Servo Voltage

[pgfaini]

Restoring my old Dumas, and I noticed that Ron recommends LiPo batteries in his Sailwinch manual. These cells have a nominal voltage of 3.7V. There was no voltage range info included with my Futaba S9405 and S9350 Jib trim and rudder servos, other than their torque ratings at 6.0V. Can they take the 7.4V of the LiPo Battery packs?
I know the LiPo's need a special charger, and can't be over-discharged, kind of a negative aspect.

I've just finished putting together 5 cell packs of 2500mAh AA NiMh cells, which will fit nicely in the keel behind the ballast block, but am now wondering whether to go with the LiPo's instead. As a newby, I welcome any opinions on this matter

Thanks,
Paul

[MichaelJ2K]

You might need to use a voltage regulator for your receiver and servos. 6 volts is about max.

I'm using NiMh cells in my boat. IMO, much easier to use vs. LiPo cells.

Mike Denest
EC12 #899

[Rick West]

Paul,
5-cell 6v boat packs and 8-cell TX packs in NiMh is the standard now for sailing. They are far better than NiCad. It is my understanding the LiPo packs were developed for the growing electric motor market for airplanes.

This is not to say it is not recommended. We really do not know yet. Also to consider being like the whole for some compatibility if sharing is needed at a regatta.

...94

[pgfaini]

Thanks boys, I've decided to go with the 5 cell NiMh packs. The U-tube show of a LiPo pack exploding in flames from overcharging, and the 6V max on the Futaba servos, make me wonder why Rob is recommending them.

Rick, you're right about electric motor driven airplanes, these cells have a current discharge rating that is a multiplier of the cell capacity. A 2500mAh LiPo cell with a C-10 rating, can dump current at 25A (2.5A x 10). My hobby shop owner has a large plane, and the motor was smoking hot when he landed it.

My cell holders have a 2.1mm power plug on a 6" AWG 26 wire. I'm going to replace the wires with 22ga., and install a jack on the systems board. I believe the 2.1mm connectors are rated at 3A. I'm mounting the switch on the deck, and I've mounted the single digit voltmeter on the jib trim servo, so it can be read through the hatch cover without removing .

I've got to admit, I find the Sailwinch setup procedure a bit intimidating, I'm waiting for my Spektrum DX6i Transmitter to arrive, I've already got their 3 channel marine RX waiting to be installed.

This is really a great sport, keeps the grey matter alive, and I haven't even gotten to thr rigging!

Paul

[s vernon]

Paul,

How well is that going to work out for you having the choice of using channels/sticks 1, 2, and 3 on the radio or rewiring the radio pots and channels?

Written by someone who has been thru this exercise - 6 ch radio and 3 ch rcvr - and eventually said, "Oh yeah, that is why the jib trim knob does not control the jib trim servo on the boat."


Scott

[pgfaini]

Scott, Thanks for the heads-up. I'll get on the horn with Spektrum, and check this out. I've still got the option of exchanging the marine receiver, for the one that comes with the DX6i.

Paul

[greerdr]

Good that you went NiMh.
I've read that water and LiPo may also lead to flames.No matter how well we try some water seems to find it's way below.
Think carefully about that deck switch-I have finally quit that.It is very nice but they fail.Without exception.Always at the worst time,like when you finally clawed your way to "A" fleet in a 3 fleet P/R regatta.Ask around and I think you will find most of us put the switch below and many do not use one at all.
Read carefully Rob's recommendation to liberally coat everything with vasiline or simular grease,it does help.

R.C.Greer

[Rick West]

Worse...
In a most unfortunate circumstance, my 94 climbed up on the deck of National Champion Jarl Wathne at the 2008 NCR at Camp Dearborn and carefully without any damage turned his boat OFF.

...94

[pgfaini]

Boy Rick, I'll have to watch out for you! I've heard you can really maneuver your boat, but this is way over the top(No pun intended)Maybe I'll put protective ears on the switch, like I've got on some tools.

On a serious note, have you heard of anyone having problems getting one momentary and two stationary channels in a 3 channel RX? Isn't the Spektrum DX6i programmable as to which Joysticks/levers operate the different RX channels?
Paul

[jack wubbe]

The Spektrum 3 channel recieved is NOT compatable with a DX5e, DX6, DX6i or a DX7. See web site http://spektrumrc.com/Products/Default. ... =SPMMR3000

Jack

[pgfaini]

Jack, Go back and closely read the web site. The RX is compatable with all DSM2 radios, of which the DX6i is one.
Paul

[pgfaini]

Jack, Thanks for posting. There was information on the site not mentioned in the brief documentation the came with the MR3000. The three channels include a throttle and rudder channel, both with dual outputs(Our sails and rudder), and third auxiliary channel suitable for various functions, including fuel mixture control. This means it will have to be able to be set up as a stationary proportional control, as needed for the jib trim servo. Tomorrow, I'll call Spektrum Tech., and find out what options I have regarding which TX control will operate it.

[jack wubbe]

Paul;

You are correct, the marine reciever is OK with most Spektrum radios.

Jack

[hedderick]

In case anyone is interested, I have been using a Lipo battery in my EC12 for about a year now. The RMG winch is fed directly from the lipo, whereas the Spektrum receiver and other servos (3) are powered through a 3 amp, 6 volt voltage regulator ($15, weight .3 oz). This is a very simple step up to install and there are several advantages:
1) The RMG winch requires a momentary 20 Amps (yikes) each time it starts to turn. No Nimh battery can put out this type of amperage, so the whole systems sees a momentary voltage drop... 97% of the time, this is no problem, but it can cause the Spektrum reciever to drop out and then you lose control. I've put a volt meter on the system and with a lipo, the voltage is rock steady, not choppy like with a Nimh
2) The RMG is VERY powerful and FAST with a Lipo (8.4 volts is the initial voltage of a two cell lipo)
3) The other servos are run at their max voltage of 6 volts and the voltage is very steady, so the rudder, in particular, is always very powerful, even in heavy air.
4) Once a lipo is charged up at home, it does not bleed off power while sitting idle. So when you go to sail, you always have 100% charge.
5) Lipos do require a special charger and they are more expensive
6) The lipo in my boat is velcroed high on the keel side, so it doesn't get wet. It only weighs 2 oz.....
7) My boat has not gone up in flames yet, nor am I concerned. Lipos can become very hot if rapidly discharged or charged, but in our boats that is never an issue.
If anyone is interested, the installation can be seen at Palm Beach Gardens.......Yellow Boat #38



Richard Hedderick

[Rick West]

That was an excellent report, Dick. It takes off the muddy stains we have heard.

I have asked Rob Guyatt to comment when he has time.

...94