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JtD

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  1. Gimpy sounded as if the slats as such create drag ("extra wing slat drag"). Wing slat drag doesn't exist as such. Besides that, the idea behind them is the creation of extra lift. Other ways of achieving the extra lift could be a larger wing, deployment of flaps, a different airfoil or wing shape and so on. Slats don't create more drag than any comparable means of increasing lift. So I think Patheras comment on that is more than fair. However, the main point of the slats on the Bf109 is to maintain lateral control at high angles of attack, not to significantly increase overall lift
  2. For sustained turn consider span loading. The square of it is equivalent to induced drag. The Tempest needs about 15% more power to sustain the same turn. The power you're assuming might be representative for sea level, but at 10000ft the V1650-3 at 67" produced ~1700hp, the Sabre IIa at 9lb ~1800hp, IIb at 11lb about 2000hp. 10000ft is much more representative for altitudes below 15000ft than sea level figures are. If you feel like using an power average 0-15000ft at typical turning speeds, you're around 1650 for the 1650 and at 1850/2100 depending on boost for the Sabre II.
  3. If you just go with wing area, weight, span and power, there's very little to chose between a P-51B V-1650 and a Tempest V Sabre IIb 11lb at lower altitudes. But the Sabre IIb at 11 lb is probably not what the comparison refers to, and with a Sabre IIa at 9 lb it's already is not that competetive anymore. This is before looking at aerodynamic qualties in more detail, which I think would shift the picture a little bit more in the P-51's favour, even if only a little.
  4. The distribution unreasonable posted doesn't take accumulated damage into account. It is single hit = kill probability, which isn't 100% accurate, but actually not too far off the real thing. Eventually, the hit that kills, in particular with AP or API rounds, is often decisive on its own. May it be pilot, controls, engine or other systems. This assumption, as he posted, has its flaws (it doesn't work if you have redundant systems, like a co-pilot), but was still considered good enough for real life damage analysts, which preferred it over any other model. What is also good with th
  5. Regarding the '75kg bombs' around here, one out six has been exploded, five of them had the detonator(s) removed and were transported off site. They were evidently found while digging on major construction sites, disarmed on site, and pictures of them in their rotten state were taken and published. It's also said there are still several hundreds of failed bombs in the area, both according to US data, and common sense estimate by known bomb failure rates. What we didn't have, ever, were terrorist cells with 3 tons of explosives in their basements.
  6. Yes, it's amazing. I also kind of expected to have pictures of 0.50 jump at me when just going through the regular literature. But somehow, it's nearly always freshly polished machines on a nice summer days... Might be worth going through this topic: https://ww2aircraft.net/forum/threads/battle-damaged-aircraft-of-ww2.15431/ Lots of big caliber damage, but certainly also 20mm HE stuff in there, and since you've been wondering about HE damage as well, might be intersting. WRT 13mm HE - this is not really something you do for structural damage, you do thi
  7. The difference between the two guns is the barrel, which could be changed by a one eyed mechanic without thumbs. (As mentioned in the manual of the Bf109F-2, even though they say it takes 17 minutes for two trained mechanics to do it, because the gun had to removed and reinstalled in order to do that.)
  8. I found this as an example for skin thickness distribution on a wing. This is from a general aircraft design book of the late 1930ies. Basically the bending forces as well as the aerodynamic (pressure) forces are mostly taken by the ribs and spars, and you're supposed to reduce distance between them if loads get to high. You don't necessarily make skin thicker. So essentially, the skin doesn't have to take a lot of forces, with the exception of torsional moments on stressed skin designs, but this still allows it to be reasonably thin. As said above, US aircraft often used somewhat thicker
  9. The calculation form still has the powers the basic form has, it is just more computer friendly by braking them down into multiplications. Got me, too, for a moment. But this is a 1981 paper, they used buildings instead of smartphones to get some decent computing power. a*x³ + b*x² + c*x + d = d + x(c + x(b + x(a))) - so don't let it confuse you. From what I gather, the 2024-T3 aluminum would be the one most typical for the era, as it or similar alloys were used on most (US) aircraft of the time. The other two alloys are of later date. So the good news would be, that we
  10. Where? Given that the limiting velocities and the HLVD are easily calculated, wouldn't it be easier to check what speeds are relevant in the first place? According to the model you can simply use projectile speed times cosinus impact angle to determine v*, and as long as v* is bigger than v3, use HVLD. Which as far as I can tell you've calculated properly (for a 0.09" plate). At 400 yards, you should be at somewhere around 2400fps projectile velocity, as 1500fps is the limiting v3, anything less than 50° off the perpendicular will produce HVLD, in the range of about 0.6
  11. Differs greatly. Japanese aircraft for instance typically use a lot thinner skin than US aircraft, German/British ones are somewhere in between. And then there's the size of the aircraft, the type, particulars of the part and so on. Some info I found quickly because I still remembered where i read it: The Bf110 wing skin ranges from 0.8mm to 2.1mm in thickness. For the Fw190 it appears to be a little bit less, couldn't find the exact range, but 1mm is not wrong - there are bits that are thicker and bits that are thinner, that I know.
  12. I'm in the 'lets acknowledge a problem and investigate further' camp. For two reasons. One, I find all this very interesting. Two, if we can come up with not only the problem, but also a solution or even just a few steps towards a solution, we make it a lot easier for the devs to implement it. Which means a more accurate simulation, sooner, for us.
  13. There's about a dozen reports floating around in the topic by now. Which one are you referring to? The design manual for impact damage tolerant aircraft structure? Feel free to adjust the hole size a figure you find more suitable. 2 inches? 50 holes - about 580 km/h. Just keep in mind that it's not the maximum damage size (i.e. cracks), but the hole size. Feel free to go through the sources and come up with your very own ballpark. There's nothing wrong with assuming 1 inch diameter, it's totally within the ranges given. Maybe not when fired at from directly behind, but then there'd
  14. How do you get that idea? I'm interested in finding out how much loss of speed is a realistic expectation. I just don't care if it is for the one example you appear to claim to be the only relevant one, or any other number of hits. Speaking about how much, a 20" diameter jagged hole increases cd of a 24m² reference area by about 0.002, a plain one about 0.001. One on top, the other one on the bottom of the wing. Or about 10%-15% drag for a German WW2 fighter in high speed config. Speed loss about 5%-7%. In terms of damaged area about 400 times of what you can expect for a 0.50 (1 i
  15. Only that the DM isn't OK for 49- rounds, either. So what's your problem? Personally I am more interested in what a few rounds of 0.50 do because that's more relevant for a proper damage model on the bottom line. To each his own, I guess.
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