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PROA SA/D & BRUCE NUMBER

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Has anyone got a really clear Idea where these numbers should be for a Proa?  More specifically for something in the @ 20-24’ size, @ 1100lbs, small cabin and 2 bodies for a several day excursion?  It seems people have noticed that less sail is required than for monohulls or other types of Multihulls.  The kind of speed Skip made on P-52 with only his club footed jib comes to mind.  I’m guessing the fine hulls and low wetted surface compared to other boats make these numbers lower than usually accepted for significant speed.

Tom

     

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Perhaps a bit less but not that much ( a mealy mouthed answer for sure).
Actually I think that your sail area is still dependent on sail area/ wetted surface ratio and you have to make your own judgement. Nomad (P52 ‘s successor, if built) will have about 165 s.f. of sail area….but… it will be easily reefed in several stages.

cheers,
Skip

     
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Skip,

P52 and Nomad are largely what I’m driving towards.  I’ll probably be a bit heavier due to the fact that the weather quite often sucks up here in the PNW, so I’m looking for a little more “Inside” volume.  I’m wondering if I can get enough sail with a 20’ stick of aluminum for a mast and 8’ battens…...and that’s limiting me to @ 150’ squared after mast bury and deck clearance for the style Junk sail I want to use.

What kind of SA/WS number do you shoot for?

Tom

     

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Tom - 14 March 2012 10:28 AM

Skip,

What kind of SA/WS number do you shoot for?

Tom

P52 as originally designed was 840# tandem with a SA/WS of 3.13:1.
Nomad is still a work in (slow)progress but I’ll be OK with anything between 2.5:1 and 3:1
FWIW P52’s solo SA/WS ratio with the 48 s.f. clubbed jib was about 1:1 probably a little less. At that it wouldn’t ghost worth a damn but could easily maintain 12 mph in the right conditions. Please note that I’m neither a professional nor expert at this stuff but it is fun.

Skip

     
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Fun is the key.  I sell furnaces to pay the rent.  Proas are just the latest fetish in what the woman calls my “Boat Porn Addiction”.  What does she expect, she started dating a man that sold a perfectly good house to buy a 40 year old wood trawler and move onto it.

I’ve almost got a deal cut for about 20’x30’ of heated shop space at a rock bottom price.  Little does she know it might soon get worse….

You may not be a Pro, But I’m really impressed with P52.  It appeals to my aesthetic and I like your balance between practical, performance and pretty.

     

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Hi Tom you asked me in another thread
“I’m also curious how much sail area you ended up with and how adequate you think it is”

Kalapunas weight is estimated 250 kg ready to sail. With me on board around 330 kg. I started with a sail area of about 19 sqm, and now ended with 17 sqm. SA/WS is 3.7:1 and SA/D ~51:1 (only with me aboard)
Alone I can sail till a wind force of ca, 15 knots. At last the ama is hopping from wave crest to wave crest, and I run the risk of capsizing. Using the polynesian reef with my crab claw makes Kalapuna extremely lee helm. For more wind, and more booatspeed I need more weight to windward eg. a second sailor. Then sailing becomes a fast, but wet pleasure ...
In my second video (http://youtu.be/9QBCwMsplo4) we sailed in a threesome at estimated 12 knots of wind with a good speed in comfort.

     
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Thank you Othmar, that helps a lot.

Tom

     

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