I think I need a new mast

[davidbfox]

Snapdragon 747 35 years old. Bad cracks between the triangle of rivet holes under the mast spreaders, extending upwards towards the bolt attaching shrouds to mast. The metal between the triangle of rivet holes is pushed inwards.

Unfortunately we only found this when tidying up ready for launch!

I guess I need a new mast. Anyone know what they cost in practice? Is repair possible? Is it worth it on an old boat?

Thanks in advance!

 

[LittleSister]

Don't know anything about new masts, but have seen various old ones advertised from wrecked/scrapped/lost/upgraded boats. You might find something of a similar size (doesn't need to be exact). Try Boats and Outboards website (if your patience can stand it!), local sailing clubs and boatyards), etc.

 

[lw395]

Many masts can be repaired, sleeved, welded, plated etc.
New mast would be nicer, but not cheap. would agree there are lots of s/h ones out there, particularly if you don't need the best for racing.
Bit of a downer finding out now though!

 

[William_H]

The repair can be relatively simple. You need to fit a sleeve of reinforcing around the mast under the spreaders.
The best source of sleeve material is an old broken mast or boom that is slightly bigger than your mast in thickness. Although the same size can be used. Ordinary sheet aluminium will nnot have the heat treatment that mast al has.

Cut the section to about 50 cms long thenn cut away the aft track area so that the sleeve can be sprung apart to fit around your mast section so extends aft nearly to the track area. ie about 3 cms short of the back of the mast.
You will have to drill holes for the shroud attach bolt first or at least mark where the old hgole underneath is going to match. Likewise the spreader base attach holes.
Paint Duralac on the mating surfaces then rivet the sleeve to the outside after pulling the sleeve as close the mast as possible.
Start drilling/rivetting at the front then move to the sides to pull the sleeve in close.
I imagine rives spaced 10 cms apart vertically. With a line of rivets near the front on each side another line about midway front to back and another line at the aft edge of the sleeve. Too many rivet holes will weaken the mast.
Use 3/16 inch monel rivets long enough to penetrate all the layers and you will need a strong rivet puller.

Refit the spreader bases and the bolt and tangs for inner shrouds.

You will find this repair very strong. I did something similar when I broke a mast and was used until a new mast could be sourced. I actually cut a section out of the mast because it was bent at the break.
good luck olewill

 

[oldharry]

I would go with WilliamH - repairs to this sort of damage are straightforward and should not hold you up too much. I had a similar problem on my boat last year where a spreader had beome entangled with something, and had been bent down kinking the mast directly below the spreader root.

Took all the affected fittings off - and the corresponding ones the other side, and obtained a sheet of stainless thin enough to be formed to the mast, and went over everything with at least 3 times the area of the damage all round (i.e. 25cms dent = 75cms radius for repair patch.)

Bedded all down with Durulac, then rivetted the plate in place using monel pop rivets same size as the originals - but not too many. The boatbuilder suggested 15 - 20cms apart to avoid weakening the spar.

Then the repaired fittings were fastened back on by the same means as previously. Looks good, seems to work, and the mast has not fallen down - yet!

I was recommended to use stainless, partly because another mast with a similar prob came back repaired with a stainless patch from the riggers shop, partly because stainless sheet is easier to source than an ally extrusion of the right size, and because the rigger pointed out stainless gives gives a much higher degree of form strength to the repair.

Doesnt take all that long to do, either!

Another boat I had also had a sleeve join half way up, which never showed any sign of stress or trouble.

 

[davidbfox]

Thanks for this advice.