Thru-Bar Spreader Bases

[Douglas]

Has anyone had experience with the Z-Spar "thru-bar" spreader bases, causing a mast wall failure ?

One rigger says : " We do not use through-bar technique for spreaders assembly as this creates too large cut outs in the mast section. I have a recent example here with a brand new production mast snapped at the cut outs level."

An example of this "thru-bar" detail can be seen at : http://www.zsparsuk.com/mastpic007.jpg

If I do choose to use this "thru-bar" spreader base system on my new mast, would an internal sleave reinforce the mast wall, to offset the weakening of the mast wall due to the large horizontal bar cut out hole ?

Douglas

[Brian Duff]

Root Bars are fine, as long as the mast and rig are designed for the boat, they will work great. Provides a low cost and low weight and low windage way to terminate spreaders and shrouds all in one. Not my first choice, but the set up is on a whole lot of yachts out there.

A failure at the tru-bar (spreader root bar) cut out is more likely due to a very loose or poor rig tune, mishandling of the boat under sail, or perhaps a tune specific to a certain class of boats racing habit and backstay power, not just becasue of the missing material at the cut out. (some racing boats sail with very loose aft lower shrouds so the mast can be bent dramatically to flatten the mainsail in stiff breeze, and this causes excess fatigue and failure at points like rootbar cutouts)

A great many spars are made with this spreader design, and it works fine. The section of the mast used is required at the mid point between each rigging termination (middle of the panel). Having the cut out for the root bars does not weaken the mast as one would imagine becasue these are at the panel ends.

Try calling Zspar ( or rigrite I guess) or call Hall Spars, GMT Spars, Charleston Spars, Novis Spars, Southern Spars (and probably others) , i believe they all offer root bar spreader designs.