can it be done in steel?

But to pretend it's a new method and connect another 'inventors' name to it is just fraud. Even to put his own name to it would be fraud because it's nothing new.
Marketing hype by any other name is marketing hype.

Forming conical sections on a press brake or by roller has been done for around 100 years now in small boat building.But the more advanced method shapes the panel in two dimensions by various methods. The difference is that Dennis presumably provides the crease lines and bend angles for the press brake operator. but any cad jocky can do that for any conic section.

But why bother when rollers can roll plate so easily to a constant radius whether you do it yourself or pay to get it rolled it's going to be better all round.
If you were building a true round bilge then you'd need to form more complex curves in the plate in both direction and would need a wheel. But that becomes a labor of love.

 

Ideally the "constant radius" portions of the hull follows the edges of the topsides and bottom. The hulls I'm aware of have the constant radius portion formed using a number of short, constant radius plates which are straight in the longitudinal direction. The length of the constant radius sections depends on how large an angle is acceptable between adjoining constant radius plates, and between the longitudinal edges of the constant radius sections and the curved edges of the topsides and bottom.

 

Not to mention the butt joint of the two plates and the fillet weld of the stringer all in one location. This is not good practice. To exacerbate this, you also have the transverse member butting into all this which also needs welding..thus a perfect triaxial stress raiser which must be avoided at all costs.

 

What causes the increase in the amount of welding; "at least a factor of 20" has been suggested? Is it the use of short sections to create a rounded "chine" instead of a simple hard chine? Is the amount of weld affected by how the short sections are formed; rolled or press-brake formed?

 

Depends on the run of the 'chine' and whether it suits long lengths pulled into shape , some of the chine runs are quite long for example a close to parallel mid body can have single 6m lengths of pre-rolled 'chine' that can be pulled into shape with very little effort. A good designer can take this into account.

On more complex chine runs it's more likely to be more segmented then the welding will be similar.

 

As Mike notes it is really whether one can use 1 sheet or as in the pic posted above endless little sheets, for the same area. The one large sheet clearly has less total weld length than all the little sheets to make the one 'large' sheet of coverage.

As to the 20 times claim, seems excessive, but the point is, it is considerably more welding.

 

Erk ! It's here: http://www.metalsailboats.com/BEZIER-HULL-PLATING-PART-2.html well spotted !

There should always be something in the specs for a minimum distance for the plate boundary to any framing member. It's in all the class rules.

And it pays to understand points and lines of contraflexure with metal structures. With any knowledge of stress patterns common sense would suggest you place the weld away from the higher stress areas....

 

here's a Bruce Roberts radius chine hull plated. This is a 48' built by Christensen Yachts in Sidney, BC. I believe these plates were all rolled to the same radius, but there is a lot of fitting involved.

 

As a rule of thumb when hull plating we work on a standard of the plate edge over hanging frames & stiffeners 12cm.
Same rule applies when replating a steel or aluminium hull, cut outs sections are never closer than 12cm to frame/stiffener

 

I think the only existing rule is to avoid making a weld in the heat affected zone of a weld before. So in my opinion, to separate the new welding, say 50 mm, from the previous one, is more than enough.

 

I apply the lay depending on size of vessel and material thickness. Most of my projects are over 20m to 45m, 12cm is the normal plus many are hi speed (35kn) CAT working boats so demi hulls undergo more stress.

 

Each one can apply the rules as seems most appropriate. If incorrectly applied, the construction quality will decrease. But the separation between contiguous welds has nothing to do with either vessel size nor the number of hulls.

 

Check with your class or flag authority. It's usually specified as a distance plus a multiple of plate thickness. Should be stated either be in the welding requirements or is simply presumed as known and will be marked as re-work by the class/flag surveyor (if seen).

Looking up GLLoyds which we use a lot, its given as [50mm+4t] for butt welds and [30mm +3t] for a butt to the nearest fillet. I haven't looked up any others but they will all be very similar.

[Edit]
Where t is the remaining time to knock off on Friday

 

MikeJohns,
It is quite possible that you're right. I have expressed my opinion because not recall ever seeing that standard in any regulation of Classification Societies, and have worked with a few. Not that there is not, but simply that I have not seen. I do not want to be misunderstood, I ask with humility and professional interest, but could you tell me how to find that standard?. Thank you.

 

Just ask whichever class you use for the info, they should send you something. Here's the GL relevant excerpt: