Looking for a small Aerofoil for project

judas101

Hi guys.

Was wondering if anyone could help me with something important.


I'm a final year mechanical engineering student and I intend to do my final year project on investigating the aerodynamic effects of Gurney Flaps on Aerofoil with the use of a wind tunnel.

A long shot perhaps but I need to get my hands on a small Aerofoil (I'd estimate an 350mm span at most) on which to carry out the project. Machining a wing would be too long and complicated so I'm on the lookout for one.

Would anybody on here have one and be willing to donate it for a few months for the benefits of science?

i can promise it'll be perfectly looked after and returned in the condition it's received. i'll give you a few bob for your troubles too!


failing that, if anybody has any ideas where i might be able to pick one up it'd be greatly appreciated.

many thanks.

Jakey

You may have better luck asking moddlers for such a small wing.

Good Luck

judas101

a model would not suffice as it needs to be made out of a proper wing material (aluminium ect.) to be dimensionally accurate.

a segment of a wing is really what i'm after i suppose.

ill track one down somehow!

bushy...

If its only 350mm long , maybe cut 2 pieces of plywood to the proper profile and sheet them ? A printing works with older type gear would have small sheets of suitable stuff . Small aircraft wing material is very thin anyway.

oscarBravo

judas101 wrote:

a model would not suffice as it needs to be made out of a proper wing material (aluminium ect.) to be dimensionally accurate.

I'm not sure what you mean by this. A model could be fabric-skinned (like a full-size airplane could) or wood-skinned (like a full-size airplane could). What's so special about aluminium, for the purposes of your project?

judas101

oscarBravo wrote:

I'm not sure what you mean by this. A model could be fabric-skinned (like a full-size airplane could) or wood-skinned (like a full-size airplane could). What's so special about aluminium, for the purposes of your project?

its all to do with dimensional analysis and homogeneity. also, i need a quite considerable downforce to be generated as i'm investigating effects of Gurney flaps on the wing.

for the puropse of the experiment i imagine it would not be dimensionally accurate to scale up a wing made from model material. or perhaps i'm wrong. if it is possible it would add some complex dimensional analysis into the project, so a small actual wing segment would be more desirable to start with.

model wings by their nature dont need to generate as much lift/downforce as real wings obviously (duh!) so i'd need to try and factor in for all the variables due to the size and material.

however,if the model wings can generate a sufficent ammount of downforce perhaps it's an avenue i could in fact look down.

the reason why i would prefer an aluminuim wing is that is makes calculations a lot less cumbersome when it comes to calculating and factoring in surface roughness. also, ridgidity comes into play. aluminium would rule out more variables so its desirable for the experiment without getting into too much detail.

to give people an idea about what i'm after, the ideal specimen would be a segment of a helicopter wing. the fact that it's a bone a fide wing simplifies the scaling up and scaling down process unlike with a small model.

this all probably doesnt make a lot of sense to anyone who isnt familiar with model testing or dimensional analysis but i'd just like to see if i can go down the path of least resistance first and if i have no luck i can look down other avenues.

cheers for reading and sorry for an rookie spelling mistakes and grammatical errors, i havent started the thesis yet!

ScabbyLeg

A aerofoil doesn't generate a net downforce, or am I misinterpreting? Isn't that the point of an aerofoil?
One problem you will encounter is getting accurate data from wind tunnel experiments, your measuring device will have to be calibrated etc.
You can use any material. Pick a specific aerofoil (you can get coordinates from various online databases to make a template) and use the available Cl and Cd graphs to help you... and then repeat the whole thing for your flapped aerofoil.
I think there are other people on this forum that can help you much more...

For the basics, take a look at Fundamentals of Aerodynamics by Anderson, you'll at least get the idea of what should be going on with the lift and drag coefficients.

judas101

ScabbyLeg wrote:

A aerofoil doesn't generate a net downforce

wha??


the purpose of a wing is to create downforce, or lift which ever way it's inclined

i appreciate where youre coming from in saying that any material could be used but attatching aluminium Gurney flaps to a lightweight small wing would wreak havoc from a dimensional standpoint as well as the downforce issues already hghlighted so i'm going to stick with the aluminium or solid composite wing.


cheers for all the feedback by the way and all and any opinions/comments are welcomed. if anyone feels i'm off the mark in my assumptions please say so!


EDIT: how difficult would it be to C+C an aerofoil shape d'ya reckon?

Turbulent Bill

You're probably better off using one of the NACA aerofoil sections as a starting point, as at least they'll be properly characterised and so easier to verify experimentally. Does your department/school have a workshop or lab to make up a wing section?

Slightly OT, but I'm not sure that using aluminium will improve your surface roughness calculations any more than wood, carbon fibre etc. As you mentioned, scaling up a wooden model wing would also scale up the wood grain, knots etc. In the same way, an aluminium model would have to be extremely smooth for dimensional accuracy with a full-scale example. Not at all sure on this, just my 2c.

oscarBravo

I'm also curious about the length of the wing section - doesn't that become a factor, what with wingtip vortices and so on?

judas101

Turbulent Bill wrote:

You're probably better off using one of the NACA aerofoil sections as a starting point, as at least they'll be properly characterised and so easier to verify experimentally. Does your department/school have a workshop or lab to make up a wing section?

yeah, that'd be the plan alright. at least i'd be sure of proper downforces then. we did some C+C last year and i do have the facility if i need it.

Turbulent Bill wrote:

Slightly OT, but I'm not sure that using aluminium will improve your surface roughness calculations any more than wood, carbon fibre etc. As you mentioned, scaling up a wooden model wing would also scale up the wood grain, knots etc. In the same way, an aluminium model would have to be extremely smooth for dimensional accuracy with a full-scale example. Not at all sure on this, just my 2c.

carbon fibre would be a perfect material. a wooden wing might suffice if the surface was finished to a high standard. it's just that whenever anyone mentions a wooden wing to me an image of a hacked up piece of 2x4 pops into my head! :rolleyes:

i reckon a metal or carbon fiber wing secment shouldnt be too hard to come by.

dont suppose you have one going?!?!? lol

ScabbyLeg

judas101 wrote:

wha??

An aerofoil in the context of an aircraft creates lift. Turn it upside down and attach it to your car and it's downforce you're dealing with. Edit: sorry, that's what you said. Still, during my studies I never heard the purpose of a wing being to create downforce as such.

All of your analysis will have to be done in non-dimensional terms, ie. coefficients of lift, drag etc. As a result, the size of your aerofoil section does not matter.

Look into the Reynolds Number if you haven't already come across it. This will be important.

oscarBravo

ScabbyLeg wrote:

All of your analysis will have to be done in non-dimensional terms, ie. coefficients of lift, drag etc. As a result, the size of your aerofoil section does not matter.

Really? I understood that lift was a function of lift co-efficient, wing surface area and the square of the airspeed. Surely the latter two are related to scale?

Turbulent Bill

oscarBravo wrote:

Really? I understood that lift was a function of lift co-efficient, wing surface area and the square of the airspeed. Surely the latter two are related to scale?

That's the idea of dimensional analysis - you normalise the analysis to express it per unit area, per unit velocity or whatever you happen to need. It allows you to characterise a particular aerofoil section without considering the actual wing size. Naturally, the actual lift force of a wing is dependent on these parameters multiplied by the area, velocity squared etc.

oscarBravo

Fair enough. I'm still curious about the length issue, though.

universe777

OP - what college are you in? DIT Bolton st have a dept. of aeronautical engineering, its in a building in the car park at the front. They have a helicopter and other assorted aviation parts, its been about 5yrs since i was in there.