Measuring Foil Angles

[Admin]

I was under the impression the shim on the black puts the stab angle at the red level. So by this diagram with shim, black has more Stab angle than red. It’s not making sense to me.

Yes, on mine, the Black with the shim has more stabilizer down angle than the Red with no shim.  The Black without the shim has less stabilizer down angle than the Red without the shim.  But, the big difference with the new Black is not the stabilizer angle (only .5 degree change).  That is a relatively small change from the Red.  The front wing incidence decreased by the much larger 2.0 degrees.  That is where most of the change happened.

My actual measurements with no shim and no number smoothing were:

The 420 rear wing has an incidence of -1.91 degrees (on the black fuselage only).

The 390 rear wing has an incidence of -2.15 degrees (on the black fuselage only).

Those are probably the same design angles (2 degrees).  I can change the angle more than that discrepancy just by tightening the screws a little more (even when very snug already).  That is why I smoothed the numbers above.  I am sure there are minor sample variations and user tweaks that will move these numbers a teeny bit. 

[SUPeter]

Thanks for the info on the eflite anglepro doohickey.  That is going to save me some time making one that only works half as well.  That device coupled with two contour measurement devices back to back and ill be able to do some definitive comparisons between my wings and others.  great post!

[PonoBill]

Thanks for the info on the eflite anglepro doohickey.  That is going to save me some time making one that only works half as well.  That device coupled with two contour measurement devices back to back and ill be able to do some definitive comparisons between my wings and others.  great post!

Yeah. before I bought that thing I spent an afternoon fabricating one out of aluminum. More than a bit of machining, welding, filing, fitting and it still wiggled. I was about to take apart a couple of drawer slides when I came to my senses and spent the 60 bucks. The Anglepro doesn't shake or wiggle even though it's pretty cheaply made. Oh well.

[fumaster]

Made from Harbor Freight ratcheting bar clamp and FDM printed parts. Digital level is a GemRed 82142 found on Amazon. I'll attach the .stl files for printing.

[PonoBill]

Nice, I have one of thise clamps in my truck. I use it as a vise. It's how I cut down my 90CM aluminum mast.

[Admin]

Check out what George was saying about flexy tools in the vid below.  Any flex or movement between measurements will blow you up.  Also the shape of the jaws can be problematic if they don't find the leading edge point accurately.  That is pretty common on our beefy, offset foils.


https://www.youtube.com/watch?v=jTCyag5N_vE&t=191s