Hauling and the 170

[gordonjudd]

corresponding to a delay in rod response (which is quite short with modern tackle).

Merlin,
I know that when you just clamp the rod and then release the line going over a peg near the butt of the rod that is attached to a large mass to raise a smaller mass attached to the line going through the tip(like Thorsten did in his experiment that showed an accelerating haul would increase the deflection of the rod ) the rod's response is related to its loaded frequency, i.e [1/(2.*pi)*sqrt(k/(mo+m)].

Thus the time for the rod tip to dip down and then return to its starting position for a 59 g tip mass on a rod with k=2.64 n/m and mo=6.2 g (giving a loaded frequency of around 1 Hz) was around .7 seconds as shown in the video below. The drop time for the heavier mass (and thus the duration of the acceleration of the haul) was around .6 s. Is that the kind of response time you are talking about, or are you using much smaller line masses or stiffer rods to get "quite short" rod responses?

Gordy

[Merlin]

Hi Gordy

Pedestrial cosine or bell shape does not really matter, they can be tuned to match a haul record but I prefer the first one because of its simpler form.

The video is interesting, when I mean "fast" about hauling, I characterize the time for the rod to react to the peak haul acceleration to get maximum rod loading. In my example (Paul's competition cast), it takes 50 ms for the rod to react to haul acceleration, meaning that for a tuned haul (depending on its duration), the peak acceleration must take place 30 ms before MAV (maximum elastic energy taking place 20 ms after MAV = pull angle effect with non linear rod stiffness) to get the best of the haul.

It would be interesting to get figures from your experiment: when does peak haul accel occurs by reference to RSP and when does max rod loading occurs by comparison to RSP. If the mass is moved by gravity only, then the comparison will not be possible I'm afraid.

In my example: RSP - max load = 80 ms approximately

Merlin

[Merlin]

Haul scheme.JPG (38.39 KiB) Viewed 6394 times

Hi all

Here is a simplified scheme for the 170 cast model. The key point for best performance is to tune the peak haul acceleration to get the best from the extra load. Then the PHV takes place somewhere between MAV and RSP for usual haul duration. If you want to take the maximum from peak haul speed at the same time, then you need a very long hauling time, which means that you are limited in peak haul speed value by the distance over which you can haul (your arms). At the other side of the range, a very brief haul brings risk for a tailing loop (a drop in tip path).

Merlin

[gordonjudd]

If the mass is moved by gravity only,

Merlin,
In Torsten's experiment the acceleration of the heavier mass is nominally constant and is driven by gravity and the effective mass of the two masses. It was around 8 m/s.^2 for the choice of masses used in that video. It took about 460 ms for the rod to reach its maximum deflection from the t=0 time when the heavier mass was released.

Could the fact that in this experiment the butt of the rod was clamped and in a cast it is being accelerated/decelerated during the haul account for the rather large difference in your nominal value of 80 ms vs the 460 ms measured value in this experiment?

I assume that Dr. McGlinn's prediction for the expected rod response delay time would be the same as your 80 ms value, so there must be some factor that would account for the difference in our response time values.

Gordy

[Merlin]

Good point Gordy

I started to give a look at a more conventional cast (Paradigm model). The difference between the timing for maximum elastic energy storage in the rod and peak haul acceleration is about 100 ms, and not 50 ms like for the 170 cast.

Merlin

[Merlin]

For the Paradigm with a mild haul (PHV = 4.6 m/s), you have to come closer to MAV. The peak haul acceleration must be placed earlier than for the long cast. There is no way to get advantage of direct and indirect effects, the duration of the haul would be longer than the one of the cast itself (to get an idea, take four times the difference between max line speed and PHAcc, it gives 4*[85+130+5] = 880 ms for the above example).

Merlin

[Merlin]

Hi all

For a stiffer rod (910) and the 170 cast, the "hauling window" can nearly cover all the timings in between MAV and RSP (place for PHV):

910 haul scheme.JPG (36.7 KiB) Viewed 6238 times

In that case you can even get the best from load and speed for a given PHV. However, a shorter haul (same PHV) can give a slightly better line speed (2%), meaning that the extra loading of the rod is slightly higher due to a larger peak haul acceleration. Hair splitting indeed.

The good news is that there is "plenty of space", about 80 ms, to set the PHV in between MAV and RSP and get a good performance.

Question for Paul: do you find a difference in easiness for tuning the haul between the HT6 and the HT10?

Merlin

[Paul Arden]

Hi Merlin,

Yes the 10 is much easier. So that fits. I actually find the HT6 far too soft for distance now that I'm so used to the 10. It takes a while to get used to the 6 again and I get to see some excellent examples of tails

Cheers, Paul

[Merlin]

Merlin

[Merlin]

I took two examples: the “paradigm cast” and the “170 cast / 906” models. The baseline is the non hauled model in each case. Figures for the hauled cast are averages from several cases.

Haul energy table.JPG (44.04 KiB) Viewed 6155 times

The share for each effect (indirect = elastic rod energy; direct = haul speed) is obtained by taking first the elastic energy change out of the line energy change. The “haul” part is the complement to get the total line kinetic energy improvement, maybe I should say it is the “non elastic” part. This is somehow an arbitrary definition, because we face the same difficulty than for a non hauled cast: we know what the rod elastic energy is, but we cannot say that the rest is pure leverage. Here it is not pure haul either: the share of haul speed effect at launch time gives the contribution of the haul speed at that very time and you can see that this “pure haul” concept brings different figures in the table. To get them I cancel the haul speed effect at launch time and calculate the contribution of it in the line energy improvement.

It is amazing to see that we get the same order of magnitude for the haul process than for the cast process (non hauled figures): 15% to 20% are coming from extra rod elastic energy storage due to the haul.

Merlin