When Mark Langford came up with a canopy hinge retrofit, I was pumped!

I had problem with the side hinge on N5391M. The screw heads were pulling through the installation holes. To compound the issue, the screws in the canopy frame were wet mounted in flox; removing them was an exercise in futility.

I tried to guess Mark's construction methods and came up short on the amount and type of carbon fibre he used to build the hinge blanks. I used the only carbon I had and a 10 layer laminate only measured out to .112”, a long ways from the .250 thickness dimension Mark cited on his site. As true to his form, Mark responded with answers and part numbers when required. That made an order for additional materials easier. I ended up using about 2 pieces of carbon fibre that roughly measured 2'x2.5'.

Carbon fibre hinge straps

I ended up with 15 additional layers plus 4 doubler-layers at the pivot point to gain the required stiffness. Mark did a great job of documenting the basic process.

 I reverse-engineered this from Mark’s photos of his hinge blanks that looked to me about 15” long with about 4” bonded to the canopy frame. My blanks ended up just a bit longer at 16”.

Mark cited a problem where he had to clearance the hinge blanks around the curved sides of his installation. I followed his recommendation and built the pivot brackets Mark designed about ½” taller and mounted them on top of the longerons with the pivot about 18” aft of the firewall.

Hinge pivot brackets

I aligned the pivot brackets using the 4’ long 3/16” rod used for aligning the tail feather hinges. Remember all the way back then in your construction sequence when you mounted those hinges? I used the #8 screw Mark recommended to lock the brackets into place. I countersunk the machine screws to maximize clearance for the bushings.

I think no 2 KRs are built exactly alike. N5391M has a removable forward deck/ fuel tank assembly. My canopy frame has an aft stiffener bow of ¼” plyfoam bonded into place with a single strip of carbon. This increases the overall rigidity of the frame considerably and I think it makes the structure better suited for the hinge retrofit.

Canopy frame stiffener

I am awaiting delivery of the gas springs. Well, that and a new condition inspection!

I'd guess that I completed all the work in less than Mark's 25 hours; maybe because he did all the figuring & I just followed along so I didn't track time or costs, sorry. It was an easy mini-project for anyone who is operating and maintaining a KR-type aircraft. Please fire away with questions and I'll do my best to fill in any missing information.