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Testing Stick-built Ribs
Hi Guys.
Does that title tickle any memory-bones? Well, let's see if I can tickle them again. First-off come the ground rules: The data came from "Handbook of Instruction for Airplane Designers, Structures Tests" Air Corps, U.S.Army (Not available to the public) ....and apparently not available to many Airplane Designers, too. :-) (Because nobody could remember seeing the thing.) Okay, start with the outline of whatever airfoil you're working with... which tells you right off that this isn't going to be good for ALL airfoils. The airfoil used in the Army manual looks suspicious like the USA-35B, which was used in the Piper Cub... and was the first thing C.G.Taylor tossed on the rubbish heap when he designed the Taylorcraft. However, the Army's test wing was tapered and of aluminum construction. It would be interesting to know the history of this manual since, from all appearances it didn't do the Army Air Corps much good. Using whatever outline you're using, starting at the trailing edge, come forward 10% of the airfoil's chord. The next section takes 43.8% of your airfoil's length. Next comes the main load-bearing section: 27.1% of your airfoil's chord, and finally the leading edge section -- 19.1% of the airfoil's chord. The weight is distributed as follows: 20% is suspended on the leading edge section, 40% is suspended on the mid-wing section, and 40% is suspended on the aft-wing section. You will note that NO LOAD is placed on the trailing edge of the wing. The method is a bit unusual (in my opinion) but it matches the |
#2
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Testing Stick-built Ribs
Veeduber wrote:
Hi Guys. Does that title tickle any memory-bones? Well, let's see if I can tickle them again. First-off come the ground rules: The data came from "Handbook of Instruction for Airplane Designers, Structures Tests" Air Corps, U.S.Army (Not available to the public) ...and apparently not available to many Airplane Designers, too. :-) (Because nobody could remember seeing the thing.) Okay, start with the outline of whatever airfoil you're working with... which tells you right off that this isn't going to be good for ALL airfoils. The airfoil used in the Army manual looks suspicious like the USA-35B, which was used in the Piper Cub... and was the first thing C.G.Taylor tossed on the rubbish heap when he designed the Taylorcraft. However, the Army's test wing was tapered and of aluminum construction. It would be interesting to know the history of this manual since, from all appearances it didn't do the Army Air Corps much good. Using whatever outline you're using, starting at the trailing edge, come forward 10% of the airfoil's chord. The next section takes 43.8% of your airfoil's length. Next comes the main load-bearing section: 27.1% of your airfoil's chord, and finally the leading edge section -- 19.1% of the airfoil's chord. The weight is distributed as follows: 20% is suspended on the leading edge section, 40% is suspended on the mid-wing section, and 40% is suspended on the aft-wing section. You will note that NO LOAD is placed on the trailing edge of the wing. The method is a bit unusual (in my opinion) but it matches the This is where your note stops. I expect you wanted to continue by asking for comments. Coupla thoughts: There's a freebee 2-D airfoil calculator from an MIT instructor which shows the shape of the low pressure on the upper surface, and the high pressure on the lower surface for a whole bunch of airfoils. If you cut these two shapes out of - lets say - lead sheet and weighed vertical strips from top and bottom, you would have a representative load for a particular airfoil station. But the last time I had that code was two or three computers ago.... So, getting down and dirty: Say a wing balances at 30% chord, then if you evenly loaded the front 30% with 70% of the load, and the back 70% with 30% of the load, you balance the turning moment (roughly!) Your USAAC cite puts roughly that proportion before and after the 30% point. So it seems to make sense. True, load distribution varies with AoA yada-yada..... Brian W |
#3
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Testing Stick-built Ribs
On Jul 25, 6:14*pm, Veeduber wrote:
Hi Guys. Does that title tickle any memory-bones? Well, let's see if I can tickle them again. *First-off come the ground rules: The data came from "Handbook of Instruction for Airplane Designers, Structures Tests" *Air Corps, U.S.Army (Not available to the public) ...and apparently not available to many Airplane Designers, too. *:-) (Because nobody could remember seeing the thing.) Okay, start with the outline of whatever airfoil you're working with... which tells you right off that this isn't going to be good for ALL airfoils. *The airfoil used in the Army manual looks suspicious like the USA-35B, which was used in the Piper Cub... and was the first thing C.G.Taylor tossed on the rubbish heap when he designed the Taylorcraft. *However, the Army's test wing was tapered and of aluminum construction. *It would be interesting to know the history of this manual since, from all appearances it didn't do the Army Air Corps much good. Using whatever outline you're using, starting at the trailing edge, come forward 10% of the airfoil's chord. *The next section takes 43.8% of your airfoil's length. *Next comes the main load-bearing section: 27.1% of your airfoil's chord, and finally the leading edge section -- 19.1% of the airfoil's chord. The weight is distributed as follows: 20% is suspended on the leading edge section, 40% is suspended on the mid-wing section, and 40% is suspended on the aft-wing section. *You will note that NO LOAD is placed on the trailing edge of the wing. The method is a bit unusual (in my opinion) but it matches the ....and right about there the whole damn shootin' match landed in my lap... that is, a lap-top HP 'Pavilion' computer flying home to roost on top of an outboard keyboard that allows me to type those long, complex words that some folks like to see in their articles and which if you try typing on an HP product you may as well throw it all out the door and plug in your S-100 computer and fire up its Hazeltine terminal because the chances are about 50-50. Hell, I throught it was World War Three when all it was happened to be a sixteen pound tom cat attempting to offer an example of his affections to a three and a half-pound lap-cat who knew I was the only feller she'd ever seen who put a 16 ga. shell into his cane every morning and wasn't ABOUT to take any lip from her boy friend. The moral of this tale is: There's really no limit to what's liable to come flying through your kitchen door if you're foolish enough to leave the damn thing open. -R.S.Hoover PS -- the truth is, I had no idea that a combination of feline romance and hi-tek electronics could actually end up SENDING a message when my best efforts often lead to failure. And that's the truth. |
#4
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Testing Stick-built Ribs
bob, that's as bad as the "dog ate my homework"!
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#5
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Testing Stick-built Ribs
On Jul 27, 4:33*am, wrote:
bob, that's as bad as the "dog ate my homework"! -------------------------------------------------------------------------- Gee, Great... that really hurts. But brings to mind a certain |
#6
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Testing Stick-built Ribs
Bob wrote:
On Jul 27, 4:33 am, wrote: bob, that's as bad as the "dog ate my homework"! -------------------------------------------------------------------------- Gee, Great... that really hurts. But brings to mind a certain Ya, we know you are faking it. But a great reply, all the same! :-) Brian W |
#7
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Testing Stick-built Ribs
On Jul 25, 7:01*pm, brian whatcott wrote:
Your USAAC cite puts roughly that proportion before and after the 30% point. |
#8
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Testing Stick-built Ribs
On Jul 27, 6:41*pm, brian whatcott wrote:
Ya, we know you are faking it. But a great reply, all the same! * :-) ------------------------------------------------------------------------------------------------------- Dear Brian, et al, It is the craziest thing but I'd swear the cats KNOW I am ill. Okay, okay... sure; the ol' hunting dog found dead on his master's grave, I'm talking about some VERY independent cats who now seem considerably less so; who jump in your lap when before you couldn't BRIBE them to come over and say hello. They have taken to accompaning me on my doctor-dictated hikes whereas before they gave such things less than a yawn's-worth of their Royal Attention. More than passing strange -- folk tales and all that -- it takes on a different emphasis. But... speaking of strange: On Sunday I had need to visit the local Lowe's, nearest of several Box Stores. Along the way there were TWO instances where slightly crazy drivers violated numerous traffic laws to inquire if I might be interested in selling my 'old bus' (a 1965 VW). One Crazy Driver, okay. After all, this is California... and it IS a splittie, etc. But two? That's about one too many. So... howzabout THIS to rattle your rudder-tab: After I shoot through (bound to happen, sooner or later, right?) So, after the Last Flight... the one we ALL gotta make sooner or later, this is to let you know I'll be keeping an eye on those rib-test procedures. (Just something to give all the girls something to twitter about... I''ll be watching :-) -Bob |
#9
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Testing Stick-built Ribs
On Tue, 28 Jul 2009 07:51:21 -0700 (PDT), Bob
wrote: On Jul 27, 6:41*pm, brian whatcott wrote: Ya, we know you are faking it. But a great reply, all the same! * :-) ------------------------------------------------------------------------------------------------------- Dear Brian, et al, It is the craziest thing but I'd swear the cats KNOW I am ill. Okay, okay... sure; the ol' hunting dog found dead on his master's grave, I'm talking about some VERY independent cats who now seem considerably less so; who jump in your lap when before you couldn't BRIBE them to come over and say hello. They have taken to accompaning me on my doctor-dictated hikes whereas before they gave such things less than a yawn's-worth of their Royal Attention. More than passing strange -- folk tales and all that -- it takes on a different emphasis. cats desert the dieing. have you ever thought that they've decided you arent going to just yet. it's a promising sign. et al. |
#10
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Testing Stick-built Ribs
In article ,
Stealth Pilot wrote: On Tue, 28 Jul 2009 07:51:21 -0700 (PDT), Bob wrote: On Jul 27, 6:41*pm, brian whatcott wrote: Ya, we know you are faking it. But a great reply, all the same! * :-) ---------------------------------------------------------------------------- --------------------------- Dear Brian, et al, It is the craziest thing but I'd swear the cats KNOW I am ill. Okay, okay... sure; the ol' hunting dog found dead on his master's grave, I'm talking about some VERY independent cats who now seem considerably less so; who jump in your lap when before you couldn't BRIBE them to come over and say hello. They have taken to accompaning me on my doctor-dictated hikes whereas before they gave such things less than a yawn's-worth of their Royal Attention. More than passing strange -- folk tales and all that -- it takes on a different emphasis. cats desert the dieing. have you ever thought that they've decided you arent going to just yet. That, and you're the one with opposable thumbs. Once they find a can opener that they can operate ... |
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