Mo,

Yes, I'm aware and this is another reason to set the guide ring edge on the plotted line path - it will stop all that motion on the retrieve as well.

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Mo,
I'm unfamilar with the calculations for the wind resistance your concerned about, but attached are the calculations for the centrifugal force.

Assume
cast velocity = 30MPH
spool dia = 2 inches
spool radius = 1
distance to first guide = 20 inches
line dia = .010
Line weight @ 20 inches = .0000567 lbs ( .0257 grams )
RPM @ 30MPH = 5042RPM

Formula for centrifugal force (Courtesy Machinery Handbook) F=.000028416Wrn^2
F=centrifugal force in lbs ; W= weight of object in lbs ; r= rotation radius in inches ; n=RPM
F= .000028416 * .0000567 *1 * 5042^2 = .04096 lbs force ( 18.58 grams) or 720 G's

I'd say that 720 G's of load is much greater than the wind resistance of 20 inches of .010 line in a 30MPH breeze. I doubt that it is over 1 gram. Certainly much greater than the effect of gravity alone.

This is only on the cast dynamics. If the velocity is doubled the load will increase 4x, if the spool dia is halved the load will increase 2x.

I've tripled checked the math but I'm still capable of mistakes.
Michael if you'll recheck the numbers I'd be obliged.

Gene Moore

No, the drag of the line through the air is the greater factor.

That .010 diameter line also has length. Once you multiply that you realize just how much drag is present.

Surface drag or resistance, pales in most cases to frontal drag. And because the line is revolving in a coil, you have a tremendous amount of what for the most part is frontal drag.

This is precisely why spincast reels cast so very well compared to standard spinning reels.

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I'm a Mechanical Engineer.
I'll require a lot more proof then "I say so"
The floor is your's.
Submit your proof and convince me.
The line is still only .010 and round in profile which is a fair areodymamic shape.
The length of line to the tip is the only amount being affected.
The max air velocity is still only 30MPH.

If you want to simulate a spin-cast you will need a guide with a foot length more closely matching the reel height to run the guide concentric with the reel. This can then be positioned much closer to the spool face to reduce the length of line influenced by the rotational speed. This will reduce the weight of line affected but it will still be at 720 G's. I believe this may be where Mo is headed.
In this case the difference in spool dia to guide dia can give a convergance angle of approximately 30 degrees per side over the distance between the spool and guide.

Gene



Edited 2 time(s). Last edit at 09/04/2009 12:23PM by Eugene Moore.

I am also a mechanical engineer with a background in aeronautics. Working with "drag" was a large part of my job.

Surface drag and frontal drag are not nearly equal. Frontal drag being vastly more of a factor than surface drag in most instances. If you throw a 2x4 spear fashion, it will go further for the same effort than if you turn it perpendicular and throw it that way. One position exposes more frontal surface.

You are not working with a simple .010 diameter - you are working with a long length that is revolving. You actually have several square inches of frontal drag in play - You have motion in more than one plane and the revolution of the line has turned the 2x4 perpendicular. You also have many yards of overall surface drag, although that only becomes an equal factor once you get enough line beyond the reel and it would take a great deal to get to that point.

Numbers are great, but you have to apply them correctly.

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If you believe that the friction created by centrifugal force pushing the line against the guide ring is truly a large factor, remove the guide and try casting that way.

The larger the coils are allowed to billow out from the reel, the more drag you incur and the more distance you'll lose.

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Just a moment on the lighter side...........

Using numbers to prove something reminds me of the old Foghorn Leghorn cartoon where he is playing hide and seek with the widow’s son. Foghorn hides and then the kid does some calculations and walks over to a woodshed and points at it. Ol’ Foghorn walks up and says, “I say, I say, boy, you’re all wrong, I’m not in there.” So the kid hands him the page of calculations and Foghorn looks it over, turns to the camera and says, “I better not look, I say, I say, according to this, I just might be in there.”

If you look at that formula you will see that that is handled also.
As the line is allowed to billow out the radius increases as does the weight of the line and the force will increase. My numbers are deliberately conservative with the assumption that the line is held at the spool dia which we know is not the case. It's always larger and how much larger is a function of the cast velocity. I also assumed the spool was filled to the lip giving the minimum RPM attainable. If that's the best proof you've got you may fail physics.
I'm also aware of the total swept area you are talking about but the line only displaces a very small percentage of that at any instant in time and the maximum area of the line is still the dia times the rod length.

Wish Denis were here.

Gene



Edited 1 time(s). Last edit at 09/04/2009 01:07PM by Eugene Moore.

Now back to seriousness. It would seem to me that casting and spincasting rods throw the line in spear fashion then. A spinning reel is partially throwing the line in spear fashion up past the first few guides but also out and around near the reel like that broad faced 2X4 you mentioned. So a lot more drag is present. This has to be the reason that spinning reels don't cast as far or quietly as casting and spincasting reels do. Never thought of it that way but it makes sense.

I would also make the assumption that this is why a smaller butt ring adds distance.........you reduce the size of the revolving coil of line which cuts down on air resistance.

Mo,
Is this where you're going ?????
Open face spinning control guide set-up
Control guide dia = 1/2 spool dia
Control guide location = 4 times spool dia in front of spool
Rotate reel to aim at center of control guide. (Use shims under rear foot and tape for mount)
Set remaining guides off choke guide and control guide

Wish Denis were here

Gene

You have a great deal of frontal drag with the line on a cast made with a spinning reel. That line diameter coupled with the length involved creates a fairly large area. And it grows as the line diameter increases.

This is the main reason that spinning reels have trouble matching the casting distance of spincast or casting reels. And this isn't an assumption - it is the primary reason for the difference in casting distance between these types of reels.

...............

Eugene, I have checked your numbers and find no problem with them. However, I don't know if 720 grams of force on a guide is significant relative to the other forces at work. Keep in mind that you are talking about friction on the guide which will slow the line. To find that force you have to multiply the 720 grams times the dynamic coefficient of friction of the line with respect to the guide. I would estimate that it would be on the order of 10 percent, not a lot higher than a tire on ice? If that were the case, the axial restraining force due to centrifugal force would be 72 grams.

I don't know what 72 grams really means relative to the restraining force on the line. I do think that the air resistance is really significant to the issue of what is slowing down the line. If it were not so then we whould have no advantage in controlling the line early. I also agree in concept with what Tom is arguing, that it isn't just trying to move .010 width of line through the air, you are trying to move a lot of .010 widths (times a bunch of lengths) through the air. And as you have demonstrated with centrifugal force, you're doing it very fast. The line being acelerated outward from the theoretical line path takes energy, and air resistance slowing its radial velocity takes energy, and slowing its axial velocity takes energy. All of this energy is taking energy from the lure. What we want to do is to minimize this energy loss, and therefore, I belive the most significant logic in the whole thing is: The advantage of controlling it early must mean that the energy cost of controlling it (getting it through the guide) is less than letting it billow without control and controlling it late.

Now, how to do this is what we have been discussing. Is it more efficient to do it by aligning the theoretical line path with the edge of the guide or the center? Tom argues from years of experimentation that it is the former. Now, does anyone have any DATA that can prove that the centerline alignment is better?

All the rest of this is fun discussion, and for us retired engineers, it's good to get the juices flowing again, but I maintain this is such a complex system that we are not going to solve it theoretically. We just need to keep running the tests, sharing the data, and helping each other analyze what we observe.

I have the data taken from tests with a mechanical casting machine. And you're correct, there are a lot of things happening simultaneously on a spinning rod cast. Drag on the line is a major factor, however, much more so than friction between line and guide/s.

What Ken has just proposed is more of a competition than a test of any one variable, but it would be fun and beyond a certain level I think the differences would come down to guide selection and set up. And it would get a lot of guys out of the house this Fall and Winter building and testing.

[rodbuilding.org]


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Michael.
Don't misquote me.
The force is 18.58 grams the equivalent of 720 G's.
This is the force moving the line outward which must pulled back by the first guide.
Certainly friction between two surfaces in contact is greater than that of air.
There is only 1 line width moving down the length of the rod.
That one line is in rotation about an axis but it's total area is constant.
That single line area is the only thing moving perpendicular to the air.
On a 6 foot rod it's about the size of a quarter.

Friction between surfaces is dictated by the pressure forcing them against one another.

The drag of the line's frontal surface area is more of a casting impediment than the friction of the line against the butt guide ring on a spinning rod.

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