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In the case of the wide, low radiator ducts, as used on the Spiteful, there was actually boundary layer thickening on the roof of the duct. The boundary layer air is not moving very quickly relative to the aircraft, so this reduced the effectiveness of the radiator. I can't recall exactly how much of the radiator the boundary layer covered, except that it was around 1/8 the depth of the radiator. Which is significant. This was from tests done of the production style Spiteful radiators.
Another solution was to provide a duct the entire length of the radiator duct, gong above the radiator.
Is this what you mean?
Bf 109 F
This shallow bypass air duct for boundary layer extraction is only available on the Bf 109 F.
Due to the increased flow velocity of the air flowing through, the channel only reduces the air resistance which the cooler housing generates.
As I understand it, it preserves the boundary layer but by reducing the flow through the radiator. So you need a much bigger radiator to do the same amount of cooling which defeats the purpose of it.So did the Spiteful also have this feature?
Messerschmitt gave up on this after the 109 for whatever reason.
Maybe the cost-benefit ratio was not worth it. It doesn't seem too complex though.
So did the Spiteful also have this feature?
Messerschmitt gave up on this after the 109 for whatever reason.
Maybe the cost-benefit ratio was not worth it. It doesn't seem too complex though.
As I understand it, it preserves the boundary layer but by reducing the flow through the radiator. So you need a much bigger radiator to do the same amount of cooling which defeats the purpose of it.
I was talking about the 109 set up, preserving the boundary layer worked but reduced the efficiency of the radiator. (that's how I understood it anyway).The problem identified for the Spiteful was that the boundary layer thickened in the duct and reduced the effective area of the radiator.
Part of the Mosquito was its cooling and general streamlining, but it was a bomber initially. Compare to a Lancaster, the "boundary layer was passing over a cheese grater by comparison.Anyway, the DH Mosquito's design lead on also to the DH Hornet, which had a level speed of around 487mph and was a study (at the time) of streamlining, particuarly of the Merlins 130/131's cowlings... all superb considering there was largely wooden structure involved, leading onto the first wood & metal being glued, DH using this new 'Redux' adhesive on the Hornet, all very new development that DH were pushing ahead with, and they then followed-on with the jet Vampire...
Comparing wood to metal, wood has less torsional strength, this just requires different methods of design and construction. There were some problems in the far east but more concerning adhesives than the actual wood.Yes the surface smoothness and ability to carefully design and control shape gave advantages to the wooden construction. I am not sure about the weight for strength as opposed to more conventional alloy construction. Not that WWII aircraft were designed for a long life span given a typical combat aircraft lifespan, but the wooden wonders of various sorts did not hold up well to adverse climates such as in the humid tropics. This probably limited the applicability of such airframes to a post war environment where longevity became a consideration.
Apparently the 109F's boundary layer bypass didn't pay off as duct stall wasn't eliminated and a larger cooler was seen as a an easier and slightly better performing option.
In late model piston engine aircraft air intakes on the leading edge for water or oil cooling were very common.I would expect (but do not know) the effect leading edge radiator ducting has on stall characteristics. Certainly they would have very different and probably not better flow over the top of the wing than a regular leading edge section. I would expect an increase in tail plane buffet near the stall at a minimum.
The radiators have to be sized to the engine and expected airflow.
Which 109 was designed to which engine?
The DB605 in the 109G made 15% more power 800 meters higher (thinner air) than the DB601N engine that the early 109Fs used.
You are going to need bigger radiators, it is just a question of how you arrange them.
The radiators have to be sized to the engine and expected airflow.
Which 109 was designed to which engine?
The DB605 in the 109G made 15% more power 800 meters higher (thinner air) than the DB601N engine that the early 109Fs used.
You are going to need bigger radiators, it is just a question of how you arrange them.