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Cool running cowl

PostPosted: Sun Oct 30, 2016 7:48 pm
by Strasnuts
Thought I would share my cowling pics on N86BC. I have a 130hp Rotax 914. My temps are perfect even on a 100 degree day taking off from 4500 feet elevation. I have the new cowl but didn't add the bottom piece on the lower scoop. I did add the upper piece on the lower scoop. Hope that makes sense...

Re: Cool running cowl

PostPosted: Mon Oct 31, 2016 9:13 am
by SheepdogRD
Strasnuts wrote:... I have the new cowl but didn't add the bottom piece on the lower scoop. I did add the upper piece on the lower scoop. Hope that makes sense...

I think I understand that. You omitted the bottom portion of the scoop, but installed the top of it and trimmed out the bottom of the original cowling. That raised the bottom of the cowling so it becomes a duct that directs outside air into the radiator. Air that enters the cowling nostrils and the oil cooler port exits on either side of the radiator. Is that correct?

Re: Cool running cowl

PostPosted: Mon Oct 31, 2016 7:41 pm
by Strasnuts
That's correct. Seems to be working great.

Re: Cool running cowl

PostPosted: Mon Oct 31, 2016 7:55 pm
by kenryan
Strasnuts wrote:Thought I would share my cowling pics on N86BC. I have a 130hp Rotax 914. My temps are perfect even on a 100 degree day taking off from 4500 feet elevation. I have the new cowl but didn't add the bottom piece on the lower scoop. I did add the upper piece on the lower scoop. Hope that makes sense...


I am picking up my 914 in a couple of weeks so I'm very interested. I don't have the cowling yet, so I don't understand some of what you have said. I can see that your cowling is lacking a big piece on the bottom (from other 914 installs that I have seen). Is that piece normally glassed to the main lower cowling? Is that the piece that you didn't use? Can you explain what you mean by "the upper piece on the lower scoop?"

Thanks,

Ken

Re: Cool running cowl

PostPosted: Mon Oct 31, 2016 10:34 pm
by SheepdogRD
When the rear-mounted radiator is used, there are four pieces to the 914 cowling: the basic upper and lower sections, plus the scoop bottom and the inner panel that forms the top of the scoop.

The upper and lower cowling pieces are installed on the plane with the radiator in position back at the firewall. Then the inner panel is laid in so it encloses the top of the radiator. That inner panel gets glassed in place on the lower section of the cowling. Then the scoop bottom is positioned and clecoed into place. The opening for the scoop is cut out of the lower cowling, and the belly of the cowling between the scoop and the inner panel is removed. Then the scoop is glassed in.

This produces a separate duct that handles cooling for the radiator. Everything else is cooled as in other Rotax-powered Just aircraft: by air passing through the cowling.

Airflow that enters the scoop goes directly to the radiator and exits the back of the radiator. Air that enters the cowling through the nostrils and the oil cooler opening exits at the back of the cowling around the sides of the radiator duct.

Strasnuts installed the inner panel, but he eliminated the scoop, so he saved weight, build time, and complexity.

Re: Cool running cowl

PostPosted: Tue Nov 01, 2016 2:10 am
by john2
Richard,
When did Just start supplying all the extra scoop pieces. I new that Steve Henry had some that he got developed when he first started using the turbo 912uls because of overheating but did not know Just was supplying them now. Just curious as I bought a 914 cowling in 2012 and it was only the top and bottom section so I bought the piece that Steve had developed. It's good that they are but if is first I have heard of this.

Re: Cool running cowl

PostPosted: Tue Nov 01, 2016 9:29 am
by SheepdogRD
I'm not sure when Just started supplying the scoop parts; they aren't part of the larger cowling. They're used to revise the cowling and direct more air through the larger coolant radiator. Like the larger radiator, they come at added cost.

It's interesting that Gary had a 914 in N376CG (the all-black Highlander that got white wings when it became the first SuperSTOL). That plane had a modified 912 cowling, and it cooled well with the standard radiator. The 912 cowling has a built-in inlet -- a sort of scoop -- for the standard radiator, where the larger cowling has no such opening.

Here's N376CG as the first SuperSTOL. You can (barely) see that the 912 cowling has openings for both radiators:

N376CG-11.jpg

I've been wondering if grafting a 912-cowling-style radiator inlet onto the larger cowling and mounting the radiator right in the opening wouldn't provide adequate cooling airflow over the smaller, lighter, less-expensive radiator. That might require enlarging the outlet opening, which is much smaller than the opening on the 912 cowling.

Re: Cool running cowl

PostPosted: Tue Nov 01, 2016 6:37 pm
by kenryan
Billy at the factory confirmed that the 914 cowling is now 4 pieces.

Re: Cool running cowl

PostPosted: Thu Nov 03, 2016 8:40 pm
by SheepdogRD
Yeah, that's a little confusing, isn't it? I think it's all in what we ask.

If we ask about the cowling for a 914 installation, then the cowling is 4 pieces, plus the intake duct for the airbox and another for the exhaust heater.

But the "914" cowling itself -- just the upper and lower cowling sections -- is used for other applications, and is available separately. I'm using it for a big-bore 912S on the ring mount.

Re: Cool running cowl

PostPosted: Tue Nov 15, 2016 2:34 pm
by HS-JAT
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