Matching an Engine with Airframe? How do I know?

[fencelake]

I'm purchasing an airframe, and I currently own a DLE 55. So far in this hobby, every plane I've owned gas, nitro, or electric has had more than enough power, but is there a way to know basically what my all up weight will need to be or something like that to know if I can use my DLE 55, or I need to buy something else. As it stands... I'm just going to mount it up and fly it. Just curious! thanks!

 

[ExtraJohn]

This is something I have done some looking into.

There are static thrust calculators that will give you an idea of what to expect from your planned combinations.

I feel that by properly matching the weight/thrust of the engine to the airframe is the best way to go.

If you have an engine that will produce the desired thrust, and it weighs a pound plus less then a more powerful engine, the only thing the extra power is doing is hauling around extra weight.

 

[fencelake]

This is something I have done some looking into.

There are static thrust calculators that will give you an idea of what to expect from your planned combinations.

I feel that by properly matching the weight/thrust of the engine to the airframe is the best way to go.

If you have an engine that will produce the desired thrust, and it weighs a pound plus less then a more powerful engine, the only thing the extra power is doing is hauling around extra weight.

So, if I know the static thrust of the DLE 55, for example, if the plane weighs less than the the static thrust, by some amount, I oughta be good? It's a bigger plane than what the engine is in now, but it should weigh close to the same or maybe even less because it's newer.

 

[ExtraJohn]

In a nut shell, yes.

I use the static thrust of the prop at X rpm.

For my H9 CAP, they called for a 1.8 4c glow as the max engine, I found a lighter gas powered engine that matched the performance of a Saito 1.80, and by moving the servos and stuff around, I was able to get it to balance out with no additional weight, not looking for 3D and unlimited vertical, just decent scale performance. I came in at 12.3lbs dry.

 

[fencelake]

In a nut shell, yes.

I use the static thrust of the prop at X rpm.

For my H9 CAP, they called for a 1.8 4c glow as the max engine, I found a lighter gas powered engine that matched the performance of a Saito 1.80, and by moving the servos and stuff around, I was able to get it to balance out with no additional weight, not looking for 3D and unlimited vertical, just decent scale performance. I came in at 12.3lbs dry.

Sweet, so I found some numbers, on the DLE 55, and they're over what I'm anticipating the weight to be with the prop that I currently have on it. What would change the performance via the prop? Larger or smaller diameter? Or increased or decreased pitch?

 

[Terryscustom]

DLE 55 is pretty good for 16lb. range planes and likes Falcon 23x8W or similar props very well. Best bet depending on your flying style if you are looking at static thrust is for plane RTF weight to be half or less than the static thrust.

 

[ExtraJohn]

That would be a really long discusion and lots of theory.

 

[pawnshopmike]

I just copy what works well for others.

 

[fencelake]

Well... I guess I'm going to put on my Chuck Yeager hat and just hook it up and see what happens! I fly IMAC mostly and this is going to be a backup plane... My main concern will be verticals... but really geez these engines are so powerful... I'll bet it's plenty.