News:


  • July 13, 2024, 06:39:14 AM

Login with username, password and session length

Author Topic: OS FS 26 Surpass - Fuel Tank Setup  (Read 31200 times)

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
OS FS 26 Surpass - Fuel Tank Setup
« on: December 19, 2022, 04:43:26 PM »
I recently acquired a new OS 26 Surpass 4-stroke engine. My plan is to use it on a profile CL model in the future, maybe a warbird flown for sport and stunt.

My question relates to fuel tank type and related setup for this engine on a profile model.

1. What tank design is considered optimum for a CL application. Uniflow wide wedge tank? Clunk tank? Other?

2. Tank height location in relation to the engine on a profile setup?

Also, will the 26s pull say a typical 40" wing profile model? I believe it is less powerful than an OS 25LA. Any model suggestions would be appreciated.

Thanks in advance.

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #1 on: December 20, 2022, 07:13:51 AM »
Colin,
The OS 26 with pull ships like a strong FOX 35, 45 - 48" span, 40 oz ish weight. I had mine in a TF Tutor (original version) and ran 10 x6 prop, 10% nitro, 22% total oil (mostly synthetic). From my notes you want a wide blade prop (like an RSM or BBYO) around 9900 rpm. I needed 2 3/4oz of fuel for the PA pattern. Use a tank tall and skinny clunk works with the fuel pickup tube being 5/32" OD and drill out the cluck to 5/32" (this gives better fuel draw), use large fuel line and wire onto fuel nipple. Set the centerline of the tank inline with the center of the carb/venturi to start and adjust up/down to get equal lap times. Set up vent for standard vents (not uniflow) and muffler pressure.

Best,   DennisT
« Last Edit: May 01, 2023, 02:52:07 PM by Dennis Toth »

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #2 on: December 21, 2022, 08:26:53 AM »
Thx Dennis. 4-stokes are new to me so I have much to learn.

Can you please help me understand why your recommendation for a 'tall and skinny' type tank. And standard vent vs a uniflow design. Also, I have been reading up a bit and some mention to use a clunk tank, but don't explain why.

A guy I know has this particular tank (see attachment) on a profile model w/ a Magnum 30 four stoke. It is a standard vent design (not a clunk design) and seems to work fine in the air.

If a clunk tank is the way to go, I looked at Sullivan and Dubro and don't see a 'tall & skinny' design per se.

Thx again for your help.


Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #3 on: December 21, 2022, 09:06:52 AM »
Colin,
The tall tank is just the regular cluck tank stood on its side. This minimizes change in fuel head being about 1 1/4Ē vs. 2 1/4Ē if set on its bottom. 4strokes donít have as much pumping fuel draw as higher rpm 2 strokes thatís why they usually run better on conventional venting. One tip is to use 5/32Ē fuel pickup tube (drill out the cluck too) and larger fuel tube .

Best,  DennisT

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #4 on: December 21, 2022, 02:36:19 PM »
Thx much
Dubro makes a 2oz rectangular tank that I can try.

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #5 on: December 23, 2022, 08:59:11 AM »
Colin,
Change out the fuel pickup line to 5/32" (copper is best for nitro) and drill the cluck tip to same.

Best,    DennisT
« Last Edit: May 01, 2023, 02:54:35 PM by Dennis Toth »

Online Robert Zambelli

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2937
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #6 on: December 23, 2022, 02:26:51 PM »
I have a number of planes flying with the Surpass 26, hundreds of flights.
One plane flys with THREE of them.
Iíve had very good results with a plain VECO two-ounce metal tank, non-uniflow, over/under venting, no muffler pressure. The engines are profile mounted.
Up to now, Iíve been using Brodak 10/23, 50-50 castor/synthetic but I plan to mix up some 20/20, 18/2 synthetic/castor to try out.
The Surpass 26 is a very good four cycle engine, requiring minimal fussing and maintenance.
The OS four cycle plug works perfectly.
Best of luck!!
Bob Z.

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #7 on: December 23, 2022, 06:19:48 PM »
Colin,
Due change out the fuel pickup line to 5/32" (copper is best for nitro) and drill the cluck tip to same.

Best,    DennisT

Thx Dennis, will do!

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #8 on: December 23, 2022, 06:38:48 PM »
I have a number of planes flying with the Surpass 26, hundreds of flights.
One plane flys with THREE of them.
Iíve had very good results with a plain VECO two-ounce metal tank, non-uniflow, over/under venting, no muffler pressure. The engines are profile mounted.
Up to now, Iíve been using Brodak 10/23, 50-50 castor/synthetic but I plan to mix up some 20/20, 18/2 synthetic/castor to try out.
The Surpass 26 is a very good four cycle engine, requiring minimal fussing and maintenance.
The OS four cycle plug works perfectly.
Best of luck!!
Bob Z.

Thx for the info Bob, much appreciated.

4-stokes are new to me so I have lots to learn. I just like the sound and plan to use the 26s on a future warbird model. Maybe a Brodak Yak 9. Might even set it up for 3-line w/ throttle control.

I normally use Brodak 5 & 10/23 fuel. So, I will already have a bunch of the correct fuel for the 26s.

A friend of mine has a Magnum 30 four-stroke on a Wildcat warbird model and uses a metal profile standard vent tank. Not sure if he uses muffler pressure. In any event his model runs great. I will play around w/ the various options to see what works best.

A few experienced members recommend a clunk tank for a 4-stroke, but don't really explain why. My guess is that they fly the pattern and want the clunk design for that purpose. But if one flies sport (and a few basic stunts), not sure it makes any real difference. Others have said a metal non-clunk works fine. I have both and will experiment for best operation.

And I do have the OS F glow plug.

I am excited to get my feet wet w/ a 4-stroke on a CL model!!

Online Robert Zambelli

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2937
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #9 on: December 23, 2022, 07:28:27 PM »
I used one of mine in a Sterling Mustang.
Flew great, took home many trophies in OTS and classic stunt.
I once beat a Super Tiger 60 powered Cardinal with the Mustang.

Bob Z.

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #10 on: December 23, 2022, 08:23:19 PM »
The Brodak Yak 9 (40" wing) is about the same size as the Sterling Mustang, so should work well for the 26s.

I recently retired and have picked up the CL hobby again after some 50+ years. (built and flew 1/2a's as a kid in Hawaii)

Not sure any competition is in my future, but I am working on practicing the pattern. So far, my squares are not very 'square', and my overhead 8's look more like 7's. But I am working on it.

Fun stuff for sure!!

Online Robert Zambelli

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2937
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #11 on: December 24, 2022, 07:16:14 AM »
Colin:
Donít worry about competition - just go out and get as much enjoyment out of the sport as you can.
If you do decide to compete, you can take advantage of one of the four skill classes.
The important thing is to have fun!

And, keep us posted on your progress with the 4-stroke engines.
Keep in mind that the Sterling Mustang and Yak 9 are very close in performance.
Build them light and if you want, make the flaps non-moveable. Iíve done them both ways and couldnít tell the difference.
Bob Z.

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #12 on: December 24, 2022, 11:30:29 AM »
Colin,
Due change out the fuel pickup line to 5/32" (copper is best for nitro) and drill the cluck tip to same.

Best,    DennisT

Dennis, I was putting together the small Dubro 2 oz rectangular clunk tank and noticed an issue. Since the tank overall length is so short, the short piece of flex fuel tubing inside the tank between the stopper and clunk is too stiff (being so short) where the clunk does not drop to the bottom (or top) of the tank.

Is there a 'trick' for these small clunk tanks?  (Some type of tubing that is more flexible than the normal silicon fuel tubing we get from SIG or Brodak? Surgical tubing maybe, but can surgical tubing be used with glow fuel?)

I guess I could use a larger clunk tank and just not fill it full for the OS 26s, but don't really want to.

Or just use a 2 oz standard vent metal tank (no clunk).

Thoughts welcome.
Thanks

 

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #13 on: December 24, 2022, 12:11:26 PM »
Colin.
For the short tanks the Sulllvan tubing is very thin walled and flexible but surgical tubing will be more flexible for the 2oz tank. Other option could be a round tank with a fixed copper tube and conventional vent pointed to the inside of the circle side of the tank, just make sure you mount the air side of the vent above the tank and on the inboard side of the fuse (this gives clean airflow to the vent).

Best,    DennisT
« Last Edit: November 24, 2023, 07:50:36 PM by Dennis Toth »

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #14 on: December 24, 2022, 03:42:44 PM »
Colin.
For the short tanks the Sulllvan tubing is very thin walled and flexible but surgical tubing will be more flexible for the 2oz tank. Other option could be a round tank with a fixed copper tube and conventional vent pointed to the inside of the circle side of the tank, just make sure you mount the air side of the vent about the tank and on the inboard side of the fuse (this gives clean airflow to the vent).

Best,    DennisT

Dennis, do you know if the Sullivan silicon tubing is more flexible than the Dubro provided tube that came w/ the tank? I have some Brodak pink tube, but it is just as stiff as the Dubro product.

And I know surgical tubing was used years ago for glow fuels, but now pretty much replaced w/ silicon. The surgical tubing does not have to be hot-fuel proof in this case, but how does it hold up (chemically) to typical nitro glow fuels. 


Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #15 on: December 25, 2022, 09:08:22 AM »
Colin,
Yes the Sullivan tubing is thinner walled and more flexible than the Dubro. Again use the 5/32" copper tube and drill out the cluck.

Best,   DennisT

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #16 on: December 25, 2022, 09:36:57 AM »
Colin,
Yes the Sullivan tubing is thinner walled and more flexible than the Dubro. Again use the 5/32" copper tube and drill out the cluck.

Best,   DennisT

Thx Dennis
Merry Christmas !!

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #17 on: May 01, 2023, 01:50:11 PM »
I have a number of planes flying with the Surpass 26, hundreds of flights.
One plane flys with THREE of them.
Iíve had very good results with a plain VECO two-ounce metal tank, non-uniflow, over/under venting, no muffler pressure. The engines are profile mounted.
Up to now, Iíve been using Brodak 10/23, 50-50 castor/synthetic but I plan to mix up some 20/20, 18/2 synthetic/castor to try out.
The Surpass 26 is a very good four cycle engine, requiring minimal fussing and maintenance.
The OS four cycle plug works perfectly.
Best of luck!!
Bob Z.

I still have a question in the OS 26FS relating to fuel pressure (muffler pressure) versus standard over/under venting for a full speed CL application. A few have said they use no muffler pressure. However, the FS26 owner's manual shows the recommended fuel system set up and shows muffler pressure applied to the fuel tank. It seems muffler pressure just enhances fuel draw.

I plan to set up the carb to be about 1/3 open to start and allow for some brief warm up. Then ground adjust to desired full speed before takeoff.

The 26FS is basically designed as an R/C engine. Maybe fuel pressure not needed for a fixed speed CL application?

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #18 on: May 01, 2023, 03:06:02 PM »
Colin,
You can try it both ways but for the no pressure option you need to get the vent line in the free air stream above the fuse sides either off the back engine bolt or through the fuse and up about 3/16" above the fuse side profile. I used the pressure and was very satisfied with the run. Attached is a photo of the vent I use on a 2 stroke powered Ringmaster. You can see it is off the back bolt, just a small piece of copper or brass tube.

As for the 1/3 carb to warm up that is not necessary. These 4 Strokes warmup quick, most people wire the carb fully open and adjust the engine to a solid lean run. Adjust lap time speed with pitch, the 10x6 is a good match on 10 - 15%N fuel.

Best,   DennisT

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #19 on: May 02, 2023, 11:43:44 AM »
Thanks Dennis.

Concerning the speed adjustment, I got this idea from a flying buddy who has a few CL 4-stroke models. I installed a simple aluminum gear (a part from a hobby shop intended for an RC car) on the carb. The gear teeth are in contact w/ the choke rod and keep the carb where you set it. So I can set the carb partially open to start. Then rotate gear to full open before takeoff. My opinion only, and maybe not necessary as you say, but it is not a bad idea to start at a lower speed and allow for some brief warmup. With all the FS moving parts (compared to 2-stroke) a brief low speed warmup can't hurt.

Online Robert Zambelli

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2937
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #20 on: May 02, 2023, 03:52:27 PM »
Very good idea!!!   y1  y1  y1
But, here's something I've found with some of the Surpass engines.
The clearance between the moving throttle drum (valve) and the bore can vary quite a bit.
If this clearance gets too large, you will get some erratic runs due to air leakage.
What I do is remove the throttle arm and install a washer that is coated with RTV.
Tightening the screw will seal any leak and hold the throttle drum in place - wide open.
Note that I've owned around twenty OS 20 and 26 four cycle engines and although rare, this situation does occasionally occur.
I've not seen it in the larger engines.
I've NEVER witnessed it in a SAITO.

Bob Z.

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6960
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #21 on: May 02, 2023, 10:31:38 PM »
  To add to what Bob is saying, an R/C carb that is wide open is way bigger than what a restrictor venturi with a spray bar through it would be and add to that all the clearance around the throttle barrel passing air. Closing down the throttle decreases the opening and adds some choke to help with fuel draw, and 4 strokes are all about fuel draw. I would test it at about 1/3 closed, and run muffler pressure. In my limited experience with both OS and Saito four strokes, this has always worked the best for me. It's more or less the "Bob Reeves" philosophy or running a 4 stroke engine and has worked pretty well for me. I applied what I learned running and flying my Saito .56 to an OS.70 and it responded the same as the Saito did. I had to use the carb closed off, as no one made any bolt on venturi for C'L stunt for it. Flying four strokes has been fun and is a viable power plant, and I hope to get my Top Flite Score recovered soon and get back to it, and maybe a couple of other models in the future, but I haven't sold off any of my 2 stroke engines just yet!
  Type at you later,
   Dan McEntee
 
   
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #22 on: May 03, 2023, 09:30:37 AM »
Dan, not sure I fully understand. Are you saying you have had good luck with 4-strokes (on a CL application) with the throttle maybe 66% open (to simulate a venturi restriction), then adjust the needle for desired full speed?

Or if the engine is not running well at full throttle (due to air leakage), test and start to close the throttle to see if the engine performance improves?

Thanks in a advance.

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6960
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #23 on: May 03, 2023, 03:19:35 PM »
Dan, not sure I fully understand. Are you saying you have had good luck with 4-strokes (on a CL application) with the throttle maybe 66% open (to simulate a venturi restriction), then adjust the needle for desired full speed?

Or if the engine is not running well at full throttle (due to air leakage), test and start to close the throttle to see if the engine performance improves?

Thanks in a advance.

   That is exactly correct. Search out threads on here by Bob Reeves. He and some others did a lot of research and experiments into this. You could also go to the Tulsa Gluedobbers web site and a lot of it is posted there. Bob has since passed away but he left a lot of information behind. Bob advocated for the low RPM/high pitch prop method of running 4 strokes. If you happen to have a C/L venturi on an engine, he came up with the idea t add a screw to the throat of the venturi that goes in on one side only, and by running the screw in and out, you effectively change the venturi choke area. Running it in makes it smaller and draws more fuel, out makes it bigger and draws more air. Not really a new idea, the speed limit combat guys have been doing the same thing for a long time to get their engines to run a constant speed.. As you turn the screw in, you turn the needle in next to get a max RPM setting just above 8000 RPM. That is what he said to do for a Saito 56/62. props are in the 6 and 7 inch pitch range. If the weather gets warmer, you can screw the blocking screw out just a bit to let more air in and reset the needle. When it gets cold out,  you do the opposite, screw in in to let in less air and reset the needle. It will kind of go against everything you already know about engines and props for 2 strokes, but it works. With an R/C carb, the barrel takes the place of the screw. Just play with it and get familiar with it. For a 4 stroke that small, i don't know if you need a new RPM range or not, but just experiment, go by lap times and line tension. before you try any maneuvers. The engine might not sound like it will pull your hat off your head, but just ignore that and go by lap time and feel. This set up with muffler pressure will make the engine run very consistently where ever it is flying. You will have to get used to that and if you have been flying 2 strokes for any length of time it will sound foreign to you.   The 4 stroke is a different animal, and resist all temptation to run it like a two stroke. This low RPM set up lets the engine get plenty of fuel, and thus it runs cooler. I have run several gallons of fuel through my Score and Saito .56 and all of the chrome is still shiny. I ran all of this by Gilbert Berringer from France. He is one of the top stunt pilots in Europe and helped bring the 4 stroke engine along. He has a large manufacturing company that makes aircraft wheels and brake systems, and comes to Oshkosh every year, along with Sun and Fun in Florida during the winter. He flew my Score several times and was impressed by it. He sets his engines up with a very small venturi to start with, no bigger that 6mm, he told me, and when you put a spray bar through that, the choke area is pretty small. I run Powermaster YS-20/20 for the most part, and it's getting pricey now, but i only use about 3.5 ounces per flight, so it lasts a while. Try some of the Powermaster synthetic blends in the 15% range. It would not hurt to add some extra synthetic oil to get the total oil content up closer to 20% like the YS blend. I have been trying not to add any castor, as there are a LOT more and smaller moving parts in these engines, and even smaller yet for your .26. If it sets up and runs the lower ROM ok, it might not be necessary. It will take a lot of attention on your part as you go through the motions. Everything from starting them to picking props and setting the needle will be different and again, the big thing is DO NOT run it like a two stroke!! The closest thing I have to your engine is a Saito Black Knight .30 but I have yet to pick a model for it.
  Type at you later,
   Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #24 on: May 03, 2023, 05:29:56 PM »
Thx Dan. I have a lot to learn about 4-strokes and this is very helpful.

I decided to pick up the OS 26 FS since I got it at a very good price. It is for a future model. I am thinking about a profile Yak 9 warbird.

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #25 on: May 04, 2023, 03:40:07 PM »
Colin,
Dan gave some very good information. Here is an engine review of the OS 26FS Surpass (http://sceptreflight.com/Model%20Engine%20Tests/OS%20FS-26%20Surpass.html). I like to run mine in the 9500rpm range and use a higher pitch (like 7") with a wide blade, diameter around 10". The point Dan made about the sound is important. With the muffler it is like flying electric, but the note is a little flat compared to 2 stroke (think Harley vs, Yamaha). You will notice that you may be flying faster lap times with the 4 stroke but it will seem like it is slower because of the sound.

The Yak is a very good ship for this size engine.

Best,    DennisT
« Last Edit: July 06, 2023, 06:17:14 PM by Dennis Toth »

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #26 on: May 31, 2023, 12:18:53 PM »
I used one of mine in a Sterling Mustang.
Flew great, took home many trophies in OTS and classic stunt.
I once beat a Super Tiger 60 powered Cardinal with the Mustang.

Bob Z.

On your Sterling Mustang w/ OS 26FS, what prop do you run, and corresponding ground rpm?
The Brodak Yak 9 is about the same size model. And I plan to build the YAK-9 w/ flaps.

I have available:
MAS 10-4
MAS 10-5
MAS 10-6
MAS 10-7
APC 10-5
APC 10-6
BYO 10-5
BYO 10-6

Thanks in Advance
« Last Edit: May 31, 2023, 12:47:31 PM by Colin McRae »

Online Robert Zambelli

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2937
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #27 on: July 06, 2023, 12:20:42 PM »
Colin: Actually, I've had very good results with a Master Airscrew 9-6 plastic as well as a 10-6 cut down to 9 1/2.

Also, if you can find some, the old Top Flite 9-6 wide blade wooden props work very well.

However, it's best to experiment - try some of the ones you already have and pick the one that best suits your flying style.
Generally, I prefer to use props with at least a 6 pitch.

Bob Z.

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #28 on: July 06, 2023, 05:21:53 PM »
Thx Bob

The 6 pitch makes sense for the 4-stroke since typically at lower rpm.

I typically run a 4 pitch on my more modern 2-stroke engines. But a 10-6 on my Fox & McCoy 35's. The Fox/McCoy are typically running around 9,000 rpm. OS's more like 11,000-13,000 rpm.

I have all the props you suggest for the 26FS and will indeed experiment. Have not even bought the kit yet for the 26 FS but I plan on a Brodak Yak-9 warbird when the time comes. I am currently completing a SIG Skyray 35 kit. The Yak will be next up in my shop.

I do have a Brodak Shark 402 with OS 25LA. The 26FS has the same mounting bolt pattern so I just might put the 26FS on the Shark to get my 'feet wet' w/ a 4-stroke on a profile model. 

One additional question. A few on this post recommend using a standard vent fuel tank and no muffler pressure. State reason that 4-strokes don't have great fuel draw. But it seems to me muffler pressure just helps fuel draw. Plus, the stock engine and owner's manual show muffler pressure. Not sure I understand what is going on.

Comments are welcome.
« Last Edit: July 06, 2023, 06:17:02 PM by Colin McRae »

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #29 on: August 01, 2023, 06:27:27 PM »
I used one of mine in a Sterling Mustang.
Flew great, took home many trophies in OTS and classic stunt.
I once beat a Super Tiger 60 powered Cardinal with the Mustang.

Bob Z.

Bob, just curious. I am thinking ahead on my future Brodak Yak 9 build w/ OS 26FS.

On your Sterling Mustang w/ OS 26FS, what trick(s) did you use to manage the CG with the heavier four stroke engine? The kit is probably designed around a 25LA or FP. With stock muffler, the 25LA is around 8 oz and the 26FS around 10 oz.

Did you move the engine back a bit, or just add lead in the tail as needed?

Thanks in advance.

Online Robert Zambelli

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2937
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #30 on: August 01, 2023, 07:50:10 PM »
Hi, Colin.
As I recall, my Sterling Mustang weighed around 27 ounces.
Rather than adding tailweight, I shortened the nose by an inch or so.
I made a few other modifications.
Hollowed out the fuselage and leading edge.
Put one inch of dihedral in the wing.
Installed a wing mounted landing gear.
Put the pushrod inside the fuselage.
It looked fantastic and flew great!
I did not use muffler pressure.
Open exhaust, metal tank with over/under venting.
That little engine never missed a beat.
Bob Z.


Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #31 on: August 18, 2023, 12:16:40 PM »
Thanks Bob

Have not purchased the Brodak Yak-9 kit as yet but am thinking and planning ahead.

Your Mustang and the Yak are nearly identical size models. Your Mustang is built pretty light. My build skills are somewhat limiting, and I probably can't build as light as you. My Yak will be pretty much stock-built. If I were to guess, the Yak will come in somewhere in the 30-32 oz range with corresponding wing loading around 13.4-14.3.

One question I have is whether or not to build the model with flaps. You had mentioned the Mustang flies great either way. Considering the heavier model with OS 26FS (compared to yours), would you suggest flaps or not? Flaps will probably improve flight performance, but also increases drag with corresponding increased power needs.

Thoughts welcome.

Online Robert Zambelli

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2937
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #32 on: August 18, 2023, 08:15:10 PM »
Hi,  Colin.
I really donít have a good answer to your question but even with the additional weight, I suspect that the fixed flaps would work.
Realistically however, itís not that difficult to reduce weight.
Get out your Dremel and a Kutzall carbide burr and start hollowing the lead edge and also taper the fuselage.
Make lightning holes wherever possible.
Round off all sharp corners.
Drill holes in the engine mounts where theyíre hidden in the fuselage.
A little effort will go a long way in reducing weight.
Bob Z.

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #33 on: November 24, 2023, 08:14:32 PM »
Colin,
Regarding the fixed vs coupled flaps for the Mustang or Yak 9, it depends on what you are building the model for. If you are planning on flying it in Old Time Stunt you can use either, but with the coupled flaps you lose 5 bonus points. If you build it with fixed flaps leave the flaps flat and square at the ends. This is an old Lew Andrews tip, he used on his Barnstomer's. What this is supposed to do is give you the effect of having around 10 degrees of flap as the ship turns through maneuvers. If you decide to go with the coupled flaps set them up for 2:1 elevator to flap. These ships have short tail moments and to much flap deflection will make it turn very slow. Also, you only need +- 20 degrees elevator, much more and the stall like a Ringmaster.

Best,    DennisT

Offline Jeremy Chinn

  • 24 supporter
  • Trade Count: (0)
  • Lieutenant
  • *
  • Posts: 107
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #34 on: December 01, 2023, 07:47:36 PM »
Reading this thread earlier this week inspired me.

I decided to pull the .26FS I had in my collection but had never run (its used and had definitely run before). I broke it most of the way down and cleaned out all of the dried castor and then lubed it back up.

I put it on the test stand, and to my big surprise it actually started on the first flip. I'm running it on some very old 15%, but after warming up and settling in, it ran beautifully. I'm extremely happy with it.

I was running it on a wide blade 10-4 that I happened to have bolted to it and that seemed to be a good prop to run on the stand. Lighting was not good for getting a good reading with the tach, but it is very strong.

I definitely have to build a bird for this engine finally!!!

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #35 on: December 17, 2023, 07:07:14 PM »
Reading this thread earlier this week inspired me.

I decided to pull the .26FS I had in my collection but had never run (its used and had definitely run before). I broke it most of the way down and cleaned out all of the dried castor and then lubed it back up.

I put it on the test stand, and to my big surprise it actually started on the first flip. I'm running it on some very old 15%, but after warming up and settling in, it ran beautifully. I'm extremely happy with it.

I was running it on a wide blade 10-4 that I happened to have bolted to it and that seemed to be a good prop to run on the stand. Lighting was not good for getting a good reading with the tach, but it is very strong.

I definitely have to build a bird for this engine finally!!!

My new OS 26FS Surpass is planned for an OTS Brodak Yak-9. My Yak-9 build is early in the build process.

In preparation I have run my 26FS in my test stand to start the initial break-in process. I have bench-run it on 10 nitro/20% oil. It has started easily and run very well so far. I am excited to finally get some experience with a FS engine on a CL model.

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #36 on: December 18, 2023, 08:49:25 AM »
Coln,
The OS 26 Surpass FS is a great little engine for the YAK 9. One thing for the tank setup, the FS like conventional tank vents NOT uniflow, some have used muffler pressure also. The RC plastic tanks work well, set them to be tall and skinny with the vent line to the top inside corner of the tank and the open end up in the free airstream above the fuse profile (see photo). This gives very consistent runs. Mine likes a 9 1/2" x 6 at about 10K.

Best,   DennisT

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #37 on: December 18, 2023, 11:14:13 AM »
Coln,
The OS 26 Surpass FS is a great little engine for the YAK 9. One thing for the tank setup, the FS like conventional tank vents NOT uniflow, some have used muffler pressure also. The RC plastic tanks work well, set them to be tall and skinny with the vent line to the top inside corner of the tank and the open end up in the free airstream above the fuse profile (see photo). This gives very consistent runs. Mine likes a 9 1/2" x 6 at about 10K.

Best,   DennisT

Dennis, maybe it is just one's terminology, but am a bit confused.

When I think about 'conventional' venting, to me it means simple over/under venting with both vents open during flight. (i.e.:, A tank similar to the old Perfect tanks.) But if muffler pressure is used, one of the vents would be plugged to maintain the pressure. Correct?

And would not a uniflow design tank keep the engine run more consistent? A uniflow tank can be run with or without muffler pressure. (I actually run an oval profile uniflow tank on a Fox 35 with just ram air to the UF vent with the overflow plugged. It runs better with ram air pressure vs muffler pressure.)

Also, others have mentioned that for some reason, a clunk type tank works best for a small FS.

I have all of the above tank designs mentioned. But I am thinking about trying a small Sullivan clunk tank, set up for uniflow, or a metal oval profile uniflow tank, but just using ram air pressure to the UF vent, with OF plugged.

Thoughts welcome

Thanks in advance.

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #38 on: March 12, 2024, 03:27:46 PM »
Since 4-strokes used for CL is relatively new to me I decided to mount an OS 26 FS Surpass on my Brodak Shark 402 as part of a learning process. It was relatively easy on the Shark as the 26 FS has the same engine mount bolt pattern a 25LA. The only significant change was that I needed to raise the fuel tank to work with the 26 FS. I'm currently building a Brodak Yak-9 and going to use the 26 FS on that model when the time comes. This experience should help iron out general engine operational experience as well as some in the air experience on a model.

I am starting out with a 2 oz uniflow fuel tank using exhaust pressure. Fuel will be 10% nitro / 20% oil (68% syn/32% castor)

« Last Edit: March 12, 2024, 05:50:03 PM by Colin McRae »

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #39 on: March 13, 2024, 07:13:18 AM »
Colin,
Sounds good, one thing you might want to experiment with is using an conventionally vented plastic tank. I was able to do the pattern on 2oz but that was 10% nitro fuel. For some reason the 4 strokes like the CV setup better. Tall and skinny works well, could try muffler pressure to the CV vent line. If you do the open CV vent make sure it is up in the free airflow above the fuse side (photo in prior posts in this thread).

I know it is a little hard to go to the CV venting after we have been told how great the Uniflow is all these years but the top guys that use the 4 strokes have proven it out so worth a try.

Best,   DennisT

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #40 on: March 13, 2024, 09:02:42 AM »
Colin,
Sounds good, one thing you might want to experiment with is using an conventionally vented plastic tank. I was able to do the pattern on 2oz but that was 10% nitro fuel. For some reason the 4 strokes like the CV setup better. Tall and skinny works well, could try muffler pressure to the CV vent line. If you do the open CV vent make sure it is up in the free airflow above the fuse side (photo in prior posts in this thread).

I know it is a little hard to go to the CV venting after we have been told how great the Uniflow is all these years but the top guys that use the 4 strokes have proven it out so worth a try.

Best,   DennisT

Thanks Dennis

I can certainly try the CV system as an alternate. My Shark w/ OS 26FS is an experiment so I can find the optimum fuel tank setup for my upcoming Yak-9 project. I can easily try different tank setups on the model to see what works best.

I do understand that CV works great on FS applications. An expert I fly with has an OS 40 FS Surpass on a Doctor and uses CV. Engine run is great. And I did try out the free air vent on my Ringmaster / Fox 35 (uniflow tank w/ free air vent). The Fox runs much better this way. Thanks for the tip.

I run muffler pressure on all of my OS 2-stroke engines. And I am aware of one potential problem. With muffler pressure, the needle is set farther closed compared to CV for the same ground rpm. But if you happen to lose muffler pressure during flight (say a leak develops or a tube comes off), the engine will go very lean even possibly contributing to some engine damage due to lack of sufficient lubrication. I always pre-check my fuel tank setup before a flight and have not experienced this potential issue to date.
« Last Edit: March 13, 2024, 09:55:45 AM by Colin McRae »

Offline Russell Graves

  • Trade Count: (0)
  • Ensign
  • **
  • Posts: 25
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #41 on: March 14, 2024, 08:09:08 PM »
This question is for Dan or Dennis or Robert. This post has been about using the four stroke on a profile plane. I recall reading somewhere that Bob Reeves suggested to mount the four stroke motor in the horizontal position (like a profile plane). What about in a full fuselage stunt plane - have you seen a big difference between mounting the four stroke engine inverted versus horizontal? Just wondering what you think, if it's a big difference or small difference. Thanks.

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6960
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #42 on: March 14, 2024, 10:11:55 PM »
This question is for Dan or Dennis or Robert. This post has been about using the four stroke on a profile plane. I recall reading somewhere that Bob Reeves suggested to mount the four stroke motor in the horizontal position (like a profile plane). What about in a full fuselage stunt plane - have you seen a big difference between mounting the four stroke engine inverted versus horizontal? Just wondering what you think, if it's a big difference or small difference. Thanks.

    I have only used a 4 stroke mounted inverted. But in reading almost everything written on the subject trying to get a satisfactory run, the only thing I recall reading about mounting them horizontally is that it is believed they oil a bit better internally. Nothing about it has anything to do with how it runs. I don't know how to tell if it's oiling better or not. I haven't flown mine in quite a while (it's over due for a recovering) but when I  finally got it squared away using Bob Reeves set ups and using pressure on standard tank venting, I never had any problems and the engine still feels and looks like new to me. It sort of semi protects the cylinder in a pancake crash, only risking the exhaust. If you have any doubts, just go back and reread Bob's post on the forum here or on the Tulsa Gluedobbers web site.
  Type at you later,
  Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #43 on: March 28, 2024, 08:36:06 AM »
Colin,
Sounds good, one thing you might want to experiment with is using an conventionally vented plastic tank. I was able to do the pattern on 2oz but that was 10% nitro fuel. For some reason the 4 strokes like the CV setup better. Tall and skinny works well, could try muffler pressure to the CV vent line. If you do the open CV vent make sure it is up in the free airflow above the fuse side (photo in prior posts in this thread).

I know it is a little hard to go to the CV venting after we have been told how great the Uniflow is all these years but the top guys that use the 4 strokes have proven it out so worth a try.

Best,   DennisT

I did try to put together a small Dubro 2 oz clunk tank for possible use on a 40" wing smaller profile model w/ the OS 26 FS. One of my struggles with the small plastic tank setup is that the clunk tube within the tank is so short that the tubing is not flexible enough such that the clunk does not move freely within the tank. The other issue is that on a smaller profile model there is not enough room to install the tank behind the FS engine. I would have to move the tank to the inboard side of the fuselage. But this makes the fuel pickup tubing longer so is somewhat counterproductive (fuel-draw wise).

So, I guess my question for others is what is the best way to set up a small 2 oz clunk tank for a smaller profile model w/ small 4-stroke? I guess I could try a larger 3 oz clunk tank, but just fill it w/ 2 oz. But that also seems counterproductive all things considered.

 

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #44 on: March 28, 2024, 03:13:20 PM »
Colin,
I agree about the short clunk tube. Sullivan had a very thin wall silicon tubing just for clunk lines I looked on Brodak's site and don't see it. You might be able to use a heavier clunk, maybe Jim Lee can help on this (Lee's Machine Shop in vendor section). The second choice is surgical tubing, this will work but needs to be change twice a year as it gets soft and may leak but in a plastic tank it is not a problem.

Last option is to use a conventionally vented 2 ish oz tank. Again, make sure the vents are in the free air stream.

Best,    DennisT
« Last Edit: March 29, 2024, 05:02:58 PM by Dennis Toth »

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #45 on: March 29, 2024, 08:41:20 AM »
Colin,
I agree about the short clunk tube. Sullivan had a very thin wall silicon tubing just for clunk lines I looked on Brodak's site and don't see it. You might be able to use a heavier clunk, maybe Jim Lee and help on this (Lee's Machine Shop in vendor section). The second choice is surgical tubing, this will work but needs to be change twice a year as it gets soft and may leak but in a plastic tank it is not a problem.

Last option is to use a conventionally vented 2 ish oz tank. Again, make sure the vents are in the free air stream.

Best,    DennisT

Thanks Dennis

I'm still going to initially try a Brodak 2 oz wide wedge uniflow tank w/ muffler (restrictor) pressure on my Brodak Shark 402. I actually did get in a couple of flights with this arrangement and the setup seemed to run well. But I still need to home in on the best prop, needle setting, throttle opening position, ground rpm, tank height, and line length to use. A bit of trial and error. I'll also eventually try different tank setups for comparison.

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #46 on: April 02, 2024, 06:47:16 PM »
Was able to get in a few more flights on my Brodak Shark 402 (profile model) with OS 26 FS Surpass this morning. Overall, a good experience. I was using 10% nitro, 20% oil (32% castor, 68% syn). 60' - 65# test Spectra lines. Also ran a 2 oz metal wide wedge uniflow tank on muffler (restrictor) pressure.

I first tried a 9.5-6 MAS prop. It was cut down from a MAS 10-6 so a pretty wide prop. I was having trouble setting the needle. My impression was that the wide cut-down prop put too much load on the engine.

I then tried a BY&O 9-6 wood prop. I was able to get a good needle setting at 10,000 rpm on the ground. Model flew fine with engine running pretty much constant rpm no matter what stunt I was doing.

The tank center was in line with the engine intake header. I was getting equal lap times inverted. So, tank height seemed OK.

One thing that was interesting. My lap time with the BY&O wood 9-6 (@10,000 ground rpm) was a little over 5 sec. Same approx lap time on the Shark with a stock OS 25 LA. But since the FS engine is much less noisy, it seemed that the model was flying slower with the FS, but it was not. Really strange feeling. But part of the FS learning process, I guess.

Another observation. Some have said that four-stokes, in general, vibrate a lot. Not the case in my limited experience. I can say I did not notice any undue model vibration, even compared to the OS 25LA which I have run on this same Shark model.

One other note. The 26FS seemed to like the carb throttle around 90% open vs wide open. No power loss as far as I could tell, but nice smooth CL operation.


Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4283
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #47 on: June 28, 2024, 08:38:59 AM »
Colin,
Any update on the OS 26SF? What did you finally settle on for fuel, prop and rpm?

Best,   DennisT

Offline Colin McRae

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 531
  • Are we having fun yet??
Re: OS FS 26 Surpass - Fuel Tank Setup
« Reply #48 on: June 28, 2024, 11:46:30 AM »
Colin,
Any update on the OS 26SF? What did you finally settle on for fuel, prop and rpm?

Best,   DennisT

Hi Dennis

Yes, I have finalized, for now, the setup on the OS 26 FS that will be going on my Brodak Yak 9 that I am currently building. The engine is now oiled up and back in the box awaiting the Yak 9 maiden.

I recently ran the 26 FS on my Brodak Shark 402 basically to get some more FS operational experience. Here is a summary:

-OS 26 FS engine (new engine that has been properly broken in)
-Valves adjusted to OS spec
-Fuel: VP Powermaster 10% nitro-18% oil, with a bit of castor added to boost the total oil content to 20% as recommended in the OS owner's manual. Resultant oil blend is 68% syn/32% castor)
-APC 9-7 sport prop seems very good. I did also try BYO and MAS, but the APC seems optimum)
-Ground rpm right at 10,000 on the APC 9-7 sport
-Brodak 2 oz metal uniflow wide wedge fuel tank centered at the engine intake header. Engine ran the same when inverted.
-Engine uses the stock carb, but I have it set up so I can manually set the throttle position where I want
-Throttle set at 90% open seems better compared to 100% open. Improved fuel draw I assume.
-I have settled in on ram air pressure on the fuel tank. Seems to run better. I also tried muffler (restrictor) pressure, but ram air worked fine on the uniflow tank

Overall, I really like the FS engine on a stunt ship. So much so that I also have an OS 40 FS (non-surpass) and also a 40 FS Surpass in my stash for a future build.

Some have said that FS's in general vibrate too much. That has not been my experience with the 26 FS.

Again, I really appreciate the help and assistance advancing my learning curve w/ FS operation on stunt ships.
« Last Edit: June 29, 2024, 07:45:59 AM by Colin McRae »


Advertise Here
Tags: