Study on Reducing Towing Drag by Varying the Shape and Arrangement of Floats and Gears

Round 1

Reviewer 1 Report

Dear author(s);

Please kindly check the attached file.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

- "kgf" is an absolutely unacceptable unit of force; the only unit allowed for force (and weight is also a force) is newton, symbol N; "kg" is a unit of mass; in the manuscript it should be clearly distinguished where the term "weight" is used, and the term "mass"; weight is a force and the unit is newton (N) while the unit for mass is kilogram "kg"; using the unit "kg" for "weight" is not allowed at all ; the term "buoyancy" as well as "sinking force" are also forces so the only allowed unit is "N";it is necessary to correct this  throughout the whole manuscript (line 94, Table 1, Figure 10, line 339, line 336, Figures 12 & 13);

 - Figure 11 is not clear. Is it a plan or side view? Or both?

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

The paper is prepared on very high level. It is recommended for publication without any changes 

Author Response

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Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

- It is not acceptable to refer to references in such a way that the title of the paper is stated in the text itself; all references should be listed in "References" and then referenced in the usual way - with number of the reference in square brackets.

- "kgf" is an absolutely unacceptable unit of force, the only unit allowed for force (and weight is also a force) is newton, symbol N; "kg" is a unit of mass.

- Figure 3. is not clear, it has to be completed.

- Table 1: missing length for G10.

- Section 2.2 .: the experiment with the car towing ground gears on a dirty ground is not clear. What is it for? Is there any similarity to pulling gears on a dirty ground and scraping a net on the seabed? This has to be more elaborated...

- Figure 3 is not clear. It would certainly help to show how the towing experiment was truly performed.

- Lines 158-167: this part discusses the use of photographs to estimate the projected area. It would certainly be desirable to show at least one photo with the accompanying data.

- The second part of the paper starts with "4. Discussion" and it seems a bit surprising that there is a text here that would much have belonged to "1. Introduction". One gets the impression that these are two separate papers which were then merged into one, but the text is not balanced at all.

- Lines 291-293: Indeed, it is known from the literature that a golf ball has less resistance than a sphere with a smoothed surface. However, are the conditions under which this is achieved the same for sphere -shaped floats?

- Line296-297: The text "This will be explored further in future studies" is not acceptable at this place in the paper.

- Lines 314-316: It is not entirely clear why this is stated here... 

- Figure 11 is not clear. Is it a plan or side view? The figure would certainly more belong to the first part of the paper...

- Figure 12. Is also not clear. Is it a plan or side view?

- Figure 13 and 14.: It is not clear in which units the weight is shown. If it is in kg, then it is wrong because the only correct unit is newton (symbol N).

- Lines 395-397 and 405-407: It has already been stated that it is not acceptable to refer to references in such a way that the title of the paper is stated in the text itself;

- Lines 407-410: The first sentence states that it has been achieved a percentage reduction in drag and fuel consumption of 60%, and then the second sentence states that according to the results of this work, a reduction of approximately 0.8% is expected. Why so much difference? Is 0.8% measurable at all?

- It is not clear where the results shown in Table 5 came from. How are drag reduction and fuel consumption related?

- "Further reading": this way is not common. If these are references that were used in the preparation of the paper, then they should be included in the list of references, and if not, then they should not be listed at all.

 

In conclusion, the following can be said: the paper has serious shortcomings in terms of writing the text and presenting the results. One gets the impression that at least two similar papers have been merged into one, without any balancing. The paper requires careful and extensive rearrangement and only then can it be considered for possible acceptance for publication in a journal.

Reviewer 2 Report

Many thanks to the authors for submitting this manuscript. It is hoped the feedback below will help enhance the quality of the manuscript.

There is a good introduction outlining the motivation for the work

Line 56: the E- Fishing 2010 reference, listed as further reading, should be made a numbered reference as it is explicitly referred to in the text. Same applies for other similar cases (eg line 300)

Could a figure be provided for the expected drag due to fishing gear out of the total drag of a trawler?

It would be valuable to provide justification for the methodology employed, eg: speeds used, sampling rate and time, etc. Flow characterization in the flume would also be valuable

A vital area to address prior to publication would be the uncertainty analysis. There are small variations in results, which may or may not be significant. The author would therefore kindly be asked to provide such uncertainty analysis. This may be based on the uncertain U being U^2 = B^2 + P^2, where B is the total bias (which can be based on the root some of the individual biases relevant to the data reduction equation for CD) and P would be the precision, assessed at the 95% confidence level.

Equation 1 (and other references) as a fluid dynamics paper, U would be expected instead of V for the flow speed.

Line 179: further detail on how the friction coefficient was computed from the towing experiment would be desirable

Results: the quality of the graph should be improved by using thinner lines to make the data more visible. Different markers should also be employed for each individual float so the results are more obvious to readers

Fig 12/13/14 a more harmonious text size to better match that of the text would be recommended

Table 3 presents misleading results: redesigned drag values are provided for ground ropes that were not redesigned. indeed, the paper stated only 5G was redesigned, presenting the other ground ropes in Table 3 is therefore misleading, and should be removed.

In Table 4, drag should be expressed in newtons for consistency. The text also need not be bold (same applies to Table 5)

The conclusion should aim to further highlight the novel contribution of the work to the field.

Reviewer 3 Report

Not very interesting. several other papers dealing with the same subject already published, some very old.

Results poorly convincing.