khodges

My Feedback: (1)

I've been out of the hobby for about 13 years, and am in the beginnings of a 1/4 scale BUSA L-4 build. While flying it after finishing is not in the plans, I figure I'll still build it as an airworthy model (hopefully it will become a display piece in a local museum), so I need an engine for it.

My experience with engines is mainly Saito and Zenoah; I notice Zenoah has changed quite a bit, and Saito has upgraded many of their engines. I want gas, not interested in glow or electric. I want plenty of power to turn a scale 18" propeller, and be able to run the engine at less than full power. In my mind, I'd rather have more than I need than marginal or not enough.

What I'm looking at is a Saito FG40 . Propeller range is 19x10 to 21x10, so it would be more than enough to turn an 18x6. There's also the FG30, but the max prop size is an 18x6, the one I plan to use. How would this one do on a Cub, that will be a tad heavier than usual (not sure just how much yet). There's $100 difference between them, I haven't compared physical size yet to see how well it will fit inside the cowl (it will be inverted, whichever engine I install).

What are the DLE engines like, in terms of reliability, power and weight? The 30cc DLE-35RA looks nice and will turn the prop well enough, and the price is half what the Saito is.

If money was no object at all, and it fit in a scale manner, I'd put an OS FF-320 Pegasus in it.

What is everyone with a 1/4 scale Cub using for power?

bryanmiick

I have 2 Sig 1/4 scale cubs with OS GT22 gas engines, one is 16 lbs and the other is 17.5lbs. the engine fits in the cowl and allows for a dummy engine from top notch products. they are not overpowered but fly nice.

tedsander

Usually bad to severely underprop an engine, so an 18x6 on the FG40 is way, way too small. The DLE would also be a bit under, but with good cooling and no prolonged use of top end probably be useable, although I might not expect maximum life out of it....
Others may have better recommendations that fit your desires.

khodges

My Feedback: (1)

Which is worse, too big a prop and the engine works too hard or is unable to spin it, or too small a prop and the engine can loaf? I suppose in the end, the FG-30 would be the one to go with, since it is rated to turn a prop the size I'm using.

I had always used an engine bigger than needed in my models, in order to turn a scale diameter prop, since most of my planes were scale models. But, I see your point, don't put a hemi in a Volkswagen.

It may be an academic discussion, hopefully this plane will hang from a ceiling until the glue rots.

tedsander

Either is bad if done to a large amount. Underpropping results in rpm's going way too high. Ignoring the fall off in torque, it can cause excessive heat build up, component failure, lack of oil distribution, etc. as the rpms go high. An engine that tops out at 10K with a designed prop may do just fine being underpropped and running half throttle. But that one vertical at full throttle where it is hitting 16K ....(yes, I'm just picking random numbers for illustration)...
Still have the remains of my old YS 1.20 that blew apart at the top of a stall turn just for that very reason - running too small a diameter and way, way too small a pitch.....

But if truly intended to be a Hanger Queen, and will only be flown a few times - then cheaper is better......

khodges

My Feedback: (1)

I've decided on the FG-30. It is rated for an 18x6 prop, and easily fits within the J-3/L-4 cowling. At worst, it would fly the plane in a scale manner, which is what I'd want, no hanging on the prop or 3-D stuff.

daveopam

My Feedback: (9)

The DLE35RE would be my choice. Sounds like you have already picked. However other people will read this thread. The 35RE is a great engine for the price is is a reliable compact choice. The RE (rear exhaust) fits most planes well and the muffler is included. I would even recommend the Boman ring. If you buy from Valley View R/C they will put the ring in and drill the prop for you.

David

jaka54

In a 1/4 scale CUB ...an OS FS 1.20 is the perfekt engine! A too big and heavy engine (all over 20cc (1.20cub inch) is making the plane too heavy). A CUB is supposed to fly on its wing not on brute power.

khodges

My Feedback: (1)

The DLE looks nice, but I'm very familiar with Saito, as I powered most of my planes with it when I flew some years ago. I like the 4-stroke sound better than a 2-stroke also.

On a scale model, I want to use a scale diameter prop, so I have to select by what the engine will turn. I've flown several Cubs before, I had a 1/5 scale ARF on floats and built a 1/5 scale kit into a L-4, similar to the project I'm doing now (except this one is 1/4 scale). I'd rather not have to use WOT when flying, you just use what you need for the circumstances. My floatplane had a .72 Saito (glow, no longer made), and my L-4 had a .65 Saito (glow, no longer made) and never needed full throttle for scale flight, but it left me a margin for those unusual circumstances. These were mine, 15 years ago: