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Cowling
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Here I am starting
to fit my cowling. The first step was to rough cut the hole for the gear leg
and the hole for the prop hub. 4/22/01 |
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I was then able to
start fitting the cowl to the plane. I did not screw the cowl to the prop
hub as called for in the plans. I just let it float so that I would not have
the problem of it shifting when it is unscrewed (Thanks Tony).
4/22/01 |
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I had to cut down
the cooling fins on the #1 cylinder head of my jabiru engine to clear the
close fitting cowl. 4/22/01 |
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I then was able to
start cutting the back edge of the cowl to match up with the fuselage. I
did this in several steps, rough cutting, checking the fit, cutting a little
closer, rechecking the fit, cutting a little closer... 4/22/01 |
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I did find that I
was bumping against the engine at several points. One was the exhaust pipe
on the right side of the engine. I talked with Jeremy at SnF and he confirmed
that I my pipes are for use with a muffler. He has another set of pipes (that
don't rub the cowling) if you want to run without he muffler. The other spot
was the oil pan fins. I noticed Tony had ground down his fins so that
they would clear the cowl. I have not decided what i will do yet.
4/22/01 |
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Here I have graduated
from duct tape holding the cowling together and I am starting to install the
piano hinges that will hold everything together. To get to this point I had
to do a lot of fitting and trimming and more fitting and trimming.
11/19/01 |
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I started by attaching
the hinges along the sides, when I had the center seams matching, I took the
cowl off and fit the hinges to the center. I then worked on attaching the
hinges at the back. 11/19/01 |
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Here you can see
where I have roughed out the opening for the air exits. 11/19/01 |
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I spent a lot of
time making sure the cowl would match up well with the prop hub. I was a
little off and had to sand the prop opening a little on one side to get good
clearance all the way around. 11/19/01 |
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You will notice that
in the above picture I was thinking about creating a NACA style inlet just
below the prop hub to let air flow over the oil pan cooling fins. But I had
to cut down the fins to clear the cowl and did not think that there would
be much room for cooling air so I just created an oval opening. I think if
I had to do it over again I would not cut down the fins and open up the front
cowl so the fins could protrude through. I would then install a duct to direct
air over the fins like this.
11/19/01 |
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Here is the opening
I cut to access the dip stick. I'll make a hinged cover to enclose this later.
11/19/01 |
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To create a low pressure
area at the exits, I put some cowl flaps on hinges so I could try out a few
positions and get the perfect amount of cooling. 11/19/01 |
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Here is another view
of the cowl flaps. Also you will notice another exit hole for the air from
the oil cooler. My plan is to take in air from a NACA vent on the side of
the cowl, run it through the oil cooler, then through a heat muff on the
muffler to heat up the air even more. I will then run the air to the cabin
heat box where the warm air will be sent into the cabin or out through this
exit. 11/19/01 |
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I plan on using the
muffler that came with my Jabiru. I am sure people living around the airport
will appreciate that. However, the muffler pipes bump against the cowl so
I opened it up to let the pipe stick out a little 11/19/01 |
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I then used a couple
layers of bi-directional fiberglass to create a small blister to cover the
pipe. 11/19/01 |
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I then used a "micro"
mixture smooth it out. "Micro" is tiny hollow glass spheres that you mix with
epoxy to create a light weight filler. For this filler, I used West Systems
epoxy which is not as strong as some other epoxies but it is much easier
to sand. 11/19/01 |
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Here you can see
the blister and the inlet. It this point, I have also laid up several layers
of fiberglass behind the center seam just below the prop hub. I placed plastic
wrap under the fiberglass on one sided of the cowl so that I would not permanently
connect the cowl haves. This will create a spot to install a few Southco
1/4 turn fasteners. . 11/19/01 |
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Here you can see
where I attached two NACA vents. I bought these vents from Vans Aircraft .
11/19/01 |
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One vent will blow
onto the air filter for the carburetor. The other will be connected to the
oil cooler. 11/19/01 |
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I attached the vents
with "flox" which is cotton fibers mixed with epoxy. It is often used as a
structural filler but it makes a good adhesive as well. 11/19/01 |
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After getting my
cowl painted I started running my engine and found that the front right exhaust
header was still too close to the cowl despite the blister I had made to
clear it You can see here it its starting to blister the paint.
7/26/02 |
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From inside the cowl
you can see that the pipe is starting to burn the epoxy. 7/26/02 |
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To fix this I cut
out the old blister to about twice the size hole I had made before and relayed
a new bigger fiberglass blister. I first laid out the fiberglass layers on
plastic wrap and wet out the glass with epoxy, squeezing out the excess epoxy.
Once the glass was wet out I flipped over the plastic wrap and applied it
to the inside of the cowl and gently pressed out the size blister I wanted.
. 7/26/02 |
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When the epoxy cures
I pulled off the plastic wrap and I was left with a nice smooth blister. I
will refill and repaint once I am sure I need no more mods to the cowl. After
5 hours of running the engine this blister shows no sign of burning.
7/26/02 |
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I further keep the
cowl from over heating I wrapped the pipe with exhaust wrap, Wicks part# 11152.
7/26/02 |
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