I believe the origin of BDB came from when Bernd used to live in a tree and watch down on distance fly casters, occasionally squawking and often sketching, or something like that (Bernd Ziesche actually translates to ‘fish-catching big bird’ I think). After coming down to the ground he committed his studiously taken notes on fly line trajectory to paper and the rest is history. Unfortunately at times we seem to have collectively forgotten some of his musings, preferring to take on more fanciful descriptions of what’s going on with our loops. However, I’m here to remind you to take another long, hard stare at Bernd’s Dangly Bits and all will, once again, become clear.
None of us possess the ability to turn off gravity and this causes our lines to sag. This is hidden somewhat by the tension generated by the fly-leg pulling the rod-leg taught, but it’s still there and worsens dramatically once the fly-leg runs out. The crux of BDB is this sag, or any other deviation from a straight line e.g. tracking errors. In a vertically-orientated overhead cast, this means that the initial movement of the line nearest the fly is almost always going to have a downward element to it, and what goes down must eventually go up! (I’ve got that saying right, haven’t I?).
This was particularly evident to me last weekend when I was watching Tracy practice the S55 event prior to this weekend’s Game Fair. (The S55 is an overhead cast with a 15ft double hander coupled with a shooting head line). The line carry for this event is quite big, normally a ~60ft head, a few feet of overhang plus the length down to the hands – giving a total of maybe 75ft. Tracy hadn’t practiced with such an outfit for quite some time (3 minutes of competition doesn’t really count as practice), and what was clear was that she was ticking front and back, evident from the dimples in the water about a rod length or two from her feet. Now BDB absolutely predicts this and offers a solution – stop the sag! Without the recourse to turn off gravity the next best thing is to take the next casting stroke slightly earlier. Tracy has a habit of watching her forward cast fully unroll before commencing the back cast, now this is all well and good for a normal length cast but perhaps not for when you’re carrying 75ft of line. A minor timing adjustment to take the cast whilst there was still some loop in sight (but not enough to crack it like a whip) and the ticks disappeared. A resounding triumph for BDB! As a slight aside, one of today’s pictures shows me starting the back cast with the same outfit, this is a straight as I can get the line aligned and you’ll still notice that there is some sag present.
Another of today’s photos is one that I’ve used a lot, my unfeasibly pointy loop from the world championships in Estonia. I should thank Ross Bannerman from the Jersey team for taking this shot and for putting his camera in the perfect plane with my loop to make it look so sharp. Anyway, the important thing as far as BDB is the other end of the line, i.e. towards the fly. Take a careful look at how the end of the fly line has tucked itself under at a seemingly weird angle. Actually it’s not that strange as BDB predicts it if there was a lot of sag – and I was casting a long head in sticky-hot conditions so I’m pretty sure there was plenty of sag. Now ask yourself if the line could get into that position if aerodynamic drag was an overriding factor influencing loop shape? Surely the line should look to align itself into a position that would minimise drag, but here it’s doing the exact opposite – massively increasing the area (and thus the drag force) presented to the airflow. If there’s one aspect of fly loop shape that tells you which is king between momentum and drag, then this must be it?
Finally take a look at the overall trajectory of that cast. Then go back to BDB and look at where the dangle ends up (very similar to last week’s FP where I was roll casting). Then perhaps take a fresh read of the ‘aerodynamic loop lift’ discussions. I also have many photos of my fly in ‘unfeasibly’ high positions in relation to the loop, but again these simply match the simple brilliance that is BDB without requiring any additional lift.
Today Tracy and I will be joining ‘camp BFCC’ at the Hatfield House Game Fair for a weekend of casting competitions, socialising, BBQs and drinking. If you’re going then please come down to the river to say hello or to have a cast.
Have a great weekend, James.