This is a report on our recent flight
to Cornwall. The flight currently holds the BGA Seager Trophy for the longest
out and return flight this season and has generated a lot of interest with nearly
600 glider pilot viewing the trace on the BGA ladder. I hope the report
encourages you all to plan and fly your 'epic' flights from Shenington this
season!
Al Cook.
The weather forecast for Saturday April 23rd indicated northerly polar air
mass with the same temp/due
point characteristics as the previous Sunday 17th April. Those of you
flying on that Sunday would have experienced some fantastic conditions and the
best looking sky seen at EDG for many many months. I know because I spent the
day sat in my garden looking at
this magnificent sky whilst my (new) syndicate partner was having a nice pub lunch unable to fly that
day! Saturday the 23rd was therefore a day defiantly not to be missed. Mid week planning favored a big out and return flight. The forecast northerly wind ruled out a flight to Scotland
and favoured a downwind first leg into 'the peninsular' that we hoped would set up a strong convergence aiding the run to the only turn point. Making sure GP had some lunch (!) sorted a task was set for Truro out and return 648km. Completely bonkers?
Absolutely not! And here's why - Firstly the
met forecast was spot on, Cu started popping by 09:30L. We
launched, at 10:37L (09:37 UTC - Earth time) into a sky full of small Cu with low bases. Early morning there
tends to be lots of small thermals closely spaced so a good technique in these
conditions is to 'bounce' the thermals, pulling up
in the lift, turning only when the thermals get a little stronger and further spaced. Using
this technique we didn't do much circling until passing the city of Bath. Early
speeds were good, pushing
110kph. Outbound leg was showing a wind of 010/15 kts and the cloud shadows indicated good signs of streeting. We tracking south of the Somerset Levels, to remain
clear of the wet and soggy area that
can reduce thermal strength, picking up
nice climbs under the cloud streets. Speed remaining at 100kph plus and helped by the wind we quickly passed Exeter
heading on towards Dartmoor.
The mouth of the River Exe heading South
 |
| The mouth of the River Exe heading South |
Conditions were now changing, the cloud streets were not
on track, the clouds lacked a little definition and to the north
appeared small and 'ripped up' indicating the first signs of
'sea air'. The cloud shadow spacing also showed it was time to slow up and
consider our options.
After
Exeter we picked up a scrappy 3 kt
climb to 4200' amsl. This left
us with our first tactical decision
to make! Cross the moor low level or divert north away from the high ground towards the
'sea air'. Dartmoor rises to 1700' amsl and we
considered that if it was not working there was a distinct possibility that we
could get low with very few land out options available. Of course the Nimbus
has the benefit of an engine but in order to start it you have to have a safe
landing area, be in circuit with a safe approach path calculated otherwise when
it fails to start, and chances are it will fail, you endanger yourself your
friend and your beloved glider! Field selection and land out areas are just as
important to us in the Nimbus as any glider on a any cross country flight!
Whilst discussing our options, which included an in depth botanical discussion
on the thermal producing properties of bracken ferns or marram grass or
whatever covers Dartmoor we noticed a small ragged cloud forming over
the moor, we therefore decided
to head out on track. Initially we were rewarded
with lots of sink but a fantastic
view of the moor until we ran
into a much needed 7kt climb over HM Prison Dartmoor!
Conditions
heading west were still looking
very blue, with 90km to go to Truro we
continued to 'tip toe' west. Under these 'blueing out' conditions it is
sometimes important to look at the ground for thermal sources rather than focus
on the sky like we normally do. A little off track, we
couldn't help but notice the enormous China Clay quarries near St Austell. Reverting to gliding basics, GP remembered that quarries are good thermal sources(!) Deviating to fly over
the quarries we were quickly rewarded with another 7kt climb which took us back
to 5000'. Happy days.
From the top of this climb this we noticed that the clouds to the south of track had firmed up and were
ragged indicating the convergence we had hoped for! Making contact with the line of lift that a sea breeze
convergence produces it was a easy run in to the
Truro turn point and back out again
to the quarries. Looking south near Truro, notice the ragged
clouds with the varying cloud bases
indicating the convergence line. Looking North from the same position, notice the lack of 'convection' caused by the dead 'sea air'.
'In the sector' - a
good old fashion turn point photo of Truro
cathedral. Heading back home at 14:00L (13:00 UTC) we calculated that there was still a good 4 hours
soaring to do around 400km back to EDG.
Running the convergence back up
to St Austell. The sky ahead was looking
nice.
 |
| Streets at sea |
The seaside near St Austell - notice
the streets running out to sea.
The return leg was standard climb & glide, the blue conditions in
the Dartmoor area had been replaced with nicely spaced Cu giving regular 4kt climbs. We later suspected that we arrived in to
the Dartmoor area slightly ahead of the trigger point, before the 'good' polar air from the north had moved in to replace
the morning 'sea air' in the area.
Pushing back north around the Bath area there were
now large areas of
spread-out but the southern sunny cloud edges were still producing regular 5kt climbs. Opting for
a long 36km glide to stay on track we got low at Cirencester but heading for another quarry we were rewarded with a nice 5kt climb that took
us up to 6000' and close to final glide for EDG. A final top up, under spread-out, at Little Rissington allowed a nice
relaxed glide home for a 7:44 hour 648km out and return flight at an overall speed of 83 kph. A nice start to the season!
The final climb at 18:30L (17:30 UTC)
under spread-out.
Keep your eye on the forecast if you
notice cold & dry polar air, and plan something................big?
