flyenforfun

flyenforfun

Well Known Member
Not sure if this is the case, but lets say one of my wings is swept forward more than the other, maybe a 1/4 inch or just slightly more. What flight characteristics would this cause?
 
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Sam Buchanan said:
Just as serious as I can be. Glad your day is now brighter. :)
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Now I have read that small variations in sweep are not a problem as long as both wings are the same. My left wing is slightly more forward than my right. Can I get a heavy wing? Weird yaw characteristics?
 
flyenforfun said:
Now I have read that small variations in sweep are not a problem as long as both wings are the same. My left wing is slightly more forward than my right. Can I get a heavy wing? Weird yaw characteristics?
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Matt, you may get some replies with engineering principles referenced, but my reply was based on seeing many RV builders rig their planes. A 1/4" variance at the wingtip is a tiny "error" that field experience has proven will have no effect on the flying qualities of your plane. There are other factors that would have much greater impact (control surface trailing edge radius, pushrod symmetry, vertical stab offset, landing gear fairing alignment, etc, etc......).
 
I agree with Sam. I doubt you would notice even a full inch of wing sweep difference. You would probably put a little trim and not even notice it. Airplanes are a lot tougher than people think. That is not license to be sloppy though.
I once had an inboard flap section on a C-130 that came off one of the jack screws. It was jammed almost fully extended and cocked and the corner penetrated the fuselage. After one of my stop and goes, I had put in a click or two of aileron trim but didn't think anything of it. The damage wasn't noticed until after parking the aircraft and the crew chief asked us if we had any logbook write-ups... We were shocked when we saw the damage that had gone undetected by anyone on the crew!
I also clocked a tree while pylon racing racing one of my R/C airplanes and lost 40% of the wing. The wing was attached to the fuselage with rubber bands. I took the remaining 60% of the wing and centered it over the fuse. The airplane was a little more unstable but it was faster!

Jerry
RV-8 N84JE
 
flyenforfun said:
Now I have read that small variations in sweep are not a problem as long as both wings are the same. My left wing is slightly more forward than my right. Can I get a heavy wing? Weird yaw characteristics?
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It has been some time since this has been discussed so I am not sure if a search will reveal all of the discussions in previous threads but basically you have nothing to worry about. If I recall, Van's allows 1/2" fore or aft sweep and they pretty much don't make a big deal about it, even if the wings differ.
The important thing is that you maintain the edge distances on your rear spar attach point. If you can not correct the sweep issue and maintain that, move on.
My left wing is 1/2" forward sweep. My right wing has none. This was because my QB fuselage was built at the factory with a slightly out of alignment center section. I have no issues. Well, my airplane has no issues, me on the other hand......
 
This is all great to hear. My edge distances on my rear spar are good. Its already drilled, otherwise I wouldn't be worrying about the sweep.

What is this control rod symmetry you speak of?
 
flyenforfun said:
Not sure if this is the case, but lets say one of my wings is swept forward more than the other, maybe a 1/4 inch or just slightly more. What flight characteristics would this cause?
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Small variations in wing sweep have two main effects:

  1. If the two wings have slightly different sweep, there will be a small difference in airflow over the left and right wings, which could make a very small difference in stall characteristics, etc. In practice, the swirling prop wash certainly causes more difference in airflow over the left and right wings than a small variation in wing sweep would do.
  2. Another effect of wing sweep is to move the average wing area ahead or back of the design location. So, if both wings were swept ahead by 1", that would move the average of the wing area 0.5" ahead of the design location. This would have an effect on the way the aircraft handles in pitch. If you compared the aircraft with the forward swept wings to an aircraft with no sweep, at the same CG location, the aircraft with forward swept wings would have lighter stick forces and lower static longitudinal stability. To get the same handling at the aft CG limit, the CG limit for the aircraft with wings swept forward 1" would need to 0.5" further forward than the CG limit for the aircraft with no sweep.

If you have one wing with zero sweep, and one wing with 1/4" sweep, this would move the average wing area 1/16" forward or aft of the nominal position. This is a neglibgle change.

I wouldn't worry about small variations in wing sweep. If both wings are swept forward or aft by 0.5" or more, that might make a measurable differnce in the handling in pitch. But, it would likely take more than 1" of forward wing sweep on both wings before the effect was big enough to cause concern.

If both wings are swept forward of the design location, consider moving the aft CG limit ahead of Van's specified value by one half of the average wing sweep.
 
Wing Sweet Limits

What experience is on record of delberate forward sweep to offset Angle Valve with Heavy Prop Forward C.of G.???

This is a pretty old thread but I would appreciate any input from Kevin Horton and others.

Sandy. Very slow QB
 
Sam,
You mentioned vertical stab offset in post #6. Can you elaborate. I have talked to those who have/haven't offset the vertical. What produces the best results in the field? Sorry not trying to hijack the thread starter
 
My first airplane, a Long EZ, was certified by a FAA inspector.

I told him the wing sweep from left to right was off by 5/8". His response was, don't sweat it, I've seen Cessna's coming off the line off by over an inch.

You do not have a problem...:)
 
Sam Buchanan said:
Matt, you may get some replies with engineering principles referenced, but my reply was based on seeing many RV builders rig their planes. A 1/4" variance at the wingtip is a tiny "error" that field experience has proven will have no effect on the flying qualities of your plane. There are other factors that would have much greater impact (control surface trailing edge radius, pushrod symmetry, vertical stab offset, landing gear fairing alignment, etc, etc......).
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I am another one like Sam that have seen small variance in wing sweep and with no noticeable effect. See Kevin's engineering calculations of effect to back these statements up.
 
Three thoughts -

1 - there's probably a prize to be claimed for having it turn out that close.

2 - were you to measure this a few days later, you might very well conclude the variation in sweep had moved to a different measure and / or direction. (Airplanes sometimes do this in the dark of night in the hangar when no one is around.)

3 - if someone ever does question it, tell them that you did it intentionally so that when a stall should occur, you would have the peace of mind of knowing that it will always break in the same direction (not true, but sounds good).

Dan
 
1/4" variance in sweep is great!

Now, go measure the height of each wingtip from the ground up. If that also is 1/4".... go buy a lottery ticket immediately!! :D (Many RVs have a very noticeable higher wingtip on one side due to tire pressure, cumulative errors, etc, etc... and it's nothing to worry about either!)
 
And then of course there are aircraft that are designed to have a different amount of sweep on each wing:

20782d1353110496-interesting-aircraft-rutanboomerang.jpg
 
A few weeks ago I had the pleasure of getting a tour of the 737 assembly line at Renton.

Up until very recently, Boeing used to attach the wings of these aircraft using plumb bobs, levels, etc....and, according to our guide, this meant each wing could be mounted slightly off from each other.

In my opinion, if a small variation is OK for a certificated airliner, your RV will be OK too :D
 
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