Dear all,
I just bought an extra 300l .15 size plane. ( wingspan 930mm and fueslage length is 840mm )The overall weight is about 1,100 - 1,300 grams. No doubt the spec ask for .15 engine, I intend to put in a .25 engine. Will it be okay considering an additional weight of 78 grams from an O.S .15 to a O.S .25 engine. Will the plane head be heavy because of the additional weight on the .25 engine? Any ways to rectify this problem? or do you think that the O.S .15 CV-A performance will be on par with the O.S .25FX?
Any comments will be appreciated.
Thanks

Two considerations:
The extra weight will require extra power and you will have it.
The extra weight might upset the balance and require that you move equipment aft. And the structure of the airframe might not be up to all the extra weight.

yes, if the design was balanced with the lighter engine, it will be noseheavy with the heavier engine.

The power to weight will make up for the extra weight, but the problem of airframe strength is one you need to study and possibly solve.

No.

BTW, lot's of builders fit larger motors into airplanes that were not designed for them Most often, the airplane flies. But there are limits.

Larger airplanes will take "oversized" engines with less problem than smaller airplanes. With our models, the larger the airplane the more structure in that airplane. It's not a proportional increase in structure. The smaller airplanes are a lot weaker because they have a lot less structure. If we increase the size of a model 25% for example, the increase in internal structure might increase 75%.

The airplanes that are designed for small engines are very lightly built. They have to be in order to fly. That structure has little or no excess strength. So increasing the engine weight and power on a small model is much more apt to cause structural problems in the small model that would not happen in a larger model.

Also, small airplanes are much more sensitive to flight trim. They're much harder to fly and they're much more sensitive to wind. When you overpower a model, it can become more sensitive to trim and fly.

It will be a lot harder to produce a good flying model from that 15size airplane with the 25 engine in it.

Hi Darock,
Thanks alot on the information. Really appreciate this fast reply. The fact is that i'm quite confuse with numerous comments from flyer in my field. Some advise to go .25 while others suggested .15.
The reason for those who suggested .25 engine is base on the plane information of weight 1300grams, wingspan - 930mm and fueslage of 840mm. They believe it's a bit too heavy and big to be fitted with a .15 engine.
Darock, with your experience, can you give me a honest comments on whether I should stick to a .15 or upgrade to a .25?
Thanks in advance

If they're experienced flyers they're probably right. If they've also got experience with a similar swap at that size, they're certainly right.

I've used a .20s on a .15 sized airplane and it worked, but I built the airplane from plans and reinforced it as I built. The airplane was harder to fly than before, but it wasn't a trainer nor was it large for a .15 sized airplane.

An Edge is an aerobatic airplane so you're not expecting it to be slow and stable. Go for it.

I gave you honest comments on what to expect generally. And I'm confident those things will happen. But with my experience I know for a fact that nobody can predict the weather more than a week away nor what exactly will happen if you change a model airplane.

About the only thing I'd add to my previous generalizations would be that you look for a .20 that's as close to the weight of your .15 as you can find. And the same advice if you decide on a .25.

I don't know what engines you're comparing but if we take the two OS engines that are those sizes:

The .15 is 6 ounces and is advertised to produce .5hp.
The .25 is about 11 ounces and is advertised at .8hp.

The 25 is almost twice as heavy and produces roughly 40% more horsepower than the 15. Those are significant differences.

Put all the equipment in the airplane aft. Build a stronger area for the battery aft. Don't worry too much that it's weight toward the rear because the airplane will need it. Expect to have a tiger by the tail when you lift it off the first time.

I'd do it. It's an Edge and supposed to be a flyer's airplane. It will be. And it ought to be fun.

The info that Darock puts out is right on the money. There is nothing wrong with putting a larger engine on a plane, as long as you take into account a couple of things. Strength of the airframe, and balance of the plane.

Balance. Putting a larger engine on the plane will change to balance of the plane. You'll either have to move around equipment in the plane to re balance the plane, or add weight to the tail.

Strength of the airframe. This is a biggie. Especially the firewall. A bigger engine is going to put stresses on the airframe that it wasn't built for. Many times the firewall at a minimum, and the rest of the fuselage at times, needs to be made stronger. This usually isn't an issue when you are building the plane from a kit because you can evaluate every joint and part in the plane to see if it can handle the extra stress. But on an ARF, or a pre-built plane, you usually can't see the structure of the plane. While it's usually fairly easy to strengthen the firewall by pinning it and epoxying tri-stock to the back side you can't tell if anything needs to be done to the rest of the fuselage because of the covering.

With these points taken into consideration there isn't any reason why you couldn't put a larger engine on the plane.

Hope this helps

Ken

I put an OS .25LA Blue in a Model Tech Mini Magic Extra 300 and it's a blast. I only had to put my battery pack behind the LE of the wing to bring it into balance. I used a 5 cell 1100 Mah NI_MH pack. Everything else is in the stock location. This plane is very close in size and weight as the one you describe. 900 X 900 and 1100Grams.

Most of the time I fly about half thortle, but point it up and power up it is unlimited in the vertical. What a hot Rod.
Only catch is I am using the stock tank, and that baby drinks up the fuel, so 6 minuets is about it.

Hi again,
I would like to thank everybody here for giving me such a informative suggestion. I believe I'll go with the .25 engine. There's actually nothing much to worry as I'm very sure there'll be help here if I run into any problems.
Thanks once again.

I stuck an OS .46LA in a Model Tech 300 which calls for a .25.

I had the engine, and was looking for a plane to install it to, other than a trainer.

The OS .46LA is about the same weight as the .25 so it fits the plane well.

Its perfictly safe dont worry about... no sirously ppl at my club but planes what call for .15 and stuff .46ax and you have an instant race plane. (lol just watch the landing if you do this) and it maybe a good idea to program you remote so that it can only slowly increas trottal(iv seen fuses riped apart in midd are because the rpms enreased to quickly)