Boat shapes? Nature knows

[trawlercap]

A boats motion, carrying ability, accommodations, fuel burn, on and on. All these things come into the design. Over many years, I've come to say "A boat is like a horse,hood ones and bad and they're all individuals, each responds differently to make them go or stop. A bad rider can kill a good horse, but a good rider can bring a limp horse home."
Same with boats.
I've learned to keep the weight in the middle. Momentum is a big deal. Take a stick, spin it with weights on the ends. It continues to spin. Then move the weights to the middle, it stops much sooner. If you add weight to the ends of you boat (engines aft, tanks, etc.) your motion will increase. If your bow and stern get heavy, it will be slow to rise, and drop much harder, and hobbyhorse.
Nature shows a pinched stern is most efficient. The 58' Bill Garden I just got shows almost no wake. It's fat underwater shape is similar to a Whale or Tuna.

View attachment 110622


This vessel, designed by a master when another set of priorities ruled. It is widest just forward of the middle to (carry the weight.) Engine room in middle, very low salon (by todays standards) Open (less windage) aft. Wheel house far back (by todays standards) off the bow (lighter bow, avoid big waves impact)
I have so much more to learn, these are my initial findings. Disadvantages? The pinched stern is less roomy, The low house barley clears my 6'0" frame. Accommodations are interrupted by a big roomy engine room. Master aft, guests forward.
Square full sterns work well to gain speed, accommodations, storage etc. And this double ender boat will never do 20 kts. I've seen 20Kt. boats at 10 kts. making huge wakes. That's got to be wasted energy.
Light in the ends, weight is centered in the middle, low windage, it slips through the water so sweet, like I've never seen.

 

[Nomad Willy]

Tcap wrote;
“ I've learned to keep the weight in the middle. Momentum is a big deal. Take a stick, spin it with weights on the ends. It continues to spin. Then move the weights to the middle, it stops much sooner. If you add weight to the ends of you boat (engines aft, tanks, etc.) your motion will increase. If your bow and stern get heavy, it will be slow to rise, and drop much harder, and hobbyhorse.”

Indeed it appears to be that way. But balance isn’t just throwing all into the middle calling it good. Putting 50% of the weight in either end or all in the middle dosn’t make a good boat.

Ideally about 25% in each end and the other half in the middle is IMO about right. Then fine tune to fit an individual boat and things will probably be good to go.
Having a boat very light at the ends would make it VERY responsive to the helm and also very responsive to the whims of the waves. But skippers like to have control ... understandably. Mariners call shuc a boat “lively”. Quick to turn and quick to get out of control.
If the weight is in the ends and a boat it yaws toward a trough and gets some momentum up the inertia could cause all kinds of problems. The worst problem would be how doggishly slow the boat would respond to her helm.

And of course the hull shape has a lot to do w it too.

BALANCE in all the dynamic forces makes for a good boat.

As to fish form hulls they work wonderfully well .... underwater. But half underwater not so much. Evolution designed the fish. NA’s design boats.
Boats (in general) travel at numerous speeds within a range. The NA fits the boats hull and all else. Some fish are slow (grouper) and some fast like a barracuda. The slowest (like the grouper) are short and fat w more girth fwd while the barracuda is long and slender. Sailboats are very slow. Pointed at both ends and very wide amidships.
You’ll notice the FD hull has a fairly wide variety of hull shapes on a single hull. Take shapes from horizontal lines and vertical lines and one could go further than that.
But w a fish rotated radially and observing slices taken at points you will see they are all very much alike ... unlike the boat that needs to travel on the surface of the water.

But TrawlerCap your boat has been idealized to an extremely high level of desirability. In every boat there are compromises to be made and if we dug deep enough we’d find some compromises in your boat. Be thankful that Mr. Garden was the man making those compromises. Make a change here (different engine) and make one or more changes to accommodate the original change, evaluate it and take the next action. This fine turning is what makes a very fine boat ... like yours.

 

[Arc]

I builder told me. ‘ if it doesn’t look right , it’s not “

 

[klee wyck]

A boats motion, carrying ability, accommodations, fuel burn, on and on. All these things come into the design. Over many years, I've come to say "A boat is like a horse,hood ones and bad and they're all individuals, each responds differently to make them go or stop. A bad rider can kill a good horse, but a good rider can bring a limp horse home."
Same with boats.
I've learned to keep the weight in the middle. Momentum is a big deal. Take a stick, spin it with weights on the ends. It continues to spin. Then move the weights to the middle, it stops much sooner. If you add weight to the ends of you boat (engines aft, tanks, etc.) your motion will increase. If your bow and stern get heavy, it will be slow to rise, and drop much harder, and hobbyhorse.
Nature shows a pinched stern is most efficient. The 58' Bill Garden I just got shows almost no wake. It's fat underwater shape is similar to a Whale or Tuna.
View attachment 110621
View attachment 110622


This vessel, designed by a master when another set of priorities ruled. It is widest just forward of the middle to (carry the weight.) Engine room in middle, very low salon (by todays standards) Open (less windage) aft. Wheel house far back (by todays standards) off the bow (lighter bow, avoid big waves impact)
I have so much more to learn, these are my initial findings. Disadvantages? The pinched stern is less roomy, The low house barley clears my 6'0" frame. Accommodations are interrupted by a big roomy engine room. Master aft, guests forward.
Square full sterns work well to gain speed, accommodations, storage etc. And this double ender boat will never do 20 kts. I've seen 20Kt. boats at 10 kts. making huge wakes. That's got to be wasted energy.
Light in the ends, weight is centered in the middle, low windage, it slips through the water so sweet, like I've never seen.

View attachment 110629

Agree with this. Seeing your wake was impressive so I paid attention to mine again yesterday which has always impressed me as well. Perhaps not quite as skookum as the Garden, but close I think.
Here is a photo of the wake of Klee Wyck yesterday at 8 knots (s/l of 1.17) at 1600 rpm. And one of her stern shape.
Pretty quiet I think.

 

[trawlercap]

Saweeet image man. That is nice! I'd love to know more! All billion$ subs have a similar shape.

 

[sean9c]

Bill Garden drew some nice sterns, Oceanus was probably the prettiest ever. All Garden designs are interesting and extremely varied. He published 2 books of his designs, well worth owning. Your fish, or submarine analogy is not accurate, they operate submerged hopefully Katherine Jane never has to.
Yacht design is a tricky business, you could likely not sell a new boat as large as yours with that small of an interior. The consumer wants more, so designers have to deliver. It's certainly not uncommon for builders to now draw the interior they want first and then figure out how to wrap a hull around it.

 

[klee wyck]

Saweeet image man. That is nice! I'd to know more! All billion$ subs have a similar shape.

View attachment 111014

View attachment 111015

Here is her sister which we also own. This one is only four feet longer at the waterline but weighs 245% more at 67 tons due to heavier gage steel in the hull and massive ballast. She will run 1.1 s/l at around 1450 rpms from her Mercedes OM403 V10 which I think is only putting out around 140 bhp at this setting. Pictured are both of her ends and a side view of her mid section.
At 7.8 knots she puts out this little double wake from her bow and stern waves that is about 6" high and water is flat behind her.
I think all of this is just feel good about how clever the NA was in the design efficiency rather than material savings in cost of owning and maintaining these rec boats, but still very cool and reason enough to inspire me....

 

[Nomad Willy]

Saweeet image man. That is nice! I'd to know more! All billion$ subs have a similar shape.

View attachment 111014

View attachment 111015

EVOLUTION trawlercap

 

[trawlercap]

Bill Garden drew some nice sterns, Oceanus was probably the prettiest ever. All Garden designs are interesting and extremely varied. He published 2 books of his designs, well worth owning. Your fish, or submarine analogy is not accurate, they operate submerged hopefully Katherine Jane never has to.
Yacht design is a tricky business, you could likely not sell a new boat as large as yours with that small of an interior. The consumer wants more, so designers have to deliver. It's certainly not uncommon for builders to now draw the interior they want first and then figure out how to wrap a hull around it.

Below the waterline runs under water, you flip this boat, it looks like a whale.

Compared to todays designs, the salon has a low ceiling, and stops short of the stern. The living room is narrow for a 58' boat. The wheelhouses is set back from the bow. I tell folks inside is like lake cabin from the 50's. They don't build little simple cabins by the shore anymore. Market demands much more.

Out side you loose deck space with pointed stern. The walkways are wide with high bulwarks and a real hand rails, all the way around. Wheel house aft helps keep the weight off and a big clear bow will better rise to big seas. The low, short salon for minimal windage. The hull is deep and wide with a real engine room in the middle, accommodations are fitted around this. It took 58'' to make a livable space with these parameters. Whale shaped under water, minimal rugged above.

 

[trawlercap]

5 min. video of the "50's lakeside cabin"

https://youtu.be/rfcphJhimCw

 

[Alaskaflyer]

https://jeb.biologists.org/content/jexbio/53/3/763.full.pdf

Perhaps the shape of a duck's a.... uh, bottom is more analogous.

 

[FF]

In the 1800's the "cods head and mackerel tail" was in vogue.

Eventually the builders realized fish swim IN not ON the water , and wave making was the cost of moving thru the water..

 

[trawlercap]

In the 1800's the "cods head and mackerel tail" was in vogue.

Eventually the builders realized fish swim IN not ON the water , and wave making was the cost of moving thru the water..

As well as windage, ability to withstand grounding, hold to to a dock, carry weight, tankage, stability, withstand boarding seas, on and on. Lots to consider.

 

[Hippocampus]

https://www.artnautica.com/designs/long-range-cruiser-58
https://setsail.com/fpb-64-theory-reality-2/

Different approach equally safe and more efficient. Will note rescue surf boats and SAR vessels have also taken this line of thinking in recent decades. Even nordhavn and like transom boats can be great seaboats. Leishman and Beebe both worked off an old school design way of thinking which made use of the benefits of having a transom.

 

[Hippocampus]

The duck article was fun. Thanks. One of the things not often thought about in these discussions is boundary layer effects and influences on parasitic drag. One wonders about waterfowl. Their feathers do a remarkable job of trapping air and keeping them warm and dry. But like shark scales effects on drag wonder about feathers effects on preserving a boundary layer of air and decreasing parasitic drag.
See boats with no indented fairing aft of bow thrusters or with multiple through hulls or “maintenance strakes “ and their effects on drag. Think even not taking a bottom down to smooth with no indents from prior flaking makes a huge difference. Also placement and nature of zincs. So many things to consider and think it all adds up.

 

[Nomad Willy]

Whale like Shape

Here's a pic of Willy on the tidal grid that shows she does look somewhat like a whale ... from certain angles. SD need not apply.

klee wyck,
Would like comments on how that very interesting anchor works?
New anchor thread??