Fixing the gooseneck

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(If you have forgotten what the projec t was about, see first page.)

My temporary repair in Port Vila worked well all the way and we arrived safely in Australia a couple of months and 1 500 nautical miles later. Somebody even joked that the arrangement probably was stronger than the original design.

Corrosion between the boom fitting and the mast

It's amazing what salt water will do to a combination of aluminium and stainless. Scorpio is 29 years old and this project was certainly not undertaken too early. Our gooseneck fitting was secured by 19 bolts of 6 mm each, but I have seen smaller fittings bolted to mast by just 6 screws.

The plan

At first, my plan was to enlarge the original bolt holes in the aluminium mast and put in threaded rivets (or threaded inserts, as they are also called). After talking to several persons I changed my mind, and decided to minimize surfaces that would be affected by corrosion. Therefore I decided not to use the old holes, instead I planned to drill new holes at the mast in areas where the aluminium had suffered the least (the original profile was 4,7 mm thick).

The performance

First I took the fitting to a welding fabrication shop (Jim Kahler at Bundaberg Port). He suggested that we use panhead screws insted of recessed ones, to minimize voids where corrosion would build up. With the new holes in place I used the fitting as a template for locating new holes. The new holes in the fitting are 6.5 mm. I used a 3/4" drill bit and 1/4" tapping tool for the new 1/4" bolts.

1. Most bolts on starboard are now out
2. Corrosion between trysail track and fitting
3. Fitting is now off
4. This shit is corroded aluminium.
5. The whole area exposed
6. Gooseneck and fitting for the mast.
The pin holes are elongated.

1. Most of the stainless bolts on the starboard side had sheard and the part remaining inside the aluminium profile had to be drilled out.

2. In this photo you can clearly see how the aluminium of the try sail track has deteriorated in contact with stainless and salt water.

3-4. An amazing amount of "gravel" came out behind the gooseneck fitting. Some call it aluminium oxide.

How's this going to end?

Actually, before the drilling of the new holes I had prepared the area: Cleaning of the metal and applying epoxy paint and filling the old holes with epoxy filler. The paint preparation served two purposes: building up the mast surface to original size and protection of the metal (as the anodization was gone).

7. Old bolt holes and first layer of epoxy paint. 8. Two layers of paint and holes filled, once. 9. Three layers of epoxy and holes filled twice.
10. Old boltholes filled and new drilled next to. 11. Reverse side, new holes + traces of the old. 12. Tapping threads into the new holes.

7. On the starboard side there was a lot of extra holes where the try sail track had been fastened with pop rivets.

8-9. The surface was sealed with several layers of epoxy paint (Altex: Altra-Build 540) and the old holes filled with epoxy resin filler (International: Epifill).

10. Here you can compare the location of the new holes with the old ones in picture #6. We only kept one hole in the original location: the one in the centre, which was hard to access.

11. This is not Swiss cheese, but a gooseneck fitting.

12. I tapped the new holes with the fitting in place, then took it off and bedded with Sikaflex 291UV to get a good seal and flexible bond. Trying to minimize moisture in the threads I applied Duralac anti-corrosive joining compound on the bolts before retightening.

The extra bonuses

As with all my boat projects, also this one escalated. So far I had been able to do most of the work by myself aboard the boat anchored in a bend of Burnett River close to Burnett Heads. We were only 50 metres from the shore and a 300 metres walk from Jim's work shop. I had early realized that both pins at the gooseneck itself had to be replaced and the elongated holes corrected, which could be done at the work shop.

13. The hole for connecting the boom to the gooseneck was badly elongated. 14. The hole was drilled larger and a sleeve of stainless steel fitted. 15. The base of the ring for the main sail sheet on the boom was also badly corroded.
16. New material is welded in place to compensate for the loss of old. 17. One epoxy primer coat is now on 18. On a sailing vessel, at least you have ways to move heavy things and hold them in place.

13. But the hole for connecting the boom to the gooseneck could not be properly fixed without bringing the boom itself to the workshop. I decided that I wanted the whole project to be finished properly and, with some effort, had it taken ashore.

14. Jim drilled out a larger hole and fitted a sleeve of stainless steel, so we got a good fit for a new bolt.

15. Now that the boom was in the work shop anyway I decided to have a look at the claw ring (the fitting used for connecting the main sail sheet to the boom), which proved to be a very good idea, indeed. Fortunately the builders of the yacht had put a stainless plate on the inside of the profile, where the bolts holding the fitting were secured. Without that plate I think we would have been in the piss some time ago already!

By the way, this revelation makes me wonder why they didn't use a similar design also at the gooseneck.

16. The bolt is original and it is keeping the internal stainless plate in place.

17. I used Internationals PA-10 Etch Primer (grey and red) under the epoxy paint.

18. The weight of the boom is probaly well over 100 kg. We took it ashore in the dinghy!

19. The main sail sheet connection fitting (think it's called a claw ring) is back on the boom. 20. There we are, looking pretty good. 21. That's it, now somebody put the main sail back again!

19-21. All the hardware were bedded in Sikaflex and the bolts soaked in Duralac (see text above). Both bolts through the gooseneck (horisontal and vertical) are new and the holes are fitted tight.


If we could have waited with the repair until the time for our next haul out, I would have pulled the mast out and everything would have been much easier. Instead of working with house hold electrical tools small enough for my inverter aboard all tasks could have been done using professional equipment. One thing is certain though - in that case the project would have escalated even moore, cause I would have checked all fittings at the mast!

Next time I have the opportunity I will check the shroud fittings, the climb steps, the sail tracks and whatever else there is of stainless steel bolted to the masts!