Dave Winrock
I'm New Here
I am rebuilding a RV-6 and in fitting the new wing I checked the other one that was undamaged and found it has a 1" forward sweep. The tip is forward of the root edge by that much. Is this a problem?
Dave
Dave
Van's Air Force
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Wing sweep
- Thread starter Dave Winrock
- Start date
mannanj
Well Known Member
Sweep
Probably not if both sides are even. I would re-define and make sure your fuselage centerline is correct and re-measure. If it's still has the forward sweep (I'm sure you've re-measured this numerous times!), as long as it is symetrical, there probably will be no problem.
You can verify this with Van's Tech Support
I continue to be totally amazed by how well these airplanes (OK all airplanes) fly with these little "lapses in concentration", or "attention to detail" while building!
Probably not if both sides are even. I would re-define and make sure your fuselage centerline is correct and re-measure. If it's still has the forward sweep (I'm sure you've re-measured this numerous times!), as long as it is symetrical, there probably will be no problem.
You can verify this with Van's Tech Support
I continue to be totally amazed by how well these airplanes (OK all airplanes) fly with these little "lapses in concentration", or "attention to detail" while building!
sprucemoose
Well Known Member
Forward sweep measured how?
This might seem like an elementary question, but how did you measure the sweep? Did you have the new wing installed? It is very difficult to get an accurate measure of wing sweep without both wings on.
If the new wing is on and has no sweep, and the old wing has 1", then you have a problem. You could sweep the new wing forward to match, or fix the sweep in the old wing. This would require new rear spar attach fittings (not such a big job, don't ask how I know.)
If you took the measurement without both wings attached, I'd wait until you have both wings on, take another measurement then re-evaluate.
This might seem like an elementary question, but how did you measure the sweep? Did you have the new wing installed? It is very difficult to get an accurate measure of wing sweep without both wings on.
If the new wing is on and has no sweep, and the old wing has 1", then you have a problem. You could sweep the new wing forward to match, or fix the sweep in the old wing. This would require new rear spar attach fittings (not such a big job, don't ask how I know.)
If you took the measurement without both wings attached, I'd wait until you have both wings on, take another measurement then re-evaluate.
mannanj
Well Known Member
Sweep
There is probably enough material on the rear spar of the new wing to match the forward sweep of the old one. One inch at the tip will not amount to much at the rear spar. Just doing a WAG on the ratio and porportons formula, 1/8th inch?????
Don't think I'm far from wrong.
There is probably enough material on the rear spar of the new wing to match the forward sweep of the old one. One inch at the tip will not amount to much at the rear spar. Just doing a WAG on the ratio and porportons formula, 1/8th inch?????
Don't think I'm far from wrong.
Kevin Horton
Well Known Member
It would be best if both wings had zero sweep, or failing that, both wings had the same sweep. But, I would be surprised if there was a discernible difference in handling or performance from this 1" difference in wing sweep.
So, if you can improve things, go for it. But if you can't, press on any way.
So, if you can improve things, go for it. But if you can't, press on any way.
Dave Winrock
I'm New Here
I do have both wings on and spent a lot of time today rechecking my measurements. It looks like I have 13/16" forward sweep on the right wing from end to end. It also looks like I have 2 degrees of angle of attack. The plane had been flying like this for years so I am thinking of just matching everything. Do you think this would cause me any problems?
Kevin Horton
Well Known Member
Small variations from the nominal sweep and incidence angle will have negligible effect. But, try to get the incidence angle the same on both wings, as close as you can. Measure the incidence at several locations along the span of each wing, and average the results, as there is usually some small variation depending on exactly where you measure.
But, there are side effects. Note that if the wing sweep differs from the nominal value, this puts the wing's mean aerodynamic chord in a different fore and aft location than intended. For example, if each wing tip is 13/16 ahead of the zero sweep location, the wing's mean aerodynamic chord is about 13/32 further ahead than nominal. From a handling perspective, this is roughly equivalent to moving the CG 13/32 aft. This will have the effect of making aircraft more sensitive in pitch at any given CG location. Thus the ideal CG envelope will be a bit different from that recommended by Van's. Of course, Van's recommended CG envelope is just a recommendation - it is up to each builder to do the flight testing to determine that the aircraft handling is acceptable at the extremes of wherever he choses to define the fore and aft CG limits. As a starting point, I would move Van's recommended CG locations ahead by 1/2 of the average forward wing sweep. Then do the flight testing to check the handling at those limits.
Thus a forward wing sweep might have the effect of limiting your allowable baggage load, if you have an aircraft with a light nose. If you solve that problem by putting more weight forward, that puts more weight on the nose gear, and thus slightly increases the risk of nose gear collapse during landing.
