Lower winglets. Do I need them?

[matt cozy1429]

What are the advantages of the lower winglets like on the Cozy and the LEZ? Berkut and Eracer do not have them.

 

I remember a web site I looked at a few years ago where a Long EZ flyer cut his off, if I remember it correctly he did not find any difference.

 

It seems like I could save some construction time by building the lower winglets like the E-racer.

 

Opinions?

 

Matt

[Drew Swenson]

In the Cozy, cutting off the winglets brought the aft end of the CG envelope forward---which typically meant that you had to carry more ballast to compensate.

 

The lower winglet does one more bit of protection for you---it is a piece of the plane you can drag on a runway. I have actually done it on takeoff---very minor damage to the lower winglet. The lower winglet protects the layups that hold the winglet onto the wing.

[Wayne Hicks]

Go to the Cozy newsletters and start reading from #43.

[Richard Riley]

What are the advantages of the lower winglets like on the Cozy and the LEZ? Berkut and Eracer do not have them.

 

I remember a web site I looked at a few years ago where a Long EZ flyer cut his off, if I remember it correctly he did not find any difference.

 

It seems like I could save some construction time by building the lower winglets like the E-racer.

 

Opinions?

 

Matt

Berkut DOES have them - they are just very small.

 

They dam up spanwise flow at low speeds and reduce roll coupling. Without them, low speed handling suffers significantly. TE fences - like Klaus' - help a lot.

[Wayne Hicks]

The Cozy does not have as much aft CG margin as the Long EZ. The Long EZ has a few inches more margin and can thus "give up" margin that goes away with removing the lower winglets.

 

Keep the lower winglets.

[matt cozy1429]

Interesting write up in the #44 on the Cozy flying without them.

 

So removal of the lower winglets:

 

Drops lift by letting the high pressure under the wing spill out. I can see how if you lose lift because of the loss of winglets you would have to move the CG limits slightly forward.

 

Also raises stall speed and effects the behavior of the aircraft in near stall conditions.

 

Plus it keeps you from scraping a wing.

 

Thanks to Wayne, Richard and Drew for taking me to school.

 

I'll keep the winglets.

 

Matt

[Wayne Hicks]

There was a brilliant discussion of lower winglets on the Cozy email group and on the Canard Aviators email group. Within the past two months. Go to their search engines and do a search on "lower winglets."

 

Cozy Email Search Engine

Canard Aviators Email Search Engine

[Waiter]

I understand the plane in question is a Cozy IV.

 

When I introduce someone to the the flying characteristics of a LongEZ, This is one of the demonstrations I include in the flight.

 

My LongEZ operates at the aft CG limit. I perform this type of maneuver regularly, i.e slow flight, high angle of attack.

 

My result (with winglets) have always been the typical gentle canard bobbing (stall/unstall), and just a touch of dutch roll, the dutch roll is normally imperceivable and would never depart.

 

Mild aileron and/or rudder inputs would introduce a minor dutch roll, but the aircraft would always return to a stable condition.

 

When I removed the winglets, I flew the same test series several times, I could not tell any difference.

 

IMHO: the only thing I lost by removing the winglets was some tip back protection that the winglets offer. A tip-back (with winglets) will (may) damage the wheel pants. A tip-back without the winglets will most likely damage the wheel pants, prop spinner, and lower cowl (and the prop if its not timed horizontally.

 

 

NOTE: If you have a significant roll angle, you may hit one winglet before you hit the prop. However, I don't think the winglets will protect against a high AOA during takeoff or landing, If the AOA is high enough to hit the winglets, then you've already destroyed the propeller.

 

REGARDLESS - If this is the case, then you need to review your takeoff and landing procedures, The Canard should NEVER be above the horizon, to do so invites the possibility of a prop strike.

 

Waiter

[matt cozy1429]

Started out with all intentions of building a Cozy. Decided on building a Long EZ.

[Waiter]

Decided on building a Long EZ.

I knew you were a highly intelligent and a very smart person. :D

 

Waiter

[Drew Swenson]

When I talked about scraping a wingtip, it was in roll not pitch. A gust of wind caught me pretty good on take off---just at rotation. The percieved roll angle that the gust got me was not that great at all. I could hear a scrape from the cockpit---wondered what it was---and thought I had done something to my wheelpant. Checked the wheelpant after landing----no damage---and forgot about the incident until a month or so later when I was cleaning the plane. And there was the scrape on the bottom of the winglet. Ground down a flat spot to the foam---was not event that big---and easily repairable.

 

The Cozy MKIV with and without lower winglets is well documented by Nat. Part of his design included removing the lower winglets. CG testing did not meet his expectation---and surprised him. I think the first thing he did was put the lower winglets back on and gained back some lost aft CG---but still not satisfied. Then cut some length off the canard with good results---then cut some more.

 

I prefer the Longez to the Cozy MKIV for its comfort and better field of view and more economical to operate. The Cozy has faster roll rates---and more importantly satisfies my mission need----need at least a three place with luggage.