Brett Bucks SkyRay 3.5

I clipped this from an archived thread; I scored a SkyRay 3.5 from the classified section (Thanks Leonard) and found some good information here. I was just wondering if Brett has made any of the mods to the fuse length or tail volume that he wrote about.

I have a “Dan Rutherford” autographed OSFP .21 with a picture of his face laser etched on the side of the case and a thumbprint on the muffler that I’m thinking of using on this model. Although I may sell it on Ebay and payoff my house. I’m not sure yet.

>Hey, guys. I finally got my
>printer working but now I
>have lost all references to
>the above plane. I must
>be too old to figure
>out the way to get
>to older stuff from the
>archives. I could use the
>addresses or just any info
>remembered about it all, and
>especially Brett Buck's info. I
>got the kit, I got
>the .20FP but I need
>details.

Not too many details! I suggest building right as it comes out of the box, with two exceptions - get some 2-wheel landing gear, and put the fin on with no rudder offset and no airfoil at all. For the landing gear, I have used both the landing gear SIG sells for the Phazer, and a Hallco fuselage-bottom R/C gear, cut in half, and re-bent to go up along the fuse sides. The rudder and fin offset should be self-explanatory, but measure it very carefully. Otherwise, build as shown, including Monokote on the wings, and minimal finish on the fuse.

Run the engine exactly as it comes out of the box, with the stock muffler, not modified in any way! This includes the stock needle/spraybar, stock .259 venturi, stock muffler baffle, stock muffler outlet hole, no changes at all. Use a 9-4 APC prop. Use either a 3 oz tank no more than 1.5" wide with uniflow open to the air, or a Sullivan 4 oz. clunk tank set up for suction, with muffler pressure into the vent, anbd with the wide side against the fuse. In the winter, or at sea level, or if you crash a lot, use a Bru-Line "fine" air filter. I use whatever 10% fuel I happen to have around - don't use all-castor. SIG, Powermaster, etc, it doesn't care much. More nitro is not necessary but it doesn't hurt.
The engine setting with the uniflow tank should be around 11,300 rpm+- a few hundred. With a suction clunk tank, you will have to experiment a bit. It needs to be *just barely* into a 2-stroke in level flight at the beginning of the flight. Too rich and it's just too slow at the beginning. Too lean and it sags off at the end. It's a pretty narrow range of acceptable.

Balance the airplane at 12-13% of the chord - about 1" - 1 1/8" from the leading edge. The centerline of my leadout guide is 2.25" from the LE. This is about right for a 34 oz airplane on .015x60ft lines at about 4.8 second laps. The position on my airplane is fixed - I just put it were Dr. Soule's "LineII" program said to. You can put in adjustable leadouts, but don't put the leadouts anywhere but where program says unless you really know what you are doing.
This will fly pretty good as long as you get it straight. Get the wings level with warps and tipweight, then go to it.

I also recommend that you use the plans to clone a second and third airplane. Make the wings out of balsa - 3/32" ribs, full at every station, with 1/2"x1/8 medium balsa spars set vertically at the high point. Everything else is fine as it is. What this does is save about 5-6 oz. Surprisingly, without other mods, it doesn't fly significantly better (plenty of power even at 36 oz), but it's much more durable. The stock wings tend to self-destruct due to excess weight. When the nose hits, the tips just keep going, and the structure just disintegrates, even on grass. The lighter wings will just flex and then return to shape with no damage. On pavement, it's broken in any case.

The stock airplane will end up about 35-36 oz. The balsa-wing version will be around 30. The tail length is just about right for the stock wing, but the lighter airplane would probably benefit from a shorter but larger tail. It's rate-limited - it has plenty of lift to turn tighter, but the maximum pitch rate is too limited. My first significant mod will be to shorten the tail about 1.5" and enlarge it to get the same tail volume. This is just an experiment that I haven't tried. It's plenty good enough as is - I got a 540-something with it in P-40 one time, only to be beaten by David F. flying it to a 547 with no appearance points. Story of my life!

Brett

My leadouts are spaced 1" apart. Mine has the bellcrank in the normal way, meaning the rear line is up. I have had variable-spacing guides, and it's just not a particularly useful adjustment. Reasonably close together is the right spacing. The "front up" advantage is minimal in all cases, and really doesn't matter at all with a 9-4 prop and a flapless airplane. I don't want to flog the dead horse, but I don't think you should be using leadout position to control the yaw angle anyway.

I used the stock bellcrank, and I think this is plenty good enough. You don't need super-slow controls, and the margin over the Netzeband wall is plenty large enough with the 3". The control loads are very light. For the record, I also used all the stock control hardware - no ball links, graphite rods, etc. It's just not necessary.
Brett

Anything new to add?
Regards,
John Jolley