Could you have designed a better Warbird?

[kool kitty89]

Another point though, I don't think such intercooling arrangement if completely necessary. A kiquid cooled core type intercooler is easy to group together with the oil coolers and/or radiator in any case. (and the small increase in drag will certainly be less problematic than the drag and other problems resulting from the added fuselage bulk, weight, and complexity of such an arrangement)

However I don't think a 2-stage supercharger is even necessary. In the case of the DB-605 early models were already rated for fairly high altitude, though this decreased as the boost limit (and power output) increased. (high alt performance remained the same, or slightly improved with MW 50, but the higher boost could obviously only be obtained at lower altitudes)

The high altitude performance of these engines could not match the altitude performance of the high altitude 2-stage Merlin 61 (and similar V-1650-3) but it was fairly similar to the medium altitude rated 2-stage Merlins like the Merlin 66. However the altitude performance of these model Merlins was considered more than necessary and thus the FS (high speed) gearing was reduced somewhat to give a moderately lower critical altitude. (the V-1650-7, low blower or MS gear was unchanged)

However the DB 605 also was fitted with a larger single-stage supercharger (actually taken from the DB 603), this was used on the DB 605 AS and D models and gave high altitude performance fairly comperable to the V-1650-7.

Also, MW 50 (water-methanol injection) aclt both as an anti-detonant and a charge cooler (intercooling effect), and is used when an intercooler is most needed. (and at normal or cruise power an intercooler was not necessary)


I don't see why similar improvements couldn't be made to the Jumo's single-stage supercharger.

The WWII German inline engines (DB 600/601/605, Jumo 211, and DB 603) relied on lower boost preasures (less powerful supercharger needed) than their allied counterparts and somewhat lower operating RPM, but instead had a much larger displacement and managed to remain comperable in size and weight to their British and American counterparts.
The French used a similar approach with the Hispano Suiza 12Y and 12Z, and thus so did the Russians with their derivatives of the 12Y -M-105 etc-, and a similar with the unrelated Mikulin AM-35/38 and derivatives)

The Jumo 211 was somewhat bulkier than the Merlin, DB-601, or 605 (despit the 605 being larger in displacement). However the Jumo engine developed into the much more powerful (and somewhat heavier) 213, which was now comperable to the DB 603 or Griffon. This woould be the exception to the German engines, as the 213 ran at higher RPM and was actually smaller in displacement to the Griffon. Similarly it produced a relatively high power/displacement (for whatever that's worth). In this engine's case a 2-stage supercharger ie 213E/F, was needed for good high altitude performance.

 

[kool kitty89]

A note on the Sabre that I hadn'y known was that it used a double-sided centrifugal impeller on the supercharger (like the Whitle engine and sbsequent developments).

http://www.ww2aircraft.net/forum/engines/napier-sabre-engine-10528.html

 

[FLYBOYJ]

Excellent points all of you...let me try to reply to you one by one..

Flyboy: Aluminium. Steel too heavy, Wooden construction theoretically possible but not practical as Germany did not have enough skilled woodworkers, and also inadequate aircraft glue production facilities. See the history of the ill-fated Tank attempt to build a wooden reply to the British Mosquito. Of course the armour will be steel.

Did you know that you would have to make wing and landing gear attach points out of steel or magnesium? Heavier aluminum alloys such as 7075 were not were not around in the time period mentioned for the development of this fighter. Many WW2 aircraft used steel more than one would expect.

 

[kool kitty89]

How common was it to have steel wing spars?

 

[Burmese Bandit]

Flyboy: thanks for that input. I will put it to good use.

Koolkitty, AFAIK it was NOT common to have steel wing spars, however some Japanese aircraft towards the end of WWII had steel wing spars due to an acute shortage of aluminium.

Now regarding the reason why I have picked the 13mm as the weapon of choice for fighters versus the 151/20 for my Bomber destroyer...

Many of the arguments I will make will be seen in other threads, in particular the 'best armed fighter' thread. I believe the ideal fighter weapon for a gunfighter aircraft designed to deal mostly with other fighters is a weapon firing a projectile that is just powerful enough to get the job done, that fires the maximum amount of bullets in the minimum amount of time, that has the greatest projectile speed possible, and that is as light as possible. Oh, and that has the lightest ammo possible combined with the largest ammo storage possible.

And this points to the MG 131. Light enough at 17 kg per weapon, a good though not spectacular projectile speed, and fairly light ammo. Firing at 900 rpm with the potential for more. Bullet with explosive ammo, not as much either weightwise or percentage wise as the 20 or 30 mm, but adequate enough to kill Spits, Ponies, and Yaks. Only against the 37 would it struggle to be effective, and even then large numbers of hits could do the job.

 

[FLYBOYJ]

How common was it to have steel wing spars?

AFAIK it wasn't, at least not in WW2 - but the most inboard sections may of connected to a steel fitting. The problem here is dissimilar metal corrosion, but there is no getting around it.

Also consider some aircraft had their wings constructed conventionally and were skinned with corrugated aluminum and then had sheet aluminum riveted to that. I believe the P-38 and B-17 were constructed in such a manner.

 

[Burmese Bandit]

My next 'paper aircraft' design will attempt to design a better Stormovik than the Il-2, and also a better Tank killer on the Axis side. Back again when I have more time from work...

 

[fly boy]

Wanna try?

if I could I would and then it might look like a flying brick but whatever

 

[109ROAMING]

if I could I would and then it might look like a flying brick but whatever

......




......

 

[kool kitty89]

On the wing construction issue, I think a some of the composite wood/metal (and fabric) constructed Russian aircraft had steel spars. At least the I-16 did.
I'm not sure about other such aircraft (wooden winged Yaks and LaGG-3's or La-5/7's), but the wooden construction would reduce the dissimilar metals issue.
In the I-16's case the wing was actually construced with aluminum ribs and aluminum skin on the leading edge and center section with fabric covering the rest.

I believe the Hurricane also had steel alloy spars. (which makes sense given the extensive use of steel in the rest of its construction)

 

[Burmese Bandit]

Before I go on to my next paper airplane, I have decided, after digesting the excellent points made by various contributors to this thread, to redo the design of my uber 109. The engine will still be either a DB 605 or a Jumo 211, available in 1940/41. The rest of the design will stay the same. Where I have decided to make a change is in armament.

In the age of aerial gun combat, there was always a tradeoff between gun and ammunition weight, bullet speed, bullet weight, and amount of bullets thrown at a target in a given time. Ideally the fighter gun and ammo would weigh next to nothing, have enough bullets for a full minute of fire, shoot a hundred or more rounds a minute, recoil like a feather, and shoot shells with a speed and trajectory like a laser beam and which were also capable of bringing down an enemy with a single hit. But gun designers only achieve such results in their dreams.

I am determined to mount all my guns on the centerline, and if possible to avoid synchronization. Why? Well, synchronization is complex, and even the German electric ammo system leads to a loss of 10% in the rate of fire. The fleeting seconds - or even one second - which was the norm for target time inside the gunsight in air combat in WW II needed every round thrown at the target as fast as possible. And centerline gun installations were the most elegant solution to multiple guns mounted and sighted in one plane. (There are many threads explaining gun performance in WW II fighters - one of the best is the 'best armed fighter' thread very near this one...). And of course mounting all the guns on the centerline frees up the space in the wings for the fuel, which IMHO is the only place they should (for cg, space, and separation from pilot reasons)be.

The practical problem with my design is that while it's possible in theory to mount multiple guns in front of the engine, in the nose, firing through the spinner, in practice unless you have a multibarrel gatling, fitting more than four guns in the nose will be a problem due to the space needed for the helix belt drives carrying the ammo from the cg point to the guns in the nose. More than two drives per side will pose a problem, limiting the nose guns to four.

Since I'm going to have only four guns, I want to have guns that fire as fast as possible while having as heavy a shell as possible...and that are light, too. Oh, and I'll need a fairly short barrel gun to fit into the nose space. And, I believe, the answer is a little brother of the Mk 108 - a 20 mm short barreled cannon firing a lower power version of the 151/20 shell for a faster firing rate. And, of course, since it will use steel stampings and a blowback system, like the Mk 108, it should be much cheaper, too.

I believe a 30 kg gun weight for a 20 mm short barrel with 800 rpm is quite achieveable in the technology available in 1940/41. With 4 guns in the nose, that's 3200 rounds a minute, or 53 rounds per second. Using the excellent Luftwaffe estimates for rounds on target by an average pilot, that translates to 1.33 rounds per second on target, or 4 rounds in a 3 second burst.

The Fragile Yaks would probably go down with that, and serious damage if not destruction would be done to a somewhat sturdier Spitfire or a Mustang. A Lavochkin would suffer slightly less, and a Jug might survive....

Could the gun experts here, in particular the very knowledgeable Mr. Bronson, comment?

 

[FLYBOYJ]

On the wing construction issue, I think a some of the composite wood/metal (and fabric) constructed Russian aircraft had steel spars. At least the I-16 did.
I'm not sure about other such aircraft (wooden winged Yaks and LaGG-3's or La-5/7's), but the wooden construction would reduce the dissimilar metals issue.
In the I-16's case the wing was actually construced with aluminum ribs and aluminum skin on the leading edge and center section with fabric covering the rest.

I believe the Hurricane also had steel alloy spars. (which makes sense given the extensive use of steel in the rest of its construction)

Figure about a 500 hour life expectancy on anything made from wood. Its also harder to repair than aluminum.

 

[kool kitty89]

Before I go on to my next paper airplane, I have decided, after digesting the excellent points made by various contributors to this thread, to redo the design of my uber 109. The engine will still be either a DB 605 or a Jumo 211, available in 1940/41. The rest of the design will stay the same. Where I have decided to make a change is in armament.

The DB 605 wasn't available in 1940/41, I don't think the DB 601E was even entering service until 1942 with the Bf 109F-4. The Jumo 211F might have been available in that time frame.


And on the armament, to be clear, you are planning on having four 20 mm cannons firing through the spinner?

 

[Burmese Bandit]

Yes, Kool Kitty. In my previous post I stated that the design would start in 1941 with the aim of mass production by 1944. The DB 605, while not in service then, well well visible on the technological horizon.

Armament, yes. The short barrel short cartridge 20 mms should be equivalent in recoil to three long barrel ones. The Spinner will need a large hole, I would estimate 300 mm, but that can be faired.

 

[tomo pauk]

Hi Bandit al,

If I may add a few points for the Uber-190: instead of building a whole new aircraft (extra engine, new wings etc), I'd rather whip BMW engineers to either die or to produce a 801 with a decent supercharger. So, 1900+Hp available early in 1943, together with 2*20mm 2*30mm would make the new FW-190 a tough nut for anything allies could field in these days. B-17 P-47 included

Or mount that DB-603 in the 190, instead in many of planes of doubtful value.

 

[Burmese Bandit]

Tomo, the 30 mm had a whole bunch of problems. First, it could be used only as an inline engine mounted gun on single engine fighters - the reasons can be seen in many other threads on this site. Second, if you put it in the wings, the tremendous recoil would warp the wings and cause not only instability but inaccuracy of fire.

And the 109 was too physically small to take the 603.

Regarding superchargers, every country was going flat out to build the best. Britain and Rolls Royce just happened to be better.

 

[kool kitty89]

The Recoil of the MK 108 was not that great relatively speaking. (in fact, the dispursion on the Bf 109's engine mount was lower than that of the MG 151/20, probably due to the MK 108's recoil smoothing operating principal) but mounting in the outer wings will hgave inherantly worse accuracy at most ranges.

The DB 603 was more or less interchangeable with the Jumo 213, similar size, weight, and mounting/connection points. (the latter done intentionally by Jumo to compete in the 603's market)


The BMW 801's supercharger limited altitude performance, but was not a major limiting factor on max power output. If you want more power early on put more work into an 18 cylinder version. (ie 802)

That siad, careful design of the supercharger, with a well matched impeller and diffuser will result in a supercharger that sucks up less power with less charge heating. (hence the difference between the Merlin I/II/III/XII and Merlin 45/50 etc, and the similar change between the 2-speed Merlin X and XX)
Charge heating reduces the engine efficiency (higher heat, lower charger density) and reduces the maximum boost limit. (detonation occurs earlier)

 

[Burmese Bandit]

Yep, agree.

Looking in the 'best armed fighter' thread I see that a majority of posters and authorities cited seem to agree that centerline is the most efficient and deadly (to the enemy) way to go for fighter armament, with opinion split between bullet power and rate of fire.

 

[Burmese Bandit]

In designing a warbird - even a 'paper airplane' - one has to take many things into consideration, and before I go on to a new paper airplane, I'd like to explain that one of the factors in my design of a fighter and a bomber destroyer is the safety of the pilot.

Statistical studies have shown that there is a direct correlation between the overall effectiveness of an air force's fighter arm and the total number of hours flown, especially combat hours, by its pilots. No matter how many aces you may have in the beginning of a war, in a long war of attrition they will, sooner or later, die. They have to be replaced by new aces, and new aces are made, not born. They have to learn - mostly - the hard way, and that means surviving the first ten or thirty air combats...

And one of the keys to that survival, in addition to tactical awareness, speed and maneuverability of your machine, is battle resistance to enemy fire. This is why my designs have machinery, in addition to armour, behind the pilot's seat.

 

[Burmese Bandit]

Oh, BTW, I have just posted an explanation of 'Base Bleed' with regard to artillery (and other) types of shells in the 'best armed fighter' thread, and I think this will explain why I think it is a good design point to have the radiator exhaust of my planned uber 109 in the extreme tail - I believe it should give a speed advantage of between 2% to 5% over the Me-109's wing radiator design.