[betelAIR]

From Germany, 1935:

 he70.jpg (104.71K)
Number of downloads: 118

 he70_1.gif (71.02K)
Number of downloads: 83

 Heinkel_70.jpg (41.87K)
Number of downloads: 94

 Revell_He70_cover.jpg (60.58K)
Number of downloads: 95

Info here.

This post has been edited by betelAIR: 15 March 2007 - 07:27 PM

[URF]

I've been thinking of this one before: But before starting I'd like to know (approximate) wing airfoil(s) and propeller RPM (and gearing if any).

[betelAIR]

Here's stuff on the BMW engine:

 he70spec2.gif (25.05K)
Number of downloads: 50

Here's a bit more general info:

 he70spec1.gif (24.01K)
Number of downloads: 47

I couldn't find the airfoils, but this is close: the wing is an elliptical planform. It is the same type of wing used in the Spitfire.
And get this: in the early 30's, Heinkel and Submarine (the makers of the Spitfire) exchanged parts and plans of the 70:
http://www.flug-revu...902/FR9902g.htm

[URF]

That's enough data to start a feasibility study. The wing looks tricky, but I'll start tomorrow.

[betelAIR]

Just to let you know, your Nord Martinet is one of my favorite oldies. Go get 'em.

[HoHun]

Hi Betelair,

>And get this: in the early 30's, Heinkel and Submarine (the makers of the Spitfire) exchanged parts and plans of the 70:
http://www.flug-revu...902/FR9902g.htm

Some other German magazine recently ran an article quoting the Heinkel He 70 as strong inspiration for the Spitfire wing, backed up by research done by one of Mitchell's descendants. I don't remember the details, but the article left little doubt that the similarity was not just an example for convergent evolution. The Spitfire wing did however differ in some points, such as basic construction (using a single-spar concept developed in Germany) and wing section (following Supermarine's own ideas).

Though some people get all excited about this, I think it's completely normal since aviation had always been an international business.

(Messerschmitt used Handley-Page slats on the Me 109, too, and of course the Me 109 made its first flight with a Rolls-Royce engine :-)

Regards,

Henning (HoHun)

[hole in the ground]

Hi Betelair,

>And get this: in the early 30's, Heinkel and Submarine (the makers of the Spitfire) exchanged parts and plans of the 70:
http://www.flug-revu...902/FR9902g.htm

Some other German magazine recently ran an article quoting the Heinkel He 70 as strong inspiration for the Spitfire wing, backed up by research done by one of Mitchell's descendants. I don't remember the details, but the article left little doubt that the similarity was not just an example for convergent evolution. The Spitfire wing did however differ in some points, such as basic construction (using a single-spar concept developed in Germany) and wing section (following Supermarine's own ideas).

The reason that the SUPERmarine Spitfire's wing is the shape it is, is because it was originaly designed for only 4 machine guns. The air ministry subsequently changed there minds and required 8. So mitchel simply stuck them further out along the wing. This transformed a tapering wing into an elliptical one. That an elliptical wing has a very good spanwise lift distribution is pure fluke for the Spit.

Im not sure why Heinkle opted for elliptical wings...
I reckon that there would be some similar kind of development thought behind it.

I thought that the spitfires wing was also made using a monocoque technique, to allow for it to be lighter and contain greater fuel and ammo. I know that the early marks had problems with control reversal at high speeds, i just assumed it was from such wing construction.

[HoHun]

Hi Hole,

>The reason that the SUPERmarine Spitfire's wing is the shape it is, is because it was originaly designed for only 4 machine guns.

Hm, I know that the 8-gun specification came only after the contract for the Type 300 (that became the Spitfire), but this is the first time I hear the ellipical planform was determined by the extra guns. Was there ever a plan for the Type 300 with tapered wings? The earlier Type 224 at least was built with such wings, it seems.

>Im not sure why Heinkle opted for elliptical wings...
>I reckon that there would be some similar kind of development thought behind it.

Not at all! It was not Heinkel personally, but his star designers, the Günter brothers. They had built their first aircraft for Paul Bäumer, the Bäumer Sausewind (roughly "Swift-as-the-wind") sports plane - without any wing guns, of course :-) -, and they certainly meant to exploit the good lift distribution you quoted.

Interestingly, the Günter brothers later abandoned the elliptical wing shape, approximating it with straight-edged sections in the later He 111 variants to simplify production. I'm sure Mitchell was aware of the aerodynamic benefits of the elliptical wing - after all, he could have reaped similar mass-production benefits as the Günters did by adopting a straight-edged approximation of an ellipse.

>I thought that the spitfires wing was also made using a monocoque technique, to allow for it to be lighter and contain greater fuel and ammo. I know that the early marks had problems with control reversal at high speeds, i just assumed it was from such wing construction.

It's a monocoque wing with a torsion box nose section in front of the single spar. I think it was developed in Germany in the 1920s for sailplanes and light planes. I don't know if Mitchell learned about the technique personally on his visit to Germany, or if it became an internationally common technique before that. I believe Messerschmitt used that construction technique for his early light-weight, wooden, two-place M-17, and he certainly used it for the Me 109. (The Spitfire used a different technique for the main spar, however, with a leaf-spring like construction rather than a solid light-alloy spar.)

The control reversal problem persisted through all versions with the elliptical wing (not the F.21 and derivatives, though), and from Mike Crosley's "Up in Harm's way", I'd say it was only fully understood after WW2. The Me 109 with its similar wing construction seems to have been affected to a certain degree, too, though at high speeds it tended to display aileron overbalancing rather than control reversal. The Spitfire was good for higher absolute dive speeds than the Me 109, however.

Regards,

Henning (HoHun)

[URF]

Landing gear is complex, but doable.
Flaps will be a problem as it's an inverted gull wing but single piece flap, so it'll look like two.
Flies pretty much OK.
Only cockpit photo I've found is very low detail, so the only thing it shows is that the pilot is offset a bit to the left. But I guess we don't want instruments in km/h and m, do we, so it's not going to be an exact cockpit anyway?

Attached File(s)

•  he70a.jpg (23.16K)
  Number of downloads: 46

[URF]

Wing planform adjusted.
Made a simple panel. For lack of better data, it will have to suffice.
Performance improved a bit with the smoothing of the fuselage. This does not handle like a sluggish airliner.

Attached File(s)

•  he70_b.jpg (38.58K)
  Number of downloads: 42
•  he70_panel1.jpg (32.97K)
  Number of downloads: 37