Water explanation, please.....

Discussion related to the Condor...

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Postby TimKuijpers » Thu Nov 13, 2008 2:56 pm

Thats like selling a sportscar with a good looking spoiler and saying:
It looks really nice, but it won't have any effect on the performance.
You'd just say, it's a really nice spoiler. Won't have to lie, and better salesment.
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Postby Jarmo K » Fri Nov 14, 2008 2:08 pm

Alpha Whisky wrote:That's odd, because the Condor manual says

C/G bias: Here you specify the relative position of your plane's center of gravity (C of G). The influence of this setting on performance is very small. The more important effect is glider handling.

You would think if it wasn't modelled at all, the manual would say "This setting has no influence on performance".

+1 to this, as my experience is below:

One SBC task in Slovenia when start was late... I was one of last (&few) task finishers and almost was not included in those. I had set C/G quite backwards for easier handling in thermals, based on ASW27 handling experience in some previous race...
Sunset was getting closer and only very weak lifts were left, and I had dumped my water earlier, so heading home long glide with very low margin. We flew side by side with SVR both with LS8 and we both had MC0

I had some +5-10m when started FG and SVR had slightly less and flying lower. I complained him in TS that even flying with correct MC0 speed, my DDH was getting less and less and he didn't have the same phenomenom. And actually he's MC0 speed was more than mine.

So after that experience I haven't touched C/G setting at all.
It can be that with higher speeds the difference is minimal, but without water and MC0 I see there's is difference.

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Postby TimKuijpers » Fri Nov 14, 2008 2:37 pm

Of course nobody did a test flight on this subject, did they? :roll:
It's soo easy to find out...
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Postby Alpha Whisky » Fri Nov 14, 2008 3:52 pm

TimKuijpers wrote:Of course nobody did a test flight on this subject, did they? :roll:
It's soo easy to find out...

Strange you should say that. I did a test flight on this last night. Three flights in the ASW28 at neutral, full forward and full rearward C of G. Zero difference in sink rate at 70kts or at 100kts (using the autopilot) so it appears it isn't modelled by Condor.
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Postby mumbles » Fri Nov 14, 2008 3:59 pm

I just did a quick test as well with the ASW 28, 100 km/h at the three cg ranges and looked at distance traveled, starting form 200 m. Full aft produced 9.11km, neutral 9.03km, full forward 9.02. If I get some free time I may try to do multiple attempts from a higher altitude.
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Postby TimKuijpers » Fri Nov 14, 2008 4:10 pm

Well, the PDA says the same for C/G forward and negative.
Plus I did a straight flight, saved the ftr, and flew behind it with a different configuration.
And as I told, the developers told me that it had no effect on the performance.
I'm convinced :)
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Re: Water explanation, please.....

Postby Andrzej Czop » Thu Mar 11, 2010 5:13 pm

Yes, it is true, but one text from manual:

"C/G bias: Here you specify the relative position of your plane’s center of gravity (C of G). The influence of this setting on performance is very small. The more important effect is glider handling"

I made somme tests with PW5 with different setings trimmer ans C/G and it is very important to quality of steering quality and the fluency of flight, finnaly on mGN and mCR


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Postby j.theswede » Tue Mar 16, 2010 7:13 pm

Fiddeflygare wrote:Regarding Water ballast dumping during real cross country soaring it normally depends on how you will land when you should dump the ballast. I have been tougt to start dumping between 4-5km:s out from the finish line if its over an airfield. if you have lots of altitude when crossing finish line you don´t have to dump before. If you are gonna land straight in (passing finish line rolling on the ground) you can dump the ballast a little earlier. The general idea is that you should not have any ballast left when touching down on the field even though most gliders is landable with ballast left. The problem is that the wing tanks might empty themselves unevenly. This makes it more possible that you will have a ground loop when landing with risks of damaging the glider. This easily occurs if you are turning in one direction for a longer period of time during the dump.

If one wing drains quicker while turning you must be flying really badly. you can drain your tanks in a themal without problems as long as you keep the ball in the middle. Also I never drain tanks before finishline. I have landed several times full of water and this is no problem unless you land really poorly... I have also witnessed landing with one side full. This didnt affect airplane until last 10kmh. just my 5 cents... :D
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Re: Water explanation, please.....

Postby MrTumnus » Mon Oct 11, 2010 11:59 pm

Bassically, using water you can change at what speed your best glide is. For example with water in a Nimbus your best glide is at 59kts?? with full water and about 50 without. This means you can fly faster without losing as much height. Disadvantages:- Worsens handling, if you stop to thermal you need to be quite fast e.g. 60kts with full water as your stall speed is increased, in bad conditions your better off getting rid of water as you'll find it easier to thermal effectively. In Good conditions use water, in bad conditions don't.

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Re: Water explanation, please.....

Postby BA » Tue Oct 12, 2010 3:25 pm

Maybe a little addition to that question...


watch the second video "CG and Water"

Cheers :)

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Re: Water explanation, please.....

Postby k6pete » Fri Dec 13, 2013 11:30 pm

mojo wrote:Hi all

I think I've finally got to grip with most of the concepts on offer in Condor, but would appreciate a bit of advice on the pros and cons of taking on water (ballast). I appreciate that increased speeds would be a factor, as would increased sink-rates, but I could do with some info on the effects of water placement. Why tail-heavy, or nose-heavy etc.

Also, what conditions would prompt you to consider ballast.

In anticipation, thanks!!!

Mojo :?:

With no balast you would be hard pressed in strong winds with stick forward to go ahead and sink lots, with the wieght of water you would not have to push on the stick so much and as you glide angle stay the same with weight, this is magic stuff... and you can dump it at any time Cheers k6pete

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Re: Water explanation, please.....

Postby Sticky Digit » Tue Mar 15, 2016 11:40 pm

Hi all . RE:- Waterrrrrrr,
Up to this point explanations of the amount of water to carry is pretty accurate as far as it goes. BUT.... Most thermals get wider and stronger the higher you are flying in them (in general) Wave is more predictable and easier to plot the higher you are, (in general) and Ridges are stronger and more consistant near the top ( in general) . So do keep your water for as long as you can but remember that the strength of and the predictability of the lift gives you the height which you convert to speed to win the race. Therefore it is perhaps the hardest decision in speed flying to know when to dump water and how much.
The curse of not winning is often being able to watch the glider who is going to win when it arrives higher, in the same thermal then climbs quicker and leaves all in his dust. Sometimes it is because he is a better pilot but most times it is because he chose to stay in a higher altitude to take advantage of better region of lift. MORAL:- Flying your glider fast between the lift sources is no compensation for winning. Sometimes carrying water but not going too fast keeps you above the weeds and in the better lift.
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