Lancaster - the exhaust theory

[chek]

My theory, that is the theory what is mine, is that Lancasters are thin at one end, much, much thicker .... sorry wrong theory.

Lancs are back in fashion and one of the weathering questions is: do they have three or four exhaust stains across the top wing?

After studying my refs (not that comprehensive - a Koku fan, two ..at Wars and some assorted mag articles)

it becomes apparent that both cases are true.

But why?

My guess from the evidence I have to hand is that with the wartime flame dampers acting like ram air tubes, the outer

exhaust smoke mostly went under the wing, leaving three stains on the upper wing. The light greyish brown deposits

from the leaded fuel also made a right mess of the cowling sides and wing fairings, but that was often overlaid with black

carbon smoke deposits which built up over time.

On post war models, the unshrouded manifolds with undirected smoke led to there being all four stains on the upperwing.

I'm not saying this is written in stone at this stage, just that it seems to fit the photo evidence I have to hand.

And someone with a better library might come to a different conclusion.

[thx6667]

My own impression from making a few Lancs is that the "three exhaust" stain is the more common, there is some staining on the "fourth" but very faint.

I'd got with three.

[tedtaylor]

My theory, that is the theory what is mine, is that Lancasters are thin at one end, much, much thicker .... sorry wrong theory.

Lancs are back in fashion and one of the weathering questions is: do they have three or four exhaust stains across the top wing?

After studying my refs (not that comprehensive - a Koku fan, two ..at Wars and some assorted mag articles)

it becomes apparent that both cases are true.

But why?

My guess from the evidence I have to hand is that with the wartime flame dampers acting like ram air tubes, the outer

exhaust smoke mostly went under the wing, leaving three stains on the upper wing. The light greyish brown deposits

from the leaded fuel also made a right mess of the cowling sides and wing fairings, but that was often overlaid with black

carbon smoke deposits which built up over time.

On post war models, the unshrouded manifolds with undirected smoke led to there being all four stains on the upperwing.

I'm not saying this is written in stone at this stage, just that it seems to fit the photo evidence I have to hand.

And someone with a better library might come to a different conclusion.

The reason there are three mainly is because of the anhedral of the outer wing, the engines are hung vertical which means that the outer exhaust is slightly lower than the leading edge of the wing so not so much exhaust goes above the surface

[chek]

The reason there are three mainly is because of the anhedral of the outer wing, the engines are hung vertical which means that the outer exhaust is slightly lower than the leading edge of the wing so not so much exhaust goes above the surface

Agreed Ted.

But although the geometry of the wing doesn't change, the number of overwing exhaust tracks does.

Four seems to me to be more prevalent on post war models, which are those without the flame dampers.

At least that's my deduction for the difference, but that might be faulty due to my limited available evidence.

It's only a minor point, but it came to mind when studying photos of postwar coastal command Lancs, as I took a fancy to having a black wartime and white peacetime Lanc pair on the shelf.