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(Earl Stahl's Vultee XP-54... pg.3)
Using "Balsabug's" tutorial on the SFA
Forum, I made up some new prop blades out
of two laminations of 1/32, and cured them overnight.
I was able to "de-glue" the plastic
ones off the hub without destroying everything.
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I took her out to the field after making the
changes I wanted including the new prop assembly.
I was able to shave 0.1 ounce of weight from
the prop assembly. |
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Test glides showed that the incidence angle change
on the stab was worth the effort. I adjusted the
trim tab to neutral and soon discovered that I could
remove some of the nose weight! I built up a new
motor out of two loops of 1/8” - 36”
long and proceeded to wind in three hundred turns.
When I built up the new prop assembly, I reduced
both the pitch of the blades and the effective area.
First flight showed immediately that the thrust
line shim we were using before the stab incidence
change was not helping, so I removed the shim. The
glide was appreciably better but not great.
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I slowly added more turns to the motor noting the
behavior each time. I was able to adjust the tab
on the right wing to a more neutral position since
I wasn’t trying to overcome as much torque
as before but still letting the torque push her
around in nice lazy left hand turns. When the rubber
started to run out, the wing tab would take over
and transition her into a nice flat right hand glide.
I removed a little bit more nose weight and compensated
with a stab trim tab adjustment and got better results.
I kept on flying adding more and more turns each
time until I could wind in 1200 turns. It looks
like I will need to add a small shim at the top
of the prop block to counteract a tendency to power
stall on climb. Otherwise, there were no bad habits.
I could have gone higher, but I was beginning to
run out of field.
Just for scientific purposes, I made up four little
prop blade extensions to test whether the reduction
in prop area had any positive or negative effects
on performance. I made a couple of flights and I
could not detect any appreciable effect. I should
have put a stopwatch on it to see if my flight times
had changed.
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Now that I was pretty confident in this ship, I
devoted some time to adding the small amount of
detail required to give it that finished look. The
only scale documentation I could find were some
Air Force photos in black and white. I made a judgment
call on the colors and finishes based on what I
could glean from these pictures and what little
I know about markings and finishes for the era.
The plane appears to be overall khaki green with
a natural metal finish around the engine cowling.
The propeller blades and spinner are black. Some
plastic models depict a sky blue underside. The
national insignia and serial numbers on the tail
are colored tissue that I cut out and doped on.
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I took her out for a few more trim flights and noticed
that as I added more turns, I was getting into some
strong torque reactions on launch. I inserted a
1/16 shim at the top of the plug and a 1/32 shim
on the left side of the plug for a little right
thrust. This did the trick. She launches out in
a nice left hand spiral each time with a nice right
hand transition to the glide. The performance of
this model makes me wonder how well one would fly
scaled up to about 32 inch span?
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