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Holtzauge

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  1. Holtzauge

    Developer Diary 210 - Discussion

    I can understand adding a Spitfire MkXIV is not a top priority for the moment since that involves a lot of effort. However, adding the option to have 25 lbs boost on the MkIX seems like the right thing to do given the plane set currently in the works.
  2. Is that like: Oh please yes! Or is it.........
  3. I get a substantially lower aspect ratio for Dr1 than that: Maybe you based calculation on the net wing area excluding the part in the fuselage? In that case you will get a higher number but for aerodynamic calculations you should include the wing area in fuselage if you use span squared/wing area. However, since both the Camel and Dr1 have fairly rectangular wings you can instead calculate using wingspan/chord in which case you will get a substantially lower number: I would say the Dr1 has an average physical aspect ratio (middle wing) of around 5.6 (I would not include aileron horns on upper wing in span based calculation) and the Camel 6.2. Fair point: My first assessment was based on the designated power on paper of 110 hp for Oberursel and 130 hp for the Clerget but I have come to understand that they were actually closer together in what they actually produced and with that in mind it looks like the Dr1 comes out on top there. However, when it comes to the turn performance I think the figures speak against the Dr1: Given the ballpark figure of total drag at maximum lift that I calculated in a post above shows that roughly 75% is due to the induced drag and only about 10% due to wing profile drag, I have a hard time seeing that the Dr1 should be able to top the Camel since the Camel beats it both in terms of the physical aspect ratio at 6.2 to 5.6 and in addition, given that the spacing of the wings are much closer in the triplane leading to a larger degree of mutual interference (hence a lower "corrected" aspect ratio) as the Munk formula shows, albeit for a biplane. BTW: when you say you can do a 360 degree turn in 8 s I assume that is the max momentaneous turn rate, i.e. with a speed loss? Roughly, what is the power and weight when you measured the turn and do you have an estimate for entry and exit speeds? The reason I’m curious about the details is that I plan to model the Camel and Dr1 in C++ so this type of indata would be very good indeed. Correction: Looks like the German 1917 Dr1 drawing I used was not to scale: Looks like both the Camel and Dr1 had an aspect ratio of around 6.2.
  4. Very interesting data on speed and climb performance Sgt_Joch and thanks for posting! When it comes to the turn performance, many people refer to the advantage the Dr1 had in terms of the thick wing profile and that that is supposed to have endowed the Dr1 with a substantial performance advantage in the turn but as far as I have been been to determine, it looks like this advantage was in Clmax only: The Camel's RAF15 comes in at about 1.4 while the Göttingen 298 is around 1.7 so a clear win for the Dr1. However, the wing profile drag at these Cl seems to be very similar at around Cd=0.03 so not big difference there. A caveat here is that this is data from airfoiltools at Re=1,000,000 which is a bit on the low side but I don't think going to a more representative 3,000,000 will change the conclusions. But what really sets them apart is the wing layout: The Camel has a bigger wing span and a larger wing area and this gives it a significant advantage in turn performance: As far as I have been able to determine, you can estimate bi- and triplane induced drag by calculating a corrected aspect ratio based on the physical span that uses this to estimate a "corrected" span and aspect ratio. This is outlined in figure 19 in Hoerner's book Fluid dynamic Drag page 7-12. I used this to do a ballpark analysis of the Dr1 drag in a max rate turn (see below) and it seems that the main drag is the induced drag which is all of circa 75% of the total drag while the wing profile drag is only 11% so its the Dr1's short span that really hurts it in turn performance and the thick wing profile in no way compensates for this shortcoming. Note that I have assumed a Clmax of 1.45 for the plane which is lower than the profile 1.7 but this is in line with what I would expect IRL I think and I based this on a similar percentage of profile/plane Clmax as a for the the NACA 23012, i.e. 1.58/1.35. Frankly, I was surprised by the results: I have always assumed that one of the Dr1's prime assets was a superiority in turning but it looks like the physics don't agree and even if the Camel had thin wings, the higher aspect ratio it has counts for more so it looks like the Camel comes out on top also in this case.
  5. Good point: I should have mentioned what engines and power I assumed: For the Camel a Clerget rated at 130 hp but delivering 126 hp and for the Camel an Oberursel II rated at 110 hp but delivering 122 hp. Those are the best estimates I have and under those conditions the Camel should beat the Dr1 in speed, climb and turnrate. That is AFAIK also the weakest engine for the Camel so if they choose anything else the Camel will do even better.
  6. To answer the question in the OP, IMHO the Camel should thrash the Dr1: Not punishing the Camel for its higher fuel capacity but assuming a similar endurance, i.e. the Camel at around 660 Kg and the Dr1 at 575 Kg, the Camel is faster, has a slightly higher power to weight ratio, slightly better wing loading and a substantially better aspect ratio. Sure, the Dr1 has a higher Clmax but that won’t save it in a turn contest since the Camel will have a better sustained turn rate (not radius mind you) due to the substantial aspect ratio advantage which counts for much more than the advantage the DR1 has due to the thicker Göttingen profile.
  7. Holtzauge

    Developer Diary 204 - Discussion

    With the caveat that I have not have time to test this latest release yet, the announcement about the improvements in dispersion and DM modeling only strengthens your position as the premier WW2 combat flight sim developer. Keep up the good work and thanks for a great update!
  8. Holtzauge

    Red Baron and the Damage Models

    @unreasonable: Great stuff and thanks for taking the time to compile the spreadsheet! A bit short on time before the weekend but some preliminary observations until then: First of all to me it looks like MvR's victory list confirms our suspicion that most victories were due to pilot, engine or a combination being incapacitated: Second, while some of the structural failures surely were due to battle damage, it's not unlikely that some pilots simply overloaded the structure when they came under fire: Does not require a vivid imagination to understand that you may dive or haul back on the stick a bit more than you would under normal circumstances when tracers are whizzing by your head..... Anyway I think your spreadsheet supports the notion that the wing shedding that is seen in RoF and now alas has been ported to BoX is not consistent which what one would expect IRL. Of course, one could always argue that 78 data points and only one pilot as input does not provide a strong enough statistical base om which to draw conclusions but I would be very surprised if gathering more data would result in any change of the trend. OTOH I think you mentioned that MvR was exceptional in that he got in much closer than was the general practice so there is that to consider as well: If you fire from really close you are more likely to hit center mass as in fuselage, pilot and engine while if you fire from longer ranges errors in aiming due relative motion, errors in lead and bullet drop estimation will inevitably lead to more spread meaning a higher incidence of unintended hits in wings. But that does not change the fact that now in BoX when I aim for the wings in earnest on a somewhat cooperating AI, it does not require that many rounds before the wings fall off and that definitely goes against what I would expect from an engineering perspective. @Chill31: On the subject of the increased rate on flamers late in the war, there is of course the question of correlation and causality and while MvR's personality may have developed in such a way that he pressed his attacks differently earlier on I find the connection to the introduction of incendiary ammunition as a more plausible cause for the increased rate of fires but for sure, a hardened attitude may have contributed as well.
  9. Holtzauge

    Fokker Dr.I Discussion

    I just tried with 5 m/s wind setting and it seems easier to avoid that little ground loop at the very end (if you land into the wind of course!). With no wind I find that if you anticipate it you can gun the engine very briefly together with opposite rudder and avoid it. Don't know how realistic that is compared to IRL though since the engine is pretty responsive in FC..... OTOH it seems to work even if you let it ground loop and drag the wing a bit on the wing tip skid at the very end as long as your speed is low.
  10. Holtzauge

    Fokker Dr.I Discussion

    Now that's interesting info and now that you mention it one can understand how it could happen if you have low control forces: If at high speeds you are able to deflect the aileron far and maybe even fully, you get a large force added with a long moment arm from the torsional center of the wing spar box which may overload it in torsion or twist the wing to unwanted angles of attack.
  11. Holtzauge

    Fokker Dr.I Discussion

    Interesting about the roll: If it's like you say the heaviest of the axis and there is no tendency to overbalance at any speeds one has to wonder why the designers at Fokker did not increase the horn balance area? Another question BTW: are there any weights in any of the horn balances for static balancing?
  12. Holtzauge

    Fokker Dr.I Discussion

    @Chill31 Thanks for all the Dr1 handling input: It's immensely interesting to get all the feedback on how the sim behaves in relation to the real thing from someone who flies the real thing and can compare. I've always been really impressed with what a modern state of the art sim engine like IL-2 can do in real time on a PC and it's impressive how close it seems to be to IRL in many aspects. However, that being said, it's also very interesting to understand a bit about where there are differences and it's good to hear that the ground looping tendency is not so pronounced IRL. Another thing I would be interest to know about is control forces: You wrote earlier on that holding the down elevator on the Dr1 can be tiresome if you fly for a long time. What about in roll? How much difference is it to deflect ailerons at low- and high speed? At what speed (if any!) do you feel hampered in roll? Some German WW1 designs had the characteristic horn balances (e.g. DR1 and D7) which I guess go some way to alleviate increasing stick forces with higher speeds but is there a tendency for overbalance on any axis? Also, how is the Dr1's IRL control feel in terms of balance between axis? Are the controls (pitch, roll and yaw) nicely balanced in relation to each other or is there a tendency for any axis to become more heavy with increasing speed?
  13. Holtzauge

    Changes in FM and DM?

    No hurry unreasonable and grab a glass of whiskey to combat the cold: Maybe it won't cure you but you will feel better anyway!
  14. Holtzauge

    Changes in FM and DM?

    Sounds interesting: Would also be nice to know how often there was a fire IRL: Those tin can fuel tanks would be easy to hole and sparks from FMJ strikes on metal or tracer could of course set it on fire but OTOH I think it was nice that this feature was not overused in the ROF DM. But again, would be interesting to hear how often the Red Baron saw his victims go down in flames. For sure: Battle damage may lead to the wing twisting or bending out of shape but if you look at the Dr1 section I posted above it's a box structure which carries both bending and torsional loads and it would require a whole lot of FMJ damage close together for it to lose structural integrity since there are a lot of alternative load paths around local damage. Same goes for the braced wing: Your best bet is to hit a strut, brace wire or brace wire fitting and those are pretty small targets while there is an awful lot of canvas and ribs that you can shoot out without affecting the wings integrity.
  15. Holtzauge

    Changes in FM and DM?

    Yup, I saw the handgun clip and it was fun to see: Quite often in these forums OP is a misused term but it certainly seem to be the right word in this case! But, as you say it's probably just a case of work in progress so they will most likely fix it later on. On the subject of susceptibility to battle damage, I found the below attached section of a Dr1 wing section which looks pretty sturdy and you would need quite a few rounds before that box section looses it's structural integrity to the point that it fails in bending or twists to the the point of failure at moderate g-loads. Of course the Dr1 is a bit different in that the spar box carries bending and torsional loads while in most other contemporary bi- or triplane designs the spars just carried compression/tension loads due to the strut/bracing wire design but the fact remains that you either need some very lucky shots that severs bracing wires, fittings or struts because most parts of the wing will just soak up FMJ rounds without compromising structural integrity meaning wing losses should be rare indeed.... Interesting info about MvR's claims records: Did not know that that backs up a lower frequency of wing shedding but IMHO common sense would also support that the pilot and engine are the largest "single point of failure structures" you can hit just as MvR's own demise proves.
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