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Author Topic: OS 15LA setup on Sig Akromaster  (Read 1758 times)

Offline Marty Hammersmith

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OS 15LA setup on Sig Akromaster
« on: October 10, 2023, 02:53:15 PM »


     I have converted an R/C OS 15LA to CL using a venturi and needle valve from shtterman on eBay. My tongue muffler does not have a provision for a pressure tap. The tank is an oval profile 2oz Brodak "standard vent" BH-566. Can I run this setup with just the line from the tank to the needle valve? This will be a profile Sig Akromaster.
Marty Hammersmith
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Offline Dan McEntee

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Re: OS 15LA setup on Sig Akromaster
« Reply #1 on: October 10, 2023, 04:29:56 PM »
      Yes. This will be an old school set up like in the old days before uniflow tanks came to be common. Mount the tank with some clearance between it and the engine. The centerline ( the pick up tube) of the tank should be just a fuzz above the centerline of the engine, or at least be able to adjust it that way in the future. The over flow tube is the one that comes out the bottom. The fill/vent tube comes out the top. The engine will run best when you cap the over flow tube after filling, and then put an angled piece of fuel line on the fill tube and have that angle cut facing forward. That will prevent any air that passes over the fill/vent tube from creating a chimney effect and make negative pressure in the tank, cause erratic runs.  The engine WILL speed up a bit after the tank level get s below half way as there is less "head pressure" or weight of the fuel pushing it towards the needle valve. You get some help from centrifugal force creating some fuel head pressure once you are in the air. Try an 8-4 to 8-4 prop on the engine as a starting point. Lines can be .012 or .015 steel or the new fishing line variety in a 30 pound test I think would be safe, both types being about 54 feet long. Fuel for an LA can be 5 or 10% nitro and most hobby shops carry Omega from Morgan Fuels.
  Have fun!
   Dan McEntee
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Offline Miotch

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Re: OS 15LA setup on Sig Akromaster
« Reply #2 on: October 11, 2023, 07:37:03 AM »
Had the same plane/engine setup about 18 years ago for a while and it worked great.  I did it the old-school way, like Dan indicated, with a wedge tank and angled pieces of fuel tubing.  Unfortunately, the plane was a victim of garage rash with extreme prejudice when I inadvertently lowered our attic ceiling ladder onto the unsuspecting Akromaster.  Still have the little blue engine, though.

Offline Steve Helmick

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Re: OS 15LA setup on Sig Akromaster
« Reply #3 on: October 12, 2023, 10:41:20 AM »
Whether you have a pressure tap on the muffler or not, a uniflow tank would be a good thing. The engine would then hold a steady setting for the whole run. Please, do not fail to let the engine warm up for 15 seconds or so before setting the needle valve!  R%%%% Steve
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Offline Marty Hammersmith

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Re: OS 15LA setup on Sig Akromaster
« Reply #4 on: December 24, 2023, 11:37:33 AM »
As a followup, the Akromaster is now flying. I just wanted to report back after it's first 30 flights. The fuel tank is a Brodak  standard vent BH 566 2oz. I set the needle slightly rich with the airplane on the stooge and as Steve suggested, let it warm up a few seconds to stabilize. Upon launch the run goes into a clean 2 stroke and stays that way until empty.  Positive loops and wing overs don't seem to disturb the tune. Currently I am running 8% nitro fuel and 21% oil (50/50). Very happy with the results. I'm not having to fiddle with the needle to speak of and cent of tank position is slightly below the needle valve.
Marty Hammersmith
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Offline 944_Jim

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Re: OS 15LA setup on Sig Akromaster
« Reply #5 on: December 24, 2023, 05:42:30 PM »
Is this Alro #1 or Revenge of Akro?

30 flights? In my hands that is a world record! Good to hear of a working combination for this plane.

Offline Dwayne Donnelly

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Re: OS 15LA setup on Sig Akromaster
« Reply #6 on: December 25, 2023, 11:41:34 AM »
Timely post, I'm going to use a LA 15 in a Jr Nobler, I was going to order a 1.5 oz. tank as I thought a 2 oz. would be to big, what flight times are you getting from 2 oz.
Thanks
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Offline Brett Buck

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Re: OS 15LA setup on Sig Akromaster
« Reply #7 on: December 25, 2023, 05:47:59 PM »
As a followup, the Akromaster is now flying. I just wanted to report back after it's first 30 flights. The fuel tank is a Brodak  standard vent BH 566 2oz. I set the needle slightly rich with the airplane on the stooge and as Steve suggested, let it warm up a few seconds to stabilize. Upon launch the run goes into a clean 2 stroke and stays that way until empty.  Positive loops and wing overs don't seem to disturb the tune. Currently I am running 8% nitro fuel and 21% oil (50/50). Very happy with the results. I'm not having to fiddle with the needle to speak of and cent of tank position is slightly below the needle valve.

  What prop are you running?

    Brett

Offline Marty Hammersmith

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Re: OS 15LA setup on Sig Akromaster
« Reply #8 on: January 08, 2024, 03:22:00 PM »
Is this Alro #1 or Revenge of Akro?

30 flights? In my hands that is a world record! Good to hear of a working combination for this plane.

LOL. This is the original short wing Koverall Akromaster #1. The long wing Silkspan covered Akromaster is almost but not quite finished.

To the other questions, I don't know the runtime but it is not short. I know I'm currently using 7 cranks of a Dave Brown fuel pump. It's something less than 2oz since that's the tank size and 7 cranks isn't filling it. I definitely would not go bigger if using a modern engine like the OS 15 LA. On my new Akromaster with the Veco 19 I will likely need the whole 2oz or maybe a little more as I expect it will be a little sloppy in the way it consumes fuel.
Marty Hammersmith
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