Boat Design Forums  |  Boat Design Directory  |  Boat Design Gallery  |  Boat Design Book Store  |  Thanks to Our Site Sponsors

Go Back   Boat Design Forums > Design > Multihulls
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read Most Recent Posts Gallery Images Search

Reply
 
Thread Tools Search this Thread Display Modes
  #16  
Old 06-24-2010, 12:54 PM
KSONeill KSONeill is offline
Junior Member
 
Join Date: Jan 2009
Rep: 33 Posts: 23
Location: Lake Jackson, TX
Quote:
Originally Posted by KSONeill View Post
Ah, sorry, I didn't realize that was an old message. I edited it without looking.

You may be right about Atlantic proas. Take a look at the link I stuck in above, it looks like Tahiti Douche does sometimes tack. I would suppose that's just to be more maneuverable in tight quarters, but who knows.

K O'N
This niggled at the back of my mind this morning, until I went back and searched up this message:

http://groups.yahoo.com/group/proa_file/message/22545

which says in part:

1999 PRAO DE CAMPING COTIER
Camp cruiser, rigged as a shooner, of 10m; can be desassembled for trailering; it is defined as "biamphidrome" ( it sails as a Pacific Proa in light winds, and Atlantic proa in strong winds). Designed and built by Denis Kergomar at Ballaruc les bains, France.

This is from a web site in French by Vincent Besin, translated for us by Laurent Coquilleau. So, what you're describing is a "biamphidrome". Sadly, googling on the term only finds two hits, the original page and the translation above. Still, it appears to have been a real boat. Well done for thinking of it yourself.

Kevin
Reply With Quote


  #17  
Old 06-24-2010, 01:25 PM
KSONeill KSONeill is offline
Junior Member
 
Join Date: Jan 2009
Rep: 33 Posts: 23
Location: Lake Jackson, TX
Quote:
Originally Posted by cavalier mk2 View Post
Not if the ama is providing buoyancy! If you have a log out there I think you have to call it an outrigger. When an atlantic gets caught aback it is relying on the weight of the ama which usually is far less than what it needs to stay up. Check out Rory Nugent in the Ostar etc.... lots of great capsize info out there.
I guess we have to define things more carefully so we're all using the same terms. "Outrigger" to me means a boat that's paddled, an OC-N for N=1, 2, 4 or 6, or a tacking boat. Google on "tacking outrigger", you'll get lots of hits for single outrigger sailboats that tack rather than shunt, and so are not called "proas". Flaquita is a nice daysailor example in Austin, Tx.

Regarding Atlantic proa capsizes, Nuget on Lady Godiva/Godiva Chocolatier/Saint Marc II/Funky But Chic (all the same boat) was capsized by a rogue wave, according to his accounts, not by going aback. Merlin/Azulao II/Fleury Michon II (all the same boat) and Eterna Royal Quartz both were damaged in collision. Rosiere lost a stay and folded up. Eka Grata went aground and was destroyed.

I don't think there's a real history of lots of Atlantic proas going aback and flipping. If there is, I've never seen it.

Regarding Pacific proas going aback, it's too broad a question, and my contention that they'll flip more easily is really not justified; I should say "flip or break something or drop the rig or something like that". Pacific proas can be any of several types. A traditional Micronesian boat like this:

http://upload.wikimedia.org/wikipedi...b/b9/Proa1.jpg

if sent aback will have the rig fall down. If the rig didn't fall the ama would sink, it's a solid log.

A more modern proa of a similar type like Gary Dierking's designs:

http://homepages.paradise.net.nz/garyd/t2.html

has more flotation in the ama, and has a fancy "pogo stick" which allows the rig to fall to a controlled 45 degrees or so, then pop back up when you scull the boat around again. I built a similar but bigger rig. The pogo stick will save you, but in a lot of wind it's a great strain on the boat. I came to think it was better to just let the rig fall down flat and then sort things out.

Russ Brown's boats, like this one:

http://www.wingo.com/proa/brown/jzero78.html

are not at all forgiving of going aback. Mark Balogh, who crewed on the boat, said there:

"We never really got caught hard aback. The mast wasn't stayed very strongly from the lee side so that was one thing you really tried to avoid. "

I think pretty clearly the rig would fall down and stuff would break in any sort of wind.

All these are more or less by design. If the rig doesn't fall down you'll either break a beam or capsize the boat. The amas are low volume; my boat has about as high a ratio of ama volume to main hull volume and sail area as you'll ever see on a pac proa, and if I go aback in a lot of wind the boat will go over pretty quickly. For one thing, if the rig doesn't fall down it's pinned against the stays, you start moving and the aft CE is trying to head the boat up. But the ama drag is trying to head the boat down. Very stable, rather hard to steer either up or down. Very powered up. Very little diagonal stability. Over you go.

So sure, there's some ama volume to help you. But the beams often aren't intended to take much stress in that direction, look at Russ Brown's beams. The ama volume is small in relation to the rig size. So it seems to me that an Atlantic proa aback and flying a hull would have a better chance to recover than a Pacific proa aback and sinking an ama. But that's a generalization, there are lots of different rigs, beam designs, ama volumes, many variables.

Rob's WTW designs are intended to be foolproof, I think, and so probably handle going aback better than any others. No stays to pin the rig, for one thing. You might still run the risk of a diagonal capsize if you got moving fast when aback, but there's no reason to, since the rig isn't pinned.

Kevin
Reply With Quote
  #18  
Old 06-24-2010, 01:28 PM
Alex.A's Avatar
Alex.A Alex.A is offline
Senior Member
 
Join Date: Feb 2010
Rep: 108 Posts: 346
Location: South Africa
Biamphidrome....Sounds cool - BUT how easy could it be to do it quickly or at sea?
How about 2 smaller ama's that slide across? The main hull would always have one tucked up against it.... but then the rig would have to be in the main hull.
And then what do you do with the deck area.... ?
Reply With Quote
  #19  
Old 06-24-2010, 01:48 PM
KSONeill KSONeill is offline
Junior Member
 
Join Date: Jan 2009
Rep: 33 Posts: 23
Location: Lake Jackson, TX
Quote:
Originally Posted by Inquisitor View Post
Cool boat!
Thank you!

Quote:
What do you think of the dual mast rig? Lower COE so you could probably carry more sail. But more to deal with. Have you found any disadvantages?
Could you recommend it for a large cruising boat? (40+ feet, 6+ crew)

Thanks for the links.
I'm sold on the schooner rig. I'd use it on any size boat. Des Jours Meilleurs is a much bigger boat with a similar rig, that's a great looking boat.

The COE is lower. That's good in all but light air. We had a race recently, with the somewhat aggrandized title of Texas Proa Championships:

http://wikiproa.pbworks.com/Texas-Pr...09-Race-Report

The white boat has a much higher AR than I do, clearly. In under ten knots I could actually keep up with him to windward (!!), and I shunt faster than he does, but he killed me downwind. I think in light air you want to get some area up high, there's more wind up there. And clearly once he gets his sail shape better sorted he'll beat me up to windward too, higher AR is better.

Still, I have a 6' leeboard to a Speer proa profile, and the boat goes to windward quite well, I'm very happy with it on that count. I wish I could go wing and wing downwind, but I can't see a good way to manage it.

The two big advantages of the schooner are: 1) the ability to control the CE of the sails when you're sailing out of a shunt. The rudders aren't working yet, it's a big advantage to be able to sheet the front sail first and get moving, then bring the aft sail on as your rudder powers up. Big, big advantage. The boat is very controllable now, I don't worry about sailing in a crowd or about pinching up too high or shunting in a lot of wind, it's all very easy. And 2) the rig is low, so the mass of the rig up high is reduced, so the boat pitches far less. The ends are very fine, of course, they're both bows, so the boat could be very pitchy. I think that's why you see schooners on so many of the French Atlantic proas. My boat is less pitchy than a H16, which has to be because of the lower rig.

Disadvantages; it's two of everything to buy and rig, and two sheets to mess with, or three if I have the jib up. Clearly one person can't steer and have three sheets in his hand, so I cleat stuff off and drive the boat more than I was comfortable with from beachcat sailing. It is nice in a lot of wind to have one sheet on a big sail, rather than three on three smaller sails. But I manage. The tops of the masts are carbon windsurfer masts and the top 8' are unstayed, so they flex off in a lot of wind, that's a built in safety feature I didn't really plan for but will be happy to take the credit. I reef both mains at about 17 or 18 knots when going to windward, but keep the jib up. Going to windward in over 20 knots I hold the sheet of the front main; if I let it off the boat comes down fine but still keeps moving. Very different from sailing a beachcat, though.

Kevin
Reply With Quote
  #20  
Old 06-24-2010, 01:53 PM
KSONeill KSONeill is offline
Junior Member
 
Join Date: Jan 2009
Rep: 33 Posts: 23
Location: Lake Jackson, TX
Quote:
Originally Posted by Alex.A View Post
Biamphidrome....Sounds cool - BUT how easy could it be to do it quickly or at sea?
Just tack or jibe. How bad could it be? Sailing in light air and you have to come about, if it's still light you shunt, if it's picking up and you want the heavy ama to windward you jibe. If it stays heavy you shunt, if it dies you jibe. Assuming the boat's sorted out for both modes, that is.

Quote:
How about 2 smaller ama's that slide across? The main hull would always have one tucked up against it.... but then the rig would have to be in the main hull.
And then what do you do with the deck area.... ?
That's, uh... Crossbow? Or Crossbow II? One of the speedsailing boats. Dave Culp has a good page on them somewhere, google around and you'll find it. I think it sounds much, much slower and more dangerous than just shunting the boat, for anything intended to be a practical cruiser. Shunting is easy and fast, you don't have to avoid it.

Kevin
Reply With Quote
  #21  
Old 06-24-2010, 02:40 PM
cavalier mk2 cavalier mk2 is offline
Senior Member
 
Join Date: Mar 2010
Rep: 192 Posts: 1,521
Location: Pacific NW North America
The atlantic proas I was thinking of were Dick Newick's Cheers before he put the pod on and the one he did for Rory. To be safe it seems like a good idea to build proas that can handle anything. There are many areas that get unbelievable wind shifts so a cruising boat should be able to handle anything, because everything usually happens!
Reply With Quote
  #22  
Old 06-25-2010, 12:38 PM
KSONeill KSONeill is offline
Junior Member
 
Join Date: Jan 2009
Rep: 33 Posts: 23
Location: Lake Jackson, TX
Quote:
Originally Posted by cavalier mk2 View Post
The atlantic proas I was thinking of were Dick Newick's Cheers before he put the pod on and the one he did for Rory. To be safe it seems like a good idea to build proas that can handle anything. There are many areas that get unbelievable wind shifts so a cruising boat should be able to handle anything, because everything usually happens!
Rob's freestanding masts and Newick's Atlantic proas with freestanding masts can't really be caught hard aback like a stayed Pacific proa can. I guess in that way they're safer, sure.

The thing is, though, lots of monohulls would be in trouble if you were suddenly tacked or jibed without warning, because of backstays or canting keels or whatever. No one seems to think they're a menace because of that. So if a boat with backstays could lose the rig from an unexpected jibe, and a proa could lose the rig from an unexpected jibe, which is what going aback is, then what's the difference?

Kevin
Reply With Quote
  #23  
Old 06-25-2010, 02:09 PM
cavalier mk2 cavalier mk2 is offline
Senior Member
 
Join Date: Mar 2010
Rep: 192 Posts: 1,521
Location: Pacific NW North America
Not much difference for racing or the trade winds, for cruising it is good seamanship to have the rig strong enough to cope with the wind from either direction, though it only needs to be maximized for one. Just a personal preference, around land masses the wind can do unexpected things and I'd rather be sailing than dragging the rig back onboard. It is hard to imagine that proas will ever be standardized, like many things there is not one "best" approach to the concept.
Reply With Quote
  #24  
Old 06-27-2010, 02:57 AM
Alex.A's Avatar
Alex.A Alex.A is offline
Senior Member
 
Join Date: Feb 2010
Rep: 108 Posts: 346
Location: South Africa
Sorry to be cross purpose here - but... for a tacking outrigger - how eqaul would the hulls have to be for the good tack/bad tack to be lessened? Would it be worth it or are we talking catamaran?
Asymetric catamaran - how asymetric can it go?
Reply With Quote
  #25  
Old 06-29-2010, 09:15 AM
terhohalme's Avatar
terhohalme terhohalme is offline
Senior Member
 
Join Date: Jun 2003
Rep: 480 Posts: 491
Location: Kotka, Finland
Quote:
Originally Posted by Alex.A View Post
In larger sized proa's - why not use the float for storage or even accomodations? Could charter - with crew in lee and guests in main hull?
More work/costs but still cheaper/lighter than a cat?
If the float was heavy enough you could have a cruising proa in either configuration?
Something like this?
Attached Thumbnails
Proa Questions:  Atlantic vs Pacific-t-harry_2_persp1.png  Proa Questions:  Atlantic vs Pacific-t-harry_2_persp2.png  Proa Questions:  Atlantic vs Pacific-t-harry_2_profile_lw1.png  

Proa Questions:  Atlantic vs Pacific-t-harry_2_profile_ww1.png  Proa Questions:  Atlantic vs Pacific-t-harry_2_top.png  
__________________
Only shared knowledge can grow.
Reply With Quote
  #26  
Old 06-29-2010, 09:37 AM
Alex.A's Avatar
Alex.A Alex.A is offline
Senior Member
 
Join Date: Feb 2010
Rep: 108 Posts: 346
Location: South Africa
Yes - like your styling! Why the schooner rig tho? I liked ping-pong's more....
Reply With Quote
  #27  
Old 06-29-2010, 01:27 PM
terhohalme's Avatar
terhohalme terhohalme is offline
Senior Member
 
Join Date: Jun 2003
Rep: 480 Posts: 491
Location: Kotka, Finland
When the free standing masts are located at beams, the structure is easier to engineer light and strong. I modelled this to Rob's customer few years ago (before global money mess) and as I remember, two mast was asked.
__________________
Only shared knowledge can grow.
Reply With Quote
  #28  
Old 06-29-2010, 09:00 PM
KSONeill KSONeill is offline
Junior Member
 
Join Date: Jan 2009
Rep: 33 Posts: 23
Location: Lake Jackson, TX
Quote:
Originally Posted by terhohalme View Post
When the free standing masts are located at beams, the structure is easier to engineer light and strong. I modelled this to Rob's customer few years ago (before global money mess) and as I remember, two mast was asked.
It also lets you control where the CE is right after the shunt, which gives you better control at low speeds and lets you get by with smaller rudders. I have a sailing buddy with an A-cat rig on his proa, who has also sailed on my schooner rigged proa. Having sailed them both for a few years, he said if he had a bigger boat he would use a schooner rig.

K O'N
Reply With Quote
  #29  
Old 06-30-2010, 10:59 PM
ThomD ThomD is offline
Senior Member
 
Join Date: Mar 2009
Rep: 108 Posts: 441
Location: TO
"I don't think there's a real history of lots of Atlantic proas going aback and flipping. If there is, I've never seen it."

There isn't a real history of APs for the most part. Cheers was caught aback and the problem was addressed with a pod. Russ's pacific proas have taken that to the point where they are self righting. If I recall Mark was on the early proa? Russ has been way out there in both the Atlantic and the Pacific, and I have his father on tape saying the boat is self-righting, though Russ doesn't like to talk it up much. This is dynamically self-righting in that it pops back up, and keeps on going, as opposed to needing to do a whole bunch of stuff as on the G32, for instance.

The problem with Russ' boat is that it works, but it doesn't really seem to be a solution to any problem other than the desire to sail a pacific proa that is very easy on the eyes. It is a particular individual's boat that works for him. Not sure it gets anyone without the emotional investment anywhere. And I say that with decades of admiration.

The harry proa really seems like the only game that ads up, and it comes with several strictures, and complexities. Also, it looks terribly wet in the video I have seen. Getting the stearing right seems terribly complex. And you need a free standing carbon mast. I have plans and will probably build one if I ever get seriously close to a cheap mast.


I don't see any reason for atlantic proas. Amas just don't add that much to weight, cost, or time budgets, and two of them have massive advantages. The atlantic idea has been around for a long time with not a lot of success. Cheers being the main exception. Hard to say what would have happened if a similar sized boat had had two light weight amas, and one stayed spar, and put the weight of the two free standing wood spars into the new ama. An equally radical idea could have been plywood folded amas of lightish construction. They might not have made it, but them the proa was hardly a certainty either. The rig could have been much more efficient ona tri, battened rotating, etc.... Want to handicap that race run a 100 times?
Reply With Quote


  #30  
Old 07-04-2010, 03:54 PM
KSONeill KSONeill is offline
Junior Member
 
Join Date: Jan 2009
Rep: 33 Posts: 23
Location: Lake Jackson, TX
Quote:
Originally Posted by ThomD View Post
"I don't think there's a real history of lots of Atlantic proas going aback and flipping. If there is, I've never seen it."

There isn't a real history of APs for the most part. Cheers was caught aback and the problem was addressed with a pod. Russ's pacific proas have taken that to the point where they are self righting. If I recall Mark was on the early proa? Russ has been way out there in both the Atlantic and the Pacific, and I have his father on tape saying the boat is self-righting, though Russ doesn't like to talk it up much. This is dynamically self-righting in that it pops back up, and keeps on going, as opposed to needing to do a whole bunch of stuff as on the G32, for instance.

The problem with Russ' boat is that it works, but it doesn't really seem to be a solution to any problem other than the desire to sail a pacific proa that is very easy on the eyes. It is a particular individual's boat that works for him. Not sure it gets anyone without the emotional investment anywhere. And I say that with decades of admiration.

The harry proa really seems like the only game that ads up, and it comes with several strictures, and complexities. Also, it looks terribly wet in the video I have seen. Getting the stearing right seems terribly complex. And you need a free standing carbon mast. I have plans and will probably build one if I ever get seriously close to a cheap mast.


I don't see any reason for atlantic proas. Amas just don't add that much to weight, cost, or time budgets, and two of them have massive advantages. The atlantic idea has been around for a long time with not a lot of success. Cheers being the main exception. Hard to say what would have happened if a similar sized boat had had two light weight amas, and one stayed spar, and put the weight of the two free standing wood spars into the new ama. An equally radical idea could have been plywood folded amas of lightish construction. They might not have made it, but them the proa was hardly a certainty either. The rig could have been much more efficient ona tri, battened rotating, etc.... Want to handicap that race run a 100 times?
There have been more Atlantic proas built and sailing than you would think. I collected some images of some Newick and French proas and put them on three pages, starting here:

http://wikiproa.pbworks.com/Images+f..._file+archives

I count ten or eleven big Atlantic proas. Just because we don't see much about something on the internet doesn't mean it's not being done, or that it doesn't work. Someone built those boats, one after the other, which means to me that they had some idea that they worked.

K O'N
Reply With Quote
Reply



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Proa questions... Inquisitor Multihulls 50 06-22-2010 02:32 PM
Info on Pacific 32 ? frank smith Boat Design 3 11-10-2009 04:53 PM
Looking Pacific Troller plans shark Boat Design 3 01-25-2008 04:05 AM
Pull of the Pacific Bergalia Open Discussion: All Things Boats & Boating 35 09-14-2007 05:47 PM
The Pacific High JonathanCole Boat Design 0 06-14-2005 01:20 AM


All times are GMT -4. The time now is 05:57 PM.


Powered by: vBulletin Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Web Site Design and Content Copyright ©1999 - 2014 Boat Design Net