The Vans RV-3 plans are pretty light when it comes to the open canopy retention “system”. The suggestion is to use a string/cord to hold it in the open position – mine used a white string that stands out like a sore thumb. Aesthetically, it was horrible; functionally it was effective. It was about as low tech and silly looking as could be imagined and did not provide any protection from a gust of wind blowing the canopy closed. However; it was very simple and light. I wanted to improve this.
Randy Lervold built a spectacular RV-3B and came up with a neat gas strut/gas spring solution to this problem. I followed his lead on this which he documented on his website.
The gas spring can be purchased from McMaster-Carr and is part 4138T581. It is described as a Gas Spring with Ball-Joint End Fitting, 15 lb Force, 20.12″ Extended Length, 8.27″ Stroke.
Figuring out the mounting and mechanics of the system is a little bit of a challenge as it is impossible to reach from the outside with the canopy closed. I safety wired the strut closed, climbed into the airplane, closed the lid (canopy), and started playing with mounting points. As noted, this is not easy as there isn’t a lot of room to turn around and work on the area immediately behind your head. However; it is possible!!
Once I was convinced of the correct mounting points and geometry, I extended the strut and confirmed that those same points would still work in with the canopy open. Based on these locations, I began fabricated the brackets.
The top bracket is the easiest. I have the sheet metal rollover structure so riveting the top bracket on was pretty easy. If you have the tubular style, follow what Randy did. I used 1/8″ aluminum angle that I cut to a pleasing shape and used pull rivets to attach it.
The canopy bracket requires a bit more finesse. Again, I used 1/8″ aluminum (sheet, this time), the hardest stuff I could find in my spar bits bin. This was worked into the shape you see pictured and pull riveted onto the canopy frame.
While working on this, be very, very careful to avoid scratching your canopy. Once it is done, continue to be very, very careful – particularly with that first closure!
Conclusion
Overall, I am very happy with the modification. I’ve had it installed for several months and it works exactly as one would expect. I am a little concerned at the twisting forces that the spring introduce into the welded canopy frame and would really like a strut with less pressure, maybe 5-7 psi? I have failed to find a gas spring with the required dimensions and reduced pressure though. If you know where one can be found, please let me know.
I still have my string attached in case one of the brackets break and allows the canopy to fall open. I look forward to the day when I remove it!
Leave a Reply