Wing section proportions

Hi guys

I am currently working on a European design that I absolutely love for its lines but it has a wing only 12% thick. The designer has told me to build it with a thicker wing (2" he said, which relates to about 16%).

I do not know about high points or tip thicknesses.

Can some of the designers amongst us tell me the latest thinking on thicknesses and high point distances for PA models.

This gadget is about Nobler size and was originally built for a Fox 35. We will be using either one of our Schneurle .25s or .40s to power it and the .25s are preferred at the moment.

What can you suggest?

How big is the plane (span and wing area)? This will determine which engine would be best.

Does it have coupled flaps? Today's flapped planes generally use thicker airfoils than non-flapped designs. The old Nobler had an airfoil thickness of abut 16% or 17%. If you have the power, I would opt for a thicker airfoil.

However, if you are asking about airfoils and wings, you will probably get a hundred different opinions. My suggestion is, if you are changing the airfoil anyway, why not use the airfoil from a known successful design of today, but scale the wing to fit the plane that you are building. You wouldn't be the first, and you won't be the last.

Leonard Neumann

Geoff,

I made up a spreadsheet some months back (and naturally cannot find it at the moment) that listed the thicknesses & high points for many of the current popular designs. I also had a col for remarks which included my own observations of how the models flew in numerous conditions. It included my own designs and how they performed also.

The consensus I drew from this was:

The %thickness needs to increase at the tips anywhere between 3 to 7%.

The high point needs to be further back at the tips again by a similar amount.

If you go with the 25 I'd say something like 18% thick. If using the 40 something more like 20 to 23% (airfoil only - flap excluded).

There's a big difference in weight between a 25 & 40, so you'll need to consider the CG as well.