1/4 scale sig cub engine ?  
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1/4 scale sig cub engine ? - 3/3/2007 2:32:36 AM   
racer-RCU


 

Posts: 483
Joined: 12/3/2002
From: charlotte, NC, USA
Status: offline 		Building a sig 1/4 scale cub and have an o.s. 91 4 stroke engine laying around and was wondering how good it would fly this cub, anybody flying this combo?
       Post #: 1

RE: 1/4 scale sig cub engine ? - 3/3/2007 4:50:39 AM   
Wayne22



Posts: 4516
Joined: 4/10/2002
From: Edmonton, AB, CANADA
Status: offline 		As a matter of fact, I have flown something very similar...with a Saito 91 4 stroke. We ended up adding quite a bit of lead (12 or 14 oz if I remember...) to the firewall to compensate for the lighter engine. The cub flew just fine with that engine, although going up was not its' forte. I was able to do loops, hammerheads, wingovers, even inverted flight with that engine. But I have to be honest, it was not very exciting to fly. I swapped that engine and the ballast for a G-20Ei and it is much more energetic, and fun...
Normal power for these birds is a 120 4 stroke, or a G-23 / 26......but there is flexibility in both directions..

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RE: 1/4 scale sig cub engine ? - 3/3/2007 5:41:54 AM   
Bass1



Posts: 1895
Joined: 12/26/2002
From: Va.Beach, VA, USA
Status: online 		I would think a 120 four stroke would be about right for scale like flight. Maybe a 150 for a little more umph and peace of mind! The OS 91 would work if the airplane was built extremely light and would probably be pretty close to the 40 hp type power on the full scale version but it would be pushing it (comfort level) on the model IMHO.

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       Post #: 3

RE: 1/4 scale sig cub engine ? - 3/3/2007 7:33:18 AM   
Jigley3


 

Posts: 128
Joined: 10/7/2004
From: dryden, ON, CANADA
Status: offline 		Hi all
I Put a 120 four banger in my Sig Cub and if I was doing it again I would chose the 91.
If you like, a scale like flight the 120 is much more than necessary. On my aircraft, the throttle seldom goes past half, even on take off.
It is a J3 after all, so hauling all the extra weight around is pointless..... bert


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       Post #: 4

RE: 1/4 scale sig cub engine ? - 3/4/2007 2:32:46 AM   
carlbecker



Posts: 1691
Joined: 7/29/2002
From: Fairfax, VA, USA
Status: offline 		I had a OS91fx then a OS120 twin in my 1/4 Cubs. For scale flight the 120 twin was a bit much but lots of fun. A 91 would fly it but then I don't think it would be quite as much fun. Its a great rudder plane!!

Carl

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       Post #: 5

RE: 1/4 scale sig cub engine ? - 3/31/2007 9:19:05 PM   
rv4pilott


 

Posts: 34
Joined: 2/27/2004
From: Southington, CT, USA
Status: offline 		Hello! I just got back from the flying field with my 1/4 Cub. It is powered with a Saito 91 spinning an APC 15x4 prop. The plane weighs 13 3/4 LBS. ready to fly. As far as the comments on "scale power" goes........ The 91 is WAY more power than a full size Cub! I have about 34 hours in the full scale Cub. I am a Private Pilot. With the 91 it takes off in about 35 to 40 feet and climbs at about a 20 degree angle at a pretty decent speed. It does loops and rolls at half throttle. It also (much to everyones suprise at the field) does knife edge from one end of the field to the other without losing altitude! The knife attitude is at about a 45 degree angle. I have maximum throw on the rudder and quite a bit on everything else. Also the CG is at almost 5 inches back from the leading edge. I know you will not believe it but those are the facts. Some people at the field thought it was imoral to see a Cub do that! So, to anyone who does not think a 91 will power a 1/4 Scale Cub and do a good job at it...... you are dead wrong! I think it is the correct engine for the plane. This is a Balsa USA kit. ............... Jeff

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       Post #: 6

RE: 1/4 scale sig cub engine ? - 4/1/2007 5:51:40 PM   
EF


 

Posts: 250
Joined: 2/25/2005
From: HAIFA, ISRAEL
Status: offline 		Interesting and a little confusing for me...

I am building the Clipped Wing Sig Cub at 1/4 scale, and have a Magnum 91 already fitted nicely.
This decision is based on my Precedent Aeronca Champ that at 108" span and 10.5 Lb., flys great on an old OS 61 FSR two stroker with a 13-5 APC. Takes off with authority, needs 50% to maintain level flight.

However, I've read quite a few posts indicating I may be pushing it a bit...so I started considering a Magnum (?) 120 in place, though wouldn't realy like to fit a new engine...

So now I understand that maybe I am OK with the 91? I might add I build rather light (started in the hobby with free-flight sailplanes...) and fly off asphalt. The CWC will be covered with Dave Brown's Skyloft (after happy experience with it on my Sig Smith Miniplane).

Comments?



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Erez

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RE: 1/4 scale sig cub engine ? - 4/1/2007 6:42:31 PM   
Wayne22



Posts: 4516
Joined: 4/10/2002
From: Edmonton, AB, CANADA
Status: offline 		It will fly just fine....Mine was built extremely light, and I ended up adding a ton of ballast in the nose with the smaller engine. It still flew fine. I was trying to think back on all the 1/4 scale cubs that I have flown, and I think only 1 had a 120 on it, and it was on floats... the others were anywhere from a Saito 91 to a G-38 ...........





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RE: 1/4 scale sig cub engine ? - 4/2/2007 2:07:49 AM   
rv4pilott


 

Posts: 34
Joined: 2/27/2004
From: Southington, CT, USA
Status: offline 		It will fly just fine with that engine. A 120 would make it climb straight up at a very light weight. Mine is the 108" cub at about 13 3/4 pounds and it does real well on the Saito 91. The CWC at 11 pounds should be good. Jeff

(in reply to Wayne22)
       Post #: 9

RE: 1/4 scale sig cub engine ? - 6/20/2007 5:30:10 AM   
aeroclassics


 

Posts: 13
Joined: 6/16/2004
From: Carrollton, TX, USA
Status: offline 		A .91FS! Drat! Am I going to be WAAAAAAYYYYYYYYY overpowered! I have a Saito 1.50 that I am currently fitting to the nose of my BUSA 1/4 Cub. I do plan on spinning a scale 18" prop. Mine might come in heavier as I am adding scale gear and an interior plus pull-pull on all the surfaces. Even still I think I have too much engine. I was thinking about starting my competition career with this plane. Sounds like I would be better off with a 1.20 since mine will spend a fair amount of time on floats. I am just not sure a .91Fs would pull a 14lb Cub + floats off the water very well.

Since I am very much interested in scale flight I think I need to reconsider engines. What do you think? For a competition Cub that will be on floats ditch the 1.50 for a Saito 1.20 or a Saito 1.00?

There is also a used OS FT-160 at my LHS. Has the stock carb replaced with a dual needle carb, on-board glow etc for $369! The engine was originally bought from the same shop and has had two owners. Both take excellent care of their gear. Probably too much engine but it sure is tempting!!

Doug

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RE: 1/4 scale sig cub engine ? - 6/20/2007 7:04:30 AM   
Wayne22



Posts: 4516
Joined: 4/10/2002
From: Edmonton, AB, CANADA
Status: offline 		If you are going to fly on floats, leave the 150 on...it is not that much more power than a 120, (and the 120 does have have that much more than a 91) we are talking fractions of a horsepower here.
The 150 would allow you some flexibility of swinging a bigger prop at lower RPM..If you compete at higher elevations, or hotter climates, you won't be hurt so much by the power loss..... Remember the throttle works in both directions....!

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RE: 1/4 scale sig cub engine ? - 6/20/2007 4:31:28 PM   
aeroclassics


 

Posts: 13
Joined: 6/16/2004
From: Carrollton, TX, USA
Status: offline 		Thanks! It is true the throttle works in both directions ;-) Surgery is required to get the 1.50 on. While it isn't difficult to do, a 1.00, 1.20 or the OS-160 Gemini all wuld most likely fit without and changes. The lowest pitch prop in an 18" size I can fine is a 6. Wish someone made a 18 x 5 or an 18 x 4.

That OS-160 twin sure is tempting!

Doug

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RE: 1/4 scale sig cub engine ? - 7/29/2007 10:58:16 PM   
WECoyote


 

Posts: 4
Joined: 11/29/2003
From: Watertown, WI, USA
Status: offline 		What about a Fox Eagle 74 for power?

I ask because my father has a Balsa USA 1/4 scale Cub that he has been working on and that is the engine he is using. The Cub is nearly done and needs only a couple more hours of finishing work before it is ready for its maiden flight (only took 13+ years to get there ) I have my doubts about the Eagle 74 having enough power to fly anything beyond scale like and am concerned that at a critical moment the lack of power could spell disaster. I'm thinking a Saito 125 or 150 would be a better choice however, it is going to require some 'surgery' for sure to change over to a Saito power plant which would delay the Cub's completion even more

Anybody have or know of a BUSA (or equivalent) 1/4 scale Cub powered by a Fox Eagle 74?
I would like to hear about how well it performs. Thanks!

Mike

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       Post #: 13

RE: 1/4 scale sig cub engine ? - 7/30/2007 3:16:48 AM   
Wayne22



Posts: 4516
Joined: 4/10/2002
From: Edmonton, AB, CANADA
Status: offline 		I'm afraid I don't have any good success stories with that engine... If you have one that runs well, it may well fly, but don't expect any spirited performance..... a lot will depend on the weight of the finished cub.



< Message edited by Wayne22 -- 7/30/2007 7:01:05 AM >

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RE: 1/4 scale sig cub engine ? - 7/30/2007 3:27:27 AM