Here is topic for all sailors: Bow design – Theory or Looks?

Ok I’m baffled! What is the real skinny on this?
What is your though and is fact or Personal Preference?

Basically I see three schools on this:

The Classic Look – Bow at the deck level longer then the waterline with graceful curve to the water line.

Straight or slight taper – From the deck slightly longer then the waterline or straight.

Wave Piercing – I’ll call this A-Cat look the deck length is shorter the water line. So the there is a “reverse angle” from the classic look. Usually almost a straight line or a slight taper from the waterline back to the deck.

I can design the bows of the TMS-20 to any of these looks. Currently the design calls for a straight line on the main hull and a classic look on the ama’s.

Your thoughts?

Mike

Wave piercer looks so much cooler.

Definitely.

Maybe look to the dollars spent on research and design for the America's Cup boats and leverage your design on that(without spending the same dollars).

If you really want to dig into this-

http://www.boatdesign.net/forums/sailboats/wave-piercing-pitching-damping-marketing-18037.html

Bows with volume at the water line and finer at the top recover easier from submersion as the drag is lower as it rises vs. diving. Stick a conventional bow in that is wider at top, drag goes up faster, the bow slows down vs. the rig and over you go. The Bimare Javelin 2, 18Ht hulls are plumb, but have this configuration, volume low and skinny at the top. The N20 has tall bows for extra volume but are quite fine- different approach.

18HT


Ben Hall on his winged A cat-


bow shot of HT

On my Stealth I have canoe bows. You forgot those in your list

I've never seen those on any other cat, they look funky, but like a canoe the buoyancy is at the bottom and the top is all skinny.

Most significant effect of "wave piercing" bows on sailing multihulls is windage reduction..."wave piercing" benefits are marginal (and maybe negative, particularly if poorly designed)...I don't believe resistance will be less with the bow under the water...in my opinion.

I think it is more fashion over function in smaller boats.

Read comments by MalSmith in above boatdesign forum link.

My main hull bow come to a fine point at the tip then grows wider. The bow height is the highest
point of the hull. Also it has a bowsprit on the starboard side of the bow for the screacher and spin.
I have a flair that starts just past the bows very slight at first then significant to the stern.
The family will be back from vacation, they took the camera, I hope to pull the foam out of the mold
again and get some shots of the half hull foamed out to show the shape of the hull and posted it on
the web site.

Today I laminated a foam strip to form the bow stem and started to bog the inside of the hull to fair
it out. What a job there are compound curves and the foam strips lay worse on the inside. The outside
will not be as bad to fair out. I also have a drawing of the ama lines to post I update the website next.

Mike

Your effectively making the water line longer as well. If the longest point is always in the air, its not doing anything usefull.

TMS, what about utility?
After all you may want to be able to stand on the bow tips when docking (or, if push comes to shove, fend them off). What about being able to see how long you really have before you hit the dock etc? I can't offer any solutions, but you may want to think about the bow shape from a practical point of view also.

You should checkout the discussion over @ SA about the BMWO bow-down pics and wave piercing amas:
http://forums.sailinganarchy.com/index.php?showtopic=93626

I thought AC boats were designed to a box or formula, which may influence their design. Maybe something like Open type boats, but those are monohulls designed with heel in mind.

Is there a class of trimarans not limited by some formula? ORMA 60's?

Only a self imposed box. BMWO's challenge document said their boat had LWL of 90' and a beam of 90' . The only constraints on the swiss is lwl<90' if a sloop or LWL<115' if its a schooner or ketch.

"The Race" boats weren't restricted.

Don't take too much technical stuff out of the SA discussion, it's more of a pissing contest between pro-Alinghi and pro-BMWO posters.

For the record, I don't like the look of those submerged hulls and Alinghi doesn't have a trim problem! hahahaha!!!!

Wave piercer looks better stationary

Nothing beats the sheet of spray that comes of a Tornadoes bow at pace.

Lots of spray = lots of energy wasted.

Sailing Math

Lots of spray = lots of energy wasted

Lots of energy wasted < Looking Cool

Therefore:

Looking Cool > lots of energy wasted

And so furthermore:

Lots of spray = Looking Cool, and cancels out any concern for energy wasted

I don't care what everyone says about you Don, you're a Genius.

Wettest ride has to be a Supercat 20 I wear goggles and a snorkel