Planing Catamaran!

Doug, I specifically referenced a windsurfer one design which, to my eye, reasonably represents one half of a kona cat. From there you went on to qoute speeds of completely different sailboards. Do you not understand that these are different craft? It makes your comparison irrelevant. Do you not understand that or are you deliberately ignoring that problem.

While I admire your tenacity I find your logic incomprehensible.

 

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Well, at least we agree about each others logic.......

 

Munter's point is pretty fair, Doug.

For about the third time - the boards you quoted weighed as little as 5kg and sailed in winds of 30 knots or more. The speeds they achieve have nothing in common with a heavy longboard in 10-12 knots.

Maka's 1982 mark of 27.8 knots, for example, was set in gust of up to 40 knots, using a 6.2m sail on a board of about 6'6" by 14". Such a board would weigh about 7kg, compared to 21kg of a normal longboard of the time.

Maka's time was set using 11 times the wind force to drive something 1/4 the weight of a typical longboard of the time. Add in the fact that induced drag drops by the square and it's obvious to anyone that we are dealing with completely different areas of sailing performance.

You're the numbers man - how in the world can you ignore the distortion in trying to draw lessons from boards, when the power/weight ratios (ie power of the wind / weight) alone are so different.

The speed boards whose records you quoted are completely different beasts in action, sailing in completely different conditions with 11 times the power.

 

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I disagree.

 

Sorry Doug, you're the ratios man - do you disagree that Munter is wrong, when he points out that you can't use support your claim that an early '80s longboard can beat a H16 by talking about record speeds that were gained in 11 times the wind force, driving something 25% the weight?

You're into ratios - do you really think that a 20+ kg board in 10-12 knots is comparable in performance to a board 25% of the weight, driven by 11 times the wind force? Having sailed those boards to national and world level, and having raced against top H16 sailors, I may as well say that a H16 is much faster than a comparably-sailed early '80s longboard in 10-12 knots.

PS - merely saying that you disagree, rather than producing a reasoned argument, is hardly convincing.

 

I saw numerous windsurfers beat Hobie 16's during the time period in question. Thats a fact, not conjecture.

 

Planing Cat

From Rad Samui in Thailand( on SA):
http://forums.sailinganarchy.com/index.php?showtopic=103327&st=0&#entry2712376

"Based on our experience on sailing the Radical Bay 8000's we built and raced we know that pretty much the boat sails flat with this rig. When a gust hits the boat just accelerates as opposed to heeling. On the RB's our calcs (and confirmed by one of the mast makers) estimated that with full sails up it would take 28knots of wind to approach flying a hull. Strongest sustained we sailed in was around 22-23+ and she was still flat and never felt like she was close to lifting. So our idea was that if the attitude of this rig set up is to sail flat then design the hull form around flat = planing. On the other hand Arnie[Happy Feet] over in Phuket has gone with foils on his bi-plane cat to 'induce' flying a hull and therefore reduce drag. We're trying the opposite and hoping to generate lift off the planing pads and reduce drag that route.

Yes, off the wind with a kite is looking like it could be fun and fast - the main reason we switched from free standing to stayed on the BP set up this time around.

I guess we'll find out soon enough if the theory works. "
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His comments about "Happy Feet" are interesting because these two boats couldn't be more different. Happy Feet uses a bi-foiler hydrofoil arrangement with a module containing both the main foil and rudder foil that slides to leeward. Its going to be interesting to see how these two boats work out as they get sorted....

 

Planing Cat

Here is a picture of a test boat used in development of Parliers 60' planing cat:

60 footer and test boat-

 

Hi Doug- wow thats a beauty!! i have been watching parliers boats for a while and in fact felt saddened since i thought maybe i had an original idea...sigh....
but i do love the planing hulls on the smaller boat. If i increased the beam of each hull to around 3.5 ft , used parallel rigs and had flat bottoms that came to an sharp upswept bow with a step a little farther back than on the parlier vessel...i figure it would still be ok in lighter airs...and fly in heavy! i was thinking if i used 3/8ths ply and stitch and glued it, then epoxied one layer inside and out for a composite hull...secondly- instead of a trampoline, i would put a large light wing section between the hulls in an attempt to generate lift kinda like a big airplane wing coupled to the hulls...thus giving easier planing speeds at lighter airs? i am hoping it wouldn't generate too much lift and reverse pitchpole it to windward.


anyway keep in mind, as it stands now its JUST an idea....
i will have to make a drawing for you this week and scan it in..it'll be very rough but maybe itll give you an idea of my design idea..ill post it here...thanks again

Doug W.

"hard dreams die harder"

 

It would be great to see your sketches!

 

Hi,
Doug asked me to post on this in reference to my cat, see pic below, although at the stern it looks like maybe flat enough to be a planing hull, at the bow and midship sections its actually a fairly deep V although nothing as extreme as a wharram. I don't believe its a planing cat.

PS if anyone knows what type of cat this boat is, please let me know.

 

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Thanks Captain-any word on the performance of your boat? You might PM Gary Baigent-he might be able to help you.

 

I haven't had much opportunity to really speed test it, solo sailed it most of last summer, until I capsized it in bad weather gusts of about 40 knots
I've been rebuilding it since.
The highest speed I recorded with my GPS was 16 knots on that same day. But like I said, I haven't had a chance to run it in the right weather with a good crew to really check its performance. Or to sail against any other catamarans.
All I know is its a lot faster than my Caledonia Yawl I built 15 years ago

 

Planing or not, you gotta love the tilting wing rig. Isn't that also known as the FlipTacker? How long before we see on one an AC boat?

 

Not quite what you were after, probably, but here's a picture of Big Bandicoot in 2008, while it was on the hard in Mackay. http://members.optusnet.com.au/owlrigh/bb01.jpg

It's currently on the hard in Darwin. My dad owns her now, and she's something of ... a white elephant. He's got the video and shows it to anyone who'll sit down long enough!