main hull for stays if I need to hang jibs off of them, they also double as tack points for a crabclaw if i ever try that :)

    We have the tools, the technology, and and the will, we'll get it working :) Fun times.

    Just a thought, but a dipping lug would be soooo easy to use on a proa, I'm planning on keeping one aboard for a spare sail, all you need is a the sail and a yard, and if push comes to shove you can use a couple oars lashed together for a yard so it's a very lightweight backup sail.

    Bill

    Last modified: 16 Jul 2018 17:24 | Anonymous member
  • 16 Jul 2018 12:17
    Reply # 6382884 on 6368944

    I wonder if a single split junk or aero junk sail, rotating on a centrally located mast, would work if a leeboard was added at each end of the main hull? I would rather have the leeboard than the jib myself.

    This uses the principle of changing the CLR of the underwater profile, rather than the C of A of the sail plan.  It could even be accomplished by using a pivoting skeg in a slot in the bow, with an attached rudder, one at each end of the boat, then it is no more complex than the standard shunting proa.

    Last modified: 16 Jul 2018 12:24 | Anonymous member
  • 16 Jul 2018 11:05
    Reply # 6382795 on 6382627
    Anonymous wrote:

    as I recall, and it's been a while, Russell Brown uses  a roller reefing jib at each bow to bring the balance forward when close hauled or reaching.

    Since a junk rig could be fully stayed on a pacific proa you could do the same thing, wouldn't even need much of a jib if you used a split junk, or you could use a reddish rig and a huge jib.

    You'd have to use double sheets but that shouldn't be a big deal in a proa, remember, they're not going over your head, or even over the boat, any time a sheet wasn't being used it would be out over the water on the lee side of the boat.


    Bill


    Well done, Bill!  You are quite right on all points.  A stayed Russell Brown rig on a Pacific proa that replaces the mainsail with a junk sail is a brilliant idea.  I think this is the breakthrough idea I was hoping for.  The mast can be stepped to windward of the main hull, like it is on Russell's boats, so that the stay out to the ama and the forestays (both widely angled) triangulate the mast support.  There is minimal support for the mast if the rig gets caught aback, a weakness Russell acknowledges, though the chances of this happening are slight, if the proa is properly sailed. Russell uses rotating masts and very light sections.  However, if the junk main's mast is stepped on the floor of the cockpit, with 10% bury, and similar scantlings to an unstayed mast, it could stand unsupported if taken aback. 

    And the mast might not need to rotate.  The masthead halyard sling point presents something of a challenge, but if there is enough drift in the halyard blocks, and possibly a sliding bale or traveller at the masthead, so the masthead blocks can self-align, I think there might be enough movement  The sling point, from the sketches I have just made, would appear to be above the yard when the sail is feathering to leeward.  Because the mainsail stays to leeward all the time, the front of the yard will not interfere with the forestays, either. 

    It would be a heavier rig, and perhaps  a carbon fibre yard, boom and battens would be beneficial.  Also I would definitely want a cambered junk sail.  This boat will be too fast for a flat junk sail. 

    Russell uses hanked-on jibs, utilizing downhauls, but others have built his boats with roller furlers and I would choose to do this.  And as Bill points out, the double sheets on the junk sail would sweep across the ocean, not over the boat.  I'd entirely missed that point.  I suspect Russell would have kittens if you put this rig on one of his boats, but I am now convinced it will work.  A Russell Brown type of Pacific proa (but maybe a cruisier version) and a junk rig.  Perfect!  I'd prefer a maximum of about 12m or 40ft LOA for this concept, though one could go to 15m (mine would be 9m).  The junk sail on a 15m proa would be large, but you never have to gybe, just come around beam on, dump the sheet and let the sail feather to leeward while you swap rudders and jibs, or reef. Sweet.

    I am a disciple of the Pacific proa (ama to windward) because of the light loadings on the beams.  I'd rather build a cat than an Atlantic proa (with the ama to leeward), since the beam loadings are similar.

    It would still be a minimalist sort of voyaging yacht, but no more so than Pete Hill's Oryx perhaps (less room though).  You have to keep multihulls light and simple if you want them to perform.  A lot of the roomy production cats built for the charter trade (no names no pack drill) sail like a block of flats.

    PS: before anyone starts throwing bricks, I admit Arion sails like a block of flats too!  24ft, with 10ft beam and weighing 5 tons...what do you expect?  I'll be dreaming of a junk rigged proa tonight.  Thanks, Bill!

    Last modified: 16 Jul 2018 11:54 | Anonymous member
  • 16 Jul 2018 05:46
    Reply # 6382627 on 6368944

    as I recall, and it's been a while, Russell Brown uses  a roller reefing jib at each bow to bring the balance forward when close hauled or reaching.

    Since a junk rig could be fully stayed on a pacific proa you could do the same thing, wouldn't even need much of a jib if you used a split junk, or you could use a reddish rig and a huge jib.

    You'd have to use double sheets but that shouldn't be a big deal in a proa, remember, they're not going over your head, or even over the boat, any time a sheet wasn't being used it would be out over the water on the lee side of the boat.


    Bill

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