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Author Topic: rules in the dimensioning of aircrafts  (Read 1564 times)
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joeskies
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« on: December 18, 2017, 07:44:29 PM »

Undecided

what should be the length per wing (in cm) for an aircraft with a fuse length of 35cm?
rules in the dimensioning of aircrafts
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strat-o
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« Reply #1 on: December 18, 2017, 11:15:22 PM »

55 cm (full span).
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Mike Rolls
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« Reply #2 on: December 19, 2017, 01:17:16 AM »

Sorry, but there is no one answer to that. The wingspan and fuselage length of any given design do not have a fixed correlation. It depends entirely on what the designer intends to achieve. For example, my various C/L stunters over the years have shorter fuselage in relation to their wingspan than my R/C aerobatic models. If you look at F/F contest designs you will see differing solutions - for example a modern F1A glider had - overall - a longer fuselage and smaller tailplane than its predecessors of years ago. And so on
Mike
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Terry Fitzpatrick
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« Reply #3 on: December 19, 2017, 04:23:42 PM »

There is no direct  link between wing span and fuselage length, but there is a book that gives general proportions for lengths and areas of model aircraft in 17 different categories. The book is ancient (1955) but it will give you the information you require. You can download a free copy from rclibrary.co.uk  . The book details are "Design for Aeromodellers" by Ron Warring, the publisher was Model Aeronautical Press. Enjoy the book Joe.
regards Terry Fitzpatrick AUSTRALIA
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Mike Rolls
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« Reply #4 on: December 20, 2017, 12:23:46 AM »

There is no direct  link between wing span and fuselage length, but there is a book that gives general proportions for lengths and areas of model aircraft in 17 different categories. The book is ancient (1955) but it will give you the information you require. You can download a free copy from rclibrary.co.uk  . The book details are "Design for Aeromodellers" by Ron Warring, the publisher was Model Aeronautical Press. Enjoy the book Joe.
regards Terry Fitzpatrick AUSTRALIA
Good Lord! I didn't realise that was still available - it was a series of articles in either Aeromodeller or Model Aircraft - I forget which - that I read avidly at the time. Ron was one of the leading lights of British aeromodelling at the time, with a wealth of knowledge on just about every aspect of model aircraft. Bear in mind how old this advice is - it obviously doesn't apply to some modern competition classes - but for general use it remains good stuff
Mike
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joeskies
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« Reply #5 on: December 20, 2017, 06:19:40 PM »

but i'm worried? cuz m a newbie.
 some say the fuse length should be 70 o/o  of the wing span.
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Mike Rolls
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« Reply #6 on: December 21, 2017, 01:26:31 AM »

Sorry, but as I have already posted there is no ‘magic number’ that for a wingspan of X then the fuselage length should be Y. The length of the fuselage for a given design depends on what the design is intended to achieved and the weight and location of various elements – notably the power source. For example, an IC (glow, diesel or petrol) model has a significant proportion of the model’s weight concentrated in a small area, usually at the extreme nose. An electric powered model has, comparatively speaking, a significant element of the model’s weight in the flight battery, but in many cases this can be so located as not to affect the overall length of the nose of the model – i.e. under (or over in the case of a low wing deign) the wing. A rubber powered model’s motive power is long and thin, with its weight strung out along  much of the length of the fuselage.
It would be helpful if we knew just what type of model you are contemplating – from your query I assume that you are looking to design something yourself? If that is the case, and you don’t wish to build an established design, I would very strongly advocate that you look up an existing design that resembles what you want to build and simply lift the numbers that it uses. Plagiarism, in this context, is greatly to be encouraged!
Hope that helps
Mike
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lincoln
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« Reply #7 on: December 21, 2017, 08:50:54 AM »

Some of the answers here:
http://www.eaa62.org/technotes/tail.htm

Answering this question is actually a very complicated task requiring a lot of information about the model and the intended task.

-Wing chord and area will be a large part of determining how big and or how far back the horizontal stab should be. That, and how much it takes to deal with pitch changes from flaps or other gadgets. I'm sure there are other factors I'm not considering.

-Vertical stab size and how far back to put it will be determined, in part, by desired damping in yaw, radius of gyration of the wing, area and span of the wing, whether thrust is always on the centerline or sometiems off center as with a twin, whether you use a rate gyro to control yaw, etc. I know the rate gyro sound nuts, but they're really cheap now. I used one several years ago to fix the handling on a model I had.

-Balance considerations as mentioned in other posts.

-Aesthetics. You'll probably enjoy the model more if you like the way it looks.

The less you need to completely optimize your design, the less critical it is to get everything exactly right, and there's usually a bit of slack available. Looking at successful designs that already exist can be helpful. If you know just what you're trying to accomplish with your new design, that will probably help with these decisions.
 
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joeskies
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« Reply #8 on: March 11, 2018, 02:37:55 PM »

Huh
 How about finding the wing loading and its correlation to the thrust-to-weight ratio?
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Mike Rolls
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« Reply #9 on: March 11, 2018, 04:20:24 PM »

Sorry, but again there isn't a straight forward correlation between wing loading and T/W. Two models with the same wing loading can have have very different T/W figures. An example. Back in the day I built a series of small F/F power duration models. They happened to be the same size and weight as the then very popular Wakefield (now known as F1B) rubber duration models - some 8 ounces AUW and a wing area of around 200 sq. ins. P/W figures were very different however. My 09 diesels turning 8x4 props at 10,000 gave some 18 ounces of static thrust - a P/W better than 2:1. As you can imagine,, they were trimmed for true vertical climb. A Wakefield would turn an 18x32 prop at more like 1,000 or around 5-6 ounces of static thrust - perhaps a bit more during the initial burst - but the two models had the same wing loading.
Mike
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joeskies
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« Reply #10 on: March 27, 2018, 05:18:22 AM »

so far i've gone this far...
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joeskies
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« Reply #11 on: March 27, 2018, 05:21:36 AM »

and this
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