Stavanger, Monday

It appears that there is a big gap between Sunbird Marine’s and Hasler/McLeod’s view on mast scantlings.

When using the SA of Lexia’s foresail (217sqft/20.2sqm) and guessing the LAP of the 30’ foremast to be 8m, fig 8.16 in PJR ends up with suggesting a solid wood mast with a diameter of 20.4cm. That should give a breaking moment of around 3800kpm.

The aluminium mast section of 5" x 0.25" (127 x 6.35mm) as suggested by Sunbird Marine, should give a breaking moment of only 1690kpm (still 2-3 times stronger than the 3.5" mast which broke). It would take a 7" (x 0.25") section to equal PJR’s wooden mast.

A 6" x 0.25" section should stand up to about 2500kpm.

Who is right? Two things are sure. Lexia’s mast lasted for 30 years. That is good. Then it broke. Not so good.

My hunch is that the thin masts from Needle Spar may serve well enough for ordinary coastal sailing (in motoring distance from harbour). However, Ostar racing is anything but ordinary and calls for stouter gear.

The righting moment of a 4.6ton Sunbird 32 should be somewhere between 2500 and 3500kpm. If one wants to go dancing Atlantic Rock’n Roll, one must have masts that reflect the conditions and the boat's stability.

I am still very unsure of how one should distribute the loads on the two masts. Much simpler with sloops...

Cheers, Arne

Jonathan Snodgrass wrote:  At dawn the wind dropped and we wallowed at around half a knot.  If I had been just cruising I would probably have thought fine, let's wallow whilst I get some rest.  Alas, I thought that I should get some sail on and as it was pretty much dead calm I put both sails up fully.  I went below and set my timer for 15 mins.  As I woke up I noted that we were sailing much faster.  Just as I was getting up to look out the foremast went over the side, breaking at the deck. 

So, my fault I think.  A bad decision, perhaps made because I was tired and was very sea sick.

Absolutely not, Jonathan.  Even if you are keeping watch, on a dark night, a black squall can come at you unseen and raise the winds force from 3 to 6 in a few seconds.  Any rig should be able to withstand this.  The boat should look after the crew: not the other way round.

Or maybe it was a failure waiting to happen.

I fear that you are correct, here.

Uninsured as I was technically racing.  Salt in the wounds.

Arne Kverneland wrote:

This was only varnished (2-pot Polyurethane) and I suspect that this has given the epoxy less protection from the sun than the paint on Johanna’s mast does.

I think you're right here: I re-glassed two masts in Capetown and varnished both.  They lasted for about 7 years of total neglect before the glass started to fall off.  Had they been painted they would have probably have lasted 15 years of equal neglect.

The strong argument for the hybrid mast is that it is so quick to make. The dug-out spruce mast called for quite some work to build (but not super accuracy) and also long waiting for the log to cure. Building from staves sounds like a BIG job and calls for high quality at every stage. In comparison the recent construction of my new hybrid mast was a walk in the park.

Not only quick, but quite a lot easier for someone one their own and/or with limited woodworking skils, like me.  I would have been dubious building what is essentially a square mast for a boat the size of Fantail (while it worked just fine on the 1-ton displ Missee Lee), but for the topmast, which only has parrels against it in light airs, I felt quite happy about it.