Radised Wing-Tips

[Double T]

I had always read that the Lockheed P-38 Lightning had radised wing-tips.
Building the old Monogram kit in 1/48 scale--my only reference--I had nothing accurate to illustrate just what this entailed. I thought perhaps it had to do with the shape of the wingtip itself, maybe fatter at the back than at the front of the leading-edge.
WRONG.
I'm currently working on an Academy/MRC 1/48 P-38F Lightning "Glacier Girl" and this is the first kit I've ever handled that depict those radised wing-tips. (It's a beautiful kit by the way...)
The entire wing-tip actually angles up for the last 6ft or so... a guess looking at 1/48 scale. It's quite a dramatic effect. If I understand the dynamics of windflow, air tends to leak over the top of the wing-tip in flight, causing a disruption and resulting drag.
The radised-tip I'm guessing, cleans-up the airflow at the wingtips and decreases drag... though I'm not sure of any resulting performance enhancements.
So, like the winglets employed on commercial planes by Boeing and Airbus, they improve stability and decrease drag, adding economy through decreased fuel usage? Is this correct?

What other planes in World War 2--and what other designers--also understood the value of radised wing-tips.

Tim

[GregP]

Actually, I'm not sure what you mean by radiused wing tips.

They do join the leading and trailing edges smoothly, but they do not join with a cricular radius. They join using elliptical shapes and wind up having a very smooth transition between wing tip and leading or trailing edges. The wing tip shape is very similar to the wing tips on the Curtiss P-40 Warhawk series of single engine fighters. The P38's wing tips are somewhat smaller in chord, and so may taper differently, but the two wing tip shapes are VERY similar.

Aerodynamically, smoother is better, sometimes MUCH better.

The wing tips do narrow more from the under side than from the top side, as you state and, again, they do so smoothly.

Maybe you could describe more what you mean by radiused wing tips and illustrate with a drawing?

[Red Admiral]

I think "raised" wing tips might be the meaning.

This increase of the dihredral would increase the stability of the aircraft but any effect on efficiency would be negligble, unlike winglets used today.

[GregP]

Ah ... rasied wingtips.

Usually they are used to impart a small extra bit of stability if the stability wasn't QUITE up to where the service test pilots wanted it to be.

The P-38 wingtips do taper more from the bottom, but probably not enough to be called a true Hoerner tip. True Hoerner tips usually angle upward at about a 30° to 45° angle, and are not a smooth transition.

You might check about halfway down the page here: http://selair.selkirk.bc.ca/aerodynamics1/drag/page8.html.

There has been a lot written about Hoerner tips, droop tips, tip plates, and Whitcomb winglets and I just don;t feel the P-38s wingtips qualify as any of the above, though they do have a marked rise that is different from the rest of the wing.

I suppose it's all in the eyes of the beholder. I certainly wouldn't argue against calling them "raised," but I wouldn't term them Hoerner either. In any case, the Lockheed P-38 made significant inventive inroards in what, up until its debut, was a pretty conservative and stodgy general fighter layout. It deserves comment if for nothing else than cutting a new shape in the sky amid all the low-wing, cantliver, single-engine designs that were so prevalent up until the P-38 went into production.

Too bad Lockheed never quite solved the low critical mach number behavior of the airframe. In hindsight, there are many "fixes" that would have helped, but we have the benefit of 60 years of aerodynamic research to help us. Back in 1939 - 1940, they were just discovering that the P-38 had some issues at high airspeeds and were scratching their heads wondering what to do to overcome it.

Though they enver quite "fixed" it, the dive recovery flaps went a long way to help safety.

[curmudgeon]

quote:Originally posted by GregP
I suppose it's all in the eyes of the beholder. I certainly wouldn't argue against calling them "raised," but I wouldn't term them Hoerner either. In any case, the Lockheed P-38 made significant inventive inroards in what, up until its debut, was a pretty conservative and stodgy general fighter layout. It deserves comment if for nothing else than cutting a new shape in the sky amid all the low-wing, cantliver, single-engine designs that were so prevalent up until the P-38 went into production.


And especially for Lightning who will find this page fast - there is a nice coverage of the P-38 in the June 2006 issue of Aeroplane Monthly and including a long interview with Bong's wingman.

[Tophe]

I know this discussion was about the Reality of such raised wingtips on the P-38 and Actual advantages, but your words are also read by dreamers like myself…
I know this is not your subject but below is the result in my dreamy mind: P-38WL with winglets, P-38FW flying wing with no rear fins/rudders…
http://img.photobucket.com/albums/v670/Tophe2712/Extra1/r_P38hy_zzj.jpg
Thanks again. (And sorry, I let you discuss seriously again)

[GregP]

Hi Tophe!

You need some vertical surfaces on the one with no rear fins.

Maybe a single vertical surface running from the rear of the pilot's pod to the stabilator, with a rudder on the end, rounded like the rest of the P-38? Sort of like a big fin and rudder? Maybe raise the small horizontal stabilators outboard of the booms to about 30° inclination.

The added drag would be small and the plane might actually then fly. The area would be the area of the two original fins and rudders plus the area of the fins and rudders on the wingtips (you have to offest destabilizing influences by adding the same area to the rear fin and rudder in compensation). The result would look not unlike the Rutan (Scaled Composites) Pond Racer and might be a very good aircraft indeed. :)

[Tophe]

Yes, the P-38FW could be turned into a P-38PR Pond-Racer-likening, but for me this has a severe drawback: it falls out of my beloved twin-boom class to become triplex-boom. So I have truncated it into the twin-boom P-38PR²…
Well thanks for having enriched the P-38 collection… maybe now we should stop hijacking this serious topic…
http://img.photobucket.com/albums/v670/Tophe2712/Extra1/r_P38hy_zzu.jpg

[GregP]

Damn Tophe, you are QUICK! I appreciate the interest and response!

The tripple boom is WAY cool! I know you like twin boom, but the tripple boom is just great!

Now go get it built in Europe by someone ... maybe Eurofighter?

It would sell! With Allisons or Merlins.

Allisons last longer and are less difficult to keep running. :)

[Double T]

Tophe:
I knew you wouldn't be able to resist this thread!

Actually, the effect is similiar to what Tophe has done with the rear elevators in his drawings. When you look at the kit of the Lightning head-on, the actual wingtips are pinched at an upward angle--a few degrees--compared to the rest of the main wing.
Just the wingtips.
I always read the Monogram kit did not reproduce this feature and so rationalized THIS was the radised wing-tip. I think GregP is of the opinion that this refers to the actual shaping (elliptical) of said wingtip... not it's relation to the wing.
Yeah, I'm still confused.

Tim

[Tophe]

In common sources, the P-38 wing is straight, is it wrong according to Realists? Were all Historians secret dreamers like I am officially?:D
http://img.photobucket.com/albums/v670/Tophe2712/Extra1/P38-rw.jpg
(thanks to http://www.warbirdsresourcegroup.org/URG/images/p38-23.jpg )

[Lightning]

Hi curmudgeon,

Quoting you:
quote:
And especially for Lightning who will find this page fast - there is a nice coverage of the P-38 in the June 2006 issue of Aeroplane Monthly and including a long interview with Bong's wingman.

Thanks for the "heads up," curmudgeon; I very much appreciate it! I don't know if I can find that magazine in this area, but I'll certainly try!

Regards,
Lightning

[Lightning]

Hi Tophe,

Welcome back!!! Where on Earth have you been? I had begun to think something had happened to you.

Regarding your latest postings, you've added another "Bent-wing Bird" to the list of aviation curiosities. (Now if we can just come up with a twin-boom Corsair. :D)

Don't stay away so long next time!

Regards,
Lightning

[Tophe]

Hello dear,
Teasing me when you mentioned a twin-boom Corsair?
Well, I did something on the subject several months ago:
http://img.photobucket.com/albums/v670/Tophe2712/r_Twosair_h.jpg
Will you enrich the gallery of possibilities? This would be welcome (from my point of view, while I am sorry if this is hijacking a topic concerning the P-38 wing...)

[GregP]

Your drawings are always welcome, Tophe, even in an unrelated thread. :)

I think they should collected in a "Tophe" thread of their very own.

[Tophe]

I have organised threads of my own, with updates for my books, on the forum of what-if modellers ( http://www.whatifmodelers.com/forum//index.php?s=b48c69586c377929a62c001393b69cce&showforum=26 Tophe Twin-Tail part), so I think there is no need to have some here. But I am glad you, dear friends, give me new interesting ideas, that is why I am happy also coming here, reading, and I post a copy of what I archive on the other forum (saying the idea comes from here, and maybe that makes newcomers join).
Thanks again for your ideas.:)

[Tophe]

My twin-fuselage Corsairs were not exactly matching Lightning's requirement of a twin-boom Corsair, even if he was too polite to refuse them.;)
So I tried to imagine[8D]: why a twin-boom Corsair, not using the available parts on the Corsair production line?[?] I found 2 reasons, justifying this twin-tail-boom layout:
- doubling the power with a push-pull device, one solution being a twin-boom tail without the long shaft of the Do 335
- installing a big/long device above each wing, I don't know which one but military fans would know
The result is this::)
http://img.photobucket.com/albums/v670/Tophe2712/Extra1/r_F4UU-Corsair_l.jpg