Wave Piercing Bows

[groper]

Ah yes, but CatBuilders multihull will be quite fast, and hes gone to some effort to ensure it sails reasonably fast, so is it a cruiser or a racer?

Most modern multis, or any yacht type really, are much faster than they used to be thanks to improved design and materials... majority of people want to go faster, with less fuel, and this type of styling eludes to this fact and appeals to their desires...

A common misconception about reserve buoyancy and these bow shapes, buoyancy is not necessarily reduced with a reverse bow... i think this comes from the idea that the top of the bow is chopped off, rather than the bottom is EXTENDED... in the second instance, you have more buoyancy than an overhanging bow dont you :idea:

USN latest destroyer - which will have a service life of at least 25years and will be visible in ports around the world for a similar duration...

 

[Doug Lord]

Reverse bows and other speed producing elements

I dont think this will be a blip, why? Because many things, such as cars, boats, sporting equipment, yada yada take their aesthetic design clues from racing, or sporting elite successes etc... what do most of teh cars on the road look like today? more like race cars than vintage collectors items no? And theres actually good reason too, like windage or in automobile parlance, fuel efficiency etc...

so because the reverse bow does have a small function in racing, primarily to reduce windage and pitching, these race boats will continue to use the best bow shape they can in order to keep winning races. This means this bow shape is here to stay until they find a faster shape. This also means, based on past trends of many industries and the link to racing, that this bow shape will remain aesthetically desirable for a similar duration...

So i dont think this one is a fad... it will be a desirable feature of many modern yachts that want the "go fast" look...

=================
I think you hit the nail on the head-great post. I think with sailing multihulls-especially racing boats- using lifting foils to a greater extent all the time every little detail on the hulls will be modified for less weight, better aerodynamics, lower wetted surface and higher L/B ratio's. The foils take care of keeping the hull(s) up and back up the "wave piercing" bows in pitch reduction.
Exciting times in performance sailboat design. Oh, did I mention I really like the looks of a reverse bow...........

 

[Petros]

I dont think this will be a blip, why? Because many things, such as cars, boats, sporting equipment, yada yada take their aesthetic design clues from racing, or sporting elite successes etc... what do most of teh cars on the road look like today? more like race cars than vintage collectors items no?

I think you are wrong here; how would you explain the popularity of the PT Cruiser and the new bug? both look like their older counterpart. But besides that we as consumers expect to see improvements in cars every year (and part of the marketing of new cars is that they are better than last year). For most Americans, cars are a necessary expense, necessary to get around, to school and work, and we love the independence it gives us even if we have public transportation too. Pure utilitarian cars do not sell well, people want and expect improvements with each new car they purchase. Comfortable, safe and reliable. Modern cars require much less maintenance and are generally longer lasting than they were 30 years ago.

No one needs to own a sailboat, they are either sport or recreation. Most classes restrict to a single design, which can be quiet old. Most people who buy sailboats want them to look like all of the others, that is why mono-hull designs dominate the recreational sailboat market. There have been a number of attempts to sell modern wing masts for recreational sailing, none have done well. And I would expect that anyone that would charter a sailboat are not doing it because they want to see the latest and greatest sailboat design in action, they go for recreation, and to experience "traditional" sailing. Granted those that want to charter a large catamaran are likely a different type of customer than your typical sailing charter customer. But it will be hard to characterize a "typical" customer, and to claim they would like to see the most modern design as possible. The most modern design of boats would not have sails at all, sails are obsolete as a means of transportation, except as recreation or sport.

 

[idkfa]

Doug posted a link to a SA interview with Marstrom on the new M32, and they think will be a fad, for it is flawed design including more spray; see the last few minutes.

 

[CatBuilder]

Fascinating discussion. To me, the PT Cruiser and bug are nostalgia cars built for older people. Also, my wife and I have owned a Hyundai Accent and Honda Civic (but also a Mini Cooper because of the features, not styling). All utility car purchases. Maybe there is also a generation gap here to explore with the bows?

I just turned (yikes!) 40. My wife is 32. She likes the reverse bow lines, I like the plumb. I wonder if there are different tastes in bows at different ages?

 

[groper]

Bwahaha, the PT cruiser and new BUG would make up about 1% of new car sales here in Australia, certainly not POPULAR??? How do you base an argument on that?

This is the #1 selling car in australia for the last 15years, the base model and top of the line model shown;

The trend on this car and same for most cars, is lower to the ground, lower profile tyres, alloy wheels and spoilers are almost a standard feature now, even the air vents in the front 1/4 panels are standard... they all contribute to efficiency born from teh race cars but are driven by fashion in the consumer market - people want what the pros are driving etc.

Good call on the age thing CB, im 31years old, probably on the younger side of people posting here and like the look (regardless of function) of the reverse bow... i think in general, that most younger people will like modern designs, whereas the 'oldies' are more likely to go for the designs of their respective generation...

 

[Doug Lord]

Reverse Bows

Heres the link again- http://www.youtube.com/watch?v=4bzhaRhWfys They talk about bows at about 26 minutes in....
I disagree with their assesment. They point to AC 45's but A class cats have even more radical reverse bows that are universaly hailed as working well. Not only that, but the A Class cats use that type of bow with foil assist and that is not an accident. AC 45's don't use lifting foils to any appreciable degree and they are narrow for their length-that's why they tend to pitchpole so frequently. Its been proven time and again that lifting foils reduce the incidence of pitch pole-no ifs ands or buts. And thats regardless of the bow type. On A Class cats, Nacra 20's etc the bow works with lifting foils as a natural progression of design refinement, weight reduction, pitch control in waves etc.
Oh yeah, they look good too.

 

[groper]

HAHA! i just found out that the PT cruiser was so successful- they dont even sell it anymore in Australia!!! i cant even find the sales figures for the new beetle, must be insignificant...

 

[DCockey]

......

The trend on this car and same for most cars, is lower to the ground, lower profile tyres, alloy wheels and spoilers are almost a standard feature now, even the air vents in the front 1/4 panels are standard... they all contribute to efficiency born from teh race cars but are driven by fashion in the consumer market - people want what the pros are driving etc.

......

Reality and perception don't always agree.

Some alloy wheels on road cars actually weigh more than an optimized steel wheel due to the design chosen for asthetic reasons. Wide, low profile tires can be higher rolling resistance. Check to see if the air vents are actually functional, and even if they are they may not contribute anything. "Spoilers" can actually increase drag; some do, some don't.

Much car design is fashion driven. Some folks want a car which shouts "look at me" and some want a car which blends into the background. Even the "look at me" folks have different tastes. Some want super-slick while others want rugged.

 

[Petros]

The PT cruiser is unfortunately not a very reliable car, they are popular here in the USA I think only because of nostalgia, certainly not because they are a good car (perhaps car buyers down under are much better judges of car quality than in the USA). But the new Mini (that I call a "maxi-cooper" because it is not really very "mini" compared to the original), the bug, the mustang, the Miata, and a number of other cars are popular because they have "classic" lines (the miata is actually a pretty good quality car compared to the others I think, my 19 year old daughter loves them).

I am 53 and like the revers bows on cats, but I also like the looks of the miata, but also the more "modern" look of the MR2.

As far as building the cat for the sake of attracting clients, that just depends on who you think your target market is in terms of demographics. I thought it would be kind of fun to build a small fleet of replica Greek trade vessels with nice accomodations, and sail people around the Mediterranean on a "sailing" pilgrimage to all of the ports of call of St. Paul did according to the book of Acts. There are many people that pay big money for religious tours of the holy land, and even a few cruise ships that follow the sea routes. But my idea was to give than a sailing tour in a modern remake of a "look-a-like" Ancient Greek trade vessel (but with much nicer accommodations below deck of course). My "target" market would be people who want to experience the trip as much as practical as St. Paul did (minus the ship wrecks of course!). But the "look" of such a charter vessel is the whole draw of this type of customer. My adult daughter and I think we can make a bundle on such a venture, but we would need big $ investors to pull it off.

CatBuilder, you have to decide how much the look of your charter boat might influence your target market. Consider your cat is a relatively modern design, it may not make much difference, so I would do what is lest costly and the most expedient. But you have to decide if it would be worth it. You can not look at it from your likes or dislikes, but what your customers might like or not (or if they would even care!).

I am not sure if the people on this forum are representative those who pay for high priced boat charters. I likely could never afford to be one of your customers, so my personal likes or dislikes are irrelevant (as I suspect most on this forum).

If it would not make much differance to your potential customers, than do what you want (since you are planning it to be a profitable buisness, I would do what is least costly). But if your customers would influenced by the design of the bow, you need to do what they want, not what we think.

 

[Leo Lazauskas]

"Spoilers" can actually increase drag; some do, some don't.

I was under the impression that spoilers were only beneficial at speeds
greater than about 160 kph. Below that they provide little down force and
are just another source of drag.
Then again, the taxis I use don't have them, so what would I know!

 

[DCockey]

I was under the impression that spoilers were only beneficial at speeds
greater than about 160 kph. Below that they provide little down force and
are just another source of drag.
Then again, the taxis I use don't have them, so what would I know!

What's magical about 160 kph? Do wings only start to produce lift above a certain speed?

 

[groper]

indeed, the spoilers remark was to point out the fashion thing, same for the wheels, tyres, air vents etc... the lower ground clearance is a safety and fuel efficiency thing however... and the whole package is meant to look more like the cars the pros drive on the race track... its a status and style driven market, with some clues from the race cars - which is directly related to this reverse bow thing on boats and taking the clues from the racing boats... most boats would not even feel the difference in performance between either bow shape, theres far bigger driving forces at play, so the choice becomes more about whats fashionable, stylish and i would hope a large portion of the choice would be about its ultimate resale value because of how well it ages in the future marketplace...

The difference between FAD or FUTURE, could mean a difference of $100,000... get it right you win, get it wrong you loose, taking the risk is playing the game...

 

[Corley]

indeed, the spoilers remark was to point out the fashion thing, same for the wheels, tyres, air vents etc... the lower ground clearance is a safety and fuel efficiency thing however... and the whole package is meant to look more like the cars the pros drive on the race track... its a status and style driven market, with some clues from the race cars - which is directly related to this reverse bow thing on boats... most boats would not even feel the difference in performance between either bow shape, theres far bigger driving forces at play, so the choice becomes more about whats fashionable, stylish and i would hope a large portion of the choice would be about its ultimate resale value because of how well it ages in the future marketplace...

The difference between FAD or FUTURE, could mean a difference of $100,000... get it right you win, get it wrong you loose, taking the risk is playing the game...

I'm not sure I agree in this case. We are talking about a foam block on the front of the boat and how it's shaped. Hydrodynamically there is a small advantage and there is a minor stylistic improvement to some (me included). If there was $100,000 in it you would get in there and glue on a new foam block when the boat was coming up for sale and splash some paint around.

By the way the Holden Commodore was not the best selling car in 2011 it was displaced by the Mazda 3 hardly a racecar package but a neat enough little car. The biggest selling car brand in Australia was Toyota by a large margin.

http://www.fleetcare.com.au/go/blog/top-selling-cars-of-2011

 

[Leo Lazauskas]

What's magical about 160 kph? Do wings only start to produce lift above a certain speed?

No, it was just based some calculations of lift and drag I did many years ago
using experimental airfoil data over a fairly wide range of Reynolds numbers.
At low Rn the lift to drag ratios are poor, so speed is an important factor.

On the topic of bow shapes...
Isn't it a mistake to focus on the bow shape in isolation, i.e. without
reference to the other parts of the hull geometry when talking about
resistance or sea-keeping and not aesthetics?