Hi Robert,

Your query is a good one and still a grey area when it comes to model boat design and building. I have a considerable collection of model publications going back years and I don't really remember anyone trying to quantify the problem and put it into an understandable format. There have been a couple of articles 'way back when' but you would need to be a physics genius to understand them.

This is probably because there are so many variables in play here, the only people in the model game that would have a considerable knowledge of the subject would be top end racers, hydroplane competitors and propeller manufacturers as they have the greatest need for this information of all of us.

The pond side 'know it all' will spout figures, makes and sizes and is sometimes right but has no knowledge of the true theoretical reasons why such and such a prop should be used for this or that model and motor set up.

In the end it all seems to come down to knowledge based on ones own experience with different set-ups and trying a certain size prop on a model with a certain motor. Most of us will try at least a couple or so props till the model runs in an OK fashion, but whether that is the correct or most efficient set up seems to be in the lap of the Gods. At the very least our starting point for these choices are within certain parameters which can, hopefully save wasting bundles of money on props that will never work.

There are a lot of modellers on this forum who have far more experience than me and while I can recommend what has worked for me and my models many others will have similar knowledge of different boats and that is the beauty of this Forum.

Hopefully, if you give us all some ideas about the model you are planning or building and what you hope to power it with, then I'm sure you will get many tips and recommendations from fellow boaters.

Give it a day or two and hopefully once you've given us some details the recommendations will come flooding in.

Cheers……………RON.

Edited By Byron Rees…(Ron) on 21/01/2018 16:43:14

Yes, as stated above there are just so many variables that sometimes only very crude indications are available such as the motor getting too hot or the boat running too slow!

I did make an attempt to address this issue in the 2011 Special Issue of Model Boats which I edited. However this concentrated on matching motors to props on an empirical basis using examples from forum members rather than looking at RPM. After all it’s easy to vary the RPM by the speed controller setting and battery voltage.

**LINK**

Colin

Robert,

The article referred to by Colin above, and also by Ashley, was based on a survey of members boat performance information submitted to the website. There is a link to all that data here, including several of my own models. **LINK**

I have kept an Excel spreadsheet of the performance of all my models, some with several different motors and propellers fitted. If you would like a copy send me a PM with your email address and I will forward a copy to you.

Gareth