The perfect Passagemaker? II (building material)

Your perfect passagemaker...

 

By so far I see three of them.

All have one thing in common though, single engine and CPP.

The Drivetrain for the "Gentlemans Yacht" comes complete with the Grenaa engine.

For the others a similar arrangement of shaft, stuffing box, stern bearing, shaft tube in a self enclosed shaft assembly will be delivered by the CPP manufacturer. Here a thrust bearing has to be choosen separately.

 

I, as a novice, voted steel. To be able to survive some ice is very very convenient where I live.

 

Well, your decision. And it was meant to provide YOUR opinion and not the one everyone has!

Aluminium can be a valid alternative too.

even wood is a good and stable material in some ice conditions! Who would have thought that.
In fact a wooden Icebreaker can be a superior vessel in certain conditions. (the directly contacting zone would have to be metal reinforced though)

The more brittle stuff breaks. Ice is brittle (not always, it can stand loads of megatonnes per square kilometer when old enough), a wooden boat, loading the ice surface on a certain point is the more flexible part of the two, breaking the ice when the weight is applied.

But that is another thread....

Regards
Richard

 

Steel with a composite superstructure.

 

true, wooden ships can stand the ice here as well, but they require more maintenance, in my (limited) experience. Aluminium too, but I have no experience with aluminium. the corrosion issues require some knowledge and it's hard to weld from what I've heard. Maintaining steel is something I know a little of, is durable and relatively simple. Of course, these are my prejudices. this thread is very enlightening in these matters.

 

Corrosion of aluminium is next to zero, if you pay close attention to using dissimilar metals. When must, then ensure they are isolated correctly and you’ll have a trouble free boat. No need to pait either.

It is ‘easy’ to weld, just requires care. However, steel is very forgiving and poor quality is not so problematic. But, aluminium requires good strict procedures being adhered to, and hence not so forgiving, that’s all. A good quality steel welder will generally be a poor ally welder, because they are different methodologies and hence ‘culture’ of welding.

Every material has its “pro’s” and “con’s”. When designing with it, you just need to know what they are and then mitigate the risks according to your SOR.

 

Alright boys, now that you've gotten all that off your chest maybe we can get back to the thread. (EDIT; It looks like the fight fest got deleted, good, back to business.)

I have some questions, and I know this is just general, but for a boat like that described in this thread, that is, 23 to 25 meter LOA passage maker. can anyone give me an idea of the plate thicknesses of aluminum, steel, and laminate thickness of wood-epoxy-E or S glass?

And a related question, is there any kind of a ballpark figure how much the hul of each of these materials would weigh?

I have held off on voting because I don't feel that I have enough knowledge to make an educated judgment. I know Richard prefers steel, but if you were to be a little more restrictive, for instance, stay out of the icepack; would a composite wood structure be lighter weight, does it make sense? (not Balsa, a wood with comparable characteristics to African mahogany) a passage maker needs to be able to run into containers, logs and big chunks of ice.

SAN Foam, Core-Cell, Cross-linked PVC cores are out, at least below the waterline.

 

Why would Corecell be out below the water line?

 

I guess I have my doubts that foam core below the water line provide sufficient impact resistance, (for instance: repeatedly bashing into large objects, such as ice chunks. Not to be confused with slamming loads) moreover, I'm not convinced they provide sufficient abrasion resistance, especially if the outer skins are compromised.

Although there is this (article written in 2003):

Source: http://www.compositesworld.com/articles/getting-to-the-core-of-composite-laminates

There is an interesting report that I wouldn't mind reading; I have not bought the full six page report. It shows the newer Divinycell H and HP products outperforming HD:
http://208.109.124.94/store/paper.aspx?pid=4651

Another issue is cost, there's a lot of material going into the hull of a 25M boat; I don't think a foam composite hull can compete with a wood core or steel hull on price, although it would be interesting to know what the difference in cost would be.

If you know of any studies that have been done on any of these issues I have raised I would be interested in reading them.

 

You are right, foam cores are out of the game. They cannot stand impacts like hitting a container or banging on a reef. And although we all hope that will not happen, it does.
When the high latitudes are not included in your cruising, a wood epoxy hull can be a alternative to metal, of course. And I planned the Gentlemans Yacht to be possibly built in wood/ep. But no calculations are made by so far.

Yes a well designed and executed wood epoxy hull is lighter than steel and about equal with Al. But again, it is weaker on impacts, therefore not my preferred material for such a boat. We never know what a second owner has in mind, so lets stay with metal.

The North Sea Trawler is planned in 8mm below, 6mm above WL in steel. Although we have a weight estimation for the preliminary design, I do not have the hull weight separately at hand.

Less for the Gent´s Yacht, where we have just sketches of the profile and GA.

We are still in a very early state and the estimations are accordingly broad.

Due to the very clear result of the poll, it is not sensible to talk any FRP choices further, I do not build these boats in FRP, period.

Regards
Richard

Thanks Jeff, for cleaning up!

 

I was reading in an other thread* and have a question. As this thread is running and is about building building materials I ask it here . . . .

* Offer: true go anywhere Trawler to build "side by side" - post #39

What period of leaving it unattended are we speaking about, and what is the attention that an Al hull needs above a steel one ?

What is it that one should pay attention to, regarding to this, when buying a second hand Al boat ?

Thanks!
Angel

 

The first thing you do when approaching an aluminium boat...before examining any features, before falling in love with the design, before considering the price, is to take a volt meter and measure for DC voltage on the hull...check positive battery terminal to hull, negative battery terminal to hull. If you find electricity on the hull immediately call a good surveyor and examine the hull. Pay particular attention to the inside of tanks, heat exchangers, pumps plumbing, rudder bearings, shaft logs, mast steps, ....the list is long.. any area that is wet. A good surveyor will know and zero in. Aluminium is a great building material..the best..but it will not tolerate stray electricity and dissimilar metals in seawater. One of the added costs when building an aluminum boat is this careful attention to detail concerning the electrical system, equipment selection and instalation and dealing with dissimilar metals. A classic visual indicator of stray electicity is exterior paint bubbling. If the yacht is out of the water, carefully observer the anodes. Anodes should wear evenly from bow to stern. If you see good anodes forward and totaly erroded anode near the engine room...something is wrong. Pay paticular attention to Aluminium to stainless steel joints...these metals are not natural friends. The SS to alu joint, and an aluminium yacht will have thousands of ss fastenings , must be carefully executed. Professional aluminium boatbuilders know all the tricks. The problem with a older yachts is that a previuos owner may not have observed correct standards and did something stupid like replace an original spec steel to aluminium watertank fitting with a stainless steel to aluminium tank fitting. Big problem.

 

And what's more propable to happen.. A boat with leaking shore power installation (or what ever fail) moores next to you. This steel hull doesn't have any corrosion as long as there's any al left on yours.. And there's no way you can protect yourself except being vigilant 24/7..

 

Marco built some Bristol Bay gillnetters out of aluminum in the sixties. I know of one that was crushed by a steel crabber against some pilings to the point where the gunnels were touching. Come-a-longs were used to pull the hull back to shape and repairs done to the interior and bulkheads and another twenty years put on the boat after (still fishing!). All of those boats are still fishing in fact. On Kiska Island, and others, there are some WWll aluminum war planes that, after sixty-five years of whipping saltspray, look almost like they just came off the assembly line, but for they have bullet holes and are crashed. Steel objects, jeeps, artillary, submarines, Marston matting - one can grab a handful of steel like it were cake. My point isn't to say steel is bad - with modern coatings it is great, but don't be too afraid of aluminum. Treat it right and it will give you a lifetime of service in return.

In a constantly wet or frozen drainage 20m above MHHW above an exposed beach.

This one is under the bay or in the surf on rocks since 1944.

Steel doesn't even survive like that.