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Old 08-19-2019, 04:55 PM
SeanB's Avatar
SeanB SeanB is offline
Join Date: Dec 2006
Location: Colorado Springs
Posts: 563
Default Engine Cowl Level

I'm in the process of installing my pink engine cowl. Already worked on the front ring and nesting issues. Still have some slight interference on the outboard curves, just aft of the intakes. Cut some of that off already. I've noticed once I set the spacing and height behind the aft spinner plate, I see what appears to be a difference in height between the right and left intakes in relation to the plane and ground. I can still "twist" the front of the cowl and affect change.

My question: Would it be good to get plumb bobs, attach them to the upper horizontal flanges of each intake, then move things to make them the same? The bottom of the flanges are not trimmed all the way yet, so there is a difference from that point. I'm thinking I need to do something to "level" the intakes relative to the plane, or it will turn into bigger issues later.
Hope this makes sense.....thanks!!!
Colorado Springs, CO
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Old 08-20-2019, 12:38 AM
RussellT RussellT is offline
Join Date: May 2016
Location: Albany Western Australia
Posts: 69

Hi Sean,
I have just been through the process of fitting the Pink Cowl to my RV 3 and I had the same differences that I think you are describing, essentially with mine one side of the cowl appeared to be moulded higher than the other and the whole top cowl seemed to have twist in it that sitting the front in place saw the rear way off and vice versa. There is also a forward/aft difference in the prop blade to cowl spacing at the inlets as well, I surmised that it is supposed to be that way?
Long story short to make it fit I leveled the fuselage fist then with a laser drew a level line through the centre of the prop hub and down the sides of the fuselage beyond where the cheek extensions would end. This line is where the cowls meet and the tapered cheek extension ends. I then concentrated on getting the inlets level and symmetrical, the now out of whack left rear of the cowl fitted the firewall curve well enough but was sitting nearly 1/2 inch high at the cheek extension, I slit it with the dremel 7-8 inches up the cheek line to make it fit, then trimmed just enough of the top and bottom cowls to meet the laser line. Lots of other minor filling and sanding required at the front as well. It's not perfect but I have the first time builder excuse to fall back on, (the next one will be better!). It ended up fitting OK despite looking like it never would at first. Good luck with yours.
RV 3B. Very slow build. Now learning about paint..
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Old 08-20-2019, 06:32 AM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 5,387

Yes, level them now, level against the longerons. I think DanH has a post with picts talking about this. Just rotate on the firewall to get the top level, then set openings evenly with the bottom. Just take care to ensure that removing and reinstalling the upper is repeatable to the same position. Clecos, holes, screws, something.

Painted 6.11.2020
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Old 08-20-2019, 08:59 AM
SeanB's Avatar
SeanB SeanB is offline
Join Date: Dec 2006
Location: Colorado Springs
Posts: 563

Russell and Bill,
Thanks for your comments and ideas. I think this will get me back on track!
Colorado Springs, CO
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Old 08-20-2019, 07:36 PM
FinnFlyer FinnFlyer is offline
Join Date: Aug 2018
Location: Bell, FL
Posts: 316
Default RV-4

I started out with the best intentions to get the side hinge lines accurate and level with fuselage longerons to within 1/16". HF rotating laser level. Months of working on it, on and off.

I did not want to get into major surgery on it, and I wanted the upper cowl cheek bows left/right to be close to the same distance to longerons at the firewall and also symmetrical inlets. Why I ended up with nearly 1/2" difference between left and right side hinge lines to floor, I do not know. (Wings off, so final numbers may be different.)

When I got to the point of nearly giving up, I relaxed my precision goals.

I have yet to discover why the cowlings are made with a 1/2" or bigger gap to the spinner on the right side compared to the left side. The engine offset really does not explain it. My cowling is the greenish and honeycomb generation.

Forming the cowl cheek extensions out of alum took several weeks (taking a lot of breaks). Again I think one of them ended up 1/8 or 1/4" off the ideal parallel line to the longerons. Why the drawing notes that they should end 7 1/2" below longerons, I don't know. I calculated 6 3/8" from the drawings, I think.

RV-4 -- Building
N46AZ RV3-B Mazda 13B EFI -- Bought -- Flying
N993FL RV-3A Mazda 13B NA 575 hours

Last edited by FinnFlyer : 08-20-2019 at 07:57 PM. Reason: Added more text.
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