F4J Phantom Cat Shot
richard.chaos_91798ec102
Posts: 0
Needs refining and some more section they are rendering! But there ya are!
PLEASE GO SEE ANIMATION AT
F4_project_tag.jpg
576 x 434 - 218K
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Comments
Good job. The accel from the cat should be much more intense than you've shown. A naval catapult takes a plane from 0 to 160mph in just under 2 seconds in a distance of ~80m.
EDIT: Just in case you don't want to do the math: acceleration is approx 30m/s^2 (depending on various factors it can vary from 28 to 32 m/s^2). Also, some of the newer cats take the jets to 174mph in ~2.4s instead of 160 in ~2s.
Kendall
Good work. I enjoy creating animations, but I have never been able to get interested in modelling. Thank goodness there are talented modelers like you who make their creations available to the rest of us, some very affordable ...
Well I am going blind doing it! Starring in this damn radiation box all day and night. I enjoy modeling and to a lesser extent doing the animation. Like on this! In this animation its not on there as it JUST got done rendering of a shot from behind the F4 as it take off the ship and I was using a MOTION path and wanted to to DIP down a little as it left the carrier then OTCH UP a ltitle then gain altitude BUT the transition was like to ran over something. I tried for 2 days to iron it out then just settled on having it fly almost i n a straight line off the ship!
Actually, the F4, like the F16, is light compared to the F15 and FA18. Depending on the carrier (deck length), the power of the cat, and the wind conditions, it is entirely possible to lift off the deck before it ends. In these cases, you won't get the "drop" that is so evident on the larger aircraft. You can sim this by having the jet start to lift at about 1.2-1.5 secs into the launch as the lift of the wings starts to support the weight. Raise the attitude of the jet on the gear to fully extended at 1.2 and start lifting the front tire at 1.5. Keep in mind that the cat shuttle and bridle will act as a weight holding the nose level instead of allowing it to cock up. At about 1.8 seconds (200m or so) the lighter craft will start lifting the fuselage. At this point it is possible for the bridle to release and allow the jet to climb, but not many pilots have the reflexes to start the climb this early as the Gx is still excessive. On an 80m deck the jet will be airborne right at 2s as the deck will have ended; on a 95m deck it may take around 2.1s for a lighter craft to lift. The heavier craft will not lift until around 2.4-2.45s when the deck will have ended.
For your animation, (assuming motion of launch along +X) the critical part is that the jet will go from stop to dX=30m in 1second. After that you're probably going to be seeing the jet from an angle where it is easier to hide "inaccuracies." Since the "Top Gun" era, folks are used to seeing the initial impulse from the cat. With so much reference, anything "slower" will look "wrong".
Kendall
Actually, the F4, like the F16, is light compared to the F15 and FA18. Depending on the carrier (deck length), the power of the cat, and the wind conditions, it is entirely possible to lift off the deck before it ends. In these cases, you won't get the "drop" that is so evident on the larger aircraft. You can sim this by having the jet start to lift at about 1.2-1.5 secs into the launch as the lift of the wings starts to support the weight. Raise the attitude of the jet on the gear to fully extended at 1.2 and start lifting the front tire at 1.5. Keep in mind that the cat shuttle and bridle will act as a weight holding the nose level instead of allowing it to cock up. At about 1.8 seconds (200m or so) the lighter craft will start lifting the fuselage. At this point it is possible for the bridle to release and allow the jet to climb, but not many pilots have the reflexes to start the climb this early as the Gx is still excessive. On an 80m deck the jet will be airborne right at 2s as the deck will have ended; on a 95m deck it may take around 2.1s for a lighter craft to lift. The heavier craft will not lift until around 2.4-2.45s when the deck will have ended.
For your animation, (assuming motion of launch along +X) the critical part is that the jet will go from stop to dX=30m in 1second. After that you're probably going to be seeing the jet from an angle where it is easier to hide "inaccuracies." Since the "Top Gun" era, folks are used to seeing the initial impulse from the cat. With so much reference, anything "slower" will look "wrong".
Kendall
I got a bugger on my finger!! And i cant get it off!
I got a bugger on my finger!! And i cant get it off!
???
Kendall
Just being an ARSE! I been up sicne 4 am!
If you still want the dip... keep in mind the velocity when the plane leaves the deck. If it covered 80m in 2 seconds, how far did it travel from the end of the deck before it was able to get back to dY=0? another 80m? more? If you don't put the relative distances into perspective then it's going to look terrible. You also need to determine just how far the jet will fall while dY is negative. Too much and your audience will think the plane has crashed, not far enough and you'd be better lifting from the deck.
You're covering ~200m in a 3.5-4s launch timespan. What are your distances in your timeline and motion paths?
Kendall
I read recently that the steam powered catapult is due to be replaced by a magnetically powered one, like what is used in some high speed trains and rail guns. I wonder if the electrical systems on the ships have to be upgraded to handle that.
http://www.airspacemag.com/military-aviation/electromagnetic-catapults.html
Kendall
Wonderful modelling and animation!
okay I forgive you for posting 5oo threads an hour... nice work, you should be proud of yourself, now go and have a rest,
bad luck about the bugger on your finger
only c and c is the shoulder is a little stiff on the pilot and the guy we see from the back isn't wearing undies....
well, if he is there isn't much room cause his pants are pretty tight :)
Well kendel I knew I should of saved the rough cuts of the failed dip. but didnt! I put up a new animation WELL the same one with another 3 seconds added and it the F4 goes off the end of the deck! at....
http://www.youtube.com/watch?v=_6vm1NE6n4k
ALSO heres a vid of a real F4 on cat trials now keep in mind these f4s are slick so have no real LOAD on em and if you look they still sort of DIP down a little after they launch! BUT a could did go straight pretty much sort of looks like mine clip
http://www.youtube.com/watch?v=_P6ItbKjPZM
Matter of fact I may need top slow it down!
Want to add some steam but waiting till I get PI
OK. I see your problem. The F4s in the vid *don't* drop, they actually lift from the deck. What your seeing is what I described before about the shuttle and bridle. In the older days the shuttle connected to a woven steel cable (bridle). The pilots would pull back on the stick from time 0 all the way through the launch. Meaning that without the bridle, the plane would have tried to flip. So, as the shuttle reaches the end on the flight deck it releases the bridle cable and the nose of the plane cocks up immediately and dramatically -- as it's been trying to do the whole time. This causes a pivot in the planes attitude that causes the tail to describe a small semi-circle that looks like a dip, but isn't.
I've drawn a crude graph of the positions of the nose, body (at the rear wheels), and tail. As you can see from the graph the plane's body doesn't dip, but the pivot causes the tail to circumscribe an arc that slightly dips below the body's path. The longer the fuselage is from center-of-gravity to tail, the more pronounced the arc. You can see this effect using a pencil on your desk. Set a point to be the nose, a point 2/3 of the way back for the COG . Pivot the pencil from the COG point as you move it across your desk in a rising arc.
Kendall
I got to say RC that your work in hex and carrara are stupifying.
Excellent modeling and great animation, btw how'd you get the jet exhaust
to look so realistic?
Im thinking particle emitters but which ones?