EcoSmart, an efficient motorboat

Not quite; you claim in the design comparison that it has the same total weight. Also there are claims that in needs 1/3 less power, 1/4 less power, and half the power requirement. At least two of your claims have to be wrong, maybe all three.

 

Show us your calculations, model tests, and full-scale tests that underlie your claim that my conclusions are wrong.
JS

 

I don't need calculations. It can't be 1/3, 1/4 and 1/2 at the same time depending on convenience.

 

The final result reported in post 27 speaks for itself. The important thing is that the client is satisfied. With a sharpened propeller, the result can be improved somewhat further.
JS

 

I think there is some confusion here.
The confusion is between semi-planing and planing. The definitions of each are sketchy as far as I'm concerned. My personal definition for each is this:

Semi-planing is when the water flow breaks away from the transom or stern post and closes somewhere after it.

Planing is when this condition happens and the boat lifts higher in the water.

Semi-planing requires less power per weight than planing does, but it allows for lower speeds than planing does.
For higher speeds, real planing is required.

A good semi-planing boat should be narrow for its length. This is so its bow can part the water better and its hull has to move it aside less.

A good planing boat should be wider, especially at the stern. This is because it is the stern bottom which lifts the boat. The wider it is, the more lift it produces. If it produces enough lift, the bow has to contribute very little lift itself. When this is the case it can be given a sectional shape that doesn't pound as much.

A narrow boat can be made to plane by having the bow contribute toward the total lift. But this means its bottom must be flatter. Not only that, but more of its hull surface area is being dragged through the water.

So, at semi-planing speeds, and lower planing ones, it probably is the better design choice.
But at higher planing speeds and greater weight per length, the wider hull is best.

 

Sharpii
That was a highly personal description of what semi-planing and planing are.
I describe semiplaning as speeds around FnL 0.7. It is the speed at which the wave formation around the hull is most favorable.
And planing over FnV 2.7.
JS

 

To increase the understanding of EcoSmart, the measured result is reported here together with the drag of other boats. It shows that EcoSmart has completely different properties than usual.

 

I hate to admit it, but I'm not sure what an FnL is.
My guess is that it has something to do with what used to be called "hull speed", which was supposedly 1.34 time the square root of the waterline, measured in feet, in knots.

From my reverse engineering of these two numbers you gave, based on my assumption, for a boat with a 16 ft waterline, I get 5.71 kts for an FnL of 1.0.
For an FnL of 2.7, I get 15.4 kts.
And for an FnL of 0.70, I get 3.99 kts.

Do I have this right?

 

Great

Logical

Planing, imo, is a paradigm that has become an idol and it is interesting to attack it from two opposite sides:

Sailboats: abandon the obsession with Drag, and concentrate on surfing. Surfing small and large waves with comfort and safety

Motorboats: become obsessed with Drag as if it were a racing sailboat

---

sailboats are obsessed with not having the bow trim up and the hydrostatic vector having an aft component when leaning aft. And they should calm down and reduce this obsession, because sailboats sail better (in the sense of being more comfortable and safer) with the bow up.

And just the opposite:

Powerboats planing by brute force easily forget the Drag created by the aft inclination of the hydroStatic and hydroDynamic vector. So much bow up and so much lift at bow is not efficient from the point of view of fuel consumption.



(Unfortunately, i entered the 'shipyard'* through the emergency room, and i will not be able to continue this interesting thread. Take care of yourselves, exercise, lead a healthy life)

(*: where i have found two things that admire: professionalism and a good heart, reconciling myself on a small scale with this horrible planet)

Kind regards to everyone.

 

No, most of it is wrong.
Firstly, there is no such thing as hull speed.
Hull speed https://www.boatdesign.net/threads/hull-speed.32698/
Then you mix up FnL and FnV, where L stands for wave-forming length and V stands for volume, actually total weight.
Planing speed is over FnL 1.0 and over FnV 2.7
JS

 

How was the resistance of the EcoSmart boat measured to obtain the data shown above?

 

Since it is an electric drive, it was just a matter of recording how many kilowatts were needed at different speeds. These values have then been converted into driving force. The recalculation is based on generally accepted methods. The values have been compared with other boats and extensive model tests.
JS