Building Materials, Structures & Processes.

Phydelis is such a nice sensible young man dont you find!!

Sorry all for not coming regularly as am suppose to but the assignements n works of other courses at taking the best of my project time. Please i will like to know what ways to measure bending and torsion of an aircraft wing. One of the major issue should be the rig and ways of clamping it in other to take the above measurment.
Thanks as always.

phydelis
Because a wing is not a simple beam as Eric says the stress calculation quickly becomes very, very complex and even in big full size they still have to actually test it to prove their sums were right.

For models the only real alternative is experience and actual testing. One benefit however is that as size reduces the relative strength of material increases so the weight penalty for building over strong is not that great.

However bending is not the only load a wing has to resist as there are torsion loads as well. If even a small twist develops as the load is applied it can have a significant effect on the bending forces.

I use a very simple test that works reasonably well up to say 6ft span. Lift the fully loaded plane up by its wing tips. This applies a bending load at the wing root equivalent to a 4G manoeuvre which, with care, is enough for even basic aerobatics.

Thanks guys. but i need to know how to set up the rig and ways of clamping it in other to take the measurements. Because the university seem not to have the clamping devices so am ask to provide one.
Thanks as always.

phydelis wrote: Sorry all for not coming regularly as am suppose to but the assignements n works of other courses at taking the best of my project time. Please i will like to know what ways to measure bending and torsion of an aircraft wing. One of the major issue should be the rig and ways of clamping it in other to take the above measurment.
Thanks as always.

Phydelis should be posting here soon, I've just spoken to him on the phone,.
There's no set formula for wing flexibility, that's down to the construction.
The simplest way to measure the flex in a wing is to anchor the root with any suitably heavy weight and lift the model by the wings ... see how much they bend.
You'll need to be more specific here Phydelis, please remember, you're doing degree level studies .... we just build & fly the buggers.

Pol.

One way of testing a wing is to use sand bags!



It is still a method used by homebuilds today!

The above were the samples i was asked to get my experiment from. But i have requested the university to get me a foam and a balsa in other to get a proper wing instead of the crashed wing. Hopefully they get it i will have to get a proper configuration for the wing.

Question:
Is there a proper or an idea configuration for a wing?

Thanks so so much.

phydelis
Ideal wing?
Unfortunately the 'ideal' structure is different from the 'ideal' aerodynamics so it always has to be a comporomise.
The problem is the 'best' compromise depends on several things like the material it is made with, the speed it will be flown at, the loads it will put under and cost!

If you look at a high performance glider wing it is biased toward aerodynamic efficiency. Very spindly with a huge span but strict limits on the load it can carry, its speed and almost regardless of cost.
A simple homebuild is likely to have a 'chunky' wing with limited span and a thick section to make it strong, easy to build with simple materials so a lot cheaper.

In some respects it will come down to how much you want to spend in time and money!

Phydelis popped into "Live chat" recently, but I missed him by minutes. He's got a load more questions so hopefully he'll get the e-mail notification of this post and come back & join us.

Pol.

I've noticed that Phydelis has posted a lot in "Live Chat" so hopefully he'll repeat his questions here.
Phydelis, .... When you ask about wing "Calculations"... are you needing to go so far as to work out the stress factors involved?
This may be beyond the scope of most modellers.
For example ... if we look at a built up balsa wing then the skin or covering of that wing will be handling the bulk of the strain.
In level flight the bottom surface will be under tension & the top surface, or spar, will be under compression. ..... this situation will be the opposite way around in the case of inverted flight.
I know you are doing an engineering degree so you may have to understand tensile strength & strain calculations .... unfortunately most modellers won't go this far.
Most of us will simply use tried & tested methods that have served us well for years.
I know that I for one don't know how much tension I could put on a 1/4 inch square strip of balsa wood or hardwood before it will snap .... this is complicated stuff.
I think you'll have to be a bit more specific as to exactly how far the university expect you to go ? ....... give us more details please mate.

That was one reason I rather like working with Depron. Each thickness of sheet has uniform physical characteristics.
It may not be an ideal material in all circumstances but its one less variable to worry about and its uniformity allows you to safely go closer to its structural limit.

For his thesis, rather than attempt stress calculations which are extraordinarily complex for even a simple airframe, would Phydelis not be better off physically load testing different wing construction samples in controlled conditions?
In the time he has available I doubt he could demonstrate to have found the lightest possible but it should prove it was at least strong enough!

This, in effect, is what experience has taught us over the years.

The only time I actually did a load test was on my first large span (60") Depron wing.

Neither a uniform load or to the limit (I didn't want to have to build another!) but with twice the total fuselage/motor/battery weight supported only at the wing tips my 'experience' told me this gave a bending load equivalent to pulling at least 4g. It hasn't broken yet!

Thanks all,
Just very few system at the university has firefox so most times am not so fortunate to logged into one. I was told i most calculated the bending stress and torsional stress on the wing. I understood that you guys uses more of experience in doing yours with everything am learning on this forum i should be able to do that. What i need to know is the design itself as i have settle for one build with foam and another with Balsa. I need to know what distant between the core and the leading and dragging edge and i want to use the foam to form some ribs and spar but am also thinking of using it as a block. which is prefereable? And what calculation do i need to do in other to get the wing dimensions since am considering an arm length as its length. (In calculation i mean : drag, lift, angle of attack, coefficeient of lift e.t.c)