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4.006 DM Discussion

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5 hours ago, emely said:

You probably won’t like the music, but maybe the video will be understandable

 

The message is clear, and international:

 

If your wife owns a pair of scissors, use internal bracing.

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I think @catchov made a good reference about going down the rabbit hole earlier on but here is some more input from the Mad Hatter :wacko::

 

Comparing the Dr1 and Camel, I made a point earlier on about how it from a DM perspective should not matter much if the spar area A is divided into 4 x A/4 as in the Dr1 wing or in a solid block A as in a Camel. In addition, @ZachariasX has already done a good job explanation this with a D7 example but let’s revisit with some numbers:

 

The Dr1 central box spar has 4 spar elements roughly 1.5 by 5 cm meaning circa 30 sqcm spar area in total (Much less further out though!). The Camel has a forward spar circa 4 by 8 cm and a rear spar circa 5.5 by 5.5 cm so in total circa 62 sqcm. However, they are hollowed for lightness so say 75% of that or 47 sqcm. So still more spar area in the Camel any way you look at it. And that is just the upper wing mind you!

 

We can continue to discuss this until hell freezes over but without a detailed understanding of how the DM actually works we are fumbling in the dark. However, we CAN see the results and the only thing that counts is if the Entente wings are falling off more often than the Central wings due to battle damage in general and in a large sample.

 

A lot of people have had input on this including myself and nothing so far convinces me that there should be a large difference between them but rather that they should be about the same and as I see it, for the damage cause by repeated 90 degree deflection shots there should statistically in a large sample of cases not be that much difference. So if the D7 and Dr1 absorb substantially more battle damage than Camels & SPADs without the wings falling off then IMHO the DM model needs tuning.

 

So to sum up: Entente and Central battle damage resistance should be ROUGHLY the same. Both should be tuned so that wings falling off due to battle damage is rare.

 

That is my takeaway from this discussion.

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Posted (edited)

The structural element of a cantilever is the spar.  I have no problem with using spar size as a basis to determine damage resistance in this instance.

 

The structural element of a belt and braces biplane are the flying wires NOT THE SPARS.  

 

 

 

 

 

Hit the wings all you want, in either case, but only use that as a basis of attacker shooting accuracy, NOT structural integrity. 

 

For cantilever winged aircraft, hits to the wing determine the basis for calculating the probable potential for structural failure of the spar.

 

For TRAD BIPLANE winged aircraft, hits to the wing, determine the basis for calculating the probability of hitting and breaking a WIRE, NOT THE SPAR.

 

The wires might look puny, but they are THE main element that resists G loads in trad, thin wing biplanes.  The spars, on a trad biplane are not designed or built to withstand G loads without additional support, spars provide structural rigidity and stiffness to a wing but without assistance (wires) they would be totally incapable of doing the job that they perform.

 

SO,   Let’s not chuck the baby out with the bath water, lets just reconsider and recognise what is actually structurally important about the different design concepts, spars for cantilevers and wires for thin wings.

 

If you shoot the wings of a Fokker D.VII or DR1 then you stand X amount of chance of hitting and damaging the SPAR and probability theory determines the consequences.

 

If you shoot the wings of a Spad or Albatros then you stand  X amount of chance of hitting and damaging the WIRES and probability theory determines the consequences.

 

Really it’s not so difficult, or radical, it just has to be recognised that it isn’t possible to compare two different and competing designs by only considering the strongest element of one and not the other.

 

Hitting and severing a wire might be more immediately terminal than a bullet in a cantilever box spar, but hitting a small wire is infinitely more difficult, more a question of luck than judgement, and designers sometimes fitted an extra failsafe, by  way of doubled up wires, to offset that likelihood.

Edited by HagarTheHorrible

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Aaaaand we are back on square 1!

 

I'd like to argue about the FC DM model please!

 

 

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Nice article about Mikael Carlson's DVII here.  He says it's test to destruction limit (undamaged, presumably) was found to be 13Gs :o: in US tests but does not give a source.

 

Details of spars etc aside, I find it implausible that a plane with a limit of 13Gs would be broken by the same number of bullets as a Camel or SE5a with limits of perhaps 7G ish. 

 

https://vintageaviationecho.com/fokker-d-vii/

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18 minutes ago, unreasonable said:

Nice article about Mikael Carlson's DVII here.  He says it's test to destruction limit (undamaged, presumably) was found to be 13Gs :o: in US tests but does not give a source.

 

Details of spars etc aside, I find it implausible that a plane with a limit of 13Gs would be broken by the same number of bullets as a Camel or SE5a with limits of perhaps 7G ish. 

 

https://vintageaviationecho.com/fokker-d-vii/

 

Interesting ..........That is one nice looking DVII as well .....

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Posted (edited)
26 minutes ago, unreasonable said:

 

 

Details of spars etc aside, I find it implausible that a plane with a limit of 13Gs would be broken by the same number of bullets as a Camel or SE5a with limits of perhaps 7G ish. 

 

https://vintageaviationecho.com/fokker-d-vii/

 

A Camel spar wouldn’t stand up to 7 G, it would probably struggle with  1 or 1.5 G, what allows it to withstand about 6.8 G’s is the supporting structure around it i.e the wires.  I think ZachariasX got it right.  We all think of the spars as absorbing the extra G forces, in a vertical manner, because that’s the way the wings come off, but actually the upper spar  main contribution is against folding, by compression, about the bottom hinge point of the flying wires.  The upper spars need to resist flexing and compression, NOT bending due to added G forces, the wires do that.

 

If you read my earlier post, and I appreciate I might not have been very clear you might understand better.

 

Cantilever winged aircraft should be judged by their spars, that is the main structural element  of their wings. The probability theory, as is, might work well for them, BUT.......

 

Traditional wing biplanes should be judged by their wires, NOT THIER SPARS.   There doesn’t need to be any radical change in the DM, the only thing that needs to change is that the probability theory calculates the probability of a hit to a wire, instead of a spar, for traditional biplanes and scores the wings accordingly. 

 

 

Edited by HagarTheHorrible

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Posted (edited)

@unreasonable: But the German design rules stated that the design limit loads were 6 g in 1917/18. Which is about the same as the British. Or are we going to go with a test from a batch example of n=1? Design rules or a single test?

 

Wait: Of course! The DVII was designed using superior Teutonic pine from the deep Bavarian forests whereas the poor British had to do with Oregon pine felled by this fellow:

 

 

Edited by Holtzauge
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23 minutes ago, unreasonable said:

Nice article about Mikael Carlson's DVII here.  He says it's test to destruction limit (undamaged, presumably) was found to be 13Gs :o: in US tests but does not give a source.

 

Details of spars etc aside, I find it implausible that a plane with a limit of 13Gs would be broken by the same number of bullets as a Camel or SE5a with limits of perhaps 7G ish. 

 

https://vintageaviationecho.com/fokker-d-vii/

 

Paging @AnPetrovich

 

I can already see the changelist for 4.007:

 

Following community feedback we carefully redid all the wing strength testing for all the Flying Circus planes and have made the following changes:

Central:

  1. Fokker Dr.I, Fokker D.VII and Fokker D.VIIF wings made stronger;

  2. Albatros D.Va lower wing spar now correctly vibrates during dive and correctly disintegrates entire airframe when touching the stick;

Entente:

  1. No changes.

 

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1 minute ago, Holtzauge said:

@unreasonable: But the German design rules stated that the design limit loads were 6 g in 1917/18. Which is about the same as the British. Or are we going to go with a test from a batch example of n=1? Design rules or a single test?

 

Wait: Of course 1 The DVII was designed using superior Teutonic pine from the deep Bavarian forests whereas the poor British had to do with Oregon pine felled by this fellow:

 

 

 

If you are talking about the limits given in NACA 145 those are the design minimum requirements, not the results of tests.  As I said, he does not give a source and it would be very interesting to see what it was.  

 

BTW Monty Python videos are not an argument.  

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Posted (edited)

I can already see the changelist for 4.007:

                                              

                                                                       Following community feedback  Fook off...all of you

Edited by J5_HellCat_
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3 hours ago, Holtzauge said:

The Dr1 central box spar has 4 spar elements roughly 1.5 by 5 cm meaning circa 30 sqcm spar area in total (Much less further out though!). The Camel has a forward spar circa 4 by 8 cm and a rear spar circa 5.5 by 5.5 cm so in total circa 62 sqcm. However, they are hollowed for lightness so say 75% of that or 47 sqcm. So still more spar area in the Camel any way you look at it. And that is just the upper wing mind you!

 

I don't think (emphasis on think) that is right...I beam math gives exponential strength increases as the beam depth increases.  For example, if I take a 3 inch deep spar and make it 4 inches deep, it will have about twice resistance to bending.  

 

The DrI has a depth of 4 inches (10.6 cm), you have to include the web in the strength.  Doubling the web thickness of the web has less impact than adding 10% to the spar depth, so it is not just about how much material is in the spar.  Total depth and total width play the largest role spar strength.

 

I think that is why they have calculated a much greater strength of the Fokker spars vs others.  The flying wires contribute a lot the smaller wings strength though, over the spar depth.  I bet that is why they are more fragile!  The flying wires aren't incorporated in the strength, thus the spar is the only thing calculated as bearing the load.

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Posted (edited)
16 minutes ago, Chill31 said:

 

 

I think that is why they have calculated a much greater strength of the Fokker spars vs others.  The flying wires contribute a lot the smaller wings strength though, over the spar depth.  I bet that is why they are more fragile!  The flying wires aren't incorporated in the strength, thus the spar is the only thing calculated as bearing the load.

 

If that is true why are the undamaged limits of the braced wing planes broadly in agreement with the sources?

 

What I think they have done is not to calculate the mechanics of spars, forgetting about the wires, but they started with an undamaged result for the whole plane based on tests etc, then made rather ad hoc calculations with respect to how much the implied G limit on the "spar" is reduced by damage in a particular place.   

 

 

Edited by unreasonable
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1 hour ago, HagarTheHorrible said:

 

A Camel spar wouldn’t stand up to 7 G, it would probably struggle with  1 or 1.5 G, what allows it to withstand about 6.8 G’s is the supporting structure around it i.e the wires.  I think ZachariasX got it right.  We all think of the spars as absorbing the extra G forces, in a vertical manner, because that’s the way the wings come off, but actually the upper spar  main contribution is against folding, by compression, about the bottom hinge point of the flying wires.  The upper spars need to resist flexing and compression, NOT bending due to added G forces, the wires do that.

This is the company that originally made the wires for the Camel in WWI! http://www.steenaero.com/Products/flying_wires.cfm

 

AN675 is what they are using on the wings.  There are 8 flying wires, each capable of supporting 6900 lbs (the wire will break before the attaching bolt will shear).  The wires should be able to support something on the order of 20-30Gs, which means the wood in the wings will fail before the wires will.  Now we just need some data on aircraft wood, and we can probably get close to available G loading by doing some math...

4 minutes ago, unreasonable said:

 

If that is true why are the undamaged limits of the braced wing planes broadly in agreement with the sources?

 

What I think they have done is not to calculate the mechanics of spars, forgetting about the wires, but they started with an undamaged result for the whole plane based on tests etc, then made rather ad hoc calculations with respect to how much the implied G limit on the "spar" is reduced by damage in a particular place.   

 

 

Ah, that may well be the case.  For my own education, where are the sources for limits on undamaged wings?  

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Posted (edited)
53 minutes ago, Chill31 said:

 

I don't think (emphasis on think) that is right...I beam math gives exponential strength increases as the beam depth increases.  For example, if I take a 3 inch deep spar and make it 4 inches deep, it will have about twice resistance to bending.  

 

The DrI has a depth of 4 inches (10.6 cm), you have to include the web in the strength.  Doubling the web thickness of the web has less impact than adding 10% to the spar depth, so it is not just about how much material is in the spar.  Total depth and total width play the largest role spar strength.

 

I think that is why they have calculated a much greater strength of the Fokker spars vs others.  The flying wires contribute a lot the smaller wings strength though, over the spar depth.  I bet that is why they are more fragile!  The flying wires aren't incorporated in the strength, thus the spar is the only thing calculated as bearing the load.

 

Well the reason the Dr1 beam is so stiff is that it has the 4 spar elements far out from the bending axis where they are held in place by the plywood:

 

Beam theory gives the total resistance to bending as:

 

It= Io + A*L**2

 

Where Io is the bending resistance of the spar element, A is the cross sectional area and L the distance from the bending axis (in this case the middle of the DR1 spar).

 

Intuitivite one can realize that the bending resistance Io from the spar elements themselves is small: Try taking a h=1.5 x b=5 cm spar and bend it: It will not take much load.

 

(The spar elements own bending resistance is expressed as Io=b*h**3/12 BTW.)

 

So the major contribution comes from the square of the “L” multiplied by the area b*h.

 

So this means that while a built up spar like on the Fokker Dr1 is very strong, it actually derives its strength from the spar elements in the corners.

 

So again, for damage resistance purposes, its perfectly valid comparing the risk to shoot away the 4 x A/4 spar area in a Dr1 with shooting away the concentrated area A in a Camel.

 

 

Edited by Holtzauge
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2 hours ago, unreasonable said:

I find it implausible that a plane with a limit of 13Gs

I find it implausible that we have WW1 crated that can do 13 g. Modern competition planes for aerobatics are not made for such standards. That is about the breaking up point of a Rafale. 13 g is nonsense, regardless of who supposedly wrote it.

 

21 minutes ago, Chill31 said:

which means the wood in the wings will fail before the wires will.

No, it means that most likely the attachment points will fail.

 

It is obviously wrong to take the whole height of the box spars as height if it was a single piece of lumber. Looking at the beams inside, there is about as much meat in a box spar than in an externally braced design, which makes sense as both are designed to carry the same loads. Ironically, if you take the whole height of the box spar, you actually make it more sensible to bullet damage, as when you hit the sides, you're actually hitting the bracing, something you cannot do in  this sim in case of braced wing designs.

 

What we definitely can say that designers didn't include as much structural reserve in early war recon planes as they did in late war scout planes. But planes that tolerate about even loads have about the same amount of lumber in them, meaning they do not differ much in damage resistance. Especially in a world where "hitting the right place" is not possible.

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2 hours ago, J5_Hellbender said:

 


Central:

  1. Fokker Dr.I, Fokker D.VII and Fokker D.VIIF wings made stronger;

  2. Albatros D.Va lower wing spar now correctly vibrates during dive and correctly disintegrates entire airframe when touching the stick;

Entente:

  1. No changes.

 

The chance is great that it will be so.  You just look at what they did by releasing a hot fix)) And there was also a story when someone complained that the P3 was flying too slow and the camel too fast.  As a result of complaints, P3 flew even slower, and the camel even faster)) All this seems to be revenge for the trouble 😉

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28 minutes ago, ZachariasX said:

But planes that tolerate about even loads have about the same amount of lumber in them, meaning they do not differ much in damage resistance.

 

Even if true, that begs the question as to whether the planes did tolerate about even loads.

 

At the aerodrome forum someone says he has the full report - lower wing failed at 10.7 with upper wing still unbroken.

 

https://www.theaerodrome.com/forum/archive/index.php/t-34302.html

 

Someone might be able to make some sense of this - it is about the US post war tests, but on specific pieces. Still looking for the report mentioned in the aerodrome.

 

https://books.google.co.th/books?id=0G04AQAAMAAJ&pg=RA2-PP9&lpg=RA2-PP9&dq=Fokker+D.VII+7774/18&source=bl&ots=xTX_mdmhd5&sig=ACfU3U0CpTrmY4SKXAjNRwhWIhFiKwYZlg&hl=en&sa=X&ved=2ahUKEwjI__mDxvLpAhUymeYKHbMuCvAQ6AEwC3oECAkQAQ#v=onepage&q=Fokker D.VII 7774%2F18&f=false

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46 minutes ago, ZachariasX said:

I find it implausible that we have WW1 crated that can do 13 g. Modern competition planes for aerobatics are not made for such standards. That is about the breaking up point of a Rafale. 13 g is nonsense, regardless of who supposedly wrote it.

 

135.png

 

The Extra 300S is rated for +10/-10g but has an ultimate failure load of 24g.

 

http://www.gforceaerobatics.com/about/aircraft/

 

 

32 minutes ago, emely said:

The chance is great that it will be so.  You just look at what they did by releasing a hot fix)) And there was also a story when someone complained that the P3 was flying too slow and the camel too fast.  As a result of complaints, P3 flew even slower, and the camel even faster)) All this seems to be revenge for the trouble 😉

 

Well, so far it's the only (questionable) source provided which talks about actual ultimate failure load, so yes.

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Posted (edited)
1 hour ago, unreasonable said:

At the aerodrome forum someone says he has the full report - lower wing failed at 10.7 with upper wing still unbroken.

It's this:

https://books.google.ch/books?id=QdBRAQAAMAAJ&pg=RA8-PA2&lpg=RA8-PA2&dq=Fokker+D.VII+(7774/18)&source=bl&ots=dVruJlvktm&sig=ACfU3U2cx56ptJdk86uj6umh5DNO7YGVdQ&hl=de&sa=X&ved=2ahUKEwjN6POkzPLpAhU1wcQBHc20AtAQ6AEwAXoECAsQAQ#v=onepage&q=Fokker D.VII (7774%2F18)&f=false

 

Edit: It's not. Still the below applies looking at the blueprints.

 

It is a static test of the Airframe. It was found to be strong while using only marginally more material. That's the cool thing about a modern design. Stronger at the same weight. But that doesn't imply bullet resistance in any way whatsoever. In fact, lighter hightech solutions are generally FAR more sensitive to abuse than dumb logs.

 

Yet the entire DM is based on how much timber is in there. It is also in this report, for anyone who can read, described that there is onyl marginally more wood in the Fokker than in other braced wing design.

 

By it's very principle, damage tolerance of the Fokker should only be marginally better, althogh it can start off one or two g's higher than other designs.

 

Then again, there's the STRONK Pfalz. We do have braced wing designs that are VERY strong. So can you just make crappy planes slightly stonger? Even the Alb that was hated for shedding wings? It's not that the Fokker is too stong in the game. That works. The others are really too sensitive. It's just nonsense as we have it.

 

1 hour ago, J5_Hellbender said:

The Extra 300S is rated for +10/-10g but has an ultimate failure load of 24g.

*ouch*

 

But you know, wiggle around long enough at 12 g and it will be case for the bin. (But.. awesome aircraft...)

Edited by ZachariasX

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49 minutes ago, emely said:

And there was also a story when someone complained that the P3 was flying too slow and the camel too fast.  As a result of complaints, P3 flew even slower, and the camel even faster)) All this seems to be revenge for the trouble 😉

 

So let's complain that there shouldn't  be a FC vol. 2

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Posted (edited)
36 minutes ago, unreasonable said:

 

Even if true, that begs the question as to whether the planes did tolerate about even loads.

 

At the aerodrome forum someone says he has the full report - lower wing failed at 10.7 with upper wing still unbroken.

 

https://www.theaerodrome.com/forum/archive/index.php/t-34302.html

 

Someone might be able to make some sense of this - it is about the US post war tests, but on specific pieces. Still looking for the report mentioned in the aerodrome.

 

https://books.google.co.th/books?id=0G04AQAAMAAJ&pg=RA2-PP9&lpg=RA2-PP9&dq=Fokker+D.VII+7774/18&source=bl&ots=xTX_mdmhd5&sig=ACfU3U0CpTrmY4SKXAjNRwhWIhFiKwYZlg&hl=en&sa=X&ved=2ahUKEwjI__mDxvLpAhUymeYKHbMuCvAQ6AEwC3oECAkQAQ#v=onepage&q=Fokker D.VII 7774%2F18&f=false

 

I'm going to rain on the parade a bit: First we only have one sample. Second they say 10.7g. OK, so 10.7 g assuming what weight? Did they use a correct base weight or had someone mistankedly used the dry weight and not loaded weight or assumed a too low weight? How did they compensate for some of the weight being in the wing? Did they do that in a right way? How did they distribute the sandbags between the upper and lower wing? How did they distribute the sandbags spanwize to simulate the spanloading? How were they supporting  the wing because I don't think they hung it up in the fuselage upside down and if not how did they attach the wing to the test setup? Finally, a built up spar like the D7 probably fails by buckling in the shear web and prediction of buckling is notoriously difficult and the subject for countless masters and doctorial thesis because buckling results are so varying in nature: One sample may buckle at a much higher or lower value than is representative of the average. A bit salty I know but really, unless we know more about this we just have a heresay result for one airplane tested under unknown conditions.

 

However, we DO know that the German design rules 1917/18 stated a 5-6 g ultimate load requirement and you can be sure that that was what Fokker designed for because you don't get extra points for building stronger than needed and building stronger than the requirement just adds unnecessary weight which means poorer performance.

Edited by Holtzauge

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2 minutes ago, ZachariasX said:

It's this:

https://books.google.ch/books?id=QdBRAQAAMAAJ&pg=RA8-PA2&lpg=RA8-PA2&dq=Fokker+D.VII+(7774/18)&source=bl&ots=dVruJlvktm&sig=ACfU3U2cx56ptJdk86uj6umh5DNO7YGVdQ&hl=de&sa=X&ved=2ahUKEwjN6POkzPLpAhU1wcQBHc20AtAQ6AEwAXoECAsQAQ#v=onepage&q=Fokker D.VII (7774%2F18)&f=false

 

It is a static test of the Airframe. It was found to be strong while using only marginally more material. That's the cool thing about a modern design. Stronger at the same weight. But that doesn't imply bullet resistance in any way whatsoever. In fact, lighter hightech solutions are generally FAR more sensitive to abuse than dumb logs.

 

 

:lol: That is a report about the chassis - the undercarriage.  As shown in the diagrams and photo.

5 minutes ago, Holtzauge said:

 

A bit salty I know but really, unless we know more about this we just have a heresay result for one airplane tested under unknown conditions.

 

However, we DO know that the German design rules 1917/18 stated a 5-6 g ultimate load requirement and you can be sure that that was what Fokker designed for because you don't get extra points for building stronger than needed and building stronger than the requirement just adds unnecessary weight which means poorer performance.

 

1) Indeed  - so I would like to find it.  None the less, n=1 is better than n=0 if the test report can actually be found.  

 

2) Perhaps, but a very high ultimate load might have been an unintended consequence of building a wing with a thicker airfoil.   What would certainly cost you as a designer would be to make something that, when tested, turned out to be weaker than designed, especially in a war time setting trying to build quickly and win orders against competition. 

 

   

 

 

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We'll we could of course apply the same principle to engines: One manufacturer sets a 5 min limit on WEP. I find one tests which shows one engine surviving 10 min so let's use that instead.

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9 minutes ago, Holtzauge said:

However, we DO know that the German design rules 1917/18 stated a 5-6 g ultimate load requirement and you can be sure that that was what Fokker designed for because you don't get extra points for building stronger than needed and building stronger than the requirement just adds unnecessary weight which means poorer performance.

 

I'm not entirely convinced of that. The conventional wisdom until the Fokker Dr.I was that you needed thin wings and struts. I believe Fokker almost inadvertently created a 1930's design back in 1917-18, especially with the Fokker E.V/D.VIII. It's not the first time that a designer/engineer is way ahead of his time, the knowledge subsequently lostdiscarded or difficult to replicate and then later on (re)discovered.

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1 hour ago, Holtzauge said:

 

So again, for damage resistance purposes, its perfectly valid comparing the risk to shoot away the 4 x A/4 spar area in a Dr1 with shooting away the concentrated area A in a Camel.

 

 

So you are discounting the two 1/16 x 4in side caps as adding strength? Begs the question of why did they bother adding it.

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7 minutes ago, Holtzauge said:

We'll we could of course apply the same principle to engines: One manufacturer sets a 5 min limit on WEP. I find one tests which shows one engine surviving 10 min so let's use that instead.

 

646227496_Aredherring.thumb.JPG.89782310f0595f84710e06c151eb1139.JPG

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25 minutes ago, Holtzauge said:

 

I'm going to rain on the parade a bit: First we only have one sample. Second they say 10.7g. OK, so 10.7 g assuming what weight? Did they use a correct base weight or had someone mistankedly used the dry weight and not loaded weight? How did they compensate for some of the weight being in the wing? Did they do that in a right way? How did they distribute the sandbags between the upper and lower wing? How did they distribute the sandbags spanwize to simulate the spanloading? How were they supporting  the wing because I don't think they hung it up in the fuselage upside down and if not how did they attach the wing to the test setup? Finally, a built up spar like the D7 probably fails by buckling in the shear web and prediction of buckling is notoriously difficult and the subject for countless masters and doctorial thesis because buckling results are so varying in nature: One sample may buckle at a much higher or lower value than is representative of the average. A bit salty I know but really, unless we know more about this we just have a heresay result for one airplane tested under unknown conditions.

 

However, we DO know that the German design rules 1917/18 stated a 5-6 g ultimate load requirement and you can be sure that that was what Fokker designed for because you don't get extra points for building stronger than needed and building stronger than the requirement just adds unnecessary weight which means poorer performance.

I get what you are saying here, BUT what other data points would you add to it or replace it with?  This is ALL  we have.  I would take a real data point over anything we can make up in this forum. 

 

Fokker prided himself on strong wings, and 13 Gs is not out of the question. 

 

Here is some contemporary data from the Stearman trainer capable of +12Gs: https://www.planeandpilotmag.com/article/the-littlest-boeing/

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Posted (edited)

 

3 hours ago, J5_Hellbender said:

 

I'm not entirely convinced of that. The conventional wisdom until the Fokker Dr.I was that you needed thin wings and struts. I believe Fokker almost inadvertently created a 1930's design back in 1917-18, especially with the Fokker E.V/D.VIII. It's not the first time that a designer/engineer is way ahead of his time, the knowledge subsequently lostdiscarded or difficult to replicate and then later on (re)discovered.

 

We can always speculate what was going on in Fokker mind. I'm just saying how I think you would look at it from an engineering perspective. I have actually done the structural design of the wing (according to JAR22) on a motorized glider and structural engineering in the tail section on the JAS39 Gripen and we for sure ONLY included what we thought was needed to reach design requirements. I would have been strung up by the privates if the weights department at SAAB found out I tried to put some extra strength in there! :rtfm:

 

3 hours ago, Chill31 said:

So you are discounting the two 1/16 x 4in side caps as adding strength? Begs the question of why did they bother adding it.

 

Sure the plywood adds as well but mostly in terms of taking the shear load: You need the vertical plywood elements to take shear. It's like the middle part in a steel I-beam: Almost all bending resistance comes from the flanges but you also need the thin middle part to take the shear loads. And sure, the top of the box also adds bending resistance but is primarily there to close the section into a box to take the torsional loads in case of the Dr1 since the wing has no bracing.

 

3 hours ago, unreasonable said:

 

646227496_Aredherring.thumb.JPG.89782310f0595f84710e06c151eb1139.JPG

 

Aber das war kein herring unvernünftige! : Was ich gesagt habe was spot on and you know it!

 

3 hours ago, Chill31 said:

I get what you are saying here, BUT what other data points would you add to it or replace it with?  This is ALL  we have.  I would take a real data point over anything we can make up in this forum. 

 

Fokker prided himself on strong wings, and 13 Gs is not out of the question. 

 

Here is some contemporary data from the Stearman trainer capable of +12Gs: https://www.planeandpilotmag.com/article/the-littlest-boeing/

 

Sure we don't have any more data points than that single test (which we don't know how it was done or under which circumstances) but we do have the German design rules and sure, 13 g is perfectly possible but is essentially bad engineering when the requirement is 5 because there is no such thing as a free lunch: Added strength means added weight. And then why design for 13 g specifically? Why would he aim for that particular figure? Why not 15 or more?

 

And we are not making anything up in the forum (The 5-6 g ultimate load requirement): Those rules were the design rules set up by the German procurement agency for acquiring scouts for the Luftstreitkräfte in the 1917 to 1918 period.

Edited by Holtzauge

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4 hours ago, J5_Klugermann said:

 

So let's complain that there shouldn't  be a FC vol. 2

Dude, despite the fact that you like to neigh and have fun, you are a subtle poetic personality and trusting, children's natura))

If you order pizza with delivery and get cold food with rotten sausage, then you most likely will not even complain, you just order pizza vol2.0 in the same company, hoping that the second delivery will be of high quality, and the first -  just a random mistake ;-))))

I believe that two rotten pizzas cost no more than one.  Why do I need two pieces, if the first one just needs to be thrown away?

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Are we all barking up the wrong tree ?

 

Just because the wings appear to be collapsing under increased G loads, in the game, it doesn't mean that that it what is happening.

 

For an aircraft to fly a high G circle then must it not generate an equal and opposite force (lift) to the additional weight that it is put under (G) ?  In other words the forces opposing one another need to be much the same, or at least possibly with a little less on top, if you consider Bernoulli's principle to have any effect, regardless of whether the aircraft is pulling 1.5G or 10G  How much difference in force, or how much damage must be done to a spar to overcome these two mutually supporting forces ?

 

If the forces exerted on a top spar, in a bay, are compressive rather than up or down, as suggested by ZachariasX, then, unless completely smashed at one point, the spar needs to buckle or bend sideways, the trouble is not only is wood very strong in compression but there are several supporting elements in a wing that prevent the buckling, backwards and forwards, of the spar over the length of the bay.  Indeed we can see that the spars are often "lightened" in the manner of an I beam suggesting that the main consideration, by the engineers, was not an up or down movement, but rather a for an aft movement.

 

I think, what is being determined by the DM, isn't the ability to resist G forces, but the structural rigidity of the wing itself, it's ability not to flex and thus expose, or point load,  areas of the wing to forces that it isn't designed to cope with , think of Albatros DV lower wing flutter to understand what is going on with the DM.

 

I'm not suggesting the DM is any more correct because of this, it's just that the forces breaking wings are different from G forces and the structural stiffness of a wing, which is the determinent of resistance to battle damage, is being calculated, I assume, by the thickness, or width, of the spar and not the wing structure as a whole.

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7 hours ago, Chill31 said:

I think that is why they have calculated a much greater strength of the Fokker spars vs others.  The flying wires contribute a lot the smaller wings strength though, over the spar depth.  I bet that is why they are more fragile!  The flying wires aren't incorporated in the strength, thus the spar is the only thing calculated as bearing the load.

 

Honestly this is the most intelligent thing I've read in this entire thread so far.

7 hours ago, unreasonable said:

What I think they have done is not to calculate the mechanics of spars, forgetting about the wires, but they started with an undamaged result for the whole plane based on tests etc, then made rather ad hoc calculations with respect to how much the implied G limit on the "spar" is reduced by damage in a particular place.  

 

I also think this makes a lot of sense.

 

It's almost like:
1) We know the spar sizes
2) We know the G-limits
3) ????

4) Damage Model!

I don't mean that as disrespect to the devs, but rather that it's understood that the _actual_ construction of the wings is not represented here. There have been abstractions and simplifications made for a variety of reasons, etc. I think you and Chill together have come up with probably the most plausible explanation to explain what we're seeing.

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Posted (edited)

Are you guys saying that wired framed planes got just a fraction of the deal? That's clarifying. What about the random numbers that forum members provided in the poll? Where do they fit in the new damage model? Were they used in those charts made by Pet?

Edited by SeaW0lf

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I didn't realise rabbit holes just went on forever …. :blink: And yet I find myself being dragged in again ....

 

40 minutes ago, SeaW0lf said:

What about the random numbers that forum members provided in the poll?

 

That was just Russian humour. Of course everyone who responded wanted wings to withstand greater hits before failing. 4005 was real bad see and there were steaks to think of. Andrey guffawed and then ignored it.

 

9 hours ago, unreasonable said:

I find it implausible that a plane with a limit of 13Gs would be broken by the same number of bullets as a Camel or SE5a with limits of perhaps 7G ish. 

 

Surely it's not the number of bullets but where they hit?

 

9 hours ago, HagarTheHorrible said:

 

Traditional wing biplanes should be judged by their wires, NOT THIER SPARS.

 

Precisely. Bracing wires were the glue that held the wings together and gave them structural strength. That's why you were best mates with your rigger, even if he was a lowly NCO. I'm unsure why Andrey is obsessed with spars only. I guess it's computing limitations?

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Posted (edited)
56 minutes ago, catchov said:

Andrey guffawed and then ignored it.

 

That is a relief, but people are gathering to address the bracing wires omission? Because it makes total sense.

 

The shaking thing I think is also being underrated by people, almost like ambient flak. We fought for years to have ambient flak removed, and we got it. To have the shaking back is a huge step back to arcade world in my opinion. I’ve been organizing my tracks and it was amazing how we could get hit like a punching bag and still maintains some smoothness and don’t become a flying seizure.

 

To fight for a better / flyable damage model (the original one was pretty awesome by the way) and omit the shaking is sort of a half-assed job.

Edited by SeaW0lf

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13 hours ago, unreasonable said:

I find it implausible that a plane with a limit of 13Gs would be broken by the same number of bullets as a Camel or SE5a with limits of perhaps 7G ish.

I don't think it's the fact that the D7 can take more rounds, What folks are against is the fact just a few rounds will take down a camel or se5 and even the Spad. Don't know where any one said the camel should take the same amount of hits as the D7. 

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Posted (edited)
2 hours ago, NO.20_W_M_Thomson said:

I don't think it's the fact that the D7 can take more rounds, What folks are against is the fact just a few rounds will take down a camel or se5 and even the Spad. Don't know where any one said the camel should take the same amount of hits as the D7. 

 

Read @ZachariasX's and @Holtzauge's posts - they are saying that, since there is roughly the same amount of lumber in the spars, they should be broken by about the same number of hits. 

 

Since the amount of new information is drying up, I will just summarize my thoughts on this issue, ignoring all "fun" and "fairness" considerations, and then step away.

 

The issue is the claimed unrealistically high frequency with which just a few rounds collapse the wing of certain planes.  Is this perception real? if so why is it happening?  What if anything can be done about it?  Some possible theories - not mutually exclusive. 

 

1) The claim is not true, or exaggerated. What we notice, and then post videos about, are the occasions when this happens. Small numbers of hits often do not cause collapse, but nobody posts videos about those.  (My own view is that it is exaggerated, but partly true).

 

2) It is true but it is due mostly, or entirely, to people's bad flying habits built up by previous DMs. (Also IMHO, partly true).

 

3) It is true, due to differences between weak and stronk "spar" lengths being averaged out in AnP's graphs, while players see a lot of the weak areas failing first.

 

See my previous graphs.  That might explain the mismatch of perceptions - AnP and players are looking at different samples. This is a hypothesis easy to test by looking at the individual "spar" distributions from AnP's tests and running a different test to test which "spars" fail first under random shot placement conditions.

 

Even if this hypothesis is true, it leaves open the question of why the weak areas are so weak and if that is correct.  It would also mean that increasing the strength of braced wing planes on average might make little or no difference to the observed phenomenon.

 

4) Another possibility that we have not discussed at all here is the lengths of the "spar" sections, how they are determined, or their effects.  There may again be an unanticipated issue of shot distribution due to different "spar" lengths in different sized hit boxes.  Which might be a cause of (3) if that turns out to be correct. 

 

5) The developers have just forgotten about the wires.  Proponents of this idea have yet to give a coherent explanation of why the game's maximum G limits of the braced aeroplanes are consistent with the sources. 

 

There seems general agreement that hits that take out wires, or wire and wing attachment points,  can lead to the wing failing, even if the spar is undamaged, so there will always be the possibility of a very few shots leading to collapse in a realistic DM. Externally braced wing designs have far more of these critical attachment points, plus the wires themselves. They should always be more vulnerable to critical hits.  

 

Quite how all these factors balance out I have yet to decide myself.  Unless we hear any more from AnP, who no doubt gets up in the morning eagerly looking forward to reading this and the other thread, it is time for me to get out of here......... and play some more of the scripted campaign missions. They are very well made.

 

Spoiler

aliceinwonderland-downtherabbithole-011.jpg.ee38c063958b4e4b58ccbdcd8461c433.jpg

 

  

 

 

Edited by unreasonable
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Posted (edited)
30 minutes ago, unreasonable said:

Things  


1) Interesting, so like a....non-survivor bias! I had the same thought, which is why I wanted to gather some data where I'd throw a 'weak' plane (Camel, SPAD, what have you) in among a bunch of two-seaters and list the times the test plane 'escaped' or had its wings clipped. In addition to the 'one-bullet-wing-off' trick, I can say that I've definitely seen one of our SPADs come home in a very sorry state...busted struts, missing wires, etc etc. I've also seen SPADs surprise me by not coming apart in certain manoeuvres after taking seemingly-fatal (or totally G-debilitating, rather) manoeuvres. 

2) I'd agree to aggressive flying being a factor - but I'm still undecided if the "punishment" is too severe or not. After all, I'm certain the real WW1 boys would have pushed their machines pretty hard as well. 

5) I've been looking into that one a little as well. The SPAD definitely seemed to be weaker with even a couple of its wires gone. The Alb surprised me, still pulling 5 - 5.5 Gs with no wires left at all. 

It was 3rd P.G. training night tonight - I got shot-up a fair few times and escaped...but it was more due to poor accuracy from my pursuer, and another SPAD finishing him off before he finished me off...! Essentially once my wings were busted up I'd lose any idea of vertical manoeuvres or hard turns, and just jink while trying to get away. If you have a guy close on your tail it seems more like a choice between a long drop or a quick bullet....

Re: more correspondence with AnP...looks like that ship has sailed. I think 4.006 will be a "Take what you're given" type deal - making all 19(!!!) pages of this a rather entertaining and enjoyable waste of time ;) 


 

Edited by US93_Larner
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