Steel Boat Building Techniques

[MarkC]

It seems that this construciton method alleviates the need to roll/form largeish plate steel to shape (for instance in the lower-stem-area) because the 'planks' or laps of steel are easier to attach?

the layout and cutting is 4 to 10 times longer (depending on the strake to chine ratio) than conventional forming

I guess that depends on how skilled a former and what equipment (English Wheels etc) you have?

Asthetically it looks great for me (from the Dutch pictures above).

You have that look - like a wooden boat. Some builders do that in fiberglass as well - but this seems more honest because one is still really 'planking'.

[jehardiman]

Originally Posted by MarkC

It seems that this construciton method alleviates the need to roll/form largeish plate steel to shape (for instance in the lower-stem-area) because the 'planks' or laps of steel are easier to attach?

Quote
the layout and cutting is 4 to 10 times longer (depending on the strake to chine ratio) than conventional forming

I guess that depends on how skilled a former and what equipment (English Wheels etc) you have?

Asthetically it looks great for me (from the Dutch pictures above).

The time to form it is not a skill or tool issue, it is a cutting issue. Every inch of cut plate edge represents time. 4 times the cut plate edge, 4 times the time reguardless of what tool (grinder, gas axe, or CNC plasma jet) is being used to cut it. Of course a $500,000 CNC plasma jet could cut it a lot faster (if they had the file) than 1 guy with a box of $5 grinding wheels, but those are other economies.

[FAST FRED]

Would this method of boatbuilding be more suitable for aluminum?

The internal void would no longer be a hassle and the overlaps might add stiffness , requyiring less framing weight ect?




FAST FRED

[rayk]

A couple of years ago I visited a Dutct built yacht, 38ft mod disp steel lapstrake built in 70's, and recall frames without stringers. Internal laps were not fully welded or sealed either. The issue of corrosion was immediately raised, but confidently dismissed by the owners, who explained how condensation travelled directly to the bilge. The owners pointed out the original hull paint and claimed no problems.
If it wasn't such a pain to build, I wouldn't mind having one.

[Milan]

At least one Dutch builder of extremely strong steel boats, Bronsveen, (http://www.bronsveen.nl ), uses laps. Their laps are a bit rounded and very tightly pressed at each other. They are using this method because of additional strength of the joint, (Each lap becomes a sort of stringer). They say that this method doesn't take them considerably more time, because with more common methods more stringers are needed and even if plates edges just touch each other, double welds are needed anyway.

French builder Meta, (http://www.reducostall.com ), built many Joshua, (Bernard Moitessier), type of the boats with the welded laps.

Milan

[MikeJohns]

Originally Posted by rayk

..................who explained how condensation travelled directly to the bilge. ....................

Rayk

Capillary action stops this moisture "draining" away and if it was salt water sloshing around from the bilges that would ingress too. Voids need to be fully sealed. I would also want to see two fillet welds ie inner and outer at that plate lap, just one on the outer is poor practice.

I just surveyed another riveted steel boat (Dutch 50 footer) but this was flush riveted with a doubler along each plate seam, the corrosion (since 1935) is bad enough to have to re-plate around 10 feet of 10 inch wide strip close to the waterline, it will be an easy enough repair when the tanks are out after the soles have been cut out............................

[MikeJohns]

Originally Posted by FAST FRED

Would this method of boatbuilding be more suitable for aluminum?

The internal void would no longer be a hassle and the overlaps might add stiffness , requyiring less framing weight ect?

FAST FRED

Thats a thought. But alloy has some detrimental qualities. My immediate concern would be that you then have stress concentrations at the edges of the overlap which are also weakened weld zones (poor property of Alloy welds) and given a poor fatigue response in the weld zones the plating would need to be stiffer (thicker) so you might end up with no net advantage to a simple butt weld.

Alloy is light and easy to work which makes shaping it to a precision fit a lot easier anyway. The big advantage with overlaps is that it allows very fast plating.

cheers