A question about convergence

[morgy]

Hi all

On fri 05 i had an other good xc flight out of pulbrough. This time i had company we planned to do a down wind flight from our take of field in pulbrough to bo peep in lewis. I we managed to take of in a light 8mph nw but when we got to bo peep in lewis the wing was coming straight from the sw and strong about 15mph poss 20mph in the compression zone at the top of the hill where our pick up was waiting.

On the way to the landing zone on Bo peep the air got very rough to rough to blame on thermic activaty. My question is when your flying into or near convergence is there a area of extreme turbulence? If so how does it work? I kind of understand how the sea breeze comes in in a wedge. but i dont understand why or how there was so much turbulence.

[Guest]

Looking at the above may help to ID the rough area of a Sea Breeze convergence. This of course becomes even more interesting when you are on a peninsula (like Cornwall)

SW

[morgy]

Thanks for that Si

Looking at the picture i could have been in between the thermic ups and the down drafts.

I suppose you have to take the rough with the smooth!!! I alway thought that sea breeze convergence was smooth all the way through.. How wrong i was. I have flown in it before and it was a smooth 2-3up all the way with my motor on tickover and trims set on neutral.

[Guest]

Well,

At least you know now, and I bet you don't forget either

SW

[morgy]

The only thing i have a problem is how do you know what part your in??? ie if your in bad lumpy air do you fly into it?? or try and go up and over it to get to the smooth air? sea breeze is a great tool to go XC i want to know the best and safest way to use it.

I suppose practice makes perfect

[norman]

The lift band down a sea breeze front in the UK can be very narrow, perhaps a couple of hundred yards at times with 'pebbles' either side. There are few if any markers to find the lift - experiment.

Although a US site the clues below stand good for the UK except that we don't often see 'dust'.

From Aviation Weather

VISUAL CLUES

When a sea breeze front develops, visual observations may provide clues to the extent of lift that you may anticipate, viz.:

1. Expect little or no lift on the seaward side of the front when the sea air is markedly void of convective clouds or when the sea breeze spreads low stratus inland. However, some lift may be present along the leading edge of the sea breeze or just ahead of it.

2. Expect little or no lift on the seaward side of the front when visibility decreases markedly in the sea breeze air. This is an indicator of stable air within the sea breeze.

3. A favorable visual indication of lift along the sea breeze front is a line of cumulus clouds marking the front; cumuli between the sea breeze front and the ocean also indicate possible lift within the sea breeze air, especially at higher levels. Cumulus bases in the moist sea air often are lower than along the front.

4. When a sea breeze front is void of cumulus but converging streamers of dust or smoke are observed, expect convection and lift along the sea breeze front.

5. Probably the best combination to be sighted is cumuli and converging dust or smoke plumes along the sea breeze front as it moves upslope over hills or mountains. The upward motion is amplified by the upslope winds.

6. A difference in visibility between the sea air and the inland air often is a visual clue to the leading edge of the sea breeze. Visibility in the sea air may be restricted by haze while visibility inland is unrestricted. On the other hand, the sea air may be quite clear while visibility inland is restricted by dust or smoke.

[morgy]

Hi thanks for the info norman

I have to say of that on the day of the flight it was mostly a blue thermal day with the odd cu about so we had no warning of a sea breeze front coming in or that it had come in untill we were in it and nearly coming into land backwards.

I have another question and may be i should start another thread but i wont!!!

When we came into land the wind was strong how should you bring the wing down???? I came in on over take off and poss on neutral setting on the trimmers. "my ground speed was slow" my normal thing in high wind on the hill when i free fly would be to grab hold of all the d lines and pull hard to collapse the wing i also run towards it but with a motor on your back i found it hard to pull in the d's and run as i was being pulled into the air again.

On my old PG wing i could pull hard on one A riser/or both and the wing would fall to the ground in a second will this work on my Fusion due to its reflex stopping it from frontal collapse.

Or is there another way to bring the wing down that i dont know of???

[fanman]

Approach on a fast trim setting, it's really not as scary as you think, you just need to do a full flare. Then bring the wing down on the C's rather than the D's.

[Guest]

Also,

I tend to put a tip down and lower the rest of the wing in to a little pile. (a reversed cobra launch)

If you are going to do the 'c' or d thing. go for the c's

SW

[fanman]

Yes, the reverse Cobra is definitely worth doing as an alternative to the C's.

[morgy]

ok thanks guys

I think its back to the ground handling field again

[helimed01]

Looking at the above may help to ID the rough area of a Sea Breeze convergence. This of course becomes even more interesting when you are on a peninsula (like Cornwall)

SW

This time of year the sea temp is often warmer than the air temp re versing the image but same effect.

Without convergence you can get big smooth sea thermals on the coast this time of year. early this month I flew with Dan from Dawlish to near Axminster along the coast, the wind was on shore for ost of the route on the cliffs and it was nice to fly along with only 1/4 revs in the bouyant conditions.

It would have been excellent Lands end to Dover coatal run conditions with x-wind 28mph ground speed.

Whitters