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View Poll Results: How do you feel about a plans-built Sperry Messenger semi-replica?
Sign me up, I'd build one! 2 11.76%
I might be interested, depending how it turns out. 4 23.53%
Sorry, not my cup of tea. 11 64.71%
Voters: 17. You may not vote on this poll

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Old 08-27-2010, 07:56 AM   #1
cluttonfred
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Please don't forget to respond to the poll!


All,


I am working with a designer on a concept for a semi-replica of the Sperry Messenger biplane.


<DIV align=center>
<DIV align=center>Verville-Sperry Messenger at NASM Udvar-Hazy
<DIV align=center>(Click "Long Description" for the detailed article.)


If you don't know the Messenger, it was designed by Alfred Verville for the U.S. Army Air Service in the early 1920s as the aerial equivalent of a motorcycle for military couriers. It's short span (under 20') and overall small size and simplicity were intended to allow operation from small fields and country roads. Unusually, it used struts, with neither flying nor landing wires, to simplify rigging and maintenance.


The Messenger earned it's claim to fame in experiments operating aircraft from airships as the first ever to succcessfully hook up and detach from an airship in flight. It was also used as the basis for an early "aerial torpedo" (guided missile) and frequently used in early NACA aerodynamic research because it's small size allowed it to fit in the wind tunnel.


This replica would duplicate the lines, wooden construction, bracing struts, etc. of the original but likely at about 90% scale, simplified for easier building and light enough to operate as a microlight in Europe, so about 400-425 lbs empty weight. Not aerobatic, but utility category to allow some tossing about, and powered by a direct-drive1835cc VW conversion. The closest equivalent available today is probably the Fisher Youngster.


Is this something that might interest any of the members of this forum?


Cheers,


Matthew



Please don't forget to respond to the poll!Edited by: Matthew L


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Old 08-27-2010, 10:57 AM   #2
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I came down on the "Sorry..." side. If I did this, it would be a full scale replica. Except for the engine, the effort would be very similar. Plus, at 6'4" tall, bigger is always better.

Unless you change the airfoil, your spars are going to be very small. I'd suggest a thicker airfoil but one with under camber to retain the look of the wing tips. And for your 90% version, a dummy three cylinder radial........Bill



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Old 08-27-2010, 12:01 PM   #3
cluttonfred
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My preference is also for a full-scale replica, but given the limits of the European microlight class the scaling may be necessary to keep the weight down without having to go odd or exotic construction methods. I do expect that the airfoil will change to something along the lines you mention.
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Old 08-27-2010, 03:55 PM   #4
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Not my cup of tea, but the wing struts should save a potential builder a bunch of money vs. flying wires.


Definitely needs to have a radial on it to make it sell, hope there's one available in the size you will need.


If possible, I'd also post this question on a forum that has a large following of the micro-light aircraft.
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Old 08-27-2010, 08:09 PM   #5
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The way to go is full scale. When a plane is scaled the linear lines are to scale. However the surface area is not. At 90% scale you will have 81% of the full scale surface area. Something to keep in mind. As Sir Sopwith stated one time about building replicas of early aircraft, "Make sure you're not authenticity dead."
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Old 08-28-2010, 01:47 AM   #6
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I like all biplanes. Seen some films of the Sperry really getting horsed around - very impressive considering the time. Lots of opinions on replicas...personally if I wanted to build a replica it would be to experience the actual airplane - vices and all. I would not change the airfoil - particularly since it wasa nice flying airplane for the time.I'd make it as close to the original as practical. Early airplanes with thin airfoils had routed (very wide) spars to attain the needed bending and column strength. It is more work but it's certainly within the capabilities of a homebuilder with router and a lot of tenacity. The end product would certainly be unique. On the other hand, if you just want anice flying biplane build a proven sport plane. Nothing wrong with borrowing some of the ideasfrom the Messenger. It might be worth looking at the Mong Sport (also strut braced biplane) - very pretty airplane and very light.Good luck with your project, Mathew!
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Old 08-28-2010, 11:37 AM   #7
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If you're doing a scale version and want to keep the weight down, you'll need a thicker airfoil so the spars can be taller. This improves both column and bending strength while using less material. You'll have more material in the ribs but I think the total package will be lighter.

The only way to experience the "real" airplane is to duplicate it in every respect. This is what I'd want to do but that's a different goal than the OP has. I've toyed with doing a Sparrowhawk for quite a few years. It would be a very challenging project and I wouldn't do it if I couldn't build a "duplicate" in every possible way.......Bill

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Old 08-28-2010, 12:39 PM   #8
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I've lusted for a Sparrowhawk ever since I saw a picture of one in Air Progress hooking up to a trapees thing on an airship. That must have been around 1973. Like you say Bill, BIG project.
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Old 08-28-2010, 05:40 PM   #9
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"you'll need a thicker airfoil so the spars can be taller. This improves both column and bending strength while using less material."
I-sections are far more efficient but also more work. Tall skinny spars buckle laterally particularly in externally braced structures like biplanes where the brace wires (or struts in this case)impose large compression loads inboard of the I-strut.
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Old 08-29-2010, 06:26 PM   #10
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The Flitzer kinda sorta looks like the Sperry.
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Old 08-29-2010, 07:28 PM   #11
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Quote:
Originally Posted by Chopmo
I-sections are far more efficient but also more work. Tall skinny spars buckle laterally particularly in externally braced structures like biplanes where the brace wires (or struts in this case)impose large compression loads inboard of the I-strut.
I was thinking an "I" or box section when I wrote that. Also, there is some contribution from the compression ribs, drag wires and leading edge (if you have a "D" section design) to keep things in column.
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Old 08-30-2010, 01:51 AM   #12
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cwilliamrose,


I'm poking at your statement"...to keep the weight down, you'll need a thicker airfoil so the spars can be taller. This improves both column and bending strength while using less material"


The point Iam trying to make is that before you go increasing airfoil percentage on an airplane with a HUGE chord and wide spar spacing you probably ought to run numbers to see if such a compromise is warranted. Engineering is done with numbers. Anything less is conjecture.


The Sperry did not have a D section. Not sure how drag wires help"keep things in column."They certainly aggravate the compression loads imposed on the spars. Presumably drag wires and compressionribs are the same for thinwing verses thick so not sure what your point is there.
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Old 08-30-2010, 10:04 AM   #13
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Having taller spars gives you the option to take away some width and make a lighter structure. Obviously it has to be done properly. As far as keeping the spar in column, if you have two drag bays the column is stiffer as a result. You are creating a wide structure that includes the rear spar. One drag bay only adds to the compression load as you point out and does nothing for the stability of the column.

If I were doing a scale version of this airplane, I would look at a D section leading edge design to gain advantages both structurally and aerodynamically.

At this point we're not engineering an airplane, we're kicking around design ideas. Both processes have their time and place............Bill

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Old 08-30-2010, 09:34 PM   #14
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"Having taller spars gives you the option to take away some width and make a lighter structure."






It is exactlythis reasoning that is concerning. As I said before, tall skinny spars are susceptable to lateral buckling in externally braced wings. For example, take a spar 4 in by 1 in and increase it's height to 5 in. Merely maintaining the same weight requires a reduction in thickness to .8 inches. Bending capability about the minor axis is increased in the taller spar by 56% so it must bemore capable-right? Not so fast. The taller thinner spar will buckle first because its column capability is REDUCED by 36%.



For externally braced wings it is desireable to make the wing only as thick as it needs to be in order to optimize the spar.

I must have misunderstood you when you said that he will "need a thicker airfoil". I get it now...that was your conjecture.It might be better to let the numbers bear out whether a compromise (like completely changing the aerodynamics) is needed.
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Old 08-31-2010, 08:18 AM   #15
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