stevegauth30

Quick question for all you aerodynamic gurus. If you had a fully symmetrical, constant chord wing, like on a Rearwin Speedster that I'm building, and you increased the thickness of the wing by adding cap strips and sanding them down to nothing at the LE, and TE, what would be the change if any to the flying qualities? Wow, that was a long winded question. Do you follow? So basically, the thickness increased by 3/16 everywhere but the LE and TE. Will it even affect it at all? Sorry if it's a dumb question.

da Rock

There have been a number of families of airfoils that were symmetrical profile. They were often ranges from very thin to very fat. From one to it's next closest kin, there was almost nothing of significance between the two.

What you're wondering about has been sorted out by control line aerobatics designers back when that was a major discipline. Noone really had proof there was any difference.

What you're suggesting, thinning fore and aft, actually results in a modification that moves the thickness of the profile aft. There have been lots of C/L models based on those kind of airfoils, and nothing really stood out.

BTW, the best way to do that job is to thin the ribs where they will be cap stripped a touch less than the thickness of the strips. Then you don't change the profile at all.

A lot of us "upgraded" a bunch of our C/L kits with cap strips back in those days. We always thought we had better flying planes than everyone else.....

All Day Dan

My Feedback: (5)

You won't notice any change. Dan.

stevegauth30

I didn't really think it would change it much, was more just curious. The whole reason I put them was because I inadvertently sanded down a bit too far, and you could see the spars along with the ribs through the fabric. I also wanted to accentuate the ribs like the full scale. Thanks for your answer, Steve.

BMatthews

All else being equal making the airfoil a little thicker like this should delay the stall by a slight amount.

The reality though is that you likely won't see any change at all. Especially since this is a film or fabric covered wing.

One thing I'd watch for though is to make sure you sand the cap strips so that you maintain the original point of maximum thickness. To help with that you may want to lay a strip of 1/2 or 3/4 inch masking tape along the wing centered on the original point of maximum thickness. Sand just to the edges and fair the strips off to the leading and trailing edges like you planned. When you're done pull off the tape and give the whole works a couple of more swipes with the fine sandpaper to feather in any steps left by the masking tape trick.

stevegauth30

Sounds like a good little trick. Thanks.

eddieC

My Feedback: (2)

What I'd like to know, Steve, is how do you get your sig/email addy to overlap the text area?

stevegauth30

I have no clue. I've been told about it a bunch of times, but in my screen, it's broke in half and on two lines. Different than what you see. I'd love to change it, and loose the @comcast.net part, but can't figure out how. If anyone knows how to change your name here I'd love to hear about it.

BMatthews

You need to make a request to one of the Community Moderators. Us normal forum mods don't have access to such tools.

DaneMcGee

The airplane will fly the same. You ain't gonna hurt it,.