I was wondering how they affect the blade cp.

The 8T will spin the rotor a bit slower, but is easier on the motor. This equals longer run times, and is best for just hovering and slow FF with flat blades.

The 9T spins the rotor a bit faster, and is better for aerobatics, but works the motor harder, and will shorten the run time. Best with sym. blades for inverted flight, etc....

CT420 is correct, it all has to do with, what you want to do with the heli.

I post this alot, it's a recommened battery and motor configuration. As I mentioned, all depends on your flying needs.

Dave / Choppersrule

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Main Motor, Pinion, Heat Sink, Battery and Main Blade Configurations

When using the recommended main motor, pinion, heat sink and battery configurations we have experienced very good main motor life (better than any other models in this class). We have main motors in stock and Aerobatic Enhancement Kit equipped models with more than 100 flights that continue to perform very well.

For those who may be experiencing premature main motor wear, it is likely the result of excessive current draw causing damage to the motor rather than brush wear. Excessive current draw can be the result of using the wrong main motor, pinion, heat sink and battery configurations, improper gear mesh or constant power on blade strikes and crashes (shock damage). For these reasons you MUST follow the power system configurations recommended to achieve expected motor life. These configurations are:

EFLH1110A - 370 Main Motor with 8-Tooth Pinion:

For use with 3-cell Li-Po packs and flat bottom main blades. This is the most efficient setup for long duration hovering and basic sport flying when using 3-cell Li-Po packs. Must use a heat sink (EFLH1132).

EFLH1110B - 370 Main Motor with 9-Tooth Pinion (Included with Aerobatic Enhancement Kit [EFLH1168]):

For use with 3-cell Li-Po packs and flat bottom main blades for hovering and sport flying, with less duration than when using the main motor with 8-tooth pinion. Also for use with 3-cell Li-Po packs and symmetrical main blades for sport flying and aerobatics. Must use a heat sink (EFLH1132, also included with Aerobatic Enhancement Kit).

We suggest 860–900mAh packs for all-out aerobatics with durations up to 15 minutes and 1200–1320mAh packs for basic aerobatics and longer durations up to 25 minutes or more.

EFLH1110C - 370 Main Motor with 10-Tooth Pinion (Included with the stock BCP heli right out of the box):

For use with 8-cell Ni-MH packs and flat bottom main blades for hovering and sport flying. This is the most efficient setup for long duration hovering and basic sport flying when using 8-cell Ni-MH packs. DO NOT USE THIS MOTOR AND 10-TOOTH PINION WITH 3-CELL LI-PO PACKS AS IT WILL DRAW EXCESSIVE CURRENT RESULTING IN SHORT MOTOR LIFE, EXCESSIVE RF NOISE POTENTIALLY CAUSING RADIO “GLITCHES” AND DAMAGE TO THE 4-IN-1 ON BRIEF BLADE STRIKES OR EVEN DURING FLIGHT. Use of a heat sink is optional (EFLH1132), though it can help to improve duration and motor life.

EFLH1110D - 370 Main Motor with 11-Tooth Pinion:

For use with 2-cell Li-Po packs and flat bottom main blades for hovering and sport flying. We suggest packs from 860–1320mAh. DO NOT USE THIS MOTOR AND 11-TOOTH PINION WITH 3-CELL LI-PO PACKS AS IT WILL DRAW EXCESSIVE CURRENT RESULTING IN SHORT MOTOR LIFE, EXCESSIVE RF NOISE POTENTIALLY CAUSING RADIO “GLITCHES” AND DAMAGE TO THE 4-IN-1 ON BRIEF BLADE STRIKES OR EVEN DURING FLIGHT. Use of a heat sink is optional (EFLH1132), though it can help to improve duration and motor life.

Also, we find it is best to allow the main motor to cool to near ambient temperature between flights.

Tail Motor

When using the recommended heat sink and battery configurations, we have experienced very good tail motor life (better than any other models in this class due to the use of a specifically designed N30 motor vs. N20). We have tail motors in stock and Aerobatic Enhancement Kit equipped models with more than 100 flights that continue to perform very well.

For those who may be experiencing premature tail motor wear, it is likely the result of excessive current draw causing damage to the motor rather than brush wear. Excessive current draw can be the result of using the wrong heat sink and battery configurations or constant power on blade strikes and crashes (shock damage). Vastly excessive amounts of gyro gain can also result in increased and excessive current draw. For these reasons you MUST follow the heat sink and battery configurations as well as gyro gain settings recommended in order to achieve expected motor life. These configurations are:

8-Cell, 9.6V Ni-MH Packs

When using 8-cell Ni-MH packs for power, use of a heat sink is optional (EFLH1131), though it can help to improve duration and motor life.

It also depends on whether you have plasti-blades or not. I have a post that discusses this.

My BCP would not fly with an 8T and plasti-blades. It's fine with a 10T (but I'm worried about over-stressing the 4-in-1). I don't have a 9T, and so I have no data there.

Yeah, that doesn't surprise me... The Plasti Blades are after-market, so Horizon did not do testing with them. The data posted above is with all E-flite equipment only, I'm sure.

Changing something as critical as the composition of the blades certainly can skew the data.

Have you, by chance, measured the cord, and root to tip and compared to stock blades? I'm curious if they have the same diameter and surface area??