Themi review
John Morgan
I heard about the THEMI (Thermal Maneuvering Indicator) over a year ago when
it was mentioned here. There was no review,
just
comments about how it worked - - or maybe didn't. No other
word until about two months ago when Tom Knauff (Knauff and Grove
Soaring Supplies) did a short post and invited people to download the
Themi manual in .pdf file from his website.
http://www.eglider.org/instr1.html
I read the manual but still wanted more in the way of unbiased
review - - there's not a lot out there. The Themi might be the best kept
secret in soaring, or maybe people are so embarrassed about wasting their
money on one that they won't admit they have one? Or could it be they want
to keep it a secret so they can out-thermal the competition?
I decided the only way I was going to sort it out was to buy one. This
decision
was made easier when Tom Knauff said I could get my money back if I
wasn't satisfied. No problem, I'll be keeping the Themi, thank you!
My review follows a brief technical description, some of
which is not in the Themi manual.
The Themi combines a GPS, solid state vario and microprocessor all housed in
a single black box measuring 5.5 X 3 X 2 inches and weighing 12 ounces. The
box is metal but sealed in heat shrink with a manufacture's seal to prevent
tampering. Otherwise I'd have had a look in the box too. Power required is
12 volts at .137 amps (137 milliamps) average - I used an meter with
averager over a 5 minute period.
The few necessary wiring connections are made through a single DB-29 style
plug at one end of the box. There are wires for
ground and positive 12 volts (with pre-installed, in-line toggle switch), a
GPS antenna, a DB-9 plug for downloading or uploading data, and a wire for
the display LEDs. No soldering required. The power wires are pre-terminated
with narrow style female spade lugs. Since my ship uses the more common
wider spade
lugs, I had to replace the lugs. Themi should consider including both types.
I also wanted the indicator LEDs mounted a bit further apart than the 2 1/2
inches the wiring harness allows. To do this I cut back the sheathing on the
single multi conductor wire to allow the individual wires to be spread
apart, then re-insulated the wire. Themi may consider the 2 1/2 inch
distance optimal for viewing, but in my installation I wanted the LEDs on
either side and above a 3 1/8" instrument.
The package looks first rate, well put together. However, there are no
mounting tabs or holes for screw mounting the main box so I mounted the box
with self adhesive Velcro. The box might also be mounted using large nylon
ties. Other than that, installation is straightforward for the panel mount
version (there's a portable version that's even quicker). Drill 3 quarter
inch holes, two for
the indicator LEDs and one for the power switch. Mount the box and GPS
antenna, hook up power and ground and you're done.
I did some additional tests to see if there might be any electrical
interference, from the Themi, on comm or existing GPS. I didn't detect any,
even when placing the Themi antenna right next to the existing GPS antenna.
Still, as the installation manual suggests, I separated the two GPS antennas
by a few inches.
The Themi won't help you find thermals. It will help you center them quickly
and will continue to assist in keeping you centered in the strongest lift.
It does this in an unobtrusive manner using 2 bright LEDs. The LEDs should
be mounted high on the instrument panel so you can keep your eyes outside
the cockpit and still see them with peripheral vision. Although the LEDs are
bright, mounting them under the glare shield will make them more noticeable
in bright sunlight.
The net effect is that the Themi
reduces work load and concentration required to maximize climb rate. Since
I'm one of those pilots who ends up circling in solid sink if I but reach
for a Power Bar, the Themi provides welcome assistance. If I'm reasonably
well centered the Themi LEDs remain off. But if I stray from the strongest
lift, the Themi will be on top of it with one LED on
steady (if the thermal center is ahead and off to one side) suggesting I
shallow the bank until the light goes back off (telling me the thermal
center is abeam), then tighten up the bank again. Vario needle swings upward
confirming the Themi is no dummy.
On one flight I'd been circling in a thermal for a few minutes when both
LEDs came on. This means the thermal center is almost straight ahead . . .
I thought how could this be? No matter, I leveled the wings to see what
would happen. Moments later I was rewarded by the familiar push on the
rump - amazing!
On another flight I was circling with a young golden eagle over Lake
Berryessa, northern California. As the eagle shifted his circles and then
moved away from me, I followed his lead. And with each change, I noticed the
Themi was basically pointing towards the eagle! In my mind this offers
conclusive prove that all eagles are equipped with Themi's.
The Themi remembers what it previously learned about a thermal. If you are
in a "compound thermal" and move from circling one center to another nearby,
the Themi will seamlessly switch over to what it considers the new thermal
center. If you leave a thermal and come back to the same thermal later on,
it
switches back to the old thermal as you approach. I don't know how large
it's "database" is, but I imagine it remembers all the thermals in a flight
as it is also a logger, though not yet approved. Note it won't "navigate" or
provide guidance back to a previous thermal, but the LEDs give thermal
center advice as you approach, even before you encounter lift.
Yup, the Themi may have a tough time overcoming the "training wheels
mentality" of some glider pilots. "A real pilot doesn't need that! I'd be
embarrassed to have it in my glider." But that same pilot probably uses a
GPS and maybe a soaring computer. I consider the Themi as just another tool,
not
a crutch. It's a friend offering advise and helping out. Trouble is the damn
thing seems to be right more than me - - it's embarrassing.
Tom Knauff is the US dealer for the Themi and tells a story about when the
Themi
developer left one with him. At first he used it mainly to see how good it
was (whether it agreed with his centering). After a while he decided to
blindly follow the Themi to "give it a real chance" and was surprised that,
in certain conditions (esp blue thermal days or low to the ground --
basically where cloud clues are not present), it did much better than him.
He said that now, when low to the ground, he follows the Themi instead of
his own instincts, and does better.
--
bumper <flybu...@att.net>
remove aviation to reply
F.de Klerk
I bought the Themi about a year ago. I am from South Africa. I
have found it a very useful tool. It seems to be at its most useful when you
are low and when the thermals are blue. Many times in these situations it
has told me to do the direct opposite to what my instincts were and BANG
into the centre of a thermal. It becomes even more unbeatable when you have
a strong wind. It has the ability to track the thermal very well in these
conditions. When you have a normal strong day with clouds then there are
other visual signs to follow and I then use it only to direct me the
strongest part of the lift under the cloud once I have found the
lift.Overall I found the Themi worth it, and it has saved me quite a few out
landings.
Regards
Francois
"John Morgan" <flybu...@worldnet.att.net> wrote in message
news:jA0H7.164122$3d2.6...@bgtnsc06-news.ops.worldnet.att.net...
Martin
"John Morgan" <flybu...@worldnet.att.net> wrote in message
news:jA0H7.164122$3d2.6...@bgtnsc06-news.ops.worldnet.att.net...
>
> Yup, the Themi may have a tough time overcoming the "training wheels
> mentality" of some glider pilots. "A real pilot doesn't need that! I'd be
> embarrassed to have it in my glider." But that same pilot probably uses a
> GPS and maybe a soaring computer. I consider the Themi as just another
tool,
> not
> a crutch. It's a friend offering advise and helping out. Trouble is the
damn
> thing seems to be right more than me - - it's embarrassing.
>
>
I like your review. Thanks for sharing your experiences. I am not surprised
by your conclusions, the Themi is not unique. Peter Zander and some of his
competitors added a similar feature to the soaring computer. I use this
feature frequently and it seems to give the right advice most of the times.
It is just plain stupid to think that you don't need it. Thermalling aid
will give you more time to watch other gliders, look at the map, eat, drink,
pee, observe the weather, etc.
You have to keep in mind that thermals can be unpredictable and have
multiple cores. Some day you just have to trust your butt and turn the
thermalling aid off.
Martin
John Morgan
"Martin" <remove_no_...@hotmail.com> wrote in message
news:SAOH7.15$K6.1182@client...
Thank you for the feedback. I also appreciate the informative post by
Francois de Klerk. I know there are a lot more Themi owners out there . . .
and I have to admit that I was hoping there would be more response to my
review. BTW I have no financial interest or connections to Themi.
I should say that parts of my original post were somewhat tongue-in-cheek,
an attempt at humor and to keep it "light reading". Honest, most of the time
I don't really fall out of a thermal at the slightest provocation. Nor do I
blindly follow the Themi. The Themi's LED indicator lights are easy to
ignore when not needed. I believe they are intended to be that way. In fact
the Themi manual says:
"REMINDER Fly as you are used to fly. Watch the airspace! Look at the sky
and the ground for thermal activities. 'Feel' your glider's reactions to the
air. Check the signals of THEMI if you are not sure what to do. Do not fall
into the habit of waiting for the signal lights to give you advice.
In different weather situations you will have different experiences. If you
are in doubt about the signals, please read chapter 3 'Signal Lights' again.
. . ."
The real beauty of the Themi, besides the fact that it truly works well
under many soaring conditions, is in the simplicity of the pilot interface.
Unlike a moving map or GPS, it requires *no* distraction from looking
outside the glider.
Just for info, I fly some cross country, but no contests or badges. I have
almost 400 hours glider since converting from power in '98 (2,500 hours
total since '91). I started late, at age 46, so I'm trying to make up for
lost time.
Bob Stern
maximizer function would be kind of toy. I love it now. I think it works
pretty much like the Themi.It uses a gps souce and input from my Borgelt
B50. It seem to work best with small odd thermals. I have just lost a
thermal completely and have the climb maximizer point in a direction and
sure enough I'm back in the small thermal again.
There seems to be advantages to both interfaces. I like the graphical nature
of winpilot. I can glance down and see the arrow and move my circle that
way. By the length of the arrow I am also given an indication of how far to
move. I can understand how the Themi's LED's can be a little less effort to
see but, I think it does not give quite as much information.
Bob
PIK-20D "68"
"Martin" <remove_no_...@hotmail.com> wrote in message
news:SAOH7.15$K6.1182@client...
>
Thomas Knauff
"Bob Stern" <rjs...@telocity.com> wrote in message
news:dSXI7.153$rU1.3...@newsrump.sjc.telocity.net...
. . . . . "I can understand how the Themi's LED's can be a little less
effort to
> see . . . . "
Themi does not require the pilot to ever "look" at the two bright LED
lights. They are almost always in your field of vision (often perepherally)
and are very noticeable no matter where you are looking. This is a better
solution than a screen you must look at, especially when thermalling with
others. In most conditions, the lights are additional information to the
audio variometer for the pilot. In some conditions, Themi becomes the
primary information to center in a thermal.
--
Thomas Knauff
Knauff & Grove Soaring Supplies
3523 South Eagle Valley Road
Julian, Pa 16844
(814) 355 2483
Fax (814) 355 2633
Email: tkn...@earthlink.net
www.eglider.org
Ruud
The Zander SR940 also has a centering aid that I find very useful when
you're getting a bit tired after a long flight.
This is all done by sound signals, so there's no need to look at any
instrument. See #17 at http://home.wxs.nl/~kpt9/FAQPZ.htm
Ruud.
On Fri, 16 Nov 2001 14:04:10 GMT, "Thomas Knauff" <kna...@eglider.org>
wrote: