SLOPING OFF...
...Christchurch and District Model Flying Club’s Magazine for August 2023
TRACTOR CRUSH! AND THE BLACK HOLE OF KNOWLE HILL, CHURCH KNOWLE
by David Bicker
When you stand at our “usual slope flying (SE) site at East Creech, if you look eastwards towards Corfe Castle you can see that there is a flyable hill ridge where you can fly either N or S direction winds. This is on the ridge above Church Knowle in the valley below.
This was my first time flying the North slope at Knowle hill. It was a dry but windy day, 25 gusting 30mph. For the first condition testing flight, I had a good 20 minute flight with the Zagi and landed it about 1m from my feet - probably the best landing I've managed!
Next up was the Top Model CZ 1.8m Sweet glider. This has a fibreglass fuselage and a built-up 3-piece balsa 1.8m wing with a slim 12mm cross section, so quite a slippery profile. Reviews of it class it as a “warm-liner”. It shows lift well but in standard build doesn’t come with flaps to aid in landings. I rectified that and added flaps so that it now has Crow brakes which makes a big difference. It has been an enjoyable model to fly and I have flown it at East Creech, Win Green and the SW bowl at Whitesheet near Mere many times, usually with easy landings whatever the wind speed. I have flown it un-ballasted in 30mph blows several times without any issues.
I flew it over a wide ranging area for about 20 mins and brought it in to land to my left, slightly behind where I was flying from, nearer to the brow of the hill in open grassland. I had flown it down to land on full Crow, which worked well until just above ground level where a strong gust of wind picked it up and pushed it backwards. In retrospect I probably could have flown it forward if I had thought to close the Crow brakes to pick up a bit more forward speed against the blow - but I didn't, so it settled to ground level - and then sank out of sight as I'd lost depth perception by that point and hadn't realised that it was actually behind the brow of the hill.
I ran over to where I had lost sight of the model and - there it was - GONE!! I thought that, like other models that had "got away from me" in the past, that it would be a dart, nose-first in the ground, a pile of impacted balsa good for a carrier bag, or sticking tail-first out of the top of the gorse bushes lower down the slope. No - it had vanished! I then spent 2 hours of that hot sunny afternoon in the hot still air on the leeward side of the hill, clambering up and down the almost sheer, thorn-covered slope searching for it to no avail.
On the 2nd search day Brian Brockway volunteered his mountain Goat-like abilities to help in the search. We spent 2 hours scouring the slope, both of us with binoculars. I started at the top and then worked through the scrub down to the middle and eventually the lower path while Brian ranged through the fields below, looking back up at the slope. A lot of the Gorse has been managed and cut back, but we were surprised by how many areas had sheer slopes with pockets of tall saplings and 1-2m high Gorse.
Unfortunately the only outcome of that search was Brian losing one of his beating sticks.
I then bought a cheap drone - which was faulty and went straight back to the seller. Then I bought another slightly better drone at twice the price and practiced in my back garden. It had One Touch launch and landing, Collision Avoidance etc and flew well. So the next day I took it to the site and it flew OK for its first flight. On second flight (wind was NW at the time, so I was on the calm leeward side of hill) - a big gust came from nowhere, blowing westwards along the south-side of the slope and blew the drone westwards and upwards. Apparently lacking the ability of its tiny props to counter it, so it just kept climbing. Then it dropped out of sky, landing in tall grass in the field next to me. After 1hr search in waist-high crop grass I declared it lost / m.i.a. It was impossible to find a little thing like that in waist high grass even although I'd stuck bright yellow markings on the drone's blue body. The body was only about 5" long, so if it had fallen edge-on into the long grass, it would become undetectable. The Return to Base function hadn’t worked.
Frustrated, hot & tired, I packed up and headed back to my car which of course was at the top of the hill, so another hot sheer climb. Just as I was about to leave, I heard a big drone nearby, so headed back to the road by the gates and found a Pro drone operator there. He landed his big 1m span £6k drone on a landing pad with a big H on it and then launched a DJI Mavic 2 and sent it up the hill to video the slope. After a few minutes it lost signal and disappeared! (He said he'd never had it happen before). He thinks it might have been caused by the nearby military sending a burst transmission that broke the connection.
Anyway, we walked back up hill to hear the drone still flying. It reconnected and he flew it to about 1m from his head and then reached over and plucked it out of the air. He said that it is programmed to hold station if it loses signal and to return to base when the battery gets low. It had a flight duration of about 25mins, so he wasn’t in a hurry to find it when he lost signal. Anyway he offered to email me the footage taken of the slope and we parted company. (He never did as he said that he didn’t see any evidence of the plane on the footage).
I returned next day and searched for 3hrs more and gave up. So I pinned some laminated lost model notices on the byway styles around the area that I had prepared prior to the trip. Bear in mind that, from where I live in Sixpenny Handley to these slopes is a 64 miles round trip, I had to stop commuting there for the searches at some point!
What I haven’t mentioned so far is the destruction done to my car by the cattle in the field! They crowded around the car whenever I left it unattended and I came back to find that they had licked slobber on all of the glass, the mirrors and the screen wash nozzles and the hood. The mirrors had been licked up into their folded positions. A cow had completely removed the left wiper blade off the arm and chewed the plastic end of it. Another cow had somehow managed to lick above the driver’s window, pulling out several threads in the edge of the soft top hood above the glass. These were hanging down the window glass for about 8” by the time that I shoo’d them away!We had spent a total of 11hrs over 3 days searching for the lost model.
Dave Bicker at the local car wash - Ed
So a lost plane, a lost drone, a pro drone lost for a while, Brian’s beating stick going missing, cattle vandalising my car at what I now term as the Church Knowle Black Hole!
On the upside of the experience, I found a days-old Deer fawn when searching in the long grass.
Later that same evening, after I had driven 32 miles back to home, I had a call from a resident of Church Knowle village saying he'd found the plane! So I drove back again and collected it (and walked around removing the lost model notices). I gave the guy the promised reward for finding it. It was (technically) still all in 1 piece but very battered as driven over by a large tractor tyre as the farmer had cut the hay around the perimeter of the field the very evening after I had abandoned my search. It turned out that it had flown on a glide path for about 1/4 mile southwards, away from the slope across 2 large fields to the south of the hill, by the road and almost into the gardens at Church Knowle!
One club member suggested that the high wind may have created a rotor effect on the leeward side of the hill and that instead of settling / diving in, the model had been picked up, gained lift and turned to a glide path southwards and away from the hill.
At least I'd got all my metal gear servos and RX kit back. At the time, as it has a balsa built wing I thought that I might try repairing it sometime….
It has crush damage that matched the width of the tractor tyre’s tracks. The driver must have stopped just before it went through the mowing attachment behind the tractor. He was kind enough to prop the model up at the side of the field in the hedge.
The fuselage tail boom sheared cleanly and has a small crush mark at one point, but the tail assembly is perfect. The central wing section is battered but the dihedral was still there and the mainspar appeared undamaged, so worth looking at repairing it.
Some weeks later I decided to repair it. The fuselage was re-joined to the tail boom. The control cables had been the only thing holding the broken bits together. It went together with no cable adjustments to the rudder and elevator needed. The fuselage had compression marks on both sides but was repaired internally and then re-sprayed.
As the model came with the wing sections pre-built and covered I didn’t have any plans to work from. So I removed sections and replaced them, straightening it out as I went. I replaced the leading edges, replaced ribs and re-sheeted the front sections, repairing the servo trays too.
The ailerons straightened out after storage in mild compression (as did the leading edges before I replaced them) to keep the shape of the wing whilst working on other areas.
New decals were cut on my plotter-cutter and the surfaces were covered. Due to the repairs it has weighed in about 50g heavier than the plan specified maximum, but I’ll just think of that as ballast!
David Bicker