[Kevin Horton]

I need two canopy frame measurements, and it is a long drive to the hangar and back to measure mine. I'm hoping that someone whose canopy is still in the garage could make two measurements for me.

I need the following approximate dimensions:

1. The length of the curved tube that sits just behind the passenger seat, joining the left and right sides of the canopy frame.
2. The distance from the aft edge of the canopy frame to the curved tube that sits just behind the passenger seat.

I need to find a piece of cardboard big enough to make a template so Terry can make a piece of cloth as shown in the picture below.



I took that picture at Oshkosh 2008. The piece of cloth is part of an interesting scheme to stop the infamous draft of cold air that comes under the canopy skirt and hits the passenger in the back of the head and neck. I've fiddled with things under the canopy skirt to block that air, and some flights it seems to be just fine. But, I am convinced that due to the three different materials involved (aluminum fuselage, steel canopy frame, and fibreglas canopy skirt), each with its own coefficienct of thermal expansion, that it will be difficult to find the right amount of weatherstripping to put under the canopy skirt for all temperatures. You get things just right for temperature X, then go flying in temperature Y, and everything fits differently, and your wife whines about the arctic blast on her head and neck.

The idea behind this piece of cloth is that it prevents any air that comes in between the rear of the canopy skirt and the fuselage from getting over the curved tube behind the rear seat. That curved tube ends up in a reasonably predictable location, and you put weather stripping between the curved tube and the fuselage skin to keep air from coming through there. Add more weather stripping vertically down from the tube to the bottom of the canopy skirt, and in principle you have left no way for the air that is under that cloth from getting into the cockpit.

I plan to try this idea out, to see if it holds water, or blocks air, or whatever. I'll report back one way or the other, once I have reached a conclusion. But, first, I need to take a piece of cardboard to the hangar, and I need these dimensions so I can be sure to take one that is big enough.

Thanks.

 

[Bubblehead]

Kevin,

I have a tracing of it at home, but I'm still at work. I will make the measurements when I get home in about an hour and post them if somebody else has not already done so.

If you would prefer I can scan it in at work in the morning and send the tracing.

You're doing almost the same thing as I am, except I was going to make a thin fiberglass part to sit over those tubes and provide a flat surface for a seal or weather stripping. I agree, the curved tube goes down toward the fuselage in a nice predictable fashion. I don't think coeficient has much to do with the variablility though. The canopy skirt is kind of flexible and depending on how much cabin air or cabin heat air is coming into the cockpit, airspeed, angle of attach etc. the skirt flexes and lets more or less air in.

John

 

[Ironflight]

Hi Kevin - just saw your message and walked out to the hangar - 20" by 20" is the answer - doesn't look "square", but those are the numbers, measuring with a flexible tape across the top of the curved lateral tube and straight from the tube back to the rear tube of the canopy frame.

Paul

 

[Kevin Horton]

Thanks Paul. I really appreciate it.