Originally Posted by Mitchell Covell

I managed to find that article: http://www.public.iastate.edu/~huhui...orrugation.pdf

Definitely worth a read.

Yeah, its really too bad they compared to an irrelevant airfoil - the GA was obviously too thick and not even as good as a flat plate. But the study does confirm that turbulation helps the stall characteristics of a flat plate, but that's not news or science.

And airfoils are designed with great care to avoid turbulence and the inevitable increase in drag.

Rick.

If I want to build a Kmf-3 airfoil for a 60" wingspan out of foamboard, do you think the board is going to warp to much?

Originally Posted by CarbonFlite

If I want to build a Kmf-3 airfoil for a 60" wingspan out of foamboard, do you think the board is going to warp to much?

Yes. During one of its early flights, my 60" delta started flapping its wings at one point. You can see the effects (from the plane's point of view) about one minute into this video. Use some good spars to keep this from happening... the shaking my plane experienced didn't seem to cause any permanent damage, but that kind of stress should probably be avoided.

Flying Over Ajax Waterfront (RC plane, aerial video, flying wing, KFm3 airfoil, gyros) (4 min 17 sec)

Originally Posted by CarbonFlite

If I want to build a Kmf-3 airfoil for a 60" wingspan out of foamboard, do you think the board is going to warp to much?

More layer, more spars, more staggered from the joint on other layers. Foam board is generally about 3/16"/4.75mm thick, for a 60: span with a one piece wing I would probably want to make it with a 3 layer center panel and add the 50% and 75% strips that form the steps as additional layers. The single layer step height will work fine, it you want you can make it a KFm9 with a third step.


==== <---- 33% step
======== <----- 50% step
============= <----- 75% step
===o========o======= <----- two small spars (48" long 3/16" dowels for example)
====================

Th secret to strength for me is the layers being full contact bonded with a PU glue like Gorilla Quick and the spars also being thoroughly bonded to the rest of the wing structure.

Jack

Arg! I posted the wrong video earlier (post 993). I've corrected the error.

Originally Posted by ibillwilson

Arg! I posted the wrong video earlier (post 993). I've corrected the error.

What camera were you using? I'm impressed by the way it handled going into and out of the sun. Nice little site you have there too!

Originally Posted by 2Doggs

What camera were you using? I'm impressed by the way it handled going into and out of the sun. Nice little site you have there too!

Thanks, 2Doggs. The camera is a GoPro Hero 2. I've flown it a number of times and gotten really good results, but I'm going to start using something less costly... At least until I have more experience building and flying. I've got an older compact HD cam ... A Kodak Zi6 ... That does 720p at 60 fps and handles lighting changes fairly well. It's bigger, heavier, and has a more awkward form factor for mounting on a plane, but it's much less expensive, and had already been relegated to the "outdated electronics" pile. I won't feel bad risking it's loss.

Edit: where are you in Lousiana? I lived in Baton Rouge for a couple of years, back around 2000 or so.

Here is a couple of photos of my first Klinefogelman wing project. It is made from EPP and has a 6 foot span. I did some sucessful glide test today and hope for a powered maiden flight tomorrow.

That is just far and away too cool. I love the scale pteradactyl underside. Much too cool for simpleton R/Cers like us. Nice guns on the model, too. Does she lift weights like FLOTUS?

It is kind of quiet over here. All we wanted is to know a little bit about the KF airfoils as they compare to some of the old standards, right?

Today, on another thread about wind tunnel sensors, poster Odysis said the following:

Originally Posted by Odysis

This should give you an idea of what you're in for...

If you haven't played with a wind tunnel, you'll be amazed at the amount of data required to make any sense. It's not trivial... If there is a university locally, I'd suggest a trip down and see if someone will show you over a low-speed tunnel.

If you have a program like M$ PowerPoint, or a viewer for it, or the free OpenOffice.org Impress program you can open the presentation above as a slide show and see what is needed to be done to set up a wind tunnel and get the data we are looking for. Very interesting stuff.

I think Odysis hit the nail on the head when he said it is not trivial...

Happy Holidays to all!

Jack

That wind tunnel link is indeed interesting. It's a complex area.
I read recently that in the early days the English and the Americans both had State Of The Art tunnels. They were both confident that they were doing good science.
After some time some the thought occurred that they should exchange some test models and see if their testing could be replicated.
The results were so random that it was clear that both tunnels needed a serious re-think.
However, that's a problem confined to testing that can be extrapolated to other cord sizes and Rn.
For Comparative Testing where, say a KFm2 and a Clark Y were compared for lift and drag under the same conditions, meaningful information could be obtained.
If the air speed and wing cord were both in the 'real world' range, no scale effects would complicate matters and Mr Renolds would be happy.
It's still complicated though...

Originally Posted by Whiskers

However, that's a problem confined to testing that can be extrapolated to other cord sizes and Rn.
For Comparative Testing where, say a KFm2 and a Clark Y were compared for lift and drag under the same conditions, meaningful information could be obtained.
If the air speed and wing cord were both in the 'real world' range, no scale effects would complicate matters and Mr Renolds would be happy.
It's still complicated though...

You are aware that there are ways to deal with the "scale effect" ...?

This is not a new problem.

Yes, but at OUR sizes we don't need to mess with it.
We are already there.

I've always thought that armed with a few sensors, you could do meaningful tests of model stuff using cruise control and a roof rack.....

It can be an attractive thought until you start thinking about the disturbed air-flow around the vehicle, the fact that airspeed and ground speed may differ and bumps and undulations will play havoc with lift readings... The list goes on.