Proa Questions: Atlantic vs Pacific

I am looking @ 9m/30' max. That'd be longest for either hull.....
So unless equal length, the windward hull would end up small for a cruiser?
If i build a cat that length, i get 2 useable (8m+-) 9m hulls.
No racing - minimalist cruiser is still my goal. Space at that length, i think the cat wins. price? I think that hulls wise it will be similar but i'd have to get a rig and sails made - this at SA prices would be big. Cant argue ease of sailing as never been on a proa.

 

Hm, this is not really a saving, this is due to minimalism - smaller interior space, reduced equipment, etc. I doubt if there is any saving on structure for proa.

But this accommodation can't be compared with accommodation of 15m cat.

About same.

Suppose it is same, for unit of weight.

But market is VERY limited, how may years one has to wait to sell it??

This type of mast is more complicated itself, and also requires stonger structure to support huge console load.

For catamaran of same beam and weight - almost same. Yes, proa has CG shifted more to one side (I doubt it is too much - the rig is heavy and it is on opposite side), but this makes it less stable in opposite direction.

OK, I don't have such experience with proa, but a lot with cats and tris I have experience of driving a cat with one hull much heavier that other - it is not pleasant steering, I would say.

OK

Yes, if You shift CG to one side, the stability will increase on one side but decrese to other. Stability is rated for smaller value of RM, and it makes sence on waves.

How about longitudinal and diagonal stability? It is less.

Sorry, but I don't see any advantages of proa compared to cat of same beam and weight.

Yes, the boat on video running at low Fn. Once the speed will increase, the stern will just sink...

There is no flare; even on video with smallr waves it does not work as one would expect for searowrty boat.

1.7t for 15m? It is nothing.

 

I’m sure Rob doesn’t need my help… but hearing another voice might actually encourage further study by those individuals considering a Proa. As I am one, I sometimes have trouble sifting between facts and drummed up misconceptions or outright, self serving deceit. All my correspondence with Rob has shown me that of individuals actually designing, building and selling, he FAR surpasses ANYONE else for openness and thoughtfulness to an individual’s questions. There are several other experts on this forum that are comparable in their willingness to educate, but they are in the minority. Most experts on this site will totally ignore a question. Maybe because they feel it’s beneath them. Or, because if it won’t line their pockets, it’s not worth their time. Often, they want to convince you it’s out of the noble cause of protecting the ignorant from hurting themselves.

I’ll take number 6 as an example, although I think I could defend the rest also.
Rob clearly said for a Proa and Cat of equal weight, that the righting arm will be higher. Anyone who passed freshman engineering Static’s will agree with this. If they have the same beam, the Proa which has a higher percentage in the windward hull WILL have a higher righting moment.

Cat: 10,000 lbs, 30 ft beam => righting moment = 10000*30/2 = 150,000 ft-lbs
Proa: 10,000 lbs, 30 ft beam, 75% windward hull weight => righting moment = 0.75*10000*30 = 225,000 ft-lbs.

Hmmm! Looks like 50% more righting moment to me!

 

When comparing cats, tris and proas, the loaded displacement is the only reasonable referense. Displacement also fits very well with costs and space. If we look same displacement cats, proas or tris, proa is simpler to build, has much longer waterline (so it is faster), pich less (due the higher longitudinal stability) and can carry more sail area (and have more power to weight ratio). Above is for weigth to windward proa only, traditional pacific proa can carry much less sail area.

Also due the longer waterline, the length displacement ratio is very high and so the double-ended, high Cp, hull does not squat in higher Froude speeds. Also the sailing drive moment helps here.

Weight to wind proas are odd and rare boats, but it doesn't make them bad. How did western NA:s took their attitude against catamarans and trimarans in the 50's. Souds familiar, Alik...

Designed one, build one, sailed one, loved one and given him to good hands...

Terho

ps. But proas are open water boats, not for narrow route archipelagos.

 

Thanks for such compliment, be sure, I passed 'freshman engineering statics' and even more The issue is that stability (in terms of safety) is estimated using worse case of inclination - refer to ISO12217 or any other safety standard as sample of approach. So for proa it will be assessed using inclination towards 'windward' side and it will be less than a cat. In reality this is a case of breaking weave, etc.

Surely it sounds reasonable for sail carring ability. But does this gained extra thrust work, given obvious disadvantages of proa in hydrodynamics? Extra RM should be compared in only terms of overall performance. Do You have polar plots of cat and proa of same dimensions and weight?

I am not convinced about advantages of canoe shapes for higher speeds. I have done a study of optimum catamaran hull shapes for different speeds, the paper was presented at CPBS-2010...

 

So proa is longer? How about marina fees then?
Let's compare boats of similar size, otherwise we will never get a conlcusion.

Yes, that's for leeward hull. How about windward hull that is short/heavy and DLR is quite high?

So, why don't we see hundreds of proas sailing then?

I am just trying to understand why some find proas attractive, no prejudice but I am conservative (as practicing NA should be). Maybe one day I will design one... if someone orders

 

"A lot of proas? Where???
I still want to hear something about real advantages..."

You are talking proas generally, one has everything from Malibu Outrigger to Gary Dehrings book. If you cruise around the net there are a lot of people who have built boats. Not a lot as in "my harbour is stuffed" but a lot as in "I went blind reading about all these projects". Since very few of these are the same, it does add up to quite a few boats.

Well advantages wise, to quote 45, "I didn't just get off the melon truck". I need to see your cash. What would you consider an advantage? Cost effective; got someone laid; was faster than other boats (Read project cheers) would you be swayed by Newick who seems to continue to believe in their potential as the designer emeritus of the multihull clan; Or would you take Jim Brown's word for it? Sure Russ' dad, but a guy so strait spoken he should be a living treasure.

I think advantages is really subjective, but proas do have certain distinctions, these may or not be advantageous to a give individual. The Polynesians certainly valued proas. Speed, simplicity of building a boat of that size. They seem to have enjoyed them for hunting type activities, a cross between a sports car and a pick-up truck.

HPs are a different mater, what appeals to me is their separation of all the "motor" parts from the accommodations. This appeals to me, and solves a variety of real problems that exist: My current tri has daggerboard in the accoms problems to the max; When built the boat compromised on the accoms, and they were very small by any standard, enter 3 new children. I would very much prefer to be facing the prospect of replacing the people pod not the whole boat. Just the other day we went for a little sail, and it was very sunny with people on the nets and the amas, we did not have adequate shelter from the sun, there is no room for any of us to sleep on board, etc... What was cool was how well the boat sailed on a "breathless day, something I would loose with an HP. I have other sailing interests where a people pod would be better. I don't believe the central location of stuff in an HP is sufficient in our cold climate, it isn't Jester level enough yet. But are there distinctions, sure.

 

Hmm, those advantages are just about easy way to build a boat of a wooden log. Nothing to do with today's techniques and cruising proas.

 

Displacement is the size, length is just a dimension to one direction.

In low Froude number DLR is normal, but volume is decreasing when going faster.

The marketing people are not yet interested...

Perhaps it is some kind of disparity pursuit (is this fair term?). Wanting to do something the neighborg's don't. Having experiments the others haven't? I just wanted to solve it (the proa thing) like solving the Rubic's cube or crosswords. So, I made better succes with proa...

Can you expect orders of a proas, if you haven't solve your crossword puzzle of it? A well educated person should know to do his/her homework properly before making fast, though conservative, conclusions.

Terho

 

Don't worry, though conservative, I am capable to design it

 

These are big boats - and that is where the money is....... but economy is still seeing it's butt - how does a proa compare in a smaller category? Building carbon is out there o beginners - it may be as easy as said but daunting - even if in the mind? It's great that length eqls speed - but costs go up - maintenance and mooring etc.... What of the small(er) cruiser? I love the proa concept but still haven't been won over. As for numbers - it wont happen as convincingly as cats and tri's - why? - shunting. A stupid thing - but it's unnatural to "norml" thinking. A tacking outrigger - worse off than a proa!!! will sell easier?

 

Ok, if you don`t like logs what about this, whatever it may be...

http://www.boatdesign.net/forums/multihulls/worlds-largest-proa-33923.html

Always liked this design idea for low resistance charter boat, with good launching fascility:

http://www.seakayakvacations.com/Kayak_Voyagers.htm

"So, why don't we see hundreds of proas sailing then?"

I don`t see hundreds of any multihull sailing around here.

 

I like the idea of kayak mothership, seems good application of proa.

For performance: did You ever drive wide powercat with only one engine, at relatively high speed? It is quite difficult to control, same will happen with proa. Moreover, at slow speed the controlability of power proa is even worse - the advantage of cat is ability to steer by engines.

 

I'd like to see them drive that Mothership at high speed! Can't wait for the Youtube video!

 

I think at over 10kts the engines should be rotated to compensate the effect of side hull...

And turning at full speed will be possible to one side only