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

Dave, can't speak directly to the particular birds you mentioned, but remember that the size of the inlet doesn't have to very huge as long as the outlet is at least twice the area of the inlet.
Walt

Thanks WT! The problem I'm up against is that these babies are streamlined and the cowling has almost no exposed forward surface area. They just go from the spinner smoothly back to the fuse. With the point of all this being to keep from chopping obvious holes in the cowling, I'm having trouble figuring out the airflow issue. I've even used "flying" cowlings with holes cut in them on some of my planes for air shows and made a second "static" cowling with no holes for mall shows and the like. Here again, have you ever tried to get spare cowlings for these birds??? Thanks again for your input.

Dave

Don't forget that heat generated in an electric setup represents inefficiency and waste. Always make sure that motor & ESC are correctly rated (I tend to over-rate things by at least 30% to be on the safe side) and are not being forced into overload by being over-propped. Electric systems should not run overly hot even without forced cooling, so be careful that you are not masking a problem and trying to correct it with over the top cooling.

How about a small ducted fan on the exhaust side to draw/blow the hot air out. I used this on a TF Spitfire powered by an RCV 90SP engine. The air intake was a slightly larger than normal gap between the spinner and the cowl and no air inlet cut into the chin.

Thanks guys! Excellent suggestions so far. I'm interested to see what others are doing in the scale realm concerning this situation. All suggestions are welcome.

Dave

Yes, interesting idea for an I/C powered model where waste heat is unavoidable.

I'm interested to see what others are doing in the scale realm concerning this situation