Wing Area Calculations

Wing Area Calculations
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Wing Area Calculations - 7/13/2003 8:09:07 PM

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Several months ago I asked in this forum about wing areas and got an answer. Many of them. I am now having some doubt if the majority of respondees were not correct.

I have been working on parts for several Wakefield rubber powered A/C designed in the 1930's these past months. In the article is always a stated wing area. When I check wing area upon doing a re-draft, I have been consistantly getting larger area figures. This is all based on using the data as stated here back a few months ago.

In doing yet more area checking, I find that if you subtract out the wing area through the fuselage, it comes more into alignment with what was stated in the original magazine article.

Does anyone know if there was written difference as to area calculation between the 1930's and now? The Wakefield rules used to be pretty tight, and if I subtract out that 15 to 20 square inches involved in the fuselage, the numbers seem more reasonable.

So we now know how wing area is calculated today. We calculate the whole wing, projecting it through the fuselage.

However, in the 1930's did they subtract out fuselage area or not?

Wm.

Wing Area Calculations - 7/13/2003 10:15:52 PM

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I'm not sure about in the 1930's, but current wakefield rules state that the wing (actually combined surface) area is calculated as the projected wing area, as opposed to plan-view. Maybe this is contributing to what you're seeing? Plan-view area will always be larger than projected area (which takes dihedral into account).

-David

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Wing Area Calculations - 7/15/2003 4:42:58 AM

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Most wing area calculations are done without the fuselage area. Some manufactures will add the fuselage area to make their wing area larger. While the fuselage will provide some lift, I would recommend that you concentrate on the wing area only and calculate fuselage area if you need to make sure that your drawings are correct to others that add fuselage area to the wing area calcualtion.

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Wing Area Calculations - 7/15/2003 5:55:11 AM

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Wing area calculations for wing loadings etc always include the area inside the fuselage.
Projected area is the criteria.

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Wing Area Calculations - 7/15/2003 7:34:26 AM

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Tall Paul is correct to say that wing loading calculations use the planform, i.e. top-down(including within the fuselage) wing area for an airplane. Reason being is that the fuselage also contributes to lift. The only time one would use the "exposed" wing area is when engineers do calculations to predict skin friction contributions to overall drag estimations. This "exposed" area is also known as the "wetted area" of the wing, FYI... Hope this helps clarify

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Wing Area Calculations - 7/17/2003 6:40:07 PM

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NOPE

Tall Paul is incorrect

Current AMA rules for free flight (See #6) and descriptions indicate that only the lifting surfaces apply. It specifically excludes out areas involved by fuselage or stick fuselage. If the wing has a high dihedral angle, natually the area gets a bit smaller.

The old fellows used to get within a couple square inches of maximum. If the fuselage area was added in to the total area, the calculated wing area would often times be about 15-20 Sq. inches larger.

Go to AMA and visit the free flight rules section. Wakefield is an international event, and is such noted.

Wm.

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Wing Area Calculations - 7/17/2003 8:15:51 PM

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He may be incorrect with regard to some model free flight competition's rules, but when it comes to REAL ENGINEERING work, he IS CORRECT.

Just because a rule in some freeflight competition says that wing area is calculated by the "exposed" wing area, doesn't mean that the Aeronautical and Aerospace Engineers of the World do it that way. I promise you that everybody from Cessna to Boeing, and everybody at NASA does include the wing area inside the fuselage.

I only stress this point because I thought the same way, until I took up Aerospace Engineering, and my professor told me otherwise.

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Wing Area Calculations - 7/17/2003 9:38:51 PM

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Wm
Until 1951 the Wakefield rules allowed for differing interpretations of wing area. They measured the amount of wing 'in the breeze' and also the planned area, not the projected area. Wing area was to between 190 and 210 sq. ins.
Thus, if you had a 200 sq.in. wing - say 40x5 - mounted on a parasol or strapped to the top of the fus - that was seen as 200 sq,ins. If, on the other hand, you had a plug in wing and lets say that the fus was 2" wide, you could have a 42"x5" wing and it still was counted as 200 sq.ins.
From post WW2 until 1951 the tailplane had to be not more than 33% (NOT 1/3) of the wing and was measured in the same way. That rule was introduced prior to WW2 - before you could have as large a tail as you wished - but I don't have access to my references for the next few months so am uncertain from memory as the the date - but it was in the 30s.
In 1951 the rules were 'metricated' - and the total of wing and tail with no limit on tail size and projected areas measured, and if you had some of your wing 'in the fus' - tough - it still counted.
Thus 8 ounces became 230 grammes, and 190-210 sq. in wing and 33% max tail became 17-19 sq. dms of projected area for wing and tail combined.

Hope this helps

Mike

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Wing Area Calculations - 7/17/2003 9:42:41 PM

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Wm

Forgot to say that prior to 1951 the fus cross-section had to be not less than

(Total length of rigged model in inches ) squared/100 square inches.
From 1951 on the cross-secrtion had to be not less than 65 sq.cms regardless of fus length. The cross-section requirement was dropped some years later, but again without my references can't remember when

Mike

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Wing Area Calculations - 7/17/2003 10:03:49 PM

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There are any number of local situations where general rules have been modified/inbred to suit peculiar conditions.

Depends on the interest of the rules users how the rules get bent.
but..
In engineering, bending rules results in death, so what works is used, unless there is a very compelling reason to ignore what works.
As nighthawk17 says.... real airplanes do it tip-to-tip, including what's inside the fuselage.
And in toy airplanes, so does FAI.

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Wing Area Calculations - 7/17/2003 10:25:58 PM

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WM,
You were asking about Wakefield rules. AMA general FF rules do not apply to Wakefield, as Wake (F1B) is not an AMA-regulated event. F1B is AMA event 151, but the AMA rules specifically state that all FAI regulations for the aircraft themselves apply. AMA contest directors are allowed to schedule the contest rounds differently, but this has nothing to do with the model.

As already stated, the FAI rules specify the maximum (and generally minimum) combined surface area as being the orthogonal projection onto a plane at zero incidence, and including any area passing through a fuselage, etc. "So as to meet at the plane of symmetry of the model." page 45, 1.4.1 FAI sporting code, section 4, volume ABR.

-David

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Wing Area Calculations - 7/18/2003 2:25:46 AM

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WM,
As you know, Wakefield rules have evolved over the years. The methods of measurement have also changed, as mentioned by Mike. Here is a nice history of the Wakefield Cup, from 1911 to the present.

http://www.btinternet.com/~kaynes/Wakebook/wkbkhome.htm

Interesting highlights:
"Prior to the end of the 1933 flying season the SMAE did some serious fiddling with the Wakefield Cup Rules. First they deleted the "Any Type of Power Rule", restricting power to "Rubber Power Only", then they restricted the wing area to be between "190 & 200 sq. inches", then they placed a limit on total weight including rubber motors to be "4 Ounces Minimum", and finally they made the flight time to be the "Average of Three Flights". So much for the threat of petrol powered, and outdoor-indoor aeromodels!"

"1956... This contest marked the end of the "Traditional Wakefield Era", long live the "Modern Era"! At last "they" had done away with that (quoting Bill Dean) "....stupid obsolete rule..." This was the last contest that required the "Rise Off Ground" (ROG) launch. Now Comrades: "you may never go home again!" "

Anyway, if you are building replica models and people want to know what area they have, simply ask them to specify a set of measurement criteria.

have fun,
-David

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Wing Area Calculations - 7/19/2003 6:57:31 PM

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David

Many thanks for that link on the Wakefield - long my 'hero' model when I was a lad. There is, however, a definite mistake in the wing area quoted as 190-200 sq.ins. The actual rule at 1950 stated 200 sq.ins plus or minus 10 sq.ins - in other words the 190-210 I quoted. Tghat was the rule for all the pre-51 8 ounce models and as far as I know it was the first area rule and applied ot the 4 oz designs as well.

Mike

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Wing Area Calculations - 7/19/2003 7:12:01 PM

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David
Just looked at that rules summary more carefully and there are a number of errors in it:

Tatal area from 1951 on should read 17 sq. dms minimum to 19 sq. dms maximum.
The weights are all to hell - from 1951 on the MINIMUM aUW was 230 grammes including rubber (about 8 1/7 ozs) NOT 8 ouces as quoted - and the weight column is erroneously headed MAXIMUM weight (perhaps accurate fro the 11 lb figure for pre 1934!)
Once limited rubber was introduced the rule was that the rubber PLUS the airframe had to weigh at least 230 grammes - as written by Rushinig you would assume that you had to have a model UNDER what was actually the minimum!
Also - if you realised he was in error in quoting the airframe weight as a maximum and that it should be a minimum - you could still end up disqulaified - if you built (under the 2002 rules for the sake of argument) an airframe of exactly the 200g he quotes and then, to be on the afe side made up a motor ot (say) 28g to make sure of being under the max limit - your model would only weigh 228g - instant disqualification!
From 1951 on until the rule was scrapped the minimum cross-section, as I wrote above, was 65 sq. cms - NOT 10 sq.ins - although to be fair the two are VERY close (but 65 sq. cms is fractioanlly bigger)
Most folk with any experienceof the Wake over the years will spot these errors - but a well meaning modeller deciding to have a go at a Wake, whether modern or old time, could be bitterly disappointed if he turned up at a contest with a model meeting Rushing's figures.

.
Mike

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Wing Area Calculations - 7/19/2003 11:18:50 PM

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Hey Mike,
Thanks for making those points. I was unaware of any errors in that publication. I saw my first Wake in around 1984, so about the only rule changes I've seen are increasing the minimum airframe weight and decreasing the max allowed rubber. Oh, and the banning of motor heaters.

thanks,
-David

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Wing Area Calculations - 7/20/2003 1:59:15 AM

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so about the only rule changes I've seen are increasing the minimum airframe weight and decreasing the max allowed rubber. <<

David,
Tell me about it! Back in 53 I was just completing my latest world-beater (

). I had managed to get the airframe down to 2.75 ounces and was scrabbling through the piggy bank to afford enough rubber for 5.3 oz motors when my flying buddy arrived with the news that for 1954 rubber was to be limited to 80 grammes!!!!

Never did fly the thing - my heart just wasn't in it!

Mike

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