[MHml] Wracking

[multihulls at steamradio.com]

Robert

Plug welding is used where the strength of a weld is desired and room is
lacking for the required length of weld.  It should be as strong as any
weld in Al if engineered correctly.  Think of them as a series of filet
welds, the length of each one would be the circumference of the hole.
I think I would trust plug welding over glue and rivet for use in
crossbeams, the welding QC would be easier on the welds than on the glue
line (whether or not the glue filled the gap between beams completely).

Marty Voss



Plug welding?  I am just a simple doctor and would have to ask a rigger how
it is done, but from the appearance of my beams, I would suspect that the
outer beam has holes about  centimetre in diameter drilled in it, through
which it can be welded to the inner sleeve, resulting in a plug of new
metal
which is visible on the outside (and which is ground flush before
anodizing).  Maybe someone with some experience of the technique can
comment?  As I understand it, glueing-and-rivetting is stronger - there is
said to be a risk of failure at the plug weld holes, though I have not
talked to anyone to whom it has happened.  (None of the welds are near the
straps which hold the beams into their sleeves in the case of the fore- and
aft-beams, which is where I guess the point loads are highest.)