Proa Questions: Atlantic vs Pacific

[Gary Baigent]

Originally Posted by Alik

Rob, weight is specified with crew and some payload, for both boats.

For Formula40, I didn't change source file - it is original sample from Wolfson with weight of 4843kg used in calculations.

Well it is a completely BS figure. If an old F40 weighs 1800 kgs sans crew, then a modern X40 in mostly carbon is going to weigh a lot less. How many crew do they carry, 4 - 5? ... still a BS figure.

[Alik]

Originally Posted by Gary Baigent

Well it is a completely BS figure. If an old F40 weighs 1800 kgs sans crew, then a modern X40 in mostly carbon is going to weigh a lot less. How many crew do they carry, 4 - 5? ... still a BS figure.

Does it matter? As one can see catamaran that weights 4840 kg is faster than 3000kg proa...

[ThomD]

And does that mater? These are radically dissimilar boats. I really never seriously thought an HP would outsail a crewed high performance multihull that has been refined over decades. Since nobody is even attempting that use, it possibly answers in the negative what these things are good for.

[Alik]

Originally Posted by ThomD

And does that mater? These are radically dissimilar boats. I really never seriously thought an HP would outsail a crewed high performance multihull that has been refined over decades. Since nobody is even attempting that use, it possibly answers in the negative what these things are good for.

I don't think cruising boat should 'outsail' anyone either. So why we are talking about perfromance as top priority, in case of proa?

Let's make a list of properties, and estimate them using numetical factors, from 5 excellent to 1 inadequate, for both proa and performance cruising catamaran of compartable size:

Esthetics
Performance
Comfort
Safety
Cost

[ThomD]

I'm with you to some extent on that. I got interested in HPs largely from the perspective of Rob's seasick wife. I like no drama easy flat sailing. It has to be fast at some level, or there is a better option in another boat. I also think mostly of very simple boats since i build stuff myself.

People didn't buy the Ford Mustang in large numbers because it was categorically better than every other car on earth in every respect. People will find stuff to like about your boat, or not, but it doesn't take a sledgehammer. One interesting thing is how people have wanted more and bigger HPs. In my think small way, I have never really thought of it as a big boat. Some of the advantages start to pale for an easy handling boat once it gets to the budget and crew size where other options are just fine too.

[Alex.A]

The size thing is an issue - but then he's aiming at charter - how many people will charter it if they've never shunted a proa before? Crew in the smaller hull?
I also thought smaller/simpler but Rob says no.
So are we back to a pac proa
Worked on Jzero - once the beams were beefed up........ At least in a pac, you are using the bigger hull - even if space is still limitted. As to why they haven't caught on - because they can capsize. But then so can all multi's
Dont think racing comparison works - but harry's are promoted for speed....

[Alex.A]

Looks : some find them beautifull - but i think most dont? The wife says it looks like a mono with training wheels.
Performance - thought it was a no-brainer...... but is it? Large cruiser - maybe not....
Comfort: not if you want the performance....
Saftey: WTW would have to be a yes - but without more miles/longer voyages?
Cost: fine compared to large cats - but nothing in the "economy" range that i and a few others find themselves....

So - a question to all interested in proa's - what is their appeal to you?

The appeal to me would be less to build - therefore cheaper and quicker.
Less carry capacity can be made up with extra speed - tho' not always practical or pleasant.... and i'm light/minimalist type anyway.
Economy wise - i'm limitting it to too small - but still possible - just wont fill most people's needs/wants.
There's a 40' Harry for sale for A$ 86K......

P.S. - i do think they are beautifull too.

P.P.S. - What would the polars look like for a pacific proa?

[rob denney]

You use a "catamaran template", and produce proa polars! No indication of which hull is to leeward, or whether the polars are an average of the two hulls.

I would say your proa polars are:

understated broad reaching and running as the headsail and the slot are always working on a ballestron rig. I would estimate 50% of wind speed ddw, but have never tested it with instruments.

The high speed bulge should be much deeper, maybe from 70 degrees round to 120-130 degrees as the apparent wind is dragged forward at high speeds.

What the proa polars/catamaran template won't show is the effect of:
2 offset water foils rather than 4 in hull ones
a fully rotating rig with an unstayed mast
two double ended hulls of different lengths and l/b ratios,
rockerless, very high prismatic hulls,
less windage than a cruising cat,
the effect of waves

I would love to work with you to improve the accuracy of the polars (maybe using my 7.5 beach proa and the 15m when it is launched), but based on what I can prove by photos and videos vs your polars, you still have a lot of work to do.

I have skippered (and capsized) a F40 race cat.

My experience suggests that not only would a grossly overweight F40 be much slower than your polars state, but it would also break as soon as it got to normal hull lifting breeze, which is about 10-12 knots. There is no way Wolfson could have tested such a boat in a meaningful manner to compare facts with the polars. I agree with Gary about the value of such polars.

Re your suggested grading of proa and cat attributes: Go for it. I have listed the proa strong (and weak) points earlier in the thread. You give them a ranking compared to a similar cat. Support the rankings with actual, provable comparisons and explain why you chose them.

Suggest you leave out aesthetics as this is purely subjective. Add in resale market size if you like, and mooring costs.

Alex,
I am not "aiming for charter" with any of the boats mentioned on this thread.

Read what I said. Small is good, proas are simpler. Short is slow, unsafe, uncomfortable and scary.
Let me know if any of this is unclear.

You can have as much space as you want in a harry. The more you have, the more it will cost. Same as any boat. Will increased space in a stressed hull weigh more than the same in an unstressed hull? You tell me. Compare Jzerro and harry weights if you still aren't sure.

There are videos of cruising harryproas sailing comfortably at windspeed under main and jib. There are pictures of a very quick and easily built low cost harry. You call this promotion, I call it validation. Either way if these aren't attributes you want, don't get a harry.

rob

[rob denney]

Hard to keep up with you guys.

Originally Posted by Alex.A

Performance - thought it was a no-brainer...... but is it?

You tell me, but make sure you say what your opinion is based on. The boat in the video or the shonky polars.

Originally Posted by Alex.A

Comfort: not if you want the performance....

Have a look at the boat in the video. Ask yourself 1) is the boat performing well? 2) Do they look comfortable?

Originally Posted by Alex.A

Saftey: WTW would have to be a yes - but without more miles/longer voyages?

How many do you need? And when they are done, will will you consider them to be "promotion" or verification?

Originally Posted by Alex.A

Cost: fine compared to large cats - but nothing in the "economy" range that i and a few others find themselves....

Please define economy range, and what boats are in it.

Originally Posted by Alex.A

What would the polars look like for a pacific proa?

Even worse than those for the harry, if the same "template" is used.
rob

[Alik]

Originally Posted by rob denney

You use a "catamaran template", and produce proa polars! No indication of which hull is to leeward, or whether the polars are an average of the two hulls.

Ridiculous what You say, the input is correct. There is separate input for windward an leeward hulls.

I would say your proa polars are:

understated broad reaching and running as the headsail and the slot are always working on a ballestron rig. I would estimate 50% of wind speed ddw, but have never tested it with instruments.

The high speed bulge should be much deeper, maybe from 70 degrees round to 120-130 degrees as the apparent wind is dragged forward at high speeds.

So my suggestion is - test it with instruments, then we can discuss it, OK? Otherwise it is not my level of discussion.

What the proa polars/catamaran template won't show is the effect of:
2 offset water foils rather than 4 in hull ones
a fully rotating rig with an unstayed mast
two double ended hulls of different lengths and l/b ratios,
rockerless, very high prismatic hulls,
less windage than a cruising cat,
the effect of waves

This is purely Your guess, how You know what catamaran template shows or not, in VPP that You do not use? Template means definition the condition of hull flying; say for pacific proa trimaran template should be used. FYI, all these correctins were made excerpt wave that was excluded in both cases.

I would love to work with you to improve the accuracy of the polars (maybe using my 7.5 beach proa and the 15m when it is launched), but based on what I can prove by photos and videos vs your polars, you still have a lot of work to do.

Actually I am not going to involve in detailed proa reasearch, but if You have some measurements pls lets compare.

I have skippered (and capsized) a F40 race cat.

My experience suggests that not only would a grossly overweight F40 be much slower than your polars state, but it would also break as soon as it got to normal hull lifting breeze, which is about 10-12 knots. There is no way Wolfson could have tested such a boat in a meaningful manner to compare facts with the polars. I agree with Gary about the value of such polars.

Ask this question to WU, but those guys are quite experienced. Of course, there could be some differences in predictions with reality (known problem with all performane software), but it is not likely that same software with same methods underpredicts one boat and overpredicts another one.

[Alex.A]

Was thinking economy/ comfort ie in smaller proa. Still thinking 30'.........
Verification. What do you look at for a cruiser - other boats that have done it?
Whats with the speed arguement anyway? You sell cruisers - and who's going to cruise at 16 knots? WTW is the type thats makes sense for cruising - no arguement there.
Cost wise - you say 50'er/15m forAus$50k but there's a 4yr old 40'er for 86K for sale..... you later add ex rig tho'.

[ThomD]

First HP plans were for 36 foot, so you aren't that far off, as with all boats, people rapidly get greedy.

Rob has several times metioned he thinks Jzerro 1 was RB's best design, it is basically the ama from a Searunner 31 with two ends, ie ply and hard chine. Of course he isn't saying it's ideal, but it does go to show how the ante keeps rising.

[Gary Baigent]

Here is a real simple basic for you to get your head around Alik: 2 race multihulls of same length, say 40 foot, cat and Harry/Pacific type proa, both optimised for similar sail power in platform overall beam; so the proa ends up narrower, immediately equals less weight and less windage, the windward, crewed proa hull is also much smaller and lighter (although it carries crew) than cat's equal sized one, ditto, three cat beams, one airfoil or two for proa, ditto, no dolphin striker, no seagull striker if there is a cat forward beam) no prod assembly equals another proa gain, smaller foil numbers (and areas), ditto, rigs to deliver equal power to both boats: cat's has to be larger, therefore less weight and drag for proa, however the unstayed balestrom mast, canterlever construction proa mast base areas would possibly be near equal weight to cat's conventionally stayed rig, but now we have two completely different sized boats ... but of equal righting moments and it is pretty easy to figure which is going to be the more efficient. Now do your beloved polars, but remember bigger and heavier and more wetted surface area in the catamaran's case, is going to be .... unfortunately slower .... in the real world of wind and sea.
Back in the old days the world speed record was held by a Pacific proa (Crossbow), and then a slewed cat (Crossbow 11) which was really a Pacific, one way direction Harryproa; later Yellow Pages was another sort of foiled proa - can you tell me of any conventional catamarans that have held this record?

[ThomD]

Wouldn't that be one point of sail? Asymmetry might be at it's best in that case. It sorta proves the point. There have been lots of proas for speed records, I remember seeing pics of some very fierce French ones.

[Alik]

Originally Posted by Gary Baigent

Here is a real simple basic for you to get your head around Alik: 2 race multihulls of same length, say 40 foot, cat and Harry/Pacific type proa, both optimised for similar sail power in platform overall beam; so the proa ends up narrower, immediately equals less weight and less windage, the windward, crewed proa hull is also much smaller and lighter (although it carries crew) than cat's equal sized one, ditto, three cat beams, one airfoil or two for proa, ditto, no dolphin striker, no seagull striker if there is a cat forward beam) no prod assembly equals another proa gain, smaller foil numbers (and areas), ditto, rigs to deliver equal power to both boats: cat's has to be larger, therefore less weight and drag for proa, however the unstayed balestrom mast, canterlever construction proa mast base areas would possibly be near equal weight to cat's conventionally stayed rig, but now we have two completely different sized boats ... but of equal righting moments and it is pretty easy to figure which is going to be the more efficient. Now do your beloved polars, but remember bigger and heavier and more wetted surface area in the catamaran's case, is going to be .... unfortunately slower .... in the real world of wind and sea.
Back in the old days the world speed record was held by a Pacific proa (Crossbow), and then a slewed cat (Crossbow 11) which was really a Pacific, one way direction Harryproa; later Yellow Pages was another sort of foiled proa - can you tell me of any conventional catamarans that have held this record?

Gary, there is no point to discuss it without having measurements of proa speed. There is no reason why I should not trust these calculations, done by well proven commercial software. Pls note that my Ph.D.dergree is in performance analysis and hydroaerodynamics of sailboats; I find it amazing that some belive that there could be childish mistakes of not including basic proa factors in calculations

When playing with software I did few estimates, say given same rig type, sail area and weight to both proa 15m and 40' cat, higher RM to proa, etc. So the result is: proa shows faster at higher windspeed when the hull is flying. Before that, cat is faster.

In this particular case with two polars posted, proa is slower due to smaller sail area practically available.

Anyone who claims that these polars are wrong are invited to provide their own calculations or results of full-size mesurements Then, we can discuss it with numbers in hands, not with emotions supported by 'years of experience'