Hi and welcome Joe

Brushless and LiPos definitely. Thoughts tend to be that twin motor setups aren't much quicker if anything than single so the motor sizes will be pretty much the same.

Initial thoughts would be something like a pair of Overlander 5045/10 720kV which on 4S LiPo would rev at 10600.

Is this around what you're thinking of?

Chris

Joe. GENERALLY speaking, in-runners seem to be in the higher revving bracket, but outrunners vary from 40Kv to 10,000Kv (for ducted fan use).

Accepted wisdom here is that a motor matched to the hull/prop may well get warm, but should not necessarily require water cooling. That said, interior ventilation is recommended to stop heat build up.

Sorry, would not like to hazard a guess as to what you might fit. However, fitting a more common size pays dividends if/when you want to swap them out.

DM is the Fairey god and he will lay down chapter and verse as to what you should fit….

Ashley

I bow before the master.

Ashley

Edited By ashley needham on 02/05/2020 18:09:06

Hi again

As Ashley says, inrunners are generally high revving motors and for boat use more suited to very high performance and race craft. With something of the size, weight and design of many of the Fairey Marine model boats what you need is a fairly torquey motor to get it moving and then with sufficient revs to give it a good top speed.

Outrunners are more torquey so one decision made and you need one with quite a large diameter to give the power required. I generally recommend a motor around 900 to 1100 kV as a good compromise but as motor diameters get bigger the kV tend to get smaller hence why I suggested the 720kV motors. The motor DM suggested is even lower which is why he's suggested running on a 5S or 6S LiPo pack to increase the revs and give the performance required. You pays yer money and makes your choice.

I doubt that my suggestion will be underpowered as brushless motors are very powerful for their size, probably the opposite! And you can always increase the volts!

I have one of the big Huntsman, when the kit was produced by Precedent and I'll see how much it weighs. I know it's bloomin' heavy!

Chris

Edit: Dave posted whilst I was rambling so has given you more info.

Edited By Chris Fellows on 02/05/2020 19:52:43

There has been a number of builds using twin motors. There is one on Model Boat Mayhem at the moment but it is for the smaller 34" version and he's using brushed motors so can't really interpolate from that.

Chris

Joe

Imagine putting a V8 in a Mini and you will get the general idea.

Joe

And I forgot that a chap called UKMike is building the same kit on Mayhem in the Pleasure Boats etc. section in a thread called Fairey Huntsman Aft Cabin Becomes a Sports Fisherman. As the name suggests he is making some modifications to the build which includes fitting 2 No. 1kW motors. He is a very meticulous builder and made a lovely job of a Riva. I don't know how he has arrived at the power required and what motors he is proposing.

In my suggestion I was looking at 50mm diameter for more torque but I see that the 4250/06 800kV that I've bought to go in my Swordsman 33 produces 980w so a pair of them could be a good choice. I tend to use Overlander but Leopard and Turnigy are good as well.

I see that the spec. for those you are thinking of is 3100w (yikes!) and they are recommended for race boats. I refer to Paul's post!

Chris

Edited By Chris Fellows on 03/05/2020 11:11:12

Hi Chris

Never throw a motor away, it will be ideal when you build a tug boat 😀

Regards Ray

There is some serious over estimating going on here.

Chris has posted a nice picture of a boat going reasonably well on an 850 motor (120watts, ish?) and a big SLA. I know it would go a lot better with a Nimh pack, and even more betterer with. Lipo, on the orig motor.

All this talk of 900W motors….?

Ashley

Ashley

There's no avoiding the fact that the very first big Huntsman 31 had a powerful 10cc glowplug motor installed; 1.2BHP is around 900W. There's no estimation involved there, m'duck.

Dave M