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OS 1.20 pumped too small?

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OS 1.20 pumped too small?

Old 08-28-2016, 02:19 PM
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Default OS 1.20 pumped too small?

I have a Dynaflite Decathlon with an 89" wing span with a weight of 16-18 lbs.
I'd like to use my OS 1.20 4 stroke with it. The instructions say a 1.20 is the smallest four stroke I can use with the Deacthlon. Does anyone know anyone with that model that uses an OS 1.20 4 stroke? Is it enough power? I don't have to be able to hover. In fact I'd like it to be more realistically powered that all out powered.

Thanks
Old 08-28-2016, 06:06 PM
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I have the Decathlon in my inventory of aircraft and I have a Saito 1.25 installed. It flies just fine, but then I am a "conservative" flyer. The Saito generates enough power with a MA 16x6 prop for smooth take offs from a grass runway. I am satisfied with the performance that this engine provides. The Decathlon is a smooth and stable aircraft.
Old 08-28-2016, 07:22 PM
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I have one also first maiden was about two weeks ago so far about fifteen flights including two this morning. Mine has a Super Tiger G-2500 which is 1.4 Cubic inch or 23cc and turns a 17x6. It flys nicely but I would not have wanted any less power and am thinking that a 30cc gasser would have been better.

I also fly two airplanes that I do use the OS 120se's on and they serve quite nicely there, they are my glider tug a Great Planes PT-17 about 12 pounds and a Balsa USA N-28 about the same weight. I do not have a weight yet for the Decathalon yet but it is considerably more than either with the OS engines.

John
Old 08-29-2016, 12:02 AM
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I should be ok then. I'd like to be able to do some loops and maybe barrel rolls but like I said, I don't have to hover...
'thanks a lot for your reply!
Old 08-29-2016, 05:56 AM
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Hmm believe me hovering is not even remotely in the equation when talking of the performance of my ship. Yes rolls are quite easy especialy if one uses the rudder with the roll. Loops however are a different matter and proper entry with a dive for speed is Ok but anything less does tend to end up falling out.

I am glad I went with at least 1.4 displacement and long for a little more. This is after all an eighteen pound airplane.

John
Old 09-02-2016, 07:57 AM
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If you run 30% heli mix fuel, you will get a substantial increase in power from your 1.20. 4 strokes benefit the most from higher nitro content. It does not hurt the engine or make it any harder to tune. You will be able to turn larger props that would otherwise lug the engine down.
Old 09-02-2016, 03:39 PM
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Thanks Steve!
I didn't know I could run that high of nitro. Anyway, I just got the engine mounted so I bolted on the wing, filled the tank, took it outside and fired it up. The OS 120 is plenty on power!!.. I was surprised how easily it pulled the plane through the grass and how fast it would accelerate!.. I think I'll be fine with the 1.20 in it..
Old 09-02-2016, 03:50 PM
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You should try a jug. But, be warned, you won't be happy with anything else if you do.
Old 09-02-2016, 08:56 PM
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Will it be more efficient?..couldn't believe how fast it emptied a 24 ounce tank of fuel!
Old 09-03-2016, 11:11 AM
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Originally Posted by chucksaw812
Will it be more efficient?..couldn't believe how fast it emptied a 24 ounce tank of fuel!
In terms of fuel consumption per minute that is doubtful.

Also be careful in the use of Heli fuels and be sure you using a mix with sufficient oils for your engne.

John
Old 09-03-2016, 03:57 PM
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Okay, right now I'm using a 20/20 mix. It runs great but it seems like it smokes more than I thought a four stroke would. Here's a video of the engine running. Do,you think that the smoke is excessive or about right for a 4 stroke?

https://youtu.be/x3Vuy4hEP_E
Old 09-03-2016, 03:59 PM
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Also, I didn't choose the color. I bought the plane from a guy and its his color scheme. I plan on redoing it in the traditional original red. Once I make sure it will actually fly that is!
Old 09-03-2016, 04:43 PM
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To put it in Champion speak, It will probably fly like a Continental 0-200 100 hp powered Citabria vs a 150 hp Citabria or a 180 hp Decathlon.
Old 09-03-2016, 06:01 PM
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That's ok...it may have its first test flight tomorrow!
Old 09-03-2016, 08:26 PM
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Yes that amount of smoke can be normal at various rpm's. Chuck is that your flying field? How many feet in usable runway do you have?

Also I hope you are aware that that it takes more skill to handle an underpowered airplane than one that maybe more appropriately powered. Even the builders manual hints at this in its suggestion that a 120 four stroke is the absolute minimum.

John
Old 09-04-2016, 05:33 PM
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No no no,..no that's just my yard,..I was testing a new 20/20 fuel I got and making sure the engine was running right..a 1.20 may be the minimum but, when I gave it full power it took off as fast or faster than any plane I've ever flown before.Ive definitely flown some that had less power than this one...since this post I've seen a few fly with the OS 120 and they flew fine...took off fine and only needed a medium distance for take off.. A 1.20 May be the minimum but I'm thinking they meant it was the minimum for any type of aerobatics...still able to perform aerobatics but not fly like a Rocket like a plane the maximum engine would....
Old 09-04-2016, 06:24 PM
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Excellent Chuck and congratulations on your successful maiden just trying to cover all bases before Your maiden I am enjoying mine too is an elegant flyer. 20 flight s now but had to put it back on the roost in the living room for now though. Got a maiden to do in the morning, a ship an with an OS 120fs this one is a Nieuport 28 but weighs just under 14 pounds.

John

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Old 09-04-2016, 06:39 PM
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Thank you John, I wasn't disagreeing with you. I was just thinking that it was more powerful that I thought it would be. I appreciate your help and answers. Good luck on your maiden tomorrow...hope you have a safe flight..
Old 09-04-2016, 06:41 PM
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Never heard of a nieuport 28.. Had to look that one up...looks like a fun plane. Is that a kit plane or scratch built?
Old 09-04-2016, 07:06 PM
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Its a BalsaUSA kit that's been around quite a few years now.

John
Old 09-06-2016, 05:02 PM
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Sorry Chuck I did not get to the maiden until early this morning almost no winds and got in two flights and they went quite well. Airplane tracked nice both takeoff and landing and was off the ground much faster than expected but rate of climb was rather lethargic.

John

Probably can,t tell but that's a happy grin behind the top wing in that last photo


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Old 09-06-2016, 05:06 PM
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That,..is a nice looking plane!..I bet it's fun to fly..looks like you have a nice area to fly at..what engine do you have in her?
Old 09-07-2016, 08:35 AM
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Chuck it is an OS 120se.
Old 09-07-2016, 02:10 PM
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Oh ok,...great engine...realistic sound..

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