Drag and Tail Winds

[Lee Cummings]

Many of the furthest casts thrown in the world have been done right here in Cumbria (at sea level, in heavy tail winds).

How does drag have an influence on the forward cast in such conditions?

[Walter]

Hi Lee,

I’m not sure what you are asking. Are you talking about how a tail wind affects drag, lift, turnover or something else?

Thanks for your videos btw.

[Paul Arden]

Well in this case drag certainly isn't floating the loop. The wind speed in Cumbria is not far off the line speed in a distance cast (OK it's maybe half!). It would be interesting to time how long it takes for the loop to unroll, to measure at what distance it unrolls at, and to measure how far it travels after LSP.

I'm guessing that it unrolls quicker - might be wrong. I don't know if it will completely unroll at a longer distance or the same - I'm thinking further. And I'm sure it will carry further after LSP. (The problem I had in Cumbria was that the strange wind rising from behind made it very difficult to lower the backcast, making the higher forward cast necessary to capture this carry effect after LSP almost impossible.)

If drag was lifting the loop then I think we would have shorter duration flight times when throwing with the wind. But I'm not on the same page here.

Cheers, Paul

[Walter]

If drag was lifting the loop then I think we would have shorter duration flight times when throwing with the wind.

That would certainly be true if we thought the thing causing the lift was the bit of inclined line on the bottom of the loop and we thought it was it’s relative wind velocity that was creating a force normal to that incline.

If the wind was half the line speed it would be around the loop speed. If (and this is a big if because I don’t think it is so) the inclined bit is moving at the same speed as the loop that would mean lift (if lift actually existed in a cast with no wind) would be zero in this case and we would expect the line to fall like a lead weight initially until drag in the Y direction started to slow it’s fall relative to that of a lead weight.

But I think that most of us are beginning to agree that lift, of the form that acts like a wing to keep the line suspended in flight, isn’t significant.

I think what would be more interesting and meaningful is how the wind affects turnover and how the line would continue to propagate after LSP. I’m often reading about distance casters taking steps such as line tapers and overhang to slow turnover. A strong wind is going to force turnover to happen earlier than would normally be desired.

Maybe someday I’ll design a fly that acts as a tiny parachute and sign up to compete...

[Paul Arden]

I asked Steve Rajeff about using overhang to control turnover. He wrote that they used to do this but instead is now using shooting line of different diameters.

It’s actually quite possible to cast at line speeds of less than wind speeds, in fact in Cumbria this is likely and these loops don’t noticeable drop.

I do think lift exists. But I’m not seeing it in the way it’s being described in keeping the loop airborne. If I angle my backcast upwards at angle to the wind, yes there is a problem. Instead of straightening the loop blows back at me. In these circumstances I lower the trajectory of my backcast, and use a high forward cast to facilitate this. But what I have never had to do, ever, is to alter my trajectory as my line speed increases.

In the log video I’m backcasting into a wind, I have high line speed that can be measured, and that line drops in the ballpark of free falling line. These are the very circumstances that we should be seeing lift.

At first I was surprised with this video. I’ve seen many casts where the loop stays reasonably level and then drops after LSP. But when I look at these videos I can now clearly see that hey have all originated from a low backcast angle.

Cheers, Paul