Eric,
I have a "theory" . . .
HYPOTHESIS : The "Tail Moment Arm" may play a big part in Glide Performance & Trimming.
(1) In those video's, all of the high-performance gliders have LONG Tail Moment Arms and glide extremely FLAT ( yes, the Wing Loading is super-low ).
(2) The Holverson Swinger has a SHORT Tail Moment Arm and a much steeper Glide Angle ( yes, the Wing Loading is higher ).
Whether a Conventional glider or a Canard glider, I believe that the effect of the Tail Moment Arm may be the same . . .
https://aviation.stackexchange.com/questions/47306/does-static-longitudinal-stability-require-download-on-the-tail
http://softskills4us.blogspot.com/p/aero.html
http://www.phoenixmp.com/articles/preptodesign.htm
EXCERPT :
2. Tailplane
The size of the tailplane is going to have a direct impact on the model's pitch stability along with the tail moment arm (distance between the mean chords of the wing and tailplane). Within reason larger the tailplane / moment arm the more stable the model. It is possible however to have too powerfull a tailplane whereupon in certain dive situations the tailplane takes over and holds the model in the dive until up elevator is applied. I experienced this on a number of occasions when I flew single channel gliders in the mid-sixties.
A starting point for tailplane area is 15% of wing area with a mooment arm of 3
x mean wing chord. The tailplane on 'Tee' tail models is more efficient than one fitted at the base of the fin so a slightly smaller tail can be fitted (12 - 15%). 'Vee' tail models have perform the function of both the fin and the tailplane. As a rough guide the fin area is approximately half that of the tailplane so the 'Vee' tail angle must be set to attain this ratio when the tailplane is veiwed from above and the side. If you do your sums this works out at approximately 110 degrees but for convenience I always use 120 degrees (60 / 30 set squares). Actual tailplane area needs to be increased by 2 - 3% to make up for the area 'lost ' due to the angle but it is still less than the total area of a conventional fin and tailplane. I have built a number of models that have been fitted with both a conventional tailplane and a Vee tail and in my experience the vee tail out-perform the conventional tail but they are aerodynamically less abusable without biting back! Basic trainers need good in pitch stability so fit a slightly larger tailplane of 18 - 20% of wing area.
Fin Area
As mentioned above the general rule for calculating fin area is half the tailplane area or 7 - 9% of wing area. Again the further aft the fin the more effective it will be. Please remember though that the fin still has to perform like a wing even though it is fully symmetrical and mounted vertically. It still has to produce 'lift', albeit horizontally. It is not just a paddle that is stuck out into the airstream.
Moment Arm
Choosing the correct moment arm is a bit of a compromise. The longer the tail moment arm the more stable the model will be in pitch and yaw for any given area but the model will require more nose weight to achieve the correct balance point . Long fuselages also increase the wetted area and the fuselage volume therby increasing parasitic drag i.e. drag not associated with lift production. Likewise a short nose moment will increase the weight required in the nose. Another side issue and quite an important one is that loong fuselages are more vulnerable to damage on an arrival due to the 'whiplash' effect.
A good starting point is to set the tail moment arm at 3 x Mean Wing Chord. The tail moment is the distance between the aerodynamic centres of the wing and tailplane. The aerodynamic centre of a section is assumed to be 25% back from the leading edge. Nose length can be provisionally set at 1.25 x Wing Root Chord.
END EXCERPT:
Dave F.