Gazaile 2 vertical tail

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stevetosh

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Dec 25, 2010
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brisbane, Australia
Hi everyone,

Please I'm having a bit of issues with my vertical tail angle's measurement. The tail needed to be set to a +13 degree angle, now when I placed my digital level on both side I'm getting a reading on both sides. Is there any way I can correct this issues? I have attached pictures of my reading to explain the problem better.

Thanks
 

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Vigilant1

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I hope I am understanding your issue correctly.

Just confirming: Vertical tail or horizontal tail?

Assuming the measurement is supposed to represent the angle between the tail's chordline and some other line on the fuselage (e.g. a horizontal or vertical reference line on the fuselage) , you'd need to:
1) Assure that line on the fuselage is truly level. You may need to lift the nose or tail to make that happen.
2) the tail line you want to measure is probably an internal line that goes from the very front of the leading edge to the trailing edge (the chordline). Whatever you place your electronic level on (your foam template) must be parallel with that internal line. So, the foam template must be exactly the same distance above the LE point and the TE point. I suspect this is your present problem. The template looks much thinner at the LE and fatter at the TE (camera angle/perspective?). This would produce the error you are seeing, with both the top and bottom being "wrong" in opposite directions.

Does the designer, M. Pennec, still conduct daily consultations with builders?
 
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wsimpso1

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Saline Michigan
Please I'm having a bit of issues with my vertical tail angle's measurement.
It sure looks like you are measuring your horizontal tail stabilator up angle, not your vertical tail.

Placement of your jig on the green foam does not look to be identical in both photos. Effort must be taken to make placement of the entire jig identical, or you will be mixing in jig angle variation with part position. In particular, I can see the green foam is placed further aft in one photo ( look at the trailing edge), the white board is placed further aft and angled side-to-side differently in one photo vs the other, and the digital level is also further aft in one photo vs the other.

Third, how precisely did you establish the lateral positions and alignment of the jig in the measurements? We can not see how you established these positions, but they too will contribute to measurement errors.

The combination of all errors of placement of the measurement jig will generally contribute to "noise" in measurement and make discernment of actual dimensions difficult. You appear to have several sources that are not controlled for, and numerous others that may also be contributing. In addition, errors on the order of what you are measuring may also be present by how well supported the stabilator is on the fuselage. Putting in efforts to positively assure consistent placement are important for making measurements of these sorts something you can trust, and must be present to make the diagnosis valuable.

The tail needed to be set to a +13 degree angle, now when I placed my digital level on both side I'm getting a reading on both sides. Is there any way I can correct this issues? I have attached pictures of my reading to explain the problem better.
Once you have a method that is consistently applied to both sides and produces consistent results, then you can start to address the potential twist implied in your stabilator. Quite frankly, if the stabilator has a full degree of twist between spots near the Butt Line, I would be very concerned about how much twist is present further outboard. Further, are you seeing spanwise waviness or spanwise twist of the stabilator?

Is your stabilator bonded together, spar, ribs, skins? If yes, any built in twist is fixed in this part. You can do some reprofiling with dry micro, and finish like a composite airplane, but that will add weight. The balance weight can be adjusted to compensate for the weight, but I do not know how flutter sensitive this stabilator is to its mass being higher, nor know how tolerant the design is to adding weight all the way out at the tail. If only one skin is on, or if one can be removed (it is a thin plywood skin, one side can be removed with a angle grinder in a half-hour) and a new skin reapplied with the stab firmly supported and straight, you could get a straightened assembly.

If the stabilator is much crooked, there is always making it into a shop decoration, and then make a new one with much attention paid to making the jigging as symmetric as is possible.

One last possibility is to simply live with the tail being out of shape. I hate the thought, but am sure that folks have done worse. The tail will be running with some additional induced drag and putting a modest rolling moment into the airplane that you will have to trim out someway. Being as it is a part you can unbolt and bolt on a better one, you might even be inclined to fly this one, apply the fixes, then bolt on a really straight stabilator and see how much difference it makes. The difference largely depends upon how much difference you really have between sides.

Billski
 

TFF

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Apr 28, 2010
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Memphis, TN
To me it looks like horizontal and I’m going to say close enough for government work. You are also not measuring at the same point. Not sure what else.
 
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