Feb 16, 2021     More cleanup - (3 hours)       Category: Canopy

Removed last canopy rail from fuselage. Removed tube/tab assembly from this rail and cleaned everything up.

Finished cleaning up other pieces.

After much thought, I've decided to rebuild the plane without the canopy jettison feature. It will be much simpler to rebuild this way and since I'm not going to get it cleared for aerobatics, there's no need for that feature. Most GA aircraft don't have a jettison-able canopy or door so this won't be an issue. The biggest reason I'm going to skip the jettison feature is one of the tube/tab assemblies is missing. The plane requires 4 for the two canopy sections. This piece is so complex and well beyond my manufacturing capabilities. I'll use the existing adjustment holes that are in the canopy rail to screw the hinge to. This will allow the canopy to open and close exactly as the original did. In fact, it will still look entirely original. I'll have the jettison cables and latches operational but they won't activate the tube/tab assembly. It will be like a gun in a restored warbird. Externally the gun is fully restored but the internals are removed or modified to prevent firing.

The jettison handles are another work of art. They are machined aluminum with some spring loaded ball bearings on either end to hold into the edge of the canopy frame. The red anodizing on the handles have long since faded. I've disassembled the handles from the chains and removed the ball bearings and springs so that I can re-anodize the handle. I removed the grease and rust from the chains and the supporting pins within the canopy frame. Lastly, I applied some new bright red to the engraved lettering.

The engraving says EJECTION VERRIERE meaning Glass Ejection and 1/4 DE TOUR ET TIRER meaning 1/4 Turn and Pull.

  Feb 14, 2021     Canopy latching mechanism and cleanup. - (1 hour)       Category: Canopy

In keeping with the progress of yesterday, I did some more exploring and experimenting on the operation of the canopy structure.

As explained yesterday, the canopy hinges from the RH side of the cockpit, overhead to a frame on the LH side of the cockpit. This frame opens outwards and upwards, lifting the canopy out of the way for entrance into the plane. Loosely fitting the frame into the rear cockpit it appeared that some parts of the latch were missing. After some head scratching and comparing it to the forward cockpit, I realized that the latch in the rear cockpit had been bent. The latching mechanism is actually quite simple. The latch is simply an aluminum tab mounted on the fuselage below the canopy rail. The tab rotates about 90 degrees into a slot in the frame holding the canopy closed. There is an additional safety latch that engages preventing the main latch from rotating out. The safety latch has a light spring that holds it either open or closed.

Surprisingly, the latching mechanism is only accessible from inside the airplane. As originally built, there are no provisions to latch or unlatch the canopy from outside the airplane. This certainly won't meet today's safety requirements. All aircraft require the ability to open from the outside. And it's not practical from the security perspective.

I have some ideas for some simple and tasteful modifications to permit the opening from the outside.

In typical Dalotel design, the latch rotates around a custom built threaded screw. The screw passes from the inside of the cockpit, through a threaded boss that's welded to the fuselage frame. The screw has a very thin head so there's little chance of catching on it in the cockpit. The head is so thin, there is no depth for a screwdriver slot or socket. Since there is no slot on the head, the end of the shank is slotted. This means one passes a screwdriver through the threaded boss to reach the screw at the opposite end. The screw is about 3/8" diameter (yet to be measured, and there are no drawings for these parts) but the really strange thing is it has LH threads. Why in the world would they have made these screws and bosses LH threads? The latch only rotates about 90 degrees and for every 1/4 turn one way, it has to be turned 1/4 the opposite way. It wouldn't make a difference if it's LH or RH threads.

After figuring out how some of these pieces worked, I spent some time cleaning up some of the grime and oxidation that have built up over the 50 years. There's a copper spring tab that's part of the canopy jettison latch. I gave it a slight polishing yesterday but it was still black. Today I gave it the once over with the dremel tool with a wire brush. It's cleaned up so nicely it's got some bling.

  Feb 13, 2021     Canopy review and discovery - (2 hours)       Category: Canopy

After a long hiatus on the project, I'm easing my way back in with some small items. That, and the shop is still filled with my DR-107 that I'd worked on over the winter so I don't have a lot of room right now.

It seemed like a great opportunity to look at the canopy. There are no real drawings for the canopy but its operation is mentioned in a couple of the articles written when the plane was introduced. In some aspects it's quite neat. In other aspects, it's mind boggling. Rube Goldberg had nothing on Michel Dalotel.

The canopy is simply a flat sheet of plexiglass secured on either side to the fuselage and bent overhead. It's no different than a piece of paper held at opposite ends. Bringing the ends closer together causes the paper to arc upwards or downwards. With the Dalotel, the plexiglass is secured to a hinge on the RH side of the cockpit and bends overtop the cockpit to a hinge secured to a frame on the LH side of the cockpit. The frame on the LH side pivots 2/3 of the way up the canopy side. As the frame is closed, the sheet of plexiglass bends around a ledge ahead and behind the pilot's head. This ledge provides the correct curvature of the sheet of plexiglass and when the frame is closed and latched, the plexiglass is snug. To open the canopy, the frame is rotated outwards and upwards causing the plexiglass to straighten out as the frame travels. Simple and elegant just like the articles from 1969 described.

The complex part of it comes into the ability to jettison the canopy in the event of an emergency. Most hinged canopies use a hinge pin that can be quickly removed by pulling a handle in an emergency. Not on the Dalotel. The previously mentioned hinges on either side of the canopy are not bolted or riveted to the canopy frame. Rather, the hinges are secured to 6 tabs that will release the lower portion of the canopy hinge when the jettison handle is pulled. Getting more complex? Just wait...

These tabs that secure the canopy hinge are mounted to a tube that runs inside the canopy frame. The canopy frame is notched in 6 places, each notch lining up with one of the 6 tabs. There are some unique rivets on the lower half of the hinge that pass through the frame and are secured when the tube/tab assembly is rotated towards the rivets. The rivets are not rivets as we all know them. They aren't clamping anything together, rather they have two heads, like duplex nails used in house framing construction. Each tab hooks onto its respective rivet between the two heads. The tube is held in place and prevented from rotating within the canopy frame by a complex latching mechanism. The latching mechanism secures a ball bearing in place that nests into a pocket in the tube/tab assembly. When the jettison handle is pulled, the latches on either side of the cockpit are released, causing the ball bearing to come out of the pocket, allowing the tube/tab assembly to rotate away from the rivets, releasing the hinges which hold the plexiglass into place. One of the elegant features of this design is that if one side hangs up and doesn't rotate fully, the release of tension on the other end of the plexiglass will allow the hung up side to also release. Of course, the system isn't as simple as that. There's more to it.

The 6 tabs that are mounted to each of the tubes (one tube per each side of each cockpit) have a some additional work to them. To allow adjustability to each of the tabs, they are actually part of a sleeve that rotates around the outside of the tube. The sleeve is held in place and adjusted by a beautifully machined brass wheel that is mounted in line with the tube. Each brass wheel is larger diameter than the outside diameter of the tube and each wheel is protrudes from the tube on either side. The brass wheel is knurled and it has a coarse thread to it. The brass wheel is secured to an allen screw that crosses the tube from one side to the other. As you turn the allen screw, it rotates the brass wheel. As the brass wheel turns, it causes the sleeve with its tab to rotate independently of the tube. This allows infinite adjustability for each tab providing the ability to adjust the tension on the plexiglass and the security of the canopy. Finally, to add one more level of complexity, there is short section of extremely fine music wire that also crosses the tube, parallel to each allen screw. This music wire catches the knurled edges of its respective brass screw, preventing it from turning on its own...

There are holes on the inside of the canopy frame which line up with each of the allen screws. This allows one to adjust them once everything is assembled and the canopy is closed.

Complex? YES.

Make sense? Maybe not. It took a couple of hours of head scratching with the pieces in hand before I was able to figure it all out. Fortunately there's a piece of original plexiglass and hinge left. If I didn't have that piece, I wouldn't know about the duplex rivets and how they hook into the tabs. It took quite a while of cleanup and experimenting to discover that turning the allen screws turned the brass wheels, which rotated the sleeves. There were many "A-ha" moments when figuring this assembly out.

More interesting details to come. More complexities and weird assemblies.