Welding the skin to the frames demystified

You can calculate shrinkage quite accurately too and actually incorporate it into the panel, any shipbuilder has to take this into account and it also drives the welding schedule of what gets welded to what where and when.

In the last days of rivetted vessels the plating was welded on the butts (the vertical plate joins) and riveted on overlapping longitudinal seams and riveted to the transverse frames, many of these boats were incredibly fair (and still are). But welding is much more precise afair these days and consistent shrinkage with MIG processes and a reasonable welder can produce welded vessels with very low distortion.

In a good shipyard you will find masters of line heating that can flatten or curve a sheet of steel with surprising accuaracy.

 

i learnt to shrink when I was 13, do not scoff, I worked sweeping floors in an old fashioned panel beaters shop
they would get me to heat, a penny sized spot , and then quench
Later in life, when I was steelbuilding, I used this techique when getting rid of a BUBBLE in a plate
The Dutch covered the decks wet straw for shrinking
Of course in those days as a beginner, I did not have stretching and forming gear, so often my plates got too wide, hence the need for the shrink
i have seen beautifully fair rivetted ships, and I watch these silly welding threads with amazement, just imagine an old time shipbuilder reading this stuff, and stuff abt arc strikes, which goes on and on and on, ) come on!!!

 

Hi all,

I've searched across this metalbuilding section, and it seems this is the only thread to ask...

Well, are there any recent successfull examples of the 'plywood' techniques applied to alu/steel hulls?
I mean: upsidedown bulkeads or frames first, then stringers, then plates, join everything with spots, then turn for a better welding end so on...

Or stitching plates first, and then fittinng frame structures/longt.beams is the only proper way of welding a 10-20-40ft vessels?

 

Your question has me confused as you seem to imply building a metal boat by adding the frames in a stitched skin would be mainstream building construction?

Most metal boat are built as what you refer to as "plywood" technic. A framing structure is erected first and the skin is tacked on after. Building upside down or upside up is a question of preference.

You also mention 10 - 20 - 40ft vessels. There is a world of difference between a 20ft and a 40ft boat, for design, material choices and building technics. You might want to narrow your research to the type of vessel you are curious about.

cheers,
Murielle

 

There are (at least) 2 ways of building metal boats.

1. Frames & stringers first followed by hull plating. The variants here are building upside down or right way up. There are pros and cons to both. I chose to build right way up, worked fine for me.

2. Skin first then frames. Once again a couple of variants. One is the so-called origami technique where you torture flat plates to make a hull shape then add internal frames as needed. The other way is the Van De Stadt way of building a female cradle, laying up the plating then adding the frames.

If I was building a single hull I'd build frames first, upright, to minimise handling. If I was building a number of boats all the same I'd build the female cradle system.

This is all based on building a chine type hull. For a round bilge then really framing, whether upright or inverted, is really the only practical way for a one-off.

I didn't rotate my hull, I just did the welding overhead, vertical up/down as required. A rotating setup is good for multiple hulls, kind of doubt the practicality for a one-off.

But it all can be done, there are lots of ways to skin this cat.

 

Picking up on Muriell's post..

There is an article written about how to sequence build a metal boat in Professional Boatbuilder magazine, Oct/Nov 2014, called - Order of Assembly.

 

Or Tom Colvin's book on steel boat building. Or Gil Klingel's. Both written for amateurs starting out with nothing more than a flat place to work.

The hull is the easy bit.

 

Where's a 'like' button here?
Thanks all!..
Now reading Pollard's 'Boatbuilding in Aluminum', as intro.