Stunt profiles

Hi

Following on from the discussion on sharp vs round LE, it seems to me that the desired profile characteristics are:

Does not exibit hysterisis loops or other anomolies in the performance curves.

Has a slow and controlled stall.

Seems heigh CL max is not necessarily required. We are mostely interested in smooth handling and and stable Cmo.

If these are the requirements, then the following might be a guide
to the profile shape we are loofing for.

If the max thick point is fairly forward say around 15-20% of chord,
that allows for a smoothly rounded and blended LE. The section need
not be so thick as the airflow on a thinner section of this type
would likely be quite stable over most of it's trim range closser
to Cl max. It would also allow the aft part of the profile to be quite straight or even concave which would help boundary layer
reattachment should a seperation bubble form or in the case of
flaps a less severe preasure gradient over the convex side of the
flap hinge.

This would be somewhat of a departure from current practice and
has most likely been looked into before. Not seriously proposing
a change, just curious.

Does anyone have good solid quantitative information to share
on this type of section?

Yes, although Nunn-Bush no longer is in business and so their wingtips, favorite shoes of mine, are no longer available, putting an end to my entire airfoil data base.

When and if I need a new airfoil I go to Rush. Other than that, blunt, thick and sorta tapered to the rear seems to work quite nicely.

LAST EDITED ON Jun-04-04 AT 08:37 AM (CDT)
 
>Yes, although Nunn-Bush no longer is in business and so their wingtips, favorite
>shoes of mine, are no longer available, putting an end to my entire airfoil data base.
>
I always thought for Wingtips you wanted another brand; but like so many other things, the brand name leaked out of memory (I wore a few pairs of whatever they are/were way back when I was forced to wear suits and ties -- yup, George, Florsheim!) My favorite Nunnbush shoes were the "Rex-Flex" because of the dual last -- narrower heels (a "B" would have an "A" heel).

>When and if I need a new airfoil I go to Rush. Other than that, blunt, thick and
>sorta tapered to the rear seems to work quite nicely.
>
My current favorites are New Balance (still narrows - the only athletic brand I've learned that I can buy fairly readily on a local basis that is regularly available in a narrow).

.

Kiwi

>My current favorites are New Balance (still narrows - the
>only athletic type I know of made in a narrow).
>
>.
>
>Kiwi

Many running shoe companies offer width sizing for their more popular models. For example, Nike offers different width in their Pegagus trainer, but not in, say, one of their racing shoe models.

If you have a very narrow heel, swallow hard and try a women's model.

LAST EDITED ON Jun-03-04 AT 09:29 PM (CDT)
 
Ken,
Sounds like a Ringmaster 'foil yo me.

Dan,
Never heard of using a wingtip to draw an airfoil before. <oops, smiley deleted>

Edit: Kiwi, Florsheim?

If Da Dirt used wingtips to draw his airfoils, what did he use to draw his wingtips? Just had to ask. I really can't picture Dan wearing wingtips.

There was an article in Stunt News a few years ago that claimed the blunter the airfoil, the less "groovey" the model. About that time, I saw the first profile Cardinal fly locally, and it appeared to track quite well. The airfoil is thick, but not too blunt. I don't know if this is the Patternmaster section, or something from Windy's old wingtips. Maybe Redwing boots, size 13's? Steve

This thread has gotten plumb weird.

>This thread has gotten plumb weird.

Sometimes that's the only way it can go after one of Danny Boy's Bon Mots!

.

Kiwi

Don't pay any attention to Dan when it comes to airfoils. I seem to remember one of his early old time creations built with the lost balsa technique and curly que ribs. It think he said they were 1/32 ribs with 1/16 cap strips. Couldn't have been too bad though because Chris Cox used to beat Dan at the NW Regionals.

See pictures of said Viking below from that contest.

>Has a slow and controlled stall.
>

I agreed with the rest, but can't see why this matters very much. If you stall, you messed up, and what happens afterwards is pretty well irrelevant. As long as it's nice and well-behaved up to the maximum Cl required, that's about all you need.

As should be clear by now, many of my supposed friends are not to be trusted with cameras and video equipment.

But hey! How about those gangster whitewalls on my Viking? I still think that is really funny...

Viking was built with 3/32" ribs, obviously to no real good effect. Zilch X was built by first under-cutting a rib by 1/16" top and bottom, then creating a Formica template to match. Ribs were fabricated from C-grain 3/32" balsa. Capstrips from substantial 1/16" wood were cut to 1/8" wide.

The result is a wing which amateur photographers seem to avoid as it hasn't gone all wonky on me while still appearing to be constructed in a period-correct manner.