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Full-span rudders on Cozy (with pict)


Nathan Gifford
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I've attached a photo of Cozy MKIV with full-span rudders. I also removed the N numbers since I don't know if the pilot wants to talk about this mod or not.

 

Saturday night there was some discussion on whether full-span rudders were a good idea or not. Dust noted that Nat's old plane had rudders 3" longer than plans because the original MKIV was build without lower winglets.

 

Sunday morning I found this MKIV with full-span rudders. When we asked the pilot why he had them full-span he said his previous project had full-span rudders and it gave him much better crosswind performance with no negative attributes. When he built his Cozy, he did the same. We do not know what flight testing may have been done.

 

Not all my picts came out, but I also think the Stagger EZ also has full-span rudders.

 

It at least seems to me that this would be a really nice mod to have especially with internal bell horns. Besides crosswind handling, it might also help during landing descents.

 

Thoughts?

post-698-141090153121_thumb.jpg

Nathan Gifford

Tickfaw, LA USA

Cozy Mk IV Plans Set 1330

Better still --> Now at CH 9

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I also removed the N numbers since I don't know if the pilot wants to talk about this mod or not.

I think you're being TOO protective on this.

 

Good topic though -- I am curious of the same, and for the life of me cannot imagine any major reason why NOT to do this. The only thing I come up with FOR having the fixed part below the rudder is to protect the control surface in the event of minor contact with a hard object. This is STRETCH though, so... I'm still coming up with no reasons against and wondering why it was done that way in the first place.

 

The original VariEzes had very short rudders (maybe the orginal Long-EZs too), and then "high performance rudders" were introduced to where they are today.

 

This could be nothing more than natural/best progression.

 

Good topic Nathan!

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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Good topic though -- I am curious of the same, and for the life of me cannot imagine any major reason why NOT to do this. The only thing I come up with FOR having the fixed part below the rudder is to protect the control surface in the event of minor contact with a hard object. This is STRETCH though, so... I'm still coming up with no reasons against and wondering why it was done that way in the first place.

 

The original VariEzes had very short rudders (maybe the orginal Long-EZs too), and then "high performance rudders" were introduced to where they are today.

 

I can't imagine why either, the Velocity has full length rudders (well, not onto the lower winglet, but from the wing up) as well.

http://www.velocityxl.com/Winglets.htm#Section%203.3%20Rudders

post-848-141090153133_thumb.jpg

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Brett Ferrell

Velocity XL/FG

Cincinnati, OH

http://www.velocityxl.com

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Personally, I like the "winglet cap" and will just make the rudders 3" taller.

Just so we're clear, you mean the winglet will be the same size, but the rudder will consume 3" more of the winglet height?

 

I heard adding some rudder and elevator width made be beneficial as well.

Not sure if you mean width or chord, but that's something I'm not going to mess with -- especially the elevator. With the increased rudder surfance and authority that would result, so I don't see the need to make any more changes.

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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...flutter...

Yep... but since the rudder only travels one way, how can it flutter? Still, the concern ran through my head, and before I came to MY conclusion that this rudder modification is no more prone to flutter than the per-plans design, I thought to reduce its chord (forward-aft width) by an inch.

 

Brett, what is the chord/width of your rudders where they're closest to the wing? At the top of the winglet?

 

All things considered, a very interesting option. FWIW, I think it looks better.

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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Yep... but since the rudder only travels one way, how can it flutter?

Since I am one of the folks that has had rudder flutter, the answer is "easily", if you modify it as I did (don't have a HARD stop for the inward direction).

 

With respect to the "Full Length" rudder, the only reason not to do it from top to bottom is for the protection in a tip-back. This is not insignificant, but it's not an overwhelming reason not to do it. Velocities don't have to worry about that, since they always sit on all three wheels - no grazing.

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..."easily", if you modify it as I did...

Marc, I hope you don't mind if we don't write that one into the list of unofficial modifications. :)

 

With respect to the "Full Length" rudder, the only reason not to do it from top to bottom is for the protection in a tip-back.

Something definitely to consider for this not-so-critical modification.

 

We missed you at Rough River Marc. I had several inquiries into how you were doing, and... how I managed to get to Rough River this year. :)

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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..Since I am one of the folks that has had rudder flutter, the answer is "easily", if you modify it as I did (don't have a HARD stop for the inward direction)...

So for us that haven't gotten to that point in construction you did not (initially) install a hard stop on the rudder?

Nathan Gifford

Tickfaw, LA USA

Cozy Mk IV Plans Set 1330

Better still --> Now at CH 9

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So for us that haven't gotten to that point in construction you did not (initially) install a hard stop on the rudder?

No. I put in an adjustable stop, so that I could tailor the T.E. position if need be for initial rigging. Turns out there was compliance in the system, and at 202 mph IAS the rudder(s) would flutter. Once I took out the adjustable stop and put in hard stops (blobs of flox, sanded flat to give the right rudder position), the flutter disappeared.

 

The full description of the problem and solution is in the COZY archives from late 2002, I believe.

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Yep... but since the rudder only travels one way, how can it flutter? Still, the concern ran through my head, and before I came to MY conclusion that this rudder modification is no more prone to flutter than the per-plans design, I thought to reduce its chord (forward-aft width) by an inch.

 

Brett, what is the chord/width of your rudders where they're closest to the wing? At the top of the winglet?

 

All things considered, a very interesting option. FWIW, I think it looks better.

That's a good question. My wings are the airport or I'd mesasure them. The Velocity rudders are stopped inboard by the wing trailing edge, and won't flutter as long the winglet line is "inline" - or in other words the rudder is not deflected outward at rest. UPDATE: Just opened the manual online at the Velocity website. Rudders are 4 1/2" at the top and widen to 7 1/2" at the bottom.

 

The only time folks have seen a problem is when they're "shimming" a rudder out to correct for a slightly off-center ball condition during test flying. Shimming a rudder can bring the plane inline and get it flying straight, but if you unload the rudder too much it will flutter.

 

B

---

Brett Ferrell

Velocity XL/FG

Cincinnati, OH

http://www.velocityxl.com

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[Velocity] Rudders are 4 1/2" at the top and widen to 7 1/2" at the bottom.

Cozy Mark IV rudders are 4" at the top and widen to 7.5" at the bottom (not measuring the final flare to 10.5") -- they're virtually identical to the Cozy.

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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.... and won't flutter as long the winglet line is "inline" - or in other words the rudder is not deflected outward at rest......

The only time folks have seen a problem is when they're "shimming" a rudder out to correct for a slightly off-center ball condition during test flying. ..... but if you unload the rudder too much it will flutter.

You are correct that "unloading" the rudder can cause a flutter susceptibility, but that will only happen if the rudder is shimmed INWARD, not OUTWARD. Deflecting the rudder outward ADDS a load to it, so unless the shim (rudder stop, whatever you want to call it) has compliance (as mine had), it won't be a flutter contributor.

 

There have been numerous instances of rudder flutter caused by folks adjusting their rudders inward (for trim reasons). This unloads the rudder. Shimming the opposite rudder outward would have achieved the same trim condition, without the flutter issue (if the shim/stop was stiff).

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You are correct that "unloading" the rudder can cause a flutter susceptibility, but that will only happen if the rudder is shimmed INWARD, not OUTWARD. Deflecting the rudder outward ADDS a load to it, so unless the shim (rudder stop, whatever you want to call it) has compliance (as mine had), it won't be a flutter contributor.

 

There have been numerous instances of rudder flutter caused by folks adjusting their rudders inward (for trim reasons). This unloads the rudder. Shimming the opposite rudder outward would have achieved the same trim condition, without the flutter issue (if the shim/stop was stiff).

You are correct, I mistakenly reversed the direction.

 

Brett

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Brett Ferrell

Velocity XL/FG

Cincinnati, OH

http://www.velocityxl.com

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Here's another picture of that Cozy IV Nathan pointed out. It's Frank Bibbee's, who has the distinction of finishing his plane in 18 months!

 

I like the long rudder and the slight reduction in size of the lower winglet.

post-386-141090153136_thumb.jpg

Jon Matcho :busy:
Builder & Canard Zone Admin
Now:  Rebuilding Quickie Tri-Q200 N479E
Next:  Resume building a Cozy Mark IV

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