Earthstar Forums

I just read the article on the Laminar Magic S-4 again (yes I saved it in my airplanes files), and am just totally impressed with his accomplishments. Looking at the S-4, it reminds me how the Gull
2000 and Odysey share some of the same streamling techniques, and Mark has mentioned how he has used wind tunnel experiments to reduce drag, and I think that by continuing to remove drag will be a fun experiment. My next goal is of course, wheel pants with the brake parts covered. I do really want to see how fast the 503 52hp can go with fixed gear. There already is a Czech single seater with retractable gear that can do 126mph, but the wing and fuselage with a front engine appears to be draggier than the Gull. I do recognize that Mark's airfoil was designed for high lift and efficiency for the 28hp 277 Rotax, and as an ultralight still was limited by the 63mph to be legal. I had to smile, when I read Mr Stonjick's comment about how fast a serious experimenter could make a 254lb ultralight fly, technically still only 63mph, but maybe with only 10hp? Now that we are/can be officially experimental-light sport airplanes (E-LSA), we have a new top speed to play with, and a new higher gross weight. I probably can't approach the 138mph of LSA's, but it will be fun seeing how fast I can go without a serious wing airfoil redesign by Mark.

Hey, we're experimenter's right??

kb

Did you ever read up on the design tricks that Mike Arnold used on the AR-5?
Loren


No, but I sure would like to. Do you have any links or book titles?

kb

<http://www.ar-5.com/> http://www.ar-5.com/


_____

Did ya try Google?
AR-5 or ar-5?


http://ar-5.com/

http://ar-5.com/gallery/AR-5

http://www.aircraftspruce.com/catalog/b ... rnold1.php

Allan,
Thanks for sharing. I just read in his own words how he got there, and am just stoked about how fast he got a 582 to go, and he's got the engine in the front. The other real fast plastic 2-stroke light speedster was the Lightening Bug, but I don't know if it was ever sanctioned, and they used a 3-cylinder 100hp water cooled engine. The Gull will definitely never be in that speed territory, but it's fun to maximize what we have. My goal is to keep up with the 80hp 2-seaters flying solo, and to do that, I will have to milk 125mph out of the 503. Putting the motor back on the Ivo prop after flying fixed pitch for a year is exhilarating, as all my speed mods were done with the prop fixed. Now I can climb like stink, push it over and shift into high gear (er prop), and bury the airspeed at 120mph. Now to true out the static ports and go out and do GPS speed runs.

kb

No, I just use Allan's link. What a beautiful plane, and stinking fast!

WEll, added it to my fly folder. had glazed past it when i saw the AR-6
being adjectivized as a formula 1 and then it's a single seater ya. The 0.88
sq ft flat plate jumped out this time, but Hoerner's book is another 45 yrs
away from being free it seems, guess i'd better read on about inertia and
things.. KR-2S i did ogle at for a few days, krnet.org. wonder which planes
are those in Gary's Gull photo folder..

Well I did some speed runs yesterday, and realize that a true 125mph maybe an illusion for a 503. I did the runs right over airport here at about 1800'msl. The airspeed was buried past 120mph on downwind, where the GPS was at 120mph at the highest speed, then when I turned 180 degrees, the GPS went to 100mph with the airspeed still at 120. That averages out to about 110mph true. The 503 was taching 6300rpm, and maybe I could have sqeaked a mile or to by fine pitching the prop for 6600rpm. I think that I'm up against the drag wall of the wing, but when I pull the power back, the speed stays near a 100mph at 5400rpm, showing how efficient the wing is for lower speeds

Wheel pants next.

kb

In a message dated 2/22/2011 9:09:59 AM Pacific Standard Time,
kessb@wavecable.com writes:

runs right over airport here at about 1800'msl. The airspeed was buried
past 120mph on downwind, where the GPS was at 120mph at the highest speed,
then when I turned 180 degrees, the GPS went to 100mph with the airspeed
still at 120. That averages out to about 110mph true. The 503 was taching
6300rpm, and maybe I could have sqeaked a mile or to by fine pitching the prop
for 6600rpm. I think that I'm up against the drag wall of the wing, but when
I pull the power back, the speed stays near a 100mph at 5400rpm, showing
how efficient the wing is for lower speeds

Wheel pants next.

kb




Hi Kess
Its not the wing, The drag of the wing at that speed is only about 6# the
wheels are about 17# . And there is the fuselage and tail, the area behind
the engine were the air does not flow easily around the back of the cowl. If
you wanted to go faster you would ad more pitch, or else you would be
putting on the brakes, maybe, it is a fine point that needs to be tested. Try
deferent combinations, do a 360 and find out witch way the wind is blowing
and how strong with your GPS than fly in to the wind and measure your speed
and ad 1/2 the difference between the fastest GPS speed and the slowest and
you will have an accurate true air speed under that condition. at that
time, during that particular test.
Manufacturers like Cessna have to do a lot of repeated runs to average the
data to come up with a true observation of the speed. You do need to get
the static port out of the cockpit if you want to fine tune your nombres.
Other wise every time you breathe the airspeed will go up momentarily as you
reduce the cockpit pressure. I don't bother with a static port out side on
my plane since I don't see the ASI as all that important. Wen I test fly an
airplane I don't care if the ASI is even connected, I fly by angle of
attack by looking out the window, and this gives me the best reference of speed.
Remember.
The scientist is looking for the facts regardless of his desires. This is
the way to find the right places to apply your hard work to achieve the
greatest gains. Take the time to establish your base line nombres before you
make any changes and every one will benefit from your experiments.
Happy Flying
Mark