Brand new to boats, have a few questions about getting started right

[Davey80]

Hey what's up, i'm finally taking the plunge into boats. I have a fair amount of RC experience with Monster Trucks and Comp Crawlers, but this whole boat scene is completely new to me. I have a few starter questions,... any advice, knowledge, or other feedback would be much appreciated.

Here's what i'm looking at:

1-Traxxas Spartan
2-Atomik C1
3-Venom Segad C1
4-Venom KOS C1
5-Pro Boat Blackjack 29
6-Pro Boat Impulse 31
7-Pro Boat Miss Geico
8-Vantex/Fuyuan Bud Select 34 (Hull)
9-Vantex/Fuyuan Thunder (Hull)
10-Vantex/Fuyuan Victory (Hull)

At this point, i'm pretty sure i want to grab the Venom Segad, and a Spartan. I also want to order a Bud Select Hull and then build it up myself with top quality components. This is where my questions start. The Bud Cat is available in three versions from Fuyuan. RTR, ARTR, and Hull only. I've got a love affair going with the hull, but don't care about any of the components that come with the RTR/ARTR versions.

Question One: Are aftermarket components for mid sized 34-35 inch Cats fairly universal?, or do you have to stick with the the basics from the manufacturer? The hardware parts are what's worrying me. Things like the rudder, flex shaft/drive shaft, shaft sleeve, and other parts that would go along with these are what I would need to get this going.

From everything i've been reading lately, the Leopard motors are a pretty decent way to go. I was thinking i would go with a mid sized brushless water-cooled 4 pole. So I was checking 'em out on their site and they list five different options:

1 - LBP4042 B
2 - LBP4065 B
3 - LBP4074 B
4 - LBP4082 B
5 - LBP4092 B

I'll be using it with a Castle Creations Hydra Ice 200 ESC.

My goal is a build that has a good mix of weight, speed and power. I don't need the fastest boat out there. I don't want a boat that almost sinks below the surface because it has a massively heavy power plant strapped into it. I DO need it to look cool, run cool temps, sounds awesome, be good quality, and have a decently fast top end...in the 55 to 60 mph range.

Question Two:

Each one of these motors is available in a whole bunch of different models...i.e. the LBP 4074B2Y which has specs of 135A, 23V, 2600W, 2150KV. Another model of the same motor is the LBP 4074B3Y which has specs of 95A 35V 2600W 1400KV....and so forth and so on...When I first went to the page, I thought all I had to do was narrow my choice down from five...now it's more like thirty-five! Where do I start?

If 2Y or 2.5Y or 3Y refer to number on winds, how can I take this knowledge and each set of specs for these motors and use it to make an educated decision on what I should buy? Is there a way to explain this stuff in layman's terms? How does the 4074 series of motors compare to the other four motors listed?

Thanks!

[TheShaughnessy]

My first thought is stay away for the spartan. Before selecting a motor you need to decide how many cells you are going to run. On 4s the 4074B 2y 2150kv motor is better suited. However if you want to use 6 s the 4074B 3y 1400kv would be better suited. Hardware is easy enough to find and is somewhat universal for similar sized boats.

Have a look at the thread at the top of this page. FE for beginners or something like that .

[mekzoid]

The answer to your kv question, The higher the kv the lower v packs you run. The math is kv x v = rpm Rpm should be under 35000.
TheShaughnessy said the 2150kv would be a good motor, the reason behind that is 2150 x 14.8 = 31820 rpm
A previous thread that I asked a question in would make more sense of your question aswell:
http://forums.offshoreelectrics.com/...count-same-rpm

[BHChieftain]

I would highly recommend either the Proboat or Aquacraft 30in models-- these are proven designs

Monos:
Proboat Impluse
Aquacraft Revolt


Cats:
Proboat Miss Geico
Proboat Blackjack
(these are very similar)

Aquacraft Motley Crew
Aquacraft Lucas Oil
(these are very similar)

First, you should decide between a mono hull or a cat hull. Monos are easier to setup and can run in most water and wind conditions. Cats are faster, but tricker to setup, and need smoother water and they don't like wind.

Between the Proboat and Aquacrafts-- they are both great systems with very good quality drive systems. I tell people to first choose hull type, then choose which paint scheme they like best.

I have setup/running guides for most of these boats, if you would like a copy of any of them shoot me an email at [email protected]

Chief

[iop65]

The answer to your kv question, The higher the kv the lower v packs you run. The math is kv x v = rpm Rpm should be under 35000.
TheShaughnessy said the 2150kv would be a good motor, the reason behind that is 2150 x 14.8 = 31820 rpm
A previous thread that I asked a question in would make more sense of your question aswell:
http://forums.offshoreelectrics.com/...count-same-rpm

ideal rpm depends on the hull type ,i would say :first choose hull ,then powerplant

[Davey80]

Cool, thanks for the info!

I'll break this down a little further to see if I can get a better understanding of the differences between these Leopard motors, and how to decide which one is best for my Bud Cat build.

1 - LBP4042 B
2 - LBP4065 B
3 - LBP4074 B
4 - LBP4082 B
5 - LBP4092 B

First - The Hull. This will be a 34 inch single outdrive cat.

Second - LiPO cell count. I want a top speed of 55-65 mph so i'm guessing I would need 6S .

Third - Motor max voltage. For 6S, I will need a motor rated to at least 25.2 volts.

Fourth - The ESC. I will be using a Castle Creations Hydra Ice HV 200 which will handle up to 200 continuous amps.

...Ok, so...

The 6S voltage rules out the Leopard 4042 series.

The 4082 and 4092 motors weigh almost 500 grams each...a little heavy I think for this 34 inch Bud Cat, so i'm ruling them out.

So now I have these two series of motors left:

2 - LBP4065 B
3 - LBP4074 B

This leaves two options from the 4065 series that would work with full 6S voltage. These weigh somewhere around 315 grams each. Here they are:

LBP4065-B/3Y 82A 27V 2000W 1800KV
LBP4065-B/4Y 69A 35V 2000W 1400KV

Then there are three options that fit the voltage requirements from the 4074 series. These motors weigh around 370 grams each. They are:

LBP4074-B/2.5Y 135A 25V 2600W 2000KV
LBP4074-B/3Y 95A 35V 2600W 1400KV
LBP4074-B/4Y 79A 45V 2600W 1050KV

So far i'm feeling good about narrowing it down to five, but...here i'm confused on both the Amps and Watts part of it though. They are basically the "power" level of the motor right? How do i know how many i need my motor to be rated for?

Now....if i was to just make my decision right now based mostly off of kV, I would pick a motor that lies in the middle of the spectrum that should in theory have a good mix of torque and top end speed.

I would cross off the 2000kV, and the 1050kV, leaving me with the 1800kV and the two 1400kV's. I would further eliminate the 1400kV that has the lower amps and watts, leaving me with two final choices...the 1800kV model 4065-3Y, and the 1400kV model 4074-3Y.

If I had to choose between these two right now, I would take the the 1400kV 4074-3Y model. (Coincidentally, this is the exact motor TheShaughnessey recommended above!) It's kV is a little more mid range, and it has significantly more amps and watts.

Any thoughts on this? ...Am i on the right track here?

Thank a lot!

Mark D.

[HTVboats]

Narrowing down to a 34" hull helps us. Normally that would be a 4-6S setup but 6-8 is possible just different batteries.
POWER = Watts or in this case milliwatts. your 40X82 motor is rated at 3500mw. Disreguard kv for now and divide 3500 by the voltage and you get amps. All theoretical and max rating. So 3500 divided by 22.2v (6S) pulls 157 amps. 3500 by 29.6v (8S) pulls only 118. Both do the same amount of work using voltage vs. amps to make power. As you go up in cells you draw less amps.

KV's - rated rpm for a motor. 1250kv X 29.6 (8S) yields a no load rpm at 37000. On 22.2v (6S) you would pull 27750 rpm. Same watt motor you could theoretically just use a higher pitch prop to accomplish the same speed.
Stay with me here and lets say we are using the same can size and watt rating and using 22.2v (6S) we go up to a 1600kv motor. 1600X22.2=35520 rpm. Very close to the 1250kv on 8s. (37000). These using the same prop and total weight boat would perform similar. Less amps again with the higher voltage but HP (watts) the same potentially.

This is where in the real world it gets down to efficiency. What prop pitch and diameter work giving enough traction (slippage) to propel your load. Weight and hull style all play into it. How many ma of battery weight are you going to carry vs run time and speed.

A good target starting point for sport running is 25000-30000 rpm. Heat racing probably 30000-36000 rpm and SAW guys go into the 40000 plus range. Bear in mind your 36000 no load is going to come down to around 30000 rpm in the water under load. 15-20% down from whatever no load.

A 40X82 1250kv motor would work well on 6 or 8S in your cat. If you didn't go above 6S I would use a 1400-1600kv motor. Start with the 1250 on 6S and get things setup then you can always bump up kv's or cells to go faster. Prop light with a X442 to an M445 to start and go from there. On an outboard tunnel with a 1600kv-3500mw motor on 6S we make 45-55mph. Going down to a 1250kv we could prop up a bit, but be careful of larger props as pitch and diameter both go up. Pitch is more load of course but diameter really eats torque load exponentially. That's where setup and trim gets critical and you get real close to the cliff where you just go up in smoke. Watch heat and stay conservative as your motor will try and pull any prop you have. It doesn't sense failure so you need to.
Hope some of this helps.
Mic

[siberianhusky]

I have an example involving one of my boats, it's about the same size but a mono, currently I have a 2000kv motor for it and planned on running a pair of 4s batteries is parallel. I am now considering running a 1000kv motor using the same batteries but in series for 8s.
No other changes. I expect the amp draw to be about half of what it is on 4s, things will run cooler and the boat should be going the same speed for the same length of time, using the same batteries just wired differently.
Only drawback is that a HV esc to run 8s is more expensive. Luckily I won't need one with huge capacity.
This is just a fun setup, no organized racing within a reasonable distance, if I did decide to travel it would be easy enough to drop in a 2000kv motor and change the esc so I could run it in "P" or 4s class.

[HTVboats]

Siberian,
I would be interested in the results there. 2 3000ma 4s packs in parallel yield 6000ma. the same packs in series stay at 3000ma but at 8S. Going from a 2000kv to a 1000kv should be identical rpm with the same boat and weight. Wonder what speeds and run times would be? Anyone else done anything like this?
Mic

[Davey80]

Great info thank you!

Things are starting to make more sense. Gotta clarify a couple things. As far as 6S LiPO, why are some listed as 25.2 volts/4.2 per cell and others at 22.2/3.7 per cell? If the battery is maxed charged and is carrying 25.2 volts, even if it's only briefly, wouldn't I want a motor that is rated to that higher number of volts?

Second thing, If the leopard 40X82 motor (rated at 3500 mwatts and 33V) is pulling 157 amps on 22.2 volt 6S, WHAT happens if the motor's amp rate is listed as lower than 157? In this case it is listed at 140. Does the motor burn up?

Third, couple other factors. I would like to sport run this boat using using really high mah batts for long runtimes. If I could get a 34 inch cat to get above 50 mph on 4S I certainly would considering going that route. I assumed it would be easier on 6S though.

Fourth, I guess I'm still struggling to see how a battery's watt rating translates into whether or not it will be enough to get the boat up to the right speed range.

Is that something that just comes with experience...where you just already know roughly how much power/speed a 2600w 40x74 motor will provide on a 34 inch hull compared to a 40x82 3500w motor?

[lenny]

Did you try using these tools yet ?
http://www.offshoreelectrics.com/conversion.htm

Also some other info hear.
http://www.offshoreelectrics.com/info.php
http://forums.offshoreelectrics.com/...-by-ReddyWatts.

http://www.tjinguytech.com/

http://www.fastelectrics.net/

[TheShaughnessy]

I wouldn't rule out the 4082 for your 34 inch cat. I'd like to offer another motor suggestion. A TP power 4060 4y at 1450 kv or maybe the 7d wind at 1550 kv. Here is a link to the chart http://tppower.com/sort.asp?class_id=4&news=44.

A well respected racer has the same size motor in the 4d wind in a 34 inch cheetah here is a video I recorded for him. http://m.youtube.com/watch?v=Cl5ebHR...%3DCl5ebHR6wR4

Don't worry too much about the weight of the motor. It's positive weight not just dead weight.

You could run 6s2p and have substantial run time.

6s is rated at 22.2 v and that is the number I would use for any calculations. It's true a fully charged 6s pack will be at 25.2 but that won't last long under load.

[martin]

Watts is amps x voltage, 6s is around 22.2v. resting cells are 4.2v per cell but under load their around 3.7v per cell. Hence 6 x 3.7v = 22.2v.

[Davey80]

Thanks for the links and info! Very helpful stuff, I appreciate it.

Mark D.

[Davey80]

Is there an easy way to pick the right motor "can size"? The power (W) ratings for the Leopard 40x65 sized cans are 2000W, the 40x74 are rated to 2600W, and the 40x82 are rated to 3500W.

If you want to put one in a 35-40 inch FE hull and be able to go reasonably fast...say 55-65 mph, how would you know if 2000W is enough...compared to 2600W or 3500W?