Tanker proa

Technique isn't about opinions, but it's all about facts.

In real model testing you calculate the equivalent to full size wind speed and wave heights, and don't leave it up to the opinion of an expert viewer, who could just be carried away with enthusiasm for the project, which would give a biased opinion, and for sure just eyesight of a model in a test is far from seeking technical facts.

Besides that, the expert viewer should know that 100 mph winds is less than what tankers every now and then encounter in the real world, and what they and their add-ons should be designed for.

A supertanker is a complex and highly engineered structure, to which you can't add major add-ons without technical consequences for the close within the safety limits designed original structure, it should at least be engineered as a whole to get it structural right.

Now being this far in the project, did you get any fiat of a supertanker designer for this add-on yet . . ?

Below some videos of not unusual winds and waves tankers encounter on their routes, the fully loaded one (#2) seems to be the least affected by the wave impacts, so I'm not sure it's a wise advice to go empty and take no ballast water when there's no cargo, and then just assume¹ the ama should take care of stability...

¹ this this should be based on sound stability and strength calculations, and not on some expert's² opinion.

² there isn't a single full size tanker proa yet, this means there are no full size experiential experts in this field, so to claim or suggest one would be false, so this strengthens I would rather trust sound stability and strength calculations³ for the full size issue.

³ which if they exist could be issued⁴ to substantiate the strength and stability claims.

⁴ as well as calculations for the adequacy of the sail power for the claimed tanker proa sailing speeds please.

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That argument is ripped out of its historical context (and size when comparing to the wished proa tankers), so to put the argument at least into a contemporary perspective here some questions:

1. Would you estimate the loss rate of the Polynesian proas and people while they populated the islands in the Pacific ?
2. Would that loss rate be acceptable today ?
3. More specific for tankers ?
4. How many Polynesian proas, of the historical kind you referred to, are nowadays in use for that kind of trips ?
5. Why is this ?​

 

1. Clearly the loss rate was such that they continued to use the design well in to the 19th century.
2. That data is not readily available – however the worlds thirst for fossil fuels would need to determine today's rate.
3. Our testing on the prototype indicates it would increase the tankers save travel.
4. Counting Hobie Cats and Multi-Hulls – Thousands.
5. Because they are more stable in all conditions.

 

After you claimed in post #73 the alleged success of historical Polynesian Proas to be valid for proa tankers, I've asked for your estimation of the Polynesians' loss rate while they populated the islands in the Pacific. But since you avoided that, and came with this evasive answer, here a follow up question about your above diversion...

Do you think when the ancient Polynesians travelled to the unknown there was feedback to the homefront whether they had arrived or not at an unknown place, so the loss rate was actually known there to take this information into account for the next departures ?

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Well, I'll tell you, for tankers loss is considered to be not acceptable today, however they do work with calculated risks, of which I don't know the rate, since it's not my project, but you should know, since this is your project.

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Well, since technique is all about facts, please post the data to substantiate this claim, otherwise it would be just an empty cry.

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You seem to be a poor reader, or one that just likes to give evasive answers.

The clear 4th question was not about diverted types, but about ‘‘the historical kind you referred to’’ for the alleged historical Polynesian Proa success that you in post #73 claimed to be valid for proa tankers.

Also there aren't many Hobie Cats traveling all over the the Pacific between all the islands there, like you claim here in your answer to the 4th question.

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Again, since technique is all about facts, please post the data to substantiate this claim, otherwise this also would be just an empty cry.

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BTW, just for your convenience, my main response to your post #73 can be seen in post #76.

 

Well Frank, it's been quite quiet so far around post #76, so I'll repeat the main question of that post, which should be easy to answer....

However responses on the other raised issues in the mentioned post #76 would be of course appreciated as well.

 

No it doesn't. For example, the Wright Brothers were treated with enormous respect by famous engineers (ie Chanute) and inventors (Bell) even before they had put an engine on an aircraft. The early computers were taken seriously by the military. The chronometer was a game changing technology that was (AFAIK) never a "crazy idea" and was actually essentially sponsored by the Royal Navy. The drasine and bicycle were darlings of high society from very early on. The assymetric spinnaker was adopted very quickly when practical.

Claiming that all new tech starts out as a crazy idea seems to often be an attempt to deflect reasoned criticism of new ideas.

 

How does the design handle the 25 foot-30ft change in draft between vessel loaded and unloaded?
Existing designs demand that matching ballast be added as cargo is discharged to prevent the hull from fatally deforming.

 

1. Totally agree, we are pursuing Naval Architects to help us produce full scale plans. The experts opinion has only served as wind in our sails, now the real calculations need to be completed.

2. Agreed - when the first full scale test rig is complete we're sure there will be plenty of experts available.

3. Agreed - these will have to be designed, built and tested

4. Not sure what your question/statement is here. The testing we've successfully completed was on a scale model, it performed very well in regards to speed and stability.

 

Angélique - just want to say how much we appreciate your questions on TankerProa and your deep understanding of the shipping market and the challenges it presents. Please keep them coming!

 

A lot of the TankerProa's issues is about technique that's known since ancient times, here's a rope truss construction running lengthwise over a ± 1,250 B.C. papyrus boat to prevent she breaks when she's lifted in the middle on top of a wave, in which event her front or rear end are hanging in the air unsupported by flotation, then the rope truss construction supports the keel and prevents breaking. A similar truss device was later used in Greek triremes.

↑ 1,024 × 533 pixels → 1,630 × 848 pixels​

Same thing with parts hanging unsupported in the air would happen to an unloaded tanker at sea, she simply would break from her own empty weight while riding the waves and so having her hull fore or aft end hanging unsupported in the air every now and then, alternated with both ends floating while at midships she's unsupported. Long ships simply aren't built strong enough to withstand those bending moments. That's one of the reasons they keep them loaded with either cargo or ballast water, which means all of the hull is deep in the water at all times, and so everywhere supported by floatation when traveling in rough seas, the outrigger won't help here.

Maybe I'll post later some relevant sailing info from the middle ages, in a for this project contemporary perspective.

Good luck !

 

About the text in the illustration in the previous post...

‘‘ Egyptian ship on the Red Sea, about 1,250 B.C. [From Torr's "Ancient Ships."]​

Mr. Lanton Cole calls attention to the rope truss in this illustration, stiffening the beam of the ship. ’’​

My thought here is; instead of ‘‘stiffening the beam of the ship’’, the text should say ‘‘stiffening the length of the ship’’, as I think that's what's happening.

P.S.​

I was reading ‘‘beam’’ as ‘‘width’’ there, but more likely by ‘‘beam’’ was meant ‘‘keel beam’’, in that case the text in the illustration is of course correct.

 

Every qualified tanker captain knows you can't go to sea with an empty tanker, while most of them, and certainly the expert captains, also know that structural issues is one of the reasons for this.

 

The ancient petroglyphs and reliefs after which the post #85 illustration was made can be found in and around the Mortuary Temple of Hatshepsut, so I've tried to look up some pics a bit closer to the originals and that also show some explanatory hieroglyphs around the ships...

| hatshepsut petroglyph ship | hatshepsut petroglyph boat | hatshepsut relief ship | hatshepsut relief boat |​

The below link also shows a replica, of which I took the picture from pinterest because it's larger and less retouched.​

Egypt's ancient Ship builders and Pharaoh(ess) Hatshepsut​

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↑ this one looks to me more like a collage remake ↑​

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I seem to remember that the longitudinal truss was originally created for the riverine boats that carried the building blocks (several tons in weight) from the upstream quarries to Giza and other centers.
The boats had very weak gunwales and limited freeboard
The idea was that the boats provided extreme buoyancy midships for load carrying and after the blocks were removed, the truss was tightened to prevent the the boat from self destructing by hogging.

 

Hogging and sagging, that's also what long and empty or wrongly loaded ships breaks on top of the waves.​

There's some drawings to explain it though . . ​

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ship hogging sagging​

Why Do Ship’s Hull Fail At Midship Region ?​

Tanker
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Can Wrongly Loaded Container Ships Really Snap in Two ?​

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The last one has two threads on these forums: 5 year old container ship breaks in half | Report issued on MOL Comfort Loss​

↓ Breaking ↓ - (just from the picture I'll guess more empty containers in the middle)
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The watertight bulkheads keep her halves afloat for a long time.​

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