Constructing the Cabin

[190 hrs]

Cabin Structure: 23, 28 & 30 September

 

With the bench cleared of the fuselage, construction has commenced on the cabin with the assembly of the cabin bottom. Line up all the parts, secure the frames to the bench using clecos so its perfectly aligned and flat, the start drilling all the holes.
TIP: Set out one of the spacers for the rivets top and bottom 32mm apart, clamp them together and use it as a template, this way all spacers are the same just in case you mix them up.

With so many solid rivets holding each of the three sections together that makes up the cabin bottom, is it any wonder that the BushCaddy is one of the most solid kit aircraft available on the market.
TIP: Debur all parts and prime before once again securing the frames to the workbench with the clecos so the cabin bottom remains square and the underside is flat. This will make it easier later on when aligning the cabin to the fuselage.

 

Thought I would lift the fuselage minus the horizontal stabilizers back up onto the workbench and butt it against the cabin bottom just to see what it looks like.

Starting to look like an aircraft.
Plenty of room for two people to sit side-by-side in comfort.
Read all the drawings for the construction of the cabin before strating to cut the individual angel iron length. The drawings show where specific sections need to be adjusted and fitted when in position. Use clecos to hold the sections in place before drilling any holes.
TIP: Mark the pattern on the workbench and individually fit each piece making adjustments as you go. Remember the old saying, mark twice and cut once otherwise you may find yourself wasting material.

Duplicate the pattern by extending the base line. Clamp the vertical end frames and transfer the measurements so the two frames are identical.

October: 13, 15, 19, 20, 21, 22, 26, 27, 28 & 29

Now that all the frames are identical, the templates can be marked and drilled ready to be riveted to the frame. Each hole in the frame will need to have a counter sink hole drilled to take the rivet head. While the spray paint dries, work on the identical section on the other frame.
TIP: Start at the front of the cabin and work toward the back, however do not drill any holes until the frame is clamped back onto the bench and aligned with the template. It might take a little longer doing it this way, but at least the frame remains square and the correct shape.

When you place the cabin frames on the base frame and slide the fuselage back onto the workbench you start to get a feel for the length of the aircraft as well as the amount of room there will be inside the cabin itself.
TIP: Use plenty of clamps to hold the cabin frames to the cabin base as well as support angle lengths to keep the correct width of the cabin before cutting, drilling and riveting each of the sections.

The construction and solid riveting of the cabin will take a considerable length of time but don't rush into riveting without cutting, drilling and fitting all the sections first and holding them into position with clecos. You might notice the square on the left side of the cabin, this is to make sure the frame is square and centre of the workbench.
TIP: At various times hold up the firewall and engine mounting bracked to make sure all the measurements are correct because once the frame is completly riveted it will take a lot of effort and waste materials fixing up a mistake.

With the cabin frame bolted to the cabin bottom and the cabin bottom secured to the workbench so nothing moves, remove the clecos one by one replacing them with solid rivets as specified in the drawings.

As you rivet the gussets into place you can feel the cabin frame becoming stronger with each rivet. Climbing in an out of the cabin to get the best angle to hold the riveting gun and bucking bar is easy as there is so much room and at this stage all riveting can be performed by one person.

The main support struts have now been secured to the cabin and the front frame, also the twin throttle support bracket has been fitted and secured into position. As I am installing a Jabiru 3300 engine, I kept the cabin frame clamped to the workbench while holding the firewall to the structure. This means the bottom surface remained flat to the workbench. Mark where the angle supports line up against the rear surface of the firewall. Set out the holes for the firewall and drill but when it comes time to drill the holes in the frame, start from the centre and work outward to the edge so the metal firewall does not buckle.
TIP: By now you would have determined which engine will be installed and you may need to make some modifications to the firewall position, throttle control arm and other fittings so everything fits.

TIP: With the holes drilled in the firewall, start drilling the holes in the cabin frame starting in the centre and working out in a spiral direction inserting clecos at regular intervals. This will ensure the metal firewall pan remains stiff against the frame and doesn't buckle. I have also braced the bottom bracket to the workbench to stop it moving out of place.

Although Robyn has not been up flying in an ultralight prefering those big birds that have flight attendants serving food and drinks during flight, she was surprised at the size of the cabin and how much leg room there is compared to my last ultralight where your legs were straight out in front. Now all I will have to do is convince her that I sit in the left side as pilot and the passanger sits in the right hand side. Maybe I can talk Robyn Into taking flying lessons ...............

Although the floor pan is shaped to match the two dimensions it may not neatly fit where the pan folds from the horizontal to the vertical.
1. Mark and drill the holes in the pan that fits onto the firewall first and secure with clecos
2. To shape the rear of the pan and have it fitting tight against the base, use a series of clamps to form the pan againsts the cabin base gradually working up until it can be clamped against the cabin. This will ensure a neat fit

TIP: My home made dimpling machine, very simple to construct and easy to operate. All you need is two pieces of wood about 1m long each, a hinge and a dimple set.
1. make a handle for the top piece of timber
2. screw the hinge between the two pieces of timber
3. drill two holes in the timber so the dimple set align
4. use a rubber mallet to stamp the dimple in the aluminium sheet

Two views of the cabin construction while working on the frame on the floor. At this stage the firewall and the panels that form the shape for the wings and the top are held into position with clecos.
TIP: At this stage you will need to start working out what engine you are going to install as the top and side skins vary depending on the HP rating of the engine.

Work has commenced on fitting the side panels and floor pan to the cabin frame. Cut and fit the centre panel first drilling holes along the centre line and fitting the clecos and working your way up toward the edge. Mark and cut out the notch for the bracket extending below the cabin and secure the panels with clecos, this way it will keep the metal tight against the ribs and the support brackets.
TIP: The floor pan goes under the front and side panels and also has a 40mm overlap at the back of the cabin so the fuselage can be attached.

November: 2, 3, 4, 9, 10, 13, 15, 16, 17 & 18

All the riveting of the cabin bottom has now been completed and the brackets holding the under carriage have been drilled and fitted into position before turning the cabin frame back over and putting it back on the workbench so the pedals can be fitted to the floor pan.

The cabin is taking shape with the pedals have been bolted to the floor and the hydraulic break arms slid into position with a brace onto the angle supporting the firewall.
There is a further modification to the side frames with another 3/4" x 3/4 x 1/8" angle riveted to the existing angle to form a T section. In addition, spacers have been bolted between the gaps in the vertical frame to support the more powerful 120HP 6 cylinder Jabiru 3300 engine. A decision on which engine to install will be made over the next month or so, stay tuned for an update on what powerplant will be installed.
TIP: Make sure the firewall is the very last skin to be riveted into position or you will run out of space to work on the controls

The break pedals move within the nilon blocks that are bolted to the floor. Adjust the nuts so that they move freely and that the break pedal that will connect to the hydraulic cylinder slides all the way into the sleve and moves freely.
TIP: You may need to file and/or drill out the main break support if the weld has penetrated the tube but keep working on it until the break pedal moves freely.

I have marked out where all the instruments, gauges, control, switches and fuses etc. are going to be placed on the dashboard working on the centre line of both pedals and will drill the holes after all the skins have been cut, fitted and held with clecos. The length of timber at the rear of the cabin and the rope is being used to back put tension on the two springs used to stabilise the pedal control cables that will be connected once the fuselage is attached to the cabin.
TIP: Don't do any riveting on the dash or any of the skins until all the skins have been cut, fitted and held in position with clecos.

Attach the side skins to the cabin frame starting from the top corner and work toward the front and down toward the workbench to make sure the skins are kept tight. The bottom holes will have to be drilled from the inside out as these have already been drilled to hold the pan into position.
TIP: This is where the extra clecos come in handy as there are many holes to drill and skins to fit before riveting into their final position.

With all the panels removed from the cabin its time to lift the structure off the workbench and back on to the floor so the cabin roof can be cut and fitted into position. While all the panels are removed it is also a good time to blow all the shavings and bits of aluminum out of the corners and trapped between the loose skins and the frame. The structure is so light one person can move it without difficulty.
TIP: Mark all the drill holes on the workbench before starting to drill the holes from the centre out so the skin is stretched tight across the frame..

Starting to look like an aeroplane with instruments, gauges, switches and fuses being mounted into the dashboard before it is fixed into position, much easire to cut the holes and fit the instruments on the workbend rather than doing it later from inside the cabin. I still have the slip/skid and vertical speed indicator to mount, however the holes are drilled ready for when they arive.

If you carfully plan the riveting sequence you will be able to do all but the top row of solid rivets forward of the dashboard.
SEQUENCE: Installation of the pedals and brace to the firewall, tension springs (place a wood block behind the pedals to keep the pedals vertical), hyrdaulic break cylinders and mounting bracket to the floor pan, dual throttle control arm, start riveting the side panels, bolt into position the dashboard, fit the top panel and leave loose while bolting into position the support bars from the firewall frame to the top of the cabin then finally the firewall. Once this is complete, finish riveting. You will only need another person to finish the last of the solid rivets forward to the dashboard. Replace any solid rivets that smile back at you.

Van Aircraft supply NACA eye-ball valve/director kits for left and right side of the cabin. Use the template to mark the section that is to be cut out of the skin forward of the doors as well as the rivet holes to secure it to the skin. To add strength, cut a template of 0.025" to the same shape as the vent so the rivets secure into metal and not the plastic.
TIP: The plans show the dimensions for drilling the holes and mounting the guide blocks for the aileron push rods to enter the cabin. I would recommed that before marking you decide at this point which push rod will go on top of the control arm and which one will go underneath, mark and drill the holes accordingly. This way, minimum pressure will be put on the push rods and the drag will be minimised otherwise you might fine the side-to-side movement of the joy stick a little stiff.

With plenty of room on the dashboard to mount the eye-ball valve/director, I have mounted both units in line with the dual throttle control to keep balance with the other instruments and controls and this will ensure they are in easy reach and will direct fresh air onto the face. I could have mounted them under the dash panel but I wanted to keep obstructions away from the legs.

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