Fly Weight - Interesting observation

[BrownChickenBrownTrout]

So I went through all my flies and weighed them with a grain scale (A scale used for loading bullets), precision down to 0.01g.

I found that there is a huge difference between like flies, and sometimes up to a 2:1 difference between Tungsten vs Brass bead heads (for flys of the same dimension and recipe).

WARNING, TECHNICAL BS COMING!
Flys that look identical, can have almost a 50% difference in weight. So what does that mean? If you take the terminal velocity equation in a fluid you can derive that the the lighter fly sinks at only 71% the rate of the heavy. Now maybe you can cast farther upstream, or adjust the rod angle, but in tight pocket situations, weight will always win out.

Some info on Fly weight ratios for terminal velocity (light/heavy):
2:1, 71% V1:V2
2:3, 81% V1:V2
3:4, 86% V1:V2

I think the closer ratios start to probably get to be essentially the same for our purposes. But 30% could be a huge difference in drop rate in a tight pocket.

Now it also means that your if you have two flies in your rig, that having radically different weights, Cd, and frontal areas could mean you have your anchor fly dragging your point fly down like a kite. But it also means that theoretically two radically different flys could be balanced and hit the sweet spot and drift at exactly the same point in time.

Food for thought....

[AaronJasper]

That was really good. I hear you on your observations and they are spot on. You guys better read this one! Nice work Dave.

[sal669]

Very good post!!!
I kind of noticed the same thing, but didn't go through the process of weighting the flies. Most often, when I am picking out the anchor fly (most of the times a tung head stone) I take 3 or 4 out of my box and weight them in my hand. I will chose the one that feels heavier or lighter, depending on the characteristics of the stretch of water in front of me. I do this even though all the flies in the same compartment were tied following the same recipe.
I did this unconsciously; after all, the same flies tied on the same size hook with the same size tung bead and number of wraps of same size lead wire...etc...should weight the same, right?

[whheff]

Very interesting observation. Thanks for post this info.

[BrownChickenBrownTrout]

Some additional info:

Size 8 streamer hook: 12 cg
5/32 brass bead. : 14 cg
5/32 tung bead. : 31 cg
10 wraps of 0.35" Lb. : 38 cg (3.8 cg/r)

Here's two almost identical flies (8 vs 10) woven nymphs and they are more than twice the weight difference.

ImageUploadedByTapatalk1341850193.026286.jpg

ImageUploadedByTapatalk1341850211.841219.jpg

Now if Aaron will get me some of the secret French Lead.

Dave

[BrownChickenBrownTrout]

So here's a thought to add to it. If I went with a double bead on the ole Rubber legs from my calculation, plus the 10 wraps, I could get an estimated weight of upwards of 145 cg, I could get a 15% increase in drop rate. How awkward would a double bead fly look in a Rubber leg?

Just thinking out loud...

[Halliday]

Bead the head, wrap the wire, add another bead and then fill in with thread, chenille, and legs. That's how I double bead. They sink like a ton of steel in fast deep water.

[BrownChickenBrownTrout]

That's one way was thinking. Does the body still taper well? Does it matter or are you using different size beads?

[Halliday]

Sometimes I use smaller beads. I usually tie the legs on and then wrap it up using like size beads. It's kinda ridiculous looking but the fish don't seem to care. The fish don't pay attention to the hook hanging out of the bottom either!!

[BrownChickenBrownTrout]

So today while fishing the gorge, I used the two flys pictured above. I am a believer in weighing your flys for sure now! Water was very low and I was snagging a lot with the heavy woven but switched to some of the identical fly but marked as lighter weight and was immediately rewarded with fish on. Once I got that weight dialed in, I was able to drift easily in the "zone" with a nice point smaller weighted fly trailing and had takes on both flys all day.