Aluminum Mast Tapering

[Brian Duff]

hey riggas

so i have never cut a mast taper on an aluminum mast before, nor has my welder. the day always comes to expand horizons....

In order to learn the process (and to get a faster spar for my little wooden penguin) I have bought a DM-1 section and my welder and I are going to learn the process. I have spoken with a couple riggers I worked with in the past, and have been instructed to simply cut a straight sided wedge out of the front side of the mast, squeeze it shut, clamp something that will stay straight to the back edge and weld the thing up.

Anyone here have any advice?

while I am eager to learn the process , i would rather not trash a $200 extrusion through some stupid mistake.

thanks fellaz

[Douglas]

Ahoy Brian , three things come to my mind about welding long joints.

One is trying to prevent ripples caused by heat distortion, maybe also called puckering, on long linear welds.

Two, is that the welding heat causes a loss of temper near the weld.

and Three, is later corrosion that seems to start under paint around previously welded areas.

Please DO let us all know, how you decide to go about it .

Enquireing minds want to know.

Douglas

[Brian Duff]

Thanks Doug. We know about all that. We have done PLENTY of metal work. built spars, car bodies, signs , railing, boat fittings, underwater turbine intake grates,and on and on and on.

What i am after is details of the shape and placement of the cuts made to create the taper. well i can see from spars I have worked on where to do the cutting, but am not sure if the cuts should be straight sided or camberd, and weather I should do one on centerline or two cuts (one on each side). I guess cause its such a small spar one on front will be enough. but I am tapering alot of section away....


still searching...

[Brian Duff]

Penguin DM-1 Aluminum Mast Taper : I suppose I am cutting a straight sided V from the mast, centered on the front of the spar, to create this taper. The width of centerline will be 1-3/8". This taper is going to run 8' down to end in a point, which will have a 1/8" radius...then I suppose I will bend the sides in (almost 25*!) right at the aft mast 'wall' to close this V... and weld it? Ta-da

Hope this is right- speak up if you can, and will!

I am off to Florida to pull the rigs from a little ketch, so circular saw day is probably not till Thursday...of course that's also the first day of Boat Show

Too many fun things to do.

Thanks guys

[Brion Toss]

Hi there,
As I understand it, the taper is cut out of the side of the spar, not the front, so you cut a wedge out of each side. That way you won't be messing with two planes, or distorting the front's radius. And of course the aft face of the wedge is vertical, so only the forward portion of the mast bends back.
Fair leads,
Brion Toss

[Douglas]

Oh , very nice reply Brion , Heaps of intuative, information and insight there,,,, say what do you think about having a radiased curve at the apex or bottom of the vee cuts,,,,, on port and stb ?

This radiused curve looks like the bottom loop of a "J" !


Douglas