Trying to put some washout in a foam wing, per "instructions", (but without the washout
template that originally came with the kit) I seem to have not induced actual "washout".
What has happened is that the leading edge is still straight, inline with the root, to the tip...
but the trailing edge at the wingtip is reflexed UP at about 3/8" on each side.
This is a relatively smooth transition, starting from about 2.5" inward of the tip, to the tip.

Aerodynamically, is this going to somewhat closely approximate washout?
If not... do you think it will be harmful? I'm not concerned if it "won't help" but "won't harm".
I am only concerned if the condition might cause some horribly undesirable effect in flight.


For more info:
56" span x ~8.5 chord (9"chord at root... 8" chord at tip)
Approximate weight will put it in the 31-32 oz/in^2 wing loading range

It's a "not-so-scale" model of a Casa C-101, in ducted fan form.
The kit has some "not-so-constructive" instructions, and "not-so-scale" plans, too
I've decided to hit it with my best shot, and see how it goes... but I don't want to trash
it for something silly... which I could repair now if I needed to do so.

I'm expecting high landing speeds and all that. I know the loading seems high.
(Actual loading may be lower, owing to a somewhat wide fuse, and me saving weight
everywhere I possibly can find to do so. I'd like to get it in around 29/in^2)

I'm mainly curious if the "wingtips up" effect is going to kill me. Any thoughts appreciated.
If I must sand the sheeting off and start over, I will... but UGH!!! That's a lot of work.
Maybe better to get some new cores, if I have to start over, I guess.

Chris
(Edited for spelling)

That's as close to "real" washout as you can get, and like washout will be beneficial.
It won't be a problem.
You already know the most important thing, keep the speed up.
Paul

That's what I was thinking... and hoping someone would confirm/deny.
One of those situations where you just want a more experienced person
to give you a kick in one direction or another, ya know.

That seals it, then... work on the "Ghetto-Jet 101" continues

Thinking more on this, you could determine where the surface deviates from what it should be, and cut that part off, and glue in a replacement chunk of foam, sanded to fit.
Or it's also likely the sheeting if any or covering can be installed to reduce the reflex.
Paul

Depending on the type model involved... the smooth ttransition of the TE as described my be an IMPROVEMENT vs the original washout setup of the design.

If the panels are the same about the transition and the amount of twist... I'd leave it as-is and fly it.

The whole point of Washout is a higher AOA at the root than at the tip. Your explaination of how your wings turned out matches that.

Yeah... since the sheeting is already in place, I'm thinking of leaving it as-is.
It'll fly, or it'll make for a good crash video for the archives

If it flies, but is unreasonably prone to tipstall... I may do up a new set of cores then.

If unreasonably prone to tip-stalls... warp the ailerons.

The ailerons won't extend past the outer 3" or so, anyhow.
I've still got to add the trailing edge stock and wingtip blocks, too.
I could conceivably, at this point, simply slice the sheeting, (and partway through the foam)
on a diagonal, pin the edge to "level", fill the foam, repair the gap in the sheeting, install the
trailing edge and wingtip blocks, and have a nice straight wing with no curled up trailing edge.

Actually... maybe I should fix it. I've been toying with adding 2.5" each side anyhow, to get
my wing loading down even more. (from 31.4oz/in^2 to 28.8oz/in^2) (6.5lbs AUW estimated)
I could take that opportunity to add "proper" washout, I suppose... by twisting each extension's
leading edge down as it should be, and just contouring them into the existing wing as necessary.

I don't know if decreasing the loading that small amount will help... but it won't hurt
Thanks for the comments, guys.

SOME designs impliment the washout by the LE being drooped... others by the TE being raised. If the same angle is achieved at root and tip... there is little difference in most cases.

The typical .40 size trainer would impliment the washout at the TE. (as with the GP PT-40 and PT-60 kits)

if you have not added the fixed TE section and its outboard of the ailerons... you can reflex the TE up and add washout very effectively.

Chopping the wing skin and foam core at a diagonal could compromise the structure of the wing... I would avoid doing that if I could.

Decreasing wing loading decreases landing speed... and adding on to the wingspan is more effective for this than adding chord (higher aspect ratio is more efficient for the same wing area.) putting the washout into the added section would be reasonably effective.

Another way to help the center stall before the tip is to make the LE sharper near the center of span. This is usually a simple thing to do... Shave about 1/2 span of the LE flat... and CA on 1/4 inch triangle stock (hypotenuse to the flattened LE) then very slightly round it... and blend the last inch or two to the original LE shape. The center having a sharper LE makes the AOA more critical, and you get a sudden stall at center span with a delayed stall at outer due to the more rounded LE section.

There are many ways to delay or accelerate when a portion of an airfoil stalls... washout is just one.

I'm trying to imagine the geometry of this. It seems to me like you mixed in some dihedral with the washout by upturning the TE.

I think that the geometry of the wing you have made would be the same as a wing with added dihedral, with the LE drooped down. Think about it. This will add some more (possibly unwanted) lateral stability.

Would a drooped LE cause anhedral?! My deltas have a TE just like described above and it lands on a dime. I don't think anything but good could come from this twist. Did the math and it is 2.61 degrees washout (at the tip)which is appropriate for the plane you describe. The wing loading sounds high but keep in mind you will have to land fast anyway.[X(] Increasing wingspan will slow you down for landing and reduce acceleration and top speed. (extra drag) Unless you have deviated alot from the original kit specs you may want to fly it before you bash it. (or not)

Patrick

ps. being a low wing you may want dihedral to bring it to neutral. One of our AE's could address that. (how bout it?)[sm=thumbup.gif]