9/15/96
Dear Jay,
Just got back from a killer XC contest this weekend and need to
get all this down on paper before it fades. First of all, I got the 10 K. I
tried for about 2 hours Sat. with the V-tail plane and never could get more
than double or triple launch height, though you could work lift there
pretty much at will. After seeing guys with heavier planes actually
finishing the course I broke down and tried the white plane with the
sniffler in it. I got it on the first launch. I wouldn't say it was easy
but I only had to work from below launch height once at the turnaround. It
was interesting actually being able to see the entire course from any point
along it.
The location: It's not on my map but we were in a place called California
Valley. Near as I can tell its about halfway between San Luis Obispo and
McKittrick. The terrain looks like the Yakima Valley without the river, a
lot less agriculture, and no town. The layout is as follows:
There is very little to hit anywhere in the valley. The lift has been
frequently documented at better than 600 feet per minute. People have seen
Sagitta XC's flying along fold up from hitting a strong thermal because the
fuse couldn't follow the wings fast enough. Joe Wurts was supposed to show
Sunday but didn't. Fortunately I was able to pick the brain of Gordon
Jennings, one of the current F3B team members. He was flying the following
plane:
The tips are incredibly light, comparable to my wood ones. He uses Spyder
Foam and really likes it. Poly is slightly less than my white one, no flaps
or ailerons. No spar, ? ply sub ribs like my white one. The center section
weights about 3 pounds, total weight is 10 empty. He doesn't like
multi-channel because you can land anywhere out here and it takes out too
much strength. These guys go Fast Fast Fast out here. The strategy is
generally to climb out fast and tight in the strong desert thermals and
burn like hell to get through the 500 ft/minute sink in between. Gordon
sets up his plane nose heavy so that it is still positively stable with
enough down trim to go at a steady 60 mph cruise. A sniffler is vital for
flying XC. I would go so far as to call it like a one eyed man in a world
of the blind. I realize that is completely opposite to what I said before
but I probably doubled my XC knowledge this weekend. Unfortunately you
can't get them from Ace anymore as far as I know, so scour the used market
up there. The sniffler allows you to burn down the road at 70 mph and
recognize a thermal when you hit it. It's much harder to do this by eye.
In order to use a sniffler effectively you need the following
modifications:
1. The transmitter antennas are about half as long as you need. Even if you don't have one yet build the wires into your next plane to go the ENTIRE wing span, or use that copper burglar alarm tape on the wing underside. (Messy looking but effective.)
2. Throw out the chalkboard pointer on the receiver and get a real CB antenna mounted on the chase vehicle, preferably as far away from your radio TX antenna as possible, like the front bumper.
3. Get set of real quality headphones, not the Walkman type or that horrible ear plug that comes with it.
4. Replace the switch on the Transmitter with a good one and replace the 9V plugs on both the transmitter and receive with better ones, as the wire is junk.
5. Tune it using the 3 pots on the back. Gordon says you are looking for a raspy sounding saw tooth pattern rather than a square wave pattern on the earphone. Same frequency, but a more usable type tone. Can't really say how he did this except by practice, kind of like a needle valve. With these mod's you can be absolutely skied out and still know what kind of air you are in. I seem to remember Matt having one. Play around with it and see what you can do.
One thing you will find is that experience on the road is everything in XC.
Wurts has a few thousand miles on the plane he is currently flying. Gordon
says he would go back to the E 374 for strength on his next one. He thinks
the 2048 has a problem on the top end, and nobody has any experience with
the 7012 on big planes. RG 15 is the other choice, but quite a bit thinner.
The other route you can go is the SBXC. Rich Tiltman won Saturday with a
respectable time for the conditions. There were 3 teams with them out there
and they seemed to do pretty well. One drawback of the flatter wing is less
stability at high altitude in thermals. Gordon seemed to think that this
limits your ceiling to lower than for a big poly-plane. He said you could
use just flaps for landing in small fields like the Catalina. He said the
only time he would pick an SBXC to win is in a pure L/D contest like our
rain-out day.
In order to compete with Wurts and Jennings you need the plane and guts to
go around the course never getting below 3000 ft except on the mad dash for
the finish line. I got 17 ? miles on Sunday and for half the flight I could
barely see the plane and often had no idea what it was doing. This is
really scary flying and probably twice the skill level I have seen in any
other location.
My next plane will most likely be a cleaned up version of the white plane
with spyder foam cores, E 374, carbon tips, and the same fuse with a bit
more length, less stab, and maybe 5% less fin. Let me know your progress on
the fuse. There is a guy here interested in making another mold if I can
get a hold of the plug.
The wood plane with the V-tails is being relegated to wowing the locals,
and will definitely be retired from racing.
The next XC is in June. If you can get a plane ready I would highly
recommend the trip. I find this flying much more interesting and
challenging than thermal duration.
Bagging info from Gordon:
He gets about a 60/40 glass/resin ratio by using a super low viscosity
resin made by Gougeon. The hardener is supposedly like water. Viscosity is
400 cp vs. 1000 cp for the regular West Systems. He spreads it fast and
thin and says to don't "wet" the glass with the squeegee, just push a wave
front of epoxy over the surface and let the 14 psi push it in. The
trowelling takes practice to get the touch but he claims to have a
spreadsheet which will predict a wing panel weight to within a few grams.
The next step in F3B is wing molds cut from a 3" chunk of Al using a CNC
machine. Just program the coordinates and the computer takes care of the
rest. These guys take it seriously here.
If you don't mind, please sign the CSS form and drop it in the mail. It
turns out I only needed two 30 minute flights.
Your friend,
Greg