Overview
Fitting the Canopy
Preparing for External Skin
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Berkut Style Canopy
The Berkut is the next generation of the Long-EZ design.
One of it's most distinctive features is the F-4 style split canopy. I bought my tinted canopy from Todd's Canopies. I will lay this out using my Berkut drawings as a guide.
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Unlike the Berkut builders, I have to make my canopy frame myself. Nothing prefabricated here. Even the canopy hinges will have to be fabricated from scratch.
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Cutting the Canopy Bubble
This is a place where you really want to take some time. After fitting the canopy on temporary crossmembers, I fixed a piece of foam at the desired angle between the firewall and the rear of the canopy. Using another piece of foam as a guide, I traced a cut line onto the lexan and cut it with the Fein Multimaster.
The firewall side needs to be cut first to insure proper alighment.
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I traced the cut line for the aft side of the front canopy. This one was pretty straight forward. I used a strip of formica as a guide. Using that as a guide, I made several reference points along that line.
I found the center point (top of the canopy) and drew reference points every five inches. I angled the line so it angles forward by clamping my formica strip to the canopy and held the centerpoint in place with tape. I then measured at my reference points to insure continuity on both sides.
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With the two sections set in place, I went about aligning the canopy halves. I used a strip of foam held with brads to align the sections and then checked the flow of both the top line and the sides.
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Once I was happy with the layout, I blocked out the rear turtleback with scraps of wing foam. After tracing the rear canopy outline, I clamped it to the firewall. Using a hotwire, saw and sanding block, I shaped the foam to what I anticipate being the finished shape.
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Forward Canopy Deck
I cut a piece of 1.5 inch thick Divinycell foam 3 inches tall and the width of the cockpit at FS43. I notched it to accept the front of the canopy bubble. I cut a trough using a 1/2 inch router bit to accept several 1" x 1/2" strips of Divinycell foam to make up the deck.
I took a scap of wing foam about an inch thick and clamped it to the rear side of FS28 and then trimmed and sanded it to match the profile of the bukhead.
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I did the port side tonight to try out the methd and I think it will work out fine. I microed the foward edge of the strips to the foam clamped to fs28. I held it in place with a bungee strap.
The block at FS43 is notched on the backside to accept addittional strips to continue the deck.
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Completed Front Deck
The front deck is completed deck is hardshelled and ready for a skin.
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Tie the front deck to side rails
The area aft of FS 43 is fabricated the same way. Once this has cured and hardshelled, the suface will be profiled to eliminate the block at FS 43.
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Mid-Canopy and Rollover
I glued eight sections of foam 20" x 24" x 2" together to form a block. The aft face was hotwired to an angle matching the forward face of the rear canopy. Once the rear face is matched to the canopy, the block is cut to the proper length.
I slipped in a large piece of paper to use as a template and traced the profile of the canopy on the paper. I pulled it out and folded it down the centerline. The side profiles were slightly off from each other so I split the difference and transferred the templated to a piece of formica. I cut that out and repeated the process for the other side. Using the these as hotwire templates.
Once the profile was cut to shape I added strips of .5" x 1.0" inset at 1/8th of an inch. This will provide a ledge for the canopy to bond to.
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Setting the bonding faces
The mating surface needs some additional attention where the front edge of the rear canopy meets the mid-canopy turtleback. The 1" x .5" strip that makes up the profile I am bonding to is perpendicular to the angle of the profile of the leading edge of the rear canopy which will not work. I need to trim it down to the point where it will run in parallel to the surface of the turtle back. I used a router set to a depth of 1/8th inch to accomplish this.
Any gouges can be repaired by screeding a final profile using a template and micro.
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Canopy Mating Lip
The form is moving along quite well. I decided to create a mold from the shape and reduce the weight of the canopy in the process.
Here is the lip I am fabricating, The canopy will be bonded to that.
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Mating the canopy to the fabricated lip
This is a trial fit of the canopy to the fabricated shape. A mold will be created from the shape and the final piece will be made up of carbon fiber to stiffen the frame. Because the frame is molded, the necessity of filler will be minimized.
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Flexibility of Canopy Frame Line
By using bondo to faricate the lip that will mate to the canopy, I can obtain a perfect fit.
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Molding the foredeck and side rails
Here I have the foredeck in the vacuum bag. After several coats of mold release I applied several layers of glass to create the mold. Once the mold is free of the plug (after about 24 hours) is is placed back on the plug to continue to cure for several more days.
The layups of carbon fiber are applied in much the same manner as the plans call out. The exception is that I substitute 2 plies of CF 716 UNI for each instance where BID is called for.
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Trial Fit
The three molded components are placed together along with the canopy bubble for a trial fit of the assembly. There is still much more to do here but it is starting to come together.
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