Engine for Sig 1/5 scale Cub
 

I am starting a 1/5 scale Sig Cub soon and want opinions on what engine to use. I really want to go with a Saito four stroke. Sig recommends a four stroke up to .65. Saito has discontinued the .65. Will a Saito .62 be a good choice? Sig discourages putting a larger engine in this aircraft.

RE: Engine for Sig 1/5 scale Cub
 

ddrake

I built one for a charity auction last year with a Magnum .70 4-stroke. It fit just fine and the guy who bought it says it flies great. I'm sure the Saito .62 would work, but I like the extra power you get with the .70.

BTW, Quantum models still lists the Saito .65 as available.

papermache

RE: Engine for Sig 1/5 scale Cub
 

Couple of guys in our club have the 1/5 scale cub with Saito .72's in them... Seems to be a great match... Really nice flying planes once you get them off the ground :D

RE: Engine for Sig 1/5 scale Cub
 

I built the Top Flite cub a few years back and used a .46 four stroke. For me it was more than enough power for a cub of that size. Very realistic flight characteristics.

RE: Engine for Sig 1/5 scale Cub
 

Alow me to correct that last post, it was a Goldberg Cub.

RE: Engine for Sig 1/5 scale Cub
 

I see there is a real difference in size and weight between the .65 and the .62.

RE: Engine for Sig 1/5 scale Cub
 

I have a Goldberg Cub and fly it with a 70 surpass. Way too much power. I would like to put a .52 surpass in it.

RE: Engine for Sig 1/5 scale Cub
 

I built one of these and put a Magnum 70 4Stroke in it. It is really much more than is needed or even desireable. The scale size prop is 14", and my engine handles it with no problem. However, the engine is largely underutilized. As nice as it flies at 1/2 throttle (including take off), it is totally out of character flying at full throttle. The pluses are ability to turn a scale sized prop, very nice sound putting along at 1/2 throttle.

On the maiden flight, take off was with throttle smoothly advanced to full: the plane rolled about 6' and promptly "launched" at a 45 degree angle, very uncublike! :)

RE: Engine for Sig 1/5 scale Cub
 

I hadn't heard that Saito had discontinued the .65. Have they got a replacement? There's nothing between the .56 and .72, that leaves a gap in a significant range. If they are coming out with a .62, it should be fine. I'd go with the .72, myself. It is lighter than the .65, makes more power (not that you'll need it), and is the same size. If you use the bigger engine, you can more easily swing a scale diameter prop (14-6 is what I use on my 1/5 Sig Cub, and I have the Saito .65 in mine.(inverted, fits completely within the cowl)

I just checked the specs on Horizon's site for the new .62. All it is is a bored out .56; the stroke is the same as the .56 (19mm), but the bore went from 24.8 to 26.2mm. It ought to be a real revver, but I don't think it will be as torquey as the .65 was. Either the .62 or the .72 should be okay, I'd lean toward the .72.

RE: Engine for Sig 1/5 scale Cub
 

Are you going to clip the wings? If so, I'd go with the .72; better yet- .90 twin (about the same power as a .72).

RE: Engine for Sig 1/5 scale Cub
 

I have a 90" wingspan Great Planes Cub that I converted to a super Cub with a Fiberglass Specialties cowling. My Magnum .91 4-stroke engine is inverted and doesn't even exit the cowling. I am almost finished building mine. All thats left is filling, sanding. and covering. It will be covered in fabric and then painted. I do still have to build the floats for when I want to fly off water.

Gibbs

RE: Engine for Sig 1/5 scale Cub
 

I was wondering how the .65 would run inverted. I do think the Saito head sticking out would look cool though. I did find a .65 at a local hobby store maybe I should run out and get it befor it's gone.

RE: Engine for Sig 1/5 scale Cub
 

I want to build it with the regular wings.

RE: Engine for Sig 1/5 scale Cub
 

Get the .65; I'll bet the price deal is also better now that they're discontinuing it. I wish I could fing some power curve diagrams for the new .62. It's rated at 1.0 hp, but at what rpm I don't know. The .65 is rated at 0.95hp, not a lot of difference in peak power, but I'm willing to bet it will out-torque the .62, which will make it a better engine for the Cub, and here's my reasoning:

Bore on the .62 is 26.2mm, on the .65 it is 24.8mm
Stroke on the .62 is 19mm, on the .65 it is 22.5mm.
If you compare the bore/stroke ratios of each engine, you'll notice that the .65 has a much longer stroke in relation to it's bore, and long stroke engines are generally better at lower rpm torque. This would let you turn a larger prop and run the engine at lower rpms. Since you want a 4-stroke at least partly for the sound, don't you think it would sound better on the Cub just puttering along rather than wound out? Saito recommends a 13-7 as the largest prop for the .62 (will turn it around 9500-9600 rpm); my .65 will turn a 14-6 to the same rpm, but I can cruise at 1/2 throttle easily.

This is all empirical, as I have nothing but my experience with my Saitos to convince me of this. It seems as though Saito is taking the same road that motorcycle design has gone--larger bore and shorter stroke for a given displacement. It allows greater horsepower and allows the engine to rev higher to make the power, but bottom end suffers as a result. Bottom end power can be regained to an extent through valve timing, but then you trade off some top end power to get it.

The old .80 and newer .82 are similar circumstance, the .80 is more "undersquare" than the .82. I liken them to a comparison between an old Triumph twin and a Honda twin of the same displacement.

Enough of my rambling, it's late and I'm tired. The facts are, the .62 makes more power and is lighter than the .65, and the .62 is the same size as the .56. But I know how the .65 performs in my Cub, and I don't think you can go wrong if you go that route. Sideways or inverted. One thing for sure, the newer muffler style sure makes it harder to do a nice scale installation, whichever way you mount it. If you can find one of the old spun aluminum cannister mufflers and an elbow header, it will look a lot better.

RE: Engine for Sig 1/5 scale Cub
 

I built the Sig 1/5 Cub and flew it this past summer. It flew beautiful with an inverted Saito 65 with an onboard glow, much more power than necessary for me. I have since pulled off the .65 and have put on a Saito .50 to bring it to a more realistic power vs. plane ratio for myself. I haven't flown it as of yet, but the Spring will be here soon! I spoke with Gary from Sig( I think that was his name, maybe Glenn???) and he had told me that he used a Saito .45 in his and it produced a very realistic flight performance that he was happy with.
Granted, you can always throttle back with the larger engine, but the Cub seems to fly on minimal power to begin with, similar to the real plane. The Saito .65 can utilize the factory Saito right angle exhaust adapter made for it, which will hide the exhuast in the cowl. If you also use the flex exhuast pipe, you can leave just enough pipe extruding through the bottom of the cowl to give it an original appearence.
Also, I cut out in between the exhuast pipes on the dummy engine to aid in the cooling of the engine. On the oil cooler screen on the bottom front of the cowl, I cut out the center and glued in a piece of black window screen material that also helps the flow of air through the cowl and looks pretty real from a distance also. I had no problems with engine operation in this plane, it just had waaay too much power for what I need with the .65 in it. The .65 is an awsome engine and a dependable engine although slightly on the heavy side.
By the way Ken Hodges, if you read this (and I'm sure you will) I picked up a set of the Robart 1/5 Cub landing gear, got it for a price I just couldn't resist! How many flights do you have on that grasshopper Ken??

RE: Engine for Sig 1/5 scale Cub
 

It's probably flown more than any L-4 did in WWII:), but hasn't been shot at as much. I'm not really sure just how many flights it does have, but it's flown at least one flight every month since I built it, and some days gets as many as four tanks of fuel through it. My .65 is starting to sound as though I might be losing a bearing; there's no resistance, tightness or play in the crank, doesn't knock, and it pulls as well as ever. I have another one new in the box, but hope it will go on another plane.

ddrake, here's my inverted installation, note the muffler type I was talking about. I had to heat and bend the elbow a bit to get the exhaust to exit the bottom of the cowl, this was before that "button" style elbow was available (special order). The brass tube that runs down the left side of the firewall is for the crankcase breather The engine mount is a DuBro antivibe mount.

RE: Engine for Sig 1/5 scale Cub
 

It looks like the firewall was cut away and recessed is this due to the engine or the mount?

RE: Engine for Sig 1/5 scale Cub
 

Mine was powered with an OS 52

RE: Engine for Sig 1/5 scale Cub
 

How was the perfomance with the .52 in it? [sm=confused.gif]

RE: Engine for Sig 1/5 scale Cub
 

Very scale-like....no problems except when it came time to land....it didn't want to :) Not a whole lot of vertical, but enough to do a scale loop.

RE: Engine for Sig 1/5 scale Cub
 

I have pretty much decided to go with the Saito .65. I have never installed an engine inverted before. What should I expect? Will it be trickier to start and adjust? Will it cause flooding issues? Wow I ask a lot of questions. [sm=49_49.gif]

RE: Engine for Sig 1/5 scale Cub
 

You may want to lower the tank a bit. The Sig Cub has a "tank floor" that is notch located behind the firewall. It's no big deal to lower it; mine is still high enough that I can slide my Rx battery pack under it. You want your tank centerline even with to about a 1/4 inch below the height of the carb spraybar. I have a 12 oz tank in mine. My Cub was my first inverted installation, and I put an on-board glow on it to forestall any problems, but once I got the carb adjusted , it's run fine without using the on-board system. I still use it for starting; you'll have to put some kind of remote plug anyway if you go inverted, the glow plug just isn't accessible. I set my system up as a manual, and can turn it on and off whenever I want from a Tx switch (mine is the MPI SuperGlo).

RE: Engine for Sig 1/5 scale Cub
 

Dang Mr. Hodges, You sure an old fart. I had you pictured as a much younger cuss.

Bill, AMA 4720
WACO Brotherhood #1

RE: Engine for Sig 1/5 scale Cub
 

If you're ever going to consider floats, go with the .72.

RE: Engine for Sig 1/5 scale Cub
 

I'm a 52 year old body with an 18 year-old inside, screaming to get out. I wish he would, too, he's giving me a headache[sm=tired.gif]