Hi there ...

How can we tell that this model or plan is designed for this size of engine (e.g. .40ci can handle this model) ?? is there any equation and tables to be followed or just need some experiences to judge ?.

Mishal

i beleive thats usualy given wiht the plane, but from what i have seen a little experience and judgment is needed in selection to...

Most planes list the range of engines suggested by the designer. If you don't know you are usually best to stick with one of them. I find that the largest engine in the selection is usually good. Once you get more experience, you can change it based on what you want to do. I have a dynaflite PT-19 for instants. I wanted to put a larger gas engine on it and most said don't do it. I have been flying for many years, so I asked all the people I thought would be able to help me decide. I disagreed with them all unfortunately and put the engine in it I wanted to. It was the US 41 CC gas engine. Many said it was too heavy and wouldn't fly it.

To make a long story short, I am glad I didn't listen and did it anyway. It is one of the best flying planes I have and a blast in the air. It will climb almost vertically and almost hover.

The jist of it is, once you gain knowledge of the planes and power plants, you will know more of how to pick larger engines if you want them. You can do just about anything you want with the hobby. The more you learn, the more you can do.

Hope that kind of answers your questions. When you are starting off, its best not to over power. Later when you get better, you will find that sometimes, over powering some birds can be a blast, while others would be bad over powered.

Hhmmm .. i see .. thanks for the valuable reply

Mishal

Mishal, have to agree with Flyboy. The key is to get the largest powerplant the airframe will handle safely, without adding too much weight to the airplanes wingloading. You can always throttle back, but if you really need more power and it's not available, you can have a real problem. Where we fly (Texas) it is almost always windy and gusty. Our site has many trees, bushes, large hay bales, etc. All of this can add up to some real interesting landings. An underpowered airplane can easily become out of control and end up in the pits, or hurting someone if you experience turbulance on final. I have seen more problems for new people with underpowered planes, than ones that had a good power reserve. We are not saying to put a .60 size motor on a .40 size airframe. What we are saying, is that if the airplane has a .40 to .46 range, opt for the .46 or even a .50 or .52 (that weighs the same as the .46). The extra power will be nice on really hot days, when air effeciency isn't so great for the engine or the wing/control surface effectiveness.

Wish someone had given me this advice years ago. it would have saved me allot of heartache and frustration.

Happy Landings.

Agree completely with the above posts! [8D]

btw, if you are designing your own plane, you should look around on the web for planes that are simular in size, weight, and designed use to yours, and use that as a starting point for your engine selection. It's not foolproof, but it can be helpful.

Yeah that makes sense but we need also to consider the cost factor in this case. Anyhow i was seaching for more information about this subject and found some interested summaries and conclusions, below is a table of recommended engine size vs. wing area.
For more details check this GREAT [link=http://adamone.rchomepage.com/design.htm]Link[/link] <== good for beginners (like me)
Hope this will help


Thanks guys for your replies

Well, take that chart with a BIG grain of salt. It depends on a lot of other factors. I have a plane that is powered by a .15 and has 604sqin.

It's not a powered glider either, it's an RC Combat plane, and very competitive, faster than you'd expect, and turns amazingly fast due to the light wingloading.