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  #1  
Old 10-11-2010, 03:56 PM
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CBarber CBarber is offline
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Default 2/10th of a degree

I would be obsessing a bit more than I have been if during my first month following my kit delivery way back in the early 2000's, I didn't remember Branden (one of the factory tech guru's of the time) chuckling about how we builders would freak out regarding our calculations using digital levels. He reminded me that these planes were designed using nothing more than a simple bubble level.

Well, I got out my template jigs out to set the incidences to my wings and canard. After fudging with it all for a while, I have gotten the pilot wing and canard set to 0.0 on my handy dandy fancy digital level. However, the co-pilot wing differs by 0.2 degrees. Even with Brenden's comforting words ringing in my memory, I am still curious as if this is "good enough". I am not sure how much closer I can get them.

I ground down washers to get my wheels to align by using the formula of how much grinding on a washer would change the wheels per inch. It worked ok.

If I decide to drive myself nuts to get everything at 0.0, do we know how much difference in washer/shim thickness would change the incident.

OR, as I would think/hope, 2/10th of a degree is pretty damn good/close and my plane will still fly straight/level and I will not become a lawn dart.

Marc? You out there paying attention? You insight is alway appriciated...and I have learned to embrace and enjoy "your tone."

Thanks.

Chris
Velocity SE N-17010
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  #2  
Old 10-11-2010, 06:00 PM
Marc Zeitlin Marc Zeitlin is offline
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Default Re: 2/10th of a degree

Quote:
Originally Posted by CBarber View Post
... However, the co-pilot wing differs by 0.2 degrees. Even with Brenden's comforting words ringing in my memory, I am still curious as if this is "good enough".
You won't know until you fly. Even if you get all three surfaces to read 0.0 at the same time, you're relying on the accuracy of the level blocks on each surface, the accuracy with which you installed the level blocks, and also the actual contour of each wing. You could have slight contour differences that create slight lift differences (or moment differences) even with the level blocks all reading the same.

So, who knows. When you fly, you'll either find that you're perfect or that one wing is slightly heavy. You'll either be able to correct that with roll trim (if it's small) or with a washer under the appropriate wing bolt. Of course, adding washers means that your perfectly contoured strake/wing intersection will now look like dog crap (to you - no one else will notice it).

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If I decide to drive myself nuts to get everything at 0.0, do we know how much difference in washer/shim thickness would change the incident.
Incidence. Sure - one degree is 0.017 inches per inch. So, if the bolts are 5 inches apart (top to bottom) and you want to change the incidence by 0.2 (1/5) degrees, you need a washer that's 0.017" thick. If the bolts are closer or further apart, adjust that number based on the ratio.

Also, you could actually have a misalignment of anywhere from 0.15 to 0.25 degrees - the resolution of the digital level rounds off to the closest tenth (assuming you've calibrated it correctly). In this case, you could actually need anywhere from 0.013" to 0.021" (and of course, you won't know what it is, and it won't matter anyway, for all the reasons stated above by the Velocity Tech. and my first paragraph).

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Originally Posted by CBarber View Post
OR, as I would think/hope, 2/10th of a degree is pretty damn good/close and my plane will still fly straight/level and I will not become a lawn dart.
Certainly no lawn dart - maybe a slightly heavy wing. I had a heavy wing after my first flight and needed to add a thin washer to the top of one wing and the bottom of the other. I need a slight amount of roll trim at this point when at high speed, but the plane flies perfectly fine.

You won't know until you fly.

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Marc? You out there paying attention?
Well, I wasn't until you woke me up. I'm at work - you should really leave my nap time alone.

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Originally Posted by CBarber View Post
You insight is alway appriciated...and I have learned to embrace and enjoy "your tone."
Some folks like nipple clamps...
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  #3  
Old 10-11-2010, 09:01 PM
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Big Steve Big Steve is offline
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Default Re: 2/10th of a degree

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Some folks like nipple clamps...
excuse me for being a hick but what the heck are nipple clamps??


Never mind I probably dont want to know.
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Old 10-11-2010, 10:39 PM
ZG4Me ZG4Me is offline
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Default Re: 2/10th of a degree

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Originally Posted by CBarber View Post
... He reminded me that these planes were designed using nothing more than a simple bubble level.
Machine tools are often leveled with a spirit level, a high $ precision one though.

I've nothing against electronic levels, they are the cat's PJ's for reading angles (aileron up/down), but I use a 4' carpenters level (not a mason's level). I can stick a finish nail (.055") under one end, and the bubble is definitely not centered anymore. So grabbing my slide rule, this works out to be... umm... lessee... about.... umm.... a bunch less than .1 degree.

I expect I'll need a handful of washers after first flight, no way all my errors will 'even out'.

Rick
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  #5  
Old 10-12-2010, 12:08 PM
Buly Buly is offline
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Default Re: 2/10th of a degree

Here is something for you that have a "carbon fiber bug" in your brains:
http://www.customautotrim.com/vinyl/...iber_vinyl.htm
You can make the whole thing look like made of it.
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  #6  
Old 10-13-2010, 10:34 AM
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CBarber CBarber is offline
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Default Re: 2/10th of a degree

While not a carbon freak, that may be a nice way to finish up my IP. Seems kinda pricy though. I havn't priced carbon lately, but I may be able to use real carbon instead
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Old 10-14-2010, 01:48 AM
Marc Oppelt Marc Oppelt is offline
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Default Re: 2/10th of a degree

Quote:
Some folks like nipple clamps...
Hey...I like nipple clamps. Not so sure about the ball gag though, and the feather duster is just too much.
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  #8  
Old 10-14-2010, 11:22 AM
Marc Zeitlin Marc Zeitlin is offline
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Default Re: 2/10th of a degree

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Hey...I like nipple clamps. Not so sure about the ball gag though, and the feather duster is just too much.
That was my point. How one tortures oneself is an extremely subjective and personal thing.
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