speedracerntrixie

My Feedback: (29)

Well once again I'm sure I will be pointed out as wrong but here goes, in the example of the boat. My understanding is that if you intend to go to point B from point A and there is a current and you want to make a single heading change to accomplish this then you are going to have to overshoot your target to allow for current drift. Thus the path traveled is going to be an arc. Again this is not guessing nor what I have read in a book. This is first hand experience spending many hours piloting a 18.5 ft boat in the SF Bay and connected bays and sloughs. Piloting an object in any fluid would be the same.

This brings up another question, just how much rudder are you guys in visioning me holding in a cross wind?

Final thought on this post. You guys want to come here bashing Sensi and myself for chest bumping and such but you are the guys in a beginners forum posting complicated vector formulas and such that are clearly going to be over the head of 99% of beginners heads just because your ego won't allow you put yourself in the shoes of an R/C pilot with 35 years hands on experience. Think about that will ya.

cfircav8r

My Feedback: (1)

It's simple, you are crossing a river that is travelling at 5 kts. You are motoring at 10 kts. If you want to travel directly across the river you turn 45 degrees up river. Now 5 kts of forward speed is countering the current and 5 kts is taking you across the river. Simple geometry. Straight horizontal line across the river and a straight diagonal line through the water. No arcs. Just because you have learned techniques that give you the visual look you want in competition, doesn't mean you actually understand what is happening. I know a very successful shooter that honestly believes that the bullet initially climbs when it leaves the barrel then starts an arc down as it slows (loses lift.) This misunderstanding doesn't make his ability to shoot accurately any less real.

Top_Gunn

My Feedback: (6)

So you're saying it's impossible to fly a straight line from point A to point B in a crosswind, or to steer a boat in the same sort of straight line in a constant current? That's just not right. It is probably true that in a real stream, rather than the ideal one we're imagining, you are likely to follow a curved path, because the stream will not really have the same velocity near the shore as it has in the middle, and because you never know the exact speed of the current and so guess at your initial heading and change it when it's off, as it usually will be. In the ideal conditions of the example, though, the boat will go in a straight line right across the stream. And planes fly straight lines from one place to another in crosswinds, by crabbing, without following curved paths and without holding, or even changing, rudder positions, except when the winds differ from the forecasts.They do it every day.

None of this is advanced in any sense. It's the sort of thing you learn on the first day of instruction in dead reckoning. Every full scale pilot has to know this stuff to get a license. Denying it is pointless.

Your 35 years of hands on experience has surely made you a skilled aerobatic pilot. Nobody questions that, and nobody is "bashing" you. But, as Sensei himself is fond of pointing out, with sufficient practice you can become very good at aerobatics without ever learning even the basics of how an airplane flies, or elementary facts about the effect of wind on airplanes. I know some RC pilots, whose flying looks great, who believe that turning downwind causes a plane to lose airspeed, which is the dumbest myth in the book, but they can fly models spectacularly. In the very small spaces we fly in, while making constant corrections, that sort of knowledge isn't absolutely essential. But when people ask, they should get the right answer, not just a guess.

Rob2160

I totally agree with your reasoning and explanation, but for the sake of being pedantic you would only turn 30 degrees in this example. Cosine 30 = 0.5 (0.5 of 10 = 5) so 30 degrees offset is giving you enough upstream component (5Kts) to compensate for the 5 kt current.

cfircav8r

My Feedback: (1)

Noted. My Whiz Wheel is packed up right now and I didn't want to dig it out, and I suck at math. Thank nerds for calculators and "navigation computers"

Rob2160

LOL, I have carried my Whiz wheel for 30+ years and have only used it operationally once. It looks the part though.

Bozarth

My Feedback: (15)

Hey, that's how I site my rifles in! Any angle above horizontal and your buddy is correct. Any angles level or below, and your are correct. What is the big point of confusion? I don't agree with his "lift" idea, just gravity, if that is what you are talking about.

Kurt

speedracerntrixie

My Feedback: (29)

First I never said that you couldn't fly from point A to point B in a strait line. I simply stated that you could not do it the way you have described. In a perfect world yes the math works but my friend the world in which we live is not a constant.

as a side note, I went flying today and took the kids trainer, a Hangar 9 Arrow. I flew all approaches with crossed controls and had no issues with doing so, the airplane showed no ill effects whatsoever. Now would I suggest a beginner fly around like that? No, but I would not consider it wrong either.

cfircav8r

My Feedback: (1)

No he believes it rises from the barrel, not that it is pointed up. This is basically the same picture he uses to show how it works. If you notice the rifle is being held level yet the bullet trajectory first rises then starts to fall. His picture came right from a hunting mag so it is gospel to him. While the picture as presented is wrong the information they are presenting is right.

speedracerntrixie

My Feedback: (29)

Good we have started talking about guns now. I never would have thought that by firing a handgun by waving it that you could make the bullet curve. I saw it once in a movie. LOL. Please do not get a rope and look for a tree guys, that was what we call humor. May not be very good humor but humor none the less.

Bob Pastorello

My Feedback: (198)

Please don't tell me that there is someone, somewhere who actually BELIEVES that a round/projectile fired from a horizontally-pointing rifle (parallel to the earth's gravity) actually RISES before it starts it's decaying arc?

speedracerntrixie

My Feedback: (29)

Now Bob you know darned well that we have been told that once an object is in motion at the correct vector that it will not arc. I'm betting that the bullet doesn't feel a cross wind and thus wind is not a factor just the same as wind correcting off the third tee would be pointless as well.

Again guys humor, this thread needs some levity

cfircav8r

My Feedback: (1)

Yes, there is. It has been a few years and I no longer live there (Tulsa,) but he was convinced that it worked that way. My point is just because you compete at a high level does not automatically make you right. I believe what Speed is trying to convey is absolutely correct for the flying he does with the aircraft he fly's, but that doesn't make it right for the reasons he is claiming nor is it necessarily right for a beginner.

I went to a well established flight school with a degree program. The emphasis was on making everyone that graduated a top notch flight instructor. The curriculum focused on aerodynamics and the classroom lessons were coordinated with the flight instruction. The lessons being learned in class were then tested in flight and you could see and feel first hand what was happening. Speed claims that models are different yet all aircraft regardless of make, model or size are different. There is however nothing you can do with a model that doesn't fall in line with what I have learned in my education. On the converse there are many things I learned in flight school that not every plane can do.

JPerrone

I recall many years ago there were quite knowledgeable people in the shooting world who eloquently explained how the rotation of the bullet caused lift.

This might have been completely wrong; but these people did sound knowledgeable, the so called science sounded plausible, and people did believe it.

Didn't necessarily make it right. However, regardless of whether the bullet has lift or not, many trajectories need to have some rise in them in order for the bullet to reach the target. And that path will look like the bullet goes up some, then comes down.

Regards

bjr_93tz

Actually, I'll probably get flamed for this but I was told by a competitive target shooter that a bullet tends to travel in a corkscrew flightpath due to the spin and other influences. The length of the barrel, the angle if the rifling and number of complete rifles over the length of the barrel can influence which part (rising, falling, left or right) of that corkscrew flightpath the bullet leaves the barrell on. Apparantly it's obvious if you rotate the barrel through 90 degee without changing it's angle because the bullet lands somewhere else??


Now I don't have a clue if that's true, but a competitive shooter with throphies beleives it to be true and I don't know any better so tend to take that on face value.

And that golf ball is slowing down, which behaves just like I explained on a previous post. It's no mystery.

speedracerntrixie

My Feedback: (29)

My my issue with the application of full scale education is that it revolves around aircraft with far less power to weight ratio the the average trainer and much more power that are operated in an environment ( altitude ) and in most cases higher airspeed ( velocity ) not to mention much higher wing loadings. IMO the outside environment has a much greater effect on our models then it does on any full scale aircraft. Therefore piloting techniques can be and for most model pilots are different. Now if any of you guys had formal education that relates to full scale airplanes with power to weight greater then 1:1 with wing loadings in the 25 oz per sq ft I'm all ears.

dabigboy

Getting back to the OP, it's worth mentioning that on many aircraft, it is necessary to hold opposite aileron in a steep turn to prevent the plane from rolling more into the direction of bank. This is because the outside wing is moving faster through the air, hence more lift. I have noticed it most in high-wing, non-aerobatic types (Cessna singles, mostly). "Sporty" aircraft like the Grumman low-wing designs aren't as noticeable. I will say that I don't notice it much on RC aircraft. I think part of the reason is that our planes tend to be light and over-powered, and generally fly very fast. This all means the plane tends to not rotate about its yaw axis as much when in a bank (especially sport and pattern aircraft). To see the other side of this coin, try slow-flight in a real plane: very shallow bank angles result in surprisingly fast turn rates. The plane will also tend to try to roll into the turn on you (again, varies somewhat by aircraft type).

I seem to recall this roll issue is less pronounced on aerobatic types, such as the Decathlon (semi-symmetrical airfoil, very little dihedral)....although it's VERY noticeable during hammer-heads.

Matt

bjr_93tz

I'm not really sure what issue you have? I agree we fly RC planes differently and there's no real reason to make a course correction in a full size with just rudder. The only reason we do it in RC is because it looks smoother and we don't get too much of a point deduction for doing it that way.

RC glider guys occasionally discuss the use of rudder in thermal turns (some DLG's just use a fixed fin with no rudder) and at the end of the day with a glider it's pretty much always better to be slipping and sliding (even with the odd tip stall) your way around a turn in lift than to perform perfecly co-ordinated turns in sink...

cfircav8r

My Feedback: (1)

Again you completely miss the point. You primarily fly planes that are tediously set up for a single purpose, to fly IMAC routines. Ok, maybe some trainers or sport planes occasionally, but I would guess you still spend the time to set them up for your flying style. You also often make the statement that we don't have to put up with the "issues" of full scale like the need to change elevator trim with speed changes. The same holds true for cars. I drive a Chevy Cavalier and it has some body roll in turns and the steering is soft (not loose,) but I don't have to put up with that if I just spend the time to set it up better. It would then have nice responsive steering and firm suspension for solid contact to the road and great feedback through the steering. Try driving that every day for long distances, it would get old real quick. Not what I want to do, also if I am inexperienced it could lead to over controlling and accidents.

While you can get away with a lot, due to the low wing loading and high power, basic knowledge will prevent simple mistakes. Mistakes like when the left wing drops during a stall trying to roll right with the ailerons instead of dropping the nose and using rudder. Models can have the very same issues at times and, even if it is rare, knowing what is happening and why can prevent disaster. Yes models have a much greater envelope, but at the edges lay in wait the same demons.

sensei

Quote:

Originally Posted by Top_Gunn

So you're saying it's impossible to fly a straight line from point A to point B in a crosswind, or to steer a boat in the same sort of straight line in a constant current? That's just not right. It is probably true that in a real stream, rather than the ideal one we're imagining, you are likely to follow a curved path, because the stream will not really have the same velocity near the shore as it has in the middle, and because you never know the exact speed of the current and so guess at your initial heading and change it when it's off, as it usually will be. In the ideal conditions of the example, though, the boat will go in a straight line right across the stream. And planes fly straight lines from one place to another in crosswinds, by crabbing, without following curved paths and without holding, or even changing, rudder positions, except when the winds differ from the forecasts.They do it every day.

None of this is advanced in any sense. It's the sort of thing you learn on the first day of instruction in dead reckoning. Every full scale pilot has to know this stuff to get a license. Denying it is pointless.

Your 35 years of hands on experience has surely made you a skilled aerobatic pilot. Nobody questions that, and nobody is "bashing" you. But, as Sensei himself is fond of pointing out, with sufficient practice you can become very good at aerobatics without ever learning even the basics of how an airplane flies, or elementary facts about the effect of wind on airplanes. I know some RC pilots, whose flying looks great, who believe that turning downwind causes a plane to lose airspeed, which is the dumbest myth in the book, but they can fly models spectacularly. In the very small spaces we fly in, while making constant corrections, that sort of knowl90edge isn't absolutely essential. But when people ask, they should get the right answer, not just a guess.

What makes you think that I don't know the basics of flight or the effects of the wind during flight? I have never stated/chest pounded in any thread what my complete background is, my formal training has been, and what all my qualifications are to date, so you are now making assumptions and you know what they say when you ass/u/me... What I have actually done for years in the hobby side of my life is shared documented build threads of my kit lightening concepts, and my scratch built lightweight designs, and in more then one forum, I then post my own flight videos in support of the those lightening concepts while pushing the airframes to the limit in some cases and in wind up in the 35 to 40 mph area as illustrated in some of my videos. Take guys like you that hang in places like the beginners forum and boast about your alleged qualifications, your alleged 20 + years of training beginners, and your bla, bla, bla, whatever the case may be, then when asked to share something we can see... Well, nothing but silence or deterrent tactics of the question as illustrated by your lame jab at me because I/we are still waiting for evidence of your dance...

For the record I didn't get into that wee wee match with you guys in the dumbest downwind turn myth thread because to be perfectly honest, who gives a rats... I say just shut up and fly, oh and guess what, on the vise versa side of your post; I know guys that have been flying 20 + years, can quote all the basics of flight from their keyboard, but when it comes right down to applying what they know, and I use the term know loosely during flight, it just doesn't happen because their entire $10.00 of attention span is already spent holding their breath while circling the field and trying to get back on the ground in one piece and more importantly, possess the ability breath and type smoothly again. Does this in any way sound familiar to you stud.

Bob

bjr_93tz

You don't have to hang out in the beginners thread, you see it pop up on the homepage as most active, see sombody's written something wrong, and try to point that out with a reasonable explanation why.

Then you get attacked for being a keyboard warrior and your flying experience is called into question because the real world "experts" have never seen you at their local field where they'e the big fish, and can't figure out who you are.

BTW I've only got 733 posts, hardly a keyboard warrior..

Calvinman

As to BJR's comment of a bullet traveling in a corkscrew path, I tend to agree with that. As a lad I had a 22 cal pellet pistol with such a low muzzle velocity that you could see the pellet fly, and it sure did have a corkscrew trajectory. I think the illustration of the hunting rifle and the targets may also be because you sight your gun in to be accurate at a certian range. So the bullet when it first leaves the barrel which is of course lower than the scope but since it is on its way up so it will have dropped to the target the second target gets hit high.

Calvi

JPerrone

It sounds like I missed a really entertaining exchange about airspeed!!! I'm not really much interested in stirring up a hornet's nest, but I am curious about that. And I don't think I have any preconceived notions about what the right answer is.

Lets start with airplane A, flying 30 mph, IN NO WIND. His ground speed (speed relative to the ground) is 30 mph and because there is no wind, I think his airspeed should be 30 mph. Maybe it isn't I'm sure someone knows!!!

Now, same airplane, same ground speed, but wind is 10 mph on the nose. This makes the airplanes airspeed 10 mph higher, so it is airspeed is 40 mph, for the same 30 mph groundspeed. Again: maybe this is wrong, etc

Now, starship Enterprise (the real one NC 1701 not 1701A, B, etc) swoops in and teleports the plane 180 degrees the opposite direction!!! I think because of conservation of momentum the plane has to be going 30 mph relative to ground; but it's airspeed must now be (30-10) = 20.

When you turn a REAL model or REAL plane, it cannot make this instantaneous change in direction, so maybe there is a "conservation of airspeed" but this would imply a change in ground speed. Hmm, wonder if there's any way to confirm/deny that?....

Now COMPLETELY ignoring any theories etc, what I observe when I'm flying my little models (they seem to react more than the bigger ones) is that they go a certain speed into the wind (call it "50 undefined units of speed") and when I turn around, flying in the direction with the wind, they slow down to 20 or 30 UUS. Ground speed reducing. This speed is from my frame of reference, so I think that is ground speed.

I think that means that the airplane tries to maintain airspeed, with a resultant change in ground speed.

Is that right?

Regards

Top_Gunn

My Feedback: (6)

Never said you didn't, Bob. If you'll take the trouble to read what I said, you'll see that I was agreeing with something you've said repeatedly.

bruceal

This is off topic, but can anyone tell me how to start a new thread? I also checked Flying Giants to see if I'm missing something being that they are pretty much the same.