air pressure behind spinner?

[nupeswv]

I have an electric sailplane using a brushless Mega direct drive (16/15/5) I was wondering if I put cooling holes through the mount to match the ones on the motor will it be of much use? The folding prop mount is a solid plate that covers this area with about 1/32" gap. Is the air in this gap going to create positive or negative airflow through the front holes because of the air being forced around the spinner going by? thanks

[Salto]

Assuming that your motor has holes in each end, then if you block off one end with the front bulkhead then you aren't going to get any airflow through the motor. Therefore you should cut matching holes in the bulkhead. Whether air flows in or out through the spinner gap doesn't matter, at least you are getting some airflow through.

See this thread (and the one refernced in it) for more info on this subject. http://www.rcgroups.com/forums/showthread.php?t=257604&highlight=cooling

Graham.

[markdrela]

The pressure at the spinner gap depends on the local shape of the spinner/fuse combination. If the spinner is too short so there is a "hump" at the gap, the pressure will be low and hence the flow will probably go forward through the motor and out of the spinner gap. If there is no spinner base plate, then the prop hub will also act like a centrifugal impeller, increasing the flow even more.