Sport 40 Nitro to Electric

[lohring]

Brian was driving the purple boat from the pictures in the first post. He had a very successful day. Onlookers thought it was at least as fast as the best nitro Mutts from the glory days of sport 40 in our district. Mark Anderson has held the NAMBA SAW record at 81+ mph and the two lap record at 23.52 seconds for a long time with that design. We'll see how the electric version does with those records very soon.

I now have three 8255 style boats. The data from them should be interesting for comparing propellers and scale effects. We'll post the data from Brian's day soon.

Lohring Miller

 

[57fairlane500]

Yes, the purple boat that Mark was filming is Lohring"s Q sport that Brian was driving and it works great. I am sure Brian will share the details, but I will say that if this is what we can do with FE in this class it will be a lot of fun.

 

[hugh hargett]

That was the mutt? It looked really fast.

 

[raptor347]

That was a Mutt. Setup was a Scorpion HK4025-1100, Castle Ice 200 (data logging is good), Turnigy 40C 5000 6S cells and an ABC 2116 with a bit of work on the back. 150amp average draw.

Once Kelly helped me with getting the setup geometry on the hull right, what a kick! The first half of that video was the the first round and the turnfin wasn't quite right. The second half of the video was round two, it was pretty much a point and shoot drive at that point.

I wasn't running for points, but it was great to be able to run with the nitro crowd just for comparison.

 

[Jerry Dunlap]

Here's a couple of photos. The boat's performance is impressive and Brian drives very well.

JD

 

[hugh hargett]

Super cool photo in the last frame. A 2116 would be like a 1653? if there was such a thing.

 

[lohring]

The Scorpion has a little low Kv so the rpm is a little low compared to the old nitro boat Pico's. That's why we ran a little more pitch than the 1455 3-blades we once ran. I'm sure the motor can handle more, even though it's rated at 80 amps. Nothing was getting hot even though the motor is air cooled. Leaving the motor exposed seems to be a good idea. I've used it twice with these nitro conversions.

Lohring Miller

 

[raptor347]

Super cool photo in the last frame. A 2116 would be like a 1653? if there was such a thing.

By the numbers, yes. The newer ABC props have a very different pitch/area distribution compared to the Octura blades. I trashed my good 1655 or I'd have tried it.

 

[T.S.Davis]

That was the slow motion footage right? hahaha JK

 

[raptor347]

That was the slow motion footage right? hahaha JK

Nah, just the low power setting. This hull running a maxed out Q setup would be really scary.

 

[T.S.Davis]

Looks pretty light on it's feet. If you let it all hang out I would think it would take flight.

 

[raptor347]

Looks pretty light on it's feet. If you let it all hang out I would think it would take flight.

You'd be amazed, it never gets flighty. This boat tunes so differently from any other sport boat I've run. Had to round file everything I thought I knew about setup and listen to the guys who really know the hull.

 

[lohring]

Below is a graph of the Mutt's data for an entire heat from the launch at 350 seconds through the mill to the start at 400 seconds to the finish around 490 seconds. Note that the rpm at around 20,000 (that's about 80% of the nominal 1100 Kv x 22.2 volts no load rpm) is a little low compared to nitro engines, the average current is around 130 to 140 amps, and current spikes go to over 190 amps, especially when you hit the throttle at the start. Not as visible on the graph is the voltage. Freshly charged it was 25.18 volts. At the start it fell to 20 volts and then held to between 20 and 23 volts for the rest of the race depending on load. The final voltage after the heat was 21.16. Even inexpensive lithium polymer batteries have very favorable discharge curves compared to any other battery type.

Lohring Miller

 

[hugh hargett]

For dummies like me can you tell me what your average hp and speed was from this chart.Its all above my head.

 

[raptor347]

Average current is ~135amps. Speed around 60-61mph. Call it 4 HP.

 

[lohring]

Actually I get closer to 3.6 input hp to the motor. (20x135/746) The power from the motor shaft is around 3 hp from an estimated efficiency of about 85%. That is about what a 7.5 engine would produce. The big difference is that the electric motor can, and did, easily pull 4 shaft hp. Loading a nitro motor like that would stall it.

Lohring Miller

 

[hugh hargett]

But dont forget LOHRING that the stall amperage of one of these electric motors will be way over anything your esc can do. So dont try to stall an FE motor

Lohring I know the math I just want you or Brian to do it sometime. I get lazy sorry lol.

 

[lohring]

The boat now holds the NAMBA 2 lap record for Q Sport Hydro - 25.256 sec. Still not as fast as the old nitro sport 40 record by the same boat, but this was only the first try with a boat that wasn't set up as an electric from the start.

Lohring Miller

 

[Tom Levescy]

Lohring, I can't wait to see the day that electrics begin running in the same classes as nitro here in District 9. We are running them alot more then we used to and Randy is working his tail bone off to get people to come out to race. I have a old sport 40 that ive posted photos of in the link that im hoping to build in the future. Your mutt looks great and hopefully ill get to see it run soon in person.

http://forums.offshoreelectrics.com/showthread.php?33088-sport-.40-going-FE&highlight=

 

[Tom Levescy]

Lohring, I can't wait to see the day that electrics begin running in the same classes as nitro here in District 9. We are running them alot more then we used to and Randy is working his tail bone off to get people to come out to race. I have a old sport 40 that ive posted photos of in the link that im hoping to build in the future. Your mutt looks great and hopefully ill get to see it run soon in person.

http://forums.offsho...ng-FE=

Btw its Tommy not my dad Tom.