how strong is a weld

[PabloPicasso]

Making a new forestay attachment point forn a pals boat. intend to use M12 S/S bolt through the existing hole in bowplate/deck.

How strong is a (professionally) made weld likely to be between the S/S m12 bolt and the forestay attachment bracket also S/S? I mean, will it sustain the full load of a taunt forestay?

 

[Bobobolinsky]

material thickness, cross section, design, all have an affect

 

[PabloPicasso]

M12 bolt hex head onto the edge of 5mm A4 S/S plate?

 

[Avocet]

It's a bit tricker than that. You'd have to show how the 5mm plate itself was restrained. An idea of what direction the loading is in. An idea of the size of boat would be useful, but a sketch or photo is probably going to be necessary before anyone will be able to say much more. In general terms, assuming the grade of bolt and stainless plate are broadly compatible, a good weld, in pure tension would probably have about the same cross sectional area as the shank of the bolt (if you welded the bolt head so that two opposite corners lay along the line of the plate (rather than two opposite flats sitting across it). The devil is in the detail, though. Often what's fine to take the design load can fail in fatigue because of smaller cyclic loads in different directions. For example, the main load on a stemhead fitting with a forestay attached to it, is from the tension in the forestay, but when tacking (especially if the forestay is a bit slack) there can be quite a big side load in it.

 

[PabloPicasso]

28ft boat . current arrangement is as above but bracket is turning in the hole a bit due to spinning of furling gear. Considering making a new bracket bolted it two places to prevent twisting.

Existing bracket has been in service for many years ,possibly since 1980s. Has not failed and is still in use but thought it woild be good to prevent the movement above.

 

[Bobobolinsky]

I think, I would use threaded rod, rather than a bolt, with cheek pieces of plate. The rod ground down to 5mm and flat bar, welded onto the bracket and the rod. Welding onto the edge of 5mm plate may be subject to fatigue.

 

[wklein]

The weld should be absolutely fine, however i try whenever possible not to use welded fittings in standing rigging as they can crack due to corrosion or overheating during welding.

 

[Blueboatman]

Can we assume that with the new set up the furler is free to articulate in both fore and aft and lateral directions-just like your shroud terminations at deck level?

Can you weld two plates drilled to 12mm thus the new pin cannot swivel?

(A photo would really help with this sort of question, as you can 'see')