Project Help - Replicating Mc Laren's "F-duct"

[riker84]

Hello all,

This is my first time posting on this website so if I've posted this in the wrong section, I apologize. I am posting with regard my final year project of a Mechanical Engineering Degree in Ireland. I have chosen to do my thesis on the effect of blown air on a rear wing, as used by Mclaren on their track car.

I plan on doing some F.E.A. testing using a programme called "Ansys", and then make a model for wind tunnel testing. Although I dont know the exact way I'm going to make the wing yet, I think i might use an aluminium skeleton but as regards covering the frame, i am lost. I am thinking fiberglass, but I am not sure yet.

I plan on wind tunnel testing the wing with and without the blowing apparatus. The main problem I have encountered is the blowing apparatus itself. My idea is to have a small airpump outside the windtunnel, then using a small tube to blow air onto the wing. This hopefully should divert the adhesive air stream off the steep edge of the second plane, thus decreasing the downforce.

The thesis itself is in early stages yet, but I thought I would post it on this forum so I could get some useful advice.

Also, I have researched on different explanations of how the 'f-duct' works, most seem to be using the term 'wing stall'. To my understanding of aerodynamics, would a wing stall not create great amounts of wake turbulence or drag?

Thanks in advance for any replies I recieve.
Best Regards,
Patrick

[SiLo]

Maybe cover it in solafilm, I used it to produce the skin of a boat at uni and the stuff is very good, just make sure you get the right cuts and use a heat gun.

[SiLo]

http://www.ashfordmodel.co.uk/solafilm-78-c.asp

[The FOZ]

I'd suggest that you cut the wing elements from foam using a CNC router or CNC hot wire cutter, then wrap them in adhesive vinyl or the like.. This is a fast, cheap approach that will let you go through multiple iterations as needed. Aluminum frames are costly and time consuming, far more elaborate for your approach.

Check out some R/C plane sites, you should be able to find lots of information on using foam with plastic coverings...

Good luck!

[wrcsti]

I'd suggest that you cut the wing elements from foam using a CNC router or CNC hot wire cutter, then wrap them in adhesive vinyl or the like.. This is a fast, cheap approach that will let you go through multiple iterations as needed. Aluminum frames are costly and time consuming, far more elaborate for your approach.

Check out some R/C plane sites, you should be able to find lots of information on using foam with plastic coverings...

Good luck!

coming from said rc plane sites i would recomend doing your wing out of foam, then "glassing it" meaning add a layer of fiberglass on to it, then remove the foam with acetone and now you have a hollow wing ready to be blown from the inside just like the F1 wings.

[riker84]

Thanks for all the replies folks, I have some images of a basic set up im proposing. This project is more about replicating what the F-duct does, rather than a to-scale model of the actual device. I am working under the assumption that air is blown from a channel in the shark fin to rear wing. How it gets there, is none of my concern.
Here are some images, that ive mocked up on a few ideas, this is merely a rough outline as to where im going with the project. Green air indicates are flowing over the wing naturally, blue represents blown air from outside the wind tunnel.
http://www.flickr.com/photos/33850204@N06/5204574140/
http://flic.kr/p/8VRJCR

[747heavy]

may I see this wrong riker, and if so I appologize.

But I don´t think the McLaren wing has a connection between the upper and lower
surface (high and low pressure side of the wing).

The slot exits only on one side (low pessure side) - IMHO

on another note, but maybe this is just due to the illustration, your wing profile
looks like a tear drop, which means it is not much of an wing profile, as the lengths of cord is more or less the same around the centre line.
This is maybe not a good representation for a actual F1 wing profil.

Other then that, good luck & please keep us posted.

Regards

[riker84]

Hey,
This is only the upper plane, and for illustration i just used a NACA 23021 profile. The finished product will have be a better replication. I am not sure what you mean by the slot only exiting on one side? Thanks for the help, this is for my final year project of a mechanical engineering degree. The pressure is on with my workload, so comments and criticisms are always welcome. Thank you

[wrcsti]

The blowing slot is maintained only on the lower side of the wing. You have a channel conecting top and bottom of the wing to blow it, there should be only 1 side.

Off topic, I do wonder if a similar effect to Fduct could be used to increase downforce? Maybe by blowing air on the top of the wing at an angle creating a gurney made of air.

[747heavy]

sorry for expressing myself not clearly.
I think this is a more accurate representation of the system.

(sorry I "stole" and modified your drawing)

[riker84]

This is a weight off my mind. Especially with regard machining. Currently I have some RP and Cnc machines at my disposal, but a split flap profile as i had originally posted, would have been a nightmare to machine.

So my new understanding would be this, from a front view, we see no slit in the wing. Only from the rear the slit is visible?

wrcsti, I was thinking the same, but how to do this without effecting the profile would be hard I'd imagine?

[747heavy]

Hi Rieker,

Just one thought, as far as I know (and I know next to nothing about the system),
the angle at which the air exit´s (get blown out from the wing), is important for
the function of the system.
So maybe you need to keep this in mind, and come up with a prototype where you can
change the exit angle, until you have the best effect.
I just wanted to mention it, so that you don´t machine a slot into your wing, and
because you choose the wrong angle, it does not work as you expect it to do.
I will put up a small sketch a little bit later.
Good luck

[riker84]

Thanks 747heavy, I am thinking of machining a slot into the flap, then some sort of dummy which can be insterted into the slot to change the angle of the blown air. I can then vary the airflow using the pump outside the test apparatus. I should have a full prototype done up in solidworks by Sunday. A sketch would be helpful 747, cheers!

[747heavy]

you may want to be able to do this:



Therefore, as I don´t know, how you want to build your wing profil, keep in mind,
that you don´t want to machine a long slot from the surface towards the centre, as
this will define your "blow angle", and you won´t be able to change it.

I think (but I could be wrong) you will need to be able to change 2 (better 3) variables.

- Blow angle/direction at the slot exit
- air flow through the slot (how hard you have to "blow" to achieve seperation)- this you do with your pump pressure/volume, and it´s the most easy one

and the third one would be , position of the slot along the cord, which means do you want your slot closer to the trailing edge or more towards the leading edge etc.

But this last parameter is difficult to achieve, if you only want to built one wing. I guess you could prepare 2 or 3 diffrent slot positions and cover/blank off
the ones you don´t use. But maybe this goes hand in hand with some compromises of you surface finish.
3 different wings would be the better option IMHO if this is feasible for you.

have a look here: this is a RC-plane wing made from a foam core, which has a hollow section. Something like this may be possible to use for your experiment.
http://www.rcgroups.com/articles/ezonem ... ofile1.jpg

[riker84]

I think your right, 3 flaps would be the only way to go for accurate results. The finish on the underside would be compromised if i was to trick around with slot inserts. What sort of profile would you recommend for the flap, i've been tricking around with a NACA 23012 mainplane and a 23021 flap ?

That pic looks great, I'm going to start searching these RC sites. They seem to have a great deal of info that I can use!