Tried standard tips, but did nothing for me. Then I had to put
new
tips
on
(another story).
Elected to go with Finch Tips. Turned down and invented by Dr
Finch.
In
fact I put them on
Rocky Jones racer, OLE BLUE. Rocky said they did exactly what
he
wanted.
Then he
died as a result of a mid-air.
At any rate I put hem on my LongEz (you flew with them) and it
resulted
in a
lot more
elevator authority due to delaying tip vortex.
I like them, and so will you. Plans are available if you wish.
Fly fast, land slow
Bill
The weirdest wing tips have the most effect. Here is an
aerodynamically
test and approved by Canada wingtip design called the "reverse
shear"
that has proved to have beneficial performance effects. Strange, no?
Performance data by user......
Type of aircraft: C177RG with turbocharger
Modification to date: Tail cone fairing, exhaust faring.
OAT at sea level: 59 deg. F
OAT at 5000': 43 deg. F
Gross weight: 2401 lbs.
CG: 106.7
Winds: 12 to 15 KTS straight down the runway.
New shear wingtip
SL to 5000' 7min 57 sec average FPM 629
1000' to 5000' 6 min 10 sec average FPM 649
IAS at 5000', 25" MP, 2500 RPM, 130 KTS
Original tips
SL to 5000' 8 min 23 sec average FPM 596
1000' to 5000' 6 min 34 sec average FPM 609
IAS at 5000', 25" MP, 2500 RPM, 128 KTS
I performed power on stalls with both tips, gear and flaps down. New
shear tips: 38 KIAS Original tips: 43KIAS. The stall break was much
smoother with the new shear tips, less roll also. I also found with
the
new tips that I get the same rate of climb no matter what speed I
fly
between 82 KIAS and 95 KIAS.
[Marc Wiese]
You will get more improvement at even higher altitudes Marc as in
effect
you have increased the span & wing area, reduced the span loading and
therefore
reduced the induced drag due to lift. What you have also done is
slightly changed the lift curve slope which is dangerous to do on a
canard
type airplane. The balance of lift curve slopes between main wing and
the canard is critical to the stability and control of canard type
airplanes.
In other words do not increase or decrease the span or area of a
canard.
Paul,
Although these are not installed on a canard, which I am sure has myriad
considerations different than conventional type aircraft designs, others
not building a canard may want to consider such a reverse design for
their wings. Many different popular aftermarket designs were tried by
this designer, and all fell short of this one, including droop type,
winglets, reverse winglets, etc.
I also want to point out that this wingtip is smaller at the tip and
larger at the rear than the original, so the gross increase in area is
not that large, guessing about a square foot each. Vortices studies were
also done on this design, and show them to be much less due to the
reverse shear shape, which was one of the primary goals to increase
performance.
Marc Wiese
Induced drag is manifested in the vortices from the wing tips. I takes
energy to generate these vortices and that is an outgrowth of the incremental
drag and the incremental HP requirements is a result of that increased drag.
The vortices are generated by the pressure on the bottom of the wing being
higher than the pressure on top. This results in a lateral airflow outboard
under the tips rolling up and over the top of the tips.
Vortices will be less as the span loading is decreased. This would work even better
if these tips where made even longer. The draw back to these schemes is they
increase the bending load on the spar. In effect they just extend the
wing span.
Any device that does not extend the wing span would be my definition
of a true unique wing tip. I would call these wing extenders. Winglets
also reduce vortices but do not extend the wing span. Also there is
such a device called a Hoerner tip used on a lot of bush planes.
That too reduces vortices yet is not designed to extend the wing span.
Sails planes are good example of low induced drag
wings as they have a lot of span. The spars however are designed to
take the increased loads.
BTW To give you an example of the importance of induced drag at high altitude
a fully loaded 747-400 with large winglets can barely make 30,000 feet. As
it burns off fuel during a trip from Sydney to LA it can climb up to about 37,000 feet.
I confirmed this by talking to airline pilots and I monitored this on the seat
LCD movie screen on the way back from Sydney last week.
Paul Lamar
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