[split thread] increasing Vne on the CH 640

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pictsidhe

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Unfortunately, the economics of the complex forming operations required to make an airplane worth having are such that when you add up the hours required to create the tooling and then create the parts in the RV-10 for a one-off, the economic payoff is way down below minimum wage. So the kit is pretty much the most economical and effective way to build the RV-10.
My own project is the same way. The various tooling to make it is the slow part. Once that is made, parts could be churned out quickly and affordably.
 

pictsidhe

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You can also do ground tests of the structure with an eccentric weight and a small motor. Thurston mentions this in one of his books (I don't remember which one).
I'm thinking of replacing a piston in my engine with a small motor with an eccentric to do a stationary TV test. It makes testing much simpler
 

Turd Ferguson

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Unfortunately, the economics of the complex forming operations required to make an airplane worth having are such that when you add up the hours required to create the tooling and then create the parts in the RV-10 for a one-off, the economic payoff is way down below minimum wage. So the kit is pretty much the most economical and effective way to build the RV-10.
I believe it was Van that said one time the difference between the raw aluminum and stamping on a part like a wing rib is only pennies.
 

SVSUSteve

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I'm thinking of replacing a piston in my engine with a small motor with an eccentric to do a stationary TV test. It makes testing much simpler
Come again? I am having trouble picturing what you mean? Do you mean actually placing something that is going to rattle about in the cylinder?

I planned on asking for advice on here regarding how to do it properly. I figure that the "normal" way is pretty straightforward (so far as I can tell...haven't done much investigation) and I am more concerned about oversimplifying something and introducing oversight.
 

SVSUSteve

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My own project is the same way. The various tooling to make it is the slow part. Once that is made, parts could be churned out quickly and affordably.
I have to build a male mold for parts of the fuselage to form the plywood. That's going to be fun. *eyeroll* LOL
 

pictsidhe

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Come again? I am having trouble picturing what you mean? Do you mean actually placing something that is going to rattle about in the cylinder?

I planned on asking for advice on here regarding how to do it properly. I figure that the "normal" way is pretty straightforward (so far as I can tell...haven't done much investigation) and I am more concerned about oversimplifying something and introducing oversight.
A small electric motor with an eccentric on the end will be linked via an extra long 'conrod' to the crank. I can then vibrate the crank a set angle at an electrically controlled speed. I want to make it sturdy enough so I can simulate a constant torque at the prop, which will be a weight on a bungee hung off a blade. Instrumentation gets a whole lot easier. I can also 'run' it indoors without having to worry about it killing me.
 

SVSUSteve

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A small electric motor with an eccentric on the end will be linked via an extra long 'conrod' to the crank. I can then vibrate the crank a set angle at an electrically controlled speed. I want to make it sturdy enough so I can simulate a constant torque at the prop, which will be a weight on a bungee hung off a blade. Instrumentation gets a whole lot easier. I can also 'run' it indoors without having to worry about it killing me.
I don't know enough about engines to know whether that's a good idea or not.
 

Mad MAC

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Generally for part 23, One would use all three methods, Numerical, ground test followed by flight test. Locally there was many years ago a flight test where the pilot come too, upside down with the aircraft flying relatively stably missing the outer wing panels and tail. The cause was poor weld detail / poor weld on a mass balance weight which unfortunately demonstrates the point that your flutter margins are only as good as the structure is durible.
 

BoKu

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I believe it was Van that said one time the difference between the raw aluminum and stamping on a part like a wing rib is only pennies.
[Warning: This is heading pretty far OT...]

Just so. As long as you have the stamping dies, the stamping press, a trained press operator, power infrastructure to run the press, and a building to keep the press in. Oh, and you're also doing batches of hundreds or thousands of the exact same rib. That puts you on the point of the curve where ribs are near enough free as makes no difference. This is the whole specialization of labor, interchangable parts, and economies of scale that brought us the industrial revolution, and other revolutions regarding means of production.

At the other end of the curve (and I've BTDT and worn the bloody T-shirt), making one-off aluminum ribs from plywood patterns probably takes the lone artisan at least two days per rib when you factor in all the fiddly work.
 

SVSUSteve

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...the other end of the curve (and I've BTDT and worn the bloody T-shirt), making one-off aluminum ribs from plywood patterns probably takes the lone artisan at least two days per rib when you factor in all the fiddly work.
And THAT (see bolded portion above) is one reason why I chose to make wooden ribs. ;)
 

BBerson

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I think Bushby reported about 30 minutes to make a hand formed sheetmetal rib. (just reading EAA archives a few days ago.)
 

BBerson

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Starting where?
Well, it might take an hour to bandsaw the plywood forms. A few minutes to draw the rib blank on the sheet and shear it by hand. Then form it might take a 15 minutes and another 5 minutes to flute it straight. It all depends on if a nose rib or main rib, etc. Or with lightening holes.
 

BoKu

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Well, it might take an hour to bandsaw the plywood forms. A few minutes to draw the rib blank on the sheet and shear it by hand. Then form it might take a 15 minutes and another 5 minutes to flute it straight. It all depends on if a nose rib or main rib, etc. Or with lightening holes.
When it comes to the precision required for a thick-skinned 200 MPH airplane (that's what we're talking about here), it probably goes that fast by the time you get to your 10th or 20th rib. First-timers, maybe not so much.
 

BBerson

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Well, it takes some time to learn any new skill and some practice on scrap is good. But the 10th rib should be almost identical to the first, within the usual tolerance.
 

wsimpso1

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IF.... IF you wanted to increase the Vne on the CH 640 by Zenith, how would you do it?
Folks have already answered this one. It will take checking the whole thing for flutter to the new speed, checking all surfaces and structures for being able to stand the higher dynamic pressure, the higher drag and moments, if the airplane can even reach the new speed, and on and on. Basically you would start over again unless you had the tech data on the whole airframe to begin with. Then you might already know what the limits are for the original airframe, which makes it a little easier...

What aspects are different between the two that would result in such a large difference?
I doubt anyone on here knows. Here is why. Neither the folks at Van's or Zenith are likely to tell anyone what the limiting factors are for their airplanes from analysis and/or from ground testing. And you can bet that when they dived to Vdive and reduced the number 10% to give us a Vne, they breathed a sigh of relief and said they were never going that fast in the thing again.

Understand that there are many things that can set Vdive, and the one at slowest speed sets it. The story is the Stearman's is set by the speed the airplane can make going straight down with the power full power.

Billski
 

geosnooker2000

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Unfortunately, the economics of the complex forming operations required to make an airplane worth having are such that when you add up the hours required to create the tooling and then create the parts in the RV-10 for a one-off, the economic payoff is way down below minimum wage. So the kit is pretty much the most economical and effective way to build the RV-10.
That would be true if I were building a plane during the hours I would normally be designing structures for money. This kind of activity is supposed to be nights and weekends, ya' know?
 

way_up_noth

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This is in an effort to keep subject matter where it belongs. If you want to see the engine discussion this came from, it is here: Trying to achieve turbonormalizing the home-built way

IF.... IF you wanted to increase the Vne on the CH 640 by Zenith, how would you do it?
Specifications and design limitations are listed here: Performances & Specifications

RV-10 Vne - 230mph
CH640 Vne - 175mph

What aspects are different between the two that would result in such a large difference?

aaaaannnndddd.... GO.
The ch640 does not have counter balanced ailerons ...the aero dynamics of the wing makes up for this.... to my knowledge there has never been a flutter problem with the 640 ailerons... but it’s not designed to be a speed demon

The 640 has very chubby wings ... very pregnant airfoil ... perfect for flight schools... the ch2000 is still flying students around...

It was not designed to be a rv10
 
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