Cracking Wood Mast! Shrinkage?

O

out_to_sea

Well-Known Member
Joined
23 Mar 2009
Messages
72
Location
West Yorkshire
Visit site
Hi all, I helped a friend out with some maintenance work on his boat on Thursday. His mast has been in storage under cover for the last 18 months.

When we got there the mast has what looks like shrinkage crack running about 2 metres long, 3 metres up from the base and in places up to 75mm (3 inch) deep in places and about the width of a pound coin. The crack is pretty strait and the mast is around 150mm in dia.

I'm after some advice on what to do, I know there are lots of very knowledgeable people on here but I must ask, could you only offer a suggestion if your competant do so. I really don't want to be half way to Holland and loose the mast

A photo should be uploaded soon hopefully

Thanks very much
 
See my last post on PBO, but you will probably get plenty of info on here.
 
Drill into the mast on the line of the crack to stop the crack spreading any further. Fashion a sliver of timber the length, width and depth of the crack and glue it in place. This should taper in depth, as that is the shape that the crack will be. This is not a rare problem with wooden masts, nor is it likely to be mast- threatening, especially after repair. I have seen shipwrights deliberately saw a slot along a log which is being shaped into a mast to relieve stress in the drying log. The slot was later filled with a strip of matching wood, glued into place.
Peter.
 
OPs image
[image]
Picture1-1.jpg
[/image]
 
Looking at that, I'd go along the crack with a Skilsaw to clean it out and to clean away the fibres that cross the crack. Use a feeler gauge to see how deep the crack goes, and set your saw for about 2/3 of the depth. That should then give you a slot of fairly consistent width and depth. Yes, it'll be a very feasible repair.
Peter.
 
Thanks All,

Peter, I've got a router but never used it but its a big bugger. I'll ask around and see if I can borrow a Skilsaw off someone, what would do we use to fill the gap up with? Are all masts made of the same stuff?

Thanks for all your help!

Andy
 
Doesn't the answer depend on whether it is caused by temporary shrinkage from being stored in the dry, or is permanent?
You surely shouldn't glue a fillet into a temporary crack?
 
I'm with Clifford. I definitely wouldn't put anything hard in the shake. I think the usual drill is something soft that will stay soft once the mast is back in commision - on the basis that it is likely to be squeezed out. Only if the crack didn't close up would I think about routing out and filling / gluing etc. I am definitely not the expert you seek but wouldn't want you to go the wrong route without some further advice. SeaNick where are you?!
 
That was our original concern that anything inserted (resin or wood) would act like a wedge if it rehydrated.

If it doesn't look like a massive structural failure we could go for the putty route and see what happens after 12 months of use again?

It was suggested we could put a stainless steel band around it, but I'm not sure what good that would do?

Cheers

Andy
 
If the mast it hollow, glue in a spline, of pine.
A skilsaw will give a poor slot, a router with battens and guides set up will do a neater job, in skilled hands. If it fits well, use polyurethene glue, if its a poor fit, use epoxy.

If the spar is solid, then simply fill with soft stopping.
Although the spilt is large, it will not compromise its strength to much,.

It looks like the mast has very few coatings, hence drying and splitting. It probably won't close up much as it won'tbe submerged, will it??

A metal band will achive nothing.
 
I'm pretty sure its solid, should we drill the ends of the cracks?

I hope it won't be submerged!!! if it is we have bigger problems /forums/images/graemlins/smile.gif

Thanks for the help

Andy
 
As to drilling the ends, not sure it would make much difference, though it does help in metal structures.
Adding to what I said above, I have tried putting spars in the sea for few days. The splits do reduce in size, and of course the salt water will preserve the innards. However, they do dry out again, even if well varnished.
I did spline up a solid bowsprit for an experiment. I raked out the spits, made up tapered splines and drove them in with planty of glue. Although this is not the done thing, it seems to have worked. The spar has occasionally bent like a banana, and stayed intact. It has a good ring to it too.

Get it sanded and coated asap, no microporus sludge though!
 
Sorry to bother you again, but what products should we use to fill the crack with?

Do we need to treat the crack with any anti rot treatment? I haven't seen any signs of dry or wet rot.

What should we do with the mast? sand off loose paint then coat it with? I think we will be painting it white I just don't know what product to use, hopefully one that doesn't cost a fortune!

Thanks Andy
 
I would not paint a wooden mast. I would go for a clear covering so that you can see the wood underneath and spot any problems that may be developing. If you paint the mast you would not be able to see the wood blackening if you have water penetration etc. For the covering ideally I'd suggest Coelan, but cheap it aint!
 
Thanks very much all, yet another success for the YBW forumn /forums/images/graemlins/blush.gif)

p.s. Kathy, what ever varnish you've been using send some my way... sailing in the 1950's!!! you must of only been a twinkle in your daddies eye... /forums/images/graemlins/smile.gif
 
There seem to have been two completely contradictary answers to this problem, never resolved or commented on.
One says the gap may close up and on no account should be filled with anything hard, the others says glue it up tight.

Normally we are strongly advised to consider all cracks as potentially temporary (eg planking) with dire consequences if they are not given flexibility. But here we have some obviously knowledgeable people advocating the contrary.

Puzzled.
 
I view it as two options, fill it with soft stopping as advocated by seanick or the clamping and glueing by Kathleen, both have there merits and I'm not sure which is best, but I'm not the owner of the boat but I'll keep you posted!

Cheers

Andy
 
Agreed. I'm not doubting Kathleen's knowledge or credentials (impressive as they are) but I personally wouldn't go down the epoxy route on this. I would personally fill with soft stopping and go from there. If still the same size after a few seasons then maybe look at the potential of epoxy fillin.
 
Assuming the split or shake has been monitored and has ceased moving? Auger a hole at both ends of the shake equal depth and width.
Rout a regular slot along the shake, form a fillet of moisture and species matched timber. Butter the fillet with Rotafix RSA a flexible adhesive with a minimum bond strength of 6N/mm squared, mallet the fillet into the slot, allow the adhesive too cure. Auger a 8-10mm diameter hole at both ends of the slot, inject RSA into the shake until refusal, one hole is a fill point, one an air release point. Dowel the auger holes - job done a tried tested method of repairing shakes and splits
 
You must log in or register to reply here.

Share this page

Top