From what I read here on a post (no idea where it is) you can scale down an aircraft dimensions but not its performance, a 7/8ths scale model of a Spitfire even if a 7/8th scale Merlin was available is a completely different beast, you must also scale aerofoils and stuff which means they are not the same.
Factors of Scale
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- #22
Actually rule of thumb is a figure of speech which means generalized rules.
The term actually came from an era where it was permissible for a man to whip his wife: Basically it was acceptable to use a whip the thickness of one's thumb.
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- #23
Mostly my interests was size to weight for the same g-load
What does that mean? A slightly scaled down spitfire will have the span of a clipped wing spitfire, if you scale down to model size you can have a rate of roll that would kill any pilot. Things don't scale, an ant maybe able to lift a comparative equivalent of a grand piano in its jaws, but a human size ant wouldn't even be able to breathe let alone lift pianos.
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- #25
For example, if I was to take a basic shape, say an XB-42 and scale it down, or scale up a P-47N by 50% what would the weight increase by?
Likewise if I was to take an existent plane and increase it's g-load from 4.5 ultimate to 6, how much weight as a rule would go up?
You cant do that. Scale up a P-47 by 50% the piston bore and stroke too? The cockpit so that the pilot cannot reach the controls. You have 50% bigger spaces between strengthening structures, so it is weaker when it needs to be stronger. When you talk about G loads and weights I honestly don't know what you are asking.
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- #27
No, I was talking about the basic fuselage shape
It would look like a hell cat with a wildcat engine on it, what engine would you put in it?
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Shortround6
Major General
It is the heaviest. it is just a tad skinner than a R-3350.
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- #31
This might be a bit more productive...
To anybody here: If I presented an image of a design, real or fictitious, made either by me or somebody else (with credit afforded them) asked you to give me a weight estimate if I gave you a g-loading figure...
Could you reliably guess how much it'd weigh +/- either 2000, 1000, 500 pounds
To anybody here: If I presented an image of a design, real or fictitious, made either by me or somebody else (with credit afforded them) asked you to give me a weight estimate if I gave you a g-loading figure...
Could you reliably guess how much it'd weigh +/- either 2000, 1000, 500 pounds
No.
Shortround6
Major General
Amazon 65 bucks.
There are reasons that people got to school for 4 years just to get started in the field of aircraft structures.
I didn't need to. My uncle was the custodian of a Norman castle. to make a span you can use a stone beam, to make a longer span you can use a semi-circular arch, a bigger span needs a vaulted arch. All the beautiful structures you see in European Cathedrals were about as good as it got at the time, you cannot double any of them in size, the people that tried going a bit bigger without changing the science had a collapse and there were many of them.
GregP
Major
I have never seen a plane with stone beams. And 0.40 granite might hard to rivet. 
Thou art a cad. As you well know if you double the size of something what does that mean? Rivets twice the distance apart? A propeller twice the diameter, don't they go supersonic at the tips or something? From a young age we know these things in our real lives , I don't know how it is considered seriously on an adult forum.I have never seen a plane with stone beams. And 0.40 granite might hard to rivet.
GregP
Major
Scaling really isn't silly though. In radio control aircraft, I used to fly airplanes with about a 60 - 65 inch wingspan. When I went up to a 108-inch wingspan version of one of them, it flew MUCH better than the 60-inch one did. And it built up with about the same type construction, just more of it, with almost the same parts count. So, at least up to a certain size, you can do it with models. The 60-inch planes were about 5 - 7 lbs and the 108-inch unit was about 9.5 lbs. No cube rule there for weight.
Once you get to manned aircraft, it's tough to do a simple scale-up. You'd THINK the easiest might be the Cessna line.
But ... and here's one not many people realize, a C-172, C-182, and C-210 all have a wingspan of within 1 inch of one another and a length of within 1 inch of one another. But a C-172 had a max weight of around 2550 lbs, a C-182 around 3100 lbs, and a C-210 around 4000 lbs, give or take a few lbs for different model years. These planes LOOK very close to one another and are all about the same size and have max weights almost 60% apart.
So, I don't buy into any cube rules for weight with scale when aircraft of the SAME size vary almost 60% from the same manufacturer and same passenger capacity.
I still think .040 granite would be hard to rivet and maybe somewhat brittle. Cheers from the CAD.
Once you get to manned aircraft, it's tough to do a simple scale-up. You'd THINK the easiest might be the Cessna line.
But ... and here's one not many people realize, a C-172, C-182, and C-210 all have a wingspan of within 1 inch of one another and a length of within 1 inch of one another. But a C-172 had a max weight of around 2550 lbs, a C-182 around 3100 lbs, and a C-210 around 4000 lbs, give or take a few lbs for different model years. These planes LOOK very close to one another and are all about the same size and have max weights almost 60% apart.
So, I don't buy into any cube rules for weight with scale when aircraft of the SAME size vary almost 60% from the same manufacturer and same passenger capacity.
I still think .040 granite would be hard to rivet and maybe somewhat brittle. Cheers from the CAD.
Shortround6
Major General
Scaling really isn't silly though. In radio control aircraft, I used to fly airplanes with about a 60 - 65 inch wingspan. When I went up to a 108-inch wingspan version of one of them, it flew MUCH better than the 60-inch one did. And it built up with about the same type construction, just more of it, with almost the same parts count. So, at least up to a certain size, you can do it with models. The 60-inch planes were about 5 - 7 lbs and the 108-inch unit was about 9.5 lbs. No cube rule there for weight.
Once you get to manned aircraft, it's tough to do a simple scale-up. You'd THINK the easiest might be the Cessna line.
But ... and here's one not many people realize, a C-172, C-182, and C-210 all have a wingspan of within 1 inch of one another and a length of within 1 inch of one another. But a C-172 had a max weight of around 2550 lbs, a C-182 around 3100 lbs, and a C-210 around 4000 lbs, give or take a few lbs for different model years. These planes LOOK very close to one another and are all about the same size and have max weights almost 60% apart.
So, I don't buy into any cube rules for weight with scale when aircraft of the SAME size vary almost 60% from the same manufacturer and same passenger capacity.
I still think .040 granite would be hard to rivet and maybe somewhat brittle. Cheers from the CAD.
yeah, but can you take the wing off a 172 and stick it on a 210 and live to tell about it
Or if you stick the wing of a 210 on a 172 how much of your payload do you give up to stay within gross weight?
OK I know the mounts/bolt holes probably won't line up but you get the idea, same size but different loads calls for different construction.
Sort of on the idea of scaling, my father told me as a teenager that if you could find a hypothetical cliff high enough and dangled wires over the edge they would break at the same length depending on material, not the size of the wire. brass (if certain alloy) would break at a certain length and steel (certain alloy) would break at another length. This is regardless of whether it was 1/8 in or 1/2 in or 1 in in diameter.
(you do need a mighty high hypothetical cliff)
All of the control line models I flew were way, way overbuilt.
If you crashed a real aircraft the way I did those CL aircraft you'd have a pile of trash and dead people.
As it was I'd usually just straighten up the landing gear, reattach the wings and go back to flying.
If you built a real aircraft that way, it'd never get off the ground.
If you crashed a real aircraft the way I did those CL aircraft you'd have a pile of trash and dead people.
As it was I'd usually just straighten up the landing gear, reattach the wings and go back to flying.
If you built a real aircraft that way, it'd never get off the ground.
GregP
Major
Wasn't suggesting swapping wings, Shortround. I was saying the cube rule for weight with scaling doesn't work when you have three or four planes all the same size with weight that varies by 60%. But I bet you knew I was saying that. Personally, my favorite is the C-182 of that group. An all-round great flying airplane with good load-hauling capability and friendly flying characteristics.
About the wires ... you don't actually need the cliff. You could use a deep trench in the ocean. And he was right. They have to use synthetic lines for deep lines that have the same weight as the seawater instead of chains or the chains break under their own cumulative weight. But, I'm sure you are up on that. It's tough to be as up on aircraft and engine technical aspects as you are and not have it bleed over into other areas of engineering.
People don't think about it much, but a fast attack class submarine is basically a long, low aspect ratio airplane ... sort of like an F-104, flying in very thick air (water) with wings scaled to match the medium and the fact that they do not carry the weight as much as supply maneuvering power.. I have heard they can pull 4 gs underwater. The diving planes, especially the conning tower sails, are basically undersized airfoils. Sort of off-topic, but I don't intend for it to develop into a submarine discussion in here, hopefully. Some of the many-bladed turboprop propellers, like the C-130J, resemble long, skinny, submarine props, with scimitar tips.
Cheers.
About the wires ... you don't actually need the cliff. You could use a deep trench in the ocean. And he was right. They have to use synthetic lines for deep lines that have the same weight as the seawater instead of chains or the chains break under their own cumulative weight. But, I'm sure you are up on that. It's tough to be as up on aircraft and engine technical aspects as you are and not have it bleed over into other areas of engineering.
People don't think about it much, but a fast attack class submarine is basically a long, low aspect ratio airplane ... sort of like an F-104, flying in very thick air (water) with wings scaled to match the medium and the fact that they do not carry the weight as much as supply maneuvering power.. I have heard they can pull 4 gs underwater. The diving planes, especially the conning tower sails, are basically undersized airfoils. Sort of off-topic, but I don't intend for it to develop into a submarine discussion in here, hopefully. Some of the many-bladed turboprop propellers, like the C-130J, resemble long, skinny, submarine props, with scimitar tips.
Cheers.
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