Glider Restoration Part 3 - Fuselage

With the wings complete I moved on to restoring the fuselage of the glider. I'd originally intended to  use the existing fuselage and just straighten it up. Unfortunately, when I came to look at it closer the plywood construction had warped more than I thought. I started trying to disassemble it with a view to re-glueing but it quickly fell apart, at this point it became even more obvious that the original ply was just too warped to be useful. I took the decision to build a new fuselage using as many of the existing parts as possible, but using balsa instead of ply for the majority of the structure. I decided it should be possible to build a structure with equivalent strength this way, with similar or less weight and less tendency to warp if stored for a long time.

[caption id="attachment_168" align="alignnone" width="460"]Twisty Fuselage Twisty Fuselage[/caption]

The first step was to trace out the layout of the fuselage from the plans. This was tricky because the way the plans were folded (in the original packaging) they would not sit flat. They had to be stretched very tightly to avoid introducing curves into the lines. I took account of this when tracing and did a second pass using measurements from the plan and filling in the straight edges.

[caption id="attachment_169" align="alignnone" width="1024"]Tracing the fuselage parts Tracing the fuselage parts[/caption]

Once I was happy with the outlines I traced them onto some balsa. The fuselage sides were cut at the same time by pinning and double sided taping two sheets together, in order to ensure that they matched. The edges were then sanded before detaching the sheets. Because my wings have a slightly longer chord I had to transfer some measurements from the new wings onto the fuselage sides. I then used the markings on the fuselage sides to determine the length of the top sheeting.

[caption id="attachment_171" align="alignnone" width="460"]Taking measurements from the new wings Taking measurements from the new wings[/caption]

I was unable to reuse the original fuselage formers. In the course of removing the glue from them the wood began to crumble, also the thickness of the side sheeting had changed necessitating different dimensions for the formers. I built a servo tray shelf from thick balsa instead of ply to avoid the difficulties of cutting this part out of ply.

[caption id="attachment_172" align="alignnone" width="1024"]Original and new formers Original and new formers[/caption]

[caption id="attachment_173" align="alignnone" width="460"]New front former New front former[/caption]

For the front section of the fuselage I cut some 1/32" ply formers to add back some strength. The were overlapped with the front former but did not go beyond.

[caption id="attachment_176" align="alignnone" width="1024"]Ply doublers Ply doublers[/caption]

I then fitted the new formers using blocks to make sure they were at right angles with the fuselage sides. The rear of the doublers was glued into place at this point, but the remainder was left unglued to make it easy to add curvature to this section later.

[caption id="attachment_178" align="alignnone" width="1024"]Fitting the formers and doublers Fitting the formers and doublers[/caption]

Once the glue was cured the other side of the fuselage was fitted to the formers, again ensuring that everything was held perpendicular. Once this was set I put the fuselage upside down and began fitting the bottom sheeting, making sure that the fuselage sides were vertical at each point.

[caption id="attachment_180" align="alignnone" width="1024"]Adding the bottom sheeting Adding the bottom sheeting[/caption]

With the majority of the fuselage bottom sheeting installed I had to fit pushrods before closing this area up. A sharpened aluminium tube worked well to drill out the angle pushrod exit holes in the fuselage. The pushrod outer tubing was roughed up and epoxied into place at the rear of the fuselage and held in place with rubber tubing at the front.

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The bottom sheeting in the nose section is thicker than in other areas and is sanded to provide a curved shape. I first traced out the shape I wanted and pinned and glued the fuselage sides into position using this template. I also glued the rest of the doublers down at this point to help maintain the curvature. Once the glue was cured I trimmed the bottom sheeting to shape.

[caption id="attachment_186" align="alignnone" width="1024"]Nose bottom sheeting Nose bottom sheeting[/caption]

To create a servo tray in the nose section of the fuselage I transferred the dimensions of the rear part of the tray (attached to the former) to a square stick of wood. I then used a servo and a piece of 3/16 sheet that would become the front of the tray to mark out the required dimensions. I used the stick to mark the inside of the fuselage sides with the tray position, then used pins to transfer these marks to the outside. Cutting a slot between the marks gave me a firm mounting for the front of the servo tray. This was glued in after the servos were screwed into it to maintain good alignment with the rear of the tray. The ends of this piece were then trimmed and sanded flush with the fuselage sides.

[gallery ids="190,191,192"]

To create the nose of the glider I first installed a ply former between the fronts of the fuselage sides. I the attached a stack of 3/16" balsa forming the rough shape of the glider's nose. These were hacked roughly to shape with a razor saw before being sanded to a smooth shape that I was happy with.

[gallery columns="4" ids="194,195,197,199"]

The wing saddle area felt a little flimsy so it was reinforced with two sections of 1/4" square section balsa on either side. These should help transfer loads across this section of the model and provide a sturdier support for the wing.

[caption id="attachment_193" align="alignnone" width="1024"]Reinforcing the wing saddle Reinforcing the wing saddle[/caption]

As with the nose, I built up a block of balsa at the very rear of the glider and sanded it to shape. This gives a neat finish to the tail as well as hopefully absorbing any impacts during transport and handling.

[caption id="attachment_196" align="alignnone" width="1024"]Tail block Tail block[/caption]

The fin was fitted last to avoid bashing it while working on other parts of the model. I was glued into a slot in the top sheeting, and held in place with blocks while the glue cured. I used the original fin as this part was still intact and straight.

[caption id="attachment_200" align="alignnone" width="1024"]Fin installation Fin installation[/caption]

Covering the fuselage was a straightforward process as there are no open sections to cover over.

[caption id="attachment_201" align="alignnone" width="1024"]Covering Covering[/caption]

With the majority of the fuselage built I fitted the original rudder and stabiliser to the model. The rudder was fitted with 3M Blenderm tape which makes an excellent hinge. The stabiliser and wings are intended to be held on with thick rubber bands, I need to go out and buy some stronger bands before flying the model. After centering the servos I trimmed the pushrods to length and fitted clevises, then tested the amount of force required to move the control surfaces. The rudder required quite a bit of force so I moved the control horn lower down on the rudder to better suit the angle of the pushrod.

Unfortunately I don't have access to a decent slope or any good means of launching the model as a pure glider. The HiFly comes with a motor pod that sits above the wing so it can be flown as a powered glider. I've assembled the pod, but I'm waiting on the arrival of a motor before I can fly it.

At this point I was able to fully assemble the model, which took up a lot more space than I remember. Various parts like the canopy and the stabiliser were reused from the original model. Once the motor arrives (hopefully next week) I'll be able to give it a test flight assuming the weather cooperates.

[caption id="attachment_203" align="alignnone" width="1024"]Assembled model, sans motor Assembled model, sans motor[/caption]