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RV3Kev 01-28-2020 05:40 AM

Dear Paul

Whats the strategy with the foam when forming the canopy skirts? I would have assumed you have would have to have the canopy frame located on the fuselage to get the right shape

David Paule 01-28-2020 09:21 AM

I'm not using the aluminum canopy frame. The plan is to make the fairing, add the flanges for the canopy, and then reinforce the fairing to make it an integral frame.


David Paule 02-07-2020 03:20 PM

Mud on Foam
After some more work shaping the foam, I was ready to seal it. The main issue was that I?d shaped it a bit too far on the sides in the middle, losing some of the compound curvature that you ca see in the top center. I needed to build that up and fill in some gaps that remained in the foam mold.

Drywall compound is the answer. It allows a build-up, the consistency is the same across multiple layers and that avoids sanding discontinuities. Also, it?s cheap and I didn?t have to mix it. Normally, I would not permit this anywhere on the plane, but since this is a mold, not a flight part, it?s okay here.

This is after I?d just started on the right side. Previously, I?d verified that the drywall compound will stick to the foam. I'm just using a yellow plastic epoxy squeegee for this instead of my drywall tools. They can't handle compound curves.

And here?s the other side ready to dry.

The instructions say to apply it in relatively thin coats to avoid cracking as it dries.

For actual drywall, I?d try very hard to smooth the surface at this stage and avoid sanding. In fact, that?s a difference between a drywall pro and a beginner. The pro doesn?t need sandpaper, or at least not much. Here, with the compound curved surface, that?s difficult, and also I don?t need a finished paint-ready surface since it?ll be covered with plastic.


David Paule 02-13-2020 09:26 PM

Waiting for drywall compound, aka "mud," to dry means that I needed to find something else to do for a while. The F-319 (or it might be F-317 or F-318, it's called all of those. But on drawing 22, it's F-319) aft deck was cut out a while ago but not drilled for installation. It's intended to be riveted to the longerons and the F-309 bulkhead. On my plane, it'll be attached with screws so that I can remove it for access to the area.

I measured where the holes should be and marked some to avoid drilling until later, just in case the horizontal stabilizer blocks a portion. Then since the .040 aft deck was opaque and I couldn't verify the longerons under it, I overlaid a bit of that .030 Lexan that I'm using as patterns and transferred the hole locates to that. Placing it over the longerons, it was obvious that I needed to shift the hole locations just a bit outboard for better edge distance. No problem, since I could see exactly where to put them.

The .030 Lexan is sourced at McMaster. It comes with a matt plastic protective layer, much like the blue vinyl we enjoy so much, except that it's translucent. It easily holds the Sharpie marks and the sheet is stiff enough that It makes superb patterns.

Once the Lexan template was overlaid on the aft deck, I used my handy Verits optical hole punch to punch through the Lexan into the aft deck. The next step was to drill the holes to #50. Why #50? Because that's small enough that if necessary, I can walk the hole to a slightly better location, and also because a Sharpie just fits and I was able to mark the longerons with the hole locations.

Removing the aft deck, I checked the hole locations on the longerons and verified that they were acceptable. Then I pilot-drilled through both the aft deck and the longerons with a #4The large access holes still need to be made.

The large access holes still need to be made.

You might notice a small part at the forward left of the deck at the bulkhead. That's an oopsie. I'd drilled a hole for the OAT sensor in the wrong location and that conflicted with where the screw hole needed to be on the aft deck. I made this small part to get to a better spot. After the photo was taken, I trimmed the part to make it smaller. You can see the new OAT hole above it on the bulkhead.

The mud is coming along nicely. It's just slow, is all, in case you were wondering.


AndyRV7 02-14-2020 09:34 AM

Looking good. Thanks for the big pics!

David Paule 02-14-2020 08:12 PM

Trial Fit, Nothing More
The aft deck needs three holes cut in it for access or lightening or something. The location of those depends on where the horizontal stabilizer goes. With the aft deck clecoed to the longerons, I pulled the stabilizer down from the rafters and clamped it into position. Except for fore and aft, I made no effort to align it. I even left the protective bubble-wrap on.

The forward flange of the inboard nose ribs on both sides are flush with the skin. These interfered with the aft top skin, the turtledeck. The interference was small, maybe .090 spanwise and perhaps 1/4 inch long, and just on the bottom of the stabilizer. I trimmed these with a Dremel and a sanding drum, finishing with a small fine file.

Later, talking with my mentor, I learned that this is common on RV-4s and Rockets, too.

After clamping the stabilizer in place I measured where the various mounting parts will have to go and took this photo.

While I was tempted to bring the vertical stabilizer down from the rafters and clamp it on, too, I refrained. We all know where that would lead: lining these parts up and hanging the elevators and rudder. One of these days, but not today. Instead, I put the horizontal stabilizer back up in the rafters for now.


David Paule 02-21-2020 08:39 PM

Aft Deck & Fairing Compound Curve
The fairing mold is nearly there. I'm currently working on eliminating waves in the surface from the sanding. Even though I'm using longboard sanding, I'm still getting them. Fill and sand, and they're improving.

The photo shows the compound curve in the surface that I'd mentioned.

The aft deck is getting closer, too. The access holes are in it and the left forward flange repair is riveted on.


David Paule 02-23-2020 08:09 PM

Canopy Latch Parts
I've been continuing to add more drywall mud to the canopy fairing mold in very thin batches, to fill in some fore-aft waves that I developed during sanding. By keeping it as smooth as possible, little new sanding has been needed. This weekend, five more coats went on. There's no photo because well, you've seen what it looks like.

In the meantime I made the parts for the canopy latch. The canopy will be a tip-over with the stock latch shown on drawing 33.

This airplane will have some differences here, although the general concept is very similar.

1. The canopy latch will be forward to latch.

2. Instead of the spring holding the system in the latched position, there's an over-center cam that either holds it fully closed or fully open.

3. This is still somewhat TBD, but there will be an aft-canopy hold-down device.

Here are the parts. They are still unfinished and can change.

That's the original welded part on the left, the gold part, after it was cut down. The handle is now an assembly of the two diagonal pieces. The flight hardware is shown (one rod-end should face the other way) even though the aluminum is unfinished. The knob fits on the right-hand part. The cam is that funny-shaped part at the top. It rides on the bearing at the top of the handle. The cam pivots at the right and its spring attaches to the left.The aluminum parts are all 2024 from the scrap bin.

Just something to work on. I've been accumulating bunches of things over the years that get attached at a later date. For this assembly, I made three iterations out of plywood and one iteration out of Lego parts to try out before I cut metal. Each time I made improvements, simplified things and tweaked the "feel" of it. Two of the iterations including the Lego one, were a totally different configuration.


David Paule 02-28-2020 08:27 PM

Started the Avionics Shelf
Since the canopy fairing will be a rather large fiberglass project, and I haven't worked with the material in more than a decade, I decided to make the fiberglass avionics shelf first.

The wooden mold was made of plywood some time ago. For mold release, first I filled the various defects and put a fillet radius on, and then I taped it all up with shipping tape. And followed that up with three coats of mold release wax, polished shiny.

Only the part with the back plate (and in front of that) is needed. The right two or three inches of the body is just excess plywood.

Fore-aft is in the foreground to background direction in the above mold photo.

There's a return lip behind the vertical piece of the mold in front. The vertical piece nearest us will become the switch panel.

I taped a piece of plastic down on the work bench and outlined the fiberglass that I'll need. On top of that is the bottom peel ply, and behind are the five layers of fiberglass:

One layer of unidirectional, running fore-aft,
Three layer of bidirectional, parallel to the mold's edges,
One layer of unidirectional, running fore-aft.

The top peel ply and upper piece of plastic aren't shown clearly, but they're there. At this point I'm all ready for the epoxy.


PaulvS 02-28-2020 08:53 PM


Originally Posted by David Paule (Post 1409590)
The fairing mold is nearly there. I'm currently working on eliminating waves in the surface from the sanding. Even though I'm using longboard sanding, I'm still getting them. Fill and sand, and they're improving.

The photo shows the compound curve in the surface that I'd mentioned.


Hi Dave,
I've been watching this with some interest and am looking forward to seeing how you build the canopy. Just curious though why the foam needs to be filled and sanded in the centre, versus just around the periphery where the skirt is going to be fitted? Cheers Paul.

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