Dean

An 850 on 12v with a 3-blade 55mm prop will draw A LOT MORE than 12A. I've seen many 20A ESCs burned out running one of these. All I can advise in that respect is not to be tempted by any of the fantastical Chinese E-bay offerings. The current-handling capability of most of them is not just suspect but definitely wrong – in many cases by a factor of ten. Avoid these at all costs. Frankly I'd go for brushless but, as Ashley says, you're already down the road with the 850's.

I don't have any experience of MTroniks 40A ESC but I can recommend from personal use both the ACTion P98 and the Microgyros FR40.

The only other two pieces of advice I'd offer would be not to use sealed lead-acid batteries (much too heavy) and to fit one battery pack and one ESC for each motor i.e. the boat has two of everything. It's expensive but much easier to trace faults, easier on the electronics and batteries and you'll get twice the running time than by just using one pack.

BTW 'Fordspeed 707' was a Huntsman 31 so it's most likely the hull you have is 1/8 scale i.e. 46" long.

'Tintarf a biggun, mester!

Dave M

Dean

From bitter experience I can testify that a pair of 850s in a 5ft Huntsman drew 30Amps during a high speed run and melted the Chinese 80Amp speed controller (and most of the wiring) I was also using a pair of SLA batteries for power and ballast which were simply not up to the job and were seriously hot when I finally recovered the boat.

At the time I had been given some very sage advice involving twin battery packs and twin P98 ESCs which I foolishly ignored.

Hard lesson to learn.

Paul

Hi Dean and all,

Like Dave Milbourn I have a long and happy list of Fairey Marine craft under my belt including quite a few of Dave's own designs as well as Philip Connelly's and also my own designs.

As Dave clearly states in his two part build of the Huntsman, January and February Model Boats Mag 2016. These boats were initially offshoots of racing boats and are strong and light. Small versions of them sail exceptionally well with small brushless motors, they are fast, responsive and beautiful. But they MUST be kept light.

As the models get bigger the problems of powering them at their correct speed and attitude grows exponentially and a large version (Which I originally built around an HP 61 marine 2 stroke engine when they first came out) like the one you are doing, needs to be kept light with the best and most powerful motors you can afford. You cannot afford to use 12 volt Gel Cells, they do not give up their power quickly enough and weigh just too much.

These days we are blessed with the advent of newer technology and even though you have 2 new MFA motors ready to go, I would put them into something else at a later date, bite the bullet as they say and invest in two Brushless motors of at least 35mm to 50mm diameter, they are lighter,cooler and much, much more powerful than a brushed motor as well as 90% efficient. Li-Po batteries are also lighter and can really deliver the power when you need it, I would consider 2x 11.1volt. 5000mAh. and two speed controllers to match, Hawk 60s are expensive but very good.

Having seen a few of these models mooching around the lake and the disappointment on the face of the builder a few times, I wouldn't even consider for one moment using a brushed/Gel Cell/standard Escs. set up for a model like this. ((I've also seen the transformation when it is refitted with a brushless set up!)

Purely my own thoughts on the subject. (Sorry Ashley!)

Ron Rees.