JUst building my scratch build from foam, and I have no idea how thick the wings should be
I currently have them about 20 mm at the front and 5mm at the back, is this ok ?
btw its a trainer so Im not too concerned about speed

Simple answer is 'it depends'. the wings on a full size B-17 Flying Fortress are a LOT thicker than an ultra micro indoor RC model, yet neither one is 'wrong'.

Is 20mm the right thickness... I've no idea.. tell us some more about the model.

FWIW airfoils on air-planes normally have their thickness stated as a % of the wing chord (width). Most RC model wings fall in a range from maybe 5% to 15% thickness (small model usually have lower % thickness airfoils). So to fall in that range your wing if 20mm thick would have to be between roughly 150mm and 400mm chord.

Sorry I have no idea what the wing chord means
Its a high winged trainer with a 32'' span if that helps

Wing chord is the distance between your wing leading edge to trailing edge ( fancy for from the front of the wing to the back of the wing )

ok thanks, mine is 130mm so i guess its a bit thick

don't worry, just set the cg right and your plane should fly.
next time a quick google search will help you find what wing chord or something else mean.

The thickness of an airfoil depends on the following things:

1. How strong do you want it to be.
2. How slow do you want to fly. (and still maintain lift)
3. What sort of glide ratio do you expect.
4. How fast do you want to fly. (related to #2, but not the same thing)

The chord (combined with the length and of course weight) will determine your wing loading, wing loading will tell the plane how fast it can fly, the lighter the plane relative to it's wing's surface area, the slower it will fly (to a certain degree). The curvature of the upper surface (camber) will also have significant influence on how slow you can fly with a given wing loading.

Thicker arifols stall "later" (excuse my aero-slang), because the airflow helps maintain laminar flow with more extreme angles of attack.

Of course, it all depends on your materials. For example, you can build very long and thin wings with carbon spars, wings so thin, neither wood nor steel will stand a chance. Here's an example of what I'm talking about.



You can't do this without carbon.

Originally Posted by vengeance111

Sorry I have no idea what the wing chord means

That's why I put (width) in brackets after the word chord

Yep, a 20mm thick 130mm chord wing really is a bit thick. Of course it will fly if you give it enough power (assuming the rest of the design is ok) but wont be anywhere near optimum. Generally small model perform best with very thin wings, thinner the better really (subject to adequate strength). Thick airfoils only work well on quite large models.

Good luck with your project.

Steve

The OP and others interested in designing their own planes should purchase Carlos Reyes' RCadvisor's Model Airplane Design Made Easy: The Simple Guide to Designing R/C Model Aircraft or Build Your Own Radio Control Flying Model Plane

http://www.amazon.com/dp/0982261322/...advisor.com%2F

You'll also learn about KF airfoils which don't really have a "thickness".

Originally Posted by vengeance111

JUst building my scratch build from foam, and I have no idea how thick the wings should be
I currently have them about 20 mm at the front and 5mm at the back, is this ok ?
btw its a trainer so Im not too concerned about speed

It depends on what kind of flying you're doing.

I have several planes with 8% thick wings - they are FAST!

I also have planes with 19% thick wings. They are nice and draggy for aerobatics.

The best books for model aircraft design reference are Andy Lemmon's book (if you find a copy, DON'T sell it!), and Martin Simons' http://carstensbookstore.com/moaiaebymasi.html and http://carstensbookstore.com/moflbymasi.html

Andy

Thanks guys Ill cut them down a a bit today

I think this:

Originally Posted by vengeance111

JUst building my scratch build from foam

.. and this:

Originally Posted by vengeance111

Sorry I have no idea what the wing chord means

.. are incompatible.

That said, loads of advice here and certainly no lack of info on this site..
..a

Well thanks for the advice but its going well so far
Ive never flown a rc plane before anyway so its a first for everything

Here's a Clark Y, it's a great flat bottomed airfoil.

Originally Posted by AndyKunz

The best books for model aircraft design reference are Andy Lemmon's book (if you find a copy, DON'T sell it!), and Martin Simons' http://carstensbookstore.com/moaiaebymasi.html and http://carstensbookstore.com/moflbymasi.html

Andy

Found an Andy Lennon. Is this the book you're referring to?

http://books.google.com/books/about/...d=RfEDoNNRHjQC

Will