DH Hornet nacelle frontal area?

BarnOwlLover

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I know it could be me, or most of the plans that I've seen may not be 100% accurate, but the Hornet's nacelles seem almost obscenely tight, especially in terms of width. Granted, they're not being faired into a single seat fighter's fuselage, since all that's behind the engine is the landing gear and an oil tank.

And I guess that's another question. Is the cleanliness of the Hornet's Merlin installation worth 100% perusing on a single-seater (assuming Merlin 60 or 100 series power), or is that a bit far fetched from a practicality standpoint?
 

tomo pauk

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And I guess that's another question. Is the cleanliness of the Hornet's Merlin installation worth 100% perusing on a single-seater (assuming Merlin 60 or 100 series power), or is that a bit far fetched from a practicality standpoint?

Depends on the fighter.
If the fuselage is of small height (like on the Bf 109, MC.202/205, Allison-engined P-51), the smaller height of the engine is a bonus. If the fuselage is taller (like on the Spitfire, Merlin Mustangs, Fw 190), the practical gain in streamlining from the less tall engine is probably very low.
 

BarnOwlLover

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The height of the Merlin installation on the Hornet seems to be similar to the Merlin powered Spitfire and Mustang. I was asking about width. The Hornet nacelle seems to be really narrow, even for a single seat fighter. Oddly, the Hornet's fusalge was claimed to be only about 10% or so wider/taller than a normal single seat fighter's (you have to put the 4x20mm cannons somewhere, and the nose is most practical on a single seat twin).
 

tomo pauk

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The height of the Merlin installation on the Hornet seems to be similar to the Merlin powered Spitfire and Mustang. I was asking about width. The Hornet nacelle seems to be really narrow, even for a single seat fighter.

I'd say that height of engines' installation was lower on the Hornet. Wrt. width - seems pretty similar on all of the three.

Oddly, the Hornet's fusalge was claimed to be only about 10% or so wider/taller than a normal single seat fighter's (you have to put the 4x20mm cannons somewhere, and the nose is most practical on a single seat twin).

There was a lot of normal 1-seaters that differed widely wrt. height of the fuselage, even if we discard the radial-powered types from the comparison. Eg. Hawker Hurricane's fuselage was much taller than what was the case with Bf 109. Thus the claim (made by whom?) of 10% difference is just an arbitrary number IMO.
 

BarnOwlLover

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Here's some images of the FMA IAe 30 Nancu, which uses the same Merlin 130 engines as the Hornet, and even a near-, if not identical, engine installation. Again,, the engine installation is clean and, maybe such a slimline engine to fuselage layout can be achieved on a single seater, given how slim both the Hornet's and Nancu's fuselages can be if you remove the 20mm cannon armament.

Ia30-04.png


FMA-IAe-30-Nancu-05.png


ia30-8.png


IAe30-01.png
 

ThomasP

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I may be mis-remembering, but I think I remember reading that the Merlin 130 (entire 100 series?) had the reduction gearing and gear box casing modified in order to allow the prop drive shaft to be located lower relative to the crank shaft than for the previous Merlin Marks. This allowed the prop drive shaft to be in a more centralized position, which position along with rearranged ancillaries allowed a more streamlined nacelle.

Maybe. I may be getting this info confused with another Merlin Mark or even a Griffon.

Merlin 100.jpg
 

BarnOwlLover

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I've never heard that before. I do know that the Merlin 130s had some ancillary items moved around and there were opposite rotation versions (same for the Packard V-1650-23/25 for the F-82) that had modified reduction gear casings to allow for the fitting of an idler gear to allow for opposite prop rotation. But I never heard that about the reduction gearing.
 

wuzak

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Depends on the fighter.
If the fuselage is of small height (like on the Bf 109, MC.202/205, Allison-engined P-51), the smaller height of the engine is a bonus. If the fuselage is taller (like on the Spitfire, Merlin Mustangs, Fw 190), the practical gain in streamlining from the less tall engine is probably very low.

You think the Spitfire has a deeper fuselage than the Mustang?

And the the Allison P-51 fuselages are much smaller than the Merlin P-51 Mustangs?
 

Steve Hnz

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The Merlin Mustangs had the wing lowered relative to the fuselage datum line by 3" compared to the Alison powered version from memory (or maybe it was 4"?) the radiator/intercooler duct was deeper than the Alison powered ones too which makes them look bulkier, so obviously it is more than fuselage cross section that influences how fast an aircraft can go. IIRC, the Spitfire had a smaller fuselage cross section than the Mustang.
 

nuuumannn

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There's a lot of ducting and so forth in the fuselage of single-seat fighters for the cooling system that gets tucked away in wings in the twins, which means the nacelles can be streamlined a bit more. The same with intakes, radiators and so forth. Here's a de Havilland Mosquito nacelle; it's pretty busy in there and it shows how much work was done on compacting the Hornet's nacelles.

51541664218_c9389ee8fa_b.jpg
DSC_4168

Here's a Spitfire XIV powered by a Griffon sans propeller. Very neat and not much more room for putting things but note the intake below.

51540634377_a15aac8c05_b.jpg
DSC_4141
 

BarnOwlLover

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I think it should be noted that the Mosquito still used updraft supercharger intakes. On the Hornet, these were inverted so they could be wing mounted. Only negative I can see with the Hornet's arragment is that intake air doesn't have a straight shot into the supercharger/carb like on other Merlin powered aircraft. Though it maybe made tropical filters easier to install (though I think later Merlin powered Spitfires, Mosquitos and Griffon powered Spitfires had integral tropical filters).

Also, the Hornet's cowling is much smoother than the Griffon-powered Spitfires, which has fairings to clear the valve covers (maybe a wider spinner would've helped the Spitfire and Spiteful?).
 

wuzak

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Also, the Hornet's cowling is much smoother than the Griffon-powered Spitfires, which has fairings to clear the valve covers (maybe a wider spinner would've helped the Spitfire and Spiteful?).

The Merlin Spitfires also had fairings for the valve covers, though not as pronounced.

I believe the reason it was don that way was to minimise frontal area and to give the pilot the best possible view.
 

spicmart

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According to Napier tests an annular/drum radiator installation with sliding gill cowling would be the least draggy. So the leading edge radiator of the Hornet was not the best in terms of drag even in conjunction with the narrow nacelles.
 

BarnOwlLover

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Ironically, the Tempest I and Fury I were the fastest of their types with leading edge wing root radiators. However, the ducted spinner Tempest with an annular radiator that Hawker and Napier worked on wasn't far off from the Tempest I in terms of speed.

I also wonder if the Hornet's nacelles were "insanely" narrow as far as being an aim for single seat fighter streamlining. Height-wise, I think they're good, but what about width or "girth" if you prefer. Because you don't just have to worry about the pilot fitting, but also some equipment. It'd be interesting to see how say a Griffon powered Spitfire, Spiteful, or P-51 D or H would compare in the width department.
 

tomo pauk

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According to Napier tests an annular/drum radiator installation with sliding gill cowling would be the least draggy. So the leading edge radiator of the Hornet was not the best in terms of drag even in conjunction with the narrow nacelles.
One wonders whether the people at Napier accounted for the drag of the wing section behind where the LE radiators go, when doing their math. With the annular radiator, there is the drag of that radiator + the full drag of that section, while with the LE radiators a good deal of the drag of that wing section is already accounted for with the radiator drag.
Meaning at the end that LE radiators have no disadvantage wrt. drag of a whole aircraft.

Another concern is that engines employing intercooler can increase the drag even if the installation is unitary and in annular form. Eg. the Ta 152, with an intercooled engine that dictated a bigger annular radiator (there was no separate radiator for intercooler, coolant and oil system*), have had 0.061 sqm worth of cooling drag, vs. 0.039 sqm on the non-intercooled engines as were the 213A and 213F - a 50+% increase of the cooling drag.
So just because the annular radiator was good for the Napier Sabre, it does not mean that it woukd've been a great solution for the 2-stage Griffon. Then we also have a thing of the aircraft with LE radiators, like the prototype Tempest I and Fury, as well as Hornet, being really fast already.

* coolant and oil were cooled via the heat exchanger, same as with other Jumo 213s, plus the intercooler was also cooled via the heat exchanger on the 213E
 

nuuumannn

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And I guess that's another question. Is the cleanliness of the Hornet's Merlin installation worth 100% perusing on a single-seater (assuming Merlin 60 or 100 series power), or is that a bit far fetched from a practicality standpoint?

I don't mean to rain on your parade or anything, but I do suspect you might be overestimating the slenderness of the aircraft's nacelle as a single point rather than taking the whole package and its aerodynamic impact. Whether the aircraft are single-seaters or twins, they need intakes, cooling systems, radiators etc and all this adds bulk and drag. In the Hornet and Namcu they moved that stuff to the wings. Bearing in mind that a single-engined aircraft has less overall surface area simply because it is single-engined means it will be aerodynamically cleaner. Moving the intakes etc to the wings would possibly help, but how much more speed might you get from that? As you've mentioned, the Hornet's intakes were in the wings, and yes, that could be done, but when this happens is the key thing as much as why and what for. The Hornet first flew in 1944, the Gloster Meteor was already in service and de Havilland's own Vampire already under development, not to mention advanced piston-engined fighters that represented the end of the line for the breed doing just fine without that ultra-streamlined nacelle. Take a look at pictures of the P-51H and Martin Baker MB.5, for example.
 

Shortround6

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Occupied-area-per-seated-person-and-the-definition-of-the-representative-measuring-points.png

That works out to just about 7 sq ft.
Granted you can trim it a bit and yes the head sticks up higher than the engine cowl, but since a Merlin was 780mm wide (not including Exhaust pipes) There was only so far you could go.
 

spicmart

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One wonders whether the people at Napier accounted for the drag of the wing section behind where the LE radiators go, when doing their math. With the annular radiator, there is the drag of that radiator + the full drag of that section, while with the LE radiators a good deal of the drag of that wing section is already accounted for with the radiator drag.
Meaning at the end that LE radiators have no disadvantage wrt. drag of a whole aircraft.

Another concern is that engines employing intercooler can increase the drag even if the installation is unitary and in annular form. Eg. the Ta 152, with an intercooled engine that dictated a bigger annular radiator (there was no separate radiator for intercooler, coolant and oil system*), have had 0.061 sqm worth of cooling drag, vs. 0.039 sqm on the non-intercooled engines as were the 213A and 213F - a 50+% increase of the cooling drag.
So just because the annular radiator was good for the Napier Sabre, it does not mean that it woukd've been a great solution for the 2-stage Griffon. Then we also have a thing of the aircraft with LE radiators, like the prototype Tempest I and Fury, as well as Hornet, being really fast already.

* coolant and oil were cooled via the heat exchanger, same as with other Jumo 213s, plus the intercooler was also cooled via the heat exchanger on the 213E
I dont think "Blanket" statements are very easy to make.

As has already been stated above, where you already have a very big fuselage, the annular system will work well because
you`re just making use of air which would have been shoved out the way of the aircraft anyway.

Something like a hornet clearly needs to have the diameter of the nacelles increased considerably to fit the
annular radiators, therefore increasing the frontal area, probably negating the benefits.

There are probably about two or three definitive layouts which will all work very well in the correct circumstances.

Just look at Reno Unlimited`s, thats been won by annular air cooled (effectively no different to a water cooled annular) and belly scoop systems (p51),
and planes like Sea Fury`s which have both leading edge and annular cooling systems at once.

I think the only thing you can conclude, is that stuffing a radiator out the bottom of the wing in a lump like a Spitfire is probably just about
bottom of the pack (although it can be very nicely done - see Supermarine Spiteful).

The FLIGHT articles (there are two) were comparing not just the annular radiator, but the later article in combination with a ducted spinner, and against the chin radiator version,
which is a pretty horrid looking lump at the best of times.

Certainly I have a lot of enthusiasm for the ducted spinners, although FW found them a bit difficult to get working on the 190 and ended up
with the more basic annular system we all know.

The annular installation here makes it pretty clear its making use of "dead space" in terms of fuselage diameter compare to the
approximate size of the actual engine (my blue lines added in). Very noteworthy here is the arrangement of the fins in the radiator matrix,
angled to align with the airflow. A lot of the benefits here will be down to excellent radiator matrix design too, not just where its fitted (as such).

Not dissimlar to that suggested by Kuchemann and Weber at Volkenröde. (yes, THE Joannah Weber, of Concorde fame when she ran off to
carry on doing maths for the British after the war)

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View attachment 673908
Do I undestand it right that your argument concerning the LE radiator also applies to the annular one (snowygrouch?

"air which would have been shoved out the way of the aircraft anyway."
"The annular installation here makes it pretty clear its making use of "dead space" in terms of fuselage diameter compare to the
approximate size of the actual engine (my blue lines added in)."
 

spicmart

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May 11, 2008
Regarding the issue of keeping air flow laminar on such an airfoil because of surface impurities and manufacturing quality can one assume that a smoother woodem surface offers an advantage over metal skin with rivets?
If so then how much better could a wood surface be dragwise?
 

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