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Old 02-21-2006, 06:24 AM
GrantK GrantK is offline
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Backing Math?

If a reel will purportedly hold a WF9F and 240 yds of 20 lb. dacron backing, how much 30 lb. dacron backing will it hold with a WF8F? Anyone have a formula of sorts for guesstimating in instances like this?
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Old 02-21-2006, 07:26 AM
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Some reel manufacturers publish capacity data for both 20 and 30 # backing for a subset of the reels in their product lines as well as backing data across a few flyline sizes...If you stare at it long enough with a little simple scaling you can probably apply it to your specific problem. The alternative is to try to find line diameter info for the backing and assume that the capacity goes as the inverse of the diameter.

See post below using data from one source.
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Last edited by jfbasser; 02-21-2006 at 01:15 PM.
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Old 02-21-2006, 11:02 AM
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Try (240 x diameter of the 30 lb) / diameter of the 20 lb
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Old 02-21-2006, 12:27 PM
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Using info on the Abel website and scaling, expect to use 225 yds of 30# with that 8 weight line.
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Old 02-21-2006, 12:47 PM
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Quote:
Originally Posted by Dave17
Try (240 x diameter of the 30 lb) / diameter of the 20 lb
Clever! But I believe the formula would be (240 x diameter of the 20 lb) / diameter of the 30 lb)
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Old 02-21-2006, 02:19 PM
GrantK GrantK is offline
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Thanks for the replies. The formula provided works pretty well for converting from 20 lb. dacron to 30 lb. dacron, but of course it doesn't account for the difference in line size.

Using some numbers I found in a saltwater article that purported to list the average diameters of dacron as .018" for 20 lb. and .024" for 30 lb., I came out with a number of 180 yds of 30 lb. in the place of 240 yds. of 20 lb.

Anyone have a method for guessing the difference between line weights? And yes, I know all I have to do is spool it on there and then I'll know. That's not the point here. I'd like to come up with a way to try and fairly accurately standardize and evaluate--within reason of course--capacities from one maker to another.
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Old 02-21-2006, 02:32 PM
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Thats better derived from a reel co's ratings of one line wt vs the other line wt on same backing then applying the ratio. For instance reel brandX says 8wt and 240 yds of 20 or 9wt and 190 etc.

If you really care you can go wind the line first then the backing over and reverse it onto another reel at a shop, but most of the time I put on as much as I think I can get away with, wind on the line and pray.

For my bonefish reels I go with 50# gelspun and load 'er up.
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Old 02-21-2006, 02:33 PM
Bob Pauli Bob Pauli is offline
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All backing is not the same. Some 30# dacron takes 15% more volume than others. A reel that holds 250 yards of white SA backing will hold about 213 yards of colored Micron backing [both 30#].

It is worth reading Abel's literature or web site. You will notice the specs are for SA backing only, white color only, with reductions for other material.

SA is the smallest diameter backing I have found, hence more fits on a reel. Wulff oval backing is the next smallest. Abel uses SA in order to maximize backing capacity. Micron is among the largest diameter dacron backings, and is used in Tibor advertising.

If you choose a colored backing material, you will lose capacity.

If you search prior posts on the subject you will find an angler can get major increases in the amount of backing installed by using white material from SA.

Last edited by Bob Pauli; 02-21-2006 at 02:39 PM.
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Old 02-21-2006, 03:00 PM
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Quote:
Originally Posted by Bob Pauli
SA is the smallest diameter backing I have found, hence more fits on a reel. Wulff oval backing is the next smallest. Abel uses SA in order to maximize backing capacity. Micron is among the largest diameter dacron backings, and is used in Tibor advertising.
So True! I had a Riptide spooled up to the capacity line on the spool which is supposed to be 250 yards of 30# dacron. It took well over 300 yards of Orvis 30#dacron to reach the line. Probably the same stuff as SA.

In fact the 30# Orvis Dacron is so close in diameter to 20# Micron it's tough to tell the difference.
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Old 02-21-2006, 03:24 PM
GrantK GrantK is offline
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[QUOTE=juro]Thats better derived from a reel co's ratings of one line wt vs the other line wt on same backing then applying the ratio. For instance reel brandX says 8wt and 240 yds of 20 or 9wt and 190 etc.QUOTE]

Absolutely. Problem is that there are reel makers that don't provide that information. They have one line size listed with one size of backing for a particular model. Unless the reels you're comparing, from one manufacturer to another, are both quoted with the same weight lines and same type backing it is very difficult to compare them in terms of capacity. My question was more of whether anyone had ever come up with, or heard of, a general ratio for changes in line size, e.g., 10 percent more backing with one line size smaller and conversely 10 percent less backing with one line size greater. Obviously there are a ton of variables from brand of backing (and even color apparently) to taper of line that will all have a big impact and make such an estimate pretty inaccurate, but I would think there could be some general figure in terms of the difference that could be applied that would at least get a person into the ballpark.

And like I said before, I know I can spool backing and line on any reel and know exactly how much it took. That's not the point, though.

Also, anyone know of a listing for diameters (in thousandths) of any of the various brands of GSP? The basic catalog type listings generally make reference to an equivalent in monofilament. Curious if there's anything more accurate out there? Anyone have a formula they've used for converting dacron to GSP? I've seen a copule real simple formulas in the past, but have heard of wildly differing experiences using them.

Last edited by GrantK; 02-21-2006 at 03:27 PM.
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Old 02-21-2006, 03:27 PM
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Quote:
Originally Posted by juro
Clever! But I believe the formula would be (240 x diameter of the 20 lb) / diameter of the 30 lb)
Here's my thinking:

20lb / 240 yds = 30lb / x yds

Cross multiply:

20lb * x yds = 30lb * 240 yds

solve for x:

x yards = (30lb * 240 yds) / 20lb

The forum gets algebraic
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Old 02-21-2006, 04:21 PM
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Yes, impressive! And the best answer of all, I am just saying it was 240 of 20 not 240 of 30 and you are solving for amount of 30lb where 20 is already known.

The logic is awesome, however if you run the diameters thru it you will see what I mean. You should get less 30# than 240yds.

Who woulda' thunk this would ever be fun!
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Old 02-21-2006, 05:06 PM
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Juro, this is what your looking for..I think

More pound test (larger diameter) requires less yardage of backing. they vary inversely!

Two objects that vary inversely are also said to "vary indirectly" or to be "inversely proportional."

One quantity is inversely proportional to another when the product of the two quantities is constant. An inverse proportion can be described by an equation of the form xy = k, where k is the constant of proportionality. The equation of an inverse proportion can be written in the form .

240 * Dia20 = k= X * Dia30

X= (240 *Dia20)/Dia30

Given that the Diameter of 20 is about 4/5ths ( .8) the Diameter of 30

X=240 * 0.8/1.0

192 yards of 30#

As for fly line weight and its effect as stated above Abel's site is as good as any. Winding the line on first is good, but I like Juro put more then enough on, then wind the flyline on and figure out (guess) how much backing to clip off based on how much flyline is left sticking off the spool. On certain reels where I have been known to use intermediates one day and a sinker some other day I find that a 120 foot sinker takes up about as much space on the spool as a 105 foot Intermediate.
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Old 02-21-2006, 06:57 PM
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Orvis lists three line weights for some of their reels. Batenkill LA comes to mind. I think that based on those differences, you could apply it to any reel.
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Old 02-21-2006, 07:28 PM
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Hmm . . .

Seems to me that it's actually an inverse-squared relationship since we're really talking about volume. This yields the same equation as Basser except that the diameter values would be squared, so using the same assumption as above (i.e., diameters have 4/5 ratio) the result would be 153.6 yds of 30#. The ratio has a huge effect on the result so it might be quite different when you plug in the real line diameters.

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