Jabiru Winglets

[anjum_jabiru]

Hi Everyone

 

I have seen a few Jabirus having winglets. Does anyone have experience of using Ultralights with winglets? Do they enhance performance in any way or the whole thing about reducing wingtip vortices just impractical when it comes to Ultralights?

 

 

[Soleair]

The theory of winglets holds good for any wing. The noticeable effect will vary with speed. And of course on the design of the winglet.

 

Bruce

 

 

[Downunder]

http://www.zenithair.com/stolch801/design/design.html

 

 

 

[Jabiru7252]

They make it easier to hang a big rag so your less likely to smash your face into the wing when walking around the hangar. Done that once or twice.

 

 

[pylon500]

Unfortunately, I doubt that the winglets fitted to the jabiru's do anything useful at all...

 

They are too thick, have the wrong section, and have been fitted to a wingtip that is already using a totally different aerodynamic technology, ie; turned down Hoerner style tip.

 

 

 

[Old Koreelah]

...but they're a good place to fit fuel vents.

 

 

[anjum_jabiru]

I guess its cosmetic as they really look cool

 

 

[Soleair]

. . . . turned down Hoerner style tip.[ATTACH=full]42484[/ATTACH]

The term 'Hoerner wingtip' has become generic, it seems, to all modified tip profiles. But to be accurate, a Hoerner wing tip is not turned either up or down - it is level. See item 5 in the definition below, from this link:

 

Dr. Hoerner showed that the efficiency of a wing tip depends on six critical areas. His findings were:

 

 

 

1. The tip must be as thin as possible but still maintain a round leading edge.

 

 

 

2. A blending of wing top and bottom surfaces along a straight line.

 

 

 

3. The edge formed at this blend to be as thin as possible.

 

 

 

4. Obtain a sharp trailing edge leading to a corner, this corner to be in a straight a line as possible with the entire wing trailing edge.

 

 

 

5. The top of the tip to remain in a level plane with the top of the wing.

 

 

 

6. The bottom plane to be brought up in a convex curve.

 

Wingtips which project up or down ISTR were developed by Richard Whitcomb at LRC in the 70's, so presumably should be called Whitcomb tips.

 

A.Pedant

 

 

[Keenaviator]

When I was building my project, UL450, I spoke to someone at Jabiru, Jamie I think it was, about fitting those cool winglets like the later model Calipso (UL450). There may be a 1 knot reduction in stall speed. Not worth the effort and expense. But they are pretty. Laurie

 

 

[Roscoe]

They make it easier to hang a big rag so your less likely to smash your face into the wing when walking around the hangar. Done that once or twice.

And they look FANTASTIC !!!!

 

 

[Oscar]

Well, yes Roscoe, but the rest of your aircraft looks fantastic as well. They blend....

 

 

[Roscoe]

Well, yes Roscoe, but the rest of your aircraft looks fantastic as well. They blend....

Mate I was shattered when someone said they do nothing for performance!!.......but still good to look at!

 

 

[pylon500]

but still good to look at

cosmetic as they really look cool

But they are pretty

This is a bit of a worrying development.

Performance is nice, but looking good is more important?

 

 

[Mick]

Performance is nice, but looking good is more important?

Life is too short to fly ugly aeroplanes!

 

My Skylark has really big winglets ( by LSA standards ), in a review on the aircraft by an American magazine their comment was "The Skylark's winglets are either an efficient aerodynamic device or a clever marketing ploy, but either way they work!"

 

I have done some research on the design and from what I can find the design is correct to reduce tip vortices. As for how much difference they make? As I have not flown a Skylark without them I couldn't tell you.

 

 

 

[Jabiru7252]

There is code out there that runs on Matlab (an expensive scientific application us plebs cannot afford) that accurately models the airflow of various wing designs including things like winglets and vortex generators etc. Maybe I can get somebody to model the Jabiru winglets at work as Matlab is use extensively there. Then we can see if they do what we think they should be doing. The winglets on the plane in the previous post seem to me to be 'too little' to be of any practicle use.

 

 

[coljones]

We all know that spoilers and airdams make an Hyundai Excel go like the clappers and handle an F1 racer.

 

 

[jetjr]

Theres not even fuel vents in them

 

Looks good, thats it

 

Aircraft is too slow for this type of device to do much and as discussed its a different wing design anyway

 

 

[Birdseye]

We all know that spoilers and airdams make an Hyundai Excel go like the clappers and handle an F1 racer.

But correctly fitted, winglets may actually improve Jabiru glide performance.

 

 

[Bruce Tuncks]

I thought the Jabiru winglets were there to make the aircraft legal in the UK by making the ailerons more effective at low speed.

 

 

[anjum_jabiru]

How does it make the aileron more effective?

 

 

[Downunder]

Unfortunately, I doubt that the winglets fitted to the jabiru's do anything useful at all...They are too thick, have the wrong section, and have been fitted to a wingtip that is already using a totally different aerodynamic technology, ie; turned down Hoerner style tip.

Interesting but brief article (4 pages) which talks about "winglets" at the end.

 

http://www.academia.edu/8223146/THEORETICAL_ASPECTS_AND_PRACTICAL_US_AGE_OF_HOERNER_WING_TIP_AN_EFFICIENT_WING_TIP

 

Basically pretty useless unless you're big, fast and going long distances.......(drag and weight outperforming benefits in small A/C).

 

Still researching the "upside down" Hoerner....

 

 

[pylon500]

Actually, when you look at his diagrams, what he's really come up with by trimming the lower wing surface up to join the upper surface, is an elliptical wing tip as per spitfire.

 

Oh, hang on, the Spitfire came out before Hoerner....

 

In fact, the DeHavilland Rapide, Comet, Albatross even beat the spitfire.

 

But as for winglets, I believe they can be useful, even on slower aircraft (gliders come to mind), but it is a close run thing between blending out the tip vortex via a washed out tip vs a correctly designed winglet, where you have to balance the wetted area drag used to gain the the tip vortex drag reduction...

 

 

 

[Soleair]

An aerodynamiscist I worked with reckoned the increase of efficiency of the wing given by properly designed Whitcomb winglets was roughly the same as would be seen by adding their combined height to the wingspan.

 

In other words, if a measure of a wing's efficiency is its aspect ratio, found by span squared divided by area, then the height of the winglet added to the half span would increase the aspect ratio, & hence improve the L/D by a small amount.

 

 

[pylon500]

Pretty much.

 

I think we all discussed this back in another thread after I found some debatable comments on a NASA youtube.

 

http://www.recreationalflying.com/threads/new-theory-on-how-planes-fly.143310/page-3

 

 

[kgwilson]

I remember Garry Morgan telling me he spent more than 2 years experimenting with the winglet design for the Sierra resulting in enhanced performance, turn stability and reduction in stall speed. The Jab 3300 powered Sierra has a 75%power cruise of 130 knots, a clean stall of 37 knots & 32 knots with full flap. The winglets are blended into the tip. See photos below