Fit out for Minotaur

I am about to start on the Admiral's Barge - plans from Marine Modelling back in 1989.  I will be using a two channel Futaba radio to control the motor and rudder and I'd be grateful for advice on what motor and ESC to look for.  The model is 31" long so quite a heavy boat.  It is certainly not going to need speedboat speed! I think I've worked it out that I need an brushed motor - 6v? -  driven by ordinary NiMh rechargeables rather than brushless and LiPo batteries.  But there is such a range of motors that I'm a bit lost and in addition I don't know which make and model of ESC would give forward and reverse and be compatible with the motor.  I assume it should use BEC technology?  I should add that I've read Dave Milbourn's very helpful brief in Model Boats but what I'm after is specific recommendations for the bits I need.  Everybody has to start somewhere!

Excellent build to start a blog with here   get posting!

in regards to running hardware and electrical...

models 31" long so to be honest won't be that heavy!

there are two ways to go...

i'll start brushed motors first as that seams to be your plan.

boat can probably take easily a plain 40 or x40 prop ( x40 will make boat go faster and the incress of amp draw)

Suggest plain 40 prop, on a standard 540 motor with an mtronics 15 amp ESC plug and play, no messing around with setting up start and stop postions!. ( forward and reverse with built in BEC) as power with either a 12v slimline Lead acid battery or a 7.2 or 8.4v rc car pack. ( recommend 8.4v pack just for the extra RPM)

http://www.cornwallmodelboats.co.uk/acatalog/mtroniks-viper15.html


That will get the boat moving at a reasonable over scale speed for about 20-30mins on the rc car pack or if using a heavy Lead acid, upwards of and hour +.

you can change the motor to a 600 size with the same size ESC and battery option. ( if you do suggest swapping to the X40 prop) but battery time will be reduced. ( suggest graphner speed 600 8.4v, there is a 7.2 but may as well go 8.4v even if you run a 7.2v pack) 

http://www.cornwallmodelboats.co.uk/acatalog/graupner_3301.html

That setup will cost you around £30 with prop (excluding battery pack) £10 for the motor £20ish... for the esc ( varys where you buy it)

If you want to go like a bat outta hell and 31" boat with either setup will be fast regardless of weight ( as long as its not over 15kg!)

then you can go brush less.

I'm currently building a boat of similar size ( its a cruiser too ) which runs a 1500KV brushless outrunner ( made by overlander, only true british made motor that i highly recommend even tho a bit pricey), and a 30 amp watercooled ESC on a x40 prop, and running on a 3s Lipo. (11.1V) 

Warning here tho many brushless ESCS don't do forwards and backwards easily even with program cards  ( no matter even if the say they do!), so take this into account that your model may only ever go forwards with this setup!

suggest reading the below linked build as it contains videos with proof of the running ability's) 

https://www.thercmodelboatforum.com/t1044-aero-naut-jenny

that setup will get that boat flying!!!

cost for that setup will be around £25 for the motor and £30 for the ESC, you will need to add water cooling to the boat to ensure the esc dose not over heat!

The lipo price varys, (check out hobby king for their selections) you want a lipo that is 3S with a discharge rate of at least 30C, size of battery around 3000-4000mahp but you can get them starting at £15 up to £50! (excluding a charger)

get back to us on the prop size you will be using regardless of my recommendation ( as a larger or smaller prop may be required depending on your build and i'll suggest something from there, but i expect a 40mm prop will be the best way to go giving you options!) 

Choice is yours on what you want to do, scale speed i do suggest brushed motors ( first set of suggestions) as that will give you decent get out of trouble speed and you can throttle back for more cruising/scale appearance.

Talking on appearance you can add a water cooling coil to 540's and 600 sized brushed motors if you want the water cooled effect on the boat its not only more realistic but also practical use as brushed motors do tend to get hot after longer runs at lower speeds. 

Brush less motors tend to like going fast rather then slow so do take that into account before deciding.


RR

Many thanks for this very prompt and comprehensive reply.  I'm new to this so please excuse my dumb questions!
I don't want unrealistic high speed on this admiral's barge so I think the 540 brushed motor sounds right.  I assume a 40 prop means 40mm diameter but the prop shown on the plan has to clear the hull and seems to be only 35mm.  Will that be obtainable and will it do? 
Thanks for the link to the ESC which seems just what I need.  
When I google 7.2v car pack I get a great variety of results.  Can you point me at what you are recommending?  And I assume I will then need a special charger?  
Thanks again.

40mm prop = 40mm dia so your correct.

a 35mm prop will be ok and i mean that loosely!

There should be enough room when inserting the shaft to clear the hull for a 40mm prop.

I really do suggest putting a 40mm prop on the shaft when installing it to ensure it clears.( u may have to tweek the angle to make it fit slightly as long as it clears 2mm from the hull it will be perfect.

there is nothing worse then building a model and finding you have to start changing the electrics because something is fixed and cannont be altered.

If you fit a 35mm prop and don't have enough clearance for a larger prop then you could find the boat under powered, the smaller prop may cavitate with the RPM more then give you thrust!

This way if the boat can fit a 40mm prop standard, if you find its over powered or you struggle to keep it under control you can drop the prop to a 35mm to reduce its speed.

I run cruiser/sport boats in the 500mm length range with 35mm props always on M4 shafts. . Anything over 500mm instantly get 40mms unless they require 3 or 4 blades to which i change the electronic setup to match.

I would suggest a M4 prop shaft with a M4 Plain 40 prop ( left or right hand it don't matter for single prop boats, you can just flip the power cables to spin prop correctly if it turns back wards) 

then the 15amp mtronics esc with your choice of 7.2 or 8.4 battery.

in regards to motor...

I would still recommend the 600 ( and at £5 you cant knock the price!) this will give you the ability to get out of trouble should the worse occur, its easier to have more power then you need and just throttle back for normal running, then be under powered and buggered if anything goes awol.

The 600 will also have enough torque and power to propel a heavy boat  ( should you be worried) with NO issue what so ever! in comparison i run a old boat nearly 5 foot long made entirely of 3/8 marine ply it is easily 8 or 9 kg in dead weight, and use a 850 torpedo motor with a 40 amp esc and that thing rockets!


as for battery's i will only recommend things i have brought and run with, i've mostly swapped to lipos now as they are in the same price range for my needs, but these i own and have run for several years with out issue..

http://www.componentshop.co.uk/7-2v-4600mah-sc-nimh-battery-pack.html?___SID=U

not overly pricy either but the yare smacking the low end lipo prices.

and the charger for those is here 

http://www.componentshop.co.uk/600ma-smart-charger-for-7-2-8-4-9-6v-battery-packs.html

both battery and charger use tamiya style male/female plugs

there is no reason why you cant run a lipo which would be a 2S at 7.4V  but you will need to make sure you get the correct plugs and chargers can be a bit tricky and also some of the 'cheaper' lipos still explode while charging if your not 100% cautious!

Thanks again but you did not comment on my battery query.  When I google 7.2 v car pack I get a wide range of results.  What do you recommend and will I need a special charger?

And you say go for a 600 motor so do I just tap that into eBay or is there a particular motor that you have in mind that is compatible with the mtronics 15 amp ESC that you have recommended?  I'm nowhere near a specialist shop where I can ask questions so I am going to have to pick something off the web without really knowing what I'm doing!

Apologies - I see that you did cover the battery issue!

my bad i updated my post when i saw i missed the battery question, i tend to just mod my posts then keep reposing cos i forgot something ( i seam uber professional that way) 

i put the 600 motor and ESC link on the first post i replied to. 

just scroll up

Thanks again for you patience and very helpful replies.
My shopping list is therefore:

• Futaba 2 channel Tx and Rx (got it)
  
• 40mm diam prop and shaft
  
• Graupner Speed 600 brushed motor - but it seems to come without capacitors to cut out interference. Does that matter?
  
• mTronics 15 amp ESC with BEC and fwd/reverse
  
• 7.2v 4600Ah NiMh battery which powers the motor and, via the BEC circuit in the ESC, also powers the receiver. I assume the BEC feeds up to 7.2v to the motor and a lower voltage to the Rx
  
• 600 mA smart charger from Component Shop
  
• A switch to go between the battery and the ESC
  

If that lot is the right package then all that remains is to build the boat!

I'll get back to you in a year or so's time - thanks yet again.

Ensure your prop shaft is M4 size. recommend JP stainless slimline if you can still get them, avoid cheaper shafts with plastic bushings nothing but junk and will just up your motor load and decrees your performance and run time.. 

http://modelshopleeds.co.uk/catalog/index.php?cPath=38_144_292 

Range of prop shaft lengths available. and only ones i use for all models!


The capacitors on the motor are only needed should you have interference with the signals, usually noticed first off with the servo twitching, you can add those yourself later if needed. 

Futaba servo recommended as they very rarely play up with servo twitch, hitech servos are junk!

And you will not require a switch for the ESC/battery, the ESC comes with a switch and some cable length to mount.

However that said, i have heard many rumors that the switch on the ESC is for only used for powering the receiver. I cant confirm that as truth but when the ESC fires up all the lights come on indication the esc' current direction ( forward backwards or both lights on for neutral) so i expect its Bull ****.

You can if you wish add a battery switch. 

if you also wish you can add a 15ammp fuse between the battery and ESC which is a 2nd lvl of fail safe. the mtronics have built in protecting but its minimal. over loading the ESC is rare providing that you keep the motor in the AMP range of the ESC, however in case of a motor stall ( prop binds on weed) then you could face a higher amp draw resulting in the ESC burning up.

a 15amp fuse on the battery will STOP that issue before the ESC blows.

The ESC is simple to use, it will power the receiver unit via the connecting lead. the other cables on the ESC are for battery hook up and Motor terminals.

The esc also has fail safe for no signal which will stop all motion should the receiver not pick up your transmitter.

On another note if your building it post it as a blog, i'm sure we would all love to see!!

if not good luck !!

Thanks again - this has been so helpful that I have copied the whole thread into My Docs!

Following on from RR's comprehensive answer, I would suggest adding a switch between the battery and ESC. The switch provided does NOT isolate the ESC completely, and the battery will drain if left connected - I know from experience , and in fact the Mtroniks instructions do state this. Its not a rapid discharge so the other option is to disconnect the battery after a session. This is in fact what I do particularly as the battery needs to be removed for recharging.

Barrie

I did mention that this could be a possibility, but wasn't 100% on the truth to the rumor and in all fairness i never read the mtronic instructions that far, just needed to know when to push the button for throttle setup! 


To be fair tho this isn't a huge issue some of us carry a battery box for our day sailing, so the battery generally is not hooked up to the model until we are lake side and as Damien pointed out its easy enough to disconnect the battery after use.

Just watch that rigging!!!