Cowling Construction

The first step was getting the cowling fitted behind the prop spinner and cutting

the slot for the nose landing gear. There was a considerable amount of sanding

required behind the spinner in order to make the hole round and to allow the two

halves to fit together properly.

 After the two halves were fitted together, the top cowling was clamped to the

spinner plate with a 1/4 inch wooden spacer between. It is a good idea to make

alignment marks in order to accurately reposition your cowling during the

trimming process. By shinning a light through the cowling, we could mark

accurate trim lines along the firewall flange.

 After trimming the rear flange, we sanded it slowly back to the original trim

line. By doing this you get the best possible fit, but it does take some patience.

After the cowling is fit along the firewall flange, we drilled into the top hinges.

 It was nice to just stand back and see the fuselage grow longer and

start looking like a real airplane.

In order to fit the lower cowling, we used a strap to hold it in place. The

bottom flange was trimmed and cut first, then the side flanges were trimmed

and cut. This method provides good results. The cowling must be removed

before each cut is made.

 The following photo shows the wooden spacer and the three screw holes on

each side of the nose joining points.

Once we trimmed and sanded the bottom cowling, we drilled the cowling

into the bottom and side hinges.

Next, it was time to install the side hinges. In order to make the cowling

easier to remove, the hinges are mounted higher in the rear than the front.

All of the holes are countersunk, and the hinges are installed with Epoxy

putty. This is the same stuff that we used around the windshield. Because

the cowling takes a lot of stress, Van's recommends doing this to prevent

the rivets from working loose in the fiberglass.

The final steps were to Epoxy Putty the inlet ducks, fit and install the oil

access door and also fit and install the exit air bracket. We decided to go

with all stainless steal pins as an upgrade. It just seemed like a good idea.

 In order to protect the inside of the cowling from oil and grime, the inside

of cowling halves were painted with epoxy paint. We used two part floor

epoxy and just rolled it on with a small roller. The external part of the

cowling requires several applications of epoxy fiberglass resin, cut one-to-one

with Acetone, and after each application, the cowling gets sanded. Because

of the honeycomb pattern, it takes at least two applications to get the surface

smooth. In order to fill the larger holes, we used marine epoxy and sanded

it once dry. After this step was completed, we rolled a coat of epoxy paint on

and then lightly sanded the surface in order to fill the tiny pinholes. According

my paint shop, this is the most efficient method for final paint preparation.

Be patient because it is worth the time spent once it is painted.

The final order of business is the prop spinner. The builder need to make a

cutout to contour to his or her specific prop setup. If you make a template out

of cardboard first, then this is job easier. We undersized the cutout and then

carefully trimmed and sanded them out. The trick here is to insure that you

have located the exact opposite side of the spinner, and this can be done

by measuring the circumference and then dividing by two. A Dremel tool

with a stout cutter attachment seemed to do the trick nicely. After that,

we are ready to install the Prop Spacer along with the rear Spinner Plate.

It requires a wooden block and a hammer, but eventually the studs will

go into the Prop Hub.

Now, we are ready to drill in the spinner into the upper and lower Spinner

Plates. Because balance is very important, the spinner needs to be aligned

using a felt-tip marker taped to a ladder. The Prop Spinner assembly is then

rotated such that you end up with a dot instead of a circle at the very end

of your spinner. Screws must be located evenly around each plate in order

to maintain good prop balance, and once the screw holes are drilled-in, then

filler plates under each blade much be fabricated by the builder, and nutplates

are installed for each screw hole drilled.