Ecodream, an optimized motor boat

Show me independent tests, say by two or three other people without a vested interest and I'll start being interested.

 

I'm at a complete loss regarding the generally negative and sometimes sarcastic tone of some of the comments so far. I figured there must be some bad blood and went back and read the other threads the OP has contributed to; but didn't see any problems there.

The OP stated he is trying to optimize a design. So yes, the darned blanket is going to get stretched. The OP wants the widest speed profile and apparently is willing to consider a single displacement when getting there. Fine. That's the game being discussed.

The boat he's built has a specific drag profile. We don't know what that is yet, but what is the objection to the way he's gone about it?

Is the objection that anyone could achieve this level of performance without the interceptor kit?

Or is the claimed performance being challenged?

Is there a feeling that basic engineering data is being withheld?

OP, could you provide the specs of the test mules? Including motor ID and trim vs speed?
Do you have fuel consumption figures over a range of speeds?
Can you isolate the effect of the interceptor numerically? Or is it integral to the hull design to the extent that the question doesn't make any sense?

 

yup....to much negativity.

It has stunted the dialogue concerning an interesting boat

 

The problem is with the idea that the "interceptor" idea is new or novel (it's neither), with the way that it's been claimed to be a new "invention" (it's not), and the history of this being promoted here over several years as the best thing since sliced bread, yet, to the best of my knowledge, it has yet to be seen on any production boat.

I spent (some might say wasted) a few hours a couple of years ago looking long and hard at how the idea might work (as Jurgen Sass had recommended it for my specific low power electric boat application), before concluding that it was not at all well suited to this application. Take a look at Jurgen's website : http://www.sassdesign.net/ and tell me how many completed full size boats you see, with verifiable performance enhancements resulting from this "interceptor" technology.

Worth also looking at scale effects and how they affect measured flow performance on relatively small scale models.

 

So why not just ignore the thread?

 

Isn`t it interesting enough to see how a hull is optimized by destroying the normal laminar/turbulent flow at the bottom ?

 

The interceptor is NOT destroying the turbulent flew, it is working inside of the turbulent flow, the boundery layer. If you deploy it more it becomes a brake.

I will be back later.

JS

 

I will be in a position to do this test on a 1:5 model in the next few weeks.

The current model hull shape is ideal to see if the concept is workable, as its design brief is to provide good motoring performance from a quite efficient sailing hull shape. I am half expecting I will need trim tabs for optimum performance, and this 'interceptor' concept would be interesting to try.

 

Independent test

Independent test?
Not optimised!

js

 

Name of owner, type of boat and pictures would be more scientific

 

Background information

I have over the years collected over eight hundred pages about interceptors. These are independent scientific reports from around the world. The oldest is from 1932.

From this extensive material I have chosen what is of interest in order to create a reliable method of calculation.

What I did this past year is to test this method in model and full scale.

The main conclusions are that the interceptor lift force is proportional to its span and its resistance is related to the boundary layer height, which in turn is related to the wet length among others. Why this is so is not entirely clear yet. The area that the interceptor affects extends about as far forward as its span. Pressure Centre is located approximately one-quarter of the span in front of interceptor.

With this background, I can now calculate the lift and drag for the interceptor with acceptable precision. In the example of the interceptor located in afterbody the interceptor takes about half of the lift force. The remaining lift and drag can be calculated in the usual manner according to Savitsky, Almeter and Radojcic and others.

These two forces are balanced then around the overall centre of gravity.

We have tried with different longitudinal positions of the interceptor on one of our 5.5 meter boats to confirm the calculation method.

To achieve optimum results, the interceptor has to be adjustable to adapt to the current weight and speed.

A few months ago I moved from Vaxholm to Gräddö. When I was moving my boat with midship interceptor I had the opportunity to more closely measure the fuel consumption. Mostly the trip was a little bumpy so the speed was around 15 knots. The length was 35 nautical miles and the fuel consumption was 8.4 litres. This will be 0.24 litres per nautical mile, which is not optimal yet. That's why I want to move on to other options, such as the aftship interceptor.

JS

 

Thank you JS for your kind help to understand what`s happening within the thin boundary layer. Found another approach to reduce skin friction in an old patent: http://www.google.com/patents/US5456201

 

No, I never dream of the ultimate boat, and I design and built for more than 40 years.
I think this statement is very odd. Each customer need a different approach and different design.
If you dream about the ultimate boat, don't make it a generality.

 

Ive seen similar turbulators used on race boats. They proved to be not effective. I dont know why...perhaps the waterflow over a sailing yacht at sea is too random

 

Abstract on interceptors

Here comes an abstract of my lecture on interceptors at KTH in Stockholm.
js