What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

RV-3B Dave's in Colorado

Epoxy and Microballoon Practice

It's been a while since I worked with epoxy and microballoons and foam, and since I had enough stuff to work with, I decided to make a practice kit.

Practice%2BStuff%2BS.jpg


Starting at the far back, is a roll of fiberglass cloth which I didn't use today. Just in front of that is a bag of microballoons, left over from the sailboat I had the first decade of this century. Then the tall can is some epoxy resin, Rhino or Jeffco 1307 LV, and to its right is a quart of the associated medium hardener. At the right of the hardener is my mixing cup and the two pieces of scrap foam that I glued together with the microballoon and epoxy mix.

In the foreground we can see the gram scale and the syringes I used to meter out the resin and hardener.

This is the first time I'd used this resin system. Steve Smith recommended it, and so far, based on this one trial, I like it. It's available from Aircraft Spruce. Previously I'd mostly used the West Systems epoxy.

The gram scale measures and reads down to 1/100 of a gram. The closest I could get to the goal weight was about .03 grams and that took some doing. Frankly, I don't think that precision was necessary, but that's a guess; I don't really know.

The mix had the consistency of peanut butter. I could have made it drier and if I repeat the experiment, I probably will.

I'll let this cure completely and then carve and shape it and sand it to see how it feels.

Dave
 
My mixing method

I have the same epoxy and like it. I think the lancair guys use it.. anyway I thought I would share my mixing method.. I have an amazon scale, and little squirt bottles that come in a three pack from harbor freight. I place a little disposable plastic cup on the scale, tare it back to zero, then add epoxy (10 grams) tare back to zero, then hardener (2.2 grams). If I need more, I increase it at the same 100:22 ratio by weight. I keep the metal cans in the fridge in an attempt to prolong their shelf life. It?s super clean with no spilling. I haven?t thought about syringes, but do they leak in between uses?
 
A scale that reads in 1/10 grams is definitely easier to use than one that goes to 1/100. For larger quantities I'll use that.

The syringes definitely leak. You can see a few drip marks on the paper. I've stored them in separate zip-lock bags and will probably change to your containers, thanks, or something else.

Dave
 
A scale that reads in 1/10 grams is definitely easier to use than one that goes to 1/100. For larger quantities I'll use that.

The syringes definitely leak. You can see a few drip marks on the paper. I've stored them in separate zip-lock bags and will probably change to your containers, thanks, or something else.

Ditch the syringes Dave. Get something like wide mouth condiment squirt bottles for hardener, and a 1 qt pour bottle for resin...something easy to refill from the can.

An electronic scale is great, but can be a lot like switching from steam to an EFIS...we begin to worry about small values because it displays small increments.

I've been mixing epoxies on an old 0-500 gram beam scale since the mid 80's. I think my father-in-law salvaged it from someone's trash can.

I keep the metal cans in the fridge in an attempt to prolong their shelf life.

Don't do that. Viscosity is too high until it warms to shop temperature, and cold cans will condense water. With epoxy, capped cans and bottles last a long time on the bench.

You really want the shop, the work, and the resin at about 75F.
 
Templates

I made some templates to transfer the correct fair shape to the foam, once I have it glued up. These are thin plywood. The lines at the left are where the panel goes.

The bottom template is the center one. The others will be used on both sides of the mold for symmetry. Sorry for the background. The color and hue are really too close to the wood for a good photo.

Canopy%2BFairing%2BTemplates%2BS.jpg


Right now three of the five slabs of foam are glued on with epoxy and micro balloons.

If you've guessed that I'm creeping along, you've guessed right. These days I'm barely spending time at it.

Dave
 
Last edited:
Foam Fun

The fiberglass canopy fairing needs to fit the skin, and there were clecos poking out of it, holding the front top on. Time to screw it down. On the RV-3B, this skin is attached with a lot of #8 screws. The side screw holes got dimpled for #8 screw heads as you'd expect. The instrument panel flange wasn't wide enough for #8 dimples so I decided to use NAS8702U1 8-32 screws instead. These screws are really good: the material is 160 ksi A286, strong enough to survive a number of installations and removals, corrosion resistant and very tough - cracks don't propagate easily in that material. It's the material that many spacecraft screws are made of.

This particular part number has a #8 body and a #6 head. I had to get a special dimple die for that, and Cleaveland came through.

In this photo, the instrument panel screw, on the right, is in a #6 dimple as it should be. But the screws on the bottom (the side of the fuselage) are #8 dimples and these screws just don't fit. I included one of the standard #8 screws for comparison. Since this is merely to temporarily replace some clecos, the use of the wrong screws here is okay.

%25236%2BScrews%252C%2B%25238%2BDimples%2BS.jpg


The foam stack finally got micro'd together.

Foam%2BStack%2BS.jpg


Using a Japanese back-cutting saw, more commonly used for fine woodwork, the corners came off easily.

Foam%2BSaw%2BCut%2BS.jpg


And then I started in with my old Stanley Surform wood rasp. This was slower but before I ran out of time, I did make some progress.

Foam%2BPartly%2BSurformed%2BS.jpg


Lots more to go.

Dave
 
Foam, continued

I'd noticed that the foam block was sliding side to side as I carved on it. Not surprisingly, since the bottom was flat and resting on the fuselage longerons. Its shape prevented fore/aft motion and rotation but nothing kept it from shifting laterally.

Two small foam blocks took care of that. This photo shows the bottom with the foam blocks in place. We're looking at the bottom and the back of it. I'd brought it into the house for the glue to set up, the house being warmer than the shop.

Foam%2BLateral%2BStops%2BS.jpg


The addition worked.

I continued to shape the foam and it's a bit closer than this photo suggests, but not much. I'm using a Surform file and expect that in a day or so, I'll switch to a 36 grit longboard that I made.

Foam%2BCarving%2BC%2BS.jpg


The other side is about the same.

Dave
 
For cutting foam, there are ?hot knives? (a hot wire knife) that are commonly used for other applications. I suggest you check out any google search for model railroading and foam blocks. Foam insulation blocks are used a lot for landscaping contours in model railroading and the hot cutters avoid dulling normal knives and don?t create lots of dangerous foam dust like a normal knife does.

Model railroader magazine has had lots and lots of references to cutting foam over time.
 
Well, thanks, always good to learn about another tool. I knew about hot wire cutting for airframe parts and even have a hot wire cutter that I've used in the past. Since this is a compound curve, I didn't think it would be appropriate here.

As it is, I expect to be done with the gross foam removal shortly using the tools at hand:

Saw for the rough trim,
Surform for the coarse shaping,
36 grit longboard for the close shaping.

Dave
 
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
 
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.

Dave
 
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.

Foam%2B1st%2BDrywall%2BMud%2BL%2BS.jpg


And here?s the other side ready to dry.

Foam%2B1st%2BDrywall%2BMud%2BR%2BS.jpg


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.

Dave
 
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.

Aft%2BDeck%2BS.jpg


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.

Dave
 
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.

Hstab%2BTrial%2BFit%2B1%2BS.jpg


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.

Dave
 
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.

Fairing%2BCompound%2BCurve%2BS.jpg


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

Aft%2BDeck%2BHoles%2BS.jpg


Dave
 
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.

Canopy%2BLatch%2BDwg%2B33%2BS.jpg


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.

Canopy%2BLatch%2BParts%2BS.jpg


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.

Dave
 
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.

Avoinics%2BShelf%2BMold%2BS.jpg


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.

Avionics%2BShelf%2BLayup%2BPieces%2BS.jpg


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.

Dave
 
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.

Dave

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.
 
Hi Dave,

What grit are you using on your block?

I'd start off heavy on the mud, then cut it to shape with 40 grit. Going super coarse gives a good cut, which stops the block riding along on the surface, creating waves. Once you have the shape sorted and can't feel any weirdness, move up the grits until you're where you need to be (120?).

If you're already doing this, ignore me.
 
I shaped the foam in the middle, even though it'll get cut away, just because when I started, I didn't know how wide my canopy would be and what the shape of the opening was going to be. Since then, I marked some areas where I didn't need to fiberglass.

Except for using 36 grit as the first sanding cut, jamlip described the process well. The final shaping was in areas, sanding with about 120 grit and adding slight layers of mud here and there.

3M has a nice sanding board for the open drywall sandpaper. It's a decent longboard except for not being very long. But it was perfect for this. Got it at Home Depot in the paint section.

Right now the shape is where I want it, or as close as I'm going to get anyway, and it's as smooth as needs be. The plastic that I'll be covering it with can bridge scratches worse than 120 grit leaves.

Dave
 
Second Fiberglass Practice

The fiberglass layup of the avionics shelf reminded me the hard way of several things I’d forgotten. As a result, it is barely useable and I haven’t decided whether to make another or fix this one.

Some of the details are -

1. Leave enough extra peel ply that doesn’t get epoxied so that you have a handle by which to pull it off.

2. Ditto with the perf ply, if you’re vacuum bagging it.

3. The absorber layer doesn’t need to be oversize but that’s a whole lot better than undersize.

4. Even using plastic, try to work out excess epoxy before laying down the peel play and the perf ply and absorber layer.

I was somewhat surprised that the Jeffco epoxy I was using had ample pot life. I thought it would be a race and it wasn’t too bad. I got by with one batch. Wirejock’s epoxy quantity calculator was a bit generous. Wirejock's Epoxy Calculator

The layers I used turned out to be just right. That was uni 90, bid 0/90, bid 0/90, bid 0/90, uni 90, with 0 being the side-side direction. However, afterwards, I decided that some more uni would be better.

How did it turn out? There are a few places that aren’t exactly bubbles but more like nicely-laid-up hills. Small ones. Outside of that, not so bad. Here it is, roughly trimmed.

Avionics%2BShelf%2BRough%2BS.jpg


After that, I covered the cockpit area in plastic, using duct tape. There were a few ripples remaining in the plastic. I chose the worst place for another practice lay-up, using some scrap cut-offs from the earlier work. This was vertical and was centered over the left corner with the fairing mold, the cockpit side, the turtledeck and the tailcone side all intersecting.

The lay-up was uni 0, bid 0/90, uni 0 this time, with 0 being the longitudinal direction, left/right. That used up the scrap pieces. I used Wirejock’s epoxy calculator again, and it was generous this time, too. Memo to self - knock it down by something like maybe 10%. Here it is shortly after laying it up with the epoxy still wet and peel-ply pressed into it.

Practice%2B2%2BS.jpg


It certainly looks to me like I’ll have to work out all the ripples in the plastic, once this is off.

Dave
 
Last edited:
Cutting Fabric

Thanks!

Lately it seems as if all I've been doing was cutting fiberglass fabric for the canopy fairing. I'm using the same lay-up that I used on the avionics shelf, 1 uni, 3 bid, 1 uni, with peel ply this time on both sides. At the front and the back, the unit runs laterally, but on the sides, it follows the contour of the fairing, very roughly parallel to the canopy edge. Let's make that very, very roughly.

Cutting%2BFabric%2BS.jpg


The cutting tool I've been using is the Olfa pizza cutter. I've used it right on the table with little damage, and the blade cuts as well now as it did when I started. It's much easier than scissors, but I do have to put pressure on it.

Here is the fabric all organized and ready. I expect that as I go there might be a bit more trimming, hope not, but it's probably likely.

Cut%2BFabric%2BS.jpg


The box is the canopy box.

The lay-up appears as if it'll take about all the remaining epoxy I have left of that gallon I bought.

Now all I need is the gumption to do this.

Dave
 
Gumption Found

I laminated the canopy fairing today, all by myself. Took all afternoon and went fairly well considering everything. I must have gone through half a dozen pairs of gloves.

Right now the epoxy is curing. I?ll leave the laminate in place for at least a couple days, don?t want it to warp after I remove it.

After I was done, I noticed that the cup with residual epoxy, about 3/4? of it, was getting warm. I checked with my IR thermometer and it was 118 F. A moment later it was 127, so I carefully took it outside and left it on the patio, away from anything. Shortly afterwards, it measured 337, but the next measurement was less. Evidently I missed the peak. At least it didn?t ignite; I'd wondered if it would. The fairing itself was roughly at shop temperature and now, an hour later, does seem to be curing.

And here?s what it looks like. The peel ply is still on, and the various defect artifacts seem to be related strictly to the peel ply.

LH%2BCanopy%2BFairing%2BLay-Up%2BS.jpg


Dave
 
The canopy fairing I am making will also be the integral canopy frame. At least that's the plan. Some head scratching needed here - I seem to do a lot of that.

Why? I wanted to make something out of composite, so I decided that this would be it and didn't order the canopy frame. As I was laminating it yesterday, I had second thoughts about that idea. I seem to do a lot of that, too, lately.

Dave
 
Head scratching

David,
One option that might materialize is to use your glass fairing as the inner shell . Then to accommodate the plex/glass intersection thickness , just lay-up an outer shell. Lastofom laminated to your inner-shell and glass over that will give it good section modulus and a slot for sealant to bond the plex into. Just a thought .
 
Larry, that's a good idea, and sort of what I'm planning, except on the inside, at least at the cockpit. I'd intended that this be the exterior and with some work I think it can be.

The fairing came off the fuselage easily enough, since I’d used plastic sheet and duct tape for a mold release. The first layer of the lay-up was peel ply, and that’s firmly glued on. It’s a major pain to remove and comes off in strips and pieces. The outside was easier and now it’s all off, but it took parts of three work sessions to do it.

The fairing isn’t perfect at all, not even nearly so, but I think it’ll work. After I removed the mold and rough-trimmed the edges so that I wouldn’t get slashed by the fiberglass, I put it on the fuselage. Good place to store it for now. The far side, forward of the roll bar, looks discontinuous because it's a trimmed edge that'll eventually be cut away so that I can sit in it.

Fairing%2BRough-Trimmed%2BOn%2BS.jpg


Here’s the canopy mold after removing it from the fuselage. If you look closely at the upper right edge, you’ll see a small black tab. That’s a couple layers of Gorilla Tape that I put there for a pull handle to remove it. Since it fits flush on all sides, there wasn’t any other place to grab it. The pull tab worked well.

Canopy%2BFairing%2BMold%2BAfter%2BS.jpg


The black line was a mark to indicate where the glass should stop on the top.

I made a canopy support cradle to hold it while I trim it. Haven’t tried it yet. Because of the working height, I’ll use the canopy box as its base.

The shop has overhead radiant heating. Under the heaters, it can get pretty warm. But about 25% of the shop isn’t directly affected by that since only three of the four heaters are connected right now - I’ve left a gap in the coverage for this. I’ll be working on the canopy in that area. Since the heaters, in aggregate, are about 75% of the power of my house furnace, and the shop is 1/4 the size and better insulated, I can heat the entire shop to any safe temperature and still not melt the canopy with the direct heat. All I have to do is pay the electric bill.

The nutplates for the aft deck are finally riveted on. It was less of a job than I’d thought it would be and came out pretty well.

Dave
 
Last edited:
Thermal expansion

David,
Not that you can change it, but think about thermal expansion. Most canopies curve up and leak air . Probably not a problem in the summer, just something to keep in mind as you approach the finish line.
 
Thanks! I've got something in mind that might help, maybe. we'll see. I plan to have a canopy latch at the aft end of the canopy frame. It'll be operated by the same handle mechanism as the main latches.

Dave
 
Canopy Flange Removed

The canopy is taped and there?s plastic on the interior. I used the same 4 mil plastic on the interior that I?d used for the fairing. The outside plastic is the green cling wrap that AeroCanopy used to ship it. The yellow tape is one of the Frogtape line, for delicate surfaces. This taping is to let me trim the forming flange off the canopy. Wirejock, who?s ahead of me on his RV-7A project, recommended the tape.

I tried a Dremel diamond cut-off wheel. It gave a nice fine kerf but was terribly slow. Maybe I shouldn?t have used it to cut aluminum earlier. Then I tried Dremel?s cut-off disk and it was somewhat faster, but the ice cream in an ice cream cone would melt on a sub-zero day before that did the job. Next up was a cut-off disk in an air die grinder. That worked. Plus I got to listen to the air compressor the whole time. That Harbor Freight die grinder really gobbles the air.

Now I have these canopy flange cut-offs.

Canopy%2BEdges%2BRemoved%2BS.jpg


I lifted the canopy fairing off the fuselage and laid it on the canopy. This was an iterative process, since I had to reposition the canopy in its cradle. The canopy, unrestrained, is somewhat wider than the canopy frame that Van?s describes in the plans on Drawing 33. The cradle is cut to match that, but at the exterior surface. The plans shows how the sides of the canopy actually curve inward beyond the semi-circular, and with the canopy in the cradle, mine does too.

Once the canopy was properly positioned in the cradle, I put the fairing back on. Then came an hour of adjusting it this way and that, trying to align the two together.

Canopy%2BFairing%2Bon%2BCanopy%2BS.jpg


Fore and aft was easier than I had expected. Lateral was a bit harder, and I'm not satisfied in roll yet. I?ll probably tweak it some before I mark the canopy for trimming.

Dave
 
Clipped In

After some more trimming, 1/2” at a time, I ended up with a total of 1 1/2” trimmed off at the front and back. The overall fit is reasonable. Here’s the canopy, free of its cradle and unrestrained, resting on the fairing.

Canopy%2BFitting%2BS.jpg


Up close, the canopy edges are generally further from the fairing than I like, but I can’t trim it any more because it’s beginning to intrude on the 1” clearance I wanted around the roll bar. It would be a mild disaster if it contacted the roll bar. Back in the cradle, the gaps are considerably reduced. No surprise there, since that’s where it was when I trimmed the canopy.

Remember that the cradle compresses the sides of the canopy to match the factory frame that I’m not using. It seems to increase the height of the canopy slightly, too, so if I could hold the canopy in this restrained shape, I’d get a better fit to the fairing and more roll bar clearance - worth trying.

I made a half dozen clips from .040 that I could cleco to the fairing. Since the fairing rests directly on the fuselage skins, the only place I could cleco them on is in the area of the cockpit. Fortunately I’d marked that some time ago. Unless I drill into the tailcone skin, though, I can't add a clip in the aft portion.

Here the canopy is, clipped to the fairing. It reduces the canopy width by about an inch and increases the depth by about 1/8”, not much but a reasonable percentage increase in clearance. If you compare these two photos, you might be able to see the better fit.

Canopy%2BTooling%2BClips%2BS.jpg


Now I’ve got to figure out the next step. While I’m letting my subconscious work that out, I’ll be smoothing the canopy edges and doing some minor tweaks.

One thing that I was pleasantly surprised with, was that the canopy trimming, at least so far, was fairly straight-forward. The cradle holds it securely, and I expect that helped a lot. My air die grinder really drinks compressed air; the compressor was running for hours.

Dave
 
Last edited:
Very nice work! It’s fascinating to watch the progress through your great sharing of your photos and thought process. I’m curious what you’re plan is to reinforce the canopy/fairing junction. How much lip or overlap do you have on the inside for a fillet? What material or adhesive do you plan to use?
 
I don't have a plan yet, but I do have some of the Rutan BID and some UNI fiberglass cloth and some 3/8" PVC foam that I can use for a core if I want to and can afford the cockpit volume.

The inside of the fairing, in the cockpit area, will be trimmed flush with the canopy, and an internal flange built up from there. I'll make an outside flange first. Aft of the roll bar, it's all TBD. Right now, the fairing goes across the top past the sides of the canopy, and I'll decide later what to cut away. There will be a bit near the aft end as part of the aft-most canopy latch that I'm adding.

I'm using those materials plus Jeffco 1307 LV laminating resin and the medium hardener, from Spruce. All these materials are well-proven and reliable, which is more than I can say for my own workmanship.

Dave
 
Well, I started making the canopy flange. The edges of the cut fabric started fraying and sticking to my hands. While fighting that, the epoxy kicked off.

I pulled the flange material off and threw it away. I'm waiting on more material now since that was the last of it. The next day, I removed most of the duct tape I'd used as a mold release since it was coated in epoxy.

Dave
 
Canopy Flange Formed

The canopy got re-taped for the second flange attempt and after buying more materials, I succeeded in laying up the canopy flange. This time I used 3” fiberglass tape and 4” peel ply tape. It turned out that the epoxy remaining in the cans was just enough to do this task and I didn’t need to open the second can of the Rhino (or Jeffco) epoxy after all. Yet.

Here’s the flange with the external peel ply pulled off. There’s a bottom layer of peel ply that’ll come off when I remove the flange from the fairing and canopy.

Canopy%2BFlange%2B1S.jpg


Some work is remaining, such as trimming the edges and probably some other things that I don't know about yet.

Dave
 
Last edited:
Very nice work Dave. That was by far my least favorite part of the build. It?s all downhill from there.
 
Canopy Flange Successfully Off The Fairing and Canopy

Thanks, Rob.

The flange came off of the fairing with some difficulty. The tool that helped was a strip of 1 x .063 aluminum left over from the exoskeleton, with tapered edges. I used this to break the seal between the fairing and the duct tape under it. Then all it took to remove the flange from the canopy itself was a tapered piece of plywood and some body English. Pulling the peel ply off was its usual fun, and included swearing and a modest blood donation.

I?d put a few cleco holes in the flange and fairing to register it afterwards. Here?s the flange on the fairing without the canopy. Later, the canopy went on ok and I marked the flange for trimming.

Canopy%2BFlange%2BSide%2BUntrimmed%2BS.jpg


Dave
 
Rough-Trimmed the Canopy Fairing

After more than a little tweaking and alignment, I was more or less finally content with the position of the canopy, and re-clecoed the flange in place. Then I got out some Sharpies and started marking the fairing up. After erasing the marks (lacquer thinner, with the canopy off, of course) and redoing it I decided that it was time for cutting it out.

A die grinder and cutting disk sure use a lot of air, at least my Harbor Freight one does. With both the air compressor and the die grinder working, the noise level was significant. The day was nice and a neighbor abandoned her patio, so I reluctantly closed the garage door and did it without that open. Cutting disks, especially 4? ones, don?t cut inside radii very well, at least with my current knowledge, so this is only a rough cut. Here?s the fairing and flange. The flange is trimmed.

Rough-Trimmed%2B1S.jpg


The next picture shows the cockpit area. You may notice three lines on the side of the fairing about in the middle. Those represent the plans version of where the center of the canopy latch handle goes. I?ll adjust that when I get inside.

Aft of the roll bar, there?s a cross-strip that?s part of the lateral reinforcement. Since this isn?t using the standard Van?s canopy frame, I need that for stiffness. Just ahead of that and aft of the cockpit area is a bit of a narrow section. That?s where a lot of the current flexibility comes from, here and more so on the other side.

Rough-Trimmed%2BCockpit%2BArea%2BS.jpg


In this next one, you can see the panel and the 3.25? sunshade the I left. It seems to block about 1/2? of the top of the panel, more or less, but that?s preliminary for now.

Aft of the cross-strip mentioned above there?s a bit of a deck or gusset or something, that you can see in the top photo. Since the plane already has an aft deck, I suppose I can?t call it that. This is the base for the aft-canopy latch which is still unbuilt. It?ll hold down the aft end of the canopy under air loads, and be latched and unlatched by the same handle that controls the main latches.

Rough-Trimmed%2BPanel%2BArea%2BS.jpg


I allowed 3/4? all around (except at the hinge, of course) for overlap around the cockpit and for blending the flange to the fairing.

After all the rough-cutting and cleaning, I taped the right side of the fairing to the fuselage and opened the canopy fairing. I wanted to make sure that it cleared the roll bar, and it also gave me an opportunity to evaluate its overall stiffness. In this case, it?s overall flexibility. I placed the canopy on and lifted the assembly far enough to peek and see the canopy clearance to the roll bar. It?s sufficient.

Dave
 
Very nice

I really like how that's turning out! I did a similar flange for the FWD section on my -4 to transition onto the aluminum skirt. Are you going to glass it in? I drilled up my glass flange as though it was metal, and riveted it on with Proseal as a bond/seal. All painted, it looks just like a very well fit aluminum flange, similar to the rest of the metal construction.
 
Stunning work David.

Will the aft end of the frame have any kind of mechanical latching?
 
The fiberglass assembly that you see is both the fairing and the canopy frame. Or it will be, once a lot more stiffness is added to it. There won't be any aluminum in the frame or fairing except for the latches and the hinge.

The latches will include both the forward and aft latch bars that the plans shows, but I'm adding a new latch at the back end. I suppose that the "aft" latch bar will be the middle one; nomenclature is becoming a bit of an issue here.

Latch%2BLocations%2BA.jpg


The aft aft latch concept is a bit hard to describe, so I won't, but reasonably simple in concept. It'll be operated by a control connection to the latch handle. I haven't decided yet if a pushrod will work or if I need a push-pull cable, but I need to decide that before I glue the canopy down.

That brings up one of the never-ending debates -- how is the canopy to be attached? It'll have an inner and an outer flange and be glued to both with 3M's 2216 epoxy. You can see the outer flange in the photo. The inner flange gets fabricated later.

There won't be any rivets, Sikaflex or other stuff. Just the 2216.

Dave
 
That brings up one of the never-ending debates -- how is the canopy to be attached? It'll have an inner and an outer flange and be glued to both with 3M's 2216 epoxy. You can see the outer flange in the photo. The inner flange gets fabricated later.

There won't be any rivets, Sikaflex or other stuff. Just the 2216.

Dave, the Showplanes setup glues the inside surface of the canopy to the outside of a fiberglass flange on the primary glass frame structure. The plexi has holes drilled in it along that flange, alternating 1/8" (for clecos) and 1/4".

I used is ordinary Hysol 9430, but I think Bryan is now recommending a Loctite product. Anyway, the canopy gets glued to the flange, secured by clecos, and the adhesive squeezes up through the 1/4" holes, forming epoxy "pegs" when cured.

After cure, sand the pegs flush while scuffing the outside surface of the plexi for tooth, wipe flox into the space below the edge of the plexi, and lay up two plies of 9oz or similar to form the outside flange. In my case, that was just West and plain weave. Blend it to desired surface contour with micro, and some high-build blocking at paint time.

Love your frame!
 
Well, I remember that you'd described that process. Thanks for going over it again with more detail. By the way, I think that Loctite now owns Hysol, so it might be the same product.

This is going to be a little different. I will follow 3M's instructions on preparing the acrylic. There won't be any holes at all in the canopy.

The canopy will bond to the flange and the flange to the fairing in one pass. When cured, I'll tape and lay up the inside flange, remove it, trim it, and bond it to the inside of the canopy and the fairing, again with the 2216.

That's the plan, anyway.

Dave
 
We Got Us a Canopy

Well, for better or worse, this plane has a canopy. After a few lost work sessions deciding if I could form the inner flange before gluing the outer one, and deciding the day I was ready to try, that I couldn?t - I glued the outer flange to the canopy.

I?d planned to glue it to the fairing at the same time but realized that was unnecessary. So at this moment it?s taped and clecoed to the fairing. For that matter, there are a few clecoes through both the flange and fairing right into the turtledeck skin. I had no other way to hold things in position.

Here?s the canopy glued with the black electrical tape still on. I removed the black tape shortly after this photo.

Glued%2Band%2BTaped%2BS.jpg


For the glue, I used 3M?s industrial glue 2216 B/A. I hadn?t used it before, but my mentor is gluing his RV together with it, using rivets also. It wasn?t as pleasant to work with as the thickened G/Flex. I made a test batch and found that while it leaves a thick film on a vertical surface, it?s only thick by comparison to something like, say, water. It doesn?t run but it does seem to creep, before it cures, of course.

The three thickeners I had on hand for use were:

Micro balloons - these do a nice job of thickening epoxy at a significant cost in strength. It is a low-density bulk filler more than anything.

Flox - this is the common structural thickener. It always seems just a hair rough to me, even in small quantities, and I wasn?t sure if perhaps it would leave the epoxy too thick.

Cab-o-sil - According to an experienced Materials and Process engineer I used to work with, in small quantities this thickener doesn?t affect the epoxy properties significantly, but does thicken it. I used a little of this.

Acrylic is one of the materials that 2216 bonds to, and this is one of the main reasons I chose it. I followed the simple process outlined in the tech sheet: wipe with isopropyl alcohol, sand with up to 180 grit (I used wet or dry, wet) and clean with isopropyl alcohol again.

I?d taped the mating surfaces of the fuselage because I knew that it was likely that there would be drips inside and I didn?t want to get them inside the fuselage.

And that?s where I left it: tape off, clecos in, canopy glued down to cure.

Dave
 
Elevator Tips

Yes, the elevator tips.

I needed some small jobs for a bit, things I could work on for just an hour at a time, so I pulled out the elevators and stabilizer and in the middle of other things, for a break, have been working on the tips. This was actually part of the plan all along, to hold off on these until I was working on the composite canopy frame/fairing, because then I could do the first batch of the fiberglass stuff all at the same time.

Today, I bonded the left elevator tip to the elevator. Before getting to this point, though, it need a few things. As delivered, the tip was slightly fat. With the flanges nicely in place, the tip shape protruded .040 or .050 above the elevator surface, all over.

1. Drill and cleco the tip in place so that it fairs with the stabilizer tip.

2. Slit the tip along its centerline with an appropriately-thick cutter.

3. Make 1/2? squares of .040 for shims, each with a hole for the cleco.

4. Test fit them - okay.

5. Fiberglass over the slit, so that instead of two halves I had a tip again.

6. Drill the holes to #30 and dimple the skin and countersink the shims.

7. Glue the shims to the tip, more for handling than anything.

8. Glue and cleco the tips in to the elevator. Since here the glue is a gap filler rather than structure, it pretty much didn?t matter what I used. But I used the thickened G-Flex.

9. Rivet the tips in place.

Right now I?m at step 8 for the left tip, shown, and at step 5 for the right tip.

Elevator%2BTip%2BS.jpg


The stabilizer tips, on the other hand, had the opposite problem. They were too skinny. I followed Wirejock?s (Larry Larson) method and heated the tips to 150 F for an hour, then pressed them on to the stabilizer ends. They cooled slightly fat. I forced them into the stabilizer and clecoed them in place. Now they fit well.

Dave
 
Canopy Inner FLange

Back to the regularly unscheduled progress report.

Also, back to the canopy. In areas, the bottom edge of the canopy was too much of a sharp edge to laminate fiberglass around, so I took a two-fold approach to that. I formed a flox bead there and then after it cured, rounded it. There were places that now protruded too much to assemble the fairing on, so I reshaped those with a more gentle radius, blending it into the outer flange. Yes, I went back and smoothed those edges.

In retrospect, flox was the wrong stuff to use here. It would have been better if I?d used micro, since this was nothing more than a bit of non-structural shaping.

With that out of the way, I taped over the area and prepared the surface to lay up the inner flange. I?m using Aircraft Spruce?s crowfoot cloth, p/n 120-38 for this, because it forms better. Since this cloth is only .004 thick, I?m using six plies. And because it?s warmer now and I?m still in my busy season, I decided to do it in overlapping sections. Here?s the first. The diagonal white stripes are the ends the short overlapping pieces of peel ply.

xdKaXIP.jpg


Dave
 
Nope.

I completed the flange, removed it, peeled off the peel ply, trimmed the edges and did a trial fit. It was too thick. After brooding about this overnight, I removed it and am planning to redo it.

Dave
 
Back
Top