Prepped Inside of Lower Cowl

I started prepping the inside of the cowl for a seal coat of epoxy.  I’m going to tint the epoxy white so that it will be easy to see oil or fuel drips.  I’ve seen other builders just spray paint the inside of the cowl white, but that won’t be impervious to solvents like a coat of tinted epoxy will be.

Worked on Cowl Hinges

Tyson Weihs, one of the co-founders of ForeFlight, stopped by tonight to check out the project along with my buddy Andre.  We spent an hour or so talking about RVs before I got started building.

I spent most of the night working on the cowl attach hinges.  First up was to pull the lower cowl and finish drilling the stainless hinges along the bottom edge of the cowl.  Drilling steel is a pain, and you really want to drill the hinge before drilling the cowl to avoid elongating the hole in the cowl.  Next up, I removed some of the eyelets in the hinge that runs along the top of the firewall.  The hinge pin has to be removed and installed in two separate pieces through the oil door.

I then drilled additional holes in all of the hinges that will bond to the cowl (nine total) and deburred everything.  The small holes will be used for AN426A3-5 rivets (not AN426AD rivets since that can crush the fiberglass).  The larger holes will allow the epoxy/flox mixture to squeeze up through the holes and bond to the layer of glass that will be laid over the rivet shop heads.  This will provide a far stronger joint than just rivets alone.  I will be using West Systems G/Flex epoxy which has a modulus of elasticity of 150,000psi.  This is substantially more flexible than their 105/205 epoxy which has a modulus of elasticity of 450,000psi, but substantially more rigid than adhesive sealants like the MC-236-B2 sealant I used on the tank.

Started Oil Door

I decided to get started on the oil door tonight.  I started by grinding down the edge of the flange to create a better-defined joggle.

I then trimmed the door itself and radiused the corners so that the door fits down nicely in the cutout.  The trims on the cowl itself are a little sloppy as you can see below, but that won’t matter.  Once I have the door exactly where I like it, I’ll put some structural filler here and use the door itself to mold it perfectly.

I then drilled the hidden hinge to the cowl and door.

The hinge has a spring that will hold the door open while I’m checking the oil.  The door is pretty flimsy right now.  I’m going to need to stiffen it in order for it to work.

Finally, I spent a little time debarring all of the holes I drilled in the cowl attach hinges.  I still have a few more to go, but this makes a big dent in the deburring.

Finished Drilling Cowl Hinges

We got back from a short vacation in Yosemite National Park yesterday, so I got back to work tonight.  I drilled the other P4 hinge to the right side of the cowl then mated the P3 hinges to both sides and installed the upper cowl.  I transferred the hole positions and then drilled the upper half of the hinge to the cowl.  Here’s the right side of the cowl.

And here’s the left.

Now that the cowl was locked in its final position, I drilled the rest of the holes along the top of the firewall.  The cowl is amazingly rigid now.  Pushing even gently on the cowl moves the whole airplane and there is no perceptible flex in the cowl itself.  If it’s this still with just clecoes, I can only imagine how much stiffer everything will be when the hinges are riveted and glassed in place.

The front left corner of the cowl has a small alignment problem.  I’ll have to build out the upper cowl to bring it out flush with the lower cowl.

The front right corner also needs a bit of work to make things line up nicely.

Received AveoMaxx Taxi/Landing Light

I received one of two AveoMaxx taxi landing lights from Aircraft Spruce today.  These lights are very compact and very bright, but all LEDs for low power consumption, heat, etc.  They come in a nice anodized aluminum enclosure that will be mounted in my wing tips.  Since they will be mounted a lot farther forward than the typical wingtip landing lights, I’m hoping the longitudinal face of the wing tip cutout won’t shade the area in front of the plane from receiving light.  The holes on the top will be used to mount the nav/strobe lights.  There are actually two separate lights in the enclosure.  The center light is the landing light and is comprised of a single massive (nearly 1 square cm) LED that is focused in a fairly tight spot.  Surrounding that is a ring of small LEDs that form the taxi light.  These have a much greater dispersion to more evenly light up the ramp.  I came out at night and tried these, and the light output is very impressive.  Since I’m installing two, I’m hoping that will be plenty of light for night ops.

Worked on Cowl Joints

I drilled both lower side hinges to the cowl.

I then clamped a section of MS20001P4 hinge to the lower cowl on the left side and laid out some holes on approximately 1″ centers.

I then drilled all of the holes.

Here’s a closeup of the joint.  I’m using MS20001P3 on the upper half since I don’t need the extra width.  I installed the P4 on the lower half so that I could bias the hinge up enough to have a small strip of solid hinge material at the joint line.  Doing it the way the plans specify would mean that you would be able to see the hinge ears through the joint which looks pretty crappy.