Blow holes vs turbulaator tape.

One would think if the blow holes did not add much a pencil pusher at the factory would realize they could have lots of man hours ($) by just using dimple tape.

On Monday, October 24, 2016 at 11:30:06 AM UTC-7, soarin wrote:
At 16:50 24 October 2016, Jim White wrote:
Herr Waibel has been quoted as saying of the ASW27 that "there is a 50/5
chance that the blow holes improve performance by 1/2 point". Possibl
apocryphal. Easy to clean with a piece of copper wire and a vacuum cleane
but tedious beyond belief. jim

I once got a DG300 in for insp and found that the blow holes on one wing
were inop (apparently the seal of the internal blow hole channel had
failed). The factory said a fix was problematic and to go ahead and
install dimple tape as it works just as well. No telling how many years
the glider flew with one wing turbulated and the other not. The owner was
oblivious to any degradation in handling or performance before and after
installing the dimple tape.

ME

On Monday, October 24, 2016 at 1:49:18 PM UTC-5, Jonathan St. Cloud wrote:
One would think if the blow holes did not add much a pencil pusher at the factory would realize they could have lots of man hours ($) by just using dimple tape.

Another claimed, but I don't know if it was ever proven, benefit of the blow holes is that even if they are behind the leading edge of the laminar bubble, they can still "blow out far enough to burst the bubble and get the advantage of not having the high drag, laminar bubble" whereas, turbulator tape inside the bubble does nothing at all for you.

It is all about how much are you willing to do to get that last half percent.

On Monday, October 24, 2016 at 10:14:25 PM UTC+3, Steve Leonard wrote:
On Monday, October 24, 2016 at 1:49:18 PM UTC-5, Jonathan St. Cloud wrote:
One would think if the blow holes did not add much a pencil pusher at the factory would realize they could have lots of man hours ($) by just using dimple tape.

Another claimed, but I don't know if it was ever proven, benefit of the blow holes is that even if they are behind the leading edge of the laminar bubble, they can still "blow out far enough to burst the bubble and get the advantage of not having the high drag, laminar bubble" whereas, turbulator tape inside the bubble does nothing at all for you.

It is all about how much are you willing to do to get that last half percent.

Half a percent? One minute on a three hour race? Plenty are won and lost by less than that.

It won't make any meaningful difference to whether you can stay up, or even whether you can complete a task.

On Monday, October 24, 2016 at 3:14:25 PM UTC-4, Steve Leonard wrote:
On Monday, October 24, 2016 at 1:49:18 PM UTC-5, Jonathan St. Cloud wrote:
One would think if the blow holes did not add much a pencil pusher at the factory would realize they could have lots of man hours ($) by just using dimple tape.

Another claimed, but I don't know if it was ever proven, benefit of the blow holes is that even if they are behind the leading edge of the laminar bubble, they can still "blow out far enough to burst the bubble and get the advantage of not having the high drag, laminar bubble" whereas, turbulator tape inside the bubble does nothing at all for you.

It is all about how much are you willing to do to get that last half percent.

If the airfoil is designed to use blowing, the gains may well be more than that.
Listen to the noise on a '27 when in the wrong flap position and you know
something is going on.
UH

Thanks Steve, I do remember now reading about that. Makes sitting down with a tiny drill bit and a six pack seem worth it.

On Monday, October 24, 2016 at 12:14:25 PM UTC-7, Steve Leonard wrote:
On Monday, October 24, 2016 at 1:49:18 PM UTC-5, Jonathan St. Cloud wrote:
One would think if the blow holes did not add much a pencil pusher at the factory would realize they could have lots of man hours ($) by just using dimple tape.

Another claimed, but I don't know if it was ever proven, benefit of the blow holes is that even if they are behind the leading edge of the laminar bubble, they can still "blow out far enough to burst the bubble and get the advantage of not having the high drag, laminar bubble" whereas, turbulator tape inside the bubble does nothing at all for you.

It is all about how much are you willing to do to get that last half percent.

On Monday, October 24, 2016 at 2:16:19 PM UTC-6, Jonathan St. Cloud wrote:
Thanks Steve, I do remember now reading about that. Makes sitting down with a tiny drill bit and a six pack seem worth it.

On Monday, October 24, 2016 at 12:14:25 PM UTC-7, Steve Leonard wrote:
On Monday, October 24, 2016 at 1:49:18 PM UTC-5, Jonathan St. Cloud wrote:
One would think if the blow holes did not add much a pencil pusher at the factory would realize they could have lots of man hours ($) by just using dimple tape.

Another claimed, but I don't know if it was ever proven, benefit of the blow holes is that even if they are behind the leading edge of the laminar bubble, they can still "blow out far enough to burst the bubble and get the advantage of not having the high drag, laminar bubble" whereas, turbulator tape inside the bubble does nothing at all for you.

It is all about how much are you willing to do to get that last half percent.

I get these on Ebay. Works good on my 29. I find that inflight dust and bugs do get in and I do clean them several times a year. If you drop them, they do break rather easily.

..024" 0.60mm #73 - Five Carbide Drill Bits -

Best. Tom #711.

Jonathan St. Cloud wrote on 10/24/2016 11:49 AM:
One would think if the blow holes did not add much a pencil pusher at
the factory would realize they could have lots of man hours ($) by
just using dimple tape.

Schleicher has used blow holes from at least 1984 on the ASW20C and B.
The holes were thin metal tubes on the wing bottom, and looked like they
might be costly. My ASH 26 E does not use the tubes on the wings;
instead, the blow holes are drilled into the the bottom of the flaps and
ailerons. That's not on the wing, but on the control surface!

My guess is the boundary layer is too thick on the control surfaces for
zig zag tape to work, unless it was stacked two or three high.

Drilled holes are probably cheap enough, and installing the tiny NACA
scoops is easy, too.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

On Wednesday, 26 October 2016 03:26:21 UTC+3, Eric Greenwell wrote:
My guess is the boundary layer is too thick on the control surfaces for
zig zag tape to work, unless it was stacked two or three high.


If the function of blowholes is to trip laminar flow into turbulent, how can laminar flow be "thick"?

krasw wrote on 10/26/2016 12:33 AM:
On Wednesday, 26 October 2016 03:26:21 UTC+3, Eric Greenwell wrote:
My guess is the boundary layer is too thick on the control surfaces for
zig zag tape to work, unless it was stacked two or three high.


If the function of blowholes is to trip laminar flow into turbulent, how can laminar flow be "thick"?

I'm not sure what you are asking, but in general, laminar flow has a
thicker boundary layer than turbulent flow, and when it grows too thick,
it separates from the airfoil into a "laminar separation bubble" that is
high drag. The cure is to trip the laminar flow into turbulent flow,
which "sticks" better to the airflow.

Schleicher uses two layers of zig-zag tape just in front of the NACA
inlets that pressurize the control surface blowholes. A single layer is
not thick enough to trip the laminar flow that far back on the airfoil.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "A Guide to Self-Launching Sailplane Operation"

https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

i'll tell you everything i know based on my time with eta-biter, concordia, and talking to butler.

The blow holes on eta biter are driven by a naca duct. the naca duct has been modified to be closed via a switch in the cockpit that drives a servo. at a certain airspeed, the blowing is swithced of and the boundry layer is turbulated further back by....zig sag tape. there is a presentation by butler about this "blowing articulation" out there on the web. Due to manufacturing and maintainance complexity, concordia doesn't have blowholes. neither does the V3. that's kinda a schleicher thing.

When we refinished my 20C two years ago, the question was this: can we fill in the blowholes, and just put zig zag over the blow-hole location? the idea was to reduce the maintainance/not worry about filling them with wax/ no cracking of the paint over the longer term.
we wanted to make sure that the turbulator tape would provide the same benefits though, and not actually harm the performance. butler and waibel both said zig zig in the same location would offer the same performance benefits..

I personally wanted to keep the blowholes, and fantazised about installing blowhole articulation for a club class ringer. I was outvoted though, so we did zig zag tape. the glider flies really well. Ask erik nelson and his V2XA...

On Sunday, October 23, 2016 at 7:54:27 PM UTC-4, Jonathan St. Cloud wrote:
Just curious if there is research that compares blow holes versus tabulator tape as to effectiveness and drag? i.e., are the bow holes worth the maintenance or is tape effectively just as good? Does the new Ventus have tape or blow holes?