Chpt 5 - Fuselage Sides

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updated: 09/05/2022

 

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Step 1 – Cutting the Jigs and Laminating the Top Longerons

Step 2 – Building the forms for the fuselage sides

Step 3 – Contouring the Sides

Step 4 –Inside Lay-up and installing upper Longerons

Step 5 –Installation of the Lower Triangular Longerons

Step 6 –Completing the Fuselage Sides

27/01/2006 - Step 1 – Cutting the Jigs and Laminating the Top Longerons
To make the Jigs I used 1” MDF board left over from making my workbench, instead of the recommended pine board.  I marked a centre line down the middle of my worktable and covered it with Cling wrap before setting up jigs FJA, FJB and FJC.  I drilled clearance holes through each set of jigs and screwed them down onto my worktable, instead of using nails.  After coating the mating surfaces of the 6 pieces of 0.25”x1”x105” spruce from the Wicks kit with epoxy, I used clamps and wedges to clamp the top longerons (3 per side) into place, tight against the curvature of the jigs.

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The photos below show the Doublers being fitted to the Longerons.  I pre-drilled the doublers, so that they didn’t split when nailing them down onto the Longerons with small panel pins, ensuring that some of the nail is left exposed for easy removal.  Due to discussions in the archives and past newsletters I was a little concerned about the location of the small 5½” doubler and wasn’t sure whether the specified 5” location was correct or not. After spending a couple hours on the Internet checking the archives I eventually found clarification on this issue and proceeded to fit the doubler as per the plans, that is 5” in from the front end of the jig (with the excess extending aft).

Some builders have experienced problems when assembling the sides to the bulkheads - F28 gets placed 6.25" (was 5.9") back from the front of F22 and the doubler location was about 1/2" to 1" short (too far aft) of this point. (See Mailing List FAQ).  Normally the doubler would be trimmed back to allow F28 to be fitted exactly 6.25” from F22 and in the jig setup shown below F22 would normally be located approximately where the front edge of jig FJA starts.  Therefore if the small doubler is 3½” long and is located 5” from F22, you will have plenty of wood available to trim off 1.25”, giving you the required measurement of 6.25”.  I hope I have explained myself clearly and haven’t mudded the water relating to this issue.

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The nails were easily removed using a claw hammer.

Step 2 – Building the forms for the fuselage sides
In this step you use 1 sheet of 1/8” thick x 4f t x 8ft Masonite and 3 sheets of 3/8”x32”x48”-H45 Blue PVC Divinycell foam (Wicks Part No.F500-030) for the fuselage sides.

A word of advice, do not setup the jigs first as mentioned in the plans unless you have 2 workbenches or plenty of space.  It is best to cut and join the Masonite and Blue foam to the correct dimensions first, before setting up the jigs.  I used a 36 inch steel ruler turned on edge to connect the points and ended up with a nice smooth curve for the fuselage sides.  I marked and cut one piece of Masonite first and then used this as template for marking the rest.

I marked the location of the jigs on my workbench using a black felt tipped pen and then used a Hot-Melt glue gun to stick my jigs down on to the table as per the plans.  The glue sets in about 30 seconds and did the job well.  When nailing the Masonite board onto the jigs it is important not to drive the nails all the way home as you will deform the natural curve & slope of the board, especially along Jigs FJC & FJE.  The board can be nailed flat on jigs FJA and FJB.  There is a good drawing on Wayne Hick’s website showing how you should nail the board down.  I used 5-minute epoxy to spot glue the 3/8” blue PVC foam down onto the Masonite and will repair any foam damage on removal later with dry micro.

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The Spacers are cut from 2 sheets of 3/4"x24”x48” - 4.5lb, white Last-A-Foam.  Wicks Part No.F400-045.

I cut the spacers and internal angles by hand using a Utility knife and then lightly filed them to the correct shape & size.  Most builders seem to use a band saw for this step.  The length of the Electrical channel is not specified in the plans and a little web surfing was required to confirm how to cut the channel.  The plans place the channel 14.5” down from the top edge and 1.25” wide.  In the Builders Mailing List FAQ it states that you must not assume that the channel is parallel to the top edge otherwise it will intersect the firewall rudder bracket and it suggests that you match the temporary firewall up with the fuselage sides before gluing in the electrical conduit.  I eventually decided after checking the archives to cut the channel 14.7” down, instead of 14.5” and took the channel back until it was 6”away from the aft edge of the fuselage and made the slope 3.75" long.

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The aft portion of the spacer was cut from one solid piece of foam using a utility knife. All the dimensions were marked with a felt tip pen using the drawings in the plans. The main dimension missing in the plans is the slope of the diagonal bevelled edge.  I chose to make it the same as the top edge (cross section C-C).  To make the bevelled edge cut, I used a hacksaw blade to rough-cut the bevel and then filed it down to the line drawn on the foam.

I made the depressions for the control stick and fuel gauges specified in Step 3 now, before permanently fixing the spacers into place with wet micro. It was easier not having the spacers in the way, whilst I was cutting and sanding the depressions, except I forgot not to bevel the top edges of the depressions for the fuel gauges and when I placed the spacers back onto the fuselage sides, the bevelled edge disappeared under the white foam, as can be seen in the first photo below.  I filled the gap under the white foam spacer with dry micro and sanded the top edge before starting the inside lay-up.  It was difficult to sand the dried micro without damaging or removing the softer white foam, I should have done this repair just before commencing the inside lay-up, whilst it was still wet.

Step 3 – Contouring the Sides
I deviated from the sequence specified in the plans and created the depressions for the control sticks and the fuel gauges above in step 2.  My depressions for the fuel gauges are a bit different, since I am using the Vance Atkinson gauges.  I made the fuel gauge depressions flat as the slanted depressions called for in the plans aren’t needed.  The depression isn't really needed for the Vance Fuel gauges, but it will allow the gauge to sit flush with the sides and will look much better.

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The hole in the bottom of the gauge, which is 0.8”from the bottom, needs to be placed as close to the bottom of the tank as possible in order to get an accurate empty reading.  The Vance instructions state that the bottom of the gauge base should be 9.15" from the top edge, which corresponds with the bottom of the fuel tank as stated in chapter 21, so to allow the correct alignment of the gauge hole during final fitting, I increased the length of the overall size of the depression by 0.5”.  This should give me a little extra movement to play with when installing the gauge.  The 8" diameter control stick depressions are 1/4" deep and were cut using the Dremel with a sanding attachment I made up.  I first removed the foam out to the 6” circle and then hand sanded the sides out to the 8” outside diameter.

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Here are the sides at the end of step 3. All the foam is in place. The depressions are made. The gap between the two sides is uniform. The longerons have been test fitted and should go in place with little effort.  All the foam has been sanded smooth and corners have been rounded (except for the electrical channel).

Step 4 –Inside Lay-up and installing upper Longerons
I marked and cut the UNI cloth required for the 2 lay-ups and with the help of 3 extra helpers, we managed to get the fuselage sides completed and the longerons floxed down, within about 6 hours.  I used the MGS 287 hardener to give me plenty of working time.  I did not have any problems with air pockets around the spacers or in the Control stick & Fuel gauge depressions.

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Before applying the 4 lengths of UNI cloth across the length of the upper longerons, I used a file to radius the inside corner of the longerons and just before starting the lay-up, I used a little flox to fill any gaps under the Doublers and along the sides of the longerons.  I pre-cut 4 lengths of UNI 8” wide by 100” long before starting the lay-up and did both sides together, one at a time, as detailed in the plans.  In the Builders Mailing List FAQ it mentions that it is not necessary to take the UNI cloth past the small 5½” doubler, as this front section is cut away during the installation of the Canard.

Step 5 –Installation of the Lower Triangular Longerons
I used a combination of clamps and nails to get the lower longerons to follow the curve of the fuselage.  I made small 45º V-Blocks for the clamps, so that they wouldn’t slip.

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I made the electrical channels using the method as detailed in the plans, except I changed the height to be 0.7" to match the height of the wooden stringers - LWX & LWY.  I covered both foam cores with a single piece of BID cloth and cut to size after cure.

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I cut both the stringers as per the dimensions given in Fig. 12 out of the supplied Spruce and when I tried to line them up as per Fig. 14 & 16, the angles weren't even close.  I was not happy with the large gaps and eventually decided to recut the 2" wide LWY stringer angle to 45° and to completely remake both the 1" wide LWX stringers.  Unfortunately I could not find any 1" x 0.7" Spruce in Perth and had to use Hoop Pine instead.  Apparently Hoop pine has better strength properties, but is about 15% heavier.  I recut the 1" wide LWX stringers taking the correct dimensions and angles directly from the fuselage sides.  This gave me a far better fit and ensured that the aft cut-out dimensions were still correct at 5.5" x 8.7" (Fig. 16) and the 16.3" position for the LWX (Fig. 14).

After LWX and LWY were floxed into place, I taped the corners with BID and then filled in the area bounded by the lower longerons, LWX and LWY with 3/4" Last-A-Foam.  The position of the electrical channel was doubled checked against the holes in the temporary firewall before final gluing into position.  Clamps were used to hold the foam in place during cure and any high spots were then sanded down level with the stringers.  Any small gaps were filled with micro just before commencing with the 6 ply BID lay-up.

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Step 6 –Completing the Fuselage Sides
The sides were trimmed back to 101.75” as stated in the plans.  With the curvature of the sides I found it very difficult to get an accurate measurement across the length as well as cutting the ends square, in both the vertical and horizontal plan.  I did not need to remove much material and stressed quite a bit about cutting off too much.  I battled a little to remove the fuselage sides from the jigs and the blue foam was damaged in a couple areas.  I think this was mostly from epoxy leaking through the 5-minute epoxy joins, when doing the glass lay-ups and sticking the blue foam onto the Masonite board.  The 5.5" x 8.7" area for the centre spar was removed using the Fein and a hand held hacksaw blade.

Fuselage Weights - Left Side = 4.8Kgs and Right Side = 4.9Kgs

Chapter 5 was completed 27th February 2006.  Total build time = 52hrs.

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