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Malcolm C

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That is a steel pipe, it is not a leading edge just a form to strap down the wet plywood to shape it prior to fitting it onto the leading edge of the wing. It was an Idea I copied from the great Tony Bingelis .
 

rtfm

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So you have no LE reinforcement under the ply or do you have some sort of dowel/pipe to support the plywood between ribs and to offer hangar rash protection?

Duncan
 

rtfm

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Hi all Flea-bitten folks
Someone asked me the other day why all Fleas had the front wing higher than the rear, and I was stuck for an answer. Something like this:
1616889250651.png

Anyone know?

Duncan
 

Vigilant1

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Hi all Flea-bitten folks
Someone asked me the other day why all Fleas had the front wing higher than the rear, and I was stuck for an answer. Something like this:
View attachment 109044

Anyone know?

Duncan
I believe the high wing allows for improved pitch stability. One problem with the earlier fleas, and a contributor to crashes, was the underappreciated importance of the craft's vertical CG in relation to the main wing on these aircraft. Neal Willford goes into the flea/ vertical CG/pitch stability issue a little in one of his old Sport Aviation articles.

Lots of folks have learned a lot of things the hard way in aviation, and that is certainly true for tandem wing designs.
 
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Malcolm C

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The leading edge of the wing has a 10 mm x 20 mm spruce stringer slotted into all the ribs, the plywood wraps around it from the top of the forward spar to the bottom of the forward spar forming a "D" cell leading edge. The lower surface has been scalloped per the plans for inspection purposes.
 

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Hot Wings

Grumpy Cynic
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was the underappreciated importance of the craft's vertical CG in relation to the main wing on these aircraft.
This^

A Flea can be considered a subset of the Spratt. CG above the aerodynamic center moves aft when the wing pitches up - further amplifying the pitch up. With the CG under the AC the reverse is true.
 

BBerson

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With respect to power changes, the low wing airplane with thrust line above CG is more stable. Source: page 234 of Perkins and Hage, Stability and Control.
 

Dana

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The interference between the Flea's closely spaced wings is a major part of its aerodynamics and stability. The Quickie, OTOH, has two long skinny wings farther apart so its aerodynamics is very different. The other image above is just a negative stagger biplane with a conventional tail.
 

rtfm

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The interference between the Flea's closely spaced wings is a major part of its aerodynamics and stability. The Quickie, OTOH, has two long skinny wings farther apart so its aerodynamics is very different.
Hi Dana,
This fancy that the two wings of the Flea somehow form a slot effect dates back to Mignet himself. And Mignet - and all who follow his "formula" without questioning the master - have perpetuated this idea. It is nothing but a fancy.

In order for the slot effect to exist at all, the two wings have to be extremely close to each other. A Fowler flap, for example, has little or no effect if the gap is too large. How large? Between 2% and 3% of the front wing chord (24mm to 36mm). If the Flea wings are further apart than this, we can expect rapidly decreasing effectiveness. At 200mm or more, the slot effect simply doesn't exist.

Barnaby Wainfan (principal aerodynamics engineer for Northrop Grumman’s Advanced Design organization) in Kitplanes Magazine May 2017 wrote with reference to the wind tunnel tests conducted in the HM 14 Flea: "the [British] wind-tunnel results show that this Venturi effect did not happen".

Regards,
Duncan
 

rtfm

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Great software is a trap for new players. DevWing CNC offers so many great features, that it has proved very difficult to keep to the straight and narrow and not get seduced into wonderful (but eventually unproductive) byways.

So, after creating a beautiful elliptical planform with sexy swept back wing tips, I realised that (of course) it would not be possible to wrap the ply around the D-Tube. Doh!

So I've retreated to a rectangular planform.

Sigh...

Anyway, busy recovering from surgery at the moment, so am off my feet. Good time for working on the CAD. I *think* I have the wing sorted now. As soon as the painkillers wear off and my mind starts working properly again, I'll hobble to the workshop and start cutting wing ribs. I can't wait.

Duncan
 

WonderousMountain

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Reverse stagger is stunning and effective,
But a series of tandem wings show it to be
perilous stall blanketing, which is different
than saying it has poor pitch character.
 
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