Wing Area & Wing Load

svaughn · Post by **svaughn** » Mon Feb 23, 2009 8:02 am

Hi thymekiller,

I just outlined the wing as you see it on the guillow plans and had sketchup calcualate the sqft of the enclosed area. Sketchup is cool because it lets you use curves to trace the rounded edges (like the wing tips).

I never thought about the top and bottom surfaces as separate factors in the equation.

ranarc · Post by **ranarc** » Mon Feb 23, 2009 9:36 am

Hi Steve,

First, please call me Rana. This request is for all in this forum. This is the first forum I have ever subscribed to, hence the full name as the sign in:-) Didn't know better.

The calculation was for the 504-Spitfire. The one supercruiser manually calculated. He gave me the best tip ever. How to cut notches, so I read everything he writes very carefully! supercruiser, thymekiller and kittyfritters are the other guys who encourage beginners like me. Xanadu and BillParker set the targets of building excellence. Maybe some day ....

To get area in Visio ... Tools --> Add-ons --> Visio Extras --> Shape Area and Perimeter. You need a closed shape to use this. Visio is real cool with tracing. With a bit of practise, tracing complex stuff is easy.

Steve, I am not an experienced builder / flyer. Absolute novice. I am yet to complete my first build. The 504- Spit.

Regards, Rana

svaughn · Post by **svaughn** » Mon Feb 23, 2009 11:24 am

Hi Rana,

Thanks for the tip on Visio. It works great. I've been playing with Sketchup for a while, but I am much more familiar with Visio.

I just started building again after about 35 years. I've only finished two kits: a Dumas PT16 and a Guillow P-51 (905). Neither one is very impressive, but I am working to improve my skills.

I hope to finish the 500 series FW-190 soon.

supercruiser · Post by **supercruiser** » Mon Feb 23, 2009 6:14 pm

svaughn wrote:Hi Supercruiser,

Looking for lift on the area under the fuselage on a low wing airplane is counter intuitive to me since most of the lift is generated by the shap eof the upper suface of an airfoil and the fuselage of a focke wulf doesn't resememble and airfoil to me.

What would you recommend for mid wing planes like the Hellcat or Wildcat?

I can understand including the entire wing structure in the calcualtion on the high wing models though.

Steve

Even with a blunt nose fuselage, lift still occurs over the middle of the wing. The lift distribution along the entire span maybe not as good for a Focke-Wulf as a Spitfire. However, I am thinking just to be consistent, the wing/fuselage area intersection should be included. Far as I know, that is how most models and full-size aircraft are measured.

That way when we are comparing our models, and someone says, mine is .65 gms/sq.in. and another says, mine is .68 g/si, then we can be sure of making like comparisions. Perhaps, you could find an accurate scale drawing of a full size airplane with the manufacturers published wing area and using your program see if they are counting the fuselage/wing area as part of the total wing area.

thymekiller · Post by **thymekiller** » Mon Feb 23, 2009 7:54 pm

I dont know ANYTHING about lifting surface inside a fuse.
I do know that the underside of a wing does have an effect on lift. Semifoiled', flat, or underchambered, there IS a response to the shape of the bottom of the wing. Just how much is for smarter people than me to debate. In the case of a sheet wing [ no top or bottom foil' at all ] Most of the lift for the model actually comes from the bottom of the wing "skimming " over the air. [ Like a fast boat over water.]
This is why when figureing wing area, it is best to figure the full width of the wing on high or low wing craft. [ In the case of model airplanes ]
Also, the fact that it is a small model changes alot of things, like the air over/around a wing tip, ect.
The system is not perfect, but it does give us a basic guideline to follow. I have read this same type of disscussion on MANY parts of the web and there is no clear answer. Its a matter of personal taste, really. There are good reasons to include wing tips and good reasons not to. I do because it makes the math easyer, and good or bad, they all have wingtips.
But thats just me. Your mileage may vary.

thymekiller

ranarc · Post by **ranarc** » Tue Feb 24, 2009 1:47 am

I have a scale drawing of the Supermarine Spitfire. Scale is Half inch = One foot. The spec specifies a wing area of 242 sqft. Did the Visio operation. Without the area under the fuselage the wing area is 111 x 2 = 220 sqft. 22 sqft under the fuselage! So a total 242 sqft includes the area under the fuselage.

I was a bit surprised by the accuracy of the results I got

Regards, Rana [/code]

svaughn · Post by **svaughn** » Tue Feb 24, 2009 7:42 am

It would be very useful to have a table of target weights for each Guillow's model .That would allow builders that want to fly their models to create a weight budget before they get started and have some assurance that their finished model would fly.

I recalculated the wing area on the plans I have to include the wing area under the fuselage and I come up with this table:

Code: Select all

model            wing area            target weight
                    sqin	      .5gm/sqin   .7gm /sqin
502 fw190           44.9            22.5        31.4
505 bf109           41.5            20.8        29.1
905 p-51            49.3            24.7        34.5
ww-1 albatros       82.3            41.2        57.6
ww-5 se5a          111.9            56.0        78.3
ww-7 britol bullet 109.3            54.7        76.5
ww-9 folker d8      49.8            24.9        34.9

thymekiller · Post by **thymekiller** » Tue Feb 24, 2009 8:39 am

svaughn has a good idea. Perhaps we could add rubber size recommenditions. Quite often a person has to chose between weight and strengh [ or details ] and knowing how close you are to target weight would be a handy piece of infomation.

thymekiller

thymekiller · Post by **thymekiller** » Tue Feb 24, 2009 9:18 am

I just figured my 500 series warhawk and came up with 51.73 square inches. Does that sound right?
Without rubber, she weighs 23 grams. [ 22.99]
I think this gives a wing load of .44 grams per inch.
Current motor weighs about 1.5 grams, but will experiment with that .

thymekiller

supercruiser · Post by **supercruiser** » Tue Feb 24, 2009 9:54 am

I build 3 foot models.

From 3 feet away they look o.k.

supercruiser · Post by **supercruiser** » Tue Feb 24, 2009 10:09 am

OOPS! My previous post was for a different thread.

Steve,
Nice graph. I need to print that.

supercruiser · Post by **supercruiser** » Tue Mar 01, 2011 9:22 pm