Roee Kalinsky's RV-7A Project

2008.06.26: (0.0) A pair of spring/gas/oil struts mount between the pivoting canopy frame and the fixed canopy deck, supporting the weight of the canopy when it's open (just like the tailgate of a minivan).  These are shown in DWG 48 and 49.

I started with the mount points on the canopy decks.  Now, these mount points experience a lot of force from the compressed struts when the canopy is closed.  I'm not sure what the struts are supposed to be rated at, but using a bathroom scale I measured a hefty 35 lbs. of force when compressed almost all the way.  I've also seen a few airplanes where these mount points look like they've twisted away from their original position, I'm guessing by elongating the holes in the canopy deck channel.  So I decided to reinforce this mount point by riveting an 0.062" aluminum doubler several inches wide inside the canopy deck channel where the mount points connect to it.  I also installed nut plates there to make installation and removal easier.  Note that I replaced the 8-32 screws called out in the plans with 10-32 (mostly because I messed up one of the original smaller holes).  Use MS24694-S56 (a.k.a. AN509-10R14).  Another little mod, instead of making two 1/8" thick C-729 spacers per side, I made a single 1/4" thick spacer per side.  Yes, it definitely looks better.  But I think it actually also makes the installation stronger, better resisting the twisting moment around the screws.  And of course, I rounded all the corners on these mounts really nice.  This also is not just for looks, but more importantly for safety.  This thing protrudes in a less than ideal location in the cockpit, and is likely to be impacted by the occupants' limbs in the event of a crash.

2008.09.23: (0.0) Fabricated and fitted the strut mounting blocks that attach to the canopy frame.  I positioned these such that the strut length (pivot center to center) when the canopy is closed is approximately 9 25/32".  The plans (RV-7/9 DWG 49) call for a minimum length of 9 11/16".  A sheet that came with the struts calls for 10.15", but that's a rough hand-drawn sketch that was done for an RV-6, and by the looks of it was more improvised than designed, so we'll ignore that.  I took the struts and measured a length of 9 7/16" when fully compressed.  But the geometry of the canopy is such that the struts are actually most compressed when the canopy is still slightly open.  They then extend some when the canopy is fully closed (a nice feature, so they actually hold the canopy closed), but apparently not by much.  So basically I took the dimension from DWG 49 and just extended it slightly to resolve an interference between the mount blocks and a rivet in the canopy frame.

2008.09.23: (0.0) It has been noted by other builders that contrary to what's shown in the plans, these types of struts should ideally be mounted with the cylinder side up.  This has two advantages: 1) the oil in the cylinder keeps the piston better lubricated, thereby maximizing the service life of the strut, and 2) in this orientation the oil will slow down the opening of the canopy before full extension is reached, whereas in the other orientation it will simply slam open.  Sounds like a good idea to me.  There doesn't appear to be any major down side to mounting the struts opposite to what is shown on the plans.