201 Wingtips and the twisted wing.

[Lood]

Some time ago, there was a lengthy discussion on fitting new style wingtips to '67 F model Mooneys that sports the twisted wing - or rather the fact that it was not possible. I insisted that it was indeed possible and I was wrong.

A very clever greybeard at our local Mooney agent, that is a sheet metal expert and does magic with rebuilding just about any wreck, explained and actually physically demonstrated to me why the wingtip could not work. It does not have anything to do with altering the flight characteristics of the airplane or the wing, or anything along those lines. The leading edge on the twisted wing and that of the new style wingtip just don't match. Holding the tip to the wing, it fits perfectly all the way from the back up to about 8 inches from the leading egde. From here on, the shape of the wing is different to that of the tip and the leading edges don't match. The wings' being substantially lower.

We concluded that it would indeed be possible to make the wintip fit, but the front quarter of the tip would have to be removed and replaced with a completely new tip, together with a reshaped nav/ strobe light lens. This would of course not be certified, so it's a no go.
I did find the whole explanation and demonstration very interesting. There's also a lot of alteration that would be required regarding modification of the aileron balance weight in the stock twisted wing. This would be expensive and probably not worth the bucks, even if a certified tip was available.

Apart from the good looks, the newer style wingtips apparently makes the ailerons up to 14% more effective at low speeds. The old man also explained this to me in detail - very interesting day that I had with someone that knows the inner structure of the Mooney intimatedly.

[MARZ]

Don't suppose you took any pictures of that?   It would be neat to see.

[jetdriven]

where did he get the 14% value?

 

[Lood]

@ Maropers: Unfortunately not. The twist, however, is very easy to see and even more pronounced once you hold the tip in position at the wing tip. I'd love to have those on my Mooney - they do wonders for the cosmetics.

@ Jetdriven: I'm not sure. His explanation did make a lot of sense though. He explained how the swept up rear part of the wing tip would influence the flow of air to spiral inwards and deflect directly onto the outer part of the aileron. This would give it some extra authority during slow flight which, of couse is normally coupled with a higher AoA. With the normal square wing tip, the airflow would follow the easy way and deflect outwards, missing the aileron in the proccess. Does this make sense?

 

[DaV8or]

Quote: jetdriven

where did he get the 14% value?

 

[jetdriven]

Quote: Lood

@ Jetdriven: I'm not sure. His explanation did make a lot of sense though. He explained how the swept up rear part of the wing tip would influence the flow of air to spiral inwards and deflect directly onto the outer part of the aileron. This would give it some extra authority during slow flight which, of couse is normally coupled with a higher AoA. With the normal square wing tip, the airflow would follow the easy way and deflect outwards, missing the aileron in the proccess. Does this make sense?

 

[PilotDerek]

Everything I ever read on the mod says that they are only for looks. No speed added. They do look good though.

[aerobat95]

I heard the same thing that they were just for looks.  When I asked Dan at Lasar he said that if someone gave him the 3K for them sure he would put them on....but they do absolutely nothing for speed.  I too love the looks but cannot justify the expense for no real net gain other than looks.  Save your money and get a windshield mod or a tail mod or put it into the panel.

[Lood]

AFAIK, there is no speed gain. I agree 100% onthe 201 windshield mod though. In fact, that was #1 on my list of extra's during the current annual.

... but that was before they found out that my crankcase needs replacing AND the cam with all its goodies and the main bearings and the conrod bolts and nuts AND the gaskets AND the crank shaft has be sent to the US to be machined rechromed and polished to certified specs AND so on ...

[DCarlton]

On 10/12/2011 at 8:16 AM, Lood said:

Some time ago, there was a lengthy discussion on fitting new style wingtips to '67 F model Mooneys that sports the twisted wing - or rather the fact that it was not possible. I insisted that it was indeed possible and I was wrong.

 

A very clever greybeard at our local Mooney agent, that is a sheet metal expert and does magic with rebuilding just about any wreck, explained and actually physically demonstrated to me why the wingtip could not work. It does not have anything to do with altering the flight characteristics of the airplane or the wing, or anything along those lines. The leading edge on the twisted wing and that of the new style wingtip just don't match. Holding the tip to the wing, it fits perfectly all the way from the back up to about 8 inches from the leading egde. From here on, the shape of the wing is different to that of the tip and the leading edges don't match. The wings' being substantially lower.

 

 

We concluded that it would indeed be possible to make the wintip fit, but the front quarter of the tip would have to be removed and replaced with a completely new tip, together with a reshaped nav/ strobe light lens. This would of course not be certified, so it's a no go.
I did find the whole explanation and demonstration very interesting. There's also a lot of alteration that would be required regarding modification of the aileron balance weight in the stock twisted wing. This would be expensive and probably not worth the bucks, even if a certified tip was available.

 

 

Apart from the good looks, the newer style wingtips apparently makes the ailerons up to 14% more effective at low speeds. The old man also explained this to me in detail - very interesting day that I had with someone that knows the inner structure of the Mooney intimatedly.

 

Any bets on it being impossible?  I'll take possible.  

[aviatoreb]

I think from these posts some of the people are missing the point of the wing tips.

- yes the don’t make you go any faster.  They are not for going fast.

- they are for making you go slower.  The improve slow speed Aileron authority/control.

[PT20J]

They probably don’t do much for low speed handling. The problem with Mooney ailerons is that the are short span in order to give more wing to the flaps to make the flaps more effective. In order to get the required area with the shorter span, the ailerons necessarily have more chord. This increases the hinge moment. The Mooney push-pull control system had less mechanical advantage than other airplanes (the wheel doesn’t turn as far from stop to stop). All this adds up to fairly heavy controls. Back in the 60’s Mooney beveled the trailing edge of the ailerons which helped some. Adding the wingtips has the effect of moving the outboard end of the aileron away from the tip vortex which reduces the force on the aileron and helps lighten the controls. The shape, at Mooney speeds, is primarily aesthetic; it’s the extra span that creates the effect.

Skip

[Raymond J1]

The subtlety of the "F" wing is a twisted wing at the end, with ailerons that are not.

This also posed a concern for roll authority in crosswind on the first "F", hence the change of ailerons in the first series versions (increased travel with new counterweight design).

[Fly Boomer]

15 minutes ago, Raymond J1 said:

The subtlety of the "F" wing is a twisted wing at the end, with ailerons that are not.

This also posed a concern for roll authority in crosswind on the first "F", hence the change of ailerons in the first series versions (increased travel with new counterweight design).

This whole conversation makes me think how complex it is just to get a new design to flight test.  Once you have something that doesn’t try to kill you on every flight, the refinements can begin.  In spite of all the engineering knowledge and experience, a lot comes down to trial and error.

[Hank]

5 hours ago, Fly Boomer said:

This whole conversation makes me think how complex it is just to get a new design to flight test.  Once you have something that doesn’t try to kill you on every flight, the refinements can begin.  In spite of all the engineering knowledge and experience, a lot comes down to trial and error.

That's because, despite the proliferation of theories and computer simulations, there is still a difference between theory and practice . . . .

[aviatoreb]

The fact that Mooney was able to alter their wing to a twisted wing in 1967, suggests to me that the whole certification process was just simpler that then.  It would just be crazy expensive impossible to even think of such a thing back then.

[DCarlton]

2 hours ago, aviatoreb said:

The fact that Mooney was able to alter their wing to a twisted wing in 1967, suggests to me that the whole certification process was just simpler that then.  It would just be crazy expensive impossible to even think of such a thing back then.

I believe the twist wing was developed for the M22 Mustang and it was used for the M20 that year as well.  

[aviatoreb]

4 hours ago, DCarlton said:

I believe the twist wing was developed for the M22 Mustang and it was used for the M20 that year as well.  

I think you are right.

Nonetheless I gotta think swapping wings is an expensive certification nightmare these days.

[jetdriven]

It's not swapping wings. It was more like twist the outboard wing rib down 2 degrees and rivet the skins on. 

[cliffy]

Every change to an airplane design changes something else. Sometimes not even imagined. 

I'd like to fly a square end Mooney using flat plate endplates to control tip vortex to see what that did to drag and aileron effectiveness

I'm sure some  aero engineer could postulate what the effect might be also without actually flying the set up. .  

All the engineering in the world can't replace actual flight experience.