Before completing the cosmetic work like cowls and covers, I wanted to
find out if this thing would fly. Although I forgot to weigh it while
I had it assembled I know that it was somewhat overweight at around
16lbs, with more than a third of that being the engine! The CG had
ended up further forward than I wanted it, but flying it would
indicate how serious a problem that might be. My biggest concern was
the possibility of a difference in the rigging of the two wing panels,
even half a degree difference in incidence would give a pronounced
roll at lift off.
Attempt Number OneTaxi trials showed that it was not overpowered and a long roll was
required before it started to rotate. I was mightily relieved on
its first lift off when the wings remained absolutely level
requiring no aileron input. However, nearly full up elevator, and
there's plenty of it, was needed to get it to break ground.
Adjusting the decalage by giving the stabilizer some negative
incidence did shorten the take off run slightly but it was quite
clear that the CG needs major movement. A few, short, straight line
flights were enough to convince me that the Ephinay will be a good
flyer, but not before it gets more power and a new CG - anybody got
a G38 for sale?
Attempt Number Two
The consensus was that the plane did not achieve a high enough
speed at take off and that the elevator was having to do too much
work because the decalage (the angle between the stabilizer and
the wing) was not right. We decided that the CG position was not
at fault, though we had some reservations about the possible
effect of turbulence over the tail surfaces created by the open
box of the fuselage. So, we decided that more power and a
changed decalage would probably solve the problem. Careful
recalculations produced a stabilizer/wing set up and a CG position
which was moved slightly forward.
Art Alfano kindly loaned me a Quadra 40 which, as well as having
more power was more than a pound lighter than the converted
Homelite 25. This meant constructing a new engine mount as the
new engine had to be moved forward 4 inches. Careful measurements
of the existing decalage showed it to be already exactly where it
should be, which cast a little doubt on our theory that it needed
to be changed.
Modifications made, it was time for the rubber to hit the road. A
sprightly take off run and she lifted off the deck into a healthy
climb, apart from a lot of up elevator she was flying straight and
true without needing any trim adjustments. What a great feeling
that was!! A 180 deg turn was made very easily but after leveling
off she started to nose down slightly, a bit more "up" should have
leveled her out but it didn't. She started to nose down more and
more and I continued to apply more and more "up" until it ran
out. She was still nosing down and I was bending the stick when
the ground rose up in greeting and ended the flight. I just stood
there in disbelief - I thought we had it licked.
The tubular steel engine mount was totally demolished as it
absorbed nearly all of the impact, it must have have hit at about
45 deg. Otherwise damage to the rest of the plane was minimal. A
couple of servos stripped their gears, the aft fuselage tube
collected a slight bend and there was minor stress damage to a
wing panel. Detailed examination may reveal more damage but it
won't be enough to prevent a third try!
The experience gained so far suggests very strongly that the
problem is indeed turbulence from the open box end of the fuselage
plus that caused by the unfaired center section. The tail
surfaces are working in very turbulent air which severely reduces
their effectiveness. Our guess is that at take off the stabilizer
and elevator were only just effective (hence the large amount of
up elevator needed to make it lift off) and as the plane leveled
off from the climb its speed increased and therefore so did the
turbulence, making the tail surfaces even less effective,
resulting in the conversion of my pride and joy into a lawn dart.
For attempt number three I will reduce the turbulence over tail by
fairing over the center section to smooth out the airflow over the
radio gear and by constructing a cone over the open box end of the
fuselage - as well as a new engine mount of course.
Attempt Number Three
The Quadra 40 was returned to Art as he found he had a plane
for it and I was left wondering what to replace it with. Both my
G38's have been doing a great job in the Cub and the Marquardt
Charger for the last dozen or years and it seemed a pity to break
up those friendships. The Homelite had proven itself not up to
the task so rather than go out and buy a new engine for a plane
that has shown some reluctance to fly, I bit the bullet and
installed the G62. This engine had been gathering dust since the
HA-1 "Iron Maiden" died. At two and a half times the size of the
Homelite power should not be an issue! Unfortunately the weight
goes up with the power and the Ephinay now stands at about 20lbs -
but with 26lbs of thrust.
The picture shows the fairings added at the back of the box and
over the center section, hopefully they will do the trick.
Creating a cowl is out of the question until the Ephinay proves
itself a satisfactory flier.
Success!
With the new fairings in place, everything checked out and the
G62 eager to go, the Ephinay taxied out to the end of the
runway, and to my delight and that of the audience she lifted
into the air after a modest ground run and climbed out very
smoothly and under full control.
After few circuits at a safe altitude it became clear that she
was very responsive to all the controls. Unlike the previous
attempts I had plenty of elevator control which seemed to prove
that the turbulence generated by the open box and center section
did seriously interfere with effectiveness of the tail
feathers. Apart from a few clicks of elevator trim the plane
flew straight and true without surprises, which is what one
would expect from a commercial model, but which cannot be taken
for granted for the first flight of a new design. There is no
substitute for that thrill.
Now that I know that it flies, and flies well, the next phase
will be to do a lot more flying to learn its characteristics and
get it to handle the way I want it. Designing a throttle
linkage to operate precisely and reliably across a fully
flexible motor mount is a bit of a challenge and I was a little
unsure of the arrangement I had devised for the G62. I had
checked the response before taking off but my doubts were
justified when for the second landing the idle would not come
down low enough and the plane kept on flying. A couple of clicks
on the trim resulted in the engine quitting on approach. I was
surprised by how comfortably the plane just floated in for a
greaser.
After a couple of false starts I am very happy with the way she
flies and look forward to further developing it!
The experience of creating a brand new design and then flying it
without any prior knowledge of what will happen when it leaves the
ground for the first time is fascinating and exhilarating. It is
unique and gives a measure of satisfaction not available from any
other type of flying.
