shelly wrote:it is really impressive and sometimes counter intuitive: e.g. you could get torsion applying an axial load.
I'm used to that. We get it on tall buildings due to differing axial shortening of the columns. You also get some unusual torsional & axial effects from applying lateral wind loads. The reinforcement in the columns and shafts are no different to fibres and cores in the wing.
The difference is that the building analysis aims to limit the movement so it is imperceptible and the lifts don't jamb in the shafts, while these wings are trying to maximise the movement.
horse wrote:Just to point out the crazy re-circulation of this argument, the point that Richard made to JET was also mentioned on page 24.
Ciro Pabón wrote:The wings cannot move more than 2 cm under a 1000 newton load. It seems to me they are moving more or less what regulations say.
Surely they have more than 1000 newtons load! More in the vicinity of 5000, I'd guess. So, they can easily move more than 10 cm at the tips. It is a cantilever, you know...
So, what's the problem?
Bad losers are losers.
I'll also take the opportunity to repose the question I put in the other thread -
Why does 3.17.1 specify 20mm? Why not, say, 5mm?
Assuming Ciro's numbers are correct (i think they are) and linearity, they just didn't want the tip to dive to deep under tarmac. You know - someone have to pay for new asphalt after the race.
The static test is done with the weight centered on the beam but in use on the track the center of pressure is ahead of the beam causing the front of the wing to pivot downward.
richard_leeds wrote:[The effect can be created with isotopic materials too if you give them the right asymmetric profile. Damn physics!
This is actually not true Richard, isotropc material are just that, isotropic, you can fool around a bit with profiles an such but nothing like this. When you see what can be done with your own eyes, promise you will wet your pants. I know I did at that university lab 30 years ago.
I agree with xpensive - behaviour of composite beams/panels it is really impressive and sometimes counter intuitive: e.g. you could get torsion applying an axial load.
It is far more than what is achievable with isotropic materials, even with fancy beam sections; and it is something beyond what we are used to.
I think too, like richard and others, that we should stop discussing merit of the rules in thsi thread, and instead focus year on the technical side of controlled flexi wing design.
Only I fear that it is too difficult a task trying to elaborate on a techincal solution most teams seem not able to master at the moment; but I hope we could collect some ideas
xpensive - Anisotropic material display different young's modulus in different directions. As per this a material displays a different deflection for a same loading in different direction.
Now in case of the wing we have down force which is vertical loading on the wing and drag which is perpendicular to down force. But from images it is clear that deflection is in direction of down force and not drag. As per some of the (brief) explanations you have given in this on anisotropic material, i fail to see how drag force affects the modulus of elasticity in the down force direction.
horse wrote:Why does 3.17.1 specify 20mm? Why not, say, 5mm?
Assuming Ciro's numbers are correct (i think they are) and linearity, they just didn't want the tip to dive to deep under tarmac. You know - someone have to pay for new asphalt after the race.
I don't understand though, if you allow it to deflect by less distance then it will stay further from the tarmac, right? There must be a reason for 20mm. If not, why not make it less to aid compliance with 3.15?
"Words are for meaning: when you've got the meaning, you can forget the words." - Chuang Tzu
Actually Williams F1, I don't think we are talking different modulus here, more like different properties in whatever directions.
A pure horizontal force, without anything else, should on an isotropic material more or less only result in bending in the same direction. In the same fashion a vertical force would typicaly result in a vertical direction and nothing else.
However, with an anisotropical material such as carbon fibre can be, you can arrange it to have diferent properties in different directions resulting in strange results, such as a horizontal load results in vertical deflection and vice versa.
As an xample, if you build a resin-matrix carbonfiber cantilever beam with all the stiff fibers arranged at some 37 degrees, applying the same bending moment as torque, the darn thing will actually bend upwards, until it breaks of course.
This is what I belive RBR is doing, cleverly arranging fiber-directions so that the front-wing is vertically stiff when subjected to pure vertical-load, such as a deflection test, but when subjected to horizontal load, it quickly bends down.
"I spent most of my money on wine and women...I wasted the rest"
xpensive wrote:Actually Williams F1, I don't think we are talking different modulus here, more like different properties in whatever directions.
A pure horizontal force, without anything else, should on an isotropic material more or less only result in bending in the same direction. In the same fashion a vertical force would typicaly result in a vertical direction and nothing else.
However, with an anisotropical material such as carbon fibre can be, you can arrange it to have diferent properties in different directions resulting in strange results, such as a horizontal load results in vertical deflection and vice versa.
As an xample, if you build a resin-matrix carbonfiber cantilever beam with all the stiff fibers arranged at some 37 degrees, applying the same bending moment as torque, the darn thing will actually bend upwards, until it breaks of course.
This is what I belive RBR is doing, cleverly arranging fiber-directions so that the front-wing is vertically stiff when subjected to pure vertical-load, such as a deflection test, but when subjected to horizontal load, it quickly bends down.
But why is it becoming such a problem to replicate? CF has been used in F1 since the mid 80's, teams should be experts in this subject.
CF has in F1 been used as a rather simple closs-ply weave, as an Aluminium-ersatz if you wish. This is something else, painstakingly applying layer after layer of thin directional film in order to get the right properties, finaly bonded together.
Besides, the calculation technology is not that easily available, surely RBR spent a lot of time to master it.
"I spent most of my money on wine and women...I wasted the rest"
horse wrote:Why does 3.17.1 specify 20mm? Why not, say, 5mm?
Assuming Ciro's numbers are correct (i think they are) and linearity, they just didn't want the tip to dive to deep under tarmac. You know - someone have to pay for new asphalt after the race.
I don't understand though, if you allow it to deflect by less distance then it will stay further from the tarmac, right? There must be a reason for 20mm. If not, why not make it less to aid compliance with 3.15?
Sorry horse, it was supposed to be a joke, but my poor english probably made it fail. I'm working on this.
Of course FIA must know it - if you allow 20mm under 1000N, you effectively allow 50mm under 2500N.
And as we see, most of the teams have no reliability problems with much stiffer wings, so FIA can mandate 5mm/1000N from the next race on. If they want.
A. A world class aerodynamicists knows exactly where the maximum pressure resultant on a multi element wing is loacted(slightly behind the leading edge).
B. World class composite engineers know exactly how to achieve these properties. For bending stiffness, you need 0/90 degree layup and for torsional stiffness you need +-45 degree layup. Then it's a question of order in the laminae and amount of layers. This is exactly what fibre composites are used for, instead of an isotropic material, you have an anistropic(mostly orthotropic due do the advanced and expensive manufacturing techniques) material plus the benefit of achiving great material properties with a lot less weight...
C. The test can easilly(apply the load more to the front) be changed to include torsion.
D. I'm mot a world class aerodynamicist or composite engineer, but I studied all these subjects in college. I coded a program for optimising laminae layup, solved problems like this one we are discussing, e.g.+-45 degree fibres in centre and 0/90 degree fibres on surfaces. I took one course in basic aerodynamics and recently I read "Competition car aerodynamics"(highly recommended) were you have illustrations of the pressure on a single element wing, a multi element wing and the effects of changing the angle of attack.
Conclusion:
I don't have a clue of what they are doing but I undertstand that the gain in downforce is massive by closing the gap to the ground.
Last edited by Donuts on 06 Apr 2011, 08:59, edited 1 time in total.
The speed of Ayrton Senna.
The mind of Alain Prost.
The dedication of Michael Schumacher.
The determination of Alex Zanardi.
On which ground would you allow 50mm of deflection when you have specified 20mm at the current load?
hooks law?that´s not working here as the materials in use do not show isotropic behaviour. But then the same set of rules expressively denies you of ANY deflection.So as I see it we cannot rely on common sense or make assumptions here.
The static load test is giving an allowed deflection under those test conditions and is allowing NOTHING else,not implied and nothing you could ever base a complaint on.It´s again a surprising set of rules being very exact in specifying things completely irrelevant to how the car performs or bends the rules.
It really is showing just how big the gap is between those in the know and those trying to create a set of rules to govern the sport.the pros are governed by aging amateurs....you would need Rory Byrne John Barnard and gordon Murray to create the rules,add Nigel Stepney and mr.Caughlan to the bunch and you got a start of course their expertise is paid by the teams then to slice of the first ten percent of their force.
The key is the overall behaviour of the composite section, as opposed to the fibre itself. You could create a similar effect using metal fibres that are isotropic, but can create an anisotropic effect when used to build up a composite structure.
It is probably more than just laying fibres at an angle. I imagine the fibre would change direction to create a change of stiffness in the section, ie a hinge point.
I also wonder if some of the fibres are debonded to create tendons in a sleeve, that's where you can play with some very imaginative effects because it is more directly parallel to the tendons controlling your fingers, or the cables used to trim a yacht mast.
They are not allowed to apply external force to pull on the tendons like a puppet. However, the drag can cause horiz bending in the wing at the pylon. That generates a force on the debonded tendons. The debonded tendons are routed to anchors in the endplate to generate eccentric loading, hence torsion. This appears to be aided by a hinge at the junction of the neutral zone and aerofoil.
Concerning the strange behaviour that carbon fibre can be made to exhibit.
I am making a pendulum clock with carbon fibre pendulum rod. Wanting to know what the expansion co-efficient is so I can do the thermal compensation I find that it can even be constructed so that it contractswith increasing temperature. One particular formulation & layup is called Zerodurused for making telescopes which has practically a zero coefficient. http://www.netzsch-thermal-analysis.com ... re_187.pdf http://www.springerlink.com/content/g2k ... lltext.pdf
Let us put aside sophisticated building techniques for a moment.
Supposing we have a normally behaving cantilever beam which bends 20mm at the tip when subject to 1000N at the tip, how much do you expect it to deflect under a 3000N (60m/s) or 6000N (90m/s) uniformly distributed load?
That's to figure out what amount of extra deflection is obtained by rbr with special building technique
