Servo for fishing boat rudder

[Michael BordParticipant @michaelbord10152]

Been building a fishing boat model for a while, as spring approaches it's encouraging me to get it on the water! With previous models I've fitted a standard analogue servo for steering, howevr they have been smaller or lighter models (largest is a Flower class corvette (from Revell kit) which is quite light).

Fishing boat is 34" long by 11" beam, underwater depth going to be about 4" below waterline. Would it be better to use a more powerful servo or will standard one like a Hitec HS311 do the job? I could just fit one and try it out but I might as well start with the most appropriate one and there's a lot of advice on this forum.

Also have a 6v lead acid battery to use, will that be ok to run radio receiver off speed controller bec output? (Other models have used higher voltage packs).

[Michael BordParticipant @michaelbord10152]

[Charles OatesParticipant @charlesoates31738]

I've never had a problem using a standard servo in similar or larger and heavier models so in my opinion you'll be fine.

Regarding the 6 volt on pb battery, that should be fine too…..with a proviso. 6 volts is near the cut off voltage for many becs, about 5.5 volts. A good, regularly charged pb battery will be around 6.7 volts fully charged and will be ok. If it's old or not maintained cross your fingers and don't sail until the battery goes flat.

It happened to me once, I lost control as the battery died, so I later used a separate battery for the receiver and kept on with the old pc battery for the drive motor and it was fine for quite a time after that.

Charles.

Ps it's worth checking the current drawn by the drive motor in the water, then you'll know if you're likely to over stress the battery.

[Chris FellowsParticipant @chrisfellows72943]

Hi – Michael

As Charles says that servo should be fine, as a fishing boat is fairly slow. With faster models a more powerful servo is a good idea as the water pressure on the rudder is greater at higher speeds.

Chris

[Richard SimpsonParticipant @richardsimpson88330]

A standard sized servo is more than capable of steering such a model.

As regards powering your receiver, I have only ever really thought that a BECC arrangement is worth considering if you are limited for space or ballast and you were therefore pushed into using the main propulsion battery to power the receiver as well. If you have available space and reserve of ballast a separate receiver battery does give you a little more flexibility in the "Get you home stakes". With a separate receiver battery set up, as a main propulsion battery dies down you will be able to use every last drop to get you back to the bank but with the main propulsion battery also supplying the receiver, especially at 6v, as soon as the battery starts to approach the end of its capacity the voltage will start to drop and you will soon loose the receiver, rendering anything left in the main battery as unusable. You will also of course be reducing the duration by a small amount as well.

On the other hand if you have a battery that has loads more charge than you are likely to use in a visit to the pond and you will never even get close to discharging it then it won't make any difference.

As an example I have an old Graupner Ton 96 fishing boat. It must be around two foot long and has a 12V 7ah lead acid main propulsion battery, that also does everything else, lights, sound, receiver etc. At last years Endurance Race I couldn't get anything else ready in time so I thought at least I would enter with the fishing boat to make up the numbers and bring it in as soon as I saw anything odd happening. I ran it flat out for an hour and it finished second! Sometimes a lead acid battery can keep you going for a long time and save the worry of having the receiver separately powered.

Edited By Richard Simpson on 02/03/2023 16:35:09

[Nigel NorthwoodParticipant @nigelnorthwood17509]

Tbh: a standard servo from Howes Models will be more than adequate.

I've used several, and their sail winches on the models I've restored, including a 50" hull that started life as a Marblehead and it turns like it's on rails.

[Michael BordParticipant @michaelbord10152]

Thanks to all for your very helpful advice. Servo sorted, I'll fit a "cooking" standard one.

Once boat is ready for the, er, test tank (do have wife's permission to use bath!) I'll connect multimeter in circuit with the motor and battery and see what the max current draw is. I've also got a couple of different diameter props to try. There'd be plenty of room for a seperate receiver battery in the model, if necessary.

I'll report back in due course as to how this all goes. Thanks again.

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