TE fences /blended winglets

[alleycat]

Greetings, I would like to construct the trailing edge fences for my VE, can some one help me with the sizes and placement of the units. I would like to fabricate the blended winglets that have I've seen on, I believe a Long EZ. Any specs on how they are made and what form they take. Is there a top speed gain? Thanks for the help. Allaycat

[GlennBob]

I'll give you my two cents worth. . . .cause that's probably all it's worth.

The trailing edge fences are more important on a Varieze because of the back swept wing.  More so than on the Longez.  The fences help keep the air flowing towards the rear of the wing instead of washing outward towards the wiglet.  This helps with slower approach speeds by maintaining aileron control down to slower speeds on approach and shortens the landing roll.   On the top end, it offers no speed improvement, .in fact if anything, . .adds a little drag.  (quite little though).  At cruise speed I don't think they have any effect except like I said a little drag.   They are quite simple and easy to make.  I made mine on the kitchen counter.  Took four layers of bid and made a big flat square from which I cut two each  fences.  I made mine (long-ez) about four inches tall and about a foot long.  For Vari-eze they could be a little smaller.  I put mine on each end of my aileron.  On the Varieze, I think you can put one on the inboard side of the aileron, and then I think I've seen two or three on the outboard side of the aileron.  Evenly spaced.  I floxed mine directly to the wing and radiused them in all perty . .but it was a lot of work and screwin' around.  Much easier to use RTV (room temp vulcanize  (or  silicone in laymans terms)).  Very important to get them mounted at the right angle.  Kind of complicated, but I dropped a plum line to the floor from my spinner center and from my pitot tube in the nose and made marks on the floor. Then I measured over to where I thought they should go and set up a ladder above the mark on the floor. Then I dropped a plum line . . . . ( more on next post ) . . . . . .

[GlennBob]

(continued )  I dropped a plum line to the floor where the mark was, . .then I pulled a piece of thread between the ladders to get my angle.  That's how I attached them.   I've heard they can lower the approach speed as much as 10 knots.   Good luck.   Glennbob.

[go ez]

Hi AllayCat

Have a look at this - that should cover it!

http://www.lightaircraftassociation.co.uk/pdf/Engineering/Standard%20Mod%202008/074_Varieze_SM11188.pdf

Steve

[GlennBob]

Yeah, . .I guess it's safe to say that should about cover it ! !

Glennbob

[A. Bruce Hughes]

Alleycat:

Be extremely cautious about making ANY changes to the plans.
I made very small changes to a Longeze and have been working
on it forever.   Any changes and you will NEVER finish.

You have to get FAA approval before you can fly it.   I am
currently hung on that.   I have an airplane that could be
flown but it cannot be flown legally.  It may never fly.

Bruce Hughes

[Marc Oppelt]

Alleycat:

Be extremely cautious about making ANY changes to the plans.
I made very small changes to a Longeze and have been working
on it forever.   Any changes and you will NEVER finish.

You have to get FAA approval before you can fly it.   I am
currently hung on that.   I have an airplane that could be
flown but it cannot be flown legally.  It may never fly.

Bruce Hughes

With all due respect my friend...I live in Olympia and I have seen your plane, and "plans changes" are not the problem with it.  The problem is a the quality of your workmanship.  It is scary.   Please don't ever fly that thing...if not for your own sake then for the sake of the people on the ground below you.  

I hate to be unkind, but this needs to be said.   I (and many others here) were very relieved when you posted that you were giving up this project.  The same when I drove by your plane and saw the engine removed.  Now I hear you've reinstalled the engine and you think you're back at again.

You need to take that engine BACK off the airframe, sell the off engine, and junk the rest.  That thing is a POS and will kill somebody if it flies.

That said...plenty of people deviate from the plans and still make it happen.  Some of the nicest canards out there are highly modified.  It's not rocket science...just be smart about it and think things through.

[GlennBob]

Actually it kinda  IS  rocket science.   But it's within reach ! !  I'm hoping to finish my " rocket "  sometime soon ! !  ( P.S.  I've learned to use the word  " soon "  to answer the forever nagging question : " When will you be done ? "  ! !   I too have made several modifications, but I don't forsee a problem.  My workmanship is as good as anyone elses, . .but it takes  FOREVER  ! !

Best wishes ! !

Glennbob

[mfryer]

I have to agree with mister G. Herder. I also have seen your project Bruce and I am concerned. I even helped you out once with installing the canard. It pains me to say this, but the workmanship is just not what we should expect in an aircraft.

[Joe Person]

Alleycat,

Side-issues above aside (i.e. back to your original question), "blended" winglets, I'm sure, could be done on a VariEze, but, I'd not simply charge off and copy what you have seen on a few Long-EZs and a Cozy or 2.  Such an udertaking involves sufficient engineering experience to: 1.  Design the configuration,  2.  Build a good test configuration,  3.  Properly test (for strength), 4.  Properly test for aero effects (flutter, stability, etc.) and, 5.  Spend the necessary time, money, work, re-work, etc., to make a safe configuration.  If you have the time and money (and skills/knowledge, or can hire it) to do all this, go get 'em.  From my perspective as an aerospace engineer, I'd not tread lightly into such a significant modification.  Flutter qualification alone would entail a rather significant run of analysis and (ultimately) actual testing.

FWIW, the VariEze wing does not have the same structural configuration as the Long-EZ wing.  The Long-EZ wing has a full-span spar/shearweb configuration, whereas the VariEze has a half-span shearweb, slightly more than half-span sparcaps, leaving the majority of the outboard half of the wing a pure foam-supported monocoque structure.

My dollar-three-eighty's worth,

[go ez]

I agree there is not a full span wing spar on the Vari Eze but don't lets get too hung up on that.

The higher loaded canards (GU and Roncz) do not have full span spars.
Neither Vari Eze or Long Ez have spars in their winglets even though the Long Ez's winglet is considerably longer.
The Vari Eze wing has 3 UNI and 1 BID plies on top and 2 UNI and 1 BID plies on the bottom  vs Long Ez 3UNI and 2 UNI respectively.

Structurally these a/c are very strong.
Regards
Steve

[Joe Person]

Not hung up on anything.  My point is that it will take some level of good structural analysis & design if one is to truely develop a blended winglet for a VariEze.  As for your comparisons, yes there are similarities, but there are also differences in structural geometry that have to be accounted for.  Yes, structurally, these airplanes are very strong (if built correctly), but that does not automatically guarantee success when fiddling with the primary structural configuration, as-designed.  The VariEze main wing was built to the level of "robustness" more for ground-handling loads and flutter considerations, vs. being designed for loads imparted from other sources in the operational envelope.  With the aspect ratio and the limited real estate available at the VEZ wingtips, I'd be diligent & conservative with analysis & testing of a blended winglet design.

[GlennBob]

Just a little clarification, . . .My comments were strictly regarding  Trailing edge fences . . .NOT  blended winglets.  I went back and re- read the initial question, . and it's a little confusing.  Actually, . .( I don't know if he knows it or not )  but he's actually asking  TWO questions.  My comments are only regarding the trailing edge fences, . .not blended winglets.

Glennbob