Proa Questions: Atlantic vs Pacific

My understanding is that the small ones are a) guys who like to experiment and/or are sick of some or all of the cost, hassle and effort required for cats, or b) people wanting to re do the ancient polynesian thing, in modern materials, although they usually use the cheapest materials possible, and have ordinary results.

There are very few large proas, of any type. Near enough equal numbers of Pac (5 that I can think of, including 2 of Russ' which aren't sailed currently) and 4 harrys. Difference is, there are a bunch of harrys being built, but no Paciifics.

If you define a Pacific proa as one with low enough righting moment to fly it's hull more often than not, then no matter how big, they will be lousy cruisers as you will always be moving ballast. If you define them as non hull fliers with the accommodation in the lee hull, then at some size, they will have heavy enough windward hulls to work the same way as harryproas do.

Read the earlier posts for my thoughts on pods.

Jamez. I originally called them weight to windward pacific proas, but got such a hard time from the traditionalists that i changed it to harryproa. While in some ways your categorisation is correct, for the purposes of this conversation, it is probably best to stick with Atlantic, Pacific (maybe split into hull flying as often as possible/need regular ballast shifting and hull flying as rarely as possible/weight in the windward hull sub types) and harry.

Alix,

Will publish the data as I get it.

rob

 

thank you! finally, some cooperation between you two!! i can't believe it took 13 pages and a month... i am sooo looking forward to the data. wish i could be there to help.

re. "local wind data": what kind of instrumentation is best alik? rob's going to want an anemometer at the top of the mast, no? and a way to measure mast rotation to get apparent wind angle and speed. and a paddle wheel and a compass to get boat angle and speed. from that true wind direction and speed can be computed. GPS would be screwed up by current, no? tacktick.com makes a good system that i've used on farrier trimarans with rotating masts. pricey. but, if that's an issue, i certainly would chip in.

oh how exciting! finally we'll be able to put these nagging performance questions behind us!!

 

this is from the OP. i didn't see confirmation of his guesses. are they about right?

what about a harry's weight distribution, loaded and unloaded?

i'm also curious about a harry's "bridgedeck" clearance.

thanks for any info, couldn't find it anywhere,

ben

 

if you're limited to 30', want a multihull, and have reservations about a proa, then you should consider a trimaran instead. catamarans that short don't have room for a stand-up bridgedeck AND decent clearance underneath. and the hulls are barely "useable" because at that length they're pretty narrow. the main hull on a 30' trimaran, however, is substantially wider. and you can always use the skinny amas for storage. ian farrier makes this case quite eloquently on his website.

ben arthur
weta trimaran #358 (14'er)
(and dreaming of a big cruising proa someday...

 

Thanks for the extremely kind offer. Initially, I intend to use a gps and wind information from the local weather centre, a couple of miles away (I have never had much faith in wind instruments mounted atop a pitching, rolling mast with air from the sail flowing around the tip of the sail). Given all the variables of sailor, rig and hull/foil finish, this will be accurate enough to start with. I will also be racing against the local A cat and NACRA fleets.

If Rick Willoughby (who has produced some polars for the 7.5m) or Alix (let me know if you want the data for your polars) can tune their numbers to the extent that my results are not accurate enough, then I will stump up for some instruments. However, I think that a gps track and speeds, an allowance for tide (rarely more than 1 knot) and the local weather station data will be more than enough.

As well as performance data, I hope to sort out a righting technique which will scale up to the big boats, figure out how to short shunt up and down a 25m wide canal, and racing shunts and gybes. Should be a lot of fun.

A suggestion. Instead of forking out for instruments, use the money to jump on a plane and come out for a look and a sail. Bring the missus and make a holiday out of it.

"About" is the operative word, there are few published details, and numerous different boats.

About 60/40 depending on the particular design. Probably about 40/60 unloaded, depending on definitions, etc.

900 mm/36" on the Visionarry, bit less on the 12m/40'. It reduces under the windward side of Vis as this is never depressed and rarely sees any direct waves.

rob

 

I like proa's - but they are better in longer sizes.....
What i'd win with a proa would be less beam - over a tri.
I dont particularly need/want a stand-up bridgedeck either (would be nice but not essential...).
At this length tho' - i keep coming back to a pacific proa - because with a pod added, it'd give headroom and more storage space.....
But they come with their own issues.........
The other proa problems are rig and rudders - where a cat can have nearly any rig type.
Space wise - i like the cat for its 2 hulls - even if headrm is lost.....
EVERYTHING IS A COMPROMISE.......... :?:

 

All multis are better in longer (not bigger) sizes.
You would get less storage space in a Pac proa than a harry.
A proa can have cat type rudders, if you don't mind cat type rudder problems (damage in a collision, likely breakage when caught in irons in big seas, potential leaks, etc)
A proa can have pretty much any rig a cat can have, if you don't mind the cat's rig expense, lack of utility, maintenance and weight.
No reason why you can't use both hulls of a harry proa or an Atlantic proa.

Harryproas are my attempt to get round the shortcomings of conventional multihulls. If you are happy with those shortcomings (and many people manage them quite satisfactorily), then they can also be incorporated in a proa.

 

Rob, You need anemometer for apparent wind speed and direction, not station data. Fix it where the air flow is not much effected by sails. Standard height is 10m, bit this can be re-calculated after.

GPS measurements for speed are OK.

 

Wind instrument...

For any HarryProa style boat, it would seem that putting an annemometer on the winward hull at about COE height would be far enough ahead and out of the sail's influence. Having it at the COE would pretty much give a direct value for force calculations.

For my test mule (MLM) I was thinking something like this (Cheap anemometer) rigged on a home made weather vane. I could set the vane's "pointer" on a protractor and get apparent wind direction. With the GPS data it should be easy enough to back calculate true wind. (assuming current isn't significant).

 

small trimarans can fold. so beam is not an issue in a marina. can even be motored out a narrow channel while folded. as well as put on a trailer and driven down the highway to a new cruising destination / regatta that is too far away to sail to, all within the legal road widths and without any special oversize permits. and stored in your backyard overwinter.

http://www.f-boat.com/pages/introduction/folding.html

i'm not saying that tris are better than proas. rather, short ones are way better than cats for cruising. you shouldn't even be considering a cat of that length for that purpose.

 

And yet many do..... many more than in tri's?
Cost being an issue - the F boats are out.

 

it'd be best to log both GPS and wind data, so that afterwards you can crunch the numbers on a computer. here is a thread describing what others on this forum have done:

http://www.boatdesign.net/forums/on...ols/laptop-interface-tacktick-nmea-21566.html

 

$$$$$$

Thank you, that was an interesting read.

You are definitely correct! I would much rather have the data time synced automatically with the GPS data. I have software I've written running on Windows Mobile Phones using external bluetooth GPS antennas. I'm currently playing with accessing multiple GPS antennas so I can determine boat leeway (Angle of Attack). If I could get a anemometer / wind direction transducer using bluetooth, I could easily integrate it with what I already have and do real time true wind calculations along with leeway and VMG calculations. Unfortunately getting the transducer is the problem. The TackTick T120 is $750!

My test boat's entire build budget should be less than half that! At $30 versus $750, my threshold of pain can jot down a whole lot of hand written numbers.

Would you happen to know of a cheap substitute? I'm not looking for long-term, marine grade stuff... jury rigged, half-*** would be fine. Main thing... it just has to output some data (preferably NMEA 0183) via bluetooth. Jeeze... my last GPS antenna with bluetooth, battery, charger cost a whopping $18.

 

Inq. Have broken out your 750 budget? I build cheap, but for the boat you have started? What about the spar?

 

Out of left field...

Depends on which boat of mine you're thinking... Are you on the HarryProa site? The only one that I've posted on BoatDesign is going to be a 60' cruiser. Its budget is not constrained to $750... its not even constrained to be under $100K. I put it on the back burner, because I wanted something to play with next spring... maybe even race.

The $350 boat I referenced above is simply a HarryProa style test mule. Its meant to be dirt cheap and quick to build. Its all ply. I have all the wood purchased, cut and some formed into the hulls and beams. The lee hull is 30 feet and the windward is 16. The mast and sails are from an old Hobie 16. So far, my out of pocket is $90. I have some glass cloth and tow and about two gallons of epoxy. Although I'll count those in the final cost, they aren't really part of my budget as they were purchased long ago for "just playing around."