Old Motor Torpedo Boat

[John O’CParticipant @johnoc]

I would say the mkV otter is it! Thanks Dodgy

I think it can stay on the shelf for another project and I will go electric.

Now do I go twin or triple in a 40" hull?

J

[Dave MilbournParticipant @davemilbourn48782]

Now do I go twin or triple in a 40" hull?

Just the one big brushless should do the job. Why buy two or even three of everything, and also double or treble the potential for problems?

No-one can count the props when it's in the water, John.

Dave M

[John O’CParticipant @johnoc]

My wife thanks you for that Dave. I had just put my Santa order in for 3.

Nice thinking though.

Having read many of your posts what would you recommend?

J

[ashley needhamParticipant @ashleyneedham69188]

Recommend…what, how many props?? That is not a question that can be answered definitively on the forum (or any other forum) as everyone has their own ideas!. For straight performance and cheapness economy a single prop is it, for looks out the water (where most of the boats spend their time), then three nice shiny brass props looks the business. Two, for my money is a halfway house number on a pt boat and should not be considered.

However, that's only my opinion. You should weigh up the factors and choose. At the end of the day, it will work well on one ,two, three, or even four props….

​Ashley

[John O’CParticipant @johnoc]

Hi Ashley

The recommendation request was for motor and prop size on a single. As said previously the boat has 3 in real life so 2 or 4 are pointless. The choice is economy and copying what the original build had or going to 3 and what the real thing had. Being still a learner any advice is welcome.

Cheers

John

[Dave MilbournParticipant @davemilbourn48782]

John

I have to admit that I've not built a model of this size with a brushless motor, so what I would say should be viewed in that light. If the model was mine I would probably fit a motor like this one **LINK** and run it on a 3S LiPo pack (11.1v). Prop would be something like a 40mm or 45mm 2 blade. Start with the standard pitch and then see what happens with the X racing type.
Two very popular RC scale model boat kits are run with a single motor, while the full-size boats have 2 and 3 props (Huntsman and Perkasa). As I often say, suit yourself.

Dave M

[John O’CParticipant @johnoc]

Thanks Dave.

Really helpful and appreciated.

J

[Ray Wood 3Participant @raywood3]

Hi John

Diesel's are lower revving than glo and have more torque, my old time Eaglet & Mini Tyro make a more sociable noise. I would keep the old radio installation in the boat (non functioning), it makes the boat interesting, MTB's are ten a penny even I'm making one

Regards Ray

[Paul TParticipant @pault84577]

John

Where are you going to sail the MTB?

Paul

[John O’CParticipant @johnoc]

Ray

Thanks for the input and I will try and position the old controls if possible. A single motor would help on that front. Love your boat looks amazing in the pics and puts my workmanship to shame but I still strive to improve when I see work like that. I need to slow down really.

Cheers

John

[John O’CParticipant @johnoc]

Paul

To be honest my history of sailing my models is hopeless!

I have never had my current models on any water other than my fish pond to test they are watertight and the controls work.

The only place I know of is the stretch of water used by Crewe club, Boundry Park Lake.

John

[Paul TParticipant @pault84577]

John

One of the main problems when wishing to build and sail I.C. powered boats is that the resident club usually don't allow such evil things. Crew club is no exception as their Rules ….Section 9 General Sailing Rules para H states: No Member may operate an Internal Combustion powered model boat.

I have had no end of bother finding places to sail my modest little petrol powered boats and usually end up on the local canal.

Some clubs are also dead against high powered 4ft MTBs on the principal that, in the wrong hands (i.e not theirs) the model becomes a high speed deadly weapon capable of wiping out all mankind.

In summary: sometimes its better to sort out your sailing venue before deciding on motive power.

Paul

[John O’CParticipant @johnoc]

Hi Paul

I will take a run around the canals and the River Weaver to see if there is a place I can park and easily launch as I will do something with the diesel in the future.

I will go to the Crewe Club lake and see if I can launch Smit and Scrappy there. I know a chap I sold a yacht I built to sails there so it would be nice to see that on the water as well.

The hull is getting there with the stripping back and I have left the water scoop in place as I will try and source a small pump and a smoke generator to use the water and engine exhausts at the stern.

Stripping the superstructure will be time consuming but it has to be done.

Cheers

J

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by John O'C on 09/11/2016 14:21:32:

The hull is getting there with the stripping back and I have left the water scoop in place as I will try and source a small pump and a smoke generator to use the water and engine exhausts at the stern.

Not sure what you want the pump for. The water scoop sits in the propeller slipstream, and the pressure of water when the engine is running is usually enough to push it around the cooling circuit and out of the water exhaust fitting….

[Paul TParticipant @pault84577]

DG

A water pump is necessary especially if the model spends a lot of time stationary with the engine ticking over.

[Dodgy Geezer 1Participant @dodgygeezer1]

I never found one necessary with any of my Aerokits back in the day. Even on tickover the water circulated ok. And I don't know how you get a model with an I/c motor stationary on tickover, unless you have a clutch…

I can't think of any advisory documents from that period which recommend a pump, especially for a fast planing boat. One might be needed for a displacement hull like a tug, with a clutch and gearbox…

[Paul TParticipant @pault84577]

An IC engine without a clutch is like a parachute without a ripcord….a cheap shortcut that is difficult to use and ultimately pointless.

i imagine that some of the racing models don't have clutches but those boats aren't intended to float around on tickover.

[John O’CParticipant @johnoc]

Whoa guys

Given all the problems my intent is to put an electric motor in the boat so the circulation of the water is for show really unless you think the motor needs a cooling coil?

Having said that the scoop behind the prop' could well be enough when on the move.

J

[John O’CParticipant @johnoc]

Paul

You have me intrigued.

Is the clutch a bought item?

J

[Paul TParticipant @pault84577]

John

The clutch on a model boat petrol engine can be purchased but they are rare, my boat engines tend to be from strimmer or hedge cutters and have a clutch built in.

I think you are right in opting for an electric motor as they are far less trouble.

Paul

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by John O'C on 10/11/2016 16:30:12:

Whoa guys

Given all the problems my intent is to put an electric motor in the boat so the circulation of the water is for show really unless you think the motor needs a cooling coil?

Having said that the scoop behind the prop' could well be enough when on the move.

J

I don't think you're going to find a clutch for that motor, so that issue is moot anyway.

For brushless motors you may cool the motor, the ESC, or both. Cooling inrunners is done with a water jacket – outrunners can have a cooled mount.

Brushless motors are somewhat different to brushed motors, which usually have a defined Volt/Amp rating they are designed for. DM will doubtless provide a better explanation, but I see brushless motors as simply being able to steadily output more and more power as you up the voltage until the wires in the motor burn out and the magnets lose their oomph. So the thing that limits a brushless motor is simply the temperature.

You can make a small brushless output huge amounts of power if you cool it effectively. But the other side of the coin is that, if you overspec the motor and the ESC, you can run with oodles of power and a motor which stays cool without any cooling at all. I suggest that you pick a motor/ESC combination that needs little or no cooling at the output you want, and then ensure that there is a bit of an airflow through the motor compartment to stop any heat build-up.

The bigger amperage marine ESCs usually have a cooling pipe running through them – it will certainly do no harm to attach a water pipe to this if you have one available…

 

Edited By Dodgy Geezer on 10/11/2016 23:15:10

[Paul TParticipant @pault84577]

I don't think you're going to find a clutch for that motor, so that issue is moot anyway

Finding a clutch isn't a case of having to locate a specific item….. Its just finding one with the correct shaft size

link

 

Edited By Paul T on 11/11/2016 15:19:46

[Dodgy Geezer 1Participant @dodgygeezer1]

Interesting – but these all look like spare parts for Zenoahs and such like. Is there a complete stand-alone clutch, with drum/bell housing there? One that would be suitable for a 3.5 cc diesel?

I have seen a few home-made ones on model tugs in the 1960s – once as part of a complex gearbox giving neutral and reverse with a petrol motor – but have never seen them on run-of-the-mill speedboats such as the Sea Queen, PT Boat, Perkasa or Crash Tender. None of the plans for these boats include a clutch either…

[Paul TParticipant @pault84577]

DG

Clutches and gearboxes for IC have been available since the late 1950s but being expensive they rarely showed up on run-of-the-mill models.

[John O’CParticipant @johnoc]

Paul

Is there a clutch mechanism that would fit between the engine and prop' shaft to allow the engine to idle with no revs on the prop'?

I have just asked Freeprawn Racing but wondered if you knew.

Regards

J

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