Four Star 40 with OS .25FX engine, what do you guys think?

Will it have enough power? This will be my first low wing plane.

well it will fly it. but it will be under powered like nothing i would fly

i run a satio 72 and still use 30%

It will be underpowered to the point that it will be much harder to fly than it should be. You really want a at least a .40 in there. The .25FX can be made to turn up to some high RPMS and produce a lot of power, but you'll wind up flying around at full throttle all the time, and it won't be nearly as much fun as it should be.

If the goal is to build it light go with something like an OS .32sx.

with the .25, after adding the lead to balance it, you would be able to fly, but you would have a very hard time doing a loop. It would only take off from a smoothly paved runway, and then it would take about 200 to 250 ft.

Best advice... NO!

The 4*40 is a GREAT airplane with a mild .40. It will do all the aerobatics it was designed for quite well with a .40 FX (or even a Magnum XL 40) It will HOVER on a .52 4-stroke with power to spare. It will just limp along feebly on a .25

I would definitely try it if you have the 25FX already.

The Four-Star needs surprisingly little power to take off and fly even from grass (I have 3.25" wheels on mine), and I have no doubt at all that the 25FX will fly the plane nicely. A couple of years ago I flew my Balsa USA Stick 40 with an OS 25LA all summer. The 25FX has a lot more power than the 25LA. Although the Stick has a flat-bottom wing and the Four-Star has a nearly symmetrical one, I think the 25FX will work.

If you choose a low-power engine like this, you have to keep in mind that you have to "fly on the wing" all the time. You can't pull the nose up 45 degrees on takeoff and pull the airplane off the ground. You have to let it gain flying speed and use the wing's lift to climb. More realistic when it comes to scale flying, but it demands a lot more from the pilot. You have to fly level to gain speed (or even dive a little) to make enough speed to do a loop. This is what full size aircraft have to do. It depends on what you want from your RC plane. I like scale aerobatics, and even though I have an OS FS-52S in mine, I hardly ever use more than half throttle unless I feel the need for crazy flying. My Irvine 53 has done some time in the Four-Star, and I have to admit that's fun too. For everyday flying I prefer slow, realistic flight though.

Why not buy an Irvine 53 or an OS 50SX and fly at lower throttle settings instead of flying a smaller engine at full bore? My most important reason is weight. My Balsa USA Stick 40 flew SO much better with the 25LA than the FS-52S. The weight difference made landings/takeoffs slower, and the plane felt lighter in the air (more responsive).

If I were to buy an engine for my Four-Star today, I would buy a 32SX or an FS-40S. Both engines will fly the airplane nicely, but you won't be able to go straight up. My Four-Star has unlimited vertical with the FS-52S with APC 12x6 on 5% nitro (500 ft MSL).

Agreed, the 4* will fly on the 25FX, but it will take more 'skill' to fly it. If money's an issue, look for a used OS 40FP or OS 46 LA. Both can be had at auctions for about $35 and would fly the plane quite well.
Dennis-

Build light, especially in the tail. Make a built up structure for stab, fin and rudder--easy to do, strong, and saves a lot of weight in a place that has a lot of leverage on the CG. Consider using a light covering--transparent film or Micafilm. Experiment with props--they can make a big difference and the only way to tell what's best is by flight testing. I'd try a 10x3 among others.
Use the lightest wheels you can find. Think of every part of the plane in terms of how you might make it lighter. It's amazing how the little things add up. I built a Balsa USA Stingray 40 (similar to the 4*40) to barely over 4 lbs and it flew very well with an OS 40FP. All the others in the club were 5 1/2 to 6 lbs or more. Keep yours light and the .25 will be fun with it. It's not for everyone--low power aerobatics are a different kind of challenge. Go to the AMA archives for a great article on it by Keith Shaw. Have fun! Jim

The OS .25FX is pretty potent and the OS .40LA isn't and I've seen them in a 4*. As has been said, be careful about tail weight. You can use a smaller tank, which will save fuel weight and allow you to put the battery under the tank.

I would mount the engine reasonably far out on the mounts before I installed the radio. I would locate then after everything else is done. You can move the throttle servo up next to the tank. You can move the aileron servo forward. You might check out pull-pull on rudder since it would add less tail weight. I would also consider pull-pull on elevator or use a hard balsa 1/4 square for the elevator pushrod.

I certainly would not use fabric, which Sig says not to anyway. I forget if all the surfaces are built up or if some are solid. I would build up all of them. Also get a light tail wheel.

Finally, I would clip each wing 1 rib. I would do this anyway for better roll performance, but it will also save a little.

I think if you can keep from adding lead up front, you'll can have a nice airplane.

Teh 4*40 tends to be noseheavy... lightening the tail is probably not a factor in putting a .25 on it.

Thanks a lot for the reply guys!

I already own a .25FX, but I think I will either buy another engine for this plane, or go for another kit?

Any recommendation for a .25 kit? I already have the Kadet LT 25!!

Thanks!

I would say to take a look at some of the 1/12 scale kits. They are designed for combat but many have landing gear option. There are a couple of neat plans available from MAN and RCM. Rich Uravich did a coupla nice 25 size plans. He did a nice extra. Some of the fun fly planes will fly well with that engine. They will not be able to do 3-D tricks. But with control surfaces tamed down will fly real good on a 25.

Mark Shuman

Ace made a smaller pacer that a .25 works well in. It flys great too. I would go more that route. Maybe a sportster 25 if you can find one. Seems they used to make them, I don't know if they still do.