OS FS 81a in a 47" Pro Yak  
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All Forums >> RC Airplanes >> Profile and Fun Flying Planes >> OMP - Ohio Model Products Support Forum >> OS FS 81a in a 47" Pro Yak
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OS FS 81a in a 47" Pro Yak - 6/14/2009 5:00 AM   
icepunk


 

Posts: 21
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Joined: 11/23/2007
Last Login: 11/3/2009
From: New Westminster, BC, CANADA
Status: offline 		Has anybody tried to mount one of the new OS four strokes ? The carb intake comes down lower than the motor mount forcing you to mount them towards the front. This not only lools funny (prop two inches in front of nose ) it requires adding weight to get the cg right.


curious if anybody had trouble with this.
thx


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RE: OS FS 81a in a 47 - 6/16/2009 2:41 AM   
AFSalmon



Posts: 4164
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Joined: 5/24/2002
Last Login: 11/6/2009
From: Beavercreek, OH,
Status: offline 		Have not heard of that combo.   What are the specs on that engine?

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Mike (Salmon) Pilkenton, Chief Slab Designer
Ohio Model Planes

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RE: OS FS 81a in a 47 - 6/16/2009 3:28 AM   
icepunk


 

Posts: 21
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Joined: 11/23/2007
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From: New Westminster, BC, CANADA
Status: offline 		here is the link to the specs:

http://www.osengines.com/engines/osmg0981.html

It is advertised as an upgrade to .70 four stroke size applications, but the problem is with the new carb design. It requires you to leave some space between the firewall so the carb can breathe as the new intake comes down almost to the bottom of the backplate. My  OS FL-70 is a perfect match for the 47" yak and i have it mounted tight to the fuselage for CG reasons. I would like to mount the .82 tight to the fuse but the new carb doesn't allow for it.   If I cut a bit out of the engine mount at the firewall it might work,  but otherwise I have to mount it over one inch forward and my prop with be sticking out front over 1"  and the plane will be too nose heavy.  :-P

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RE: OS FS 81a in a 47 - 6/16/2009 3:43 AM   
icepunk


 

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From: New Westminster, BC, CANADA
Status: offline 		  I see in the post before this one , someone  is having the same issue with a Saito 82 and the venturie stack off the carb. I will ask OS tommorrow if I can run without it as someone in the other discusion suggested removing it for the Saito.  If the extension off the carb is there only to suck up excess oil I think I can live with out,  it if it means swinging a 15x4W instead of a 13x4W !  I am not crazy about cutting away the fuse.....

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RE: OS FS 81a in a 47 - 6/16/2009 3:48 AM   
icepunk


 

Posts: 21
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Joined: 11/23/2007
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From: New Westminster, BC, CANADA
Status: offline 		I also found this article interesting


http://saito-engines.info/special_tricks.html


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RE: OS FS 81a in a 47 - 6/16/2009 9:29 PM   
Ernie Misner


 

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Status: offline 		Try drilling a hole through the fuse for the stack to sit into.   (better ask Mike's permission first though....     Is the OS 81 stack removable?   If so, supposedly you will just get a bit more spit back oil onto the plane and might see the fuel economy go down a tiny bit.   Not a big deal, just remove it if you are able.    No other OS engines have ever even had a stack available and the tuning is not critical like in a 2-stroke.

Ernie

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RE: OS FS 81a in a 47 - 6/16/2009 9:41 PM   
icepunk


 

Posts: 21
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Joined: 11/23/2007
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From: New Westminster, BC, CANADA
Status: offline 		I think I might try that.  I nee dthe engine as far back as it will go and drilling out a breather hole doesn't sound like a good idea.


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RE: OS FS 81a in a 47 - 6/17/2009 7:22 AM   
freeair


 

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From: queensland, AUSTRALIA
Status: offline 		you shouldn,t have any problems mounting the 81 a .  i have one on these great engines in a Katana 40.  if you worried about nose weight issues you can modify the front bulkhead so you can get the engine back further ,  let us know how you go as i would like to try my 81a in this size profile model.

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RE: OS FS 81a in a 47 - 6/17/2009 5:55 PM   
icepunk


 

Posts: 21
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Joined: 11/23/2007
Last Login: 11/3/2009
From: New Westminster, BC, CANADA
Status: offline 		I have the sent the OS 81a back to Tower Hobbies as the advertised weight  was off by over 2 oz !!!  This only compounds my problem. I am going to try the FS-72a instead and maybe this will resolve some of the mounting issues and allow me to leave room for the intake. I can't beleive OS gets away with this. - 2 oz is quite a bit of lead !  The actual wieght of the engine with muffler is 610 grams  almost 60 grams more than stated in the specs.....**** ?


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