My Next Pod

Four years ago, I built my first instrument pod – I called it the Nerf Fairing, because I used a closed-cell foam to create the body of the pod. I wrote about it here: http://ozreport.com/forum/viewtopic.php?t=10760&highlight=nerf

The pod worked very well overall. After 4 years, it looks as good as the day I finished it. There were, however, a few things I was hoping to improve.

First, the vario was positioned behind the GPS. This meant that at faster speeds, I had to look behind me to see it. Also, the GPS was far enough out front that I had to speed up and bank left to be close enough to read the street names on the moving map. Both were less than ideal.

Second, the connection jacks from the vario to the GPS and wind vane were somewhat exposed. While it likely makes little difference in terms of drag, I thought I might be able to improve that in a next-generation pod.

Lastly, (and most compelling) is that I needed a winter-time project. Frankly, building a new pod was going to be a pure vanity project - I wanted a new toy, and was prepared to build it.

Pod design had evolved since I built the Nerf Fairing. Dustin’s pod, for example, is more streamlined than the predecessors; the vario was out front where I wanted it, and the teardrop shape is quite appealing. There is nothing available in this style that fits my older instruments, so I would have to come up with a few tricks of my own.

Over the last few years, I’ve gotten more confident in working with carbon fiber. I’m certainly no expert, but my skills have improved with use. I decided to try building a CF pod. Apologies in advance for not having mid-process photos.

The first step was to shape the guts of the pod. I used a chunk of simple packing Styrofoam; shaping it first with a hot-knife, then with my dremel to get the shape. On the interior, I got a very nice instrument fit by wrapping them both in sandwich wrap, then placing a strip of mylar around them. I could then pour an epoxy/micro-balloon mix into the remaining cavity, which left me with a perfect friction fit on the first try. I used a very lightweight spackle in some places to correct spots that needed a bit of filler.

The carbon layers were applied in a way I haven’t used before – laying them directly over the pod, but not wrapping them. It didn’t take much to get the layers to stay where I wanted – I used a few push-pins if the carbon didn’t behave. After curing, I sanded each layer to barely expose the carbon, then applied the next layer. There are four layers at the back – where the most forces are applied – and each layer extended farther toward the front. Only the final layer extends the full length of the pod.

Once the carbon was complete, I used a fine brush to apply additional epoxy over the pod. The interior cavity got only enough to cover the styrofoam, but the exterior required some additional sanding and coats to get a nice finish.

I also built a pivoting mount –entirely from scratch – that includes a carbon-epoxy body which transitions nicely from the pod. I used simple hardware store material for the mount that cost around $15.

I didn’t think my carbon work looked good enough to leave it exposed, so I applied two coats of primer before spraying on a dark-grey metallic paint job.

I’ve flown with it a couple of times. So far, it does exactly what I hoped for, gave me a lot of satisfaction in building it, and cost very little to complete.

RM

The pod is designed to mount to my left downtube, hence the angle of the mount. Note the shaped plug for the wind vane jack, next to the small depression to reach the power switch.

Working with CF allowed me to make this pod somewhat sleeker than my Nerf Fairing, although my older instruments are thicker than the latest versions. Note the lanyard that connects all components, then exits near the back of the mount.

After creating the void for the wind vane and associated wiring, I used a bit of spray-in expansion foam to set the vane in place. The foam is firm enough to hold the vane well, but will provide some flex if I were to strike the vane.

No mounting holes in the back. The instruments are held in by friction, backed up with velcro, and secured with a lanyard.

The mount’s pivot arm is partially opened, exposing the sleeve around the mounting bolt. I don’t normally flip up the pod for launching/landing, but the pivot is good for impact stress relief.