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Brushless Balaenoptera Musculus

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Old 11-05-2012, 03:20 PM
  #1
seehuusen
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Default Brushless Balaenoptera Musculus

Hey fellow modders :-)
I have gone and purchased another toy boat to mod
I really like building these boats; it gives me no end of pleasure.
It’s relaxing to sit at home with a beer, some music and modify these boats, then take them out and see how much better they run. Bring back home, repair something or modify the boat further, just to squeeze a bit more out of it, I love it :-)
Damfurst on this forum started an awesome build with dual brushless motors, using the original drive train. I’m wanting a single motor, I think it’ll be easier to maintain and build (plus that’s what I’d want anyway)
The plan is to run a 3/16inch flex shaft setup to a strudder (stinger with a rudder behind it)
I’ve heard people say lots of confusing things about the flex setup, and because this is my first ever prop boat, I’m probably not understanding the advice.
The general thing I understood were the parts involved, but sizes seems a bit odd.. With some shops only selling certain bits?!? Anyways, I found this listing, and that’s what I believe I’ll be going with
The kit contains everything I need, so I can learn all the bits and how they work together
Motor wise for this thing, I’m thinking something in between 2860 and 3660… It just depends what sort of Kv rated motors I can get… 2500Kv on 3S and 3300Kv on 2S seems to be the goal
I’ve gutted the boat, and sanded it down. I’m going to put some putty in all the little cast holes
I really want a 100% smooth bottom surface, as I’d like to hit 50+ km/h with this thing
Cheers
Martin
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Old 11-05-2012, 07:50 PM
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Default RE: Brushless Balaenoptera Musculus

Yeeooow "The Blue Whale" only to be used in water!..

Looks the goods mate, i'm watching what your doing as i don't have a clue on prop boats....lol

50+k's should be sweet. looks as tho you've been busy, man i hate sanding!
Inside hull pics would be good once you get the chance also.
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Old 11-07-2012, 07:43 AM
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Old 11-07-2012, 03:14 PM
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Default RE: Brushless Balaenoptera Musculus

Mikeup you are a f..in legend!!!  That information is GOLD! In fact, I've copied it in case it went away due to a crash!!

I am totally keen for offset rudder now that you mention maintenance (as I am not hesitant to run my gear in salt water)
When looking for rudders, I must ask, what do I need to look for? Does it have to be further back than the prop?

e.g. if I went with a stinger, say 70mm or so long, would the rudder HAVE to be behind the prop on the stinger? (checking to find out how long it needs to extend back)

Thanks again for parting with your knowledge, I really appreciate it

Cheers
Martin
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Old 11-07-2012, 07:12 PM
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Old 11-07-2012, 09:06 PM
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Default RE: Brushless Balaenoptera Musculus

Mike, you are a wealth of information!!! Thanks so much for parting with it
I will do some research and post up some new rudder/drive train combos

Thanks
Martin
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Old 11-08-2012, 01:04 PM
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Default RE: Brushless Balaenoptera Musculus

Hi Mike,

I went to Hobbyking to see what stuff they might have, and I'd like your oppinion please





The transom on the boat is bowed, so I'd need to make a small mounting pod for the stinger, which should push it out the few extra mm if required

What do you guys think?

Cheers
Martin
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Old 11-08-2012, 01:15 PM
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Default RE: Brushless Balaenoptera Musculus

I also found a potential motor


and a bit more information


Cheers
Martin
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Old 11-10-2012, 04:51 PM
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Old 11-11-2012, 12:00 PM
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Default RE: Brushless Balaenoptera Musculus

LOL Mike, your message cracked me up Thanks for your research and time

If I followed Mike right, using the Hobbyking stringer and rudder I suggested above, should do the trick
By adding a small pod for the stinger, I can' move the exit of it, back 9mm or so, in line with the leading edge on the rudder.

I'll get those parts and the motor shipped over this week, then I'll figure out this flex shaft assembly, which is still somewhat fuzzy for me... 
(When I get the stringer drive it'll be clearer, as that's the part I don't get, if they are made for a specific sized tube, or you space that out with sleeving the inside...)

Someone please clear it up for me is it stRinger or stinger? I've seen both...

Cheers
Martin
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Old 11-11-2012, 02:09 PM
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Old 11-15-2012, 12:49 PM
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Default RE: Brushless Balaenoptera Musculus

I'm looking at buying hardware today

What is a 6 pitch prop?
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Old 11-15-2012, 02:54 PM
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Default RE: Brushless Balaenoptera Musculus

OK, the list is nearly complete... Boat is intended for 3S

Motor: 
XK3665-B-2500KV Brushless Inrunner
36 Size Adjustable Motor Mount with Water Cooling
Water Cooling Jacket for 36mm Brushless Motor

ESC:
Not sure, will update

Running Gear:
all 4mm gear
Flex cable with end (approx 300mm long)
Outer tube (Use with teflon liner, 300mm long, 6mm x 0.2mm thick)
Drive dog
Threaded prop nut
Teflon thrust washer (to use between drive dog and strut end)
Teflon liner (Suits 4mm cables, 300mm long, 4.5mm id x 5.5mm od)

This is paired up to a 70mm long 4mm adjustable Stinger

Rudder:
130mm X 32mm wide Rudder dual pickup version (130mm deep X 75mm offset rudder with dual pickups, Uses kick back funtion for safety, mounting bolts included)

Servo arm, piano wire or what ever
Servo arm boot
Metal Gear Digital Servo - MG995 - 15kg thrust

Props:
???? 33mm - 36mm at what pitch? 1.4? I want to buy a small selection of props, preferably plastic, that I can then test out, and buy the better cnc prop after that...

What do you guys reckon?

Cheers
Martin
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Old 11-15-2012, 03:32 PM
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Old 11-15-2012, 04:30 PM
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Default RE: Brushless Balaenoptera Musculus

Hi Mike,
I found those on OSE, and then I thought to myself, I really aught to do myself a favour and figure out what 6 pitch is... I got it (http://www.modelpowerboat.com/conten...136-propellers)
Using your graupner as an exampleiameter 36mm, Pitch 57mm. This is nearly the same as: 36 x 1.6 x 4mm prop
Now to find some over this side of the pond, coz at $21 shipping, they are a bit too expensive...
Could I go a larger sized diameter with a 1.4 pitch, or does that put too much strain on the motor?
Or should I go the smaller diameter, but with a bigger pitch?
Cheers
Martin
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Old 11-15-2012, 04:33 PM
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Default RE: Brushless Balaenoptera Musculus

also, I know from my ski boat, more blades gives a better hole-shot, e.g. faster acceleration and better turning... I doubt it's desired in an R/C boat, but what are the pros/cons?
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Old 11-15-2012, 04:38 PM
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Default RE: Brushless Balaenoptera Musculus

here's one... maybe? gotta drill out to 4mm hole size, but that'd be OK

35mm 2 Blade EP CNC Boat Prop (P1.7 D1/8x2)

Light weight and precision CNC machined.

Shaft: 3.25mm
Weight: 1.6gram

$18.08
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Old 11-15-2012, 05:59 PM
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Old 11-15-2012, 06:02 PM
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Default RE: Brushless Balaenoptera Musculus

maybe I'll get it later, just placed an order for the lot!!!!
Thanks again for your explanations... I ended up gettting a 37mm 1.4 pitch prop... Had to have something LOL (I'll research for other shops here in Oz)
~$300 all up, with postage... It's a little more than I wanted to spend, but I wanted it... So what can you do?
MOTOR:
XK3665-B-2500KV Brushless Inrunner - $39.13 (HK)
Shaft Adapter - 5mm motor shaft to 4mm Flexi Shaft - $4.96
36 Size Adjustable Motor Mount with Water Cooling - $14.99 (ebay)
Water Cooling Jacket for 36mm Brushless Motor - $16.69 (ebay)
ESC:
Turnigy Aquastar 120A Watercooled ESC $69.56 (HK)
Water Outlet Barb - $2.99 (ebay)
Servo:
Metal Gear Digital MG995 - 15kg - $7.83 (ebay)
Flex-Rod Boots - $1.14 (HK)
Servo Con-Rod for Boat Rudder $2.47 (HK)
Running gear:
All from RC Boat Bitz, South Australia
4mm drive dog $3.00
4mm outer tube $4.00
4mm threaded prop nut $3.00
4mm flex cable with end $15.00
4mm teflon liner $4.00
130mm Rudder dual pickup version $38.50
Stinger 70mm long 4mm adjustable $25.00
4mm teflon thrust washer $1.00
37 x 1.4 x 4mm prop $15.00
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Old 11-15-2012, 06:42 PM
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Default RE: Brushless Balaenoptera Musculus

Good to see the project moving ahead Martin. I've realised that i need a lot of schooling on prop boats thats for sure.
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Old 11-15-2012, 08:21 PM
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Default RE: Brushless Balaenoptera Musculus

LOL, Mike's your man!!
In all fairness, once you figure out how to read the different prop numbers, it's a bit simpler...
The site I quoted above, has that part down pat!
Understanding diameter of the prop and pitch (which is the distance the prop travels forward on 1 revolution, theoretically) and shape is pretty much all there was to it...
To get the top speed, I believe Mike did the following calculation
33mm diameter at 1.6 pitch (calculated pitch x diameter = distance travelled by one revolution) would yield
re">
re"> 33 x 1.6 = 52.8mm/ revolution
re"> 2500KV motor @ 11.1 volt = 27750rpm at full throttle
re"> 27750rpm x 52.8mm = 1465200 mm/minute
Converting this to a bit easier figure = 87.912 km/h THEORETICALLY
However, in reality, the prop slips in the water, and so you loose anywhere between 15% - 30%, so 67.6 km/h is possible...
The shape of the prop, determines it's efficiency to a large degree
Other factors play in at these speeds as well, coz now you have tremendous drag from the hull to think of, plus that massive fin, total weight, water conditions etc
I'd really like to figure out what the heck the different diameter has an effect, I think it pushes more water, so you'd think higher speed. I think it comes at the cost of engine heat... anyone care to clarify?
Cheers
Martin

PS. I'll bring my boat down to Brissy when I've built it, can show it all to you then I'm sure I've got a fair bit to learn yet
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Old 11-15-2012, 08:28 PM
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Default RE: Brushless Balaenoptera Musculus

oooooooooohhhhh * SLAPS OWN FOREHEAD*
ofcourse!!
if you have a larger diameter prop, it will travel further per RPM at the same pitch compared to a smaller diameter prop
e.g.
33mm x 1.6p vs 37mm x 1.6p = 52.8mm vs 59.2mm per revolution

The prop I purchased, 37mm x 1.4p = 51.8mm/revolution, which equates to a theoretical top speed of86.247 km/h, so still capable of ~50+ km/h
Hoping the motor doesn't get too hot
Thanks brain... it's Friday, I need a drink hahaha
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Old 11-16-2012, 05:34 AM
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Default RE: Brushless Balaenoptera Musculus

In RC planes the pitch determines top speed the diameter determines thrust.

There is no point having a very high pitch (good top speed) if there is not enough thrust (diameter) to get you there.

Pitch=speed
Diameter= thrust/acceleration.
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Old 11-16-2012, 06:47 AM
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Old 11-16-2012, 01:27 PM
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Default RE: Brushless Balaenoptera Musculus

cheers Mike I've got a hight quality 120amp ESC, which I've tried and tested before, it should muster whatever that 36mm motor can demand
As for prop size, thanks for the clarification, I thought there would be more work for the motor with a larger prop... I'll get some more when they become available, I like experimenting anyway

cheers
Martin
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