Thanks, Anthony.
I think that must be the paper that Lange used to fit the Antares
with a larger fin leading edge to fuselage fillet. This prevented the
formation of a vortex either side of the fin and rudder.
Buying an ASG-29 just gives you a much more expensive glider to start
improving, but it is nice to see that money is no object. :-)
It is doubtful anyway that a nice Ventus A/Ca with winglets is any
worse than a ASW-27 (or ASG29 in 15M), as Gary Ittner proved for years.
There is a lot of satisfaction to be had investigating your glider's
aerodynamics and fixing the little things. Besides it sows seeds of
doubt in your competitors' minds as they suspect they are flying
gliders that are just a little worse than yours.
BTW Dick Johnson didn't use any really fancy equipment for his
testing. He had a vibrator device to remove any stiction from the
altimeter and ASI and a stopwatch. Nowadays there are better methods.
You need to be careful with the drag rake device as if the pitot and
rake sides of the ASI you use aren't balanced the reading will depend
on the rate of climb or descent. This can be overcome by balancing.
The USAF Test pilot School simply sticks the fuselage in a pressure
chamber to balance the pitot/ static.
If you modify the rake to have two lines to it and extend it
vertically so that you get a pitot source in free air above and
below, you can balance the lines, ASI and rake out of the glider. Try
finding a lift in a multistory building or a reasonable size chamber.
you don't need
much pressure change, just a good rate of change. If you want an
electronic signal find an old later model B-24 unit. The electronic
ASI was very accurate and stable as it had an auto zero feature. We
once built an ASI for the old CAA for flight testing based on one of
these. When tested by a NATA lab they found it was within 0.25 knots
from 10 to 160 knots.
Mike
At 07:37 PM 10/03/2015, you wrote:
Content-Type: multipart/alternative;
boundary="----=_NextPart_000_000F_01D05B6D.D7FB5500"
Content-Language: en-au
Something that may help Adam more for LE fairings is this:
<http://www.icas.org/ICAS_ARCHIVE/ICAS2002/PAPERS/294.PDF>http://www.icas.org/ICAS_ARCHIVE/ICAS2002/PAPERS/294.PDF
From: [email protected]
[mailto:[email protected]] On Behalf Of Mike Borgelt
Sent: Tuesday, 10 March 2015 5:15 PM
To: Discussion of issues relating to Soaring in Australia.
Subject: Re: [Aus-soaring] Wool tuft testing
Take a look at the root fairings on the P-38
<http://www.gayot.com/blog/wp-content/uploads/2009/04/lockheed-p-38-lightning.jpg>http://www.gayot.com/blog/wp-content/uploads/2009/04/lockheed-p-38-lightning.jpg
Note the fairing is at the leading edge. Particularly noticeable on
the wing to fuselage but also on the wing to booms.
No fairing or fillet at the TE. Fixed an airflow problem
apparently. A more blended wing/body junction may have some merit.
Mike
At 01:54 PM 10/03/2015, you wrote:
G'day Anthony,
Thanks for your detailed reply, lots to think about & plan for. I'm
going to wool tuft test the wing root of my Ventus, as I want to
improve on the lamina flow & induced drag in that area, which
ultimately will help with climbing & handling.
Once I discover the separation points, I plan to 'fix it'..
Guessing I'll need to view the tufts at thermalling speeds/bank, &
at my usual cruise speeds.
Cheers,
WPP
> On 9 Mar 2015, at 18:38, Anthony Smith
<<mailto:[email protected]>[email protected]> wrote:
>
> Adam
>
> I have done it on the wing tip of a large military aircraft.
>
> Wing loading is only a problem if you have a particular issue that is wing
> loading related. In essence what are you looking for? Is it Reynolds
> Number related or is it Angle of Attack related? Or both?
>
> Wool lengths need to be visible to the camera or observer. For my project
> we had a PC-9 as a chase plane with a photographer and video camera in the
> back seat. So we had really big tufts. For your purpose, quite fine wool
> may work depending on how you plan to record the results.
>
> You do not want the tufts to overlap. Typical patterns have the
end of each
> tuft, a small gap and then the start of the tape adhering the next tuft.
> Lateral spacing is the same.
>
> Wool thickness will depend on what speed you are operating at. Also will
> depend on how visible you want it. I used the thickest wool we could find
> in order to be visible to the camera. Also we were operating at
much higher
> speeds than your average glider. You will not need to be that thick. Some
> simple experimenting with a range of wool sizes stuck to the wing root may
> give you an answer.
>
> How many tufts will depend on the length of the wool tuft.
>
> For my project, we adopted a diamond pattern. This aligned
really well with
> some features on the wingtip that we wanted to study. The size of the
> diamond was dictated by the length of the tuft and the features on the
> wingtip. A square pattern may work better for your problem.
>
> Installation: You need to tie a knot in both ends of the wool tuft. The
> knot under the tape helps to hold the tuft in place. The knot in the free
> end stops the wool unravelling. A simple knot will do. Don't get carried
> away or the mass of the knot will affect the results. A dob of super glue
> on the free end may also work just as well. We used triangular pieces of
> fabric reinforced tape (instant airframe) to secure each tuft in place. We
> had the point of the triangle faving forwards. Wing gap tape with a good
> adhesive may suit you better.
>
> Some experimentation may be required. However if you start off
with typical
> yaw string lengths you will not be far long. You can also space them out a
> bit initially (say at twice the tuft length) and then increase the density
> as you need to and where you need it.
>
> There appear to be plenty of photos if you google 'flow
visualization tuft'.
>
> Anthony
>
>
> -----Original Message-----
> From:
<mailto:[email protected]>[email protected]
> [ mailto:[email protected]] On Behalf Of Adam
> Woolley
> Sent: Monday, 9 March 2015 6:32 PM
> To: Discussion of issues relating to Soaring in Australia.
> Subject: [Aus-soaring] Wool tuft testing
>
> G'day all,
>
> Has anyone got any experience or thoughts on wool tuft testing a
wing root?
>
> Does wing loading matter?
> What wool lengths & thickness is best?
> How many?
> What pattern?
>
>
> Cheers,
> WPP
>
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Borgelt Instruments - design & manufacture of quality soaring
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instrumentation since 1978
www.borgeltinstruments.com
tel: 07 4635 5784 overseas: int+61-7-4635 5784
mob: 042835 5784 : int+61-42835 5784
P O Box 4607, Toowoomba East, QLD 4350, Australia
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