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Old Feb 26, 2014, 05:57 AM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
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Alex's DS theories

They may be total BS but is what I have found over the years. Hopefully they can be of help to others out there.

Late at night, tired with not much to do, bad conditions for mindless ranting...

To fly the fastest on a given day totally depends on the weight your model is flying at. Also depends on the power in the conditions, that being, is it consistent, or does the power come and go. The conditions and how you fly to them is a huge part of it I have found. Tekapo has been the biggest eye opener and teaching point for me.

When the power comes and goes and is short in time when it is there, a lighter than normal model I have found better due to it being able to accelerate easier. Example was my 1.6kg Burner at Tekapo during the DS fest getting to 285 to equal the record at the time. Asto flew his much heavier burner later on burning some perfect big laps, but couldn't get over 241. I was pulling much tighter laps and was sitting in the 220s-230s, then as a gust came, it accellerated to 270 in a lap or two. A lighter model needs tighter laps than a heavier one due to not having the inertia to counteract the drag/turbulence. You need to use the DS kick more often in a given time to maintain/gain speed. A heavier model can maintain speed from a previous boost from a power period, even if the current air would not accelerate it to that speed, but it may take twice as many laps to pick up to the same speed as the lighter model. In short, heavy means you can nail the laps easier as you can fly a bigger and longer lap, but may not make the most of the power avaiable. Lighter is harder to fly faster as you need smaller laps but will make use of accelleration from the power when doing so.

When I first flew my D60 at Wainui, the day I went 318, I flew it twice. Both flights I flew the same medium-large laps. Once ballasted it jumped up about 10-15mph in average speed. If I had tightened it up when light, I feel I could have got 300+. Basically what I am saying, it depends on pilot ability too, as the tighter laps are much harder to fly consistently.

Which brings me onto the next point. Laps, the power line WIILL change depending on the gusting of the wind. The boundary layer is always moving and so is the air on the back. I have watched some very erratic laps yeild the same speeds as someone who is pulling in the most perfect and consistent laps. My theory is that they are making use of power that isn't on a good radar line, then pulling a perfect radar line straight after. An example is my 214 run at sugarloaf with my old Destiny. No reads near 200, a few laps up high gaining speed that I couldn't gain down low on a radar line, pulled one down low right in front of the radar gun and, boom, 214 from seemingly nowhere. Sugarloaf is a site that works best doing that. Even tekapo is like that in bigger air. In lighter air it doesn't seem to matter.

In Bigger air it gets rougher. More wind means brings more air movement and means your model is flying through ever changing wind vectors. I feel the higher laps to gain speed then pulling a lower radar gun line lap can yeild some of the best numbers. In medium air trying to nail the consistent lap is the key.

There is much more that my tired brain is missing.

Please feel free to BS me and pull it all apart

My theory is DS is like thermal flying. It is about reading the air and feeling it out with the model, reading the changes and trying to make the most out of what the air is giving you.
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Last edited by ALEX HEWSON; Feb 26, 2014 at 06:08 AM.
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Old Feb 26, 2014, 06:17 AM
Just Stab It In
Bangalow,Australia
Joined Aug 2008
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Totally agree with you Alex. I enjoy flying lighter models now doing tighter laps. The fun factor is much much more flying lighter models than heavier.
I learnt a lot that big day at Tekapo.

Wind direction is a major factor as well.
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Old Feb 26, 2014, 09:12 AM
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Pacific Palisades, CA
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Good stuff Alex. Thanks for sharing. For guys like me who don't fly as often, just watching someone fast and trying to decipher what they're doing can be very enlightening.
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Old Feb 26, 2014, 08:47 PM
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Curitiba - Brazil
Joined Oct 2007
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Keep sharing your ideas, it will help getting shortcut to fly it efficient and faaaassstt
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Old Feb 26, 2014, 10:12 PM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
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Damn saw this thread and forgot I even wrote it! I am suprised it even makes sense. Was written near midnight after working for 14 hours lol!

Thanks for your comments.

Yes you are very right, Asto. Wind direction plays a major part. The air tends to spill over when it isn't square on. When you look at the cross section of the hill along the wind vector, it flattens the hill out, meaning if wind is off angel, your ridge isn't as steep or sharp at the top. This makes the air attach to the contour easier and not seperate at the lip cleanly.

This, I feel, is why Weldon and Bird Springs work so well. The valleys straighten the wind perfectly square to the hill. The valley leading up to Weldon isnt as narrow so vector tends to change a little, but still within the workable realms.

This is why tekapo is very temperamental. Is has nothing to straighten the airflow leading up to it. Is has no hills in front of it so wind is smooth and it accelerates leading up to the hill, just vector changes a bit with nothing to keep it in line
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Old Feb 27, 2014, 12:06 AM
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Thanks Alex, that all makes a lot of sense.
Cheers
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Old Feb 27, 2014, 03:46 AM
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Wellington, New Zealand
Joined Sep 2009
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I've noticed that what's up-stream of the hill has as a big effect on how good DSing will be on it. With our two main sites: Long Gully & Ngiao, Long Gully has the more classic straight knife-edge ridge (its far from perfect); while Ngaio from first look wouldn't look like the sort of hill that would be much good. They both have very big back-sides. However Long Gully has a same-height ridge 800 meters upwind of it, where Ngiao does not. Ngaio tends to be noticeably much smoother than Long Gully in big winds (gale force and above).

So in our case the better shaped ridge is out-performed by the less classical shaped ridge with cleaner airflow over it.
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Old Feb 27, 2014, 05:02 AM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
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Totally. We have a great ridge (probably Christchurch's best shaped ridge) funnily enough, called Mt Parker. But it has a hill about 600m in front of it. A little lower, but enough to kill the air. Works in a NW wind. Fastest we have gone there is about 130 maybe 140 something with foam. You need a lightish plane as lift can drop to nothing. Haven't flown it for over 7 years!
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Old Feb 28, 2014, 07:19 PM
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timbuck's Avatar
gold coast australia
Joined Aug 2008
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Sound good Alex nothing to pull apart here

Only thing I'll add is , also depends what CL range a particular airfoil / plane is best flying at. We have seen on an unballasted D80 tight laps slow is down about 20 or 30mph and medium CL type laps it eats it up. Compared to a K2M do big open low CL laps and it will cruise around @ 200 and start to bang it hard and it will go to 250.. It's definaly the best example.
Ezza and Asto flying light K2m's on an average 20knt day can hands off ds and cruise around or fly it crazy tight and the speed comes.
I agree flying heavier allows you to fly faster easier ( for the average guy) but as you get better and better a lighter ( but not to light) plane will be more fun and you can get similar speeds.
It all comes down to so many variables.... Conditions , hill shape , turbulence , gust length.

LIGHTER
Finds power easier , more fun to fly , lands much easier , easier to find a day to DS

HEAVIER
Take longer to gain speed from power , easier to fly , lands very hard , Much better in rough air.

I guess why we all need a plane for each condition
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Old Feb 28, 2014, 07:43 PM
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Thank for your comments Alex and explains a bit of why I find DS more difficult in Aus.

On my first DS attempt I achieved 78mph on Tekapo with big laps, since being home our sites are much smaller and I have found simply string 2 laps together difficult. Never really thought about it but the tighter Laps do happen faster and explain some of the issue I have had.
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Old Mar 02, 2014, 01:52 PM
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ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
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Totally agree, Tim. SO many variables.
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