Aerokits Vosper R.A.F. Crash Rescue Tender

[Guest]

I must point out at the very beginning that I am reletivly new to the boat building scene, I have just retired and returned to modelling, my last venture was when I was a teenager a long time agoe. I came across the above kit which someone had already had a go at, it is old but what attracted me to it was that it is of wood construction and being a joiner all my working life it is just up my street.

My problem is that I am sorting out the power for the model, the origional had one motor with an option to fit twin which I have decieded to do. I have 2X550 motors at 15 amps each 6 volts, I want to use a speed controller that I already have which is 6-12 volt 50amp. My question is which batteries to use? weight has to be considered and size but also to look realistic it would have to have some speed with it, also the wiring of the batteries through the speed controller to the motors. Your advice would be very much appreciated, maybe one of you out there has had experience of the same model! Thanks Bryan

[Guest]

Hi Brian and a very warm welcome to the Scale Models forum.

We are a pretty relaxed friendly bunch with a very diverse range of modelling interests and I am sure there will always be someone to offer some advice and guidance.

As for your power plant not knowing the size of the model I am not so sure what sort of suggestions to offer. Your motors actually sound quite powerfull so I am assuming that your boat is a good size and you say that you want a good turn of speed.

As with all these things it is a compromise and you have to balance your requirements of speed with endurance and reliability.

It is important to get this sorted out as early as possible though as the biggest impact on stability will be the battery so you need to get this established before thinking about the rest of the ballast requirements.

My first suggestion would be a small 12v motorcycle battery and connect the motors in series to split the voltage. I use one of those to power the Badger customs cutter that you can see in the gallery. That is a large boat but slow and the battery has so far lasted for nearly two hours on some outings.

The great advantage of this type of battery is that they have a big capacity but they are heavy so location in the boat will have to be carefully considered.

Another possibility is the Tamiya pack type battery that typically come in 7.2 volt configurations. Your 6v motors should be able to comfortably cope with this voltage. You could fit one of these for each motor and even have independant control if you wanted to fit two speed controllers.

I have done this with my Cossack model and used two Tamiya packs with two speed controllers and wired each one up completely independantly. These batteries tend to be less weight but not of the same capacity as the motorcycle battery but the other advantage is that the 7.2 volts will make the motors spin a little bit faster.

At the end of the day I would play around in the test tank (bath) until you have sorted out your ballast requirements then see what sort of weight you have available for your battery and take it from there.

[Guest]

Thank you for your suggestions this is just the sort of input I was looking for. You have given me ideas particularly with the motor cycle battery. Thanks again Bryan

[Guest]

I'm glad I could be of some help. I am sure there will be other suggestions as well and if you have any more questions don't hesitate to ask.

[Guest]

46" Fire tender...

Hello Bryan - I too am now retired but I built this model some 30+ years ago but it was never quite finished because the deck fittings kit became unavailable following a fire at the Kiel Kraft factory (I think Aerokits had been subsumed by Kiel Kraft). I appreciate that yours is an old posting but I would like to chat with you about your experience with this model. Mine is powered by a 6cc? Enya water cooled, throttle controlled engine, with the exhaust well filtered and silenced but it rides in the water beautifully and comes on to the plane magnificently. It is languishing in the loft and I am by no means certain that the engine will run after 30 years of neglect but your posting has inspired me to get it down and take some pictures of it, albeit on dry land for the time being! The hull might have stood the test of time. It was assembled with Aerolite 306 which you must have come across in your day job as a joiner.

Alan

[Guest]

There are a couple of groups where info may be found

The Model Fireboat Website! - Home Page!

firefloat : Firefloat RAF Crash Tender

boath have info that may help you and may get you thinking a bit more about getting it out there is also a fireboat fun day in september, there is info on the first link . there are a lot of people building/restoring these boats and there are plenty of fittings avalable, there is also quite a lot of information avalable that was proberley not around when you built yours

Peter

[Guest]

Just put some pictures of my two fireboat builds in my gallery, one is 34" and one is 24" boath are twin screw on fiberglass hulls.if anyone wants any more info just ask.

Peter

[Guest]

Hi Brian, before deciding on power plants need to consider the boat size if the smaller, I think it was 36" 2x550 will be fine, but the 49" is heavy particulaly if using a jelly cell battery, you also need to look at the prop size suggest you give Simon at The Prop shop a call and he will sort for you you will find info on his webb site also.

At 15amps each your motors will get hot so you need the look at cooling coils also you will need a heat shunt or cooling under the speed controller to be safe, for boats around 4.0" I use 2x12v low rpm motors (app. 5000 rpm) and 65mm 3 blade brass racing props.

As the boat has been standing for some years suggest you run some resin sound all the seams in case the origional adhesive is breaking down, regards, Vic.

[Guest]

Hi Bryan

I have also just retired and have taken up model boats again after a break of 20 years.

My approach is a little different. Start off by putting the model in the bath and loading it up with anything you have (for example baked bean cans !!) until it floats on the waterline. Weigh the added ballast and then put together a 'scenario' of what equipment you can fit to the bare model. You can get weights of equipment from model catalogues (eg servos, ESC's, receiver, motors, Nicads......)

The reason I recommend doing this is because I have a 25 year old unfinished Whaleback ASRL in my cellar which floats on the waterline without any radio gear, motor, batteries or anything !