new design motor size assistance

[wayne nicol]

Hi all, we are working on a new boat design, and we want to move up a step past the drawings stage. and we want to build a smaller hull mockup, design is for a 33' power boat.
we are wanting to build maybe just a 10' hull mock up and test the performance of some of the unique features.
is there a way to make a guesstimate of what size motor would be used on the mockup, maybe based on the designed in motor size of the bigger craft.
i realize there are a lot of other variables, mass, bouyancy etc, but we just want to confirm a few things before moving up to a full size build.
many thanks

 

[jehardiman]

It's not the motor, it's the prop. If your "unique features" have anything to do with propulsive hydrodynamics it is better not to use a geosim model but just conduct basic research to flesh out some operating points in the theory.

 

[wayne nicol]

thanks,
the features are design features within the overall hull shape.
we were looking at doing some tow tests with the local university with their NA program, and that's good and well as its free, however, we lose any rights to the design concepts as they are introduced into the teaching program.
so were wanting to do some of our own simulation trials comparing at least 3 different hull shapes, one being the industry standard, as that one will be used as the control/benchmark.
thanks

 

[jehardiman]

thanks,
the features are design features within the overall hull shape.
we were looking at doing some tow tests with the local university with their NA program, and that's good and well as its free, however, we lose any rights to the design concepts as they are introduced into the teaching program.
so were wanting to do some of our own simulation trials comparing at least 3 different hull shapes, one being the industry standard, as that one will be used as the control/benchmark.
thanks

Look at this thread, just be aware that some things don't scale well.

L/B ratios the same for short and long hulls? https://www.boatdesign.net/threads/l-b-ratios-the-same-for-short-and-long-hulls.67070/#post-930525

 

[HJS]

To obtain reasonably comparable results, a load cell should be placed so that the propeller pressure can be measured. Anything else can lead to incorrect conclusions.
JS

 

[tpenfield]

Does the university have any guidance on scaling down a full-sized hull for testing purposes (without compromising your Intellectual Property rights)? I assume the 10' model will be too big for most test tanks. Is it better to use a smaller scale model and a test tank?

 

[messabout]

Have you explored the patent office for prior art? People have been "improving" boats since before Archimedes.

 

[gonzo]

You can tow the model with another boat and make a chart of resistance at different speeds. That will give a fairly accurate estimate of power needed.