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Foam Fairings, Part 3

Fitting a full lightweight fairing to a pedal machine

by John Tetz

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In Part 2 of this series I looked at how you can form the foam shell around the mould. This week, I install it on the trike.

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Set the shell on the floor. Take the wheels (including the rear) off the trike and place the trike in the shell from above, sliding it forward. This shows the inside of the front part of the shell with the Y-mounts holding this section up and out. The pads which spread the load out are made from scraps of Zotefoam. The tubes are carbon.

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Here is the rear support off the back of the seat. A C-clamp is used until everything is mounted, aligned, and checked out. Then the rod will be bolted to the aluminium bracket. This is a damn complicated mount! It has to be adjustable forward/back and up/down, and accommodate the two angles of the side of the shell, one for the foil shape and the other for the sectional view shape. And ideally it should be easy and quick to couple the shell to the vehicle. For this, I plug the rod part of the mount into an aluminium tube mounted on the seat back. The bracket is wood screwed to a block of wood. The wood provides a decent amount of area to be contact cemented to the shell. No doubt there are other ways to do this.

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This shows the brackets. The slots are up/down adjustments.

The Y-support and seat mount are all you need for now. I blocked the wheel-less trike up under the cross tube to prevent the trike from rotating, then climbed in to check for toe/heel clearance. Some adjustment of the Y-mount and seat mount may be necessary. The Y-mount adjusts the shell nose height. The seat mount adjusts the shell rear end height and left/right positioning, as well as the nose left/right positioning.

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Once the up/down, forward/back, and centre positions have been thoroughly checked out, a frame mount can be made which will permanently fix the forward/back position. I use a strip of Velcro along the bottom of the frame to support the bottom foam.

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Once this is installed, the wheel holes can be trimmed and the wheels reinstalled. Turn the wheels and make small cuts. The wheel openings will not be round but have some amount of rectangular shape. Seeing the trike on its wheels in the shell for the first time was quite a moment. This represented ten months of work, from the time I started building the trike to its installation in a partially finished shell.

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Next, cut the butterfly-shape openings on the grey bottom so the wheels will clear when turning corners. I cut only a minimum amount until the vehicle is on the road, then trim to get the turning radius needed.

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Make the spray shields. These make wonderful bulkheads which stiffen the shell, replacing some of the stiffness lost from those large wheel openings.Note the carbon rod (arrowed) plugged into a small tube brazed on the head tube leading to the spray shield. This is needed to reduce left/right shifting of the shell.


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Heat-form the sides of the tail and trim the S-curve and bottom green/grey line, using the trim system on the mould. Leave about 1 inch along the top edge.

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The final trimming will be done on the vehicle. I carved a wheel fairing from mould foam to aid in hand-shaping the Zotefoam

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Here is the left side, with the grey bottom colour and a black HD 80 wheel fairing. The grey and black pieces were heat-formed separately with a hot air gun and held in place with gloved hands until cooled, then trimmed and glued to the main tail side. Heat-forming the tight compound curves at the leading edge of the black wheel fairing has to be done in a few steps to get the proper shapes. Leave enough material on the leading edge to join with the right side after the two halves are on the vehicle. They will be glued together.

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I used a lap joint between the grey and the black because of the differences in thickness and because the HD 80 doesn’t glue very well; the lap joint helps prevent detachment.

Plug in the small U-stiffeners into the bigger U-stiffeners on the shell. I use about 3 inches. The plug-in sections for the upper ones are shorter, so that when installing the tail, the lower ones are inserted first, then the upper ones. The bottom of the smaller U-stiffener has to be trimmed off to fit into the bigger U-stiffener, but make sure to put a new bottom inside this short plug-in section. Then masking tape each side of the tail to the shell, using the green/grey line as an alignment guide.

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Next, mark the location of the smaller U-stiffeners and glue in. The stiffener straddling the green/grey colour line extends to the end of the tail. I shortened the upper U-stiffeners on the tail because long ones would interfere with the panniers. These could be around 10 incheslong.

Time to make the tongue & groove alignment joints between the U-stiffeners. Refer to the end of the last week’s article for a detailed description if needed. The tail has the groove, while the shell has the tongue. This system does a wonderful job of stabilizing the edges.

When the U-stiffeners and the tongue & groove braces are installed, and the tail is securely taped to the shell (or the over-centre clips are installed), the rest of the tongue & groove braces for the shell/tail joint can be completed.

This is the time to trim the top edge to fit the line of the shell. Then the top edge tongue & groove braces along the 27.5 inch line can be constructed.

The shell has the grooves and the turtledeck has the tongues. This system guides the turtledeck onto the shell/tail and provides edge stiffness. The braces extend from the end of the canopy to the end of the tail, with a groove break at the shell/tail joint, but continuous for the tongue on the turtledeck side.

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I made six small aluminium over-centre clips to hold the tail to the shell: one for each of the four U-stiffeners, and one for each of the shell/tail tongue & groove joints. Also, two to hold the turtledeck in place, one for the front edge of the canopy, and one for the canopy to door.

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Here are three clips per side holding the tail in place.

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Here are the two halves of the tail joined by an end.

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This shows the luggage rack end support, which will be glued to the tail and bolted to the luggage rack. Do not glue this in until after the vehicle has been tested and checked out on the road, as you might have to adjust the shell height. Here is an upside down view of the construction of that support:


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I waited to cut the door until I knew where my shoe must go when entering and exiting the shell. The leading edge of the door does not have to be even with the canopy. The smaller the door, the lighter the door and the stiffer the shell. Carefully lay out the lines for the door opening, and with a razor blade cut nice straight lines, as these are the lines you will see on the shell. Then start constructing the latch system.

This shows the inside of the door with a backing for the latch system, which is made from 0.2 inch HD 80 and glued to the door. Note there are spaces on the right and left edges of the green door. These will contact an overlap on the shell to limit the door in its closed position. Leave enough space along the top edge because this is the groove into which the canopy will drop. Lay a cover piece on top to complete the groove. Below the door in the photo are two sliders also made from HD 80. They have finger tabs that are used to move the sliders.

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This photo below shows the sliders attached and in the open position (slide inwards).

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This shows the slider in the closed position, which will overlap the shell edge stiffener.

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I used a cloth hinge. Cut the cloth to the proper width to be glued to the bottom edge of the door (thickness of door) and to the edge of the shell, including about 0.25 inch of the U-stiffener to increase the gluing area. Make a longitudinal crease at the thickness of the door by folding the cloth and squeezing it in a vice. Use a little heat from the hot air gun when the cloth is in the vice to help make a permanent crease.

Next, apply a light coat of contact cement and let it dry overnight, as the cement takes a long time to dry on cloth. Apply another thin coat of glue, then apply the hinge to the bottom of the door. The closed end of the hinge goes out, the open ends goes in. Glue and lightly apply to the shell to check for alignment and even gaps, then press firmly.


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Heat-form a U-stiffener to fit the inside canopy shape and glue in approximately as shown. Make and glue in the tongue assembly on the left side of the canopy so it lines up with the groove on the door edge. Pre-glue a cloth hinge, but do not glue to the canopy.

Make the lap joint on the leading edge of the canopy and inside the shell. The inside of the shell has a layer of HD 80 placed even with the trailing edge of the shell. To provide a lap for the canopy, glue a second layer extending about 0.5 inches beyond the edge. The canopy has one layer of HD 80 flush with its edge and makes contact with the lap. These stabilize the edges of the shell and canopy. I use one over-centre clip to hold the canopy to the shell and one to hold the canopy to the door.

Glue the hinge to the shell but not to the edge of the canopy. Check the fit of the canopy along the canopy/shell joint with the canopy inserted in the door tongue & groove. A trim cut along the right edge of the canopy may be needed to bring it in flush with the shell. Also, look from the back view for uneven heights of the left side vs right side of the canopy. This cut can also adjust left/right heights. This edge is a slightly curved line, so use the edge as a guide. Glue the canopy, lightly apply it to the shell to check for fit, then press firmly.


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Last is the turtledeck. I basically hand-formed these two pieces. The sides of the yellow area have very little forming. The hardest part is trimming the fit between the turtledeck and the shell. This shows the two sides rough-cut and taped to the shell.

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This pic shows heat-formed scraps of HD 80 holding a green top in place to determine the size of the grey filler piece. The photo below shows the grey filler trimmed and taped in place to check for fit. Note the green triangular piece also being fitted at the tail end. Finally, fabricate the tongue along the entire length of the bottom edge.

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I made a hinge with a removable pin so the turtledeck can be removed. I suggest using a piece of HD 80 in this area as a backup and on the turtle deck as a stiffener. Then glue the hinge to it.

Do a final trim around the cockpit area. I added a strip of grey for accent.

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Here are the door, canopy, and turtledeck closed...

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... and then opened. There is a string to limit opening of the turtledeck. To close the turtledeck, slip the tongue on the right side into the groove, then do the left side. There is one clip per side about halfway down to hold it on. I also use a short piece of Velcro near the most forward end to hold that area down to the shell, and another piece of Velcro between the canopy and turtledeck. This photo shows the door canopy open as you would see getting in.

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To climb in the vehicle, first open the door, hang on to the handlebars for support and stability, then raise your right foot over the door opening and down through the foot opening in the bottom.

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That 22 inch line is about as high as you can comfortably get your feet up and over. Then raise your left foot over the door opening, step into the left foot hole, and lower yourself into the vehicle, using the handlebars for balance.

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