Monday, September 9, 2013

Continuing With More Forward Fuselage Prep

Continuing on with preparing more forward fuselage components for primer, the F-1271-L&R fuselage corner skins were pulled out of the shipping crate and deburred. There was nothing in the plans requiring any preparation for these components … but of course they will be dimpled prior to priming for the flush rivets being used on the project.

While the F-1271 corner skins and F-1272 bottom skin were out of the box, decided it would be a good idea to do a trial fit of them onto the F-1276 bottom skin to identify areas of overlap. Once the pieces were mated, a soldering iron was used to melt the blue film so it could be pealed away from the overlapping areas for primer.
                                     Dragging the soldering iron along the overlapping edges of the F-1271,
                                     F-1272 and F-1276 skins for easy removal of the blue film for primer.

Yesterday, the decision was made to leave the stainless steel firewall components alone until later … today was later. Further in the build, after the F-1217A-R tunnel rib has been riveted onto the F-1201C firewall, the plans have the builder enlarge a hole in the F-1201C firewall to 9/16”. I remember reading builders have had issues with the step drill (unibit) drifting away from center … the drift is caused by the edge of the flange of the F-1217A-R tunnel rib not completely covering the hole which tends to push the step drill away from center. My solution and suggestion to other RV-12 builders is to take an extra 15 minutes now and make a perfectly centered hole by first drilling the F-1201C firewall hole to 9/16”, then Cleco the F-1217A-R tunnel rib onto the F-1201C firewall so the portion of the flange that requires removal can be marked, then removed. Once marked, a Dremel outfitted with a cutting bit was used to hog the excess material, followed by a fine smoothing with a sanding drum. The result … perfection! OK it took at least an extra 15 minutes … time well spent in my book.
              Using the drill press outfitted with a step drill to enlarge the required hole in the F-1201C firewall to 9/16”.

The reason the step drill drifts can easily be seen in the next photo. The flange on the F-1217A-R tunnel rib offers more resistance on the left side of the hole so the step drill will tend to drift right because there is less material there.
            Marking the location on the forward flange of the F-1217A-R tunnel rib which requires removal of material.
                                             Using a Dremel tool with a cutting bit to quickly remove the excess
                                             material on the forward flange of the F-1217A-R tunnel rib.
                           Final smoothing of the F-1217A-R tunnel rib relief with a sanding drum on the Dremel tool.
The finished hole … the F-1217A-R tunnel rib is attached onto the F-1201C firewall .. looks like it was drilled in place.

Moving on, a couple of small F-1201U flat spacers were cut out of raw stock to 1 1/2" each, deburred and set aside for priming.  Next up was the separating of the four F-1257 rudder pedal support channels on the band saw followed by a deburring on the Scotch-Brite wheel.
                          Using the band saw to separate the four F-1257 rudder pedal support channels from one another.

The plans call for dimpling the nutplate rivet holes on the F-1257 channels using #40-100 degree dimple dies. However, only three of the four F-1257 support channels require the nutplate holes dimpled … these dimples correspond to factory dimples already in the F-1201B firewall shelf.
                Dimpling the nutplate rivet holes using the pneumatic squeezer outfitted with #40-100 degree dimple dies.

The plans instruct the builder to also dimple the aft two holes on all the F-1257 rudder pedal support channels to #30-120 degrees flush on the bottom. Those holes can be seen in the above photo marked in red on the F-1257 channels. The corresponding holes (also seen in the above photo) on the F-1201B firewall shelf were also be dimpled to #30-120 degree per the plans.