Best alloy for Durafix style brazing sticks

[Adrian Harris]

I'm rethinking my Sherman hull construction and considering using Durafix alloy brazing sticks to join the floor to hull sides and rear plates.

As I have a choice of material from which to cut the parts, has anyone found any noticeable difference between say 5000 series alloy and 6082T6, which seems to be the standard offering

I have had one hull professionally welded, which cost £100, and I've had a go at fully brazing a hull myself, with Durafix sticks. The join was OK but the heat needed warped the floor, as it is half the thickness of the hull sides.

I'm thinking that it should be possible to tack weld the sides together, then slowly build up the number of attachment points, as the thermal conductivity of the aluminium should prevent adjacent joins from coming undone, especially if I use some steel as heat sinks. Doing it this way means that I only need to heat up around an inch of join at a time, so the thermal expansion should be minimised.

Adrian.

[Stephen White]

Adrian hi.

My experience has been mostly with 1050A, which is a softer alloy. I've found that although you can get some wider distortion of sheet in achieving the localised temps around 700C needed for brazing, it's manageable. With the annealing effect, the distortions can be straightened easily and by and large they have disappeared on cooling. That was my experience assembling the external tank on my Cent, which is the largest piece I've tried. I'd certainly recommend the use of heat sinks. I've been using a series of different sized G-clamps.

I think the brazing rods available commercially are all pretty much the same. I've been using Lumiweld from L-B Restorations in Cornwall.

Good luck.

Stephen