Wednesday, March 14, 2018

________________________ GEAR BREAKAGES ________________________

 Rivet holes exposed after the goose neck fitting sheared off.

Last weekend I raced in the Onerahi Yacht Clubs two day, 8 race annual championships. There were 4 races on each of the two days. I came second in my division but not without incident. It blew very hard over the two days, these days being just before the downgraded Tropical Cyclone 'Hola' arrived. During the second to last race on day two, I gybed heavily and sheared the booms' goose neck off the mast. As you can see from the above photo the force of the gybe popped all rivets holding the goose neck to the mast.

 Goose neck fitting before reattaching with new rivets.

I continued racing although my speed to windward dropped as the boom lay on one side of the mast not unlike the boom of a lug sail rig.

Double sheave pulley with rope attachment becket.

As I continued sailing there was jerking of the main boom again and a rattle. The pin that held the mainsheet pulley becket (black plastic roller above) that the mainsheet ties to somehow fell out (probably due to all the flapping and rattling during and after the punishing gybe. The bowline I tie  that holds the mainsheet to the becket stopped the mainsheet from running through all the mainsheet blocks, and I continued with reduced purchase on the sheet. Luckily the pin and the little plastic roller fell into the cockpit and I was able to reassemble it after the racing was completed.

After the race when the goose neck failed and with one race to go I had the choice of either retiring from the racing or continuing and completing the last race. I chose the latter and tried to tie the goose neck back on the mast with a piece of cord. I succeeded in doing so but not before capsizing the boat while standing forward in the boat in a gale of a wind (first time I have capsized the Zephyr) ...... the boat went over and I went under with a big splash. Unfortunately the mast dug into the mud on the bottom and bent the wind vane which I had for the very first time attached it in its alternative position at the top of the mast. But despite everything I was able to right the boat and roughly tie the goose neck to the mast and complete the last race.

 Reattached goose neck filling.

I have been able to re - rivet the goose neck back onto the mast, fix the becket on the main sheet pulley and was able to sail again yesterday in the regular Tuesday twilight series. All the gear worked well again and we are really not that much worse for wear.

The OYC champs and the Tuesday twilight race were both held in high winds and I am pleased with the improved speed to windward in heavy air I am achieving since setting up the boat according to the advice I gleaned from Andy Knowles while sailing in the NZ Champs at Worser Bay. The Zephyr is a technical boat, challenging to sail well, and as I have said before I have only scratched the the surface of what's possible. Only time will tell whether I am able to race the boat at the top of its potential performance - in the mean time I will be enjoying immensely finding out!


George A said...

Wow. What did you do to effect the repair to the mast before riveting the gooseneck back in place? Did you increase the rivet size?

Out of curiosity, how much vang pressure did you have on during the gybe? The vang tends to push the tack end of the boom hard against the mast and perhaps beneficially reduces the stress on the gooseneck.

Alden Smith said...

Good questions. I was going to make and rivet an aluminum plate over the attachment area to strengthen it. What I did in the end was - yes - simply increase the rivet size from 5.8mm to 6.0mm. I had to search hard around town for this bigger size. The rivets are also quite long, so I am relying on a big pull back and squashing up of the rivet on the inside of the mast to fill out the holes which had become larger through corrosion and damage. When the goose neck came off some of the rivets were sheared off, some of them were pulled back through the mast wall.

I had a huge amount of vang on when all this happened. I sometimes ease the vang when going downwind which takes a lot of the pre - bend out of the mast and puts a bit of fullness back in the mains'l, but on this occasion it was blowing very hard and I didn't get time to alter any of the controls, I was too busy trying to keep the boat up-right and on course. The gybe was a 'hard' gybe rather than a 'soft' one - that is the full force of the boom was taken up suddenly by the main sheet which meant there was quite a long and powerful lever arm trying to rip the fitting off the mast. Sometimes you can effect a 'soft' gybe in high winds by rounding up into the wind a little bit as the boom goes over your head which has the boom floating free as the end of the gybe, which takes some of the shock loading off the mast and the goose neck - but not in this case.

I take your point about the vang pushing the tack end against the mast which is true, but I think in this case the shearing action generated in the gybe overcame any benefit from the opposing force from the vang.

George A said...

6 mm long reach rivets. Hope you had access to a pneumatic rivet gun--especially if they were stainless steel!

Alden Smith said...

I used a manual hand held rivet gun and used aluminum rivets - stainless on aluminum risks corrosion. I had to use both hands on the rivet handles to get the rivet to pop but it all came together well. Time will tell whether I have fixed it properly.

George A said...

My hands ache just thinking about it! Yes to the corrosion risk of mixing SS and alu. Having said that, I've used SS rivets in aluminum spars but always coat the rivets before setting them with a barrier compound. Even so, a carefully wash with fresh water after a salt water exposure is a must.

Alden Smith said...

Any stainless fittings I have attached on the mast and boom of my big boat 'Mariner' I have if possible mounted on thin plastic and and used silicon on the threads of the attachment screws.

So far as my Zephyr goes, I think SS rivets would be suitable for very high loading areas such as the vang bracket that attaches to the mast (which gets very, very highly loaded in high winds) - for other fittings aluminium rivets are fine.