I have read many posts
and web articles about the pros and cons of priming a homebuilt,
and the opinions range from "priming is unnecessary" to "priming
is the only way."
I am not trying to cut
corners, but I think that the overly complicated multi-stage
been suggested by some could needlessly extend the build time to
a point where it would not be a fun and educational exercise. Therefore,
I set out to find a simple primer which would provide at least
a small margin of protection against corrosion without putting
a rigorous set of extra tasks.
I think I have found a
product that will do the job. It is Sherwin Williams 988 self-etching
primer. It comes in a spray can, which should reduce set-up time.
Here are some links
to people who are using this stuff on their projects:
Primer Update: 5/6/2004
My procedure for priming the empennage parts was to first scuff the parts with ScotchBrite pads, then clean the parts with Acetone, and then (finally) spray the self-etching primer. The preparation work turned out to be a lot more messy, and a lot more trouble than I had anticipated. As a result, I have changed my procedure for the wing parts.
I decided that if I was going to have to clean the parts anyways, I may as well use Alumaprep. And, if I was doing the Alumaprep, I may as well go ahead and Alodine. So, the new procedure is as follows:
First, clean off any sticky substances (like stickers or tape) with Acetone. Next, working outdoors I spray on the Alumaprep/water mixture and scrub the part with Scotchbrite pads. Next, I rinse the part with a water hose and then hang the part in the garage so it can dry. Now I am ready for the Alodine. I either brush it on or dip the part, and after three minutes I rinse it with the water hose. Once again I let it dry. Finally, I prime with the self-etching primer. Although the self etching stuff is not really necessary after all of this work, I still do it because I want to maintain consistency with the parts I may need to quickly prime in the future.
The bottom line is that this new procedure doesn't take much more time than the old scuff-and-prime procedure, and I prefer wet scuffing to dry scuffing.
Primer Update: 5/11/2004
I ruined a gallon of Alodine. I figured I was doing the smart thing by working out in the nice spring weather. What I noticed about halfway through the process was that the parts didn't seem to be getting as dark as they were at the start. By the end of the batch of parts I decided I needed to find out what was happening. Was the aluminum causing the Alodine to wear out?
The answer? Don't use Alodine out in the sun. It is sensitive to the sun, so being out in the sun ruins it. So, I ruined a gallon of Alodine, but at least I don't have cancer!
I plan to add lights to the plane, so I investigated the options
and found that there are many ways to go about it. One
issue is the fact that with the big bubble canopy, you don't
want a strobe mounted on top of the plane. Another is the added
drag that can come as a result of placing lights on the fuselage.
Vans sells a light package which contains three combination
lights: a red with strobe for the left wingtip, a green with
strobe for the right wingtip, and a white with strobe for the
back end of the rudder. This is currently the setup I plan to
System Six is the
one I am currently planning to use.
Lights Update: 1/4/05
I bought my lights from CreativAir. Bill VonDane sells a complete lighting package which includes position, strobe, and landing lights. The only thing not included is the tail light, which I bought separately from Van's. The position lights are LEDs, and everything fits inside the wingtips.
Lights Update: 2/12/05
I have finished assembling the light kit from CreativAir. Check them out.
One of the strange things that I first noticed while I was working
on my Private Pilot's License was a distrust of all fuel gauges.
This started with my first instructor. He told me that the plane
I was flying in at the time had really bad fuel gauges so you
should never even look at them. So, I always used a stick to
measure the gallons of fuel in the tanks. After I passed my checkride
I started flying 172s, and again the fuel gauges are not very
Based on this experience, I decided that I want my plane to
be a little different. I want to be able to look at any instrument
and get some useful information from it, including the fuel gauges.
I have come to find out that fuel level accuracy starts with
the sending units in the fuel tanks themselves. Also, apparently
most fuel gauges are limited by the dihedral of the wings. I
can deal with only seeing the fuel gauge move if the fuel level
is below 15 gallons in each tank. What I don't want is some mechanical
foul-up with a sending unit causing the gauge to read incorrectly.
Bottom line: I have decided to install capacitive fuel sending
units in each tank. These are solid-state devices which have
no moving parts at all, and theoretically should last the lifetime
of the plane. The downside is that these units require a more
expensive fuel gauge, but the one I plan to use is really nice,
putting the ones in the old Cessnas to shame.
Here is some
information about the Electronics International fuel gauge.
Update 2/12/05: The GRT engine monitor will display fuel information, I only need to buy the senders. I won't be using any other fuel gauges.
Blind (Pop) Rivets
At times the plans
call for blind rivets to optionally be used in place of solid
rivets where a bucking bar or squeezer cannot easily reach.
I know most builders would prefer a solid rivet over a pop
rivet, but I cannot see why I should spend any time worrying
about these "optional" pop-rivets. I mean, I have a friend
who is building a Sonex, and the whole plane is covered in
pop rivets, so they are certainly strong enough. The two issues
I can think of may be that they weigh a bit more and they cost
a lot. Well, if we are only talking about a few here and there,
it seems that the time savings would overcome any additional
cost considerations, and the weight is probably so small a
difference as to not matter.
So, the bottom line
is that I will be using blind rivets whenever the plans say
I can. The factory demonstrators use them, so I will too.
After figuring out
that Van's ships the RV-9A with electric flaps as a standard
feature, I started thinking about the space the trim cable
and control would occupy. Initially I had decided to use the
manual trim because of the simplicity, but as I weighed the
options I came to the conclusion that it sure would be nice
to have the trim controls located on the stick, and since the
servo provides position information automatically, I won't
need a sensor to provide visual feedback of the trim position.
Ray Allen sells a nice position indicator, and some of the
engine monitors display trim status as well. So, I ordered
the electric trim servo so I could install it while I am building,
rather than waiting and having to do a retrofit.