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Synchronicity S8E R/C R/G

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.



Building notes

(The following are basic building notes on the 1986 version of Synchronicity. At the time, I had used a relatively crude method to build up the flat bottom wing airfoil by using triangular ribs aft of the airfoil high point. Dind't start using realribs and specific airoils until later. If I was building new Synchronicities today, I would probably get foam wing cures cut rather than build up the wings).

Select all wood parts carefully for low weight and adequate strength, most especially the wing. Synchronicity is designed with an E6 in mind and should not weigh much more than 8 ounces at liftoff. My first bird weighed 7 ounces at liftoff, second one weighed 6.75 ounces at liftoff. Significantly more weight will cause excessively slow boosts at major loss of potential altitude using an E6. If you do not feel capable of building this light enough, consider shortening the wing center section from 16" to 12" and going with a balsa center spar (the spruce or graphite center section spar needed only for the 40" span version of the wing). If your R/C gear is too heavy, this model will not be suitable at all for E6 power, yet it will likely shred the wing on any other E engine (like the E10).

Use cyanoacrylate (Hot Stuff) glues for construction, epoxy is to be avoided completely.

Assemble the critical assemblies as accurately as possible. A warp in the wing or having the rudder slightly offset will lead to trouble in trimming the model to both boost and glide. The stabilizer needs to be glued to the fuselage so that it is at a zero angle of attack relative to the wing, otherwise the faster the model boosts the more it will try to pitch up. The fuselage tends to bow upwards from the transition to triangular cross section, so do not go by the stabilizer relationship with the rear fuselage! The wing should be laterally balanced: that means when balanced at the center neither wingtip droops. If not balanced, make a small hole near the tip block and insert necessary weight to make it balance correctly (Hot Stuff the weight in position, Hot Stuff alone may be enough weight for most wings). Cover the hole with an adhesive mylar patch.

The model should be given a tissue finish, Monokote is an option if model not too heavy already.

     The models have required a glide CG close to 50% of root chord, somewhat unusual for an R/C glider. The exact CG your model requires may vary, plan the R/C installation to allow for some shifting of components after the first test glide session. If the model requires a lot of up elevator and the nose drops too quickly, shift the CG more to the rear. If the model stalls too easily or you have to jockey the elevator stick too much, move the CG more forward (if the elevator requires down trim the stab may be at a positive angle of attack and require repositioning). If the model requires more than a slight amount of rudder trim there is probably a misalignment somewhere: warped wing, one tip panel not parallel to the center section, crooked fuselage or rudder, etc. Consider whether you can correct it or live with it. This is important because even though the model may glide horizontally straight with a lot of rudder trim, it may roll during vertical boost flight.

Synchronicity was designed to fly with the use of dual rates on the transmitter, with very low elevator and rudder movement for boost. It also must be set for boost with a lower elevator angle than used for glide (not necessarily negative). It seems possible to find the "ballpark" boost trim location by hand launching the model upwards at a 30 degree angle. When the model does not pitch up or down for the first 10-15 feet, you are in the area of the right boost trim. Note your transmitter trim lever position, or better yet add a second trim control and switch to your Tx to switch between boost trim and glide trim positions.

A tower type launcher is highly recommended, as it gives a straighter launch and does not induce any launch roll. The tower these models have flown from uses two 3/4" diameter aluminum tubes for the main guidance rails, providing about 5 feet of direct guidance. Many flights have had very little if any roll, allowing complete concentration on pitch control without also having to correct roll. Test flights can be made with D12 power.

This design ought to make a good Boost Glider as well. The 6 ounce glide weight with engine casing and pod would be about 5.25-5.5 ounces as a Boost Glider.


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