cyclops2

I am using the CAP plan # 16 of the Avro Vulcan. 60 inch W.S.
I have cut out the wing outline in pink foam. Have been using the airfoil below. Was in a family of........Flat bottomed Clark Y's...........

If I use it at the root or tip, what areas of it should change for the 4 different sections ? Or can just 2 foils do the job.
I will fly with some UP elevator all the time. O K with me.

A hand pencil sketching over what I posted would be fine. Sport & scale flying only.

da Rock

Actually, you're not providing near enough info to get good results from.

You need to provide the planform. And some measurements. And don't be surprised if the response isn't too huge. In fact, it's actually true that some wings are going to stall at the tips first no matter what the difference in airfoils is from root to tip. And twisting can't do but so much. It is going to depend on the planform.

It's an unfortunate belief in the flying model hobby that there is a way to stop tip stalls. It's just not universally possible. And in most cases it just doesn't happen.

Depending on your model's planform, it could be helpful to change the airfoil from root to tip. But helpful is the best promise.

Truth is, the advice that's probably going to have as good a chance of working is to simply make the tip airfoil a couple of percentage thicker and build the sucker. BTW, with tapered wings, if you don't reduce the airfoil thickness from root to tip, you get that automatically. (But tapered wings stall at the tips first naturally and aerodynamic twist can't stop that in most cases.)

Whomever helps you will probably need to know the root chord and tip chord to even begin to help.

Nathan King

What are you looking to do with the airplane? I ask because this can be considered a good characteristic to have when doing aerobatics. Remember, there is one way to avoid a stall that causes a wing to drop. Stay in coordinated flight and the airplane can't possibly drop a wing. If it does, correct with rudder and not ailerons.

As da Rock mentioned, we need more information to provide useful advice. Adding a few degrees of washout can work wonders, but won't make the airplane immune. Frankly the Clark Y has pretty tame stall characteristics. I doubt you need much of anything.

P.S. Why the heck do you fly out of trim all the time? I know some people like the feeling of pulling up all the time, but it's a mental issue. A properly trimmed airplane will be much more of a pleasure to fly.

BMatthews

That airfoil is not a wise choice for a delta shaped flying wing. You'd be far better off with a symetrical airfoil or one that is intended for flying wings. The ClarkY like shape is going to require so much reflex or washout to stabilize it that the wing is going to just look plain odd. On the other hand a symetrical airfoil will only require a few degrees of elevon up for the reflex to stabilize the wing in pitch.

Best of all if you go symetrical it'll even be more scale. The real Vulcan used an airfoil that is almost completley symetrical.

Nathan King

Oh, I didn't notice this was going to be on a Vulcan [sm=red_smile.gif]. What I said still holds true, but BMatthews is right - the Clark Y is not a good choice for a flying wing.

cyclops2

The inner 25% is pretty symetrical. Center 50% is a definate undercamber. Outer 25% is a very slight undercamber. Both wing halves are identical in the large model.

cyclops2

Busy web will not let me post picture of the wing. Do it tomorrow.

cyclops2

I want to fly it.

Could someone post a picture of a good airfoil to use? I can then enlarge it to what I need.

Many thanks.

Mike Connor

My Feedback: (5)

Clark Y on a delta? Yikes! Deltas fly by their own set of rules and tip stalls are usually not a big problem. I would use something like a NACA 0006 up to a NACA 0012 symmetrical airfoil with out wash out or increasing the thickness % towards the tips.

da Rock

You betcha'

It's often said that deltas are almost impossible to stall.

cyclops2

Deltas are a 2 edged sword.
The SAAB Draken took enough young pilots when they stalled into a flat spin. Apperantly you can not recover from a flat. This is from a Swedish book about the life of the plane.

I know in "Jaynes Fighters Anthology" it is impossible to recover from any height. It is the only plane like that in all of them. Spinning leaf all the way down. Probably would spread your arms all the way down.

Thanks for the safe & easy way to sand my wings into a stabile flier.

BMatthews

I went looking at some Vulcan stuff and found this rather confusing picture...

http://www.spxtraining.com/niactest/.../XM605web3.jpg

It clearly shows that the airfoil of the outer section is anything but symetrical. However for your model I still strongly suggest you just go with a symetrical airfoil.

It would be nice to say to use the scale airfoils but since we don't know the ins and outs of how they chose these options and trimmed the aircraft and at what lift coefficients they typically fly at it's best to stick with the model aerodynamics that we do know.

cyclops2

There is a neat site with some unbelieviable statement that the Vulcan can beat a F-15 in high altitude mock dogfights.

But when you look at the wing load of the Vulcan it becomes real.

www.users.zetnet.co.uk/mongsoft/vulcan_tech

Flypaper 2

Another good one is the Avro Arrow, where it looks like the wing is in upside down. The top of the wing is flat and the curve is on the bottom. Sort of built in reflex. Where the cut is on the wing, it has leading edge droop from there out.

combatpigg

My Feedback: (3)

An ounce of weight control is worth a pound of airfoil "cure" when it comes to stalling. Pink foam is a relatively heavy way to begin just about any .60 and under project. I would use the foam wing panels but slice them up so you can take tracings for balsa ribs and build a conventional built up wing.
The masters of building light with foam cores put way more work into those cores than what meets the eye...in the long run a one of a kind built up balsa wing will be less work if saving weight and maximizing strength is your goal.

cyclops2

Hi combat.

The flying weight will be about 3 with the DEWALT cells.

BMatthews

That may explain a lot about why I can't understand the leading edge shape. If the upper rear is near flat and the lower side has some curve in the rear portion then you've got yourselves a reflexed airfoil. And that would explain the drooping leading edge shape.

combatpigg

My Feedback: (3)

A 60 inch span [huge] delta with scale looks that weighs 3 pounds RTF? To put that into perspective, a 32 inch delta made from kite rods and balsa will come out at 2.5 pounds RTF with a 13 ounce engine, standard RC gear and make a moderately light plane to fly. What you're proposing will be quite an accomplishment!

BMatthews

Pish.. a free flighter could do it....

He's got you cyclops. A 60 inch Vulcan is a LOT of airplane. The good news is that even at 5 or 6 lbs it will still have a light wing loading.

cyclops2

Blue foam gets NO respect.

The complete bare 80" A-10 weighed 4 while ALL the parts were still solid.

60" of Vulcan is a 3 piece of cake, compared to the A-10. [>:]

combatpigg

My Feedback: (3)

If you make it light enough......you know how the rest goes.
I've never seen one of those flying stop signs [Roun'tuits?] fly, by I've heard that they flew pretty well, inspite of having a "wrong" airfoil.
How much of the 3 pounds will be devoted to the power system and onboard equipment?

ol_seabee

I just kind of scanned this thread so excuse me if it's been mentioned but can't the outside ~10%-20% of the wing be semi-symmetrical?

"flying tips" is that common?

da Rock

You betcha. If you're talking about changine the airfoil from root to tip, that's done all the time. It's very, very common in full scale, and happens all the time with models. Matter of fact, one of the greatest features of cutting foam cores is how easily you can create a wing that starts with one airfoil at the root and changes progressively to a different airfoil at the tip. And the usual reason to do that is to make the tip stall at a slightly greater angle of attack.

ol_seabee

ya thats what I meant

I thought I saw a scratch built laser with flying tips in the '80s down in Naple Fl

it flew real nice[8D]

rmh

This adea was use by Ron Chidgey on his aerobatic models -in 1970/80 time frame

Depending on whom you talk to it helps
frankly I never saw it as benificial -theory says yes on very large craft -full scale
On our own pattern models we have gone to 10% tips and no washout /semisymm/ whatever
they land at a walk -
it has to do with low wing loadings an lower aspect ratios which ar more forgiving
The primary cause of tip stall is that the model looses directional control - so one wing "leads" the other at critical low speed
You can proove this by doing "recovery high controlled fly bys and reaching a stall- if a bit of rudder is trimmed in - the model will fall off to one side. "tip stalling"
some small well designed tip ends also work to prevent the problem -I found full scale aerobats now also doing this here is an example