Frameless steel hulls: Is there a lenght limit?

It is still a frame

WHo said you need a complicate & huge frame. I can design a ship with a double hull, a floor, and a deck. That is the frame.

 

Jehardiman, great post representing the material efficiencies of using framing to steel.
Xarax, if you want a nice little boat, the Van DE Stadt 34 is still a pretty & valid design & formed up as frameless then frames inserted to accept bulkheads for a standard & functional fitout, the keel is supported by webs welded to floors that the tops of are level to support the cabin sole, chainplates attach to deep hanging knees possitioned for the purpose & help frame the settee backs, the decks use curved angle beams that headlining material easily attaches to. Very economically constructed of 4mm plate to hull & 3mm to deck in steel or 6mm & 4mm in alu & is a great start to getting a nice yacht of reasonable performance. Regards from Jeff.

 

I repeat - Frame does not take up space if done right

A boat needs bulkheads, compartments, these are frame.
fuel tanks, water tanks can be and should be part of frame.
Floor and its frames, creates bilge separation between bottom of floor .
Deck is ceiling and upper frame structure.
If you dont have a frame where are you going to attach engines.

 

It could be a sailboat and then you don't nead engine.

If a outboard then it's not inside the boat annyway.

If a inboard it's normaly attached to the engine grider.

There is also limited how manny bulkheads you want to have and also how manny compartments. If the deck surface is big enough you will nead frames to hold it up so it wont bend when people walk on it.

If weight is a ishue you would like to keep enginegriders to a minimum.

 

Decks , chines, built in tank tops, keel and skeg structures al consitute fully welded longitudinal bulkheads. All parts of a sailboat hull are curves of one form or another. The ends of an origami hull are cones with the apex of the cone being the start of the chine. Between these are portions of a cylindre. Calculations for transverse frames are often made on the naive assumption that we are dealing with flat surfaces. Longitudinal stringers are far more effective structuraly on hard chine hulls than transverse frames, as any pressure on a longitudinal, along a curve, would put a compression load on a longitudinal , but siimply put a bending load on a transverse frame. It is easier to bend a piece of material than it is to compress it on end , especially if it is welded to the plate.
The biggest frameless origami boat I ever built was a 47 footer , which completed a circumnavigation and is now cruising portugal. A friend built an origami 60 footer which is still cruising, after 30 years.
Several friends have 55 footers which have cruised the central Pacific and the Northern BC coast in all weathers, year round. None have transverse framing.
Brent Swain.