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This thread is privately moderated by jackerbes, who may elect to delete unwanted replies.
Sep 03, 2018, 04:03 PM
Build straight - Fly twisty
Whiskers's Avatar
Not crappy, but almost everything needed to be replaced to make it better.
Hmmm...


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Sep 03, 2018, 10:49 PM
flyin' fool
goldguy's Avatar
Humm?? I know for a fact that KF airfoils generates more drag. Tested and compared by my FBs and myself. Seeing is believing.

Two different airfoils on the same wing without any effect would tell me the other airfoil is not very efficient. You need to compare the KF with a proper conventional one to tell the whole story.
Last edited by goldguy; Sep 04, 2018 at 11:36 AM.
Sep 03, 2018, 11:11 PM
Registered User
davereap's Avatar
KF=more drag, but more stability...
as with everything its "swings and roundabouts" with you picking what is more important.
I now use KF steps only on powered models and more normal simple and thin sections on my gliders... And all my indoor stuff being even simpler flat foam..
Sep 03, 2018, 11:36 PM
flyin' fool
goldguy's Avatar
..
Sep 04, 2018, 12:00 AM
Build straight - Fly twisty
Whiskers's Avatar
Quote:
Originally Posted by goldguy
Humm?? I know for a fact that KF airfoils generates more drag. Tested and compared by my FBs and myself. Seeing is believing.

Two different airfoils on the same wing without any effect would tell me the other airfoil not very efficient. You need to compare the KF with a proper conventional one to tell the whole story.
The 'conventional' airfoil has a square trailing edge like a typical foam slab KFm. My aim was to make the two sides the same except for the aft 2/3 of the top of the wing. Steps on the right, smooth curve on the left.
It is absolutely correct that the 'conventional' airfoil is far from optimal.
The experiment was to test, 'steps' verses 'no steps.'
It should be noted that the foam was only 'as sanded' or 'as supplied.' so the surface would have generated a turbulent boundary layer.
My theory regarding the performance similarity is that the vortexes generated by the steps creates a virtual surface similar in shape to the turbulent boundary layer generated virtual surface of the non-stepped wing.

I think the comparison of a KFm to a "proper conventional one" would be a forgone conclusion. JetplaneFlyer did that with an Elf DLG and found a 10% performance deficit.
A thing that greatly impressed me with that comparative test was how the glider fitted with the Drela wing flew in such a lively and responsive way, reacting to every little hint of lift, in contrast to the stolid unresponsive glide when using the KFm wing. I think that was an example of the much noted KFm stability. And that, for certain applications, can be a good thing.
Sep 04, 2018, 08:52 AM
Build straight - Fly twisty
Whiskers's Avatar
While we are doing this I'd like to know what you knowledgeable gentlemen think of the validity of the side by side wing-section concept for comparative testing?
I was mainly interested in looking at the stall behaviour of the test sections.
I think it is a good way get a direct comparison, but Jack thinks it is a stupid idea.
Comments?
Sep 04, 2018, 09:14 AM
Jack
jackerbes's Avatar
There you go again! Reading something into my words that was not said!

I merely said I did not think it was a good way to get a comparison between two foils...

I notice from your blog page that you have quite an interest in FPV flying. My keychain camera's battery has expired over time and I'm going to buy a better camera (not for FPV, just aerial photography). What is a good camera that has better resolution than the keychain or gum pack cameras I used in all of my youtube videos?

Jack
Sep 04, 2018, 11:49 AM
flyin' fool
goldguy's Avatar
Step VS no step only ……………….. I get it. Experimenting is part of the fun.

I've not noticed anything negative about the KF on powered models. Actually, like Dave, I prefer them on powered models, that or flat.

The slope is the only place where we've seen the negative effect of the KF, which was drag. But, with ballast in lots of wind/lift they worked very well. You just have to get them moving forwards to generate lift.

My latest KF bird, the Trottel, sports a KF wing made from 8mm EPP for the wing and 5mm for the step at 45% on the top. I've used this before and found it worked well (for me). Maybe step height and location are still an areas to explore.
Sep 04, 2018, 06:22 PM
Build straight - Fly twisty
Whiskers's Avatar
Quote:
Originally Posted by jackerbes
There you go again! Reading something into my words that was not said!

I merely said I did not think it was a good way to get a comparison between two foils...

I notice from your blog page that you have quite an interest in FPV flying. My keychain camera's battery has expired over time and I'm going to buy a better camera (not for FPV, just aerial photography). What is a good camera that has better resolution than the keychain or gum pack cameras I used in all of my youtube videos?

Jack
Jack, I was not reading something into your words that was not said. My phrase is just an example of Aussie verbal shorthand.

Regarding the camera: I am not very knowledgeable in this area, but you may like to look at this inexpensive little camera which will certainly be better than the key-chain ones.
https://www.banggood.com/buy/sq8-min...xoCGb8QAvD_BwE
Sep 04, 2018, 09:33 PM
Registered User
I don't know if this is worth anything for the subject, I intend to build a model called the blitz, simple box fuse and a straight wing, but it had a funny tail section, very nice plane had 2 of them flew great, this next one will be a foam kf airfoil, a single step on the top of the wing, I hope it flies well, if it does I'll have my friend cut a balsa version with the semi symetrical wing for it and do some comparisons
Sep 04, 2018, 09:49 PM
Too old to rock-n-roll...
TooJung2Die's Avatar
Quote:
Originally Posted by jackerbes
My keychain camera's battery has expired over time and I'm going to buy a better camera (not for FPV, just aerial photography). What is a good camera that has better resolution than the keychain or gum pack cameras I used in all of my youtube videos?
I bought the SQ11, the next model up from the SQ8 that Whiskers linked. It has thousands of positive reviews and the video posted online from the SQ11 looks pretty good. My bad luck, I got a defective camera. It won't set the time, won't print a date stamp on the video, and after a minute of recording all the data is corrupted and won't play. I am not deterred. Banggood is sending me another SQ11. I can say that the 1 minute of video it manages to capture looks a heck of a lot better than the keychain camera I also have.

Jon
Sep 04, 2018, 11:39 PM
Build straight - Fly twisty
Whiskers's Avatar
Quote:
Originally Posted by slam555
I don't know if this is worth anything for the subject, I intend to build a model called the blitz, simple box fuse and a straight wing, but it had a funny tail section, very nice plane had 2 of them flew great, this next one will be a foam kf airfoil, a single step on the top of the wing, I hope it flies well, if it does I'll have my friend cut a balsa version with the semi symetrical wing for it and do some comparisons
Yes indeed, your results will be of interest to us.
Post video if possible.
Sep 05, 2018, 06:28 AM
Jack
jackerbes's Avatar
Quote:
Originally Posted by Whiskers
Jack, I was not reading something into your words that was not said. My phrase is just an example of Aussie verbal shorthand.

Regarding the camera: I am not very knowledgeable in this area, but you may like to look at this inexpensive little camera which will certainly be better than the key-chain ones.
https://www.banggood.com/buy/sq8-min...xoCGb8QAvD_BwE
OK, buy some of us don't use or understand that dialect of English...

Here in the North American colonies when we would have said "..Jack does not agree with that..." or words to that effect. That is because anyone reading your "shorthand" might think I had actually said it was a stupid idea when I had not. That thought may have crossed my mind but it was not expressed in my writing. :>)

Thanks for the camera suggestion, that should improve things. The key chain camera resolution is 720x480 and the one you suggest is 1240x 720, that should improve things. And at 28 grams the weight penalty is not very much...

Jack
Sep 05, 2018, 06:29 AM
Jack
jackerbes's Avatar
And thanks for the SQ 11 details too Jon, will consider that also.

Jack
Last edited by jackerbes; Sep 16, 2018 at 02:53 PM.
Sep 16, 2018, 12:25 PM
scratchbuilder
Thomas B.'s Avatar

KFm 2 Temco Pinto


My father and me flew his Pinto design this morning. Very smooth flyer. free download plan is in progress.
2 Temco Pintos im Flug (2 min 54 sec)


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