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[SteveJo]

Phantom build is progressing (pics at end) and now ready to sort the details of the RC installation.


The Billing 'instructions' show 2 x 3.6v battery packs (in series) mounted either side of the motor - I guess it keeps the CofG closer to the centre of the boat.


Other builds I've seen have a 6 cell (sub-c?) pack mounted in front of the motor which puts a lot of weight at the front.  One build has the pack mounted behind the motor which makes for a very long servo linkage to the rudder and puts a lot of weight at the back.


Does it matter or am I overthinking this?   


I could make up two 3.6v packs as shown - can't find anything ready made - but it's a bit of a pain.  Or am wondering if two AA based packs would work - appreciate you can't get the same discharge current but max speed isn't my priority.  Will try and measure the current taken under load and see how it compares to the AA specs.


Thanks





5 coats of Ronseal exterior varnish, trimline


Zpoxy finishing resin, fibreglass cloth, upol primer and car aerosol topcoat - varnish protected with tamiya masking tape

[malcolmfrary]

These days I would look for a 2S LiPo pack of similar capacity.  Smaller and lighter giving more choice of siting.  On a boat that should be fast, adding extra lightness always helps.
Back in the day, manufacturers instructions specified from what was available.  For instance, Graupners Lotse wanted a pair of 6 volt SLA batteries, one each side, but worked startlingly well with a 7 cell NiMH pack sitting on top of the prop shaft.  While following the instructions is usually a good way to get the right results, sometimes using newer kit can improve things.

[SteveJo]

Thanks.  Have come to realise lipo would have given me more flexibility but unfortunately have a non lipo compatible speed controller.


Have gone the over the prop shaft route for the 6 cell Nimh battery pack - cofg is around 35% - and will decide where speed controller goes after taking a look how it floats in the bath!  The battery mounting supports a bit of adjustment so hopefullly will be able to get the waterline close to where it should be.

[malcolmfrary]

They are all compatible - you just need a low volt alarm, very compact item, weighs little, inexpensive.  ESCs don't care where the electricity comes from, just as long as the source can supply the current wanted and the volts are in the right range.

[timgarrod]

mine take 2s 2200 ma batteries.

[RST]

May I propose something a bit controversial controversial and a very po-poo'd old fashioned approach these days but I did it twice myself last week as I don't really build kits or stick to plans much myself...

...So you know what the recommended set-up is.  If you have no batteries at the moment, you can still grab some AA sized dry cells which will be close-enough to NiMH cells.  Cellotape them together into a configuration and try placing them about the hull. If ou want to go LiPo, then google the specs, dimensions and weights and find something the same and try fitting.

Have you put the hull in the bath yet to see how it floats?  I'm working away from home, realised I only have a 1/2" deep shower cubicle (crazy -never seen that outside the UK, no wonder I mop the floor each time!) so I went and bought a cheap plastic box as a test tank.  I had some batteries, some other bits to represent other weights so I could move things around and see how my model floated.  I think I found a glass jar of herbs which was close enough for something -you get the idea!!!

I do not think you can do everything by prescription from the internet.  If you ask 10 people you will get 10 different answers, and almost no answers which suit you in particular, unless you want the security of doing what someone else always does, in which case there's minimal learning curve.
By the way, looks a fantastic job on the hull so far!  Very envious!!!!! Particularly varnishing which I detest.


Rich

[Onetenor]

Wasn't there some press about Abc 123 batteries some time ago which gave higher voltage and capacity. I can't find 'em now but IF you can they would seem to fill the bill from what I recall. May I suggest The Component Shop  catalogue a[size=78%]vailable return of post. You can peruse it for what you want or even have some made up into packs, I have some which I can't get to at present to give details. They are packs about 5/6" long and about 1 1/2" wide. They are Nimh cell packs of I think 7.4 v. They sit in the hull bottom either side of the motor and balance the hull evenly. Mine came with the boat but appear to be commercial packs.[/size]

[JimG]

Iirc the ABC123 batteries are either Lithium ion or Lithium ironphospate chemistry. They have a lower voltage than LiPoly ,, around 3.3 -3.4V instead of 3.7V. Their main pro was that they came in metal cases instead of a plastic bag so were much less prone to damage or catching fire if badly mistreated. Lithium Iron Phosphate or LIFe cells are still available and are often used as a replacement for NiMh cells in RC equipment, most receivers and servos can stand 6.6V from a 2 cell pack but not 7.4V from a LiPo.

Jim

[SteveJo]

Lots of interesting stuff thanks - forum is great for finding out about the stuff you don't know you don't know about - the unknown unknowns.


Had a brief play in the bath and although boat is a bit back heavy it's not too bad at all - by the time deck and cockpit are in will be pretty close.  Definitely learned that sealing around the prop shaft needs to be better!


There are some AA based battery packs that would work - unlike many sites this place specs max discharge
https://www.vapextech.co.uk/batteries/radio-control/4-8v-7-2v/7-2v-battery-pack-2500mah-nimh-instance-flat-vapextech-rx-145/


This is about half the weight of my subc pack and would be an easy swap if it was in stock!  There's similar on ebay.


Also now done a bit more reading about Lipo batteries and understand why my Viper Marine controller says 'Lipo safe no' and how an alarm can workaround the issue.


Amazing how much there is to learn just building a kit!


Thanks for all the info and until next time 

[malcolmfrary]

HMMM...
When a seller says "MAX Discharge Current >7A", then says "Max Charge Current 2500mAH" I start to wonder just what they mean, and if they actually understand what they are selling.  Although they do say that the quoted charge is at a 5 hour rate.
The discharge figure might or might not be a constant sustainable figure, the charge current figure might indicate that it can be charged at 1C.
A 2S LiPo of probably greater capacity plus its alarm circuit will be lighter and more compact and be capable of the wanted performance.
But yer makes yer choice and yer hands over yer money.

[canabus]

Hi SteveJo
Check out Hobbyking site for Lipo batteries.
Turnigy 2S 1000mah size 73x34x15mm weight 70 grams
Turnigy 2S 1300mah size 73x35x17mm weight 71 grams
Turnigy 2S 1500mah size 73x34x19mm weight 83 grams
Voltage Alarm(part Name Voltage-Alarm)
ESC for brush motors, the Hobbywing 60Amp for 2 and 3S Lipo batteries size 36.5x32x18 weight 39 grams.
I am using the ESC in fishing boat with up tp 60 turn 540 motors.
Link setup, so no program card required.
It's the only one I have found which goes straight from forward into reverse.
Canabus

[SteveJo]

yes now understand that Lipo is the best solution - however I don't have to progress it right now. 


Happy enough with the NiMh pack/boat balance I have to get the deck glued on and start on the planking (fixed the leak around the propshaft)


Easy enough to retrofit a Lipo battery, tamiya adaptor and low voltage alarm in future if the finished boat balance needs it.  If I knew when I started what I know now about Lipo batteries then that's the route I'd have gone but no worries - there's always the next build. 


Thanks again

[Netleyned]

Steer clear of Tamiya connectors. not the best
Especially with Lipos.
Ned