Well, I think I have calculated the wing loading number. But now that I have it - what do I do with it?

This kind of reminds me of taking a course and the prof ends the overview with, "are there any questions?"

"Hell, I don't know enough about the subject to ask an intellegent question!"

WING LOADING - It doesn't tell me (at this point) if the engine I have on the beast will fly it or not

I obviously know the weight of the aircraft, and I know thw size of the wing.

Q) Is this magical number going to tell me if it is a good number or a bad number?

Q) Do I need lots of runway or a short one?

Q) How important is the engine?

These might seem like some very trite questions but if I don't know the answers, what's the sense in trying to do things properly?

I've been scratch building for over 20 years. All of my planes fly - some better than others some worse.

If I can predict my results - that would be awesome

any and all guidance is greatly appreciated.

marwen1

The "Cubic" wingload, weight(g)/wingarea(dm2)^3/2, is good guide to how the plane will behave. A number of 4-6 is typical for free-flight, 8-10 is a good sports plane and 12-14 (and up) is warbird territory.

Then you choose an engine to suit. A thrust of 1/3 of the weight is about minimum for sustained flight, a thrust near equal to the weight is fine for sport flight and for 3D you need more power.

It is as simple as that....

A 1:1 ratio of power to weight [or close to it] is very easy to acheive with an engine that fits within the lines of the aircraft. Nice to have surplus power.
Free, online thrust calculators will give you a ball park idea of what you've got.
From there, wing loading and airfoil is a matter of personal taste and the goals that you have for the plane.

Read this article:

http://findarticles.com/p/articles/m...g=content;col1

Well, my DELTA is 48" for the root, the overall WS is 60", and it weights just over 10 lbs
so, if I look at the R. or L. half it has a 6" clip on the wing tips - making the cverall shape of the 1/2 wing - a screwed up rectangle. I think it's what is referred to as a TRAPEZOID

According to a variety of research - my DELTA is now at 780 sq. in. and just around the 10 lb. area. Accordingly, this all important number is coming in at around "30".

If I were around 1/2 that size - say 36" WS and in the 6-7 lb area. the loading is almost the very same!

A small .40 ENYA i used to have in the late 80's made the 36" version kick out at about 45-+50mph.

This LARGER version of the same plane - as I say - is 60" WS.. I now have a ROSSI .81 DF to power this larger bird.

The DF is for "DUCTED FAN". - with a tuned pipe!

From what I've seen so far, the old ROSSI engines are like running straight TURBO.

Now then, PROPS - I have an 11/7 MASTER AIRSCREW (PUSHER) on it - I also have some smaller ones, too

What to do?

I've run the ROSSI a couple of times but I'm waiting for a solid BULLET for the nosecone. It'll thread right INTO the prop shaft.

Right now, I barely have enough threads to keep it on

marwen1

If you have a computer program capable of using MS Excel then download "Sailplane Calc" and if you input some very easy measurements on the "Wing Tab" it'll easily calculate Wing Loading and much, much more.

I realize the name implies Gliders but it's useful for any kind of plane.

Curtis
www.TailwindGliders.com

I'm a bit lost here, is there a specific question?

10 lbs and 780 inch^2, should do fine with a cubic load of 12.8.

A 48x60 delta is pretty big...bigger than my computer desk.

That engine belongs in a 36 inch span delta if the object of this exercise is speed and not just noise.

To the original post:


Some of the other factors:

Size, a large model work well with a higher wing loading than a small model.
Scaling and how it do affect wing loading have been discussed in this forum before.

Wing chord large chord gives a larger Reynolds number at the same speed and allow higher wing loading
Speed, higher speed is the flip side of above.

Planform, large span high aspect ratio wings work better with high wing loading than the same area on a low aspect ratio wing. (As long as the chord dont get to small.)
Some argue that the absolute span is as important as the aspect ratio when considering the wing.

Power, more power will fly a higher loaded wing.

In many ways the wing loading numbertell something about how a plane at a certaian weight and planform will perform. It's only useful for comparing models at the same kind of size.

That is exactly why one shouldn't look at the wingloading but the "cubic wingload" instead, as meantioned above, it takes care of the scaling problem.

Mr Cox's cubic loading value of 12.6 pretty much matches what I think the 2D regular wing loading is saying. At 780 sq inches and 10 lbs it will fly quite well but it ain't gonna be a floater slow flyer sort of model. Being a delta it may offer some funky high angle lift effects that'll let you slow it down a lot for landing by forming a strong vortex lift over the wing with a high angle of attack and lots of lift for a slow approach. Play with the high angle flight mode the proverbial 3.5 mistakes high at first until you get a handle on how it handles in that mode.

As for the thrust to weight I foresee F18 on afterburner like performance from that engine on a 10 lb model.

It's going to be WAY bigger than 780 square inches. I'll bet he's describing more like 1500. This size model is out of my league....but my guess is it would take one of the 1.5 cubic inch [or so] model engines to be a good performer.
This size airframe will need X amount of prop disk and a piped DF engine's only going to tolerate so much prop before it refuses to stage.
I'll be interested how this all turns out, mostly because I'm shooting from the hip with this opinion and have no real world experience with this exact application.

Yer right CP. I guess we shouldn't trust Marwen's math at face value.... The average chord is (48+6)/2= 27. 27 x 60 = 1620 sq inches or 11.25 sq feet. So the wing loading is actually a feathery 14.2 oz/sq ft. That's just barely over thermal soaring glider wing loading territory.

Holy Cow! Did I ever open up a can of worms.. LOL

Bruce: The formua I used was pretty close to what you had above. What I have here is a TRAPEZOID.

I measured my root from the imaginaty point (that isn't there) of my DELTA point to the trailing edge. That was 48". Add the 6" for the wing tip length = 52" /2= 26 (AVERAGE CHORD)

WING AREA = WING SPAN X AVERAGE CHORD

WING SPAN IS 60" - A TRAPEZOID ONLY MEASURES 1/2 OF THE WHOLE WING (WS/2=30)

26X30=780


combatpig quote "That engine belongs in a 36 inch span delta if the object of this exercise is speed and not just noise.


Are you referring to the ROSSI engine? The FORCE ONE (in question) was originally designed by laddie mikulasko way back in to early to mid 80's == it came out as a 36.5" Ws PUSHER. I've built that plane
5-6 x and I only needed a .40 on it


I started this thread simply because I don't know much about WING LOADING. eventually, a variety of answers will come out of the woodwork. LEARNING what I can from this forum is what it's all about. (I thought)

I have been under the weather for the past couple of years but its SLOWLY coming back. Hopefully, I'll get this thing in the air before the end of the flying season. - if not, well, there's always next year.

In the middle of all this stuff I have a 12 year old child with Cerebral Palsy. She has been the Youth Embassador for the MANITOBA EASTER SEALS. Taking her to and from all the events that is required really cuts into my weekend flying time.

Not only that, the C/L club I belong to (THE PERFECT CIRCLE FLYING CLUB) has made her an honorary member as of last week. She now has some more responsabilities as their Embassador - but at least that gets me out to one of the fields.

Thank you ALL for so much incredibly valuable information

marwen1

Marwen, first off 48 + 6 = 54 and not 52. And when you get the average for the wing chord by adding the root and tip and dividing by 2 you have already allowed for the shape and the average chord is the average chord. No need to divide by two for the shape. So it's 27 x 60 which is 1620 sq inchs. You've got yourself a Vulcan like "balsa overcast" there....

Thanks Bruce;

The formula I got was from another website. Nevertheless, by using the wing loading nomogramm from the rcu site itself, I'm coming up with a loading of about 14oz/sq.ft. Whatever that means , at this point - I really don't know

marwen1

14 oz/sqft is light, but typical of deltas, there is no fuselage, tailplanes etc. I fly a 48" '362' delta which is well powered with an old OS .40, and it weighs around 4lb for a similar loading to your calculation. You need to know that in order to use the very high (=slow)landing attitudes possible the prop needs to be at the front. The top speed will be much better than you would expect, due to the low loadings, and the low drag at the very low AOA needed to fly. If you start doing 'high alpha' stuff the drag rise is a bit higher than with the normal layout, and you need to carefully transition to normal flight in order not lose altitude, but the speed range and acceleration is a bit better than normal stuff. Balance around 50% centre chord, and mainwheels just behind the balance point, helps both takeoff and landing. Other than that the usual stuff applies, keep it light and have fun.
Evan, WB #12.

Matthews calculation seems correct to me...

I'm a little confused about your planform, here are two screenshots from Flying Wing Calc available at TailwindGliders.com

Anyway, there's all the information and more for wing loading, but I have no information for power requirements.

Curtis
Montana

Like I said Marwen, you've almost got a thermal soaring delta there. A typical 100 to 120 inch saiplane these days runs with wing loadings from 8 to 12 oz/sqft. And in stiff winds it's not uncommon to ballast up the performance sailplanes to 14. A more typical wing loading for a "normal" model with a smaller wing of this size would be up in the mid 20's to mid 30's for wing loading.

For power you won't be shy. The .90DF engine with the correct prop will easily generate more than 10 lbs of thrust so you've got true unlimited vertical ability with this design.

Be careful with the wing loading data you get by running the formula (model weight inounces divided by (weight in ounces x 144) as even though that formula is correct it's not aerodynamically correct. Somehow you have to have an elevator to counteract the pitching moment of the wing thus I have a "effective wing loading" and have reduced the wing area by about 30% to account for the tail, even though it's a delta it still has a tail, aerodynamically speaking.

Curtis

That's true, But even if I take the rule of thumb where the rearward 25% to 30% of the wing area is used as the stabilizer then it's still only up around 19 to 20 oz/sq foot.

In truth though it's not so much about effective wing area as it is that airfoils that are self stabilizing tend to have a lower maximum lift coefficient. But it comes down to the same thing at lower speeds.

But by any standard be it the full wing, the front 2/3's as the "effective" wing area or a lowered max lift coefficient. He's still got a very light wing loading for this size of model. It isn't going to have any big issues with slowing down even in "normal" flying mode. And from there he can play with the nose high vortex lift mode that high sweep angle delta wings are so good at.

BMatthews,

Exactly! Thanks for the clarifications. It helps us all.

Curtis

Could you do some calculating on this.The Rotating wing has a 6ft. span re-inforced foam with 6 inches from leading edge to rear edge. meaning 3 ft. on either side of the hub.I just want to get this in the air and flying.Upgrades will follow.I have planes for a powered steerable front wheel for Taxying and short trips without rotating the wing.Electricity would be switched from wing motors to front wheel!!

I have a Question but, I have some numbers for you.The Aircrafts weight is 4 pounds with everything battery for motors,battery for reciever weight of wing and weight of body including gimble.The Rotarywing is 6ft.in span 3ft. on either side.And 6 inches front edge to tailing edge.Can you tell me at what r.p.m. it will lift off at ?