Author Topic: P17 Manoeuvre Geometries  (Read 5701 times)

Offline Yoda

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Re: P17 Manoeuvre Geometries
« Reply #15 on: 01, October 2015, 12:54:30 PM »
Hi Stuart,

The direction the arrow points in aresti is purely to tell the pilot which direction to rotate. The aresti in P17 clearly shows the arrow pointing in the same direction as the rolls, therefore the pilot must rotate in the same direction in which they roll. A positive or negative snap may be performed. A snap roll performed from inverted does not need to have an inverted triangle.

On another point, the aresti clearly shows that there are two different looping radii in the knife edge humpty. The two on the bottom are equal but the knife edge on top is larger. Does the F3A judging guide reflect the aresti? If they are looking for all the radii to be the same then they have drawn the aresti diagram incorrectly. The same goes for the goldfish after the KE humpty, tight radii in and out. Again, if the judging guide is asking for equal radii throughout the manoeuvre then the aresti has been drawn incorrectly. Remember, if in doubt it is always the aresti diagram that is referred to to clarify these things, but F3A sometimes make up their own rules.

I flew this on Saturday with my 260, bloody good. Best P for a long time. The F is also good but my own personal view is that they need to ditch some of the sharp knife edge moves and replace them with integrated rolling moves. 

Offline Stuart Mellor

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Re: P17 Manoeuvre Geometries
« Reply #16 on: 01, October 2015, 04:36:22 PM »
Hi Peter,
No Peter - the direction of snap is independent of whether the aircraft is upright or inverted. Direction of rotation may be linked to a previous or following manoevre, in which case the Aresti diagram, or text description will clarify. If its not opposite - the triangle will be above the line point up. If opposite, point down & below the line.

Hi Angus - Looking still further into the black hole.....ref  'Aresti made Simple by Barry Wegman' & the British Aerobatic Association's (full size) website......

A 'normal' snap , whether from upright or inverted is always shown as an 'upright' triangle. A negative snap is filled in (usually red though).
Also - if the snap is intended to be opposite to , say, a following or preceding roll element, the triangle is inverted , with point down. In 'our' case P-17 snap - the triangle point is above the line, therefore the rolls & snap are in the same direction.
ps -the tick on the top of the triangle just indicates the direction of flight, I believe - not direction of rotation. That is defined as above.
 
re - the Humpty - BAA state the the radius at the top (or bottom) of a humpty does not have to be the same as the other radii.
re - the SC Aresti diagram - don't get me started. The P-15 Aresti showed the Top hat as 'square'  - whereas we all know now - that was not what was intended!
 
Look at P. 29 of the SC  - Aresti symbols - left hand column near the bottom -snap rolls. There's a clear mistake - the 'negative G snap roll from inverted flight' shows the triangle inverted. Incorrect -it should be upright. Its only shown inverted when the snap is opposite to another roll.
 
Next symbol down is correct - 'Two positive snap rolls in opposite directions' i.e. 1 triangle point up, 1 point down. Both not filled in & therefore positive.
Note also - the 'ticks' at the apex of the triangles both point forward.i.e. the ticks are not a reference to direction of rotation, just direction of flight.

Jo - where's those 2 paracetemol I asked for?
 
« Last Edit: 01, October 2015, 05:00:10 PM by Stuart Mellor »

Offline peter brett

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Re: P17 Manoeuvre Geometries
« Reply #17 on: 04, October 2015, 10:03:30 AM »
Thanks to all for contributing to this, it's really useful especially if one can't get to Adrian's Hurley comp this weekend.
Slightly off topic but.......
Adrian M what CAD programme were you using for this - and would you recommend it for other things as well?


Peter

Offline Adrian Mansell

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Re: P17 Manoeuvre Geometries
« Reply #18 on: 11, October 2015, 08:56:17 AM »
Hi Peter,


Sorry for the slow response.  The diagrams were drawn on Techsoft 2D design.  It is a good CAD package in that it is designed for teaching CAD, so has everything I need for 2D drawing without all the whistles and bells to confuse things.  On the flip side, it's not cheap (£200+) - I have a very old license that I keep flogging away on.  I use it for all my 2D model CAD drawings.


I don't know enough about what is out there these days to recommend it or not.  It would certainly be worth trawling the forums for info, there are a number of open source (=free) CAD packages around these days.


A

Offline Alan Simmonds

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Re: P17 Manoeuvre Geometries
« Reply #19 on: 11, October 2015, 10:32:25 AM »
Peter

For 2D CAD, I use Draftsight from Dassault Systemes (the makers of Solidworks and Catia): https://www.3ds.com/products-services/draftsight-cad-software/free-download/

This entirely free software is very similar to AutoCad and uses many of the same keyboard shortcuts. There is a PRO version with more features which they will try to flog you, but the free software is more than adequate for general purposes.

Give it a try.
Alan

Offline peter brett

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Re: P17 Manoeuvre Geometries
« Reply #20 on: 11, October 2015, 06:24:51 PM »
Thank you Adrian and Alan I'll give the free Draftsight a go as I have done a bit with Autocad in the past.
I like the idea of drawing out the manoeuvres to get the shapes in your head, for flying and judging.


Peter

Offline Serious Power

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Re: P17 Manoeuvre Geometries
« Reply #21 on: 05, September 2017, 01:16:06 PM »
Hi,
Anyone know if/where the Geometries for P19 are available  ??


Brian

Offline Alan Wild

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Offline Alan Wild

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Offline Mike Wood

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Re: P17 Manoeuvre Geometries
« Reply #24 on: 08, September 2017, 07:46:21 AM »
Thanks Alan and Peter Uhlig.

Mike

Offline dan workman

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Re: P17 Manoeuvre Geometries
« Reply #25 on: 08, September 2017, 08:45:20 AM »
Is there one of these for f19?

Offline Alan Wild

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Re: P17 Manoeuvre Geometries
« Reply #26 on: 08, September 2017, 10:10:42 AM »
Yes,Dan.
See post #22,which I put in ,in error for P19.

Offline Serious Power

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Re: P17 Manoeuvre Geometries
« Reply #27 on: 08, September 2017, 12:40:49 PM »
Hi Alan,
Thanks, but not what I'm looking for.
ie; The drawings in post #1 that Adrian produced, but for P19.
A Japanese guy also used to do them for the various schedules !!?


Peter's judging guide PP presentations are great at what they are for, also.


Brian