Planing Catamaran!

[Doug Lord]

Originally Posted by CT 249

That 1981 record of 24.75 knots was Jurgen Honschied on a surfboard - not a surfboard-style windsurfer, but a real surfboard fitted with a mast base and footstraps. As a 2.28m 5kg sinker-style board of 26L volume, it is much faster than a longboard (around 3.7m, 16-21kg and 190-260L) in speed record conditions and its performance is not comparable. Similarly, Jaap Van Der Rest's 1980 windsurfer record of 24.45 was also set on a 7kg shortboard that also cannot be compared to something as a large as a longboard windsurfer or an Itza Cat.

Down here the '80s update of the original Windsurfer One Design (same hull, retracting centreboard, better rig) is the most popular windsurfer racing class nationally and its titles attract 40-57 sailors including multiple Olympians. There is no way such a board can pace a Hobie 16 except perhaps in the most extreme conditions. The best speed I know of is a peak of 25.4 knots (achieved by the national champ in extreme conditions and verified by one of the world's top 10 GPS speedsailors, who hit his own Formula board peak of 31 knots the same day) which may be faster than a Hobie 16, but 99.99999999999% of the time the H16 is much quicker, as indicated by its yardstick being some 38% faster.

Did I have fun on the Itzacat, Doug? Not particularly. It planed okay but it had issues. But what I objected to was the way the Youtube caption insults cat sailors by claiming that they did not buy the boat because they did not understand the concept. The planing cat concept is an old one, dating (IIRC) from the '60s. There were boats as big as 60' built around the concept here, and that failed to do what it was supposed to do.

Insulting people because they 'couldn't understand the concept' means opening up yourself to those who want to clear the record, IMHO.

Interestingly, the Youtube caption says that the boat sold to science teachers and those who 'understood the concept'. I wonder how many science teachers are familiar with stagnation points, Savitsky and other facets of planing? And if they were so satisfied with the boat, how come we don't see lots of them sailing and beating conventional cats?

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I personally saw several windsurfers pass a couple of Hobie 16's in 10-15 knots of wind and numerous other incidents like this as well-no ifs ands or buts-my boat did as well(but only on a reach in smooth water).
I don't care for the 'couldn't understand the concept' bit either-wasn't necessary.
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In all fairness, he did not specifically refer to "cat sailors":
"Few potential customers could understand the planing concept and some thought there was something fishy about it appearing to travel so fast, despite the obvious spray from it planing and the spray from the skiboat."

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Zed, when was that boat done? Any pictures? Thanks for the info!

[CT 249]

Yes, Doug, a well sailed craft of just about any type can beat a poorly sailed (or unlucky) craft of just about any type. When we were kids, we passed an 18 Foot Skiff in our 420 once. Some of the world's top Moth foilers have been beaten by Lasers at Woolahra SC on rare occasions - that doesn't mean that 420s are faster than 18s, or Lasers are faster than Moths.

I have four of the very best early '80s longboards (two ex-Robby Naish custom Pan Ams, the bronze medal winning Lechner from the Barcelona Games, and a multiple national title winning One Design) and a rather good national windsurfer record, and I am 99.9999% sure such early '80s boards would not consistently outpace a GOOD H16 in 10-12 knots. Sure, you may be able to pass a slow H16 but passing a slow example of any type is no proof of relative speed. May I ask how many times you have seen a national titleholder in an early '80s board up against a world or national champ H16?

Zed, Big Bandicoot may have planed, but it never reached the speed record it aimed at.

Cats may be able to plane, but the point is that you can plane but be slower than something that doesn't plane but has less form resistance, wetted surface resistance etc.

[Doug Lord]

Parliers 60' planing cat held the world 24hr speed record-both crewed and single-handed-in 2006 for a few months....http://www.sailspeedrecords.com/24-hour-distance.html
Another planing multihull holds these records:
2008 Macquarie Innovation Simon McKeon AUS Sandy Point, AUS 48.14 kts
2009 Macquarie Innovation Simon McKeon AUS Sandy Point, AUS 50.07 kts

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Again, best recorded(that I can find 1977-1982) Hobie 16 speed 16.8 knots:
Speeds credited to "windsurfers" in WSSRC:
1981 Erica Keller 21.00 knots
1982 Jenna de Rosnay 23.67 knots
1977 Derk Thys 19.10 knots
1980 Jaap van der Root 24.63
1981 Jurgen Honsheid 24.75
1982 Philip Pudenz 26.5 knots
1982 Pascal Maka 27.8 knots

[Munter]

As has been pointed out, those records were set on windsurfers very different to the plastic rotomoulded craft your cat seems to be comprised of. I introduced the comparison to a single sailboard as a valid way of questioning how an even slower craft could keep up with a 16 and you gone and plucked some unrelated numbers.
Bah. It doesn't really matter. Your fantasy world is impenetrable by logic and reason.

[CT 249]

Doug

You are always quoting formulae. Why not work out the numbers for a 2.28m by 50cm (approx) windsurfer weighing 5kg and sailing in 30 knots or s0 (like those speeds you are quoting), and compare it to the numbers for a Kona Kat or other early '80s longboard in 10-12 knots?

The numbers are completely different and the performance is completely different.

The fact thar Parlier's cat held the world record for a short time may not mean a lot in terms of all-round performance, in just the same way that VO 70s have beaten the CBTF boats for 24 hours records yet normally go slower than the CBTF supermaxis. And even if a planing cat can have better record-setting performance that does not mean that (1) it's a 'better' design and (2) those who preferred a displacement cat for its superior all-round performance were ignorant when they rejected the planing Itza Cat.

Finally, Macquarie Innovation was SPECIFICALLY designed to have short, fat planing surfaces rather than cat-style hulls (to quote the website 'the width of the planing surface (1.2m) designed to ensure the most efficient planing aspect ratio possible') and therefore this tri/proa/whatever demonstrates that a short, fat surface is quicker than a long skinny one in terms of top speed. It is simply more evidence that a skinny hull is not a very good planing surface and (as years of experience proves) you lose more overall speed than you gain if you try to make a long skinny cat hull into a flat planing hull.

[Doug Lord]

Originally Posted by Munter

As has been pointed out, those records were set on windsurfers very different to the plastic rotomoulded craft your cat seems to be comprised of. I introduced the comparison to a single sailboard as a valid way of questioning how an even slower craft could keep up with a 16 and you gone and plucked some unrelated numbers.
Bah. It doesn't really matter. Your fantasy world is impenetrable by logic and reason.

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You made unsubstantiated comments about my Kona Kat and asked how could it be faster (on a reach ,in smooth water) than a Hobie 16 assuming a windsurfer of the era couldn't beat a 16. I did some research and found a B Class top speed at Portland UK for a Hobie 16 of 16 knots. I then looked at the published records of the era for Windsurfers and found that ,at that level, they were on average 1.5 times faster than a Hobie 16.
And you say this to me??!!

[CT 249]

Yes, Doug, because the speed of a 5kg sinker in 30+ knots of breeze is no indication of the speed of a very heavy longboard (like a Kona, One Design, Pan Am etc) in 10-12 knots of breeze.

That's a pretty simple, and very valid, point.

[Doug Lord]

Originally Posted by CT 249

Doug

You are always quoting formulae. Why not work out the numbers for a 2.28m by 50cm (approx) windsurfer weighing 5kg and sailing in 30 knots or s0 (like those speeds you are quoting), and compare it to the numbers for a Kona Kat or other early '80s longboard in 10-12 knots?

The numbers are completely different and the performance is completely different.

The fact thar Parlier's cat held the world record for a short time may not mean a lot in terms of all-round performance, in just the same way that VO 70s have beaten the CBTF boats for 24 hours records yet normally go slower than the CBTF supermaxis. And even if a planing cat can have better record-setting performance that does not mean that (1) it's a 'better' design and (2) those who preferred a displacement cat for its superior all-round performance were ignorant when they rejected the planing Itza Cat.
Finally, Macquarie Innovation was SPECIFICALLY designed to have short, fat planing surfaces rather than cat-style hulls (to quote the website 'the width of the planing surface (1.2m) designed to ensure the most efficient planing aspect ratio possible') and therefore this tri/proa/whatever demonstrates that a short, fat surface is quicker than a long skinny one in terms of top speed. It is simply more evidence that a skinny hull is not the best planing surface.

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Ct, I didn't say that-in fact I rejected what the itza cat guy actually said-which you continually misquote!
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I think it is evidence that a planing multihull can be very, very fast.

[Zed]

I can't find one pic of 'Big Bandicoot', there is supposed to be a video of the whole episode called "A Dream to Sail Faster Than the Wind" . I just remember her hanging around the local yacht club. I guessed that nothing came of her but I would have loved to seen her go. The vid was on fleabay once apparently.

[CT 249]

Yes, Doug, I respect you for rejecting what the guy said. I was referring not just to his remarks, but to the fact that we've seen the same attitude (that the world was stupid for not going for planing cats) from numerous other people.

If someone wants a planing cat, great; all I'm saying is that its proponents tend to be derogatory of the boats that other people sail and that's not good.

[Zed]

It is a bit obvious really, you need to create a degree of resistance in order to plane (in a traditional planing hull), so at what point does the benefit of planing overcome the penalty of the resistance. In most average conditions around a course it would have to be to the advantage of a lower resistance craft.

I know it is a can of worms but I still really don't understand why a normal cat hull is not considered to plane. To my simple way of thinking if a hull when moving is displacing less water than when stationary it is to some degree or another riding on the water and therefor planing. So its a matter of the % of water displaced 100% being near unachievable and a lower % being easily achievable. To me my old cat looks for all the world to be planing in the low teens and I bet that at that speed it displaces a lot less water than at rest, but then that is just my perception. Has it ever been measured?

[Doug Lord]

Originally Posted by Zed

It is a bit obvious really, you need to create a degree of resistance in order to plane (in a traditional planing hull), so at what point does the benefit of planing overcome the penalty of the resistance. In most average conditions around a course it would have to be to the advantage of a lower resistance craft.

I know it is a can of worms but I still really don't understand why a normal cat hull is not considered to plane. To my simple way of thinking if a hull when moving is displacing less water than when stationary it is to some degree or another riding on the water and therefor planing. So its a matter of the % of water displaced 100% being near unachievable and a lower % being easily achievable. To me my old cat looks for all the world to be planing in the low teens and I bet that at that speed it displaces a lot less water than at rest, but then that is just my perception. Has it ever been measured?

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A "normal" cat hull- the F16 Blade(with single crew) does plane-I've seen it up close-no question about it. I've talked to Matt McDonald(developer of the US made Blade and Falcon) about it as well. And there is another thing: old Moths with 10/1 L/B ratios planed but started at a higher speed than they would have with a more efficient planing surface-perhaps they-and the Blade(L/B=16/1) are examples of hulls that have the advantages of skinny "displacement" hulls and "planing" hulls with benefits accruing according to the speed of the hull?
And there is another beachcat-European- that uses(or used) a step on a high L/B hull-name escapes me for now.

[CT 249]

Zed, as far as I can find out from naval architects and books, the point is that as soon as a boat starts making bow and stern waves, the hull squats lower between them (albiet in an almost unnoticeable manner for a cat). The conventional definition (as I understand it) is that a boat is considered to be 'planing' only when the lift created by dynamic (planing) forces is enough to compensate for the squatting effect and therefore lift the boat's c of g higher than it is when the boat is stationary. And of course, afaik unless you get the right angle of attack to the planing surface you won't get dynamic lift, and how often does that occur on a significant portion of flat hull on a conventional cat????

I'm no expert, of course, and how you work out whether it's happening is another matter altogether! But it would indicate that although cats make dynamic lift, many of them don't "plane", because the dynamic lift isn't enough to raise the c of g sufficiently to compensate for the wavemaking squat.

Which cats planing happens in is a moot point, afaik. Martin Fischer (cat designer and PhD in fluid dynamics) seems to reckon that only a small minority of cats plane, although I can't recall his exact words. As we all know, the terms are very loose - what I'd call a 'planing cat' is a boat with beamy, flat bottomed hulls like Bandicoot or an Itzacat. It's like the way the 12 Foot Skiff designers call a modern 12 a "displacement hull' as a way to contrast it to something like an old Murray 'planing shape' 12.

As Doug says, some of the recent cats (ie Fischer's Capricorn F18, maybe the Blade etc) are capable of planing, but they are a very different in style and operation to the flat Bandicoot/Itzacat hulls. And while the Cap and Blade are great boats, they don't massacre the older Taipan/Tiger/Tornado/Mossie types around the courses all the time, so is there a massive difference in what's happening to the hull??? It would be interesting to hear opinions.


It's such a blurred continuum between planing and non-planing, where do we draw the line? The more craft we look at, the harder it gets - at one extreme, there are some guys who say longboard windsurfers don't plane, which is odd considering they can do 30 knots plus and have enough lift to do forward rolls off chop!

So many ideas to throw around, so few answers!

[Zed]

Well my money is definitely on the long board windsurfers planning, having sailed hifly races etc you can plane through a gybe on those things, for sure and you know when you don't get it right and fall off the plane. Been along time but I remember that much!

As for my old warhorse of a SW24, I won't argue that one, it is as you say probably more a matter of definitions and at what point you say what is occurring and why.

The newer sport boats are interesting in that regard, they just seem to slide up onto the plane with little or no noticeable 'hump climb', more like the seamless acceleration of a cat IMO but they are definitely planing (please don't burst my bubble on that one! LOL)... so should planing cats more reflect the shapes (beam/length ratios accepted) of the sports boats and refined skiffs like the NS14's. I must go look at a Blade hull!

[Zed]

I googled some pic's. If I have it right the Blade looks very derivative of a new A Class.