ideal spreader attachment

[Robbie.g]

Something like this is pretty close.

Strong, looks good, straightforward fabrication, whats not to like?
IMHO...Cheers

[brm3]

looks nice. can do thanks

[brm3]

quick question . how does this design relieve stress on side compression of the mast?
thanks

[Douglas]

Ahoy bm , my Forespar mast fabricated around 1985 has spreader bases welded right to the mast wall .

FWIW , author Nigel Calder says this , in his second edition of Boatowner's Mechanical and Electrical Manual ,,,, page 484 , " ......... any welds around the spar produce a week section prone to buckling. Notable in this respect are welded spreader sockets, especially where the sockets wrap a good way around the spar. "

As for mast wall compression at the spreader bases , are you thinking about Z spar's through bar spreader base system ?

[brm3]

yep. you got it. I've seen the bars and the sleeved bolt option. My mast is oval so compression tubes would be challenging. I'm trying to either copy a solid design or come up with something to fit the bill. My wall thickness is 3/16" but I want to be safe with the loading at the point of compression on the wall.
Thanks

[Jim Fulton]

I would expect that a rigid connection between the spreader and the mast like that pictured would increase the likelihood of metal fatigue at the joint due to vibration. All of the spreader bases that I have seen (or paid attention to) have some allowance for the spreader to move, at least a little. Am I off base here?

[brm3]

I guess it would depend on the amount of deflection resulting in flex inducing fatigue. I'm still curious if the side compression of the mast is really a problem. Nigels book raises concern. Is this opinion or fact? Does anyone know? I know how stories can be mutated to unreasonable point.
Thanks