Steel boat – heaven or hell?

[svrodeorm]

Originally Posted by leftbrainstuff

With decades of experience in engineering ferrous, non ferrous and composite structures. No material is better. It's all about compromises and tradeoffs.

I favor glass fibre boats. Why?

1) grp is on balance more durable and less of a maintenance burden over time
2) steel has the benefit of much higher hardness and impact resistance. Provided the steel used has appropriate ductile to brittle transition properties. The Titanic and many WWII Liberty ships sank because they were operated in sea temperatures lower than the glass transition temperature of the steels used. Typically 5 -15 deg Celsius. What steel has been used in your desired vessel? Not so much of an issue these days with the microallyed steels in common use.
3) Corrosion is potentially a much bigger issue with metal boats. Coating preparation ideally requires full vessel grit blasting. Any scratches then pose issues. This is often more of a problem on the interior. Corrosion will often start in hard to inspect locations.
4) Condensation and heat soak can pose major comfort issues in some climates.
5) Sensor location on steel boats can add some complexity relative to grp boats.
5) High quality field repairs of non ferrous boats are near impossible. Steel is a little more forgiving to field repairs while grp can be fully repaired anywhere.
6) Shape and aesthetics. I see some ugly steel boats because the builder didnt have capability or ability to form complex steel shapes.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

Good thread, but this one sums it up IMHO, then it's down to personal preference as always

[GTom]

Originally Posted by svrodeorm

Good thread, but this one sums it up IMHO, then it's down to personal preference as always

I am actually surprised that the "single GRP" rules the boat world while there are a range of metals and there is carbon fiber too. I highly doubt that for 99% GRP is the best choice... Most buy it because there is no affordable solution for their design preferences.

[hpeer]

Lots of reasons to choose this or that. The cruising area and availability of repair facilities can influence your decision. Being able to take hard groundings vs round the cans race performance. Etc.

[GTom]

Originally Posted by hpeer

Lots of reasons to choose this or that. The cruising area and availability of repair facilities can influence your decision. Being able to take hard groundings vs round the cans race performance. Etc.

Absolutely. Being a novice I have been jumping between designs from trailer sailor, multihulls up to heavy cruisers. Cruising area comes first of course. Staying with the steel vs GRP topic however, robustness/relative immunity to grounding/collisions is always a plus.

[hpeer]

Yup, the hardest thing is to figure out what life has in store for you and how it will all unfold.

Relax, any decision you make will be the best one you can with the information available. Just try to not over commit, keep some thing reserve for when it all goes pear shaped. As it will.

Good luck.

[GTom]

Thanks! I always keep some reserves, never bet everything on one card. Playing it relatively cheap and safe is also part of the game.

[GTom]

This is quite reassuring:

https://www.boatdesign.net/threads/hot-zinc-spray.7021/

I would like to share some experience that I have with flame spray.
I have friend with a 36 foot steel sailboat that was built in Holland more than 80 years ago. On the inside the boat was flame sprayed with zinc at the time it was manufactured. Insulation in the form of rock wool was installed and over the years got wet. There is not a sign of rust, on the unpainted zinc, in any area that we inspected on the inside of the boat. I can't speak for what was applied on the outside of the boat because there looks to be 80 years worth of paint.
I have flame sprayed the inside of my 39 foot steel sailboat with zinc so I have at least a minimal amount of experience with sand blasting and zinc flame spray. I bought a type Y Metco gun and a box full of spare parts on ebay for 140 US$. The gun works perfectly. The pure zinc wire costs around 7US$ per kilo and covers around 5 square meters per kilo. It takes a minute or two to spray a square meter, on a straight run. Add in the cost of gas and oxygen and the cost would come in below 1 US$ per square foot. Compared to epoxy coating systems, primer ... primer. paint. I believe the zinc is the cheaper of the two, or at least in this neck of the woods zinc is cheaper? There are issues about welding over zinc etc. etc. but since this is already longer than most will want to read, I wont go into them.

Also:

https://www.youtube.com/watch?v=gdkl5LaKkhk

[Pauls]

It all comes down to the quality of the original construction. This is true for all materials. Steel, properly finished, which means sand blasted, then painted with high quality paint both inside and out, is very long lived and low maintenance. If the paint prep is poor then there are rust problems. There are plenty of examples of old steel boats in great shape, as well as examples of what happens when they aren't built right. Buy one that is built right and steel is a great cruising boat material. Metal boats are about the only way to have a really dry boat. With no holes in the deck to mount anything and welded seams they can be very dry. Welding rod is the best bedding compound in the world.

[Captsteve53]

Wow , Certainly so many varied beliefs out there with steel yachts here's some FACTUAL input coming from a steel yacht builder of some 40 years ,

1) Constructed correctly and use of pre-blasted and zinc primer sprayed quality steel covered with Epoxy primers and top coats will survive numerous years with out corrosion issues or even regular maintenance.
2) With the use of Corten steel (same as a container) the corrosion issues are negated by a huge percentage if following my number 1 item, Corten steel has additions of Chromium and Copper to battle corrosion.
3) As long as the normal practice of isolating installed materials such as Bronze thru hulls/sender units etc any thing can be mounted on a steel vessel above or below the water
4) There is no such thing technically as Electrolysis when referring to corrosion issues with steel vessels , here's the definition of ELECTROLYSIS)

A)chemical decomposition produced by passing an electric current through a liquid or solution containing ions.
B)
the removal of hair roots or small blemishes on the skin by the application of heat using an electric current.


5) Steel vessels suffer from GALVANIC CORROSION/STRAY ELECTRICAL CURRENT CORROSION/CREVICE CORROSION
6) Repair of steel hulls these days is rather easy when compared with other materials as steel workers abound at most area's of the world, and no you dont have to strip the whole interior to repair, the prudent use of cutting wheels will remove most of any area required to be repaired, once gone it's easy to check inside if some thing needs to be removes /isolated.
7) Nearly all new hull testing ultra sound equipment will read thru paint/filler etc even up to 1/2" and above fillers- and yes even under water!!, the days of removing paint to check thickness are long gone
8) Dont even have to make a mess any more if blasting is required inside or out with the use of Dry Ice blasting
9) As for the weight etc of steel yachts these days with Steel designers for yachts (not taken/adapted from wood designs as was common)the build weight is very close to other normal building medium(No not comparing to composites etc)
10) One thing i note not mentioned when referring against GRP is the improved comfort (roll moment of inertia)
11) I note some talk of using ALUMINIUM anodes(-.09) on their hulls- Only Zinc Anodes(-1.1) should used (probably why they have had to place so many on the hull?)
12) Un less checked with a 1/2 cell silver anode /multi meter it's possible to cause issues with to many zincs(Paint blistering.corrosion!!!)

Finally the strength factor- Steel pound for pound is the strongest material out there especially in toughness and survivability in extreme conditions,

Below are two pictures of STEEL YACHTS in very bad collisions with no water ingress (NOW-you tell me where any other material would with stand this and be floating!!)

Cheers Steve (Marine Engineer and Steel Vessel Builder)yes we did build in GRP as well (Rob Ladd/Larger 45 (Annapolis boat show awards) plus 60ft, So you see my mind is not totally one sided!!!

[Pete7]

Originally Posted by Captsteve53

10) One thing i note not mentioned when referring against GRP is the improved comfort (roll moment of inertia)

Great post, but could you just expand on this part?

Pete

[GTom]

I have to fly to my boat (probably many do...) thus a troubled mild steel construction is definitely not for me. Unfortunately corten seems to be rare among the boats on offer (or one has to travel around the globe to get one) - I suppose corten boats would be advertised as such, stronger (50%!) material that corrodes slower is a key selling point...

The best would be of course to order a brand new hull and treat it by the book, but I am afraid that's beyond my budget (haven't seen numbers though).

[GTom]

Originally Posted by GTom

I have to fly to my boat (probably many do...) thus a troubled mild steel construction is definitely not for me. Unfortunately corten seems to be rare among the boats on offer (or one has to travel around the globe to get one) - I suppose corten boats would be advertised as such, stronger (50%!) material that corrodes slower is a key selling point...

The best would be of course to order a brand new hull and treat it by the book, but I am afraid that's beyond my budget (haven't seen numbers though).

Browsing trough the ads, one can see what corrosion can do to a boat if conditions/care are not ideal... and how does a well maintained 60(!) years old steel boat looks like.

[hpeer]

The negative comments I've heard about zinc coating and zinc primers wells restricted to their use outside under the waterline. I think all agree with their use above the waterline and inside.

In fact our big boat was coated inside and our with flame sprayed aluminum. I see no negative issues.

[hpeer]

Gtom,

I've seen worse. Often the condition is not represented in the add and old pictures are shown.

On the other had, I am in Newfoundland and I know of an ice, well maintained 40'er for sale. Pilot house, inside steering. Asking $40,000 Canadian. Let me know if you are interested.

[Captsteve53]

Originally Posted by Pete7

Great post, but could you just expand on this part?

Pete

Pete, Been racking the old brain box for the simple answer but it's complex to say the least: here goes SO BEAR WITH ME:

1) While the amount of displacement per water plane area will have a very real effect on a vessel's reaction to the sea surface, it is the distribution of a vessel's mass that has the greatest effect on dynamic roll motions. A vessel's "Mass Moment of Inertia" also called "Roll Moment of Inertia" is a way of expressing resistance to being put into motion by a force.(Quoted Text book Explanation)

2) We can improve comfort, and we can improve safety by increasing the "Roll Moment of Inertia" of the vessel. This is accomplished by spreading out the various weights aboard rather than having them highly concentrated. This is very much counter to the often assumed requirement for a specific 'ballast ratio' on sail boats, or that there must be a certain amount of ballast present for the safety of a power boat.

3) For the most basic understanding of this, we can observe that an object with its mass distributed toward its perimeter will have a much higher resistance to changes in motion. It is therefore evident that it will be more dynamically stable. This can be intuitively thought of as the "gyroscope" effect.

4) On boats, it has been well proven that distributing weights away from the roll axis, say into the structure and the rig, is extremely favorable to a vessel's dynamic stability. By direct observation, we have learned that boats that have been dis-masted are much more likely to be rolled over.

Why, you might ask...? Don't they have a much lower CG as a result of the dismasting...?

5) A dis-masted sailboat is more likely to capsize due to the greatly reduced "Roll Moment of Inertia" and the consequent relative ease with which a heavy roll can be suddenly induced. This cannot be demonstrated by any kind of static analysis as one would normally expect. Said differently, while the dis-masted boat obviously has 'more' static stability without its mast, in the ocean where dynamic forces are at work, the effect is the opposite...!

6) More explicitly, Roll or Mass Moment of Inertia is a way of expressing resistance to being put into motion by a force. This is quite different from static Torque or "Righting Moment" which is calculated as a quantity of mass times its distance from an axis. Instead, Roll Moment of Inertia is calculated as a quantity of mass times the fourth power of its distance from an axis.

STILL HERE?

7)Many years ago during the Fastnet Race, rigorous analyses done after the loss of many vessels revealed that the boats which had concentrated ballast, light structure, and very light rigging suffered excessively due to their harsh rolling motions which caused many dismastings with consequent capsizes, as well as widespread seasickness and inability to function.

8) By comparison, boats with heavier structure, lesser "ballast ratios" and heavier rigs resisted being "thrown" into severe roll accelerations, had much more sea-kindly roll motions, were easier on their rigging, did not lose their masts, did not capsize, and did not experience nearly the degree of seasickness among their crews. This is counter-intuitive because the heavier vessels typically had a higher center of gravity and therefore less "static" stability. However due to their distributed masses they had much greater "dynamic" stability, which enhanced both sea-kindliness and sea-keeping ability, and vastly improved survivability.

OK TRUST YOU ARE STILL WITH ME?

9) With regard to structure, as compared to a fiberglass vessel a steel vessel will inherently have its mass distributed farther from its roll center, therefore a steel vessel will have a higher roll moment of inertia (mass moment of inertia) and will be less active 'dynamically' in terms of roll, pitch, and yaw, thus a steel vessel will inherently be much more sea-kindly.


Cheers Steve (MIIMS-Lloyd's Maritime)