Yak 9 engine question?
11-20-2009, 09:45 PM
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Yak 9 engine question?
I have flown my Brodak/Sterling Yak 9 twice now and I am not to thrilled with the Fox 35. I had to add alot of weight to the tail I hate haveing to bring a different fuel for it. So I was thinking of getting a OS 25LA. What's everyone thoughts on this engine? Spec wise it will turn similar props at more rpm plus it will run on just regular sport fuel.
Would this be a good choice for the Yak? My AUW with the Fox is 1lb 13oz
Would this be a good choice for the Yak? My AUW with the Fox is 1lb 13oz
11-20-2009, 10:16 PM
#2
RE: Yak 9 engine question?
I'd be more than happy to take that Fox off your hands... 
It flew my Yak just fine (and the Mustang and the Midwest ME-109 and Aircobra as well as the TopFlite "Tutor".)
IMHO, it's hard to beat a Fox 35 if you build light and watch the CG. The OS .35 is another good choice.
It flew my Yak just fine (and the Mustang and the Midwest ME-109 and Aircobra as well as the TopFlite "Tutor".)
IMHO, it's hard to beat a Fox 35 if you build light and watch the CG. The OS .35 is another good choice.
11-21-2009, 07:26 AM
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RE: Yak 9 engine question?
Well 2 to 1 maybe it needs to be broken in a bit more? I ran a 9x6 for brake in now I use a 10x6. For fuel I am running Fox super Fuel 5% nitro 29% all castor
11-21-2009, 10:16 AM
#6
RE: Yak 9 engine question?
I flew a Sterling Yak-9 back in the fifties with a K&B Greenhead .29 and it did everything my Sterling Mustang with Fox .35 could do.
We even stuck a K&B .19 in a Mustang and it flew great.
We even stuck a K&B .19 in a Mustang and it flew great.
11-21-2009, 03:29 PM
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RE: Yak 9 engine question?
It isnt uncommon for a Fox to need a gallon or more of fuel run thru it before being completely broken in. The old style iron piston breaks in slow but on high castor fuel will last nearly forever. I have a 40+ year old Veco 29 that still has great compression.
Bob
Bob
11-21-2009, 04:08 PM
#8
RE: Yak 9 engine question?
The Fox .35 is an excellent choice but the new engines do run with less vibration.
Some Foxes need break-in, some do not. To give it the benefit of doubt, I would ALWAYS break-in an iron/steel engine. A few (5-6) heat cycles and you should know if it needs more. If it holds peak without "sagging" it should be good to go.
If you are using the Fox muffler, perhaps switching to a tongue muffler will allow you to remove some tail weight.
George
Some Foxes need break-in, some do not. To give it the benefit of doubt, I would ALWAYS break-in an iron/steel engine. A few (5-6) heat cycles and you should know if it needs more. If it holds peak without "sagging" it should be good to go.
If you are using the Fox muffler, perhaps switching to a tongue muffler will allow you to remove some tail weight.
George
12-03-2009, 10:21 AM
#9
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RE: Yak 9 engine question?
Hi- the Fox 35 is a good engine and just when it is at its 'screaming peak power' a rod will let go! We used to do racing with these engines. Like previous posts relate- it takes a while to get the piston-cylinder to seat.
12-03-2009, 12:30 PM
#11
Senior Member
RE: Yak 9 engine question?
Run down this thread to the picture of my smallest and least effective muffler.
http://www.rcuniverse.com/forum/m_9165158/tm.htm
http://www.rcuniverse.com/forum/m_9165158/tm.htm
