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drstress

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Bye

There is an important omission in the calculations for the "Constraint Analysis". Put there on purpose to see what would happen. All of the calculations are simple "hand, closed-form" calculations any high school algebra student should easily follow. Since no one commented on any of them, I think either no one bothered to look through them or no one has the expertise to understand them.

Either way this is my last post. I'm sure the "good ole' boy" club will pointlessly blabber on and on about any and all of my attempts to bring a small amount of order to what has to be the most random assortment of opinions I have ever experienced.

Since I don't fit in to this culture, I will welcome it as a badge of honor to be exorcised from HBA.
 
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pictsidhe

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Well this makes a pleasant change, somebody designing an aircraft using engineering methods. The forum would benefit from seeing how you have gone about it. Perhaps you could start a member project blog and drown us in details.
 

Vigilant1

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Thanks for coming back, drstress. I was afraid we'd lost you.

I'm looking forward to seeing your work.

Will you be using constant speed props for this little bird? In the similar (but more modest) centerline thrust concepts we've most extensively discussed here lately (the "Beetlemaster" and the "Micromaster") we have generally assumed fixed-pitch props (for economy purposes and due to limitations on crankshafts and front bearings of the proposed engines--VW derivatives and small industrial engines, respectively). Controllable pitch props certainly reduce the tradeoffs required between acceptable single engine climb performance and two-engine cruise speed. But, Burt Rutan was able to get good single-engine performance and cruise performance with fixed-pich props on his Defiant, so it is possible.

Thanks for letting us peer into the processes you've used.
 
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bmcj

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One thing to keep in mind is that the dual verticals will likely lose a little bit of effectiveness due to interaction between the two inner surfaces. In other words, when yaw induces a lower pressure on one inner surface and a higher pressure on the opposite inner surface, there will be some cancelation of the two pressure fields as they try to equalize. That means that the stabilizing effect will probably fall in between that of a single rudder and two rudders each acting at 100% effectiveness.

Of course, proper choices of distance and chord combinations can help mitigate some of the loss.

Just don’t be surprised if two are not twice as effective as one at twice the size.
 

Pops

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Thanks for coming back, drstress. I was afraid we'd lost you.

I'm looking forward to seeing your work.

Will you be using constant speed props for this little bird? In the similar (but more modest) centerline thrust concepts we've most extensively discussed here lately (the "Beetlemaster" and the "Micromaster") we have generally assumed fixed-pitch props (for economy purposes and due to limitations on crankshafts and front bearings of the proposed engines--VW derivatives and small industrial engines, respectively). Controllable pitch props certainly reduce the tradeoffs required between acceptable single engine climb performance and two-engine cruise speed. But, Burt Rutan was able to get good single-engine performance and cruise performance with fixed-pich props on his Defiant, so it is possible.

Thanks for letting us peer into the processes you've used.

I also thought of the Beetlemaster. If I had more time and energy I would like to built the Beetlemaster. Vigilant , I'm waiting for you to start construction.

Looking forward for this thread. Hope is not to deep for this redneck . Already like the looks of it.
 

Vigilant1

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I would like to invite everyone to participate in the design discussion. Please follow these rules:

I need critiques from knowledgeable people. All critiques must be accompanied by references to available test data or references to verifiable analysis techniques. (“Extraordinary claims require extraordinary proof.” - Occam's Razor)

I will not provide accurate dimensions. This is to prevent someone from using my data to actually build an airplane. (“Those who can make you believe absurdities, can make you commit atrocities.” - Voltaire)

I do not have a lot of experience with aerodynamics or stability, so don't believe anything that I show here until it has been verified by you or someone that has the necessary experience. (“The more I read, the more I acquire, the more certain I am that I know nothing.” - Voltaire)

Please keep personal opinion out of this. If you know there is something wrong or there is a better way, please provide references that can be checked by everyone. There is no guarantee I will incorporate your input into my design, so don't get pissy if I don't. (“Opinions have caused more ills than the plague or earthquakes on this little globe of ours.” - Voltaire)
These (rational) rules are going to get quite a workout. I might tape a cheat sheet to my monitor so I can tell who is being called out for what (me included). :)
 

Vigilant1

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Oh wow man, you make me sound like a school mar'm. I'll try to be gentle, but I want "Just the facts, ma'am, just the facts." Help me make sure that my posts aren't "calling out" anyone. I truly want this to be a group effort.
No, I'm just having a bit of fun. It will be good to keep the discussion as fact-based as possible, but that's a higher "standard of proof" than is normal here.

It is hard to herd cats! Still, you've obviously put a lot of work into this, and it deserves a disciplined discussion. And if you've got analysis to go behind your design choices (single rudder or two, to cite a recent example), I'll learn a LOT from that.
 

Retiree

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I will not provide accurate dimensions. This is to prevent someone from using my data to actually build an airplane. (“Those who can make you believe absurdities, can make you commit atrocities.” - Voltaire)
I look forward to the progress of your project. If you do not provide basic dimensions and performance targets, how can we judge what you are doing is reasonable?
Doug
 

imacfii

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You are right. Like the examples I am asking others to show, I will need to provide enough information so you can see what I am doing. As we go along, I will have to develop a method to satisfy my need to keep someone from actually building this airplane. I have been debating for awhile whether I have the time or am qualified to do what I am attempting. I do not want anyone depending on my design as a real airplane.

If anyone is serious about a detail design, it would take a consortium of several qualified individuals to pull this off. They would need to legally agree to structural static load tests, DER and DAR approval, and to a rigorous flight test program.
Why would you not want/like someone to share in your vision of creation? Is it a liability issue?
 

Pops

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Don't worry about me posting anything. You are on your own.
 

TFF

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This is an Internet forum. We talk like best friends and fight like siblings at the same time. It’s no fun when someone’s work looks, well, like work. Well thought out is great but no one wants to read a term paper. Your credentials are pretty good but there are a lot of non engineers who have designed and built some mighty fine machines that are flying today, on this site. They can generally footnote their own work. They are equally as smart as any degree. There are also top engineering type too. As serious as we can be here, this is our fun time.
 

proppastie

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So you will do structure analysis without detail design?
 

wktaylor

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Looks like a mini C336 SkyMaster**

A few general questions.

Anticipated design airspeeds: Green, Yellow, Red line/arc [VNE]?
Design +G, -G load factors?
Construction: metal, composite, hybrid?
Tandem, side-by-side or staggered?
Sticks or control-wheels?
Gasoline or diesel engines

NOTE.
Twin V-Stabs/rudders and the boom-to-boom wide-span H-Stab/elevator can create some awkward/long control-cable/rod routing to ensure fully-coordinated-movement and non-asymmetric internal-loading and clearances... especially where the booms neck-down.

Rear prop failures [blade or hub, makes no difference] can be catastrophic.

Regards, Wil Taylor
**I was lead USAF engineer for the O-2A/B (C337) for about 3-Years in the 1980s
 

wktaylor

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PS... Lighter-side : I, too, am a quotes-loving-guy... also... here are a few to consider from my files...

A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. --Saint-Exupery

At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation.” – Igor Sikorsky

Simplicate and add more lightness.” –William B Stout, Early Aircraft Engineer

The turtle only makes progress when its neck is stuck out." – often quoted by John Thorp

A camel is a horse designed by committee." --Sir Alec Issigonis, British car designer


Some fear flutter because they do not understand it. And some fear it because they do." --Theodore von Karman, aerodynamicist

Any damned fool can criticize, but it takes a genius to design it in the first place." --Edgar Schmued, Chief Designer North American Aviation

The Wright brothers’ design… allowed them to survive long enough to learn how to fly." --Michael Potts, spokesman, Beech Aircraft

I would not trust the engine now. You have an engine by design, when it is running, it's trying to throw itself apart. Throw in a prop strike, and you have a built in problem that will show up when you are asking the most of the engine. A nice hot day at altitude just below gross weight. Then bam, you’re a glider. Or as one Boeing engineer put it, "have the glide characteristics of a streamlined man hole cover." That would be a bad day. --Eric Pfalzer T-18 owner after hearing of a second prop strike by another T-18.

It has a Winchester 30-30 warranty … 30 feet or 30 seconds whichever comes first." --unknown

MIL-TFD-J1T = Make It Like The F****ng Drawing Just 1 Time --unknown
 

proppastie

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Error you can preview post under more options
Posts did not get here
 

don january

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drstress. What a large amount of time spent on the web when you could have been building and sharing
 
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