Tacking "proa" - what's the penalty?

I am actually working on a very small tacking / shunting Proa. 10' main hull, 8' beam, 30 lb main hull + cross beams + other structural members, 15 lb rig, light (but ??? lb) ama. If I can get it to work OK in displacement mode, foiling and/or hard wing would be the path to more performance.

For max speed (the objective) I will have the main hull, the rig, and the combination dagger board/rudders all to the windward. This is the "half a tri" concept.

However, if I need to work my way upwind without shunting, I should be able to tack.

I am intentionally not going to put any finishing touches on the initial craft and I am trying to maintain maximum flexibility for the configuration adjustments I expect to need.

The first round will be with a free standing rig that can take the heavy loads expected in the normal mode, and can take the lesser loads in the "ama to windward" mode.

Making it all work is just engineering. I plan to use mostly trial and error to figure stuff out rather that try to crunch numbers since I really need to get more "on the water time" anyhow.

 

If the rig is offset from the main hull like traditional proas it is working a bit like a cat when it tacks. For short tacks I'm not sure a proa needs to have the same righting moment on each heading. Get clear, then configure your power set up, be it Atlantic or Pacific. For cruising an outrigger seems less versatile. You can't sail into a tight area then reverse without having to turn around etc....

 

The "Ninja" is an example of a tacking outrigger that seems to work very well. it takes full advantage of fore and aft hull asymmetry and movable ballast ( the crew). Interestingly it is also sold as a tri( "Ninja Spider").The rack is removed and replaced with beams and an ama. I watched a video of the tri sailing and noted that the leeward hull submerged to the beams . The boat does not pitch pole but the spray coming from the forward beam would seem to indicate a lot of drag. It suggests to me that the low volume ama does not allow the main hull to fly. Watching the boat sail as an outrigger it is evident that with the main hull to lee the ama can be induced to fly effortlessly . If this is indeed the " good tack" then in order to fly the main hull on the other tack the volume of the ama and there fore the weight of both the ama and the beams would need to increase. Ultimately if we go this route do we not end up with a cat? The other approach might be to add a lifting foil to the low volume ama.

 

http://www.eckerberg.net/boatbuilding/proa/proa.html

this is an interesting 1/2 tri project from a chris white dragonfly design

 

The Slatts 22 was a outrigger that used a foil in the ama for stability assistance allowing the crew to stay in the kayak style cockpit. This approach seems to retain more of the theoretical outrigger advantages. Without the foil or crew weight though a catamaran or proa does seem to make more sense. A foil in the ama of a shunt/tack proa would offer the same advantages, allowing power to be kept up on the short boards.

 

From my own minimal experience on my tacking wa'apa, and from written accounts of other tacking outriggers, you lose between 1-2 knots boat speed (less in low winds, more in high winds) on the ama to lee tack. However you feel soooo much more confident on that tack, you can work on the rig, move about the boat, etc without any fear of the boat capsizing (I had a few close calls myself). This would be less of an issue on a larger cruising type outrigger however.

The pacific proa was the fastest polynesian sailboat because the mechanics of a proa combined with plenty of crew and the crab claw shunting sail allowed them to fly an incredible amount of sail area given the very weak materials available to them. Its application to today's recreational boats is, imho, limited. Although theoretically a pacific proa can be built lighter than a tacker, it still must be built fairly strong. Remember Jerry Brown's jzero which broke an aka in a storm? It was strong enough to take the loads from the sails, but there is still a minimum strength and buoyancy in the ama that you need for cross-seas, breaking seas and occassionally being taken aback (getting the ama to lee). The disadvantages of the proa, especially for a low cost cruising boat, are significant. Firstly the sail configuration must be sorted out. It is complicated, even more so because the mast must be supported in case you get taken aback. The most successful arrangement, that used by jerry brown, requires a rotating mast and two jibs. I imagine two travelers are needed as well, but I'm not sure. So you have added cost there. Then, the rudder/daggerboard arrangement that seems to work on proas is also complicated and probably a bit delicate for the casual cruiser, and would be difficult to implement on larger proas. Not impossible, but I'm saying, the claims of proas being less expensive, lighter and simpler than other boats are a little exagerated. Finally, since proas are double ended, you can't sit in a proper cockpit in the back of the boat, protected from spray, you must sit up high by the akas, in the center of the boat.

I have considered the same build as the op. Basically a tacking outrigger which has the vaka l/b ratio of a cruising trimaran, about 25' long. The accomodation would be expanded towards the ama above the waterline, like a trimaran but only on one side however to keep it narrow on the trailer and also to keep the cg somewhat closer to the ama than to the center of the vaka. A simple safety ama would be necessary for the ama to windward tack, I could have really used one on my tacker, more than anything for peace of mind. Finally some sort of minimal water ballast system in the ama would be really cool, something that could be pumped out each tack, or even just left in the ama for both tacks. An old tornado rig or similar would suffice for sail area, and a small aft cockpit would be set up, like a trimaran has. It would be the cheapest way to cruise fast on a trailerable boat, though cabin/cuddy space would be pretty minimal, much less than a catalina 22 for sure...

 

@peterchech
Thank you very much for your input! These are exactly my thoughts behind this thread!
Nice to hear of some practical experience with a tacking outrigger.
It is somewhat reassuring for an armchair sailor like me, that with my thoughts and expectations I am not so far off the track.
Especially thinking of a cruising configuration in the 20-30 feet range, the volume of the ama would be selected in a way to make it usable as at least storage space, so the wetted area (as the reason for the speed penalty) wouldn't increase so much as on a nearly submerged low volume ama of proa type.

 

Hi champ, glad to hear someone is on the same wavelength as me. As far as I know, the only cruising tacking outrigger with accommodations in this size range being built is still in construction in brazil, by a home builder out of plywood. It doesn't seem to have much interior volume despite its 30' length however, and seems built for speed more than true cruising (aren't all small multis?) I can't wait to see the finished product...

As for AMA design, it is pretty well settled that an ama with minimum displacement of 100% of total displacement is best, plenty of threads here on that...

Do u have any solid build plans, or are u still armchair at the moment?

 

@peterchech
Only armchair sailing and building, I have to admit.
I'm just daydreaming about the possibilities for one of the holy grails in boatdesign:
Affordable (trailerable), basic comforts for 2-4 people (double or king size bed, standing height), fast (including set up) and safe from daysailing to ocean cruising...
A larger proa would tick some of these points but shunting is IMHO of limited use in limited waters as well as an obvious disadvantage due to loss of momentum. Therefore this thread... .
By the way (and totally off-topic), another option to obtain hull width for king size beds in a trailerable boat with two hulls would be asymmetry above the waterline e.g. a cat with one pod (or two pods longitudinally offset) as extension of the basic hull width. No idea of how this asymmetry in windage and weight distribution would affect the sailing properties... .

 

Easy to trailer & set up along with a King size bed is getting pretty close to a "dream" of the "in your dreams" variety.

For cruising and casual day sailing, the handling of a shunting Proa may not be as bad as you seem to think. Have you poked around and tried to find first hand accounts of this mode of sailing?

 

Well, the accounts on shunting are very positive, indeed! But nevertheless it is essentially a loss of speed to zero in comparison to the slowing down while tacking.
As I'm only an armchair sailor I asked in my first post for first hand experience (or educated guesses) in the direct comparison of proa and outrigger. Especially thinking of sailing in limited spaces like harbours, against (tidal) streams - everywhere, where it gets narrow, seems to me not very appealing in a shunting proa.

The king size bed in a trailerable boat is not so far fetched, the width limit of 2.50 m is more than sufficient for that - the problem is to design a boat with multiple hulls to accommodate it.
One solution is a trimaran with a big mainhull and folding amas, but with only two hulls it gets more difficult, as symmetry doesn't allow for hulls to go wider than 1.25 m.
Ok, a foldable cat with standing height in the hulls and king size accommodation in a removable centerpod may be another option, but going asymmetric can also provide some interesting solutions.

 

Tacking Proa

I have been a lurking here.

I was going to build a Malibu Outrigger, got the plans and got as far buying and beefing up some windsurf some spars, but changed my mind, not because the MO is not a good boat, but for the simple reason I wanted to have a light boat that I could stand on and move about...may sound insignificant but a do like relaxed high speed cruising with a beer...and easy rigging and travel, like the Ninja...but maybe a bit roomier and dryer.

I believe some of you read those past posts. It was a sort of evolutionary process.

I even bought some foam for the outrigger or ama, but decided the mess was not worth (stuff is a super pain to sand) the trouble and figured out how to use a PVC base with a bit of foam and wood...

So, I moved on to working on building a tacking proa with a Windmill hull...and still working on it. I thought I had acquired a glass hull from agent out east but he disappeared on line.

Have also kicked out a very high aspect soft wing "sail" on paper, but that is now on hold until I dredge up a Windmill hull.

At this point it is a project waiting for the main ingredient.

Just comments...I do not wish to hijack the thread, so consider my interjection as rhetorical, please.

Just thought I would add me to the list of fellow proa lovers, though it is smaller, more relaxed version.

 

Peterchech, maybe a Malibu Outrigger stub mast with carbon spars and sprit-set jib, might be an efficient combo?

Seems easy to figure balance as well, with such a setup. A sort of crab claw/sloop rig.

I get that Windmill hull, that is how I plan to power it, at least at this point.

Sadly, looks as though I am building the boat backwards. I have the carbon spars, stub mast, no hull...so far.

Winter, no hull to get ready...time expiring...

 

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BB, you might consider building a hull from Clark Mills plans-it's just 1/4" ply. You might be able to modify it easily to be more suitable for your purpose.

 

tacking-proa or tacking outrigger, whichever you call it. They are not bad boats. Sure they are not sailing perfection like a well balanced proa, but they are pretty good.

They are the standard boat for Madagascar, New Caledonia and Samoa. Proas (shunting outriggers) were confined to micronesia and generally did not go as far as polynesia (a simplification I know). Some tacking outriggers were as far as Hawaii and are still there.

For more gentle and protected areas like Indonesia and the Phillipines the double outrigger was/is much more common.

Think those in this thread know all this though.

I added another tacking proa today, 10m long, simple aluminium boat. Not refined but looks ok, cheap to make and still trailerable, they launch it from the beach, could easily cross an ocean.

I think slingshot had that sliding mechanism that you refer to. On each tack the outriggers slided so that they always acted as a counterweight. The other outrigger lied flush with the main hull, could cause some drag though if there was a seaway or the boat heeled.

There are now 65 links from main page, probably 50 of which link to real world tacking outriggers. They are generally simple boats, not speed record breakers, but they work.

Sure if you have a spare $400,000 go and buy a large catamaran, for those on a budget where money is a fraction tighter and speed records are not everythinjg the tacking-outrigger has its place.

In the few years now (3 years I think) I have had the site, it seems almost all tacking outriggers I see seem to work pretty well. Some proas work well and some just dont work at all (a bit hit and miss).

I doubt tacking outriggers will ever be popular (people are conservative) but they work well.

regards
N Peter Evans
tacking-outrigger.com