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Old Dec 27, 2012, 12:59 PM
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Keeping things cool

Hey guys, I'm looking for ideas. I've done a number of electric warbird conversions and have had real good luck with most of them. I've run up against a bit of a head-scratcher though and am looking for suggestions. I'm addressing keeping the motor/ESC cool enough in a larger aircraft with an scale inline cowling. There is no problem with radial-engine cowling as you just cut an opening in between a cylinder or two on the dummy engine and run the air out the bottom of the cowl. I'm doing an ESM P-39 right now and I've got this thing ready to maiden. The problem is that all the scale air scoops/outlets are designed to flow OUT of the cowling, not in. Even the P-51 has the chin scoop that you can get air in to the cowl, but not this baby. I'm also putting the finish on the ESM JU-87D Stuka and the CMP Spitfire and am running into the same situation. Plenty of OUT through the bottom, as I cut small exits in the underside of the cowl. No IN though. About the only thing I can come up with on my own is to cut some inlets in the front cowl ring behind where the spinner would be and fly with a smaller sized spinner (say, going from a 5 inch spinner to a 3 incher) so that I can get some air in the front. Won't look too good at the scale fly-ins though. There's just something about flying a big scale model with a tiny little nose up front that I'm finding hard to live with. Any suggestions on getting some air IN?? Thanks, guys!!


Dave
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Old Dec 27, 2012, 01:31 PM
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whitecrest's Avatar
Orleans, MA
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If this is your plane, it looks like there's a scoop on top near the spinner.
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Old Dec 27, 2012, 01:42 PM
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eflightray's Avatar
South Wales U.K.
Joined Mar 2003
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If you don't mind a fair bit of digging and reading, this thread may help -

ESM P-39 Airacobra Build Log & Review

It's IC powered, but a quick look seemed to show a similar problem. If you go to the thread, on the right hand side is a Search this Thread option, if you type cooling, it finds all the posts with that word in and hopefully will show how it was done for an IC set-up.

Though if you're willing to consider a non-scale spinner, why not add a non-scale air scoop. But don't forget the outlets need to be a bit bigger than the inlets to draw the air through.
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Old Dec 27, 2012, 02:40 PM
AndyKunz's Avatar
Illinois
Joined Sep 2001
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You might be surprised at just how much air you can get between a nose ring and spinner backplate if you have a good low-pressure (exhaust) opening to draw it and a 3/32" gap.

Andy
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Old Dec 27, 2012, 07:12 PM
Dude, get me some ice cream!
Felt_ripper 23's Avatar
United States, MA, Amherst
Joined Apr 2012
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They make cooling spinners. They have special holes in them that channel air to the motor. The holes don't show up when the spinner is spinning. Not sure who makes them, but I've seen them around. Maybe puffin models?
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Old Dec 31, 2012, 11:23 AM
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Thanks for the suggestions! Actually, that IS the plane I'm modeling. The "scoops" you see on the top by the spinner are gun ports. I've considered opening them up on mine at the expense of losing the scale guns. As well, I've looked at the cooling spinners. An excellent and intriguing design. This is a big plane however and the spinner on my plane is over 5 inches across. I haven't seen one that big. I'm thinking on going with opening some small intake slots on the upper area toward the sides (say around 1/4 to 1/2 inch wide by maybe an inch long) and then opening up a couple more about two to three times that big on the bottom. Should be minimally noticeable, especially if I open them up right near the gun ports. Thanks again for all the excellent suggestions! Dave
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Old Dec 31, 2012, 11:33 AM
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There is no reason why you can't cut/drill your own cooling holes in your spinner. You could even use that Cannon in the centre of the spinner of the real thing and modify it to actually be an air inlet. Of course this all relies on your spinner backplate having cut outs in it to let the air through.
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Old Dec 31, 2012, 02:25 PM
Dude, get me some ice cream!
Felt_ripper 23's Avatar
United States, MA, Amherst
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Quote:
Originally Posted by luke352 View Post
There is no reason why you can't cut/drill your own cooling holes in your spinner. You could even use that Cannon in the centre of the spinner of the real thing and modify it to actually be an air inlet. Of course this all relies on your spinner backplate having cut outs in it to let the air through.
They can't be ANY old holes. They take months of testing to get the right amount of cooling.
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Old Dec 31, 2012, 05:13 PM
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You might try cutting some holes on the underside of the nose, directly behind the spinner. Cover them with fine brass screen then paint, fogging the color on very gently. the painted screen blends into to the surrounding fuselage nicely and flows enough air to keep things cool. Be sure not to plug the screen with too much paint, however.
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Old Jan 01, 2013, 04:35 AM
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Joensuu, Finland
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Or maybe fudge with the nose gear doors. I bet they didn't close that accurately in the war time full-size planes either...
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Old Jan 01, 2013, 04:52 AM
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Quote:
Originally Posted by Felt_ripper 23 View Post
They can't be ANY old holes. They take months of testing to get the right amount of cooling.
What's the right amount of cooling, we aren't cooking a cake here. The more air we can get in the better and i'm sure any holes will be better than no holes. But there are several products from well establised companies that he could just try to replicate, if it's not perfect he may not get the maximum amount of air but he might get 90% of the way there.
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