Forming plastic wing/fin add-ons?

[DynaSoar]

Here's the problem: I'm trying to come up with a sort of a flap (a K-F airfoil) that I can add onto a glider wing that'll stay in place during flight, but can be removed. It has to be light and smooth and hold snuggly enough to the wing. One side has to fit flush across its dimensions, the other side has to be slightly raised from the surface so that it leaves a "stair-step" discontinuity. Here's a link to what I'm trying to work on: https://www.rexresearch.com/klinfogl/klinfogl.htm The result can be hollow all the way underneath, or just folded over as if solid.

While I was building my Estes ARV Condor (https://estesrockets.com/products/product174.html) which is going to serve as the test bed for this project since it has two identical gliders, it occurred to me that the molded plastic parts that came with it were just about the right stiffness and weight. Now, I don't have vaccuum molding equipment. But I'm wondering if the kind of heat moldable plastic that's used is available, and if so, what it takes to mold it. Anyone ever worked with any heat moldable plastic like this? I did try cutting them out of various kinds of paper, but it doesn't have the spring enough to grip the wing without some kind of adhesive, and I can't glue it because I need to (a) switch it from top vented to bottom vented to test which is better, and (b) switch it between the two gliders for multiple tests to balance out any bias in the glide time measures due to differences in them.

 

[sandman]

Well, I can't get the link to work for me...

Try going into the "edit" and reposting the link.

sandman

 

[OKTurbo]

It's the period at the end that's messing up the link. Copy and paste...then backspace to remove the period after the htm.

Worked for me....

Interesting idea. You can "plunge" mold the plastic without the vacuum. Make up a frame to hold the plastic sheet...heat it up...and then quickly push it down over your master form. I've done this with clear plastic for canopies on free flight rubber powered airplanes. It will take a few tries to get the technique down...depends on the thickness of the plastic...temperature etc.

Sig Mfg has plastic sheets. www.sigmfg.com

John

 

[KermieD]

Holy cow! I remember seeing that issue of OMNI magazine and have thought of it from time to time thinking of a boost glider! The copy I had gotten a hold of didn't have the paper airplane kit in it and I was too lazy to try to build one from scratch.

 

[teflonrocketry1]

Don't go for the exact air foil shape at first, just try adding a step of extra material to build up the step you need. After you figure out how to add the step, then work on getting the exact air foil shape; take it a step at at time!

You could use hot melt glue to tack the edges of the steps onto the wings, solid balsa strips, polystyrene sheets, etc. When you want to remove them use a hair dryer to sofen the glue and remove the slats! You will have to experiment with which hot melt glue is best to use; some of the slower setting ones might be better for this type of application. Be sure to only tack down the edges.

Hope this helps,

Bruce S. Levison, NAR #69055

 

[powderburner]

The Kline-Fogleman airfoil is not what you want.

Many years ago, my interest was also peaked by the big claims for this wing shape. I was especially interested in the "stall-free" claims because I would have started using this airfoil for my RC models. I sent several inquiries to the inventors and received no response.

When I had to select a senior research project, several of the other guys in the class had already picked some cool airfoils (like the GAW series, and a new sailplane airfoil) so to avoid repeating, I went with the K-F. I made my models, ran the tunnel tests, and collected hard data.

Then I finally heard from the lawyers representing the inventors, and was threatened with a suit if I continued. Our campus lawyers said there was no basis for a lawsuit because I was not trying to profit in any way, but rather was simply performing research, so I continued.

Well, the short version of the story: the old NACA 23012 airfoil has better characteristics than the K-F. The Kline-Fogleman had higher drag, lower lift, more severe pitching moment shift, and much more severe stall onset. That's right, the Kline-Fogleman airfoil had very bad stall characteristics.

Turns out that what the inventors stumbled into is a three-dimensional aerodynamics effect, and it is really pretty much independent of the airfoil shape. The K-F airfoil really really is just as bad as classical subsonic aerodynamic theory would lead you to suspect.

Dynasoar, if you want to learn more, email me at [email protected]
I will see if I still have a copy of my old college research paper.

In the mean time, pick a better airfoil.