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[Green Nomad]

Hello Everyone,

If you missed my first post describing my current build, then I will briefly recap here.

This is my first R/C scratch build, a 0.5m rough scale model of a 40' Lochin fishing sportsman.  Hull made of 2mm ply sheet on MDF/ply frame.

My question is. I am at the stage of ordering the electronics now and want to know if this selection is compatible and appropriate. I had sent a message to Cornwall Model Boats as I was ordering from them, but have had no reply as yet.

The package is:        Graupner 280 motor
                              Graupner 15 amp Navy V15R ESC
                              Futuba R152JE  2ch receiver
                              Futuba S3003 standard servo
                              Eco Power Nimh 6v battery pack

Any extra ideas or things I definately need to add, suggestions will be appreciated.

Nomad..

[john s 2]

Just my thoughts but.Motor seems a little small. Would a Mtronics Esc be cheaper? Also is it worth investing in a 2.4 Set? John

[malcolmfrary]

Yes it will all work together. 
The plug on the ESC might need a bit of trimming to fit the RX, it might not.
Like John S said, the motor might be small for the boat.  Very small.  Telling us what size prop you intend would help at guessing an appropriate motor.

[Green Nomad]

Thanks for reply John.  Priced the ESC at Cornwall Model Boats online for £22.50. Will look up about the Mtronics price. What size motor do you reckon then for a 1/2 metre length boat?.

On another point regarding the material I am using for the hull framing, MDF.   I have been searching for waterproofing techniques for this and have read a lot of negatives about using MDF. So I am considering changing at this stage to 3mm ply maybe doubled up as sandwhich, as I have not yet bonded all the frames etc together. Just take me a day or so to convert to the ply I think once I have bonded the sheets togther.

Lastly, with respect, what is a 2.4 set?,,, presume it is all that I need in one package.

Cheers Nomad...

PS, Just got the reply from  Malcolm, the size of prop is a 3 blade 30mm dia in plastic. Thanks for input.

[hollowhornbear]

2.4 Ghz new frequency no crystals and no frequency clashes at the lake side, read about the various types herehttp://www.modelboatmayhem.co.uk/forum/index.php?board=146.0 just look for 2.4g in the thread title
i use a spektrum dxi6 in my surface boats and love it, although there are cheaper sets.

[cos918]

Hi Nomad
A 280 motor is a little under power for a 0.5m boat witha 30mm prop.  I would be looking at a 380 or bigger. Your raido and ESC should be fine.
Other stuff you might need. Motor coupling , servo links for the rudder, fuse holder etc.

You are correct on ditching the MDF and going for ply.

John

[malcolmfrary]

Motor, I would go for a 385 for a boat that size, running on 6 volts, look for a 15 volt one.  Torque characteristics right, speed a bit more than adequate, but thats why there is an ESC and a control stick.  Rather than over working a smaller motor, this size will run cool, probably at lower current and thus give a longer run time.

[john s 2]

Just a thought but would you be better off using a gell (lead acid) battery also known as a pb cell? 6v is a standard rating and amps
also varie. A gell cell uses a jelly instead of acid, will work on its side and of course no acid leaks. a source is use in burglar alarms.
You could of course use a motorcycle battery again usually 6 or 12 v. There is a chance of acid spill. John 

[Green Nomad]

Further to everyones comments and suggestions on here, which I am thankfull,  I have tried to match up motors, ESCs, batteries etc.. I have been looking for full packages that include all I need, but still needing to match things together. I am a complete beginner when it comes to the electrics etc. Is there a shop or online order company that can mail me all I need in one package.,


I'm located in Oman, and I very rarely go back to UK., so all has to be ordered, I do belong to a aero modellers club here, but the gear seems OTT for my needs.

Any suggestions on good packages out there on the net..

Cheers Nomad.

[Green Nomad]

Hi All,

Have now decided on the package I am going to fit..

Graupner Speed 330 7.2v brushed motor linked with the Mtroniks Viper 15 amp brushed ESC, I believe having a BEC in built.

As for the power supply I was wondering on whether to have a Li Po 2 cell battery to keep weight down. What amp discharge would I be looking for with this motor and does it need to be max 15amp discharge with the ESC.?

What make of Li Po batteries are recommended?, as I am trying to keep the costs down also.

Finally, I have also toyed with the idea of getting a 2.4 Ghz Spektrum 5ch Tx/Rx, but again not sure whether this is dependent on BEC, and do I need a seperate power supply?

Any suggestions please?  GN
 

[dodgy geezer]

Finally, I have also toyed with the idea of getting a 2.4 Ghz Spektrum 5ch Tx/Rx, but again not sure whether this is dependent on BEC, and do I need a seperate power supply?
 

You can power any radio receiver from its own dedicated batteries, or from the main boat motor power supply. If the main motor power supply is not 5v-6v (which is what a receiver needs), it will need to be regulated to this voltage, which is the job of a BEC. You can either have a separate BEC, an BEC incorporated in the receiver, or a BEC incorporated in the speed controller.

I do not think the Spectrum DX5e receiver includes a BEC, but the Mtroniks Viper 15 does, so that's fine. I'm a little concerned to hear you talk about LiPo batteries - these are very powerful and very light, but will be damaged if they are discharged below a set limit. So they are usually used in conjunction with a speed controller which senses this limit, and cuts all power just before the limit is reached. The Viper 15 does not seem to have this technology, so you run the risk of over-discharging your LiPo batteries. People usually use LiPo batteries in conjunction with powerful brushless motors in practice, so brushless speed controllers usually incorporate this feature...

You might be interested in some of the cheaper 2.4Ghz sets (which are the coming thing in RC!). Two popular ones are very cheap - the Planet T5 and the Radiolink T4EU. Here are some reviews:

http://www.modelboatmayhem.co.uk/forum/index.php?topic=25779.0
http://www.modelboatmayhem.co.uk/forum/index.php?topic=27616.0

They are very similar - the Planet is more expensive, but, if you are not used to RC, probably the easier one to use ...

[malcolmfrary]

You can either have a separate BEC, an BEC incorporated in the receiver, or a BEC incorporated in the speed controller.

I've yet to see any figures for RX BECs, and have always assumed that they were intended for buggy use, where 6 cell NiCad packs were the norm, so applying a higher voltage is probably not a good idea.  If you just regard the "BEC" lettering on the RX case as ornamental marks, and get the nominal 5 volt receiver power from either its own battery or a BEC, either separate or incorporated into the ESC, there will be no tragedies.

[dodgy geezer]

I've yet to see any figures for RX BECs, and have always assumed that they were intended for buggy use, where 6 cell NiCad packs were the norm, so applying a higher voltage is probably not a good idea.  ...

You're probably right - my Futaba Attack Rx is specified as 4.8v - 8.4v (built-in BEC). I included the statement for completeness - of course, as always, one should check the specs of each electronic item you use to confirm that it is acceptable.

[Netleyned]

The GC receivers in my yachts are sometimes run from 4xDuracell AAs well over 6V when fitted with no ill effects

Ned

[malcolmfrary]

The GC receivers in my yachts are sometimes run from 4xDuracell AAs well over 6V when fitted with no ill effects

Ned

Thats because it was designed to run off four newly bought AA dry cells and survive the voltage.  Plugging some of the new generation extras that are built around PIC chips and the like will fry those circuits, careful reading of instructions is needed.
Most portable electronic devices are designed around a nominal voltage, they will still work to a lower voltage, like when the battery voltage drops, they have to survive a fully charged battery of the nominal voltage.  There is some latitude in the supply voltage, but deliberately running to one extreme or the other is not a good practice.