Horton

[ACE-OF-ACES]

I was looking at the 'Evolution of Wing Design' dawning and I noticed something..

There were two things that happened between 03-24-1942 and 07-19-1943

1) The BMW P.3302 was replaced with the Jumo 004A
2) The inner portion of the wing was swept to match the angle of the outer wing

First things first..

We know for a fact that STORMBIRDS agrees that 'the wing' was swept to correct the cg.
We know for a fact that STORMBIRDS did not distinguish between inner or outer wing.

What we don't know for sure is how many times the Germans had to correct the cg due to heavier and larger engines than expected.

But looking at the 'Evolution of Wing Design' it appears they had to do it more than once due to all the changes in the engines

For example, take a look at the pictures dated 03-24-1942 and 07-19-1943 and note:

a) The Jumo 004A is wider and longer than the BMW P.3302.
b) The Jumo 004A and BMW P.3302 intake location is the same.
c) The Jumo 004A sticks out the rear of the wing much further than the BMW P3302.

What this means is:

a) The Jumo 004B version of the Me262 V1 has more weight (mass) behind the cg than the BMW P.3302 version of the Me262 V1
b) The Jumo 004B version of the Me262 V1 is heavier than the BMW P.3302 version of the Me262 V1

Which means the Germans would have had to add more weight (mass) in front of the cg to maintain the cg

This can be done in several ways

1) Add ballast
2) Change the design (shape) of the plane to add more mass forward

Adding ballast is a 'fudge' and is to be avoided, in that it just adds weight. Where as increasing the wing area adds weight, but at the same time increases lift to offset the extra weight of the heavier than expected engines.

With that in mind, it make sense that the Germans would sweep the inner wing to match the sweep of the outer wing, in that it not only looks better (aesthetics) but it adds weight forward of the cg to offset the Jumo 004B mass behind the cg, and adds more lift by increasing the wing area to offset the total weight increase

This observation not only agrees with STORMBIRDS statement that the Germans swept the wing to correct the cg, but could explain why STORMBIRDS did not distinguish between inner and outer when they said the wing design was changed (swept) to correct the cg.

Enjoy!

[tools4fools]

Indeed there is the change of engines and indeed the Jumo is heavier.

If the inner wing sweep was doone for weight is still debatable as you see in your nicely drawn comparisons:
The Jumo is a much larger engine, stretching out further behind the wing. If you look at your own drawing there is only a small part of the BMW after the center wing, almost entire weight is in front.
Not so with the Jumo, where approx 40% is in the back of wing center.

Radinger and Schick seem to disagree as well:
http://www.amazon.com/262-Entwicklun...N%3D3925505210

On 1 March 1940, instead of moving the wing backward on its mount, the outer wing was repositioned slightly aft; the trailing edge of the mid-section of the wing remained unswept. Based on data from the AVA Göttingen and wind tunnel results, the middle section's leading edge was later swept to the same angle as the outer panels

We know for a fact that STORMBIRDS did not distinguish between inner or outer wing.

In an article about plagiarism. They don't go into design and development details of the 262 really.

You really have to give up clinging to one single sentence on their site.
As said there's much more to design and development than one single sentence.
Start thinking open minded.
++++++

[ACE-OF-ACES]

Originally Posted by tools4fools

The Jumo is a much larger engine, stretching out further behind the wing.

Agreed as my drawing showed

Originally Posted by tools4fools

If you look at your own drawing there is only a small part of the BMW after the center wing, almost entire weight is in front.

Agreed as my drawing showed

Most of the weight (mass) of the BMW engine is FORWARD of the cg..

Which is explains why the OUTER wing was swept BACKWARDS

As in to put some weight (mass) behind the cg to counter the weight (mass) of BMW engine sticking out ahead of the cg..

Originally Posted by tools4fools

Not so with the Jumo, where approx 40% is in the back of wing center.

Agreed as my drawing showed

And is the essance of my point

As for 40%, I don't know if I would go as far as to say 40% of the weight (mass)..

In that assumes a uniform distribution of weight of the engine, framing, skin, etc.

But I think we can all agree that there is more weight (mass) behind the cg due to the replacement of the BMW with the Jumo..

With that said, we know..

The cg was 'set' for the BMW configuration
The cg will 'change' with the replacement of the BMW with the Jumo

The additional weight (mass) behind the cg has to be offset with weight (mass) added ahead of the cg.

Which is explains why the INNER wing was swept FORWARD

As in to put some weight (mass) ahead of the cg to counter the weight (mass) of Jumo engine sticking out behind the cg..

Hope that helps! S!

[tools4fools]

The additional weight (mass) behind the cg has to be offset with weight (mass) added ahead of the cg.

Indeed, nobody disputes this.

But the Jumo added a lot of weight forward too, remember?
Not only behind.
So correctly placed there is no need for additional weight.
In particular as the majority of weight seems to be forward in the Jumo 004.

http://deanoinamerica.files.wordpres.../jumo004_1.jpg

There certainly seem to be more bits n pieces in those 60% percent mounted forward on the wing.


Additionally check this out, from this book:
http://www.amazon.com/The-Luftwaffe-...123503&sr=1-12

Me262wing01.jpg

As we see Jumo jet, still straight inner wings.

So we are likely back to this:

On 1 March 1940, instead of moving the wing backward on its mount, the outer wing was repositioned slightly aft; the trailing edge of the mid-section of the wing remained unswept. Based on data from the AVA Göttingen and wind tunnel results, the middle section's leading edge was later swept to the same angle as the outer panels

++++

[ACE-OF-ACES]

Originally Posted by tools4fools

But the Jumo added a lot of weight forward too, remember?

I think you need to take another look at my drawing!

And note the overlay I did of the BMW on the Jumo (bottom center)..

First look at the overlay of the two engines ahead of the cg and note that the BMW and Jumo occupy about the same space ahead of the cg. Which means 'very little' NEW weight was added ahead of the cg due to the replacement of the BMW with the Jumo. That is to say the two almost cancel each other out. By candled out I mean subtract the BMW weight that was there from the Jumo that is now there and you will see that very little 'NEW' weight was added ahead of the cg

Now look at the overlay of the two engines behind the cg and note that the BMW and Jumo do NOT occupy the same space behind the cg. Which means 'a lot' of NEW weight was added behind the cg due to the replacement of the BMW with the Jumo. That is to say the two do NOT cancel each other out. By candled out I mean subtract the BMW weight that was there from the Jumo that is now there and you will see that 'a lot' of NEW weight was added behind of the cg

Which means they would have to add weight ahead of the cg to maintain the cg due to the replacement of the BMW with the Jumo

Hope that helps!

[Al Schlageter]

tools, you need to read the 4 volume tome on the Me262 by Smith and Creek.

[ACE-OF-ACES]

I realized my verbal descriptions can confuse some people, so I took the liberty of creating another drawing that shows what I was describing in my last post.. The red being the new weight the Jumo added.. I also added the swept wing area in Green.. See attached

Enjoy