Baby SV43 running gear

[Reece1]

Hi all! Newby to the fast electric side of things so be gentle please! I'll start with an introduction!

I have been model boating for about 15 years. Started with scale boats then got a mono with a modified 26cc petrol in. Used to run approx 50-60 knots. Then got my hands of one of Andy's 66" SV43 and built it with a RCMK K600, a twin cylinder 57cc, 14hp motor. Ran it for about 2 years then rebuilt it as a show piece so I don't really use any boats anymore. Until now hopefully. I use my boats in salt water here in the UK in anchorage off a real boat.

I am no longer looking for out and out speed. I am going to build twin electric for the baby SV43, this is just personal preference, prefer the look and backup of twins. I want something that is pretty torquey as I can run in 6-10 knot tides sometimes. Looking for I'd say around 30-40 mph so nothing blistering.

I like the turnigy stuff. I understand it's probably not the best quality, just hoping to get out on the water for reasonable prices plus they look good! This build is more about looks than speed!

I don't suppose I could have some recommendations of which turnigy motor to buy, esc and what batteries I should be running to achieve the above? I have been looking at their T20 3T 730/1280kv motor. But I am concerned having 2 of these is overkill but maybe I'm wrong!

Boat is a baby (1230 mm) SV43 from Andy in Germany.

Any advice appreciated. Thanks for reading!

[Jesse J]

Hi Reece, welcome!
I’d encourage you to use the search function, as there a good number of build threads and discussions to be read.
Not knowing that motor, I’d bet one would be sufficient for your needs.

30-40 mph speeds would look amazing for this hull and you won’t need much power, this hull is super efficient.
If you went with 40mm motors in the 700-900 kv range, then you could do 8 or 10s 2p on moderately small props (45-48mm) and have decent run times and a low amp system. There is plenty of room for batteries!
What paint scheme?

[Reece1]

Hi, Thank you for taking the time to reply!
I am having a rummage through old post etc and trying to learn all the different terminology etc of the fast electric world! Couple more questions if that's okay!
- In my old scale boats you could link up in series to give more Volts and parallel to give more Amps, - is this still the case for Lipo Batteries, never ventured into Lipo before.
- Secondly what value of Watts do you think I should be looking for and when you say low amp system, what kind of amps do you mean approx?
Paint scheme is my own design , metallic candy blue , black bottom and outerlimits over the roof including the name on the side - it will match my bigger one!

[Jesse J]

Series and parallel have same effect on voltage and amp capacity
Watts.. probably what that one motor had, ~5k.. and amp draw between 100-150 continuous would be really easy on electronics.
Also if you are deliberate to get 40mph by choosing motor kv, battery voltage and prop size, you could be able to go full throttle most of the time (better on esc).

[Reece1]

Okay brilliant, I take it you mean 5000 Watts per motor? That is roughly what I was looking at Amp wise! That's interesting to know, so esc prefer full throttle. Thank you for the good information!

[Jesse J]

Well, I was thinking 5000 total.. so maybe 3000 per motor? I think you will be surprised how little motor you need for twins, in a super stepped hull and not requiring more than 40mph!

[Reece1]

Okay brilliant - thank you for taking the time to reply, I will do some more digging and let you know what combination I come up with!

[srislash]

Jesse has you on the right track here. I just stepped my 45? cat down to 4s packs on my 1700kv motors, so 25,000rpm at the prop which are 46mm props it goes very well with a great runtime. If you look on the video section here you will see my HPR hull.

[Reece1]

Jesse has you on the right track here. I just stepped my 45? cat down to 4s packs on my 1700kv motors, so 25,000rpm at the prop which are 46mm props it goes very well with a great runtime. If you look on the video section here you will see my HPR hull.

Just had a look now - runs really well, sound's nice too! I am a petrol boater trough and through but they do sound nice these fast electrics - roughly what run-time do you get?

[Jesse J]

Well, with 10amp hrs, maybe 5 min? That is a pair of 10s (4s+6s) so 2p, at 10,000 mah.
You may be able to double batteries 4x 10s and get 10 min.. but need to check heat before letting her bash for 10 min straight.

[srislash]

I have one 4s 5000mah battery per side and I think it was 5 mins. That was a first go on the lower voltage(was running 6s) and have not played with other props yet. A little less pitch and blade area would yield a better runtime in my experience.
I have a 40” twin mono that runs 8s 8000mah and gets very near to 10mins with the aforementioned props.

[Reece1]

Brilliant thanks chaps, really short run times compared to what I'm used to - Really looking forward to starting this build!

[Reece1]

Well, with 10amp hrs, maybe 5 min? That is a pair of 10s (4s+6s) so 2p, at 10,000 mah.
You may be able to double batteries 4x 10s and get 10 min.. but need to check heat before letting her bash for 10 min straight.

Hi again, Hope you all had a good Christmas

The hull is currently on it's way to UK so super excited. I have been doing some research and making some calculations and have got myself into some bother - I think! So, following from your advice I have had a look around and think I have selected my motors:

Leopard LBP4092/4Y (Specs: 80A, 50V, 4200W, 700Kv) A bit high on power but not many at such low Kv

I believe this would yield approx 25,900 RPM unloaded when coupled up to 10S (37.0V)

Batteries would be Turnigy Nano-Tech Plus 5000mAh 6S 60C and a 5000mAh 4S 60C wired in series to give me my 10S (Would it be worth paralleling another set of these to get the Amps up?)

Speed controller would be a YEP 120A HV (4-14S) marine brushless speed controller (Opto)

According to calculations at this power (W) and voltage I would be requiring 113A which is obviously over the 80A rating of the motors and getting close to the 120A of the speed controller. Do I need to be calculating the Amps like I have done or will this set-up work? If I am going to get that motor below 80A I would have to run 16S (59.2V) at 70A but then over the max voltage for the motor. This appears to be a nightmare!

Hopefully that makes sense!

[Reece1]

Hi again,
Hoping someone could help me out please!
Been doing more research into this and found today on the OSE shop that the 4092 is actually 2600W with burst upto 4200W. This makes sense now as the Amp work I think.

So, would the above set-up work or have I missed something?

Happy new year!

[Jesse J]

Sounds reasonable. The trick is to not over prop, start with 45mm and maybe go up to 47mm. But you may be happy with even smaller props, depending on how you set it up.

I just remembered that I have a pair of motors/esc that I bought for this my baby sv43 and would give you a good deal on them; all new gear.
Motors: Hyperion Hs 4025 brushless out runner
Esc: sunrise model ice 120 a 4-14 cell lipo with programming card.
If interested I can post pics.
Jesse