Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Dexacare, Mar 28, 2016.
Does this mean that Cirrus can stop worrying now?
Think about where the CG is likely to be on the Raptor. Then think about the all of that profile area in front of the CG due to the deep fuselage profile, the profile area behind the CG, and the relative moments of those areas. The design has two large vertical stabilizers, but there's no telling if those are enough, especially given the weight creep and the probable location of much of that excess weight.
Yeah, test flight is the only way to know. I was reading some articles about the Dutch roll problem on wiki. It said sweep-back makes it worse. Didn't say how to correct the problem other than a yaw damper. Can be fatal if wrong.
I did some upgrades on a turbine goose conversion with a two foot extended forward fuselage. The owner said it had no directional stability until they put VG's on the vertical tail.
I read the specs for the Raptor today. The range is most impressive. It tells me that the glide ratio is above 25:1. Maybe Peter does have some value in the design, while the glideratii here will be yawning, thats a very good glide ratio for something that shape.
Since a Long-EZ has an L/D of about 15:1, and a COZY MKIV has an L/D of about 12 - 13:1, and a Velocity is about the same or a bit lower, even with retractable landing gear there is essentially zero chance that the Raptor has an L/D higher than a Long-EZ.
But you already knew that, right? Just as you know that that particular specification is no more accurate than any of the others...
Hmm, maybe you could be verrrry careful with your airfoil selection and fuselage shape (area rulz!) and use an extra turbo to draw air from the right places to provide active laminar flow control and so forth with RGB LED lighting and only add about 500lbs of extra weight!
Watch out Cirrus!
I am pretty confident that Peter used the calculated L/D coming out of the program. When I first designed the Beast One, I got predictions for an L/D of 35 and both my test pilot and aerodynamicist called it bullshit. So I tried to use Solidworks CFD to calculate again and it was even worse. Nice for identifying problem areas, but not to use for proofing numbers.
In the end we switched to calculating the competition with the same tool and comparing the results with their specifications in order to get meaningful values.
I'm not will talk about other technical problems with this airplane, but I see problem with prop clearness. How RAPTOR can land, without destroying the prop and power plant? What I see, there not mach clearness for the prop for the landing. 12" nose wheel UP, will give this airplane not normal angle for landing.
What is normal angel for landing this aircraft? At 10 degrees of angel, prop will strike the runway.
Even our aircraft designed to have 18 degrees nose up on landing.
From the design page of his website, he appears to be unaware of induced drag. That would explain his numbers nicely...
Yep, in the unlikely event that this gets flown, a prop strike ia going to happen sooner rather than later.
This(prop strike) will happen in the first landing - remember that.
If not the first take off...
This thread has been a single-source educational opportunity for people like me. Even as ignorant as I am about aircraft design, I can see so many obvious issues.
Therein is my personal fear; the unknown.
Several years ago I paid a contractor 25k to correct a multitude of construction errors made by my home's builder. When he finished the job he advised me to sell ASAP. I asked, "Didn't you just fix my home?"
"Everything I could find. It's what I couldn't find that scares me."
Peter has his hands full with a long list of obvious issues, items that should have met proper design criteria before installation. That flexing of the aileron pulleys, as an example, is purely poor structural design. Who can possibly know what lies beneath the obvious.
It should never fly.
It's interesting to read some of the first posts on this thread. I thought one of depositors said Peter had taken over this project. Not sure who started it.
I suppose someone could buy it now and throw out the engine and AC and try to make it fly.
I also suspect that it is a deathtrap. From what I've seen Peter does not know enough to design an ultralight.
This project needed the eye of a competent person all the way though. What it got was an IT guy and his lackeys.
I've done IT work. Never had a problem with deadly bugs! The "We can iron out the bugs later" mindset is completely wrong for building an aircraft.
I looked at the prop clearance too and it seems to be similar to the Velocity. Something you always have to be aware of on rotation and in the flare though. That MT prop has to be close to $20K.
A prop strike on rotation could save the life of a test pilot, or Peter. $20k well spent.
Hi, to get glider like L/D takes a glider like planform. The Voyager had that kind of L/D. The EZ planform is not one you would chose when designing a normal GA aircraft for max L/D with its higher loaded canard surface and swept main wing. It can be a reasonable choice for a high speed cruiser. For efficient high altitude cruising the design needs to be more glider like. Think of airliners and B-52 which have swept wings only because they are transonic. A better example is the U 2. If you have huge power, you build an SR. An SR pilot made an interesting statement when asked how fast it could really go. That is still secret so he said, "Whenever he needed it to go faster, it would."
There are many questions I have about their powertrain. Putting a new engine in a new airframe has often led to program failure.
It looked like the distance between the prop and engine was large. So the prop might be more aft or the engine is more forward.
I know nothing about CFD, which might spit out wonderful numbers to unsuspecting dilettantes, but I do know that L/D depends on things like W/S, Cdo, and K (which in turn depends on Oswald), so there is lots of room for optimism until it is displaced by reality. Of course you have to have either a tow rope or an engine that works to find out.
The programs " Lackeys" are far more competent than most of the critics here on this thread( no insult intended). However the IT guy thinks he knows more than everyone
( Cirrus,Piper,Beech,Velocity,for example) and rarely listened to advice, suggestion, and even argument. Borrowing from modern phraseology to relate to all the problems herein, Peter " OWNS IT" all.
Separate names with a comma.