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Offline Motorman

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« on: October 31, 2017, 10:56:21 PM »
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« Last Edit: December 08, 2021, 12:48:45 PM by Motorman »

Offline Tim Wescott

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Re: Tapered Trailing Edge
« Reply #1 on: November 01, 2017, 12:08:44 PM »
Do you mean a swept trailing edge?  Because a flap hinge point that gets thinner from root to tip wouldn't have any bearing on the flap horn, but one that's swept forward or back might.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Paul Smith

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Re: Tapered Trailing Edge
« Reply #2 on: November 02, 2017, 09:21:02 AM »
I'm not sure they do.  I figgered that the bent flap line was just a byproduct of the tapered wing layout that the designer wanted.   You can only get a limited amount of taper with the Nobler-style wing.  Maybe Werwage (Ares) and others wanted more taper than a Nobler & just accepted the bent flap line a necessary evil.
Paul Smith

Offline Ted Fancher

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Re: Tapered Trailing Edge
« Reply #3 on: November 02, 2017, 01:14:46 PM »
I'm not sure they do.  I figgered that the bent flap line was just a byproduct of the tapered wing layout that the designer wanted.   You can only get a limited amount of taper with the Nobler-style wing.  Maybe Werwage (Ares) and others wanted more taper than a Nobler & just accepted the bent flap line a necessary evil.

Strictly a guess on my part as swept forward flap hinge lines are not common among designs of the last couple of decades...

To the best of my recollection swept forward hingelines became common in roughly the mid to late '50s and were a regular feature of the then popular I-beam stunters like Billy's Ares, Steve Wooley's Argus and others.  My guess is that that era was when the search for very light, low wing loading ships became an important design criteria for top fliers in search of optimum performance...especially given the comparatively modest outputs of the powertrains of the era.  (In support of that I offer the previous generations of very popular Bob Palmer designs which utilized partial span and/or narrow chord flaps...the T-Birds in the first example and the Indian ships...Chief, Squaw, Papoose, etc....in the latter).

Combined with the search for lighter wing loadings (more lift per unit of wing area) was the ubiquitous throughout stunt history search for the most beautiful stunt ship including not only paint jobs but pleasing shapes and  complementary lines...such as tapered and or curved wing/tail planforms which were not only lovely to look at but eye catching as well.

One way to make a more attractive airplane was to forego the often constant chord or very modestly tapered wing/tail planforms.  Both high tapers or elliptical planforms, however, when combined with a straight hinge line resulted in flaps being shortened, narrowed quickly in chord or some combination of both...which flew in the face of the search for lowered wing-loading (less lift per unit of span and/or area of high lift device).  Designers might well have attempted to circumvent this loss of lift by utilizing a swept forward hinge line so as to allow for a greater percentage of flap area and/or flapped span to maximize the then ubiquitous demand for more area per unit of weight. Note, for instance, how much flap area and. perhaps, even a tiny amount of flap span would be sacrificed if the flap hingeline of the famous Ares weren't swept forward an inch or so.

A few of the modest but valuable changes made in more recent design criteria, larger tail volumes coupled with CGs located further aft plus, in no small measure, the availability of powerplants and operating systems thereof which allow modern stunt ships to be much less critical in terms of wing loading have minimized the search for larger flaps.  Wing loadings nearly half again greater than once though mandatory now routinely compete for our greates championships (I know, some still scoff at a sentence like that but an unbiased chart of the weight, wing and flap area of the vast majority of Nats Champions for the last couple of decades or more would support the accuracy of the statement...as would a breakdown of the powerplants pulling them around).

The bottom line in this evaluation of the swept forward hingeline is that it came about for the reasons listed and pretty much fell off the stunt design landscape as we became more aware of and desirous of utilizing optimum CG location, minimizing the effects of (flap induced) pitching moments and optimizing the size of the little wing in the back relative to the big one up front.  (Although they may well be utilized in special applications such as serious semi-scale ships with distinctive wing planforms...such designs have managed to win a few as well!)

Ted

p.s.  A couple of designers, one a giant of the modern era, believed and published their belief that swept forward hingelines made flight trimming more difficult and subject to response problems under difficult flight conditions.

Edited due to a messed up and incomplete paragraph.
« Last Edit: November 02, 2017, 05:31:46 PM by Ted Fancher »

Offline Tim Wescott

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Re: Tapered Trailing Edge
« Reply #4 on: November 02, 2017, 04:01:54 PM »
What Ted said.

I've seen comments that a swept-forward flap hinge line is great when it's calm, but makes the plane harder to deal with in the wind.  I haven't tried, so I can't say.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline phil c

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Re: Tapered Trailing Edge
« Reply #5 on: November 02, 2017, 08:00:03 PM »
A friend of outs, Dave Noel, came up with a number of very flyable stunters, mostly foam wings, in the 80's.  He used double tapered wings on most of them- something like 1.5in le sweep and 1-1.5 in forward sweep in the trailing edge.  He worked it out that the flap horn was a normal, straight construction.  The trailing edge of the wing inside the fuselage was squared off between the sides for mounting the flap horn.  The flap arms extended about 3/8 past the fuse side to leave some room for fillets, and the flap arms were bent 90deg to the trailing edge.  That minimized any wiggly movement of the arms in the flaps to only 1/32in. or so  which was soaked up by either silicon rubber glue in the flap or a lucky box. 

We just flew one of his old planes that Al fixed today.  despite two crashes and 25 years, it still flies well on a FP 40 or the old ST 46
phil Cartier


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