Sprintcat .40 - "Norm"

[crabstick]

meaning not a lot lol, would have been interesting to watch the spool down rpm

[j.m.]

It sounded like the can spun pretty easily once the throttle was off. Probably because the can has such a high mass compared to a regular inrunner's rotor. The sound of the magnets is awesome though... Sounds much bigger than it is.

[Xfactor]

even if the mass was the same the outrunners mass is so far from the center of rotation changes in the outrunners acceleration require more to start and more to stop. In my opinion the only have more torque in terms of inertail energy but they require more to get there. I think the tru differnce in motors is the weight of the rotors versus the magnetic force created by the windings and magnets.

[Xfactor]

I think the outrunners sucess lies in it simple mechanical design and all the poles they have. Theres just less gap between the magnet pulls on the rotor from pole to pole; plus theyre open where they can breathe.The only reason i feel that some of that torque is negated because the mass is so far out from the center of rotation so everytime you change the acceleration it works harder than an inrunner. I just think the good outweighs the bad in an outrunner. At any given steady rpm an outrunner probably has more torque but with a varying rpm i think the inrunner will win. I think a outrunner may be a better saw motor.In inrunner a better race motor. Just my thoughts.

X

[j.m.]

Just like your idea about the mass being far away from the center, so are the magnets and stator coils.

An outrunner will always have more toque than an inrunner of the same Kv, outside diameter, and stator length.

Jon

[crabstick]

rotating mass for the win!

Anyhoo, Boat is now finished, going to add some straps as well as the bottom velcro to the cells, and finish the cowl, its currently some balsa, soon to have a couple of layers of glass over a foam cockpit and the balsa. hopefully run it tomorrow.




Ended up removing my alloy cross braces in favor of the carbon wall, it runs from rail to rail. Found with the batts up there and the servo,rx batt and rx sitting at the back i had the best COG and the best range of adjustment. As it sits now its exactly on 33%

just waiting for some glue on the cowl to set and hope to glass it tonight.

[Rumdog]

I'd wack that skeg off the strut. You wont need it. Just more drag. These hulls turn like you wouldnt believe!

[Rumdog]

Where is the CG at with the cells way up front?

[crabstick]

COG is exactly 33% i can go back a little or forward a fair bit.

Want this to be a good rough water electric boat.. might race it with the .45 nitro's possibly. Think the skeg will help in race water. I have a speedmaster non skeg strut to try if i need to. Not gonna hack up my nice skeg strut

Have owned a couple of sprintcats and yep, they turn pretty well.

[crabstick]

Glassed the cockpit onto the cowl - 2 layers of cloth.

Just finished laying the epoxy and am awaiting it to dry! black marks is carbon dust from my file..

once its dry I will give it a few very thick coats of primer

[Brushless55]

Glassed the cockpit onto the cowl - 2 layers of cloth.

Just finished laying the epoxy and am awaiting it to dry! black marks is carbon dust from my file..

once its dry I will give it a few very thick coats of primer

Sweet!
I'm looking forward to seeing the fininshed cowl on the hull

[LarrysDrifter]

Why are the rails so long?Is it to stiffen the hull?Your work looks really good so far.

[crabstick]

Thanks Larry,

Yes length of the rails is for stiffness and longevity.

[Jeff Wohlt]

So that is the Hex 120 ESC with the USB programmer? If so, are you able to run a pistol radio with it or not? I like the new USB prgrammer with them but figure they only work with stick radios.

Nice job! I think we are all getting very excited about the OR possibilities! She is singing for sure! How do you beat that for the money?

I have a tiny one on a larger plane and can't believe it pulls the props it does...when I got the motor I laughed and thought no way...damn it is powerful for a 2628 or something like that.

[crabstick]

yep thats the esc, I have only used it on stick radio, when i used to run pistols with non compatible esc's id just remove the spring and make a ratchet, so full forward was kill the motor..

Cheers Jeff, I have just primed the hatch and put it in the server room to dry, it will get a sand and another couple coats of primer then a dash of silver, hopefully the weather is better tomorrow than today for a test