helicopter project

at about 3kg /m or roughly 6lbs per yard the thick walled rectangular mild steel tubing is about ideal aviation material.

"IT IS MADE FROM 2" X 1" X 3MM MILD STEEL TUBING"

 

Probably the most misguided back-yard project you could imagine. Can only end in tears.

 

put a long handle on it and make a big garden trimmer.

 

Quote

I queried YellowJacket about this rule of thumb and this was his response:

With his permission to Copy and Paste,

"It depends on a lot of parameters, mostly the rotor tip speed and diameter. Bigger rotors with higher tip speeds can hover more weight/hp than smaller rotors for a given hp. If you want to hover with a small fan it's going to take a lot more power than if the aircraft has a big rotor. A generality like 1hp/5 pounds isn't going to apply broadly, it works for a specific rotor speed and diameter, so, while you coud find some helicopters that it worked for, you can just as easily find different data.

For example, if you look at the Bell 407, it has about 700 hp and has a gross takeoff weight of 5250 pounds, so that is more like 7 pounds per hp. The old Bell 406 had a max power of 315 hp and could hover about 3200 pounds, so it was closer to 10 to one, but it was a pretty anemic aircraft. So no, you probably don't need 1 hp/5 pounds of weight, you can do it with a lot less, provided the rotor loading is lower.

Also you need to consider altitude and air temperaue. High and hot, (like 4,000 ft and 95 degree day) is a lot worse than sea level standard day.

Like I said, you can probably find helo's with the rotor loading to match the data, but you can easily find others that won't. Bad rule of thumb unless you qualify it with rotor loading and tip speed.

It's kinda like somebody asking how fast a boat weighing x pounds will go with given hp. Unless you know the length, beam and deadrise you probably aren't going to be close to right. A underpowered short skinny deep v hull isn't going to plane very well, but a wide flat bottom hull might plane off and move right along on the same power to weight ratio..."

He then added:

"I did happen across another data point, the new Sikorsky 434 has a GTOW of 2850 pounds and has 320 hp, so their power loading is 9 lbs per hp. Seems like that's a more common power loading than 5."

-Tom