Volksplane VP-2 Mk2 wing project

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FritzW

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I read the question as "with VP-1 rib spacing on a VP-2 wing, do you need a VP-1 style torque box?".

Side note: I wonder why Evans put the VP-1 torque box in the middle of the wing instead of at the wing tip. It seems like it would be a whole lot more efficient at the wing tip.
 

plncraze

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That is a good question. In Evan's first article on the project in Sport Aviation he talked about doing a couple of years on design and researching engines and materials. One would think it has a good reason for being there.
 

Starflight

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Just to clear up the mystery; I read a report on the early flight trials of the F-86 Sabre and a problem arose when the large ailerons were deflected during a high speed pass, creating a reverse control (wing twist) situation and causing the pilot to complain to the tower with a loud : " J***s Ch***t!" Perhaps the VP-1 wing twist, generated by camber as well as aileron deflection, might have been made worse by the use of the single bolt attachment at each mid-spar location (pivot point).
 

cluttonfred

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I don't see how the mid-spar attachments could have anything to do with the VP-1 wing rigidity. Bill Beatty in FLYING THE EVANS VP says that the torque boxes were added to improve aileron responsiveness, nothing more dramatic than that.
 

FritzW

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The only problem that led to the VP-1 torque box was the mentioned anti-servo (twist) action in the wing. Apparently it was bad enough that they didn't fly it again until they added the TB.
A little wing twist translates into big loads in the cockpit gussets. ...I found out the hard way ;)

bent gear.jpg

I'm just wondering why he put it in the middle instead of the tip.
 

TFF

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He probably put the box where the twist is biggest. Are you just making a kit for your friend or are you helping put the wing together?
 

FritzW

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The twist is biggest at the tip but he put the box in the middle of the wing. ...still a head scratcher for me.

The wing is being built in Texas ;/ but I'm sure he'll send me pictures of the build.
 

TFF

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I hope to see it go together.
Even though the twist is the most at outboard, I would think you would arrest the twist inboard. The twist would be starting after the strut. Lock it out there.
 

FritzW

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The only way to stop the twist is to do it at the end.
It would be fairer to say "The best way to stop the twist is to do it at the end".

I think: If you consider the cockpit to be it's own TB (gussets forming the 6th side of the box) then putting another TB at the tip would be the most efficient. If you don't consider the cockpit to be a TB then putting the TB in the middle of the wing is best (assuming your TB is limited to a few rib bays).

...that's my story and I'm sticking to it ;)

EDIT: none of this applies to the VP-2 wing.
 

poormansairforce

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poormansairforce

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If the cockpit was a proper TB the wings couldn't twist. It must have flexed enough to allow the wings to act as anti-servo tabs. ...I bet that first flight was pretty exciting
If it twisted at the fuse then why didn't he fix it at the fuse? I assumed the wing itself twisted outboard of the struts hence my first comment about the TB being at the tip. Does this have to do with the low wing/inverted struts? How does the VP-2 differ from this?
 

FritzW

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If it twisted at the fuse then why didn't he fix it at the fuse?
I'm not sure it could be fixed at the cockpit and still leave room for the pilot. The cockpit gussets take up just about all the real estate they can on the "6th face" of the TB. With the -relatively- short span outboard of the struts and the beefy spars, I don't think twisting outboard could be much of an issue. Especially twisting caused by the ailerons.


Re: lighter fuselage
There was a post a few years ago about ways to lighten a VP-2. The fuselage does (IMHO) have lots of ways it could loose weight and stay just as simple to build.
 

GeeZee

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Well if we’re making requests I’ve been pondering a parasol wing VP1. Add a turtledeck behind the pilot with a little headrest. Hmmmmm
 
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