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[corinmellor]

Could any body give me some advise on the best set up for my MFA spearfish I am restoring.I would like the boat to run pretty fast.
I was thinking of using the following but I am no expert and would appreciate some advise. The boat is 36 inches long and 12inch beam it is single shaft with a v hull.Would this work
motor-turnigy aquastar 4884 1050kv ?  or aquastar t20 3t 730kv/1280kv ?
battery 1x zippy 5800/ah 5s ip 30c ??
esc turnigy aquastar 160amp
prop ????


any help please

[ChrisF]

Is that first motor a brushless? If so I think that would be on the big size and a 5S battery way over!

If Canabus doesn't see this drop him a PM as he has experience of these and similar boats.

Have a look at recent threads in Model Boating and Beginners in the General Section as there has been discussion on motors etc. for similar sized and types of boat.

Chris

[corinmellor]

Thanks Chris,
the first motor is brushless from hobbyking my mistake it is 4084 1050kv and I am sure you are right
it may well be overkill. I will look at somemore threads and see if Canabus can advise me.


Corin

[corinmellor]

update.!!
I have searched the web and threads and come up with this possible set up ?
3648 1450kv 1600watt turnigy
4s 5800 mah (not sure what c ? )
40mmx1.4 pitch 2 blade prop
100amp hk100a car esc


If any one has any got any views if this will work on the old boat

[ChrisF]

Yes, that's more like it, though the kv is probably a little on the high side for the type of boat. Around 900 to 1000 will give you more torque.


I'm about to start building a 33" Fairey Swordsman and am going for a bigger 42mm dia. 800kv motor with a 40mm prop and 4S LiPo so that it won't be working too hard and give me a good run time.. It will be heavier than your boat though.


Be interesting to see how you get on as I recently picked up an MFA Spearfish kit and need to get the motor for that.


Chris

[ChrisF]

Just been looking at the Overlander site, as that is what I've bought for the Swordsman and will probably stick with them, and they do a 3548 900kv that will do me.

If you do want higher revs they do higher kv ones. Canabus does tend to use higher kv as he is a bit of a speed freak and has access to a good stretch of water to use it.

[canabus]

Hi corinmellor
My mate is running a MFA Spearfish which he started with a 100 Amp car ESC, 3S Lipo 5800mah 60C and a 3639-1100kv 800watt brushless motor.
Prop was a 50mm 2 prop 1.4 pitch.
The was quick, but, we changed up to a 4S Lipo 5800mah 40C.
The boat was quicker, but as it is a very stable boat.
We straight changed over to the 3648-1450kv 1600watt on the 3S with a 2 blade 45mm 1.4 pitch prop.
Getting into the fast end the boat was still stable and quicker.
So we changed last Saturday to the 4S Lipo and changed the prop to a 2 blade 40mm 1.4 pitch prop.
It's dam quick and still very stable.
GPS at 37KPH, if that's quick!!!!
The only change to the ESC was the cut out voltage for the different batteries and the start power from 10% down to 5% for better low speed.
The onboard Amp meter showed 72.88 Amps at full speed on a fully charged 4S battery.
I have a XK3674-1660kv 1600 watt sitting in my lengthened Swordsman which I have not finished so we may drop it in the Spearfish for fun.

Canabus

[corinmellor]

Thanks Chris,
I will check out the overlander site. What c rating should I go for with the battery pack, I understand what the c rating means but not sure how this translates to the set up, is 40c enough or do I need to go higher ? Also I was going to replace the prop shaft as it must be 40 years old do you have any recommendation for this, I have also read that 12 degrees is the correct angle from the hull.
sorry to ask you all these questions but I am more used to full sized boats and dont want to get it too wrong !
Corin

[corinmellor]

Thanks Canabus,
thats realy helpful its good to know what works on the exact boat, so if I went for your tried and tested set up as follows


100amp car esc
4s 5800mah battery   40c or 60c ?
3648 1450kva 1600watt motor (should this be water cooled ? )
2 blade 40mm1.4 pitch prop
I saw a full sized Spearfish on holiday in Greece this year and had a chat to the eccentric owner who gave me tour around,sadly no ride was offered !
Corin

[canabus]

Hi corin
https://www.youtube.com/watch?v=jMsPNyepbTs
You tube video from Saturday with the Spearfish at the end and my Sea Hornet at the start making two 180 degree turns.
Canabus

[canabus]

Hi again
The motor is not water cooled.

Canabus

[corinmellor]

Canabus,
thanks for the video, that will spur me on ! and what an amazing place to run a boat !
Am I better with 40c or 60c for the battery you had run both,and do you know the best angle to set the prop shaft ?


Corin

[canabus]

Hi corin
He did not change the prop angle from the original.
A 60C is a bit heavier and we have not tested one in the boat.
Yes a top location.

Canabus

[ChrisF]

Corbin - I've read up quite a bit on prop shaft angle and 12 degrees is fine, that's what I'll be using.

Chris
 

[corinmellor]

 Thanks Chris ,
thats reassuring, good luck with the build and thanks for your help.


Corin

[canabus]

Hi corin
I am looking after my mate's Spearfish whilst he is hospital.
The original boat had a shaft angle of 17 degrees with the center of the prop 105mm from the stern.
The 40mm prop has 8mm clearance.
The rudder size is top 29mm, bottom 27mm and depth 52mm, with a 4.5KG servo.
He has been having problems with the boat, so I am changing around motor, ESC and battery.
All the same gear except it's my stuff.
Tracing it down to one of these.
Once it is fixed I will have time to test the XK3674-1660kv in the beast!!!
Post a few pics of the boat for you.

Canabus

[canabus]

Ho corin
Pics of the boat.
Canabus

[corinmellor]

Hi Canabus,
thanks for all the pics and help . I am just about to install a new propshaft and rudder so thats great.
Let me know how you get on with the large 3674 motor. How do you think the 3648 would run on 5c ?


Kind regards


Corin

[canabus]

Hi Corin
The 3648-1450kv will handle up to 6S !!!
I am using the Hobbyking HK100Amp which only handles up to 4S.
The boat goes like a rocket on 4S and probably fastest than when they used the 10cc IC motors in them.
We GPS the boat at 37KPH on the 2blade 40mm prop and the onboard Amp meter hit 72.88 Amps.

Canabus