required parts

[Peter Smith 24Participant @petersmith24]

This is my first boat. I like building things from scratch. I have the hull built but when I look at the section about the workings of the boat it all gets a bit confusing.

For example a stern tube, what size? I can see it on the drawing but where do you measure from.

I can see motors etc. on sites but what is best for this type of model.

[Peter Smith 24Participant @petersmith24]

Tugboat Craig

[ashley needhamParticipant @ashleyneedham69188]

Peter. Welcome to the Mb forum.

​Well done for having a go and scratch built at that.

What size is the tugboat and what size is indicated for the prop on the plan? Usually the plan suggests a motor type, and the choice of motor will also depend on the battery voltage.

The drive system consists; Motor, coupling between motor and propshaft, and propshaft assembly.

You will need a coupling to connect the motor to the shaft. Usually one of those ones which have brass fittings on the motor shaft and on the propshaft and a red plastic universal joint in between. If you are following a plan, the motor position will be indicated, and also the propeller location will also be indicated. The tube length that you want (this is the TUBE measurement), will be that between the end of the coupling and the propeller, minus about 6mm to allow for the lock-nuts. The couplings are about 35mm or so long (ish). propshaft tubes come in set lengths if bought "off the shelf", say 6,7,8,9 inches of the equivalent in mm. Holding the prop in approximately the right place and the motor with coupling (or allowing for the coupling) and measure between the two. No doubt it will not be an exact inch distance, so the motor mount can be positioned to suit.

I have seen diagrams of this no doubt someone will find one and stick a picture on a post.

Ashley

[Paul TParticipant @pault84577]

Hello Peter

It is difficult to explain without having a copy of the drawing to look at so it would help if you could scan the drawing and post it here then we would have a common reference point.

It will also help you to know that this model (or one called TugBoat Craig) has been covered before on this forum **LINK**which might help answer some of your questions.

Paul

Edited By Paul T on 02/10/2016 18:50:53

[ashley needhamParticipant @ashleyneedham69188]

See I knew someone had a better answer (and an encyclopedic knowledge of previous posts)

​Ashley. Yes yes I know its easy to search……

[Yabbie1Participant @yabbie1]

Hi Peter,

I didn't intend Tugboat Craig as a first scratch-build model, so well done for getting this far! The project does assume some previous experience.

A stern tube of about 7" (180mm) – measure the tube, not the shaft – should be fine with a normal motor installation and single universal.

[I used a shorter stern tube only because I needed a bit of extra length in the engine room for the motor I used (which was a heater fan motor from a scrapped full-size car), and to fit two universals.]

You need a high-torque, low-revving motor to drive the 63mm dia. 4-blade prop. Some types of five-pole RS545 motors are OK or perhaps an RS755 – see what your usual supplier has in this category. If you can't find a high torque one for direct drive, you can use a geared motor of about 3:1 ratio.

Since the article was written brushless motors have become a viable alternative but I fear that might be confusing you further.

Good luck with the build, my 'Craig' still enjoys regular outings.

Yabbie1 (John Parker)

[Dave MilbournParticipant @davemilbourn48782]

I reckon this motor on direct drive (no gearbox) will turn a 60mm prop very nicely on 12v. **LINK**

DM

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