Pushrod Boot for Elevator

So I was talking to Abby at Flightline Interiors about their pushrod boots (http://www.flightlineinteriors.com/products/construction/default.asp). They are designed to cut down the airflow for the large hole in the side skins for the aileron pushrods. But I was also thinking about the large hole in the bulkhead at the rear of the baggage bulkhead for the elevator pushrod under the baggage floor. I was thinking that using a pushrod boot there would cut down on the amount of air flowing under the baggage floor and radiating out.

Has anyone looked into something like this or is this airflow minor since the space is mostly enclosed on the cabin side?

I did not do anything with the rear holes, I would think it would be good to have airflow out of the tunnel for various reasons. I did purchase the boots for the aileron push-rods.

I would think it would get bunched up under the battery box, it's pretty tight under there between the two ribs. Maybe a smaller version would work.

After I posted I realized you could put the boot on the tunnel side but I still think it would have to be smaller.

Bill.Peyton said:

I did not do anything with the rear holes, I would think it would be good to have airflow out of the tunnel for various reasons. I did purchase the boots for the aileron push-rods.

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I think I agree with Bill. With all the air coming into the cabin, it needs someplace to exit. Leaks in the rear are probably a good thing unless you are planning on riding the baggage area.

I put put a boot on the rear bulkhead in the aft fuselage on my rocket for the elevator pushrod, and put a plate on the holes in the upper bulkhead that can be removed for summer flying, if air not exiting becomes an issue.

I made my own boots for the ailerons and also the rear elevator tube. Mine does not bunch up and I am not flying yet so who knows how well it will work. If I find I need air to exit our the tunnel through the bulkhead, its easily removable.

Bill.Peyton said:

I did not do anything with the rear holes, I would think it would be good to have airflow out of the tunnel for various reasons. I did purchase the boots for the aileron push-rods.

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Bill, just curious, how did those work? They look like they would have too large an inner hole for the hex pushrod. Or were you able to specify that it was for a -10 and get something sized for our control system?

I got the aileron pushrod covers as well from Abby. The hole is indeed larger than the hex rod, but it's designed that way. Use a small zip time to "cinch" the hole around the hexrod and you're all set.

I asked Abbey for the ones for the RV-10. They come with a draw string that you tighten up around the hex rod. They work great. I can tell you that you don't need to worry about cold air getting in the cabin, the heaters work great, along with the big heater on the front of the firewall. My tunnel is always warm (not hot) to the touch, even with fibrefrax and 1/2" insulation on the floors.

So how much pressure might be generated? Air moves with pressure differential. The boots on the ailerons are pressure balanced from side to side. The elevator would not be pressure balanced, so that force would act on the control rod.

If the flow is sealed with the other panels up to the spar, then the only boots that apply are the stick, and ailerons.

So that is theory, but no data for pressures, any practical thoughts about that?

Thanks, Bill. I'll give Flightline a call. I'm not so worried about cold air getting in; I'm trying to keep my air conditioning from escaping.

Like Bill Peyton, I installed aileron boots only. I sealed the baggage bulkhead corrugations. Sealed hinge areas on doors. I do like having the ventilation into the tailcone area and decided not to seal off the elevator pushrod. If one does decide to install the elevator boot, our huge trim tabs will not have any problem overcoming the boot forces on the control rod.

For Bill asking about pressures...There is always a negative pressure on our cabin when the two heater valves and four fresh air intakes are closed. To get the pressure equal to outside during 160 kt cruise, all we have to do is open both front large eyeball vents. So, even as sealed as we have it, we are still leaking a ton of "free air conditioning at cruise". I would imagine if we opened all fresh air and two heater valves, pressure inside would be greater than outside. A good way to test your side window installations. I have not and probably will not perform this test. I do know of one rear window blowing out in cruise over Georgia.