Steel Hull?

[builder dan]

I once sailed over a whale at night in a steel boat we could tell it was a whale by the shape of the phosperescence when it swam away.no damage to the boat.With no whaling going on there is a lot more whales around than 30 years ago.I still consider ships a lot bigger danger than whales.

[barnakiel]

The risk is there. I would guess there is higher than 1% chance of hitting something and damaging the boat beyond repair. Whales seem of least concern: they are soft and neatly rounded.

Going slower mitigates the risk somewhat. Going in a stronger hull mitigates the risk somewhat further. If you chose a very strong hull ... you are likely to sail somewhat slower ... etc. If you are going fast in a paperweight hull, you may get more damage sooner.

b.

[Sea Frog]

I wonder why the heck nobody is using so-called "whale pingers"? They are widely used by commercial fisherment and are, from what I have read, proven to be effective way to scare whales away. There may be a difference in efficiency of different pingers, but some are said to be quite effective. And they are not too expensive either, AFAIK. So, instead of building a bullet-proof hull and trying to see the whale with a forward loking sonar (which won't be effective, I am afraid), isn't it better just to make them go away?

[micah719]

And I just posted on the Whale collision thread. Sigh. 135dB is loud. Otoh, less of a headache than a sailboat to the head. Interesting, might get one when the time comes.

Future Oceans 3 kHz Whale Pinger - Future Oceans

[barnakiel]

After all, they are at home and we are just visitors. Pinging the host could be a bit too rough, I think. Some scientists believe massive beachings may be result of extensive (mostly military and oil search) pinging.

Maybe there are some 'no go' zones? Maybe, just like we avoid ice, heavy commercial traffic, etc, we should start paying attention to where the whales live and how they travel?

Anyways, this must be a highly accidental event: having sailed many ocean miles in a pretty vulnerable boat we have never had a brush. And if you look at what Webb is doing (his boat is a 23' uldb), or at what hundreds of Minis are doing, this must be a most marginal chance.

b.

[goat]

Originally Posted by barnakiel

After all, they are at home and we are just visitors. Pinging the host could be a bit too rough, I think. Some scientists believe massive beachings may be result of extensive (mostly military and oil search) pinging.

Maybe there are some 'no go' zones? Maybe, just like we avoid ice, heavy commercial traffic, etc, we should start paying attention to where the whales live and how they travel?

Anyways, this must be a highly accidental event: having sailed many ocean miles in a pretty vulnerable boat we have never had a brush. And if you look at what Webb is doing (his boat is a 23' uldb), or at what hundreds of Minis are doing, this must be a most marginal chance.

b.

Here you go;



goat

[Steadman Uhlich]

I like steel boats. I really do.

But, while they can be strong and watertight, it is prudent to look below the surface and especially inside in hidden areas for hidden corrosion.

Anyone considering purchase of one?
If so, I suggest you read the following blog post about the possible hidden things that can be missed, even by a surveyor. The interesting part is about half way down the page.

Fundamentals of Terra D'Agua part 4 — Terradagua

[micah719]

Thanks for the horror story. Lessons learned.....invest in ultrasonic test gear before buying/maintaining steel boat, trust but verify, ferret out the scuttlebutt about prospective boats & previous owners; and have a close friend called Fat Tony with a side business in cement and oil drums.

Related to this, how about insulation. One should have access to all parts of the hull, yet steel needs insulation to beat condensation and not bake/freeze the crew.

I'm leery of sprayed closed cell foam because you don't know what's under it without ripping it off; I'm leaning toward sheets of rockwool encased in vapour barrier membrane (tyvek, like in house walls), attached to 3mm expoxied ply with a laminated timber rim to shape it. The interior of the hull is to be reinforced with rings (basically frames, which the TT doesn't strictly need) of laminated timber/epoxy, and to give the insulation panels something to slot into. That way I can pop out a whole insulation panel and see the plating, even weld, without the mess & hassle of stuck on foam. If I'm careful with the layout of the joinery I can cover the whole inside of the boat apart from the bilge sump and still have access any time for those regular inspections. It also adds significant bouyancy....

[Tensen]

Originally Posted by micah719

Hence the hull that can take a few hits. Go steel...

This is the collective myth that many uninformed people mistakenly believe.

Originally Posted by RaymondR

Excellent boat building material that it is fibreglass has a serious vulnerability in it's flamability, once it starts burning there is little chance of putting it out with the equipment available on most boats.

Perhaps true, but you aren't likely to put out any fire once it reaches that same point, and the course of action is then the same for any hull: get off.

The ductility of metals is their strongest property in resisting holing, no other boat building material surpasses them in this quality.

This is misleading. A material with no ductility can be harder to hole than a very ductile material.

It's a trivial matter to build in FRP to a point that absorbs far more energy that steel, despite steel's ductility.
(As an example of FRP's ability to absorb energy, it's used under helicopter seats to absorb crash impacts).
In other words, it's easy to build an FRP hull that's harder to hole by impact than a steel hull, and it will still be lighter to boot.

[barnakiel]

Originally Posted by goat

Here you go;



goat

+1!

barnakiel

[micah719]

A36 steel in plates, bars, and shapes with a thickness of less than 8 in (203 mm) has a minimum yield strength of 36,000 psi (250 MPa) and ultimate tensile strength of 58,000–80,000 psi (400–550 MPa).

This is the Cythera, 22 imperial tons, 43 feet, homebuilt steel ketch being rammed by the Colorado del Mar, 1025 imperial tons. The yacht was returned to her owners, who made emergency repairs to the smashed windows and then sailed it home through a cyclone.



This was the damage:



And another look:



And another, back in Sydney, 1963:



Try that in any other material, and then sail it through a cyclone, and have it still floating in 40 years, after more cyclones and collisions. Myths, huh? Look at the failure modes of fibreglass, and consider the repairs.

p.s. all info above from wiki, sorry

Now, here's a thread from Boat Design about fatigue:
http://www.boatdesign.net/forums/boa...gue-13174.html

And another about fibreglass, longevity, and water:
http://www.boatdesign.net/forums/mat...ass-11455.html

[Steadman Uhlich]

Originally Posted by Steady Hand

I like steel boats. I really do.

But, while they can be strong and watertight, it is prudent to look below the surface and especially inside in hidden areas for hidden corrosion.

Anyone considering purchase of one?
If so, I suggest you read the following blog post about the possible hidden things that can be missed, even by a surveyor. The interesting part is about half way down the page.

Fundamentals of Terra D'Agua part 4 — Terradagua

When you go to this linked blog and read it, carefully examine the photos in the blog.

Notice the holes that were punched through the steel plate with a screwdriver.

See the photo that shows a young woman sitting on the ladder (inside the empty hull). Notice the dark rust all around her on the steel hull. Look at the crevices, look at the panels, Notice the extent of what could NOT be seen because of the furniture (interior wood and cabinetry) that prevented seeing it.

Of course we don't know much about the boat. We don't know if it was a homebuilt boat or pro-built boat. We don't know when it was built. We don't know what kind of coatings were used on the steel. Those things matter too.

[Steadman Uhlich]

Originally Posted by micah719

Thanks for the horror story. Lessons learned.....invest in ultrasonic test gear before buying/maintaining steel boat, trust but verify, ferret out the scuttlebutt about prospective boats & previous owners; and have a close friend called Fat Tony with a side business in cement and oil drums.

Related to this, how about insulation. One should have access to all parts of the hull, yet steel needs insulation to beat condensation and not bake/freeze the crew.

I'm leery of sprayed closed cell foam because you don't know what's under it without ripping it off; I'm leaning toward sheets of rockwool encased in vapour barrier membrane (tyvek, like in house walls), attached to 3mm expoxied ply with a laminated timber rim to shape it. The interior of the hull is to be reinforced with rings (basically frames, which the TT doesn't strictly need) of laminated timber/epoxy, and to give the insulation panels something to slot into. That way I can pop out a whole insulation panel and see the plating, even weld, without the mess & hassle of stuck on foam. If I'm careful with the layout of the joinery I can cover the whole inside of the boat apart from the bilge sump and still have access any time for those regular inspections. It also adds significant bouyancy....

Hi Michah.

I appreciate your points and your concerns.

I went back and looked at the original post of this thread and see that the original intent was to discuss whether whales are a risk and whether a steel hull would make a difference (be safer).

Since your points are about the proper insulation of a steel hull, I suggest you start a new thread on that topic alone. That way the forum may take notice of it as a separate subject and the discussion can be focused on that topic. Otherwise, people tend to read the Original Post and if it is NOT on something which they have opinion or experience, they move on without seeing the other "off topic" content of the thread. . So, I suggest we spin off a new thread to discuss the pros and cons of insulation and removable interior construction ideas etc.

[Pelagic]

I favor a well built and maintained steel yacht for the following reasons.

Sailing in the Western Pacific with almost no SAR support, poor charting, high likelihood of anchoring in Typhoon Shelters with real risks of dragging ashore, whales are the least of my concerns.

I would place floating debris and containers as a higher risk in SE Asia and the need to survive the pounding and abrasion of a reef encounter without help, as the highest priority.

I know of many steel boats that pounded and deformed on reefs for days in adverse weather before dragging themselves off.....bent but not broken.

In my part of the world.. the advantages of steel are obvious.

[Tensen]

Originally Posted by micah719

A36 steel in plates, bars, and shapes with a thickness of less than 8 in (203 mm) has a minimum yield strength of 36,000 psi (250 MPa) and ultimate tensile strength of 58,000–80,000 psi (400–550 MPa).

And the same mass of FRP would have an even higher UTS - some would be an order of magnitude higher!

Try that in any other material, and then sail it through a cyclone, and have it still floating in 40 years, after more cyclones and collisions. Myths, huh? Look at the failure modes of fibreglass, and consider the repairs.

The myth is that steel is stronger than FRP. When compared pound for pound, FRPs are far stronger.