Very low aspect ratio planes?

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rotax618

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Oct 31, 2005
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Evans Head Australia
The most successful of the large models had very small tip fins, these models were built and flown many years ago, I thought the addition of small tip fins would increase the span efficiency, but in reality they actually disturbed the stability of the vortex, I discovered this much later while testing various planform shapes of sheet foam models.
 

lr27

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Nov 3, 2007
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I have a delta planform model made of flat foam that has a central fin and rudder. The rudder is effective. Adding it made a significant improvement n slow flight at high angles of attack.
 

Riggerrob

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Sep 9, 2014
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Canada
Dear Rotax 618,
Full-sized Saab Drakens also had nasty stall characteristics.
They could get into a deep stall where wing tips were stalled, but forward LERX were still lifting. The
Swedish Air Force eventually developed a stall recovery technique that depended upon momentum to depress that nose and many thousands of feet of altitiude!
 

cluttonfred

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Feb 13, 2010
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I think that's what Rotax 618 was implying when saying that SAAB spend millions to learn what an inexpensive model also demonstrated.

I have no idea how it would impact vortex generation and other issues, but one thing that has occurred to me using all-moving outer wing sections as elevons to provide docile stalls because the elevons would be nose-down as the wing goes nose-up. Such elevons were used in some non-delta tailless designs like the Short Sherpa and Granger Archaeopteryx.
 

danmoser

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Feb 1, 2010
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641
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Sandy, Utah, USA
I have a delta planform model made of flat foam that has a central fin and rudder. The rudder is effective. Adding it made a significant improvement n slow flight at high angles of attack.
That parallels my experience as well.. mine was essentially a flat plate equilateral triangle delta with a central rudder, AR~2. I was able to turn it without using ANY rudder input (elevons only), but a modest amount of rudder allowed it to carve cleaner, tighter turns.. I could also turn it with rudder only, but not quite as easy. It would maintain lateral control, even at very high AoA, nearly vertical descent.... next step is to build an improved version with motor & prop.
 

Johan Fleischer

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Aug 24, 2019
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Pinterest is a time wasting site, as it doesn't distinguish between delusions, concepts, plans, aeromodels, prototypes, or production machines. Terrible!
hehe, I agree. Pinterest is not to be regarded as a useful tool. Just for entertainment and fun. But sometimes one of the things view'ed as entertainmant, gives a little spark of interest 🙂
 
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