Hi Graham,

a couple of years ago I got some quotes for a bare aluminium tapered tube from China via Alibaba (170 mm diameter, 5 mm wall, 11.8 meters long), the cost was just over $700 US but the transport cost was over $800 US, so I did not go ahead with the purchase. Since then I have found out that the transport cost can be reduced dramatically if you contact a local importer and get him to include it in one of his containers as part of another shipment and have the pole delivered to him in China. It could be worth some investigation.

All the best, David.

Maxime wrote:

More from my mechanical engineer friend:

The fibreglass wrapping is useless for increasing strength, and will be counterproductive. He says, don't cover it, leave it visible so you can see if any cracks start to develop. He also strongly suggests to use a circular deburring tool or very fine rat tail file to smooth out the edges of those holes. Deburring tool would be best, to deburr inside and out. This will help avoid stress raisers. And David's suggestion of inspection dye is very good.

Your engineering friend may be right, Maxime.  I am no engineer, more of a monkey see monkey do sort of guy.  Rounding the edges of the holes makes sense, since the cracks develop because of concentrated stresses at sharp edges.  However, I have already filled the holes with epoxy putty and put a structural sheathing around the mast.  My hope is that the stresses will flow past the holes. If not, I'd hope to see some cracking of the glass sheathing.  If I am wrong, the mast may indeed fall down.  If I find a 10-11m tapered alloy tube with maximum diameter of 170mm and 4-5mm wall thickness I will buy it, but no luck so far in Australia.  Arion's mast, which was a beautiful object, came from France and cost me $4000 in 2011.  So I am going to take David Thatcher's good advice and keep sailing with a weather eye peeled.   I appreciate all opinions.

Anonymous wrote:

I have wrapped four layers of 100mm wide 6 oz E glass impregnated with epoxy resin around the mast in a continuous band.  That is 24 oz of epoxy/glass sheathing, and I am hoping that this will inhibit any tendency for stress cracks to develop at the edges of the holes.  Time will tell.  That just leaves another 30 or so holes in the mast!  The boat has sailed several thousand miles on the open ocean in the last decade but I cannot say I am confident.  However, I plan to mostly cruise in the sheltered waters of Moreton Bay for now, with just one 40 mile ocean hop from my base in Mooloolaba, which I will do in quiet weather.  I'll keep a close eye on it!

More from my mechanical engineer friend:

The fibreglass wrapping is useless for increasing strength, and will be counterproductive. He says, don't cover it, leave it visible so you can see if any cracks start to develop. He also strongly suggests to use a circular deburring tool or very fine rat tail file to smooth out the edges of those holes. Deburring tool would be best, to deburr inside and out. This will help avoid stress raisers. And David's suggestion of inspection dye is very good.

That's certainly true. My experience at Kemp Masts, fatigue testing aluminium mast sections, was that failure was generally due to cracks propagating out from holes, both large and small. All that can be said for sure is that eventually, failure will occur. When? No way of telling, but if lasts longer than the boat or the skipper, it's immaterial. A good way of getting advance warning of failure is with dye penetrant inspection. There are many brands of crack detection kit available.

In the long-running saga of trying to turn a mediocre little boat into something halfway acceptable, I've been busy fitting a self steering gear, replacing the large windows with small bronze deadlights (I hate glare and also prefer the look of deadlights) and soon there will be a hard bimini.  I have also abandoned the junkette rig, and Paul Thompson has built me a cambered junk sail out of Weathermax 80 which I have just started fitting.  I've always been a bit dubious about this untapered alloy mast which has at least 50 holes in it above the partners where fittings are attached, including a vertical row up the aft face for an internal cable conduit.  I keep reminding myself that the boat has sailed several thousand ocean miles with this rig. 

But it was when I took off the top section of the gooseneck base and saw the row of holes underneath that my heart really quavered.  It just needed a sticker saying, 'Tear along the dotted line'.  It seems impossible to remove this mast without destroying it or the partners, being a tight fit and glued in, and I am reaching a stage where I cannot bear to spend much more of my dwindling finances in replacing the mast.  So I filled the holes with epoxy putty and wrapped four layers of 100mm-wide 6oz E-glass tape  embedded in epoxy around it.  I have no idea if it will be strong enough but plan to sail gingerly when I get going again.  Here's what it looked like when I took the fitting off.  You can just see the bottom half of the bracket at the lower edge of the photo, under which will also be a similar number of holes.  But the fitting is both riveted and glued over a gasket so that one is probably going to be left in place.  The boom should sit just above it when furled.  The upper bracket was a devil to remove.

Other Blue Moon photos can be viewed here.

PS: I have just updated the link above because I forgot I needed to link via my directory profile.  It should work now!

PPS:  I am waiting until I have a photo of Blue Moon flying her new burgundy cambered sail before I change my avatar.  Doing so will also be painful, the last goodbye to dear Arion.