Choosing electric motors and RC gear

[al mclauchlanParticipant @al-mclauchlan]

I’m effectively new to this hobby not counting the crude, straight running, small scale frigate and submarine models which I made in my teens.

I am currently working on a Type 42 Destroyer at 1:150 which works out at nearly 840mm long with a maximum beam of 95mm and a draught of about 30mm. I am guessing it will weigh about 1.5 to 2 Kg.

I’m still in the design stages at the moment but I want to spec the components I need so that I can design them in. I have a couple of Mabuchi RE 280 RA 1.5-3v motors but I’m not sure if they will have sufficient power to propel the model at a realistic scale speed. I’m also unsure of what to install in the way of RC gear. I want to control rudder and speed but would like to keep things compact, preferably in one watertight compartment. I’m not really sure where to start so any suggestions would be appreciated.

[Colin BishopModerator @colinbishop34627]

Hi Al,

You will need a bit more than 280  1.5 – 3v motors. A hull of that length and beam is a bit between sizes when it comes to brushed motors. You might get away with the the 280 3-6v version for scale speed while the efficient 385 next size up could be a bit heavy. An alternative would be small brushless motors which would be more efficient and lightweight. Ashley Needham on here would probably be able to suggest a suitable combination.

Do you want independent control of the motors? One speed control can control two brushed motors but each brushless motor needs its own controller whether you want independent control or not.

As far as Radio is concerned, there are a lot of reasonably priced multi channel sets available at not much more than the cost of a basic two channel set – check out Howes Models.

Home

As a bit of a newcomer have a read of this article which, although a bit old now, covers all the basics you need to know.

But I don’t understand Electronics!

Probably the biggest potential issue you will have with a Type 42 at that scale is ensuring adequate stability. There will be a lot of topweight for the hull size and length/beam ratio which can affect both static stability and the ability of the model to resist the effect of the wind on the superstructure.

Colin

 

[ashley needhamParticipant @ashleyneedham69188]

Hi Al. Independent motor control will not be necessary as with twin props and rudders you will have enough oomph to turn easily.

Two for instance speed 280 motors will have enough power but will be revvy and probably not turn a big enough prop. 385’s would be great and I would have thought you will have the weight allowance necessary to carry them.

Twin brushed motors can run off the same ESC. Unlike fitting two brushless which will require 2x ESC.

Are you building from a plan or designing it yourself? If at all possible, making the hull that much deeper would be sensible to increase the draft and you will have much better stability as you can fit more ballast.

Sticking lead strip (or whatever) UNDER the keel is a good ruse on destroyers and so.on as it gets the weight as low as possible. I would also be fitting oversize bilge keels to dampen rolling.

Ashley

[al mclauchlanParticipant @al-mclauchlan]

Hello Colin and Ashley,

Thank you for your advice and links. I can see I have quite a lot of homework to do! I don’t need independent control and one ESC is preferable to two which means sticking with brushed motors.

It is to my own design and a little too progressed to do much about the draught at this point. I’m also reluctant to do much that compromises visual accuracy. However, I’m aiming for a very lightweight 3D printed hull design which will be very thin walled (0.4mm) with even lighter superstructure. I’m intending to get the ballast right against the bottom of the hull. I might also consider a detachable weighted centre board if I cannot achieve integral stability. I don’t think I’ll really know until I’ve built it and can do some floatation testing.

I imagine the props would be about 25mm in diameter which would be slightly over scaled.

Thank you,

Al

[Ray Wood 3Participant @raywood3]

Hi Al

I would recommend lead sheet flashing laid in the bilges it works fine for stability, It works fine on my HMS Diamond, they are supposed to heel over in the turns 🙂

Regards Ray

[Colin BishopModerator @colinbishop34627]

Al,

25mm props should be fine.

The printed hull and superstructure should certainly help with stability. You might want to consider adding internal reinforcement with balsa strip to maintain rigidity though. It is often necessary with styrene hulls which are generally a bit thicker than what you are proposing.

I have no experience with printed hulls – are you satisfied with the impact resistance should the boat ram something or be rammed?

A detachable weighted centreboard may be needed, it was for my RC conversion of the Revell Queen Mary plastic kit which is 880mm long, 100mm beam and 30mm draught. Ovbiously the hull is fuller than the Type 42 and can carry more weight and it has a high flat superstructure. I found it was pretty stable in the bath without a keel but very prone to listing with the slightest force against the side so a detachable keel was essential although I leave it attached.

Power is two of the low voltage 280 type, geared down with pulleys to increase thrust and driving 20mm 4 blade propellers. Performance is on the lethargic side, OK in calm windless conditions but not really adequate for anything more. It really needs more powerful motors. If your Type 42 can accommodate the weight of the 385 motors in direct drive then that would be better. You can save battery weight by using LiPo cells rather than NIMH.

I would suggest you make provision for mounting an external keel by fitting threaded brass inserts into the bottom of the hull which will allow you to experiment.The centreboard also helps prevent rolling. My keel is made up of some spare door spindles from the bits box. A couple more are directly attached to the hull.

Colin

 

[al mclauchlanParticipant @al-mclauchlan]

Hello Colin and Ray,

Thank you for your replies.

I was thinking of using the powdered lead ballast you can get for weighting golf clubs but lead flashing would be more economical.

The Queen Mary 2 looks great. I’m not sure I’d be trusting those swans though! The Hull dimensions are pretty similar to my Type 42 but I would have thought you would have more topweight with all that superstructure. The Type 42 hull is quite full bodied in comparison with some warship designs so I’m hoping It will be large and light enough to get sufficient ballast low down with the weighted centreboard as a further measure if necessary. I will design in locating mounts for this in the hull print.

I think I will go for the 285 motors but I’m not sure at what voltage I should be operating them. The Howes site lists them as 4.5 to 15 volts.

I’m reasonably confident that the hull will be strong enough to withstand everyday knocks. It’s a bit like the real thing with a framework under the skin although it’s all printed together but in 5 sections .  The bow test piece I have done seems pretty rigid. I won’t really know for sure until I have built the whole thing though.

Some images of progress to date.

Thank you,

 

Al

[al mclauchlanParticipant @al-mclauchlan]

Forgot this view.

[Colin BishopModerator @colinbishop34627]

Al,

The swans appeared unexpectedly after I had launched. I just stopped the boat and hoped for the best!

I assume you mean the 385 motors? That’s a good price from Howes. The case actually says 6-15 volts. They run fine on a 7.2v NiMH pack or a 2S (7.4v) LiPo battery. The 25mm prop should be no problem. As you probably know, it is possible to get skewed props as fitted to modern warships. e.g.

https://www.cornwallmodelboats.co.uk/acatalog/R170-M4-p1.html

You are right that the QM2 will have a heavier superstructure but the hull block coefficient is much greater than for a warship so there is a lot more buoyancy to support it. In the bath without a keel it seemed stable enough but only a very small effort was needed to make it list to one side which did surprise me a bit. I put that down to the shallow draught which doesn’t give much of a righting moment. The non continuous 1mm high bilge keels are useless in stopping any roll. Those on the Type 42 might help.

You will just have to see, but building in provision for a keel will be much easier at the design stage than trying to add one afterwards! Some of the initial internal ballast will need to be removable if you fit an external keel of course. There is one other trick worth remembering which is that water is transparent and rarely completely flat so you can get away with the actual waterline being a few mm deeper than the painted one as the latter will still be visible most of the time. Every little helps!

You are undertaking a fascinating project so do keep us updated on progress.

Colin

[al mclauchlanParticipant @al-mclauchlan]

Hello Colin,

I did mean 385 motors and I will order a couple to get started. I also had a look at RC sets on the Howes site. The one they recommend for boats is a Carson Tamiya reflex 3.1 but it is out of stock. I think I would have to buy an ESC in addition to this but it includes the battery pack. Would I just need the one battery pack to run everything including the 385 motors or do I need to have a separate power source for the RC equipment? I read the John Cundell book and the article on electronics that you recommended but I’m still a bit hazy on these details and I really want to tie all this down before going further so I know what weight and volume of gear I am going to have to design into my hull.

I really appreciate your help with all this but please don’t hold your breath because I feel it will be quite a long haul. The CAD drawing I began as a teach myself 3D project about a decade ago and I had originally intended to use it to generate 2D components to fabricate a hull but the advent of more accessible 3D printing over the last few years has led to a change in direction. I have still not drawn any of the fittings/detail work and but I can see that others have done this at different scales so I may see if I can buy CAD or print files from somebody else to speed up the process.

I don’t actually know what a skewed prop is but the Type 42 has 5 bladed props. I do have a CAD drawing of a propellor which I can probably adapt to get what I want although it would not be as durable as a brass or nylon one.

I will keep you posted.

 

Al

 

 

[Colin BishopModerator @colinbishop34627]

Most ESCs these days are fitted with a BEC (battery elimination circuit) which provides a suitable power take off for the receiver regardless of the battery pack voltage and avoids the need for a separate battery.

So yes, one battery pack, one ESC and two brushed motors will work OK. The ESC output is simply split between the two motors.

The Carson radio looks expensive for that it is. One of the 4 channel sets such as the FlySky is better value even if you only use two channels but there are others on here who might have some suggestions.

By ‘skewed’ I meant the scimitar shaped blades which are usually fitted to modern warships.

Colin

 

[Dave ReedParticipant @davereed72029]

I agree with Colin about the radio, I use a Flysky FSI6X myself and like it. Up to 10 channels available for additional functions and loads of other features you may find useful in the future.

One thing to be cautious of with a stick radio is that some don’t have a centre return on the throttle. This makes reverse a problem (they’re intended for aircraft with no reverse gear). There is a kit available for the Flysky to add the centre return for around £4.

Dave

[John W EParticipant @johnwe]

hi ya Al and welcome to the forum and model boats

I am surprised nobody has pointed you in the direction of a couple of items which may help you along your way.

First one there is abook ‘Modern Combat Ships 3 – Type 42 – by Leo Marriott’ and these books do often pop up on Ebay and they are a little gem.   There are a lot of onboard photographs/history regarding these ships.   You may already have this – not sure.

Second one – there is a Model Boats Magazine – December 1975 and it should have a free plan in it o for a Vickers Vedette Warship.   Although, it is not the same class warship – it is of the same size and similar scale to the one you a proposing to build.   The reason I mention this is – you will be able to use the motors/prop shafts/rudder set up – to give you some idea of what to use.   Although this one is made from balsa wood; it will also give you some ideas of how to keep superstructure etc. light in weight, to stop the ‘top heavy attitude’ of these type 42s.

I have built a 1:96 scale model.   I used Jacobin plans as my base – but – sadly at this time – they seem to be difficult to find (unless you can find them on an auction site).

My build is on Mayhem Forum, under the topic HMS York type 42.

As far as radio gear goes, I use a 6 channel on mine.  This one is the old Sanwa 40 mghz and bascially the channels go – 1 channel for rudder steering and I have an ACtion speed controller plus mixer on another channel.  Radar and lights on other channels also the guns on another channel rotating and also on a separate channel the missiles.

I am not sure what else you would like to operate on your model, but, the old saying is keep it simple and good luck with your build.

[al mclauchlanParticipant @al-mclauchlan]

Hello Dave and John,

 

Thank you for your posts. I have had a little look at some of the other sets including the Flysky and I will probably go for one of these. I only want two functions, speed and rudders but at a push would even settle for rudders alone since I only really want it to come back! I wouldn’t mind a rotating radar but would probably make this independent. My main issue at this stage is sorting out the gear I want to install because I can then go about designing it into my hull at the CAD stage before I begin printing anything. I don’t really want to have to chop and change too much later.

Your HMS York model is fabulous. It looks like a plank on frame hull as well. What fantastic workmanship! I’m probably well stocked for reference on Type 42’s as I already have the Marriot book, the Jecobin Plan of Glasgow as built and hundreds of photos and drawings from trawling the net. My CAD model is my own plan derived mostly from photographs with some reference to the Jecobin plan and other line drawings. I’m doing a Batch 1 as built because I prefer the clean lines of these ships early in their service before the various modifications and upgrades which I think gave them a somewhat cluttered look later in their careers. Each to ones own! I’m reasonably confident that I can construct the hull and superstucture through a mixture of fabrication and 3D printing and I will probably 3D print many of the fittings but I haven’t even started to draw Cad files for these and that is a lot of work so I will try to source from elsewhere.

I was looking at your rudder installation as this is a bit of a conundrum for me. At 1:150 there is only about 20mm or so from the underside of the hull to the quarter deck. I haven’t been able to find a rudder post assembly small enough to fit so I am thinking that I may just create my own with brass tube but with the rudder post protruding right through the quarter deck with the tillers visible above the deck and the control rod running through the bulkhead at the front of the quarter deck and into the main hull. I would not have to worry too much about water ingress through the rudder post as they would not be open to the inside the hull. Just a thought but another feature which I would like to design in.

Sometimes I still think it would be much easier to stick to the straight runners of my youth!

Here’s my HMS Eastbourne in the bath a few years ago. Very crude by your standards I think!

Thank you, Al

 

[Richard SimpsonParticipant @richardsimpson88330]

There are plenty of alternative arrangements for a twin rudder operation.  This is a very simple twin rudder set up I fitted to a Revel plastic kit conversion to a surface running RC model, which is quite a small arrangement.

The wire and sleeves are RC aircraft items for operating control surfaces but lent themselves to this project very well.  I kept the linkages the same distances apart from the servo horn to the tiller arms which gave just the right amount of rudder movement and the model, even with the scale rudders fitted, is surprisingly manoeuvrable.

 

 

 

 

[Colin BishopModerator @colinbishop34627]

As Richard says, the rudder servo can be mounted in the middle of the boat where there is more room. This reduces the vertical space needed at the stern where there may not be room for a servo but you should make provision for occasional access to the rudder heads for maintenance. Never install anything that you cannot reach afterwards for maintenance.

If you look carefully at the image below you can see the outline of a hatch which gives access to the rudder head. It is not normally opened but if there is a problem with the rudder then it can be removed for repairs.

Colin

[ashley needhamParticipant @ashleyneedham69188]

The type 42 has a big flight deck, which could be made to be entirely detachable giving no access issues. If you made a watertight bulkhead just under the hangar then any water slopped in the stern will not travel down the rest of the boat.

Honestly, adding 15mm more hull depth would not notice at all and you will gave a much better margin for ballast. A scale model is fine, but if you want to use it on the pond with carefree handling, some changes need to be made sometimes to reflect that mass and weights do not scale the same.
<p style=”text-align: center;”>I too have a 1:96 batch 2 T42, using a commercial fibreglass hull,  and have no stability issues despite that it does seem to be light despite its 57 inch length. All the lead is sheet and lays on the floor of the hull.but..it is much larger than yours.</p>
I do have decent size bilge keels though.

Ashley

[John W EParticipant @johnwe]

https://www.modelboatmayhem.co.uk/forum/index.php?topic=65976.0

 

Hi there, if you have a look at the above link – don’t forget to see it properly, you will need to be a member of Mayhem, this is easily done.

The guy on here has used a lot of 3D printing to re-build this model of a Type 42; it may help you.

To go back though to your problem with the rudders, these are quite easily manufactured from brass tube, as you are thinking; for the rudder tube & brass bar for the rudder post.

When I have made them, I tend to used 2 different diameter tubes; one tube fitting inside the other.  The 2 inner tubes are shorter in length, so that it creates a space in the inside the larger tube.  This allows for this area to be filled with grease and therefore creating a seal on the rudder post, when in place.

As far as access, it would be possible to secretly put a hatch in the helicopter deck, where the roundel landing pad is and underneath that, on the quarter deck, where the capstan is located in that area you will be able to put an opening there through into the main hull which could quite easily be sealed.

Are you going to build the type 1 with the rounded stern and the type AKE-2 aerials more commonly known as the double bedspread aerials.   I would like to see how this turns out for you – I know you can purchase pre-etched brass fittings for these aerials, but, I am unsure of the scale of them.

Last, but not least, are you going to build HMS Sheffield with the Micky Mouse ears on her funnel, cos I think that is one of the best lookers of this batch.

John

 

[John W EParticipant @johnwe]

Hi some pics

[al mclauchlanParticipant @al-mclauchlan]

Hello to all and thank you for all of your comments and suggestions.

The U boat looks great. It’s great what you can do with large scale plastic kits. Regarding the rudder set up, I was primarily concerned with creating watertight rudder posts which would fit in the limited height under the quarter deck. As I mentioned earlier, I was considering running brass tube right through the quarterdeck so that there would be no possibility of water entering the hull through capillary action but, John, the tube within a tube is a great idea and means I will probably be able keep the rudder posts and tillers concealed under the quarter deck. I may also follow your advice regarding access.

I still think I am beyond the point at which I could increase the draught but I am now considering increasing the scale to 1:120 which I can do by simply rescaling my CAD drawing which would add another 200mm to the length and nearly 25mm to the beam. I would gain more hull volume and the superstructure would become proportionally lighter with no significant implications for the print process. I could also oversize the bilge keels and stabilizers and I think I will make these removable so that I can experiment.

Thank you for the link to the mayhem thread on Coventry. I had seen this previously but will give it more detailed scrutiny. I am building a Batch 1 but I’m not sure which one. I am almost thinking in terms of a builders/publicity style model, possibly with less detail but incorporating features from different vessels. I kind of agree that Sheffield was the best looking without the STWS platforms and the deck edge stiffening but I’m not sure about the Mickey Mouse ears or the bulging main mast. There is a great picture of Newcastle on builders trials on the jacket of the Marriot book in grey overall with no deck edge stiffening or pennant number. I do like this look.

Thank you, Al

 

 

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