Thread Tools
This thread is privately moderated by maguro, who may elect to delete unwanted replies.
Apr 24, 2019, 05:24 AM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
Guys , if you have the time , we’ve been using Glidden Gripper to laminate the KF strip(s) to my wings …. lightly coat both sides , let sit a few minutes , then stick it together ( Newton clamp) and wait a week for it to cure … Very strong !!! The trick is to make several wings in advance … ( planning ! )
Latest blog entry: Lost plans
Sign up now
to remove ads between posts
Apr 24, 2019, 06:37 AM
Jack
jackerbes's Avatar
Have not tried the new clear glue yet but the classic old brown and the newer opaque quick glue work fine as you describe:

https://www.gorillatough.com/products/#filter=.glue

And for hot glue the Arrow slow setting for woodworking is my choice, not the cheap Chinese sticks:

https://www.lowes.com/pd/Arrow-24-Pa...Sticks/1043701

Look at the build images on my blog page and you'll see both of those in use. The hot glue is the ticket for gluing tape covered parts together, like a vstab onto a hstab...

And the tape is the 2 mil or 2.2 mil or so colored package sealing tape applied directly to the plastic membrane side of FFF or applied as you describe above with water and glue to the bare foam side of FFF.

Jack
Last edited by jackerbes; Jun 05, 2019 at 12:53 PM.
May 01, 2019, 09:24 PM
Registered User
Dickeroo's Avatar
Thought the KFers might find this document interesting. Employing the KF vortex concept to a Darrieus Wind Turbine, it produced a 13% improvement over the conventional airfoil in the post stall phase. This paper was just published. I think it’s on page 35 under 2.8. Innovative Darrieus Turbines.

2.8. Innovative Darrieus Turbines
The continuous research on the Darrieus turbine has yielded many innovative designs, yet a very few concepts have the potential to be scaled up for commercial purpose. These turbines are optimized for low wind speed and are economical. An airfoil that is capable of maintaining the lift over high AoA without significant increase in drag will be an apt choice for Darrieus turbines. Airfoils are modified such as trailing edge cavity modification [64] was found to enhance energy yield. Kline (KF) conceived airfoils with abrupt discontinuity claiming to have enhanced lift. Though the airfoil doesn’t outperform in the pre-stall region, it demands attention for its aerodynamic behaviours in the post-stall region when the step is located on the suction side of the airfoil as reported by Mishriky. The new airfoil KF-N-21 was created by introducing the step discontinuity borrowed from the KF airfoil on the suction side of the NACA 0021 airfoil. In order to create maximum drag during the reverse flow to aid in the startup, the depth of step is located at 18%c, while the maximum thickness of airfoil is 21%c. The step length is 50%c and originates at 30%c from the leading edge, though location near to the trailing edge is favourable for high lift coefficient. The experimental comparison with conventional turbines reveals that the turbine Cp has been increased by 13% at low Re.
Last edited by Dickeroo; May 02, 2019 at 04:38 PM.
May 02, 2019, 07:37 AM
He who stalls....falls!
Quote:
Originally Posted by Dickeroo
Thought the KFers might find this document interesting. Employing the KF vortex concept to a Darrieus Wind Turbine, it produced a 13% improvement over the conventional airfoil in the post stall phase. This paper was just published. I think it’s on page 35 under 2.8. Innovative Darrieus Turbines.
Very interesting.
Would imagine some serious testing happened .
If one industry is taking a look, what others will follow.

Just a thought (probably already mentioned somewhere here), if the KF works well as a "driven" force,
ie- our wings and turbines driven by airspeed, does it also work as a "driving" force? ie- impellor blades,
auto-gyro blades etc.
As I said probably covered, only reading a few pages at a time, the whole concept and history of KF to me
is nothing short of fascinating.
Anyhow, time to get back to depron cutting, and a rest from thinking too hard.
cheers
May 02, 2019, 11:56 AM
Thermite + ice = Big boom.
boaterguy's Avatar
That would be interesting for multirotor propellers, which I imagine are at stall speeds very frequently. a KF lip might show some performance increase in the low end.
Jun 04, 2019, 11:41 AM
Registered User
Dickeroo's Avatar

Very interesting paper on trapping a Vortex in various ways.


This paper is from January 2019.

PASSIVE FLOW CONTROL OF ROTARY-WING AND FIXED- WING AIRCRAFT AIRFOILS VIA SURFACE-BASED TRAPPED VORTEX GENERATORS
By
Khider J. Al-Jaburi M.Sc. Aeronautical Engineering

https://curve.carleton.ca/system/fil...dfixedwing.pdf
Jun 04, 2019, 05:05 PM
Arizona Rim Country
GPW .... Which Glidden Gripper ? $50 a gallon or $20 a gallon
Jun 05, 2019, 05:10 AM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
The $20 one …
Latest blog entry: Lost plans
Jun 06, 2019, 02:13 PM
Thermite + ice = Big boom.
boaterguy's Avatar
Quote:
Originally Posted by Dickeroo
This paper is from January 2019.

PASSIVE FLOW CONTROL OF ROTARY-WING AND FIXED- WING AIRCRAFT AIRFOILS VIA SURFACE-BASED TRAPPED VORTEX GENERATORS
By
Khider J. Al-Jaburi M.Sc. Aeronautical Engineering

https://curve.carleton.ca/system/fil...dfixedwing.pdf
My alma-mater!

Why do they have to have so many words though? I just look at the pictures
Jun 11, 2019, 01:46 PM
Pile-it
Alien_Tech's Avatar
Quote:
Originally Posted by Jim Petro
Some other ideas to consider;
The Prandtl wing is very interesting but the basic design parts have been hidden (at least I can't find them) so we can duplicate and then start offing modifications. The KF construction should be a fast and easy way to play with the Prandtl build.
Coring holes in the interior layers of a KF construction would reduce the weight.
Using a thin CF or filament strapping tape under the top and on top of the bottom pieces of the KF "sandwich" would add stiffness.
Would a heat gun or heat lamp allow the hot glue to remain workable with a spatula to spread it thinner?
If the above techniques were used with thinner core pieces, then a multi-layer construction would more closely match conventional airfoil shape but still have the signature KF terraces.
Always remove un-needed weight and add strength only where it is needed...........something I heard in aero engineering over 60 years ago.
Nothing is hidden, what would you like to know?

https://www.amaflightschool.org/PRANDTL
http://www.nestofdragons.net/weird-a...andtl-project/
Jun 27, 2019, 10:40 AM
Registered User
Dickeroo's Avatar
A very interesting paper in the Journal of Applied Fluid Mechanics.
The KFm4 performed very well.

CONCLUSION
In this work, the energy extraction performance of a flapping foil device with a combined foil shape was investigated. The 2D unsteady and incompressible Navier-Stokes equations governing the flow over the foil undergoing prescribed heaving and pitching motions at low Reynolds number (Re = 10 000) were solved by a finite volume method, using the software ANSYS Fluent 16. The considered foil was designed by combining a NACA0012 leading edge and a NACA006 trailing edge. Then, the NACA0006 and NACA0012 were used as baseline foils. For this work, a validation study was carried out, and the results were in good agreement with the published data. Thus, the main results obtained in this study are summarized below:
1) The use of the combined foil improves the energy extraction performances.
2) The connecting area between the leading edge and the trailing edge (Xs/c) has a significant effect on the energy extraction performance. Indeed, the best performance was observed at Xs/c = 0.5, where the energy extraction efficiency was improved by 30.60% and 17.32% in comparison to NACA0006 and NACA0012, respectively.
3) For the kinematic parameters considered in this study, it is also observed that the combined flapping foil extracts the energy mainly by the heaving motion, while the contribution of the pitching motion is negative.
4) Moreover, the flow fields over a flapping cycle show that the vortex and the pressure distribution near the trailing edge of the combined foil are changed. This is due to the stepped surface of the foil. Consequently, the lift force and the moment coefficient are enhanced, thus, the energy extraction performance is improved.
Accordingly, the combined foil shape may provide an effective means to improve the energy extraction performance.
Last edited by Dickeroo; Jun 27, 2019 at 03:58 PM.
Jun 27, 2019, 04:44 PM
Build straight - Fly twisty
Whiskers's Avatar
Well there ya go. They say that the best results were obtained with the step at 50% cord position.
Jun 28, 2019, 07:16 AM
Jack
jackerbes's Avatar
Yep, and that has always been our "learned the hard way" recommendation here for steps top and bottom or single step top or bottom only wings.

So many big words and complicated math though! That dilutes the fun, just build it and fly is my recommendation!

Jack
Last edited by jackerbes; Jun 29, 2019 at 06:11 AM.
Jun 28, 2019, 11:37 AM
flyin' fool
goldguy's Avatar
Right! Too much talk and not enough action.
Jun 28, 2019, 12:24 PM
OpenTX University Staff
maguro's Avatar
Thread OP
I enjoy building and flying as much as the next person, but I also have a deep seated desire to know why and how these airfoils work. That is why I created this thread. To date a lot of interesting information has been brought forth. I hope it continues.

Thanks Dick.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion ** Kline-Fogleman (KFm) Airfoils - Building/Flying Discussion ** jackerbes Foamies (Scratchbuilt) 10264 Dec 12, 2019 02:11 AM
Discussion ** Kline-Fogleman Airfoiled Flying Wing ** Tony65x55 Foamies (Scratchbuilt) 3960 Jul 20, 2018 06:01 AM
Cool Here is my KFm-5 DLG GLider (Kline-Fogleman) dougmontgomery Foamies (Scratchbuilt) 151 Apr 21, 2014 09:08 AM
Video Kline Fogleman Airfoil on a flying wing Tony65x55 Electric Plane Talk 3 Jan 30, 2009 08:37 PM
Idea Per Dick Kline, Kline-Fogleman test dougmontgomery Hand Launch 49 Apr 13, 2007 02:13 AM