is TE probe needed?

[JSoar]

My homebuilt self-launching sailplane is getting very close to it's
first flight. However, to make a long story short, I don't have any
good place to install a total energy probe right now. I have an old
variometer that I was planning on starting with, if it still works.
Otherwise I may need to get a new variometer for it, like the B400 or
RAS-V1000. But I see where they require a TE probe. Can these or
similar varios be used without a TE probe and still get useful
results, maybe just hook it up to the static system? Or are there some
small low cost varios that don't need a TE probe?

Thanks in advance,
Jerry Booker
www.jsoaraero.com

[[email protected]]

On Jul 13, 6:50*pm, JSoar > wrote:
> My homebuilt self-launching sailplane is getting very close to it's
> first flight. However, to make a long story short, I don't have any
> good place to install a total energy probe right now. I have an old
> variometer that I was planning on starting with, if it still works.
> Otherwise I may need to get a new variometer for it, like the B400 or
> RAS-V1000. But I see where they require a TE probe. Can these or
> similar varios be used without a TE probe and still get useful
> results, maybe just hook it up to the static system? Or are there some
> small low cost varios that don't need a TE probe?
>
> Thanks in advance,
> Jerry Bookerwww.jsoaraero.com

A good total energy system is more important than what vario you hook
it to.
You may not want to do it right now, but sooner or later you will want
to add it.
Aerodynamically the upper part of the fin seems to work best by
keeping it out of disturbed
flow.
That said, a quick and dirty solution is to mount the probe on the aft
fuselage as far back as you can reach.
Another alternative is buying a vario with electronic compensation.
The down side of this is that you need a pretty good static system to
avoid creating more probelms than you solve.
Good luck and keep us posted.
UH

[Eric Greenwell]

JSoar wrote:
> My homebuilt self-launching sailplane is getting very close to it's
> first flight. However, to make a long story short, I don't have any
> good place to install a total energy probe right now. I have an old
> variometer that I was planning on starting with, if it still works.
> Otherwise I may need to get a new variometer for it, like the B400 or
> RAS-V1000. But I see where they require a TE probe. Can these or
> similar varios be used without a TE probe and still get useful
> results, maybe just hook it up to the static system?

What speeds do you expect to fly at? The slower you go, the less TE
helps. If your gliding speed range is, say 30 to 50 knots, I say start
off with just the static connection.

You could easily mount a TE in the nose; the drawback is it's more
susceptible to ground damage. A TE probe in the tail is badly affected
by the propeller blast, and can be almost worthless when the engine is
running. Some pilots switch it to static, even cabin static, during the
engine run.

> Or are there some
> small low cost varios that don't need a TE probe?

Small, yes, low cost, no. Electronic TE using the pitot and static
require a vario with a pitot input, and the cheap ones don't have it.
You might find what you want by looking at hang glider varios. Their
speed range is probably close to what I'm guessing the Red Tail will be
flying, and their stuff seems to be much cheaper than sailplane instruments.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Heinz]

Some years ago I build a TE-Probe per Dick Johson for our club's
1-26D. See http://www.postfrontal.com/PDF/PW5_TE.pdf. or search the
SSA site for how to. The whole project cost me a couple of bucks and
took about 1 hr to do.
I mounted the probe just behind the removable turtle-deck
(accessibility issue). I used a phenolic block with a hole for the
probe so that I could raise or lower it to find the "out-of-boundary-
layer" position. about 6-7" did the trick.
And the results were great. Thermal-flying was much eased.
Heinz

..
On Jul 13, 3:50*pm, JSoar > wrote:
> My homebuilt self-launching sailplane is getting very close to it's
> first flight. However, to make a long story short, I don't have any
> good place to install a total energy probe right now. I have an old
> variometer that I was planning on starting with, if it still works.
> Otherwise I may need to get a new variometer for it, like the B400 or
> RAS-V1000. But I see where they require a TE probe. Can these or
> similar varios be used without a TE probe and still get useful
> results, maybe just hook it up to the static system? Or are there some
> small low cost varios that don't need a TE probe?
>
> Thanks in advance,
> Jerry Bookerwww.jsoaraero.com

[Dave Martin[_3_]]

If you can get hold of a QWEK converter this should do the job.

The converter is a diaphram inside a capsule that is plumbed into the
vario/asi circuit. Many Polish gliders are fitted with them as standard,
so you may find someone who has one lying around.

They are simple to fit and provided you get them in the right place in the
plumbing work OK. It also requires one per instrument and is G sensitive to
so should be mounted vertically.

Some fin tubes instead of being the conventional fin probe use a venturi
on a probe that could be nose mounted, but again these have their faults

The converter takes a feed from the pitot pressure before it gets to the
ASI, then T's into the vario circuit between the bottle and the
instrument. There must be someone in the US with one lying around. They
just need to be checked to ensure the diaphram has not perished.

Dave

At 02:39 14 July 2009, Eric Greenwell wrote:
>JSoar wrote:
>> My homebuilt self-launching sailplane is getting very close to it's
>> first flight. However, to make a long story short, I don't have any
>> good place to install a total energy probe right now. I have an old
>> variometer that I was planning on starting with, if it still works.
>> Otherwise I may need to get a new variometer for it, like the B400 or
>> RAS-V1000. But I see where they require a TE probe. Can these or
>> similar varios be used without a TE probe and still get useful
>> results, maybe just hook it up to the static system?
>
>What speeds do you expect to fly at? The slower you go, the less TE
>helps. If your gliding speed range is, say 30 to 50 knots, I say start
>off with just the static connection.
>
>You could easily mount a TE in the nose; the drawback is it's more
>susceptible to ground damage. A TE probe in the tail is badly affected
>by the propeller blast, and can be almost worthless when the engine is
>running. Some pilots switch it to static, even cabin static, during the
>engine run.
>
>> Or are there some
>> small low cost varios that don't need a TE probe?
>
>Small, yes, low cost, no. Electronic TE using the pitot and static
>require a vario with a pitot input, and the cheap ones don't have it.
>You might find what you want by looking at hang glider varios. Their
>speed range is probably close to what I'm guessing the Red Tail will be

>flying, and their stuff seems to be much cheaper than sailplane
>instruments.
>
>--
>Eric Greenwell - Washington State, USA
>* Change "netto" to "net" to email me directly
>
>* "Transponders in Sailplanes" http://tinyurl.com/y739x4
> * Sections on Mode S, TPAS, ADS-B, Flarm, more
>
>* "A Guide to Self-launching Sailplane Operation" at
www.motorglider.org
>

[Ron Gleason]

One alternative may be a f