"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

OK .074 recommendation

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Old 11-21-2011, 07:56 PM
  #1
jeffie8696
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Default OK .074 recommendation

What prop for an OK .074? Seems like the 6X4 might be a bit small but Idont know if this engine is supposed to be a stump puller or a revver.
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Old 11-21-2011, 08:05 PM
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66Malibu
 
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Default RE: OK .074 recommendation

The Top Flight Prop Chart circa 1960 calls for 7x4 for Stunt and Free Flight, 4 1/2 X7 for Speed, and 8X3 1/2 for R/C for the OKCub .074.....FWIW...
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Old 11-21-2011, 08:10 PM
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Default RE: OK .074 recommendation

APC makes a special prop for .15 size combat that is 6.5X4.5. You might give that one a try. The OK isnt a stump puller... more like a Cox reed engine that can turn larger props.
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Old 11-21-2011, 08:42 PM
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Default RE: OK .074 recommendation

Hello Jeffies, Just prop the thing for the plane, & don't worry 'bout the engine. These things breath so poorly, that regardless of prop, you're not likely to reach "destruct" speed (the rod & crank don't like 18K) unless you really get serious with the mods. ........... Some RPM readings for a stock .074 Cub ; MAS 7x3 = 11,500, ........... APC 4.75x4.75 = 13,400, ........... APC 4.75x4 = 14,700 .......... APC 5.7x3 = 14,000 ............... APC 5x3= 15,900 , .............. TD 5.5x4 = 12,600, ........... MAS 5.5x4 = 14,000
MAS 5.5x4 cut to 5" diameter = 15,000 .............................. I've had one of these mounted on a EPP mustang (street fighter?) for the last 2 or 3 yrs.. The AUW is 'bout 8+ OZs. Have tried a load of props, & have settled on the APC 5.7x3 or MAS 5.5x4. Slight difference in verticle & speed. Either way, quite a blast .!!!!!!!!!! ................ George K.
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Old 11-30-2011, 07:55 AM
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Default RE: OK .074 recommendation

Thanks George. Iwas worried about over revving it . Imay try the 6X4 just to see if its a runner.
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Old 11-30-2011, 05:41 PM
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Default RE: OK .074 recommendation

as a lot younger person I used Cub 074's on 1/2A flite streaks and musciano hollow logs and really didn't do any better then a baby bee or cub 049.
The Cubs were mostly anemic but to their credit you could slap almost any of the recommended props within reason and it would turn them enough to get you airborne. Powerhouses they are not but I surely did have my share of fun with them 50 years ago.
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Old 12-01-2011, 04:52 AM
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Default RE: OK .074 recommendation


Quote:
ORIGINAL: dennis

as a lot younger person I used Cub 074's on 1/2A flite streaks and musciano hollow logs and really didn't do any better then a baby bee or cub 049.
The Cubs were mostly anemic but to their credit you could slap almost any of the recommended props within reason and it would turn them enough to get you airborne. Powerhouses they are not but I surely did have my share of fun with them 50 years ago.
Dennis
DITTO, except that I have to go back 'bout 60 yrs for when I got my first .074 cub. That engine replaced my first ever model engine (.049 Atwood Wasp) on a Jim Walker FireBaby. The wasp was so weak that I thought the Cub was a real powerhouse!!! Took me awhile to save for the cub; Making $.10/hr. then. .... Ah, memories from more simple times. ......... George K.
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