Wing to Stab alignment How To?
05-07-2012, 08:27 AM
#1
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Wing to Stab alignment How To?
How do you measure if the wing and horizontal stabilizer are in correct alignment. I know how to measure one from the wing trailing edge to the trailing edge of the horizontal stabilizer to insure the distance is equal on both sides. But how do you measure if the wings and horizontal stab are in the correct position relative to each other so you dont tend to roll when you pull back on the elevator. (I don't know what this alignment is called so it's hard to explain. ) I have never known how to do this accurately other than eye balling from a distance.
05-07-2012, 08:56 AM
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RE: Wing to Stab alignment How To?
I put a mark about half span on each wing, equidistant from the centerline. Then I eyeball the stab tips to those marks. Compensates for dihedral or airfoil taper.
A also measure tip of wings and stab above my flat building table to double check.
A also measure tip of wings and stab above my flat building table to double check.
05-07-2012, 08:58 AM
#3
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RE: Wing to Stab alignment How To?
Hope this works for you (and that Iunderstood your question) ...
Pic 1 - the wing is mounted to the fuse & the stab is pinned to the stab mounting saddle. It's sitting on your table and it is viewed from the front from as far back as you can get. The big visual gap between the stab tips and the wing bottoms suggest that the stab / wing are not in alignment but not sure how much
Pic 2 - raise the tail of the model until the leading edge of the stab is partially abscured from view by the wing. It is now easy to tell how much out of alignment the wing and stab are.
Pic 3 - shim the stab saddle on the low side until, when viewed from across the room, the stab tips are now equal distance from the wing's bottom.
The wing tip trailing edge corner to stab trailing edge corners are now equal distance.
The wing and the stab are now parallel with each other (it does NOTmatter whether they are at 90 degrees to the fuse - just that they are parallel.
Only remaining question before permanently mounting the stab: Is the difference between the angle of incidence of the stab and the angle of incidence of the wing correct?
You should assume that the stab is at 0 incidence (almost always the case). Adjust the fuse so that the stab is horizontal - you can use a small string level for this. What is the incidence of the wing? For an accurate reading use your incidence meter (or borrow one from a club member) and attach it to the wing near the fuse. Read the incidence - let's say 2 degrees. If the manufacturer suggests 1.5 degrees then shim the front (or back)of the stab. Reset the stab as level. Check the wing incidence. Repeat until the wing incidence is now as recommended by the manufacturer.
Pic 4 - incidence meter and string level set up.
Then glue the shims to the stab's mounting saddle. Some prefer to sand the stab saddle rather than use shims - reduces the amount of epoxy needed to fill the void. Sanding is not a good idea for an ARFthat is already covered.
Then epoxy the stab to its mounting saddle. Before the epoxy sets - repeat the "view from across the room" test and the measurement from the wing tip trailing edges to the stab tip trailing edges. Adjust as necessary.
Pic 1 - the wing is mounted to the fuse & the stab is pinned to the stab mounting saddle. It's sitting on your table and it is viewed from the front from as far back as you can get. The big visual gap between the stab tips and the wing bottoms suggest that the stab / wing are not in alignment but not sure how much
Pic 2 - raise the tail of the model until the leading edge of the stab is partially abscured from view by the wing. It is now easy to tell how much out of alignment the wing and stab are.
Pic 3 - shim the stab saddle on the low side until, when viewed from across the room, the stab tips are now equal distance from the wing's bottom.
The wing tip trailing edge corner to stab trailing edge corners are now equal distance.
The wing and the stab are now parallel with each other (it does NOTmatter whether they are at 90 degrees to the fuse - just that they are parallel.
Only remaining question before permanently mounting the stab: Is the difference between the angle of incidence of the stab and the angle of incidence of the wing correct?
You should assume that the stab is at 0 incidence (almost always the case). Adjust the fuse so that the stab is horizontal - you can use a small string level for this. What is the incidence of the wing? For an accurate reading use your incidence meter (or borrow one from a club member) and attach it to the wing near the fuse. Read the incidence - let's say 2 degrees. If the manufacturer suggests 1.5 degrees then shim the front (or back)of the stab. Reset the stab as level. Check the wing incidence. Repeat until the wing incidence is now as recommended by the manufacturer.
Pic 4 - incidence meter and string level set up.
Then glue the shims to the stab's mounting saddle. Some prefer to sand the stab saddle rather than use shims - reduces the amount of epoxy needed to fill the void. Sanding is not a good idea for an ARFthat is already covered.
Then epoxy the stab to its mounting saddle. Before the epoxy sets - repeat the "view from across the room" test and the measurement from the wing tip trailing edges to the stab tip trailing edges. Adjust as necessary.
