Thanks- sometimes I hit the target

All of those things and other details like cooling drag, antennas (can put a lot of them inside the skin on a fiberglass airframe), not to mention pusher propellers have the disadvantage of being in the wake of the airframe... it will be an extraordinary accomplishment—and a heckuva lot of work—if they pull off those kinds of numbers in the end. I'm still in the camp that it looks a little too ambitious.

I approached the calculation kinda backwards by starting with horsepower. I also didn't apportion any of the total drag as induced drag, I didn't get into propeller efficiency, nor did convert it into L:D. Just purely pushing a physical object through the air.[/quote]

That is brilliant. Nice job. Kinda gets back to my main point. Boundary area laminar nose and body flow (i.e non turbulent flow across the frontal area/wing root) and the transition through the wing root on this bird is what I believe the implications of which are being misunderstood.[/quote]

The other thing I have been pondering and can't quite get my arms around is what percent of fuselage itself will act as a lifting body, and to what effect and at what speeds. Given laminar flow across the whole body this has drastic implications as it reduces induced drag on the wings. Especially as airspeed winds up.

maybe missed this page

viewtopic.php?f=49&t=123165&start=285

viewtopic.php?p=2056452#p2056452

All of those things and other details like cooling drag, antennas (can put a lot of them inside the skin on a fiberglass airframe), not to mention pusher propellers have the disadvantage of being in the wake of the airframe... it will be an extraordinary accomplishment—and a heckuva lot of work—if they pull off those kinds of numbers in the end. I'm still in the camp that it looks a little too ambitious.[/quote]

You pay either way right? Either turbulence inducing frontal flat area for cooling (massive increase in parasitic flow across the whole airframe) in a tractor traded for clean air for the prop to bite, or some degree of turbulent flow in a pusher, but you get the aforementioned benefits.

My thinking is the reduction in induced drag on the wings/lift created by the body FAR outweighs the penalty of prop bite... especially on the out 2/3 thirds of the prop throw. Which is "where the rubber meets the road" so to speak. ESPECIALLY at higher speeds which is where the polar on conventional configurations drops off a cliff.

I am optimistic.

Thanks. I did. I am new.. :-) Is this what you are referring to?

"Yes, but his math still doesn't add up. I asked him to show his math, but he brushed me off. He thinks all he has to do is maintain the same horsepower at FL250 that he has at sea level for a given IAS, and he'll be able to achieve the same IAS at FL250 as he can at sea level. And since the same IAS at FL250 translates to a much faster TAS, he thinks he'll get all that extra speed for free. That's not how it works. Even if he can maintain the same HP at FL250, the thrust in that thin air will only be about 60% of what it was at sea level. No way he's getting even his claimed 262 KTAS at FL250, even if he achieves his claimed 15% drag advantage over the Cirrus, and that's a big if!" ???

Yes, while keeping clear of it by about 93 million miles, give or take. More like an ellipse.

Thanks. I did. I am new.. :-) Is this what you are referring to?

"Yes, but his math still doesn't add up. I asked him to show his math, but he brushed me off. He thinks all he has to do is maintain the same horsepower at FL250 that he has at sea level for a given IAS, and he'll be able to achieve the same IAS at FL250 as he can at sea level. And since the same IAS at FL250 translates to a much faster TAS, he thinks he'll get all that extra speed for free. That's not how it works. Even if he can maintain the same HP at FL250, the thrust in that thin air will only be about 60% of what it was at sea level. No way he's getting even his claimed 262 KTAS at FL250, even if he achieves his claimed 15% drag advantage over the Cirrus, and that's a big if!" ???

It's those unfortunate "laws of physics" again. Even with equal drag and horsepower, maintaining the same IAS will go down because while thrust equals drag, horsepower equals thrust times velocity (i.e. TAS). It's things like this that make me less optimistic about the Raptor's claimed performance.[/quote]

Help me out here... are we talking loss of engine HP output due to density altitude or something else?

Help me out here... are we talking loss of engine HP output due to density altitude or something else?

Help me out here... are we talking loss of engine HP output due to density altitude or something else?[/quote]
No, the incorrect premises was that if engine could produce the same power at a higher altitude, the increase in TAS over IAS due to the thinner air at the higher altitude would provide an increase in economy and range.

Technically the horsepower I referred to is "thrust HP" which is the engine's power output multiplied by the prop's efficiency. And Thrust HP for a given IAS does increase precisely with the TAS obtained at higher altitude. This is why maximum range in cruise flight is completely independent of altitude if you ignore wind. And ignoring the minute prop efficiency variations of a CS prop at different altitudes the power required for a given IAS increases at almost the exactly the same proportion as the increase in TAS when you cruise at a higher altitude.[/quote]

Got it. Thank you. But I think I take issue with part of what you said.. Maybe I am doing so because I am wrong, and if so would love to have you straighten me out.

But I need to take this step by step given we are working with 4 variables and several assumptions...

1.) Thrust HP
2.) Prop efficiency at a given altitude
3.) L/D polar for given airframe given any given IAS (We agree polar is independent of altitude yes? Given IAS is the measuring stick? Will assume constant weight so polar does not %#$@ along velocity axis of graph.)
4.) TAS given any IAS as computed using known static air temperature and pressure altitude.
5.) Assuming a still air mass.

That being said.....

Can I correctly summarize what you said above by saying if we graph the inverse polar of the airframe (i.e combination of induced and parasitic drag) maximum range cruise is simply power required to maintain best L/D, or the tangent on the polar as it originates from the graph vertice? Power being the Y axis and IAS being the X axis.

Thanks
--Chris

Just watched his update for today. Guess what he added a few more pounds. He found out he needed a bigger fuel pump. Decided while I am here it would be nice to have a cut off vaulve so working on stuff like this is easier. Gotta run some bigger wire to the bigger fuel pump. All I keep thinking is all the ounces are adding up man. This thing is already to heavy. And its not painted, missing back seats and other stuff too. I sure hope he can get the extra HP he is hunting I have a feeling he is going to need it.

There’s an apropos saying in hiking. “Ounces lead to pounds and pounds lead to pain.” I’m rooting for him but the physics aren’t looking positive at this point.

I guesstimate this airplane will climb at 700FPM and go about 160kts until the engine quits. I'm a raving fan of experimental airplanes but this is simply not a good design.

I think the main issue I see is the fact that he has made claims that are not possible.
Dreams are great, and people should dream and go further.
But in a field like aviation, where the most brilliant minds have been after improvements for a long time, it is difficult to make those incredible claims...
This guy is dangerous, and having people invest in his venture is ridiculous.
Unless he intends to move to a different planet, where the laws of Earth's physics don't apply, he is going to kill himself.
Gravity is a