.30 fourstroke for sig skyray.

[brian thomas bennett]

Need some advice for this setup. Looking at other posts here I see that the skyray is generally powered by a good .25 2 stroke. I want to fit an asp.30/magnum .30 fourstroke and was wondering if I should increase the span by a panel on either side or lengthen the fuse as although the 4 stroke will fly the model it is likely to be heavier than a .25 2 stroke. Doing away with the single wheel setup in favour of 2 wheel fixed the same as a twister/banshee. Would appreciate your comments/thoughts on this setup.
                                                           Thanks Brian.

[Doug Morris]

   Hi Brian,
    I put a Saito 30 4/stroke on a Flite Streak a few years ago. The fusalage was streched 3 inches. It flew well, but the engine is just
 to darn Heavy for the amount of power it can create. Also the engine was Brand NEW. I traded it off to a RC guy and wished him good luck.
 I'm not sure about your Magnum, I hope It'll work out for you. I do have a Magnum 52 and it's a Super engine.
  Good Luck
   Doug M.863718

[wwwarbird]

 First, I'd save the four stroke for a more appropriate use and use a two-stroke .25-.35 on the Skyray. That .30 would probably work very well on a stock Twister if the plane was kept nice and light.
 If your set on a Skyray, the first step is to throw away the light-ply ribs and make up new 3/32" balsa replacements. Make them all full ribs instead of using the half ribs. For more wing area you can space the ribs a bit further apart than shown on the plans, like set it up for a 48" total span or so before the wingtips. Another angle/option is to add some fixed flaps to the trailing edge to give some more wing area. You could add a couple inches to the chord and leave the stab in the stock location. If you add the fixed flaps you can change the entire look of the plane depending on the shape of flap you decide on. For landing gear, I highly recommend Sig "Fazer" aluminum gear or another equivalent. The Fazer gear works perfectly on about any .25-.40 size profile, including ARF Flite Streaks and Primary Forces. The aluminum gear looks a lot better, and as a rule, holds it's shape much better than a wire gear.

[Larry Renger]

I had a Magnum .30 4-stroke, and put it on a Flite Streak.  Had to shorten the nose over 1" and put the tank inboard.  That setup worked really well (more below). Vey pleasant combination. Totally capable of a good competition pattern.  I don't recall the size of the SkyRay, but you can figure it out relative to the Flite Streak.

Then I had a chance to compare my engine to a Saito .30 four-stroke; on the same bottle of fuel and the physically same prop, there was a 400 rpm difference.  The Magnum went on sale immediately and was replaced with a Saito!  Anyway, the Flite Streak has a fat airfoil and 390 sq.in.  Balance it right, and you have a delightful combo with either engine.

Incidentally, with the inboard tank location I got a 4-8 break.     That is, I would set the model dead lean on the ground; then it would go rich in the air, but when you loaded it down in maneuvers, it would really "dig in".  A remarkably nice performance equivalent to the best 2-4 break I have managed.  You could hear the engine generate more power whenever it slowed down or was overhead.  But the transition was very smooth, not like a "break" at all, just more power in smooth proportion as the speed dropped .

There are a couple of humerous anecdotes related to this model.  First one was at a contest, I took off and flew the pattern.  The judges, who were between the two flight circles thought my engine had quit, because they could not hear it over the sound of the model behind them.  When I completed the 2nd part of the reverse wingover, they decided I wasn't planning to whip the model through the rest of the flight, the engine must still be running.

The second event was when I persuaded Keith Trostle to fly the model.  He took off, and related that he figured it was totally without adequate power.  However, he tried a climb and dive; that worked.  Next a high climb and dive; hmm that seemed OK.  Then a wingover and all is still well.  A loop? Yup, still hanging in there.  So he then did the full pattern  and was well pleased with the performance of the plane.  I don't recall for sure, but he may have done his signature square hourglass as a finale.

[brian thomas bennett]

Hi Wayne, I did have the very same engine in a stock Twister last year. It did fly quite well and the engine ran smoothly on a clunk uniflow. Sadly I flew it one afternoon that was very blustery and lost it when it came in on the lines during a wingover. I did not however make any effort to build the twister especially light as there was an O.S 40 La in it before the fourstroke. The dozen or so flights I did get out of the Twister encouraged me enough to want another four stroke powered model. I have already decided to re cut ribs in 3/32 balsa as you have recommended. I have decided not to cut the spars to length and leave them run over, they are about 1" too long so this should give me a span of just over 47" including tips. I have replaced the ply doublers with 1/32 ply on the fuse. I like the idea of adding fixed flaps and will use this thanks.

Larry, I have a flite streak artf and did toy with the idea of fitting the fourstroke in it but was put off when I realised I would have to alter the nose. I flew it on a .20 but it needs a good .25 which I shall have to get for this season. The fourstroke does sound great in a model and is a lot quieter in noise sensitive sites. I am going to use a 3oz uniflow clunk in the sky ray. This setup worked well in the Twister but I found exhaust pressure could not be used as there is more goo in  fourstroke exhaust than in a 2stroke.

Thanks for you advice guys. I will bear it in mind while building the Ray.

[Brett Buck]

Larry, I have a flite streak artf and did toy with the idea of fitting the fourstroke in it but was put off when I realised I would have to alter the nose. I flew it on a .20 but it needs a good .25 which I shall have to get for this season.

    If you had a 20FP, I wonder if yours was operating properly. The 20fp has made every ARF or regular Flite Streak I have seen really sit up and talk. Particularly the ARF, which while it's not overly tough, is extremely light. It yanked my 36 oz Skyray around like it was nothing. I wonder also about the "low noise" aspect - if you run the 20FP with the stock muffler we have measured the SPL and it was the same or lower than any of the 4-strokes we tested.

     In short, if a 20FP won't fly the airplane with authority, I think you might have some problem with the engine or the setup. There is plenty of information about the setup I use (and after a lot of work, think is the ideal for the engine) with the search button on here or SSW. Or send me a PM or email.

    Brett

[proparc]

This is one I can personally weigh-in on. Flew Larry Renger's Saito 30 Flitestreak. Gave me all I could handle!! Same hard jump from horizontal as the big 4 strokes.