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| In 1986 I finally got serious about doing R/C R/G's, as opposed to the pop-pod R/C B/G's that I had sometimes modified into R/G's by adding a slide pod or even a slide-wing. So I worked up a design meant from the start to be flown as an R/C R/G, no moving parts. Gave it the name of Synchronicity. The basic layout of Synchroniicty was not special. It used a Flagship type of layout. Except that the fuselage was longer, yet as narrow as the radio gear allowed. It was larger than a Flagship, with span of 40" and wing area of 160 sq in. It worked out well. As my first no moving parts R/C R/G, I helped make the lauches smoother by also bukding my first R/ R/G tower, better liftoffs than with a lach rod and lugs. Made a lot of flghts on D12 power, there was no such thing as relaodable D7 and E6's at the time, and expendable E6's were so costly that they were not used as often as D12's were. In any case, I was able to handle E6 boosts with this model. Flew it at the 1986 Team flyoffs and made the S8E team. For 1987, the design was refined a bit more, a bit more wing area, and fuselage tweaked so the servos were in the nose, allowing the fuselage under the wing to be reduced in height to allow only for the Cannon super micro receiver and 50 mAh nicad pack. That was the design I used at the 1987 WSMC in Yugoslavia, to win a bronze medal. The design was tweaked a little more wit a little bit more wing area in 1988, up to 44" span and 180 sq inches. Unfortunately right now I have only one photo, of a model in flight. But do have plans and short building notes. Click here for an overview of the 1986 original version. click here for full size plans of the wings of the 1986 version. Click here for ful lsize plans of the fuselage of the 1986 version. Click here for an overview of the 1988 version. I built at least 15 Synchronicity models from 1986 to 1995. A couple were for the NAR "R/C Glider" Event, using external "Vee" airbrakes flush to the rear fuselage until deployed up and outward. I stopped using my own designs for FAI flying when Kevin McKiou came out with his all-composite Stingray design in 1995. I started flying those instead, used one to take the Bronze medal in S8E at the 1996 WSMC. |
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Building notes
(The following are basic building notes on the 1986 version ofSynchronicity. At the time, I had used a relatively crude method tobuild up the flat bottom wing airfoil by using triangular ribs aft ofthe airfoil high point. Dind't start using realribs and specificairoils until later. If I was building new Synchronicities today, Iwould probably get foam wing cures cut rather than build up thewings).
Select all wood parts carefully for low weight and adequatestrength, most especially the wing. Synchronicity is designed with anE6 in mind and should not weigh much more than 8 ounces at liftoff.My first bird weighed 7 ounces at liftoff, second one weighed 6.75ounces at liftoff. Significantly more weight will cause excessivelyslow boosts at major loss of potential altitude using an E6. If youdo not feel capable of building this light enough, considershortening the wing center section from 16" to 12" and going with abalsa center spar (the spruce or graphite center section spar neededonly for the 40" span version of the wing). If your R/C gear is tooheavy, this model will not be suitable at all for E6 power, yet itwill likely shred the wing on any other E engine (like the E10).
Use cyanoacrylate (Hot Stuff) glues for construction, epoxy is tobe avoided completely.
Assemble the critical assemblies as accurately as possible. A warpin the wing or having the rudder slightly offset will lead to troublein trimming the model to both boost and glide. The stabilizer needsto be glued to the fuselage so that it is at a zero angle of attackrelative to the wing, otherwise the faster the model boosts the moreit will try to pitch up. The fuselage tends to bow upwards from thetransition to triangular cross section, so do not go by thestabilizer relationship with the rear fuselage! The wing should belaterally balanced: that means when balanced at the center neitherwingtip droops. If not balanced, make a small hole near the tip blockand insert necessary weight to make it balance correctly (Hot Stuffthe weight in position, Hot Stuff alone may be enough weight for mostwings). Cover the hole with an adhesive mylar patch.
The model should be given a tissue finish, Monokote is an optionif model not too heavy already.
The models have required a glide CGclose to 50% of root chord, somewhat unusual for an R/C glider. Theexact CG your model requires may vary, plan the R/C installation toallow for some shifting of components after the first test glidesession. If the model requires a lot of up elevator and the nosedrops too quickly, shift the CG more to the rear. If the model stallstoo easily or you have to jockey the elevator stick too much, movethe CG more forward (if the elevator requires down trim the stab maybe at a positive angle of attack and require repositioning). If themodel requires more than a slight amount of rudder trim there isprobably a misalignment somewhere: warped wing, one tip panel notparallel to the center section, crooked fuselage or rudder, etc.Consider whether you can correct it or live with it. This isimportant because even though the model may glide horizontallystraight with a lot of rudder trim, it may roll during vertical boostflight.
Synchronicity was designed to fly with the use of dual rates onthe transmitter, with very low elevator and rudder movement forboost. It also must be set for boost with a lower elevator angle thanused for glide (not necessarily negative). It seems possible to findthe "ballpark" boost trim location by hand launching the modelupwards at a 30 degree angle. When the model does not pitch up ordown for the first 10-15 feet, you are in the area of the right boosttrim. Note your transmitter trim lever position, or better yet add asecond trim control and switch to your Tx to switch between boosttrim and glide trim positions.
A tower type launcher is highly recommended, as it gives astraighter launch and does not induce any launch roll. The towerthese models have flown from uses two 3/4" diameter aluminum tubesfor the main guidance rails, providing about 5 feet of directguidance. Many flights have had very little if any roll, allowingcomplete concentration on pitch control without also having tocorrect roll. Test flights can be made with D12 power.
This design ought to make a good Boost Glider as well. The 6 ounceglide weight with engine casing and pod would be about 5.25-5.5ounces as a Boost Glider.
