stunthanger.com
General control line discussion => Open Forum => Topic started by: Robert Zambelli on April 05, 2021, 05:15:16 PM
-
Let's hear some of your methods!
Bob Z.
-
I'm basically lazy. I use my computer and my CAD program. It also measures the M.A.C. as well. Yes, it's cheating, and not discussing, using, and developing the skills to accurately measure the wing area manually. I told you I was lazy didn't I?
-
For stunt, or for some class where it matters?
If it's for a class that calls out wing area, I'd do it the way the rule book says. If that doesn't say (sorry, I haven't looked) I'd either do the high school algebra calculate the area of a trapezoid method ((root chord + tip chord)/2 * span) or I'd put the outline of the wing on graph paper and count squares.
If it's for stunt -- who cares? There's so many variables, that if you're within 10% that's good enough. For the most part we modellers do it wrong anyway (full-scale airplanes count the wing area not including the fuselage -- modellers just argue about what's "right").
-
I usually just look at the title block on the plan or the kit box lid, but that's just me!
Type at you later,
Dan McEntee
-
Assuming straight or tapered wing panels? - Add root chord width to tip chord width and divide by two. Multiply that figure by wing length for each panel then add the two together. Tips if 'large' can be calc'd in a similar fashion and the total will probably be within a few sq. inches.
-
Simple math for straight elements.
For curves such as wingtips --
Get some homogeneous cardboard like from a cereal box and cut it to 100 square inches. Weigh it.
Trace the shape of the curved onto the same cardboard, cut it loose and weigh it.
Simple math will give you the results you need.
-
Calculating the area of a polygon
-
BINGO!!!!!
Any shape, no matter how complex.
Simple math for straight elements.
For curves such as wingtips --
Get some homogeneous cardboard like from a cereal box and cut it to 100 square inches. Weigh it.
Trace the shape of the curved onto the same cardboard, cut it loose and weigh it.
Simple math will give you the results you need.
-
He beat me to it. This was taught me many years ago. This is when a gram scale works. D>K
-
Interestingly, in aero calcs we include the wing area that's "inside" the fuselage, not just the exposed wing. There's a reason we do it but it get's fairly (OK, extremely boringly) esoteric. All I'll tell you is use the wing area before it goes into the fuselage.
Chuck
-
The arithmetic is easy enough. Where we run into trouble is the argument whether or not to include flaps as part of total area. Many "experts" do not consider flaps to be part of the wing area.
I tend to go by plan view; looking down on the wing from a distance. Looks like Wing Area to me! Air flows past it, just like the rest of the wing.
So I include flaps as part of wing area.
-
Interestingly, in aero calcs we include the wing area that's "inside" the fuselage, not just the exposed wing. There's a reason we do it but it get's fairly (OK, extremely boringly) esoteric. All I'll tell you is use the wing area before it goes into the fuselage.
My new plane has wings that bolt onto the side of the fuselage. Does the part that’s not inside, but should be, count?
-
My new plane has wings that bolt onto the side of the fuselage. Does the part that’s not inside, but should be, count?
Always
-
I use 3/4" Baltic birch plywood for the weight templates. It is extremely uniform and I can use a larger scale for more accuracy.....
The Divot
PS--I have for sale a heavy duty Nobler components set. Extremely durable. FOB
-
If 1/10th bolted inside the fuselage , you could bolt ten through the fuselage, and you wouldnt need any wings . ;) .
-
The arithmetic is easy enough. Where we run into trouble is the argument whether or not to include flaps as part of total area. Many "experts" do not consider flaps to be part of the wing area.
I tend to go by plan view; looking down on the wing from a distance. Looks like Wing Area to me! Air flows past it, just like the rest of the wing.
So I include flaps as part of wing area.
They are not "experts".
-
My new plane has wings that bolt onto the side of the fuselage. Does the part that’s not inside, but should be, count?
Yep. Pretty weird, eh?
-
Other than things that can be defined discretely (i.e I have 5 apples) there are no exact measurements, everything is approximate S?P
-
They are not "experts".
You know who they are. They are the few who have "the answer" for stunt design, engine handling, fuel, and judging. If you dare to disagree,. you get their response, "you are not in the 'top ten', so you need to heed what I say." I have learned to treat these people with caution.
-
For certain, I don't qualify for "top 10". <=
Olds school method, with known cardboard of density x lbs./sq. in. (or weigh yourself), make a cardboard cutout of 1/2 the wing (right or left panel). Weigh it, multiple by its known density per square inch. A little crude, but works. (Used to calculate a model rocket center of pressure via similar method.)
Or, Buy Brodak or Sig, then you know the wing area. :!
-
There’s a mechanical drafting tool called a planimeter. It’s essentially a mechanical computer that integrates the area inside of a closed two dimensional shape. I used to use them at work to estimate the weight of a complex castings.
If you really want to geek out, I see used ones on eBay and Etsy for under $100.
https://en.m.wikipedia.org/wiki/Planimeter
-
Simple math for straight elements.
For curves such as wingtips --
Get some homogeneous cardboard like from a cereal box and cut it to 100 square inches. Weigh it.
Trace the shape of the curved onto the same cardboard, cut it loose and weigh it.
Simple math will give you the results you need.
Great idea
-
Straight line shapes pose no problem in measurement. For odd shapes, plot or trace the wing panel full size on grid paper. My grid paper has 10 divisions per inch. Then, simply count the squares inside the outline. If a line bisects a square,then the 1/10 divisions help. Or sufficient accuracy by just estimating the % of a square.
-
Great idea
Old idea.
-
For a 2 Dimensional flat plan view a planimeter is the go to but if it's wetted 3D curved area the cardboard cant be beaten.
There is another method using perimeter and string that gives a quick and dirty 2D estimate also.
Chris.
-
I wish I knew the wing area of this.
Or do I already know? ;D
I might finish this model and do a paint finishing build.
My guess is 2 days. I'm thinking TRUMP.
-
I wish I knew the wing area of this.
If that is a true ellipse, area is the span times root chord divided by 4 times pi.
Keith
-
If that is a true ellipse, area is the span times root chord divided by 4 times pi.
Keith
Keith,
Thank you,
And I have absolutely no idea what the area is.
I'll do that, be nice to know the wing loading, I can do that once I have the area.
Thanks again.
CB
-
Many "experts" do not consider flaps to be part of the wing area.
If my "many", you mean one, then yes.
Brett
-
Maybe he had Fowler flaps in mind like on the big stuff he flew.
-
In Thomas A Edison's book he caught an employee trying to derive formula to calculate the volume inside a light bulb.
Edison told him to weight it full of mercury and get back to work.
-
The formulae for computing the area of a TRUE ellipse are valid. But a wing drawn up by a modeler is likely to be just "elliptical-looking".
Another close-guess method would be to multiply the span times the AVERAGE chord computed from measurements taken at intervals. The span and number of the intervals would depend on how accurate you want the result.
-
The formulae for computing the area of a TRUE ellipse are valid. But a wing drawn up by a modeler is likely to be just "elliptical-looking".
Another close-guess method would be to multiply the span times the AVERAGE chord computed from measurements taken at intervals. The span and number of the intervals would depend on how accurate you want the result.
Would this pass the elliptical test?
Now if I cut the wing tip off a tad, like many modelers do for the slider, is the wing then still an elliptical wing?
I didn't design the wing in the photo. I nicked it from an ARF Spitfire wing I had from my R/C days.
I did design this one.
-
I would say that is not AN ellipse, but two different half ellipses joined at the high point. So if you went the "higher math" route you would have the compute the areas ahead of and behind the high point.
-
Charles, if you already have the wing drawn up in a CAD program then that should be able tell you the area.
Chris.
-
I would say that is not AN ellipse, but two different half ellipses joined at the high point. So if you went the "higher math" route you would have the compute the areas ahead of and behind the high point.
Here's the higher math for you: (pi * (c1 + c2) * b) / 4 = ((pi * 2 * c1 * b) / 2 ) / 4 + ((pi * 2 * c2 * b ) / 2 ) / 4
-
I would say that is not AN ellipse, but two different half ellipses joined at the high point. So if you went the "higher math" route you would have the compute the areas ahead of and behind the high point.
If the forward portion of Charles' wing is a half ellipse and the rear portion is another half ellipse, the equation is still the same:
(root chord x span)/4 x pi
An ellipse is just a squashed out circle.
Keith
-
For our purposes, isn’t a rough guess close enough? Precision without wind tunnel data at correct Reynolds numbers is meaningless.
It is the guy at the handle and the one tuning the model that gets the trophy. Trust me, I have an MIT degree in Aeronutics, lousy coordination, slow reaction time and never got past an all time career high of one 500 point flight in competition. I treasure that score sheet.
By now, there isn’t much to be discovered in CL Aerobatic science. The pilots are the limiting factor and we need a new generation of ones with razor honed computer game skills to go farther. Sadly, they aren’t interested because model aircraft don’t have a reset button when you screw up. Plus, why spend a year building a model when you can buy a game?
-
For our purposes, isn’t a rough guess close enough?
Like most posts, 'our' purpose doesn't matter, it's the author's that counts and it's a valid question.