Old beginner.

[Ben KenobiParticipant @benkenobi30507]

A beginner that isn’t really a beginner

[Ben KenobiParticipant @benkenobi30507]

OK I am not a noob, build my first boat back in 1968, biggest build was a Smit Rotterdam in 1981 – I still have it.

And that's why I'm here, the boat was stored whilst the brood was raised, it hasn't faired the wardrobe, little fingers and 2 house moves unscathed.

So I'm getting back into my model boats with a full refurb of Smit, this is planned for over the winter. Leaving it in the wardrobe any longer somehow seems wrong given that I've spent hundreds on multirotors and helicopters, so I'm playing catch up with what is available motor and control wise for scale boats.

One of the cock ups I made when building was the prop tube alignment, my propeller centres are too high and aren't centered in the nozzle, the original propeller fits and doesn't foul but it just ain't right so I intend to pry the tubes free and redo them, I also intend to replace the shafts and motors with more 'modern' technology,

The model will run 4 bladed 50mm Kort propellers such as the Raboesch items, I'd love to go to variable pitch but it doesn't seem to exist even now. The real Smit Rotterdam (ex it's now under a Greek flag) runs 4 bladed variable pitch propellers and always has but getting hold of such details back in 1981 wasn't near so easy as it is now so consequently the propeller size and profile is not open to debate.

My preference is to install two brushless low Kv motors on soft / suspended mounts because I want this to be as quiet as technology permits. I'll drive the shafts via flexible kardan joint or something similar. I am not going to fit a gearbox, the ones that I've seen are noisy and crude. I intend on 2 reversible ESC's, one per motor, I also plan to find a pump to operate as a bow thruster, I installed tubes back in 1981 with a view to using a windscreen washer pump from a car – but they are old, hard and need to be replaced. I haven't decided whether to run 12 or 14 volts yet, also haven't decided on type i.e. gel, lead acid or lipo.

Regrettably back when I built it the LED technology was nowhere near where it is today and retrofitting decent lighting just isn't an option.

I'm not a dummy, I have several flying models, I operate a Taranis X9D (OpenTX), I intend to use a smart controller such as an APM / Pixhawk but reprogram it for marine use but will likely use 'ArduRover' initially since it won't know the land is actually water.

So I'm looking to pick everyone's brains, what's out there motor and controller wise suitable for 'scale' models that is '21st century', in particular

Soft mounts for motors – zero vibration transferred into hull

Low Kv brushless motors – able to run a prop and push the boat at 'scale' speeds with minimal noise.

Propshaft and propeller technology – Propeller must be Kort profile and 50mm

Propshaft / motor joints – low noise and minimum vibration

Model 'ballasting' i.e. tanks that can be flooded or pumped out to trim the model – this model takes a lot of weight to get to the waterline.

Bow thruster 'pumps' maximum space between thruster faces (hull width) is 25mm

Something that can dissolve epoxy such as Araldite – I've tried all sorts from Acetone, nitromors (the original nasty stuff) to Isopropyl Alcohol – nothing is touching it.

Edited By Ben Kenobi on 12/09/2014 12:33:21

Edited By Ben Kenobi on 12/09/2014 12:34:47

[Gareth JonesParticipant @garethjones79649]

Hi Ben,

I have found the best way of removing a prop shaft fixed in with araldite is to remove the drive shaft and then stick a soldering iron down into the end of the sleeve and leave it to warm up. The araldite will soften with the heat and the sleeve should pull out after a bit of twisting, hopefully without any heat damage to your hull. Mole grips are a good way to get hold of the sleeve without burning your fingers.

As regards a good quiet brushless motor, I am afraid I can't help. The ones I have tried so far are quite noisy, particularly at low speed but it may be possible to overcome that problem with a different speed controller.

Gareth

[Ben KenobiParticipant @benkenobi30507]

I can't easily get an iron anywhere near, from the prop side there's a plastic support, from the inside getting an iron in will be a challenge but potentially possible. I've been trying the chemical solution first but it does seem that heat is the most likely to succeed. When I built this I pinned the wood but used things like epoxy on fittings and the entire hull is impregnated with fibreglass resin. I'm just trying to do the least amount of 'collateral' damage.

I've seen a few boats now this year and been unimpressed at the 'propulsion' technology progress, still using brushed motors, high speed and small 'out of scale' props, generating cavitation and water disturbance that destroys the whole 'scale' feel not to mention the unrealistic speeds – I really can't stand the noise, I hated the noise Smit made before going into storage. The speed controller I had combined with the brushed motor did not permit a really low rpm, if you tried a gradual start the motor just wouldn't until you had quite a bit of stick on it – I know that a gearbox is probably the answer but all those I have seen are straight cut gears, noisy and not of an acceptable standard, I don't fancy belts and no longer have the tools to make my own.

I've always thought that the hard mounting the motor as in fixing it directly to wood inside the hull is part of the issue since it uses the entire hull as a sound board, bit like a guitar chamber it amplifies any noise.

There are some nice quiet brushless around, but not necessarily very low Kv, perhaps I'm to fussy these days but money and the patience of youth (or lack of) are no longer an issue so it's time to do it right by this model.

[ashley needhamParticipant @ashleyneedham69188]

Ben. I think things have moved on now. The mtronics ESC I have provides the very slowest start, even on a small motor.They do whistle a bit but again this seems to vary depending on the motor fitted.

A large reasonable quiality motor should be quiet enough, and a rubber type coupling as per Marks Model Bits is comletely silent. If you have good alignment then you should not worry about the hull being a soudboard. It is damped by the water in any event. If using a rubber type coupling then a rubber (inner tube) layer could be used between motor mount and boat, howeevr at low speeds this wont make a lot of difference.

I have several boats that are completely silent, without any special measures being used.

Mechanical means may have to be used to remove the shaft, and some time spent scoring and cutting with a scalpel may pay dividends. If the shaft was cut then possibly a heated iron rod (bit of brass) could be shoved in the tube to heat it up…a sharp tap with a drift completes the job.

gel batteries, no point in using anything else, you need the weight. I might even suggest a pair of 800 motors, ..powerful, slow speed, heavy, reasonable price.

Ashley

[Ben KenobiParticipant @benkenobi30507]

"I think things have moved on now"

That's what I was hoping, I look at the stuff I use on my helicopters, you could only fantasise about such things when I 'left' this hobby.

I looked at some motors with an '800' number – mfa Torpedo – there was an 850 too – this the same thing ?

How is interference handled if you use brushed – i could put a house sized capacitor on the motors it was built with and you'd still get interference, I'll keep them for nostalgic reasons but by todays standards they are poor – but then again so was my first car compared to the A8 that I drive now . .

I did read about some motors that could be tuned by altering the 'brush' timing – but aren't brushes a bit old school, I wouldn't consider them on any flying machine.

Whistling I can handle once the tops on you don't hear that, it's that horrid rumbling – like something isn't balanced that I hear on so many boats I detest, going to look for those flexible links. I was going to sit the motor in it's standard mount but then sit the mount on the same 3M pads that I use to insulate my flight controllers from vibration – although I have a ton of work to do before I get that far.

I now have some decent pictures of Smit in dry dock so I need to modify the Kort and prop tube supports totally. I'm going to need to mount the motors further forward at a much shallower angle than the Billing drawings recommend – the angle that the propeller enters the Kort nozzle is totally wrong and the propeller is too far forwards, needs to be further back in the 'centre' of the nozzle. I've already done some whittling with a stanley blade but it's too crude – a scalpel would be much better. Used to have an XActo with different blade shapes, long since been spirited away by the poltergeists.

I concur on the heavy thing, when I ran this before I had two 12 Volt 'alarm' batteries installed and I still needed lead – hence my question about trim tanks. Partly I'd like to be able to trim down with water then pump out simply because I did myself a mischief leaning over trying to haul it out the water 30 years ago – still remember it – this boat's really heavy when in sailing trim.

When I look at it now and realise that it took me 14+ months to build I'm saddened by how I've treated it – and that I didn't do a better job on some parts.

[ashley needhamParticipant @ashleyneedham69188]

Ben. MFA800 it is. This maxes at about 5000 rpm and 6A as opposed to 9500 rpm and 10A of the 850. A simple capacitor set on the motors will be sufficient for suppression.

Tuned brushed motors is for racing, generally speaking..an area taken over by brushless I would think now.

For a model such as yours, brushed motors are fine, and if you were to go for brushless, you would be on your own as to the choice.

I think it would be tricky to retro-fit water ballast tanks, Perhaps simply making the existing ballast easier to remove would be the thing, and fitting batteries once floating in the water..as i do with my Aircraft carrier. Much easier.

Ashley

[Ben KenobiParticipant @benkenobi30507]

There are so many things that 'experience' teaches, there are many things that I'd change now but many of them need to go back to before the deck went on.

I'll see what I can work out re the ballast, I need to remove about 2kg of lead from the bottom of the hull anyhow. May do some plaster castings between the frames and use those to create 'ballast' forms.

I'll explore the mtronics ESC too.

I can testify to the brushless in racing boats, a friend runs them – 70mph, 180Amp water cooled !!! – but his interest in boats is partly why I figured that I should dust off the Smit. It's certainly possible to find a brushless that peaks at 5000 rpm on 12VDC – but I'd have thought that even 5000 rpm would be way beyond 'scale' in performance terms. I seriously doubt that the real thing had a shaft rpm much beyond 750rpm – but of course the surface area of her prop blades was somewhat more than my model – density of water yada yada – hard to scale and get right – not sure I'm going to be able to scale a 170 ton bollard pull

[Mark Jarvis 2Participant @markjarvis2]

HI Ben

Having a set of ebay refurbs on the bench, the prop shaft is easily removed, heat it then with mole grips twist and pull to remove. Replacement with re-alignment is a little more difficult, just take your time, you sound like a seasoned modeller, flying alignment is a lot more critical than prop shafts!!!!!

Motors. Brushless motors are superb in the right environment, tugs aint that, good quality brushed motors have better running qualities at the revs we need. Big props are restricted to about 5000 revs by most manufactures, buy quality, Raboerch, or Propshop. Kort nozzles and the props must be carefully aligned together, minimal clearance. My Rotterdam has twin Johnson 600 motors, better quality is available but they perform well. 12v gel battery and twin ESC's, Raboerch bow thruster with 400 motor on 6v, all on 2.4mhz. the ESC;s are cheap chinese ones, nothing special, handle 50 amps forward and 20 amps reverse, £8 each

The remaining part of your questions such as LED's, Chinese supply is overwhelming, to much to choose from!!! my advice is don't go the brushless route, the quality of brushed motors, if chosen carefully is superb, look at the T motors from Mobile Marine 12 and 24v, look at the Americans their Portman motors, industrial motors are quite cheap, lots to choose from, not just "model motors". get the spec sheets and compare outputs etc.

Refurbs are easy now we have learnt the pitfalls, don't mistake technology for better.

Regards

Mark

[Ben KenobiParticipant @benkenobi30507]

I shall take all advice seriously, that's why I asked, my first task is to build a frame so that I can invert the hull and work on it, motors and such are a 'concern' because they impact on the re-alignment – and I know that the 500's that I put in this all those years ago aren't so good. I've already pretty much set my mind on a pair of Raboesch 50mm Kort propellers – I've yet to find any that are better.

I'd love to do the LED thing but there's no way I'm pulling the mast apart – couldn't get wires to the top anyhow, the flying bridge with the spotlights etc I may be able to do something with, maybe navigation lights too.

To be honest I want to get the hull side of things sorted first though – could actually sail it now but I've got fussy in my old age

I'd be interested to know how you got the bow thruster to fit, all my measurements say that none of the commercial offerings will fit – even the the Graupner or Raboesch mini's – and I'm not about to hack that part of the hull around unless I'm certain.

Seasoned modeller – I guess, I've made my share of models and mistakes, I just lost touch with the pastime for a long time while the kids were at home.

I'll try the heat thing – I have a nice little gas pencil that will get down there – just need to keep the plastic part in water to stop it getting melted I guess, I've looked for new ones in most of Billings lists but you don't seem able to buy the 'fittings' as a separate kit any more – not that I need a complete one.

[Mark Jarvis 2Participant @markjarvis2]

HI Ben

Last first, Billings have gone bust, any fittings you need will have to be bought separately. the kort nozzles if there anything like mine are easy to replace Prop shop, Mobile marine.

You mentioned the bow thruster, mine is the Raboesh mini, don't worry about the length, that is trimmed to size when fitted.

I cut the section from the keel to fit the bow thruster, after drilling out the hole, the thruster was fitted the the keel piece was epoxy and glass clothed back into place, inside and out.

Cut the prop tube near the area to be removed, the heat will be more localised, might even be enough to loosen the tube without more heat????

Regards

Mark

[Ben KenobiParticipant @benkenobi30507]

Well I have a lot of work to do in that area, I could do with loads more pictures. I have some but not enough.

Sadly I'll never get any of the boat unless they are old ones. It was beached and scrapped on 24th June 2014 at Gaddani beach in Pakistan along with it's sisters.

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