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Old Oct 15, 2003, 10:45 AM
LedKitty is offline
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I even seen a house fly!
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Joined Oct 2003
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Small prop, big cowl --> bigger prop, bigger spinner?

Hey gang!

I've got another question! *drumroll*

Ok, say you're going to be building a plane from scratch, and you've decided that you're going to be using a direct drive 400 motor with a 6" prop. Now let's also say in the interest of scale that the aircraft you're building is of the radial engined type with appropriately shaped cowl and that at the scale you're planning on building the bird, the cowl winds up to be, say... about 3" in diameter.

Wouldn't that make for a lot of engine cooling and really not all that much useable thrust left to propel the thing?

Now if that is the case, would it not be possible to simply use a larger diameter prop with an oversized spinner to decrease the useable prop area in order to reduce the load on the motor? Or is it a question of a larger diameter giving higher tip speeds that puts the load on the motor?

Despite my aircraft maintenance training years ago, it seems I have forgotten more than I know unfortunately, so if anyone's got answers to this one, I'd love to hear them!

This is the aircraft I'm planning to build:

I started a thread for it in e-zone/power systems called "electric twins and pusher-pullers". Vintage1 and I were yabbering on about it all day yesterday!

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