Monday, January 30, 2006

Volkrust 28 / 29 Jan 2006 -- Warren Butler

After a very pleasant drive up to Volksies, the group decided that the severely waterlogged field as well as the pretty strong wind would have to be given up in favour of some casual slope flying.

Driving up to the slope (these okes are severely spoilt with such a magnificent site in all aspects!) saw a few chaps carving it up already. Russ, you would have had an absolute ball with a heavy Toko! I only had my Zagi (from Ev a few years ago) to play with and a few seconds into the blustery first fling, revealed that it's gonna need more than just a sliver of lead to get it going. The second fling, revealed that it's gonna need even more! Having upturned my flight box in the hunt for more lead had the Zagi at more than double it's original weight (450g + 500g lead!!) I heaved it into the wind and up it went. I must have got the ballast position smack on since I didn't need even one click of trim, it was getting on-step with no effort at all. Loops were using the whole sky! Not normal for a Zagi. Now for a few speed runs........the first one came whistling past and quite surprised me and the pull-up was the best I've seen in a Zagi. Deciding to gain a bit more height for the next one saw it coming in from the left and as I levelled out, a strance buzzing sort of noise was coming from the elevons! This is exciting! Correx must have some sort of 'sweet spot resonance' at a particular speed. Let's see if it will do that again.......! Climbing a bit higher this time and also coming in from the left saw distinct signs of elevon flutter, this time quite a bit louder and as I levelled off, BANG!!, the whole thing exploded! The wing split in 2 and flipped up at 90 deg. to the airflow, battery pack still going straight!! Confetti and bits raining down. What a sight! At least the R700 Rx was still dangling by one servo lead!! The battery pack was from my Cobra (4 cell NiCd) and needed replacing anyway. Never found it. This was the same Zagi (sans lead) that had the 'most amazing last flight' at Rosendal last year, using the valley release till it was dark. I have another set of this space!

There were a few Nelspruit chaps there with a funny looking thing (name escapes me) made from EPP. Sort of curved leading edge delta, central fin with huge elevon surfaces. There were about 4 of them in the air, and all of them had one wing's underside panel painted with a big red "X" and later I was to find out why(!!) I was offered a stir on the sticks since the one I saw flying seemed pretty nimble. You know how it's done. You sneak up next to the guy and tell him how nice his aerie looks then after 30 seconds mention casually that you also fly the same mode. If he then doesn't shove the Tx in your hands, he is either deaf or is silently saying 'bugger off!' I got the tranny! I tried a gentle roll and all I can say is "What the #$%&* was that?!" This thing redefines the term "twinkle rolls!" Now I know why you need to clearly mark one wing panel's underside!! The roll rate must have been about 5 rolls per second, I kid you not! They bounce quite well too since the one I saw plonked it squarely onto a rock more than once with no apparent damage. Further questions revealed that, in my opinion, R650 would be better spent on a new JR R-700 Rx and a micro servo!

The chaps had boerie rolls and refreshments laid on as well. A very friendly bunch.

Just checking to see if anyone is keen on Volksies for the Black Eagle Slope weekend on 11th and 12th March. Dave said that it clashed with something else he has planned but I'm keen to go. Anyone else? This weekend was my first taste of Volksies and certainly not my last. Come on chaps, let's get planning.

Warren Butler

Friday, January 20, 2006

The South African F3J team BLOG

Have a look at the SA F3J team BLOG -- inspiring.

Almost a quiet day at JOMAC

On Thursday I had arranged to meet Kelvin Reynolds at JOMAC for some relaxed flying.

I drove out along William Nicol, not much traffic, slightly overcast with a gentle breeze, perfect.

This desirable state of affairs lasted until the Dainfern turn-off. There, Metro Police were blocking all traffic along the R511 in the direction of the field. I turned around and came home.

The seven o'clock E News told the rest of the tale.

In Diepsloot members of two Taxi Associations had exchanged fire. In the melee shots struck passing motorists. A lorry hit a Metro Police office killing him. Metro Police arrested several men after a skirmish on the veld.

From some points of view we do live in desperate times.

John Godwin

Wednesday, January 11, 2006

Tuesday, January 10, 2006

LiPo balancing -- Andre Kilian

You have probably not picked up much on the subject on the internet, as it has not been much of an issue at the charge/discharge rates used. One of the reasons for the limitation on the charge rate of 1C on lipos was to ensure that they stay balanced - you will note that some of the manufacturers are using higher charge rates possible with lipo balancers as a "selling point" - I have seen charging times advertised as 20 mins! I have personally checked the voltage on idividual cells on an old Kokam 1500 3S pack that has more than 100 charge/discharge cycles, and cells were within a few milli volts of each other.

The problem comes in with the new 20C packs (20C continous rating - 30C peak), as at these high discharge rates the cells tend to become unbalanced. I have noted that the problem also arises when running a number of cells next to each other, e.g. 5S packs. I suspect that the imbalance arises from the different internal resistance of the inner cells that are running at higher temperatures.

You also need a seperate lipo balancer that normally works with any lipo charger. These monitor the voltages on each individual cell - that is why the tags are used. An added advantage is the safety feature - the better ones cut off before overcharging the batteries if you have chosen the incorrect settings!

My advice is not to worry about lipo balancing unless you are using the 15 - 20C rated cells and are pushing them to their limits! As a precautionary measure I have soldered tags on all my batteries and only charge through the tags - accidents are bound to happen, as I am charging 2S, 3S, 4S and 5S packs! At about R10 a tag I view it as a worthwhile investment, as i have enough "fat packs"!



Tuesday, January 03, 2006

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