Archimedes, Mark Wintle, Graham Marsden and Peter Drennan

[RUDD]

Several years ago I read Allan Haines "The complete book of match fishing" and also "The complete book of float fishing".

 

In one was a section about a hollow tipped waggler designed for fishing at distance so anglers could see tip but reduce residual bouyancy.

 

Yesterday I was looking through "Pole fishing a complete Guide" by Graham Marsden and Mark Wintle and I for some reason came across on Page 72 paragraph 3. :

 

"The tip material has no effect on its residual buoyancy, which is affected only by the volume of water that remains to be displaced. If you disagree with that statement you will have to prove Archimedes wrong."

 

After reading above I come across this article by Peter Drennan " Stillwater blues" in which he states:

 

In the main the thinner the antenna the better the bite indication will be, but there are two other factors which influence bite registration.

The first one is the weight of the antenna material and the amount of buoyancy left in the portion sitting above the surface. If the material is dense and heavy with little or no residual buoyancy left

in the tip, you will tend to get big, slow, exaggerated bites.

It’s why wire tipped pole floats are so sensitive; there is no buoyancy at all in a wire pole float antenna, just dead weight. As a result they are extremely difficult to shot accurately, can only be fished in the calmest conditions and they have to be greased to hold their position in the surface

film. But of course, they just sink right out of sight in response to the merest indication, providing long, slow, practically unmissable bites. Exactly the opposite applies with ultra light weight, highly

buoyant material like a fine Peacock antenna, which wants to pop back up to the surface as fast as it can. With such buoyant antenna you tend to get quicker, more staccato dips from shy biting fish which by comparison are much more difficult to read, to time and to strike. Bamboo cane dowel is, sort of half-way between these two extremes. It’s neither

so dense and heavy that it’s difficult to shot and gets dragged under by the slightest breeze or drift; nor is it so light and buoyant that you only get quick little dips of the float from shy biting fish. In fact Bamboo is a uniquenatural material; lightweightand moderately buoyant but incredibly tough and strong."

 

OK - with me so far?

 

Archimedes' principle is a law of physics stating that the upward buoyant force exerted on a body immersed in a fluid is equal to the weight of the fluid the body displaces. In other words, an immersed object is buoyed up by a force equal to the weight of the fluid it actually displaces.

Archimedes' principle relates buoyant force and displacement of fluid.

 

However, the concept of Archimedes' principle can be applied when considering why objects float. Proposition 5 of Archimedes' treatise On Floating Bodies states that:

 

Any floating object displaces its own weight of fluid.

 

 

In other words, for a floating object on a liquid, the weight of the displaced liquid is the weight of the object. Thus, only in the special case of floating does the buoyant force acting on an object equal the objects weight. Consider a 1-ton block of solid iron. As iron is nearly eight times denser than water, it displaces only 1/8 ton of water when submerged, which is not enough to keep it afloat. Suppose the same iron block is reshaped into a bowl. It still weighs 1 ton, but when it is put in water, it displaces a greater volume of water than when it was a block. The deeper the iron bowl is immersed, the more water it displaces, and the greater the buoyant force acting on it. When the buoyant force equals 1 ton, it will sink no farther.

 

Based on above statement and Peter Drennans article I can only conclude that Mark/Grahams statement " the tip material has no effect on its residual bouyancy" may be false and Peter Drennan correct.

 

No disrespect intended towards Graham/Mark as the rest of the paragraph is true (ask Archimedes):

 

3. the tip material has no effect on it's residual buoyancy, which is affected only by the volume of water that remains to be displaced. If you disagree with that statement you will have to prove Archimedes wrong. As far as this is concerned what is worth knowing is that if you double the thinkness of the float tip then you quadrupal its buyancy. this is why ultra thin wire float tips are so dificult to shot up yet nylon ones that look only slightly thicker are manageable. Althoughthe Nylon one is only half as think again as the wire it is twice as buoyant.

 

 

Confused? Can someone clear this up for me?

 

 

Ok heres a quiz with the answers taken from " Advancing Phyysics chapter 10, 190S to help make sense of matters:

 

Bobbing floats

Archimedes’ principle states that the up thrust acting on a body immersed partly or wholly in a fluid is equal to the weight of fluid displaced.

A cylindrical fishing float is 15 cm long, with an average cross section of 3 cm2. It is made of polystyrene and has negligible mass. A lead weight of 30 g is attached to the bottom of the float using a thin nylon monofilament line.

g = 10 N kg–1

 

 

1q. Assuming the weight and line to be of negligible volume, calculate how far will the float sink into the water?

 

 

1a. The up thrust must support 30 g, so the up thrust is 0.3 N.

The float sinks until 0.3 N of water is displaced. Length of float submerged = h.

 

2q. A fish pulls on the baited hook further down the line and pulls the float down a further 3 cm before letting go. Calculate the resultant force on the float as the fish lets go.

 

2a. Additional volume displaced = 0.03 m  3  10–4 m2 = 9 10–6 m3

up thrust = Vg = 9  10–6 m3  1000 kg m–3  10 N kg–1 = 0.09 N

 

3q. Show that the restoring force is proportional to the distance that the float is pulled below its rest level.

 

3a. F = density  area  g  additional length submerged, therefore the force is proportional to the additional length submerged.

 

4q. If the float is lifted slightly by the angler and dropped, show that the force is again proportional to the distance above the rest position.

 

4a. Lifting the float involves the same calculation, with the decrease in up thrust being calculated, which is then the resultant force downwards.

[Steve Walker]

All that matters is cross sectional area.

 

On the matter of weight of water displaced equalling the weight of the object - that reflects the average density of the whole object, not the density of the specific part which is emergent.

Edited August 10, 2012 by Steve Walker

[Mark Wintle]

I'm afraid Mr Drennan doesn't know what he's talking about when it comes to residual bouyancy! Of course Archimedes might be wrong....

 

If tip material did matter then a test float that I have which has a steel (density about 7) antenna one end (diameter 3mm) and a cane antenna the other (density 0.8) also 3mm in diameter would be affected differently by the same no. 4 shot according to which way up it was. Of course it isn't affected differently. In fact according to Drennan it would be impossible to keep the steel end afloat. It is possible using physics to calculate the effect of a given shot on an antenna given its diameter.

 

The hollow tipped antenna is a brilliant idea and I have several floats so equipped.

 

The 'popping' up effect is more to do with inertia and overall density of the float than the tip material.

[Old geezer]

I'm probably wrong, but I take no notice of this kind of stuff. IMHO a small, very light float usually flies away and pops up again almost immediately as a result of the interest of small fish pecking at the bait. A larger, more heavily shotted flooat, is slower to react to such interest and as such the momentum of the attak is not as noticeable. A confident take will mean that the float disappears and stays that way. I have had hesitant bites from large wary fish on many occasions and the signals are usually slow hesitant "twitches" where the float seems to just bobble slightly and then usually develops into a determined bite.

 

I tend to sit at the bankside and determine which float seems right for the circumstances and use it........

 

Perhaps it's just me, the old git, who doesn't get phased bt the science of it all and just goes fishing.......

[Phone]

Mark,

 

The way I read the passage. The intention is that if the weight above the universal cross section line is lighter the force from above will be less.

 

I believe he is trying to make the float verticle while having unequal pressure density (upward force). Thus, a much lighter float could set higher or lower in the water.

 

Something like that. I'd have to think it out to say it better. What I have in my mind is a picture of a inverted hot air balloon. In that case the more detailed adjustment is at the bottom rather than at the top.

 

Phone

 

What if any would be the importance of knowing or using such a finely detailed float.

[Phone]

Mark,

 

Well, where is everyone? I'm now interested myself.

 

From the avalilable text it's hard to determine what the author means with statements like - "...better the bite indication..." wonder if "better" means simply easier to see?

 

I can't see the conflict. When you have to grease a float for buoyance you're way out of my league. That adds things like surface tension - blah blah.

 

Phone

Edited August 11, 2012 by Phone

[Steve Walker]

It is counter-intuitive, but it's right - the material doesn't matter. I was trying to think of a thought experiment that would show how it works, but Mark has a practical demonstration with his reversible float.

[Ken L]

The factors that are relevant here are the volume of tip sticking out of the water (Achemedes principle), the mass (and consequent inertia) of the float and it's shot and the degree to which the float and it's shot are streamlined to reduce drag.

 

To increase visibility at distance without increasing the volume of the tip, the two options are either a "Dart flight" type tip or a hollow tube like a drinking straw with a hole in it so water can flow through.

Years ago, I fitted a couple of big wagglers with cut down dart flights that had been painted blaze orange and they worked a treat for bream fishing at range - the paint did have a tendency to flake off though.

These days, I suspect that you could just go out and buy flights in a range of colours.

 

Sure enough

[ayjay]

Well, where is everyone?

 

 

Phone

 

At 3.29 a.m. UK time, the sensible ones were pushing out the zzzzzzzzzzzzzzzs.