I bought these for another airplane, but thought I would try them first
temporarily on my amphib Rebel to see what difference they made. After
attaching them with double sided carpet tape at the prescribed location on
the wing, I took it up for some stall trials. My gross weight was exactly at
1650 for the test. I tried it first at the neutral flaperon setting. I
hadn't done a stall for a while, but seemed to recall it stalling between 45
and 50 mph at that weight with neutral flaperons. Well, I kept pulling back
and watching my airspeed go all the way down to below 40 (around about 38, I
think, as it doesn't read too accurately below that) before it finally felt
like a stall at a ridiculously high nose angle. So there was definitely a
dramatic drop in stall speed. Because it was so slow already, I didn't even
try it with full flaps.
However, it was harder to tell what difference if any it made to my
take-offs. When you are flying floats, you can't rotate at a high angle of
attack because of the float tails. My take-offs were plenty fast, but never
had a chance to put it to the test in a high elevation lake on a hot day or
with a real heavy load. At near sea level my take-offs were always pretty
fast anyway unless I was really loaded down. I flew this way for a couple of
weeks, and it seemed to perform pretty well, but I had no quantitative way
to measure my take-offs or climb rates (which also seemed better).
I did not notice any other handling differences or change in cruise speed.
They are also supposed to improve low speed handling, but with floats and my
previous 50 mph stall speed, I usually would never fly below about 70
anyway.
So for this long weekend, I removed the VGs to see if I would notice a
difference again. Of course the first thing I tried was the stall speed once
I had the right fuel quantity to make it 1650 gross again. This time it
buffeted at around 50 with a clear fast dropping stall by 48 mph. That means
the VGs probably improved stall by about 10 to 12 mph which is a lot more
than I expected. And that was at neutral flaps.
I did a few take-offs on land and water, and sure enough it seemed to be a
little longer to take-off without the VGs. It was especially noticeable on
the water, where I needed to be a little more patient so I didn't ruin my
sweet spot trying to lift it off early. Also, my climb rate also seemed
lower by about 2 or 300 fpm.
The only problem with this testing, is that it is a little too qualitative
(other than the stalls), so am not prepared to say with certainty, that the
VGs did indeed improve take-offs and climbs. The real test would be at
higher altitudes with a good load and I just haven't had a chance to try
that yet. Also, taking off beside another Rebel would help.
However, next week I will be flying with Bruce G, so am going to put them on
again, and see if we can get a better sense of comparison with his plane.
Anyway, thought this would be of interest to the group, as I'm not sure if
there is anyone else out there flying a Rebel with the VGs.
If these things actually make a difference at high elevation lakes, then
maybe I won't need that 0360 clone after all.
Related to this, was talking to another Rebel float plane pilot, (won't
mention his name to protect the innocent) but he told me it took him half an
hour this morning trying to get off a 3800 foot lake. He was pretty loaded
with camping gear, full fuel and his wife, so I was not surprised, even
though he had the 160 hp 0320 (mine is only 150 hp). He said his biggest
problem was getting on the step, and he finally did it after he got a little
headwind breeze. He said he tried every trick in the book, with wakes,
rocking it, flaps, no flaps, but it just wouldn't go. Once on the step, he
eventually was able to raise one float, allowing it to gain more speed until
he finally lifted off. He had to keep flaps in neutral initially, and then
full flap at speed to lift off.
So that would have been a good test for the VGs.
Walter
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