Wave Piercing Bows

[sabsfeigler]

sink or float

For submerged bodies, far enough below the surface so that wave making isn't significant, shape of the forebody doesn't significantly affect drag as long as flow over the forebody is attached.

It's no use to look at submarine animals when designing a floating boat. A whale or barracuda, or sailfish don't have to break the surface tension of the water like a boat's nose does, therefore I present to you, the Black Skimmer, nature's own reverse bow. Now THAT'S biomimicry.

There's also a great website called Asknature.org (I think) where any biomimicry questions researched.

 

[CatBuilder]

Also, it is important to distinguish between "waves" as we all tend to get lazy and call anything, and chop.

You want a boat to ride up over waves, but not so much over chop.

This is probably why the new bows are faster. Multihull momentum is quickly sapped when going up and down quickly in chop - there is less inertia to overcome that situation on a multihull. So, going through chop (and of course, over waves) would give q performance advantage.

 

[CatBuilder]

There you go then. Another marketing thing to consider is the customer base. It takes awhile to build a boat so the more affluent mature crowd may be a better market than the young money who might not want "Pops" as a skipper.

I tend to disagree. Our charter customers are people who only want the best. A "b" catamaran style will be passed over for the best one (latest and coolest) every time. Old boats don't attract charter guests, unless that is you entire angle. Think pirate ships or classic wooden boats. New boats attract charter guests.

Also, the average age of my guests seems to be about 45. We has several in their early 20's, a load of housewives from Jersey, Europeans on their 50's with sons living in nyc that were in their 20's, professional athletes, a cop and his wife, hedge fund manager in his mid 30's, etc.

To think that old people are the only successful people is seriously incorrect.

I have sold out every year. I certainly don't need marketing lessons. Why do you think I can afford this build and work full time at it with an employee? Because I don't understand my market? Ha ha ha

Oh, wait... Just read your post again... Are you calling me pops?? Ha ha ha. I just turned 40 and my wife is 32. You're cracking me up!

 

[Richard Woods]

So what do you guys think of this bow?? It's hardly modern, as it was built in 1891, and was still in use last week when I took the photo

I watched the AC races on youtube in Lisbon, Plymouth and San Diego. (I was in S California when the races were in Plymouth, and in Plymouth when they were in San Diego!) So I haven't seen them yet in the flesh

But it was obvious that the crews were really struggling to begin with, although they slowly improved. There is no substitute for racing a boat, just going out practising is never the same.

Those who hadn't sailed multihulls much before clearly didn't realise the potential for pitchpoling that occurs when you bear off hard. For it seems that most of the capsizes occurred when rounding the windward mark and bearing off.

So maybe the problem isn't the bow or even the hull shape but rather that it is too difficult/slow to dump the mainsail and then sheet in again.

And as I have written before, racing boats only need sail fast, cruising boats have equally important criteria to incorporate, like coming alongside, anchoring, having a dry, comfortable deck area etc

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

[mydauphin]

All these new bows are actually circa 1900's checkout the Titanic's bow and like the PT cruiser the style will pass.

 

[CatBuilder]

Very true Mydauphin. All styles will pass. The plumb bow I love so much has recently passed and the traditional bow passed several years before that. Style wise, I guess it's time for me to resist the inertia of getting older and move on from those plumb bows I like. Reverse bows it is.

 

[mydauphin]

I have noticed in those reverse bows that the entry point is not touching water, so they don't dig in right away. Check out the Wally boats

 

[catsketcher]

Bows are made by hull shape

Just got on this thread but a few points

Bows are shaped by hull side flare. Wharrams with fared hull sides will always have traditional bows. More modern slab sided boats will have plumb bows. I had a look at a new Farrier and for the life of me I can't get why the bow is reverse. The ama has vertical sides so an affectation and distortion is required to get the reverse bow to work. It does not flow from hull side orientation.

When I build boats you don't even have to draw the bows. A designer could leave the front 200mm off and say let the planking and fairing board do the rest. The bow shape will be a function of the rest of the boat but mostly hullside flare. So to get reverse bows on a cat you will have to have inward sloping hull sides. This is fine if the bows are long and thin but otherwise there will be a wobble as the hull sides go from inward sloping to vertical. If designers were using these bows for the reasons they are needed - to reduce drag when immersed then you would see a similar hull shape at least one quarter of the way back from the bow - a la A class, AC 45 and trimaran floats. But it does not seem as this the case - it looks as though the bows are stuck on normal hull shapes which is dumb if you believe that "form follows function".

As for fine bows and rounded bows I would go the rounded bow anytime. A fine bow is a dangerous thing in a marina. It can cause much more damage and get more damaged than a well reinforced bluff bow. Instead of having to exchange insurers you will get away with a "sorry". The drag difference is minimal and the spray on our cat never gets much above a foot higher than the water.

cheers

Phil

 

[catsketcher]

Some thoughts from Irens

A few years ago I interviewed Nigel Irens about the development of hull shapes. He said that one of the most influential cats of all time is the Tornado. He said that it was one of the first boats to use the idea of drag reduction rather than increase of buoyancy to counter pitch poling. This idea was furthered by Nacra cats and now the reverse bow proponents. It's a great idea for hulls that go underwater.

The idea is that it is not buoyancy but drag reduction that you want to reduce the pitchpoling moment at times like the AC 45 bear aways. Irens said that adding buoyancy can increase the pitchpoling tendency rather than the more obvious thinking that says the bows need more volume. On cats that will never dig in the hulls anyway - most cruising cats these bows have to be a waste of time. Add to that that the difference in drag between a reverse bow shape compared to a normal shape would be negligible on a cat with a forebeam, netting, catwalk, forehatches, cleats, anchor roller and anchor. May as well tape your ears back.

Do it for good reasons but never do it just for looks from the side. For an angle you will see the twists of the hulls side and wonder why the boat is unfair.

 

[daiquiri]

So what do you guys think of this bow?? It's hardly modern, as it was built in 1891, and was still in use last week when I took the photo.

Precisely.
By reading the discussions about plumb and reverse bows, sometimes one gets an impression that it is a kind of space technology, which comes together with carbon fiber composites and CFD analysis. The reality is - no contemporary designer or design firm has invented anything new there. These hull shapes, for example, have been crossing Mediterranean since the times of Ancient Greece and Roman Empire:

This one is a motorized version of an ancient Maltese Luzzu boat:

And so on...

Cheers

 

[hoytedow]

It's no use to look at submarine animals when designing a floating boat. A whale or barracuda, or sailfish don't have to break the surface tension of the water like a boat's nose does, therefore I present to you, the Black Skimmer, nature's own reverse bow. Now THAT'S biomimicry.


There's also a great website called Asknature.org (I think) where any biomimicry questions researched.

That's pretty cool and here is the website: http://www.asknature.org/

 

[BobBill]

Daquiri, very "kewl" and thanks.

I think they all serve, just depends on wet and aesthetic viewpoint. Again, I think Par may be right, another fad for some, functional for others who have specialty rigs...all fun.

I will post a pic of the odd ball I have decided to use on the MO...later.

 

[BobBill]

Precisely.
By reading the discussions about plumb and reverse bows, sometimes one gets an impression that it is a kind of space technology, which comes together with carbon fiber composites and CFD analysis. The reality is - no person or contemporary designer has invented anything new there. These hull shapes, for example, have been crossing Mediterranean since the times of Ancient Greece and Roman Empire:

This one is a motorized version of an ancient Maltese Luzzu boat:

And so on...

Cheers

You think MFA means My Fine Astern... :/ I know, had to do it though.

 

[mydauphin]

Original Wave piercing boat

 

[BobBill]

Original Wave piercing boat

Yep, and more...