Fast Crackerbox ques

[ace028]

Hi, I just built a 1/8 crackerbox form plans I bought from rc boat modeler. I am running octura hardware with a x431 prop and a mamba max system I removed from my car (6900 kv mamba motor) and I am running 2 cell lipo, and a 6 cell nimh when the lipo is on the charger. I am battleing heat isuess, and am going to run water cooling on the motor and a fan on the esc. The boat is very fast, but I'm in the need for more speed. What props should I try? Its great to spank my dads boat that has 12-16 cells with my crackerbox with only a 6 cell pack. Thanks.

[PatrickJ]

The kv of 6900 is rather high for 6 cells and direct drive, I think thats the reason for you heat issues don't increase the cells it will only heat things up quicker. More speed in your case means more power to increase power cells quality must increase or cell count must increase either way heat issues becomes worse or the alway the option of a more powerful system. Then the problem might be can the hull handle the increase power.

[ace028]

well I'm installing water cooling and fans, I think that will take care of alot of the heat issues. I turned my timing down, and I think that the lipo has a larger amp output then regular cells. I am going to try the regular sub c packs and see how it likes that. I am just wondering what prop would be good for my boat, maybe the x431 is all I need.

[Fluid]

You will find that if you use a smaller prop you will go faster and have less heat issues. A 6900 kV motor is way way too hot for a direct drive 2S boat, you have probably already damaged your motor's magnets through overheating. Allowing the motor to spin up higher will let it unload and produce more power instead of more heat. Watercooling will not help the magnet damage, the magents are deep inside, away from the water coils.

Try an x427 prop, or cut the diameter of you x431 down to 27 mm. But, it may be too small for that size boat. Only trying the small prop will tell.


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[n.h.schmidt]

Hi
Jay is right . I know for a fact that a Cb will run very nicely using a X427. I have seen and run against CBs using that prop at the Wisconsin races. As fast as anything else and helped keep the heat down with the Hi rpm 27T stock motors. Myself I used a K31 CF prop with great results. I like to use a lower rpm 27T stock motor like the P2K . Plenty of low end and less heat issues. I wouldn't even want to try faster motors in the little boat . They will not stay upright very long with more power. n.h.schmidt