Proa Shunting in Heavy Weather

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

Tags:
  1. NewSalt
    Joined: Apr 2021
    Posts: 24
    Likes: 2, Points: 3
    Location: Canada

    NewSalt Junior Member

    Thanks...
    Some extra considerations when choosing from rig options.
    I'm thinking that this might be minimized with a schooner because you could start with the downwind sail, which would tend to want to keep that end of the hull in the same orientation, but it would mean that there was a bit more skill experience needed to complete well.
    The gibbons might have the edge here as the drag shifts to to correct end, and then forward thrust isn't applied until you're ready to get underway, but I needed to give this some more thought...
     
  2. Clarkey
    Joined: Aug 2010
    Posts: 139
    Likes: 22, Points: 18, Legacy Rep: 10
    Location: UK

    Clarkey Senior Member

    I agree that doing this with a bermudan schooner seems straightforward but am struggling to imagine pulling it off with a Gibbons rig?
     
  3. NewSalt
    Joined: Apr 2021
    Posts: 24
    Likes: 2, Points: 3
    Location: Canada

    NewSalt Junior Member

    I'm not sure it could, still thinking...

    but when I say Gibbon's rig I mean the original - I think of the Dierking rig as a different beast. No boom, just a yard. The sail flies loose like a Genoa, but does add drag. First step is to loose the sheet then cant the mast aft and pull the old peak down to the new tack. In this position, I imagine the weathercock forces would keep the proa in the desired orientation (broad reach/run), and as the sail starts to fill, the CE remains (new) forward until you have way on and are ready to head up.

    Might be wrong though...
     
    Last edited: May 6, 2021
  4. Clarkey
    Joined: Aug 2010
    Posts: 139
    Likes: 22, Points: 18, Legacy Rep: 10
    Location: UK

    Clarkey Senior Member

    I thought the original Euel Gibbons rig had a fixed mast that didn't cant? I just imagine that long, high up, yard attached to flogging canvas being a bit of a nightmare to control in that situation?
     
  5. rob denney
    Joined: Feb 2005
    Posts: 781
    Likes: 138, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    I sailed a crab claw rigged proa in the Marshall Islands last year. If you did not go beam on to the wind, the boat will luff and the rig fall down. You luff, release the sheet, grab the sail and move it towards amidships, waiting for the boat to turn beam on, then complete the shunt. Done properly, shunting these boats is ballet. Grab the spar, take 2 steps, turn, grab the mast, take 2 more steps and plonk it in the hole. I never got close. ;-) There is a video, including a shunt and some explanations at Feb 2020 on Mini Cargo Ferry Prototype – HARRYPROA http://harryproa.com/?p=3155
    No, as it is ridiculous. A proa beam to is no less safe than any other multi beam to regardless of whether they are sailing, hove to or shunting.
    Nothing. Done properly, in big wind and waves shunting off a lee shore is invariably less costly than tacking a cat (backwinding headsails, sailing backwards in irons). Modern shunting is shown in the video at SHUNTING – HARRYPROA http://harryproa.com/?p=1910. It is even quicker with aschooner rig. See racing shunt if you prefer the pictogram.

    Suggestion: When you ask proa questions, ask respondents to include their experience, then weight the answers accordingly. Or, join HarryProa groups.io Group https://groups.io/g/HarryProa which is by far the most experienced group of proa sailors, discussing deeper issues than anywhere else.

    Absolutely agree about lee pods. Weight in the wrong place, a big hole in the most loaded part of the hull and an invitation to trip sideways when heeled.
     
    guzzis3 and fallguy like this.
  6. NewSalt
    Joined: Apr 2021
    Posts: 24
    Likes: 2, Points: 3
    Location: Canada

    NewSalt Junior Member

    Hi Rob,
    Thanks for your comments.
    I will look into the HarryProa group, but I am wondering: are people interested in other sorts of proas welcome?
    If I were looking to create a large proa, I'd likely end up with a Harry if not Catamaran, but every time I end up running through the design spiral trying to create a minimal cruising proa with updated materials/design/rigs, I end up with something akin to an Atlantic.
    Thnx
     
  7. rob denney
    Joined: Feb 2005
    Posts: 781
    Likes: 138, Points: 43, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    Everybody who likes talking about building or sailing boats is welcome. Look forward to hearing why the Atlantic ticks your boxes. I can understand for racing, but for minimal cruising, the Harry arrangement is hard to beat.
     
  8. Dejay
    Joined: Mar 2018
    Posts: 720
    Likes: 136, Points: 43
    Location: Europe

    Dejay Senior Newbie

    I'd be curious what you're trying to design. I'm now also thinking about a proa.
    Are you trying to minimize boat size and maximize accommodation so want to put them into the bigger hull? For berthing fees?

    A long slender symmetrical hull without accommodations is cheap and easy to build. More length, less resistance, smaller sails. Less forces, less structure, less weight, less material, less cost etc. And by separating the functions you have more modularity and easier of build.

    If you check out his 80' cargo ferry prototype you could even build the lee hull in half height and solid fiberglass to save even more cost and build time.

    Do you consider the Ex40 as minimal? You could have a wider, taller or larger cabin at the cost of some performance and put a smaller dinghy somewhere else. It really depends what you're trying to minimize. Or are you looking for shorter than 40'?
     
  9. NewSalt
    Joined: Apr 2021
    Posts: 24
    Likes: 2, Points: 3
    Location: Canada

    NewSalt Junior Member

    Yes, I like the Ex40 for some types of minimal.
    I'm looking for something different though.

    I wanted something that doesn't need to be as performance oriented, but that I don't have to worry about running into things with as I like sailing in shallow water. Beachable without fuss (more drying out than landing craft though). Proas are meant to be long, but ideally one that is narrower than we've been seeing would allow it to access a berth for a larger mono or the end of fingers - not cheap, but not as bad as double berths and easier to find. Rather than try to fit it all in, I'd rather only a very few stations, but for each of them to be fully human sized and comfortable. I'm not looking for a second hull so much as a larger ama/float.

    Cheers and other very early Atlantic's were closer to what I am drawn to in many regards.

    I'm not set on many factors, and every time I change my mind on one thing, it has a cascade effect on the others. But what I'm most likely to settle on looks something like (WARNING: this is likely to be long and at times confusing ;p):

    Imagine a traditional walap with a narrow, deep hull and considerable rocker. Now convert it to an Atlantic using a pretty minimal ama, but still greater than displacement (I haven't seen this done). Akas are all designed to take full displacement nowadays even on Pacifics due to wave stresses, and lengthening the ama to the full length of the vaka or slightly more adds some cost, but in the grand scheme of things, it is minimal. Domestic water and fuel tankage would be in the ama. The deep central portion of the main hull/vaka would protect relatively LAR spade dagger rudders; the Atlantics' lining up forces better and offsetting each other will make this simpler, but a rig with controllable CE would still have considerable merit in this configuration.

    There would be no leepods per se so as to maximize hull separation and righting moment, but the interior would be like a trench in the hull with counter space either side to prevent claustrophobia; the windward counterspace enclosure ideally would carry the displacent in an aback knockdown to keep all of the weight on the righting side. A platform between the hulls would house a sleeping compartment and the cockpit. This latter would look just like half of a monohull's but take advantage of the proa's always keeping the wind to one side to keep the crew comfortable under a dodger - this is the heart of the boat.

    There are drawbacks to this approach:

    As mentioned - performance will be limited when compared to foil based designs.

    Still working on the Atlantics' reorienting themselves backwards to the wind when idle, but there may be some options depending on rig and why I say Atlantic(ish) is b/c I'd like the mast(s) on the platform, not in the hull which would help with this (but has it's own drawbacks such as not contributing to stopping an aback knockdown resulting in turning turtle)

    Smaller space than a Harry style

    No capsize prevention systems. This would primarily be avoided by smaller rig/performance potential, a low CE, and having a rig that has little power when aback.
     
    Dejay likes this.
  10. Dejay
    Joined: Mar 2018
    Posts: 720
    Likes: 136, Points: 43
    Location: Europe

    Dejay Senior Newbie

    What dimensions approximately would still fit this "larger monohull berthing space"? Something like 40' x 10'? Larger? Smaller?

    I have minimal boating and sailing experience so I can't speak to the sailing advantages of Atlantic vs Pacific proa.
    The biggest advantage I believe is separating the sail, mast and rig from the accommodation. Less constraints makes it easier to design and build.

    The harry proa hulls themselves seem to be so easy to build with the mould and vacuum infusion that there is no advantage of making the ama minimal - so why not use it for accommodations?

    Wondering why the Harryproa Air 40 wasn't developed further or made into plans. I assume you've seen that one?
    It proably just doesn't play to the harry proa advantage of cheap length.
    But I could also imagine a simpler version with telescoping crossbeams and demountable. And a 9m x 2.5m windward hull so it fits on a trailer while the lee hull slides below the deck. And I guess the lee hull with folding ends. Then you could push the two hulls together for a smaller berthing space, or demount and trailer for cheap storage.
     
  11. Clarkey
    Joined: Aug 2010
    Posts: 139
    Likes: 22, Points: 18, Legacy Rep: 10
    Location: UK

    Clarkey Senior Member

  12. NewSalt
    Joined: Apr 2021
    Posts: 24
    Likes: 2, Points: 3
    Location: Canada

    NewSalt Junior Member

    At 36-40'x10' is too narrow, both in stability and hull interference (although an asymmetric vaka and minimal ama would reduce this effect some). 15' would be approaching 40% so probably be about right, and squeeze into the 40 berths around here. This narrow dictates having weight to windward.

    Turn one of Pizzey's (below) around and you are closer to the configuration I'm looking for.

    One of the big overlooked positives for cruising that Atlantics' have is more protection from the weather, which can be seen by the shared Pizzey image.

    I like Kergomard's 35' styling (shared below) but it too exposes the crew. I also want the lateral resistance in the windward hull, plus the aforementioned smaller ama and foiless design.

    Both A and P proas have the rig in the main hull usually. Denney's designs are somewhere in the middle conceptually where the functions of each hull are differentiated, the lee hull acts like the P's vaka in terms of rig and lift, the windward hull like the A's in terms of righting moment and accomodations (and gets the wind protection right). There is a lot of merit to this, but there are always compromises. It means two more equally sized hulls than is possible (although in practice the big racing A's hulls were often similar), which I am avoiding as I would prefer most of the build effort to be applied to the main hull. It also generally means the CE being outside the boat laterally which can be compensated for statically, but I prefer to avoid because of the dynamics that sets up. And again, I feel that it is safer to keep the lateral resistance upwind (if you can indeed keep the boat from wanting to reorient itself)
     

    Attached Files:

  13. garydierking
    Joined: Sep 2004
    Posts: 169
    Likes: 39, Points: 28, Legacy Rep: 174
    Location: New Zealand

    garydierking Senior Member

  14. Russell Brown
    Joined: Jul 2012
    Posts: 136
    Likes: 40, Points: 28, Legacy Rep: 25
    Location: washington state

    Russell Brown Senior Member

    I saw on your blog that you built a power cat with Tornado Hulls. Your to speed is good. I only got about 16 with 15 hp. It looks good and I'd love to know how it goes when you get the bugs worked out. I have a new "Grasshopper" that's only been out once. The only things that work well on it so far are the trailer and the motor mount. I made a sled for the motor to adjust the height and attached a serious fairing for the leg of the motor. There's not much fuss around the motor.
    Did you hook up a tachometer on your cat? Seems like the only way to choose a prop.
     

    Attached Files:


  15. garydierking
    Joined: Sep 2004
    Posts: 169
    Likes: 39, Points: 28, Legacy Rep: 174
    Location: New Zealand

    garydierking Senior Member

    It turned out that the very old plywood hulls I got were not going to hold up so I cut them up. I like your fairing. I had one too but yours looks better. I didn't have a tach, I just used the standard prop on the Honda 9.9. It was a heavy engine though and I had to mount it well forward.
    [​IMG]
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.