Yak-9/OS 15 FP

[Mike Ferguson]

I'm getting started on building a Brodak Yak-9 ... was trying to figure out the best motor to power it.

Would a OS 15 FP have enough oomph for the job, or would something a little bigger be better?

[Terrence Durrill]

Mike,

 

        The .15FP will probably fly the Yak O.K., however, I prefer a little more engine for that plane.  I have a Sterling Yak-9 that I first flew in the early 1990's with a Fox .35 stunt and it flew great...........plenty of power.  Since then I have also flown the Yak with a 4 bolt backplate Fox .25 and an older Fox .25 stunt.  The Brodak kit is patterned after the long extinct Sterling kit from the 1950's, 60's and 70's.  I built this model with working flaps, which I believe is the way to go with the S-3 Yak-9.  In the future I plan to fly it with a K&B Torpedo .29 green head and a K&B Torpedo .19 green head.  These are all traditional engines that have been used on the Yak-9 design over the years and I expect great results here as well.  The Yak-9 from Sterling is one of my favorite sport planes and in fact, I have 5 more Yak-9 kits on the shelf, waiting to be built and flown.  My current Yak is covered with white Monokote on the wings and Hobbypoxy epoxy white on the fuselage which really makes those red stars stand out.  You will enjoy your Yak-9.
                          TDurrill          

[peabody]

Hi Mike....
I have a period correct (well....almost) VECO .19 that would be just the ticket, if built light.....
Let me know?
Have fun!
Peabody

[john e. holliday]

If all you want to do is fly level the .15 might work.  Or you can put it on short lines.

[Dalton Hammett]

Terrence -  Thats the way I like that plane also - have one I'm going to put a GH .32 on, my favorite of the Torpedos.   Have you ever used one of the .29S models,  I have one I've not used and wondered if it really is any better preformer than the regular .29 ??

Mike - I would go with the .29 - .35 size engine to have fun with it.  A modern .25 would likely do well but I prefer the larger engine as well as a period engine.   The old McCoy RH engines are pretty plentyfull also.

Dalton H.

[Terrence Durrill]

Dalton,

    I do have two K&B Torpedo .32's.....one silver head and one greenhead.  They are the same engine with different colored heads, which will not effect performance terribly.  I also have a K&B Torpedo .29S which I have never run.  I have heard that they use a lot of fuel compared to the regular .29 greenhead.  I am mounting it on my Sassy Saucer, which I started in 1987 and am still trying to get finished.   It is ready to cover and I want to get some Darma silk to use on this plane.  I can't tell you how the 29S compares to the regular .29 greenhead, but I used to run regular .29 greenheads on Sterling S-1 Ringmasters decades ago and they provided plenty of power for those planes.............TDurrill      

[Dalton Hammett]

Terrance
    Thanks for the answer.  I know where your comming from,  I have a Chief I started about then also and it's just about ready for papering - next year maybe !!!!!!!

Dalton H.

[Bill Little]

HI Terrence,

I would go with a .20FP, and that would take care of things.    Use the BBTU on the .20FP and it will fly it fine.  A much easier to work with set up than a vintage engine.

Build it reasonable light, and have a ball.  My new OTS Yak 9 has a Veco .19BB, and it was *plans built* using light wood.  I know it will fly really good, and I did not use the flaps.  It doesn't really seem to need them, especially for OTS.

Mongo

[Mike Ferguson]

HI Terrence,

I would go with a .20FP, and that would take care of things.    Use the BBTU on the .20FP and it will fly it fine.  A much easier to work with set up than a vintage engine.

Build it reasonable light, and have a ball.  My new OTS Yak 9 has a Veco .19BB, and it was *plans built* using light wood.  I know it will fly really good, and I did not use the flaps.  It doesn't really seem to need them, especially for OTS.

Mongo

Thanks Bill!  Will probably go with the 20FP then. I was basically thinking of running the 15FP with the BBTU set-up, but didn't know if it would have the guts to do the job.

Rich, I'll let you know when I'm drilling motor mounts ... may make it so I can put a "classic" motor in it as well as something more modern.

[Peter Ferguson]

Mike, I have your 20fp sitting idle and a .25LA, your choice and they are in the mail. Haynes tank and a TT prop works well. I'll send the pkg mon and I'll come out in Sept to see it fly.

[mike hartung]

I just test flew my Brodak Yak-9 last week with an OS LA .25 and it worked good. I made the mistake of using a 4oz. tank and I filled it!!! The engine only needs 2.5oz to 3oz. I was kind of a pooped old man after about 8 to 10min. on the 4ozs. I built mine with flaps, and I am waiting for the smaller tanks to come before any more flying.

[Bill Little]

HI Mike H.,

I am sure the LA 25 is a good set up in the Yak 9!  They are a very easy to work with engine.  I use a touch over 2 oz. in my .20FPs, and haven't used *my* LA 25 yet, so the run time is good to know, thanks.

I am going to use mine in OTS one day so the lack of flaps gets me 10 extra points (as if that would help! LOL!!).

If it was an old Sterling kit, I would be worried since it has a small wing and the old kits usually built HEAVY.

Big Bear

[john e. holliday]

Just need to fly a little faster.   

[Larry Fernandez]

If all you want to do is fly level the .15 might work.  Or you can put it on short lines.

Its funny you say that Doc.

A couple of years back  I told everyone I was going to build a Ringmaster and power it with an FP .15
Same thing was said, "Should fly fine if you just want to fly in circles"

That plane won Old Time at the Golden State Meet.

Larry Buttafucco Stunt Team

[Phil Spillman]

Hi Mike, I agree with all suggestions made heretofore! Back in the day I must have had 4 or more Yaks from Sterling and now there's another one just begging to be finished in my new building room! However there is two P-51's from Sterling which I have been flying, one since 1974 and the other since 1992! One is powered by an FP .20 the other by an FP .25! Both are flapped and both never flew this well back in the day with Fox 35's and K&B's of all varieties! I must also say that both have had LA .25's mounted and that engine flew every bit as well as either of the others did!

What the modern engines really accomplished was to make the wing finall work as it should have all along! Others prefer 9 X 5's (MAS) props but I enjoy the (9 X 4) APC prop for these engines, both LA and FP. AS to tank size the 2.5 to 3 ounce varieties are best if you don't want to still flying when everybody else goes home! In addition I prefer muffler pressure and 10-11-11 formula fuel.

My P-51 has been rendered in "B" foremat and was the basis for my first sortie into Mono Coat covering. I did the entire plane including the fuselage and hinges in the then "new" flat colors; Olive Drab top and Polar Gray bottom! The MonoCoat hinges result in a completely sealed hinge line for all surfaces, going all across the full surface, which makes the controls much more positive and effective! These a re truly fun projects and my just score you a prize or two depending on what skill class you fly in if you are a competitive type o/w they are at the top of the chart for pounds of fun derived for penny of capital invested!
Tally Ho,

Phil Spillman
T 

[Terrence Durrill]

Thanks Phil, for the information.  I have two OS Max .20fp's and one OS Max .25la which I just may have to try out on the Yak-9 as well.  My 20fp's are the older iron piston types, not the newer ones recommended by Brett Buck and "da dirt".  I have not run them yet, but I believe they should perform O.K. on this plane...TDurrill 

[Mike Ferguson]

Mike, I have your 20fp sitting idle and a .25LA, your choice and they are in the mail. Haynes tank and a TT prop works well. I'll send the pkg mon and I'll come out in Sept to see it fly.

Send the 20FP on back to the wilds of New Jersey, then. And thanks!

I'll get the Yak ready for September. 

[Peter Ferguson]

Its nicely broken in. I'll put together a care package.

[Phil Spillman]

Hi Terrance, you are most welcome for whatever it may be worth. As to the iron pistons vs. the others not to worry! Several of my FP's have been the iron pistoned varieties and they ran just fine perhaps a bit better! My fuels always have some Castor oil in the mix and so I am not concerned in the least that I may be putting my engines at risk! I know for a fact the my iron pistons have been runevery bit as thoroughly as the aluminium ones with no discernable ware noted! I do use muffler pressure and the tanks are mounted abut 1/4 to 3/8 inches above the center of the venturi insert. With this arrangement I noticed no difference from upright to inverted!

I do use for the most part idle bar plugs. Thunderbolt long is my variety of choice!

Tally Ho!

Phil Spillman