Skyray 35

[Duke.Johnson]

Hope someone can help.  My teenage son bought a Skyray 35 kit and is about ready to drill the motor mounts.  He has a OS .25 FP I thought we would use, but it is built out of lite-ply.  I like these engines but I'm worried if it has enoughpower for this kit.  He's just learning the pattern and this is for that purpose.  Is it enough power?

Thanks guys.

[Steven Kientz]

There are several articles on the forum about engines  for the Skyray. Many use the Os fp 20, although those have balsa ribs replacing the originals. I getting ready to build 3 using .25fsr and 25fp for power. Should be plenty of power, make sure to use the correct prop for your setup.

Steve

[Paul Taylor]

Yup it will work just fine.
And don't worry should he lawn dart it. Glue it up and go fly.
Good trainer.

[Bootlegger]

 Something else you might consider is 57'-58" lines in the .012 diameter, use a 9x4 9x5 prop and turn about 10,500-11,500 RPM.
  Make a pattern of ALL the parts for repairs, and keep the plans..
  Good luck, and keep us posted as to your progress, don't hesitate to ask questions as we will help all we can...

[Duke.Johnson]

I've heard the .25FP was a one prop engine, I think it was a 9x5?  I'll have him post a picture tonight.

[Tim Wescott]

He has a OS .25 FP I thought we would use, but it is built out of lite-ply.

Actually, that engine is built out of aluminum and steel.   

I have a garage-sale Skyray, and it's a great plane.  It is pretty robust in a crash, and generally easy to repair.  The plane will do the whole pattern nicely on an FP-20; the FP-25 doesn't have as good a reputation as a pattern engine as the FP-20, but it should be perfect for training, and pretty darned good up to intermediate pattern flying if he gets that serious.

As mentioned, if it's not too late you want to take tracings of all the parts, particularly the wing ribs.  And save those plans!  In fact, it wouldn't be a bad idea to start scratch-building the next one as soon as the first one is done -- that way he can fly one while the other one is on the bench getting rebuilt.

[Andrew Hathaway]

Even with the lite ply, the Skyray 35 doesn't build up that heavy, and the 25FP should be more than enough power.  The .20 may be more fool proof and consistent, but there's nothing really wrong with the .25.  The .25 will turn a 10-5 with plenty of authority, but try a few props and use whatever you like best. 

The Skyray 35 works pretty well right out of the box.  There are several easy changes and modifications from the plans that will make it a better plane, but for learning the pattern they aren't really necessary.  If you do build another one, I'd recommend the following changes. 

-Move the pushrod to the inner hole of the bellcrank.  The plans show the pushrod in the outer hole which can make the plane a bit twitchy and harder to fly smooth.
-Ditch the CA EZ hinges.  They're stiff when installed, and the plane will fly better if the control system is free.
-Substitute balsa for all the lite ply in the wing, use full length ribs in place of the half ribs, use 1/4" square spars, and move the splices away from the center of the wing.  The lite ply is heavier, and tends to keep going when the nose hits the ground, breaking the wing.  It also splinters worse than balsa, making for harder repairs.  Moving the splices lessens the chances that the wing will split in the center.  Full length ribs tend to keep the wing from drumming (audible annoying vibration), and in my opinion build a stronger wing.
-Add fixed flaps.  A 3/16" thick balsa flap tapering from about 2" at the root to about 3/4" at the tip increases the wing area, gives the plane a more finished look, and the plane will fly better.
-Substitute a 2 wheel gear, adjustable leadouts, adjustable weight box, to your preference.   

I built two Skyrays right out of the box when I was 16, per the plans right down to the sky blue Monokote and provided decals.  I destroyed both planes many times over the course of that summer, but I did learn the pattern.  Later I started using the above modifications, and the result was a much better plane. 

[Brett Buck]

Hope someone can help.  My teenage son bought a Skyray 35 kit and is about ready to drill the motor mounts.  He has a OS .25 FP I thought we would use, but it is built out of lite-ply.  I like these engines but I'm worried if it has enoughpower for this kit.  He's just learning the pattern and this is for that purpose.  Is it enough power?

Far more than enough. There are extensive discussions of this combination here and on SSW. The 25FP provides far more effective propulsion than any "vintage" 35 or 40, and is far easier to control than any current production 35/36/40. Use a 9-4 or 10-4 APC prop, STOCK MUFFLER,  a Sullivan tank set flat up against the fuselage, set to peak, then back off 5-6 clicks, adjust from there. Use .015x60 lines. Do not use a 2"wide tank, the fuel suction will be marginal.

   There are limitations to the airplane that are not engine-related. I flew mine straight out of the box, plywood ribs and all, and it flew fine. The plywood makes it essentially certain to self-destruct on the first significant head-on crash. Mine hit on the nose and shattered on the first hard hit. I rebuild it with an all-balsa wing, and the performance didn't get a lot better (since even 6 oz of weight is nothing to this engine and the turn is limited by the tail length/deflection, not the wing loading). But it has withstood crashes far better with essentially no damage in at least 30 nose-in power-on crashes over the past 15+ years. 

  I strongly suggest cloning a second, third, or even fourth airplane out of balsa (as described in many places in the archives here and on SSW), finshing them, getting a bunch of spare props, and taking them all to the field for practice sessions. Crash one, get the next one off the stack, put the engine on it, a new prop, and keep going.

    Brett

[Brett Buck]

I've heard the .25FP was a one prop engine, I think it was a 9x5?  I'll have him post a picture tonight.

  It will handle a wide array of props. I have even seen people running 10-4 3-blades on the 20, and it worked pretty well. You can't melt it.

   But 5" of pitch is WAY too much. Running as intended that will pull the airplane *far too quickly* to be easily flown. Even 4" is marginally excessive, but there's nothing between there and 3" commonly available.

   The 20FP works best, by far, with the 9-4 APC. The 25 works OK with a 9-4, a 10-4 APC, a 9-4 or 10-4 Tornado, and is even OK with a 10-4 Tornado. No real problems with a 11-4 but unless you are at sea level this might lead to fuel suction issues.

    Brett

[MikeyPratt]

Hope someone can help.  My teenage son bought a Skyray 35 kit and is about ready to drill the motor mounts.  He has a OS .25 FP I thought we would use, but it is built out of lite-ply.  I like these engines but I'm worried if it has enoughpower for this kit.  He's just learning the pattern and this is for that purpose.  Is it enough power?

Thanks guys.

Hi Duke,
The OS .25 FP will work out just fine in the Shyray 35.  Brett and others are correct about the prop size for this engine just use the 10" X 4" to slow it down a little.

Later,
Mikey

[Dan McEntee]

    HEY MIKEY!!!!! Good to hear from you!!!! I like the APC 10-4 for the FP and LA .25s if the plane has any appreciable weight or large draggy airframe. I had a LA and an FP.25 on my P-Force for years. it weighed 42 ounces and while it was just at the ragged edge of power, I did pretty well with it. Use the stock muffler and either the APC 9-4,9-5, 10-4 depending on speed needed and have fun.Use good fuel with at least half castor in it and 10 to 15% nitro. I don't have a flyable Skyray right now and need to remedy that, and a new Ringmaster also, and I'll probably have one of the two OS .25s on each.
   Type at you later,
    Dan McEntee

[ron young]

   Hi all
I am building my first one of these as well ,i looked on tower hobbies and dont see these engines are they out of production? the only source used e-bay?I sure wish the wind would stop blowing.
  Ron

[Paul Smith]

I never use that Liteply for engine mounts.  Replace it with a thinner grade of hard birch aircraft plywood.  And put a balsa pod on the inside for good measure.

[Andrew Tinsley]

Hello Ron,
The FP series of engines has been discontinued for a good few years now. E bay and the small adds here are a good source. You can always put an add in one of the forums. Probably safer than EBay as you will more than likely get a good one. I would go for the Brett Buck tune up and use an FP20 (do a search here and on Stuka Stunt for the BBTU details).
If you want to buy new, then an LA25s is the most popular engine these days (I personally think the small Enyas to be a better engine), however the LA25s is cheap and readily available.

Regards,

Andrew.

[ron young]

  Thanks Andrew i will look further at that i appreciate the input
Ron

[Tim Wescott]

I've heard the .25FP was a one prop engine, I think it was a 9x5?

You might be thinking of the FP20 with the E2030 muffler, which runs just perfectly all the time on a 9-4 APC.

[Brett Buck]

. I would go for the Brett Buck tune up and use an FP20 (do a search here and on Stuka Stunt for the BBTU details).

   Note that there is no such thing as "tuning up" a 20FP. The term BBTU was used by The Dirt to describe it, mostly because no one can believe the reality.

   To run the 20FP the way I suggest, you take a stock 20FP ABC and change the following items:

     NOTHING

   Use the STOCK venturi/spraybar, do not replace with ST needle, do not replace with smaller venturi, STOCK
   Use the unmodified STOCK muffler that comes in the box. This is CRITICAL.
   DO NOT, repeat, DO NOT add head gaskets. Leave the head on the motor and do not touch it.
   Use a STOCK APC 9-4 propellor. You can knock off the flash at the TE to keep it from slicing your finger,
   Use a NARROW fuel tank like the Sullivan SS-4 with the flat side up against a profile fuselage. Mine is currently set up for suction and muffler pressure because I was willing to expend about 5 minutes putting the tank together. You can also use an inboard tank of any desired width.
   Use any common castor synthetic blend fuel, 10% or higher.
   Use any common stunt glow plug. The one that comes with it is fine, if (and this has never happened to my knowledge) it fails at some point, it is not sensitive to type, any of the normal stunt plugs (Thunderbolt 4-cycle or RC, Glow Devil 300, McCoy, etc). Avoid the obvious problem plugs like the Rossi and any of the Fox plugs.  I use the plugs I removed for maintenance reasons from my big engines, with any taters scraped off.
   Set the engine on the ground by peaking it out lean, then backing off until you get a noticeable drop, maybe 6-8 clicks. If the engine is new beware of heroic fuel consumption that drops rapidly over the first 10 flights. It will run out 4 ounces of fuel in maybe 3-4 minutes on the first run, and the engine will go drastically richer as the flight wears on. Reset it and it will need to be screwed in a lot. That will happen over the first 10 flights or so to a diminishing degree.  It will also tend to quit on inside maneuvers near the end of the pattern on the first few flights. After that the fuel consumption will stabilize and you will need around 2 ounces or a little less to get through a pattern comfortably.

   The 25LA seems to work reliably and much the same, but the current versions are much stronger than the previous and so far it appears to be far too powerful for the Skyray 35 set up per stock. Again, however, FOLLOW THE DIRECTIONS TO THE LETTER aside from the prop selection for flight.

    Brett

[john e. holliday]

Oh no!  A box stock engine for our use wih no engine guru to set it up.   No one will beleive it I am sure.

[Terrence Durrill]

Will the OS Max .20fp iron piston/steel liner version work in this application for the Skyray .35 or Flite Streak?  These engines seem to be much more common than the ABC version of the .20fp and easily obtainable on Ebay....I have two myself and have not run them as of this time.  They are slated to go on two Skyray .35's, one of which is under construction currently. I assume these engines would require more castor than the ABC versions and I do have 2030 stock mufflers.  Any other adjustments needed?        

[dirty dan]

  Note that there is no such thing as "tuning up" a 20FP. The term BBTU was used by The Dirt to describe it, mostly because no one can believe the reality.

    Brett

While it is true that many, many times I have used the term "BBTU," although in my case it is generally "BB-TU," I am nearly certain it was Doug Moon who coined the term. And a good one it is...

Dan

[Sean McEntee]

There is ONE improvement that I dont think I saw.  Replace the NVA and plastic backplate with a metal FP backplate and venturi-mounted NVA.  Have heard of issues with the fuel lines cracking over time, the NVs can be hard to set,  and rear-mounted NVAs tend to be harder to prime and choke, given the bit of extra plumbing.  Other then that, a stock-as-a-rock 25LA is an awesome combo.  I flown the aforementioned Primary Force/stock 25LA/APC 10x4 combination, and took it from advanced to expert.  Also have one in my "Frisky Pete" Old Timer (allot of folks think its an FP cause it aint blue) and it runs fantastic with the previously mentioned substitutions. 

[Paul Smith]

Oh no!  A box stock engine for our use wih no engine guru to set it up.   No one will beleive it I am sure.

The only catch is that the recommended engine is off the market & those that have 'em aren't selling.

[Brett Buck]

The only catch is that the recommended engine is off the market & those that have 'em aren't selling.

    Any similar small engine like that will work, maybe not as perfectly, but pretty good. 25LA, for example, and I think I got them on a special for something like $40 a piece.

    Brett

[Michael Alurac]

As a recent beginner or retread myself I've had a lot of fun with my kit Skyray entering back into the CL hobby after a 30+ year hiatus. Here are some pics of the Sig kit Skyray I built to get my wings back on, the demise of the kit Skyray and the rise from the toothpicks (ashes) scratch built Skyray. Rebuilt with balsa ribs and lighter wood throughout this has become one of my favorite flyers while relearning this sport. Using an old Enya 35 square venturi on crankcase pressure, a 4oz. Sullivan clunk tank with a cut and balanced Tornado 8.5 x 7 prop I get this baby to fly the beginner stunt pattern with an easily achieved 2-4 break using the stock Enya NVA. So from a beginners perspective this has been a very good choice for me to get my wings back on. That's my story and I'm sticking to it!

Mike "Alley" Alurac