Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[NobbySideways]

Hi there,


I'm about to start building a fibreglass hulled Fairey Huntsman 31 (the Precedent 34" kit) and would like to look at a rig that would give me decent pace. I've never built a boat before and am looking forward to the process. I've spent the last couple of days educating myself on this very useful forum.


As I'm completely new to it all I have no equipment at all, which means I might as well buy the right kit straight from the off, but I figured I should start looking at the motor and prop first off. Everything I have read has suggested I go Brushless, especially as I'm starting with nothing.


I was thinking about using a Thumper V2 3548/05 running on 4S lipo with a 60A speed controller and a 40mm prop. I considered two motors but figure the additional complexity wasn't worth the effort (but please feel free to voice your opinions)


Does anyone have any opinions on this setup? I'm looking for decent pace, and from the tentative calculations I've made the setup above should get her motoring a treat, unless I've made a serious booboo. I want to get her planing well, I guess I'm just a speed freak.


Thanks for any assistance you can render.

[essex2visuvesi]

Here's my build log for the same kit
http://www.modelboatmayhem.co.uk/forum/index.php/topic,36813.0.html


Mine has enough power to stand on its transom if you are too eager with the loud stick 
Currently the model is in Finland & I am in the UK so not much has been done of late

[boatmadman]

You might need a bigger esc with that motor and prop. I would look at 100a and water cooled.Also what is the kv of the motor..that will dictate the prop revs. You should be looking for an unloaded speed of about 12000..15000 rpm for submerged drive.
Find revs by multiplying the motor kv by battery voltage
Ian

[Calimero]

I don't think water cooling would be needed. I'd move to a slightly more powerful car ESC (can be had for less than $50). They come with heat sinks and cooling fans. Car ESC also usually offer smoother throttle response than offshore-type ESCs.

[NobbySideways]

Excellent, many thanks to all those who have commented.

[Leaky Bottom]

Hello
My Huntsman is the Precident wooded hulled version, very heavy and converted from ic power. I use a simalar sized motor but only on a 3 cell Lipo with a X45mm propeller and a 40amp speed controller. It performs very well
 
I would get the largest capacity battery you can for longer run times
 
On another point, try to keep the superstructure as light as possible and add ballast inside the bottom of the hull if it needs it to get it to float on the correct waterline, I've heard it said that the fiberglass hulled versions tend to roll a bit.
 
Post some pics of the build if you can

[NobbySideways]

...what is the kv of the motor..that will dictate the prop revs. You should be looking for an unloaded speed of about 12000..15000 rpm for submerged drive.
Find revs by multiplying the motor kv by battery voltage
Ian

I worked out that using a 4s (4x3.7) I should be getting 14.8v. The unloaded speed of the 900Kv motor I mentioned would be (if I have done the maths correctly, still learning...) 900 x 14.8  which takes me to 13,320. Thats slap in the middle of the magic figure you state. Hopefully that means I've not screwed my maths up?

[NobbySideways]

I've committed now, I've bought the motor... here is hoping I guessed right! I'll buy an ESC soon, 100A as suggested

[NobbySideways]

It may be that this motor is hard to get hold of.... I always pick the wrong items! 

[canabus]

Hi NobbySideways
I am running the same size boat with a brushless;
D3548/4 1100kv motor on 4s(14.8volts)  free run 16280rpm,HK-60A
Car type ESC,
Zippy Compact 5600mah.4s.60c battery with a 40mm x 1.4 pitch prop.

Run time about one hour, speed over scale speed .

Repaginated - Admin 

[NobbySideways]

I am running the same size boat with a D3548/4 1100kv motor on 4s(14.8volts)free run 16280rpm,HK-60A car ESC, Zippy Compact 5600mah.4s.60c battery with a 40mm x 1.4 pitch prop.
Run time about one hour, speed over scale speed .

Canabus, I can't tell you how useful your post is. It gives me a bit more confidence to know I'm heading in roughly the right direction. The info you give (specifically run times, prop size/pitch etc) is really useful to me to work out what I can expect from mine.


Out of interest, is that a 3 blade prop? And what have you done about cooling? I'm toying with the idea of running a seperate water pump to ensure the cooling keeps going during periods of slow movement after high speed runs (when the cooling is probably most important).


Thanks again for your post.

[canabus]

The car ESC's have a fan on top and run all the time, no water plumbing required.
I do not run water cooling on the motors but Hobbyking have a number of these!!!
The D3548/4 motor has a rear mount and a built in fan in the front case, so no cooling required.
My other motors 3639-1100kv and 3648-1450kv are mounted on alloy engine mounts, these only get warm with long hard runs.
As for 3 blade props I have not tested on a boat as yet.
I am ordering a 42mm x 1.4 pitch prop (code HK-5B12x42) it is 5mm shaft so I cut a sleeve from a gold wire connector.
This works very well.
Also ordering a 45 x 1.4 pitch prop( code 377000015 or 377000016).
I first started with the plastic props because that are cheaper and if they do not suit the boat it's not a great cost.