Thread: Boats / Ships & Fishing

Originally Posted by Pedro_The_Swift

how about some action shots Ean?

you know the old saying,,
a picture sells a thousand prawns

Oh! My God! Spare us action shots of shipboard life. Rum, sodomy, and the lash, as was said about the Royal Navy.

Originally Posted by Brian Hjelm

Oh! My God! Spare us action shots of shipboard life. Rum, sodomy, and the lash, as was said about the Royal Navy.

Are you sure they are in the right order?


Cheers Ean

that is a classic - ha ha ha ha

Originally Posted by JDNSW

I seriously considered ferro, but ended up with steel. I think the problem with ferro is the amount of labour involved.


John

My son is a civil engineer who is a specialist in concrete and marine structures.

I asked him today about ferro-cement hulls. He says he would not, if he had a choice of anything else. He gives the example of static marine concrete structures where little corrosion and concrete cracking occurs under the tide line. Above the low tide line the porous concrete absorbs salt water and dries out when the tide falls leaving behind salt. Air (oxygen) then enters the capilliaries and corrodes any steel in the structure with the aid of the salt. Rust starts, expands, and starts to break out the concrete. He says concrete is porous having capiliaries and a network of microscopic cracks allowing moisture entry. He says a boat hull will do the same as it is likely to be operated heavy laden and thus soaking the upper level in salt water and then moored unladen thus allowing the water to dry out and corrosion to start same as the static structure. Just takes longer.

He says if one had to built a ferro-cement hull, then an expensive additive should be used. Caltite, which seals the porous passages and is a water repellent. Drawbacks are that it is expensive and the company insists its representatives be present whilst it is being used. If not used properly they withdraw any guarantees and support. He has been involved in a dispute between a property owner, principal contractor, sub-contractors, and Caltite. Caltite techno reps on the site say the concrete trucks were arriving too close together, overwhelming the placing and finishing crews, and finishing was going on after "first set" not to the required Caltite standard.

When we built our yacht we used Onodo products. Cant remember what they were now but one was a sort of parrafin wax emulsion. Made the plaster more plastic.

Didiman

is it hard to learn Alluminium Welding?

"is it hard to learn Alluminium (sp) Welding?"

Hard relative to what? What process do you want to learn. What processes are you already proficient in? What equipment do you have available?
Arguably the internet is not a very good classroom!

Simply put Al is a smite harder to fuse than carbon steel for reasons of puddle control. Al goes from metal - to fluid - to splashing on the ground in an inordinately short period of time! No puddle colour change as with carbon steel. But with practise it is just another skill?

S

Originally Posted by Brian Hjelm

My son is a civil engineer who is a specialist in concrete and marine structures.

I asked him today about ferro-cement hulls. He says he would not, if he had a choice of anything else. He gives the example of static marine concrete structures where little corrosion and concrete cracking occurs under the tide line. Above the low tide line the porous concrete absorbs salt water and dries out when the tide falls leaving behind salt. Air (oxygen) then enters the capilliaries and corrodes any steel in the structure with the aid of the salt. Rust starts, expands, and starts to break out the concrete. He says concrete is porous having capiliaries and a network of microscopic cracks allowing moisture entry. He says a boat hull will do the same as it is likely to be operated heavy laden and thus soaking the upper level in salt water and then moored unladen thus allowing the water to dry out and corrosion to start same as the static structure. Just takes longer.

He says if one had to built a ferro-cement hull, then an expensive additive should be used. Caltite, which seals the porous passages and is a water repellent. Drawbacks are that it is expensive and the company insists its representatives be present whilst it is being used. If not used properly they withdraw any guarantees and support. He has been involved in a dispute between a property owner, principal contractor, sub-contractors, and Caltite. Caltite techno reps on the site say the concrete trucks were arriving too close together, overwhelming the placing and finishing crews, and finishing was going on after "first set" not to the required Caltite standard.

Certainly concrete used in hulls usually has an additive to ensure low porosity, but this need not be a proprietary additive - successful concrete hulls were being built many years before these were invented - for example, 'Helsal' a successful ocean racer of the 1950-60 period, and barges dating from as far back as the eighteenth century. I think what his discussion is missing is that concrete hulls are always adequately painted, inside and out, which prevents water absorption from being a problem.

John