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  #16  
Old 02-19-2013, 11:24 PM
upchurchmr upchurchmr is offline
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Thanks for the input Gonzo, that was useful.
Sweating makes you wet too.
Here in Texas hot weather generally means slower winds, so it wouldn't help.
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  #17  
Old 02-20-2013, 09:12 AM
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Doug Lord Doug Lord is offline
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Quote:
Originally Posted by upchurchmr View Post
Doug, thats a typical feel good statement.
What I would like it to hear some actual facts rather than gushing about the latest fad.

I did not say anything about the "looks" because that is immaterial to me. People can get use to anything that works better.

If the bows are actually extended on the waterline, that will provide more righting moment for preventing nose diving.
If the bows are actually no different in providing the pitching resistance then they should not help until you would submerge the "normal" deck and get an increased force stopping the boat.

So what is actually designed into such a boat?
All I want to know is what is intended by the designer and how does it compare to an older typical boat - a Tornado catamaran just as an example. For instance the Tornado has the mast placed mid length.
The illustration of the Trikala seems to show the mast much farther back, which by itself will provide more pitchpole resistance, no matter if you have a Tornado or a reversed bow.

Just a few facts.

Oracle 17 showed that reversed bows by themselves don't prevent a pitchpole, although I believe the reduced width deck gave them much gentler and slower crash, giving them more chance to recover. I will be the first to agree that not all things were equal for Oracle so that is not a good comparison.
========================
No, it's not-it sums up what I've read by A Class sailors on the subject. The reverse bow type of hull in the A class has buoyancy lower than a normal hull and is known for it's wave penetrating ability. In other words, it appears to reduce pitching and reduces the "stopping effect" of waves better than a normal bow/hull shape. And, in the A Class the bow is definitely tied into a shape with its buoyancy closer to the waterline than to the deck.
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  #18  
Old 02-20-2013, 10:01 AM
cavalier mk2 cavalier mk2 is offline
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I ponder whether each type of bow has a effective wave size range. Penetrating waves can help with chop but in some cases going up and over might be safer than digging in deep.
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  #19  
Old 02-20-2013, 11:17 AM
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Richard Woods Richard Woods is offline
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I hope a Trikala gets sailing soon in the PNW as it will be fun to race against it in my similar Strike 18 trimaran, and of course against the Hughes 15 Gonzo, never mind Osprey and the Tremolinos.

The A cat is such a specialised boat I don't think you can generalise too much and say "if its good for an A class its good for other boats"

Certainly, having a wet boat is not popular amongst cruisers.

And when I make mistakes docking my boat it tends to be the bow that hits first and I need to fend off. Which I cannot do with a reverse bow. I have often had times when I've been anchored in light winds and when the tide changed have had the anchor line catch round the stem. Obviously with a ram bow the warp will not release itself under the hull but rather ride up to deck level. At the very least this will be noisy and disconcerting, especially if you are asleep at the time

For that is another difference between a day racing boat like an A cat and larger boats. The A cat is definitely a money-no-object, the-only-thing-that-is-important-is-speed, boat, whereas boats with accommodation have other, maybe even more important, requirements.

As always, I have more about it on my website

Richard Woods of Woods Designs

www.sailingcatamarans.com
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  #20  
Old 02-20-2013, 01:09 PM
Number4 Number4 is offline
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Please excuse my ignorance, but I have a few simple questions about this boat.

1. How much would it cost to build a Trikala 19? I see the plans are US$ 500.
2. How long would it take a ham fisted idiot to build one?
3. How much would you expect the complete boats made in Asia to sell for?

Thankyou kindly.
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  #21  
Old 02-20-2013, 01:34 PM
warwick warwick is offline
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Slightly off topic a new catamaran by long island yachts, what I find interesting is the bow profile. Would it have more volume low down?
May be a better comprimise?
Attached Thumbnails
Kurt Hughes updated Trikala 19 trimaran-long-island-yachts-85.jpg  
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  #22  
Old 02-20-2013, 05:57 PM
upchurchmr upchurchmr is offline
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Doug,

So if I carried a full shape at the waterline, vertical bow, and a rounded deck (ala Nacra) would I get the same effect as the A class reversed bow?

OBTW, is an A class longer from bow to mast than mast to stern?
Lock Crowther was a great proponent of the mast positioned further aft. Was he basically getting pitchpole resistance similar to an A-cat?

I'm willing to understand reduced pitching in a specific sea state (wave height), but in bigger waves I'm not sure I wouldn't want more upper boyancy to lift the bow and avoid a pitchpole. Richards comment about being designed for absolute speed goes hand in hand with typical racing being done in limited conditions (not always since there plenty of crazies in the world - and extreme conditions are fun if you are fit).

Richard, I'll re-read your comments - soon, I promise.
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  #23  
Old 02-20-2013, 06:08 PM
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Quote:
Originally Posted by upchurchmr View Post
Doug,

So if I carried a full shape at the waterline, vertical bow, and a rounded deck (ala Nacra) would I get the same effect as the A class reversed bow?
OBTW, is an A class longer from bow to mast than mast to stern?
Lock Crowther was a great proponent of the mast positioned further aft. Was he basically getting pitchpole resistance similar to an A-cat?

I'm willing to understand reduced pitching in a specific sea state (wave height), but in bigger waves I'm not sure I wouldn't want more upper boyancy to lift the bow and avoid a pitchpole. Richards comment about being designed for absolute speed goes hand in hand with typical racing being done in limited conditions (not always since there plenty of crazies in the world - and extreme conditions are fun if you are fit).

Richard, I'll re-read your comments - soon, I promise.
----------------
I doubt it......I don't know anything about an A Class having a "full shape at the waterline" ? Do you mean "full section shape at the waterline"? This is not semantics -it's important. The section would be widest right about at the waterline as I understand it-the waterline would be relatively narrow especially on hulls designed to use lifting foils. It would be difficult, probably, to not use a reverse bow with this kind of hull shape.
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  #24  
Old 02-20-2013, 06:27 PM
upchurchmr upchurchmr is offline
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Doug,

You said "The reverse bow type of hull in the A class has buoyancy lower than a normal hull "
I thought that would be the same as "a full shape at the waterline".

So now you are saying the shape is widest at the waterline, but narrower than compared to a "normal" shape?

If the bow is the same length, and narrower at the waterline and narrower higher, how do you get pitchpole resistance? Or do they just quit pushing the boat when they are reaching due to pitchpole limits?
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  #25  
Old 02-20-2013, 06:39 PM
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Quote:
Originally Posted by upchurchmr View Post
Doug,

You said "The reverse bow type of hull in the A class has buoyancy lower than a normal hull "
I thought that would be the same as "a full shape at the waterline".

So now you are saying the shape is widest at the waterline, but narrower than compared to a "normal" shape?

If the bow is the same length, and narrower at the waterline and narrower higher, how do you get pitchpole resistance? Or do they just quit pushing the boat when they are reaching due to pitchpole limits?
====================
Note that I said " relatively narrow especially on hulls designed to use lifting foils"- which is true of most new A Class boats. The trend now is also to incorporate rudder foils as well-which aid pitch stability.
From catsailingnews about the cat in the picture below. Note that at the front beam the hull section is wider lower down than it is at the top:

"The hull is a wave piercer, with a cutaway bow for minimum friction and wave drag. Also known as a upside down design. The hull is an evolution of the Flyer 1 (the mother of all modern designs) and the Nikita (the first succesful design with curved boards). With slightly more volume the boat is optimized for 80+ kg sailors, who can push the boat harder than ever before.
The curved boards increase downwind speeds tremendously and simplify handeling, while the boards stay down downwind."


click---
Attached Thumbnails
Kurt Hughes updated Trikala 19 trimaran-cat-dna-classcad.jpg  
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  #26  
Old 02-20-2013, 08:41 PM
upchurchmr upchurchmr is offline
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Just can't quit changing the subject to lifting foils can you.
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  #27  
Old 02-20-2013, 08:45 PM
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Originally Posted by upchurchmr View Post
Just can't quit changing the subject to lifting foils can you.
------------------------
Do you really not get it? Thats a major design factor for why the A class hulls are shaped the way they are and why so many succesful A Class cats have reversed bows!
So many reversed bows are just following fashion but you wanted technical reasons and the A Class provides that......
You also asked "how do you get pitchpole resistance?" and I answered. Amazing.......
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  #28  
Old 02-20-2013, 09:22 PM
upchurchmr upchurchmr is offline
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Actually the subject was Trikala and reversed bows.
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  #29  
Old 02-20-2013, 10:11 PM
warwick warwick is offline
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Would the reverse raked bows be more about weight loss.

The float bows from what I understand are wave penetrating derived from the A class cats.

Would it be how you interpret overall length? With a reverse bow you could have longer boat or shorter one depending your point of view, taken from the water line or deck.
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  #30  
Old 02-20-2013, 10:14 PM
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Originally Posted by upchurchmr View Post
Actually the subject was Trikala and reversed bows.
--------------------
You should reread your posts 14,16,22 and 24-all of which asked questions which I then tried to answer in detail-and I was off topic??!!
Like I said before Amazing!
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