Frigate Helge Ingstad Design - Damage Survivability

The HI had a valid Seaworthiness Certificate and had been receiving a Class notation by DNV-GL:

PS> Not built to class but found to comply with requirements after delivery from the yard in 2009.

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There are no such things as a Seaworthiness Certificate or classification rules for war ships. Merchant ships must provide at PSCs plenty certificates about safety, protection, pollution prevention, radio, load line, ISM, security, etc, but no seaworthiness certificate. Reason is that seaworthiness is the responsibility of the ship owner alone to ensure that the ship is seaworthy. It includes the duty of the ship owner to provide a capable crew to operate the ship, which doesn’t seem to be the case here. I am still mystified about the structural damages of HI. We have been told that the starboard anchor of Sola TS ripped open the aft starboard deck house above waterline, but ships do not float on deck houses. Divers must have inspected and taken pictures of the wreck’s underwater hull and the damages there. Anyway, the war ship is a CTL and cannot be repaired. Easiest is just to leave the wreck where it is. I agree with you that the Swedish Royal Navy is a joke today with some corvettes, a submarine and some ‘war” boats for military action. It wasn’t much better 1965/70 when I served.
I note that the Norwegian Armed Forces Materiel Safety Authority issues something called a Seaworthiness Certificate but I haven’t got a clue what that piece of paper is all about.

HI and her sisters were built with a “ramming bow”:

Seems a bit funny in these modern times to build a ship with such a bow. You must be pretty desperate to ram another ship as it could damage your own ship pretty much in the process. I suppose you have to take additional measures in other parts of the ship to compensate for probable damage caused by the impact. In hindsight it was pure luck then that the HI had not crashed into the side of the tanker because then there had been a real problem with a huge oil spill, a possible fire and whatnot.

Beware we also still have a ship with a ramming bow built in 1868 for the Royal Dutch Navy. It was the Navy’s first ship driven by steam. It is now a museum ship and fully restored under the Dutch Heritage Goods act.

By the way, as I understand it the HI had 16 water tight sections but that didnot help much…

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Blockquote There are no such things as a Seaworthiness Certificate or classification rules for war ships.

In 2 minutes of googling, I found the LR Rules and Regulations for the Classification of Naval Ships and the ABS Guide for Building and Classing International Naval Ships. Maybe a little research on your end should be done before making broad and incorrect statements.

Yes - the LR Naval Ships rules are easily available at\Rules\NAVAL%20SHIPS\2015%20NAVAL\VOLUME%201\15%20Naval_v1%20p3.pdf

and they are more or less copy/paste of the rules for construction of steel Merchant Ships.

Of course a Naval Ship has a gas tight deck house while merchant ships deck houses must only resist rain and wind.

But LR does not concern itself with subdivision, damage stability, survival, pollution prevention/protection, lifesaving, crewing, operational systems (ISM) etc, including seaworthiness.

Or “ramming” of enemy ships! In the old days, we are told that Greek ships could ram enemy ships. The bow of the Greek ship was supposed to contact the enemy ship and sink it. The underwater part of the bow was reinforced with a bulb that could punch a hole in the enemy ship, etc. The above waterline part of the bow with the focsle and windlass/anchors is pretty useless to sink enemy ships.

In this Sola TS/HI case it seems it was the Sola TS (with a Greek Captain?) that rammed the Norwegian warship HI using its bulbous bow below waterline, even if we haven’t seen any photos of the underwater damages of HI. It caused up-flooding and loss of buoyancy of HI. Sola TS’ bow flare/focsle with anchors also ripped open the HI gas tight deck house above waterline but it didn’t sink the ship. It was only cosmetic damages! Ships do not float on deck houses.

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I am not going to discuss the merits or pitfalls of Class Rules for Naval Ships. You clearly stated they didn’t exist, yet a quick search proved you wrong.

I see what you mean. I clearly stated that there were no such things as a Seaworthiness Certificate or classification rules for war ships (to obtain a seaworthiness certificate). I was a little unclear. Of course there are classification rules how to build steel war ships that are not seaworthy. In the old days war ships/destroyers were built very light using first principles, so they looked like starving horses after a while (due to plastic deformation of the shell plates) and it was OK. Class doesn’t allow plastic deformation of hull parts.
Re HI life saving equipment it seems that the HI 130 sailors, to survive a sinking, had to jump into the water and swim to and climb into three life rafts that somebody would throw into the sea. These three rafts would then be towed to safety by a little rescue boat with outboard engine. Personally I prefer cruising in the Caribbean with good food and pretty women around than to spend time at a desk watching a PC screen on a grey funnel liner protecting Svalbard or Spitzbergen.

It makes sense that the navy will not depend on a civil classification society for seaworthiness of their vessels, but that they would take guidance from their rules.

I bet they get paid a lot better than those poor Royal Navy sailors protecting United Kingdom or Great Britain…

I’m guessing something is being lost in translation… ships haven’t been built with rams in over a century. The Nansens have bow-mounted sonars, which generally react poorly to running into things. More likely the bows are reinforced for Arctic operations and can “ram” growlers and such (which again, I don’t know that I’d want to expose my transducer to).

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A real ramming bow punches a big hole just above and below the water line so that large amounts of sea water can enter the enemy ship. Aiming for the engine room was what I would do.The bow of the HI is not a ramming bow, it punches a hole mainly above the water line.

Reinforcements for dealing with ice is the logical thing. The echosounder and sonar transducers are placed in the bow because it is the only place on the ship where there is ‘solid’ water. Fast ships and especially ships with a bulbous bow suck air under the keel which spreads out as a blanket of small air bubbles under the entire length of the ship. It is called aeration and sound signals are dispersed by that phenomenon and in fact blocked by it. In the pre bulbous bow time the transducers were fitted at a third of the length of the ship and that always worked well.

Here in the Netherlands we did tests already a long time ago in a Depressurised Wave Basin where the air pressure is reduced to the inverse of model scale so you need quite a bit of vacuum! It can be lowered to a minimum of 2500 Pa. The water is then on scale and aeration shows up. Also research on cavitation is possible as well as many other things. The new tank (2012) dimensions are 240 x 18 x 8 m and models up to 12 meters can be towed.

Nice ads …

The expression rubbing oneself against the horns of the behemoth takes on its full meaning. I don’t know who is the mastermind behind the design of a bulbous bow so wide, that he had to imagine some kind of can opener appendage extending beyond the hull outline. It is quite hard to picture the frigate heeling to the point of being ripped off from 3 to 4 meters above water line through all the way down below her line of flotation, without leaving any mark on the bulbous bow!

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Form follows function. If the wide bulbous bow saves a few percent of fuel in transit, why not? Few exceptions aside, ships are not designed with collision safety in mind.

What puzzles me is that even after two high-profile naval/merchant ship collisions, the Norwegian Navy refuses to use AIS within the confined waters of their own fjords.

Does-it saves a few percent of fuel in transit or it saves in bending and shaping steel construction cost or it increases the carrying capacity by a few cubes ? These horns appendages also found on bulk carriers could be very snagging if you have the misfortune to come alongside a strait dock with a certain angle or needing to keep an angle to clear the ice…


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In today’s highly-competitive shipping industry, I would expect any hull form to be a result of extensive CFD calculations, so regardless of what is the reason behind Sola TS’s bulbous bow, I’m quite sure it’s justified from naval architecture point of view. However, quite many modern bulk carriers are doing away with bulbous bows protruding much beyond the forward perpendicular. Protruding anchors, however, are still quite common - how else could you drop them clear of the hull?

ombugge, stabilizer fins are not uncommon in modern naval ships. However, I don’t think it really matters in this case whether they were extended or not.

«In today’s highly-competitive shipping industry» … construction cost is paramount. Bridge toilet that flushes is too expensive …


That is a bow worth of that name. Unfortunately, that flaring is by today’s standards, too expensive to build.

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That’s true. However, unless the vessel design is done in close co-operation with the shipyard that has some strange limitations (“Hey, we can’t bend double-curvature plates!”), it’s unlikely that any “construction cost saving features” will show in the price tag. In China, work costs next to nothing, so making the ship “cheap to build” by leaving out one branch from the sewage vacuum line doesn’t necessarily pay off.

I’ve sometimes dreamed of creating a “crude” and “simplified” design aimed to reduce construction cost and time, but while most yards can’t really put a price tag on, say, replacing most of the double-curvature shell plating with single-curvature plating, it’s quite easy to calculate the impact to installed power, endurance etc. So now I’m dreaming of creating a tanker where the double hull is just an offset surface from the shell (to maximize tank capacity)…

I guess we are straying off topic again.

…like that !

Then it will be understood that walking out a VLCC anchor gives better control…

Back to topic … :wink:

Now the shipyard getting involved: