Proa Shunting in Heavy Weather

[NewSalt]

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.......

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...

 

[Clarkey]

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...

I agree that doing this with a bermudan schooner seems straightforward but am struggling to imagine pulling it off with a Gibbons rig?

 

[NewSalt]

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...

 

[Clarkey]

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?

 

[rob denney]

I have a technical question which would likely apply to all styles of proa:

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

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?

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.

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?

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.

 

[NewSalt]

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

 

[rob denney]

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

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.

 

[Dejay]

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.

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'?

 

[NewSalt]

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]

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.

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.

 

[Clarkey]

Have you looked at some of the stuff done by the late John Pizzey? They are unusual designs that may provide some food for thought, especially on the narrow beam ideas.

Proa File | The Proas of John Pizzey - Part 1 https://proafile.com/multihull-boats/article/the-proas-of-john-pizzey-part-1
Proa File | The Proas of John Pizzey - Part 2 https://proafile.com/multihull-boats/article/the-proas-of-john-pizzey-part-2
Proa File | The Proas of John Pizzey - Part 3 https://proafile.com/multihull-boats/article/the-proas-of-john-pizzey-part-3

 

[NewSalt]

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)

 

[garydierking]

I'm sure there was plenty of rough water and high seas in this account.
Russ Brown's Pacific Crossing https://outriggersailingcanoes.blogspot.com/2021/05/russ-browns-pacific-crossing.html

 

[Russell Brown]

I'm sure there was plenty of rough water and high seas in this account.
Russ Brown's Pacific Crossing https://outriggersailingcanoes.blogspot.com/2021/05/russ-browns-pacific-crossing.html

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.

 

[garydierking]

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.