Motors/Cost

[Peter Smith 24Participant @petersmith24]

[Peter Smith 24Participant @petersmith24]

I have just completed John Parker's Tugboat Craig. This was my first encounter with model boats. The whole experience has been excellent.

I have sent for plans of another of Mr Parker's design. This is his Picket Boat which I can build with the aid of his plan feature in the winter edition 2014.

The build I love and find this kind of work suits my past employments. My problem this time is the motor. This is of the brushless type which seems rather complicated. My concern is also with cost, the price of these seems to rise to greater levels.

Is there a normal brushed motor that would function just as well and meet my pensioners budget.

[ashley needhamParticipant @ashleyneedham69188]

Peter. The cost rather depends on what size of brushless motor you need. I don't know much about the picket boat, but I am guessing it is not too big and a relatively small brushless motor would be suitable, and these are very cheap off e-bay. The cost rather seems to be in the electronic speed control department, whereby there are cheap ones out there but these likely do not reverse, and the Chinese ones can be of dubious reliability.

​What size and Kva brushless motor does the plan specify?? and how big is the boat??

​Technically there is no extra level of difficulty in using a brushless motor. You need a brushless speed controller, but this will be exactly the same to use as a brushed one, and on the motor side, there are three wires rather than only two, but they connect to the ESC in the same manner.

Ashley

[Charles OatesParticipant @charlesoates31738]

I'm quite surprised to see a brushless motor specified for a scale boat. It's true that they have made massive advances in recent years, but I thought this was mainly for speed and power. As Ashley says, tell us the size of the model and you'll get some good opinions.

Chas

[Malcolm FraryParticipant @malcolmfrary95515]

The motors didn't really need much improvement – its the controllers that govern how well they work. The big markets are flight, cars and fast boats. Scale boats usually have different control requirements, and are still better served by conventional brushed gear (usually, depending on the nature of the boat).

Not familiar with that picket boat, but reasons for specifying brushless could be

1- ensuring that the specification will be current for longer

2 – because it seemed a good idea

3 – more power for less weight. There is no reason why, but brushless and Lithium batteries seem go go hand in hand, and lithium batteries can store a lot more energy for a given weight which gives a longer run time.

At a recent show I went to, an owner of a scale tug was keen to demonstrate the fine control he had with his brushless setup in a tug. It might have been showtime jitters, but I eventually wandered off unconvinced.

[Colin BishopModerator @colinbishop34627]

The model is 38 inches long which is quite large and the original boat had a speed of 25 knots so it will need a fair bit of power to push it along to give scale looking appearance which is why John Parker was emphatic that a brushless motor would get the most from it.

Should work fine with NiMH batteries though instead of the more expensive LiPos. John's model runs on 7.2v and performance looks good from the article photos.

Colin

[Dave MilbournParticipant @davemilbourn48782]

A brushed motor has two connections while a brushless motor has three. Is this the 'complication' you refer to? If so you'll find that a brushless speed controller reassuringly has three wires for the motor connection. The connection to the receiver is identical.

You will be pleasantly surprised at the actual cost of a brushless motor unless you're used to buying your brushed motors from Internet suppliers at a quid a throw. Much the same can be said of the speed controllers. I use Turnigy and Leopard motors and the quality of both is remarkable. CNC machines are a huge improvement over Chinese peasants winding armatures on converted treadle sewing machines…

I don't have a model at the moment which has a brushed motor although I reserve the right to equip one with a brushed motor if I think it's most appropriate.

Go on – stick your toe in the water. John P certainly knows what he's doing so why not follow his guidance?

Dave M

[Yabbie1Participant @yabbie1]

Hello Peter,

Glad to hear that you are enjoying scratch-building from my plans.

You'll like the Picket Boat, it's a favourite of mine in operation and a straightforward build.

I first used a brushless motor in a scale boat many years ago, and never looked back. It's not just about power and speed, a low KV outrunner brushless motor will turn a large prop like the Picket Boat's very effectively without a gearbox. I've traded the harsh grinding of a gearbox for the turbine-like whine of a brushless motor and I think that alone is worthwhile, but it is the gain in efficiency that is most gratifying. I don't actually know how long the PB runs for on its two 7.2v NiMHs, because after two hours of zapping around I'm ready to go home! I estimate about 75-80% power provides scale top speed – it's always good to have a little extra in hand with a model. We are not unduly worried about weight with the round-bilge hull; I've tested the PB with the weight of an extra two batteries and it makes little difference to the performance.

You shouldn't have to spend a lot of money. Here in Australia not many hobby shops cater for boat models so I am more or less forced to buy on-line, and find that a brand-name brushless motor and ESC combination can be had for much the same price (or less) than a good brushed motor/ESC option (surplus specials excepted), certainly if you include the gearbox you'll likely need. Turnigy motors are OK, perhaps paired with an Mtronics or SJ controller if you don't trust the cheap Chinese ones.

That's my case for a brushless motor- but the main thing is, have fun.

Yabbie1 (John Parker)

[Peter Smith 24Participant @petersmith24]

Thank to all who took the time to give me sound advice.

I would like mainly to thank John Parker for listening to a slightly older gentleman's concerns. It is good of you to take time to do this. I will just need to bite the bullet and catch up with new and different methods,

One other question John, if you have the time, what grade of fibre glass do you use. I used Halford's but found it very stiff. Can you give me some idea of grade and even where is a good supplier.

Thanks again, Peter.

[ashley needhamParticipant @ashleyneedham69188]

Peter. A good point. I didn't know it until recently when I was purchasing such stuff for the next project, but you can get woven fibreglass cloth, as an alternative to chopped strand (the stuff you see in car shops) in very fine (like silk) up to quite thick grades.

​The big difference is that there is no binding agent in the woven stuff, so it looks and feels like cloth, and lays perfectly over hulls (for instance) even before being wetted with resin. It is the resin that melts the binding agent in chopped strand allowing it to become loose enough to get pushed about.

​You can also get (from specialist suppliers) slow cure resin, which takes up to 8 hours to go off, invaluable it seems to me as you can mix several batches to cover in one go and not waste so much. It also gets rid of the panic stations feeling after 5 mins when the stuff starts to go like jelly. This is what I will be using , and my hull will be of a decent size.

​The thickness of the mat is expressed as gsm….grams per sq metre. For a smaller vessel then some fine-ish stuff should be ok, several layers.

​I imagine it will leave a textured surface once covered in resin, but there again chopped strand will not be smooth either, and require a scraping of filler.

Ashley

[Dave MilbournParticipant @davemilbourn48782]

I buy that sort of stuff from these people **LINK** and have always been pleased with the price, quality and service. John P lives around the other side of the world so his supplier might not be appropriate!

DM

[Yabbie1Participant @yabbie1]

Yes, my supplier is in Tullamarine, Victoria, Australia – not really handy unless you're planning a flying visit!

Although I used epoxy resin on the picket boat, my usual preference is general purpose polyester resin which is cheaper and quicker. The glass I use is cloth (not chopped strand mat), a satin weave of 85gsm which doesn't fray and drapes nicely. For the outside two layers of this should be fine. Sometimes I use a heavier first layer of about 185gsm followed by a second of the 85gsm if I want more protection e.g. for a tug. A final fill coat of resin optionally mixed with filler (e.g. micro balloons) fills any remaining weave and provides the thickness needed for sanding smooth without going through to the cloth. Speak to your suppliers, they should understand what is needed.

Something I forgot to mention about brushless motors – you don't have to solder up those fiddly suppression capacitors because they're not needed. That makes the installation less complicated in my book.

Yabbie1 (JP)

[harry smith 1Participant @harrysmith1]

Hi All

I cruised around the Hobbyking website at some of the brushless motor available!!!

The number of motors is amazing!!!

The information on a lot of them, you can get the right size and rpm required for all types of boats.

The price on these are cheaper than brush motors( in Australia) and the ESC's are better.

We use the car ESC's which handle 2 to 4S Lipo batteries and are electric fan cooled, great for slow running.

Generally the brushless motors do not require water cooling, except with high speed motors.

Harry

[Mark Jarvis 2Participant @markjarvis2]

Hi Peter, the cloth and resin i use are from a company in Stoke on Trent, called Easycomposites, they have a web site of the same name, also a lot of how to do videos, they sec the resins and hardeners for the layup time etc, if you are close ish, they have a trade counter and are great for a chat to explain what you want to do

Regards

Mark

[Paul TParticipant @pault84577]

Dave

On the subject of Chinese peasants and their sewing machines you might find this interesting Link

Paul

[Dave MilbournParticipant @davemilbourn48782]

Paul

"Comprehensive"? Certainly – a huge exercise in data collection and presentation.

"Interesting"??? Didn't you hear the "thud" as my head slumped forward and hit the keyboard? Only for people who also bottle railway smoke, collect seaside pebbles or attempt to discuss the length of your intestines with total strangers. **LINK**

DM

[Paul TParticipant @pault84577]

Dave

Kenneth Williams was a much underrated actor and was totally wasted in the later Carry On films, the 'secret code' language in the Julian and Sandy sketches are just as funny today as they were in the mid 1960s.

Getting back to where things are made…these days it seems that all roads ultimately lead to China even products assembled in Europe have component parts from China……that poor peasant with his treadmill must work very hard. But as I found out recently some very high quality products are also produced in China which only goes to prove the old adage of 'you get what you pay for' or in my recent experience least what you specify.

Paul

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