Chuck and Ryan's Build Tips

[ceslaw]

I have been posting construction tips over at Supercub.org, but since it is about a Carbon Cub, this seems like a better place to post. So I will be posting future tips and thoughts on this site.

Floor board

When the floorboard is finally set in place one feels like some real progress is being made. But before setting that floorboard in place here some tips.

There are some 40 holes pre drilled and tapped in the frame for screws to secure the floor board. But odds are the threads are a bit rusty or have a bit of powder coat on them which will make screwing problematic. So get out a tap and run it through the holes before the floor board is set in place.

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We used the Boelube with the tap. Good stuff. A piece of tape on the tap let us know when we had gone in far enough. After each hole was tapped it was marked with a silver Sharpee so we could keep track of what we were doing.

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The screws went in easily thanks to this little extra step.

We also sprayed a bit of Corrosion X into each of the threaded holes. This is pretty neat stuff we picked up at EAA Air Adventure a couple of years ago. It is a rust preventer that comes out like a foamy oil but clings to the steel. It works well on raw steel surfaces, like a drill press table.

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The manual describes pre-installing the pedals before the floorboard is set in place. The pedals have screws that go directly into the frame (two on each front, one on each rear), so preinstalling them could create an issue with aligning them once the floor is in place. We simply installed the floor board and then set the pedals in place. Initially all the screws are just put in with a couple of turns and then once they are all set in place tightened. (We used a battery drill with the torque preset to assure uniform tension). Finally the pedal screws that go through the floor board with backing washers and nuts were added. There were no alignment problems using this approach.

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[c130jake]

Great idea.

[ceslaw]

Tail Feathers

The manual indicates the tail feathers should be assembled after covering. We decided to assemble and rig them before so we could make sure everything would come together easily after it was covered. It won’t take much time to dissemble them for covering and all the hardware will go into a marked zip lock back so it will be easily found when the time comes.The cable that pulls the “up” elevator is more difficult to access once the fabric is on, so it was adjusted per the manual now. Two things must be done to adjust it per the Finish manual.

First, the elevator must be set so it is on the same level as the stabilizer. (I could say they need to “be on the same plane” but that would have a double meaning.) Power up the trim motor to move it into this centered position.

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Second, the seat has to be set in place in the most forward position. Then the top “up” cable can be adjusted so when the stick is pulled back to the maximum up elevator position it just kisses the seat. Lock the connection at the top elevator and it is now set.

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Third, get in the plane, move the stick back and forth, operate the rudder pedals, and make airplane sounds. Then take it all apart putting the pieces in a plastic baggy marked appropriately. It will be so much quicker finding the hardware when installed for the final time.

[Pete D]

These holes are flow drilled and roll tapped. It would be best to use a roll tap, not a standard cutting tap to chase these holes.

[ceslaw]

These holes are flow drilled and roll tapped. It would be best to use a roll tap, not a standard cutting tap to chase these holes.

Thanks Pete. It is good to know the pros are keeping an eye on us builders. Good point!

I should have noted in my post:

1. Just the tip of the tap was used to clean out the top threads and the tap was never "forced".

2. The green tape visible in the pictures was a marker to make sure the tap only went in a short distance.

3. The screws were still snug, but easier to start once the first few threads were chased.

But your point is well taken. Thanks.

[ceslaw]

Cup Holder Update

Last November I posted that my order for a Carbon Cub EX was placed just days after Cubcrafters revealed that the 2014 model would include a cup holder; clearly a factor in making such a big purchase decision. In June I posted what are believed the first public photos of the elusive cup holder. And now I can reveal yet another cup holder update.

While at Oshkosh Cubccrafters was touting their official beverage container. It is an impressive vessel which has a full frontal view of a Cub and is made in the USA. This is a necessity for any serious Cub pilot, so I brought one home. Upon returning home I was able to confirm that it fits perfectly in the carbon fiber kick panel cup holder. Kudos to the CC engineering department for yet another fine addition to their product line.

[ceslaw]

Extended Baggage.

So how much work is there in fastening several aluminum panels together? Actually quite a bit.

1. Make sure that the stringer below the access door on the right is NOT installed until after the extended baggage is in place.

2. The manual shows continuous beads of methocrylate along many of the joints between the frame and the aluminum panels. Although we started out that way, we switched to stitching with three or four inch beads. I am sure it is sufficient and it conserves the glue. Plus the gaps between the glue provide space for plastic ties to secure the fuel line later.

3. Stitched beads of methocrylate are needed along the top airframe joints, all angle airframe joints, and the bottom below the floor along the cross support tubes: anywhere the aluminum meets the airframe.

4. Here is an idea. We added two tie downs at the midpoint on the floor. The same tie downs and hardware were used as on the top aft panel, but the tube clamp is a 5/8” size, part number MS27405-5 rather than the ½” used at the top aft panel. I did this for two reasons. First another mechanical connection between the aluminum panels and the frame seemed like a good idea. Second, the tie downs can be used to secure a net to prevent cargo from shifting forward.

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5. Another set of tie downs was added at the rear seat belt connections, per Mitch’s suggestion. The welded nut plate for the seat belt bolt is the same size as the tie down bolt. Spacers and washers will make this work just fine.

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[ceslaw]

Stede:

Very nice tie downs!

Tie downs at the aft end floor are a good idea.

[ceslaw]

Garmin G3X preparation

We decided to go with the Garmin G3X after checking it out at Oshkosh this summer. It has an abundance of features which are unnecessary for typical VFR flight but it is intuitive and packs so much information into such a small space. Before covering the plane there are three items that need to be installed.

1. Trim indicator. This provides a display on the G3X showing the relative position of the stabilizer trim. Once the indicator was installed the wires that run along the left stringer could finally be tied down. We used wire ties about every eight inches, wrapping the wire with friction tape at each mounting point.

A couple of notches were filed on the bottom bracket so a screw driver could be used to fasten the sensor to the vertical bracket.

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2. Pitot tube. The AOA requires a two tube rather than single tube pitot. The bracket was mounted roughly centered between the inboard rib and the inboard edge of the landing light opening (which pretty much nailed the specs in the new drawings, which we did not have at the time). The bottom of the bracket must be even with the bottom of the ribs, not the spar. Masking tape between the ribs provided a good reference point for the bottom of the bracket.

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The pitot tubes were routed and then brought through the butt rib at the opening by the drag wire after a grommet was placed in the opening. Protective anti chafe wrap was used on the tubes. Silicone was applied in a couple of locations to make sure the tubes stayed put.

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3. Magnetometer. First a couple of holes need to be drilled in the spar to mount the bracket. Very precise dimensions are specified to assure it will be level to compensate for the dihedral. (Future kits will have these holes pre drilled at the factory). The truth is the holes are slightly over sized so the bracket can be leveled even if the holes are a few thousandths off. Second the bracket needs to be assembled. We placed the three rivets on the leading edge and the top ring, but not on the sides. Once it is installed after the plane is covered the longitudinal axis can be checked to confirm it will be level in flight and then the four side rivets can be placed. Finally the cable needs to be run and secured with silicone.

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Although the holes in the spar need to be drilled before covering, the magnetometer and the bracket are not permanently installed until the plane is covered. The risk of damaging it while covering is too great. The bracket and magnetometer need to be installed in the covered plane together, so there is no point in leaving the bracket in place while the plane is being covered.

The wings and fuselage are now ready to be covered.

[ceslaw]

Boot Cowl

1. Before any rivets are placed on the fire wall, we used the fire wall as a pattern to cut out the black vinyl and fiberglass insulation. We used the fire wall as a pattern to cut out each of the holes with a #11 Exacto knife.

Per Mitch, the holes in the vinyl and insulation that carry the engine mount bolts need to be enlarged to assure the metal fire wall will directly contact the frame.

Once all the holes are neatly cut, we glued the vinyl to the fiberglass with 3M spray adhesive. Then we set it aside. The fire wall was also used as a pattern to mark an outline on a 4 x 4 section of birch veneer plywood.

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2. We measured 1 ¼ to 1 ½ inches inside the outline of the fire wall on the board so there would be enough space to clear the out squeeze riveter and then we cut it out. Even cutting it back that distance proved insufficient and we ended up grinding a bit off the rivet squeezer.

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3. When placing the fire wall / plywood on the fuselage we discovered that the top of the heater vent on the floor board was interfering. It was trimmed back even with the fire wall. Four hardware store 5/16” bolts were used to hold it in place, ready to add the side panels.

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4. The temporary instrument panel was installed with those frustrating Adel clamps per the award winning Mitch Travis video. We discovered that the lateral position of the panel is important and can make a difference in the way the support tubes center in the openings. The holes for mounting the panel were elongated so that we could precisely locate it evenly left to right, marking a reference point and then measuring on both sides. A tiny lateral variation in the location of the panel can make a difference in the alignment of the two support tubes in the cowl openings.

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5. Use lots of clips. We placed a clip between every rivet hole. Start the clips at the bottom so that the angle at the bottom of the cowl is exactly even with where the tunnel will be. Odds are by the time you get done working your way to the top with those clips the top center seam will come together nicely. Likewise when placing the spacer strips, start at the bottom at the angle. This will result in a better fit at the bottom.

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6. The gascolator cover went together just fine until we went to place the six Tinnerman nuts. None fit. On Mitch’s award winning video the Tinnerman nuts referenced were part number A1785-6Z-1D. Those are also shown in the pictures in the manual, although the manual references part number A1784-6Z-1 which is what came with the kit. So we called Wick’s and spent three bucks for the longer A1785-6Z-1D nuts, which worked just fine. Alternatively one could notch out the panel a bit so the supplied nuts would fit. I admit it. I’m lazy.

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