Preparing our Mizzen Mast for Dyneema rigging

Today it was time to start getting the mizzen mast prepared for the Dyneema Rigging.

FR4 Tangs

Jane got busy on carving the FR4 mast tangs. We need 8 (2 forestays, 2 cap shrouds, 2 lower shrouds, 2 running backstays). This was working with the basic “triangles” I cut the other day (see DIY Mast tangs for Dyneema:¬†progress).

We did vacuum up the dust from the workmate and from the tarp as we went.

Between getting started, interruptions and recharging the dremel she managed nearly two completed tangs today. They are getting a bit quicker but it is going to need quite a few more days work!

Mizzen mast prep

Meanwhile, I started work on the mast itself.

There were some things we knew we needed to remove:

  • one remaining radar reflector bracket (the other has already broken off)
  • the radar mount (we no longer have radar, we would not trust a new radar to this mount!)
  • the deck light (we want LED and it was in poor condition)
  • a couple of plastic cleats (one of them broken). There are already 4 original alloy cleats and only potential for 4 lines at the mast head.
  • the VHF aerial (we need a new one for both VHF and AIS).

When we saw how much corrosion was under some of these (indicating that the different metals had not been electrically separated causing galvanic corrosion) we decided that this is our best opportunity to do a full refurbishment.

So as well as removing the deck light we also removed the external channel for it’s wire (that was riveted to the mast).

Having decided to do a full refurbishment I spent some time doing research. We have decided to go for a full epoxy paint. So we are removing anything that doesn’t look absolutely perfect. At the lower end of the mast the gooseneck, winch bases and original cleats are all looking good, plus they are low enough that they could be removed and refitted with the mast up.

Further up the mast the two higher shroud attachment points have stainless plates riveted to stop the through bolt elongating the hole. I was a bit concerned about some signs of corrosion, so I have removed them (and the VHF bracket). You can see the end of the compression tube in the bolt hole. In this picture you can see I have taken off the mast head, which also came off very easily (note that I have replaced the very bad halyards with messenger lines). I will add an extra line for an internal topping lift rather than use the external block that is shackled on).

Here you can see the lowest shroud attachment. No stainless steel plate for this one as there is not enough space above the hole due to the spreader attachment. Looks like some corrosion where whatever was used as a barrier between the stainless steel and the aluminium has failed.

Top of the mast with the mast head removed.

Plans

We are going with mostly International Paints Products. So 2 part epoxy Interprotect Primer (grey) followed by 2 part Perfection Undercoat (white) and then Perfection gloss top coat (Mediterranean White).

Before the primer we need to prepare the surface. So sanding (I’ve ordered a special ScotchBrite pad – we need to be careful not to use anything metallic when doing the surface work as it could cause more galvanic corrosion), the cleaning with acetone before applying the primer ASAP (the aluminium oxidises really quickly which stops the primer adhering properly).

After the Primer we will use thickened epoxy to fill all the holes that are no longer needed and make good any areas where we had to sand away pitting.

We are aiming for 2 coats primer, then 1 coat undercoat and 2 coats top coat. We have ordered enough paint for the main mast as well. So we will get that prepared to the same point and sand, and paint with primer together (then the rush is a bit over).

Once the painting is done we have a few more things to fit and so I have been sourcing some of these.

  • new bolts, washers and more to attach the tangs for the dyneema shrouds. The imperial measurement bolts won’t be ready until 8th September which delays putting the mizzen mast up. It took ages to sort out and calculate the bolt lengths as it is affected by the angle the shrouds meet the mast.
  • new VHF/AIS aerial (probably from Digital Yacht as we will probably use their AIS devices)
  • new deck/cockpit light (probably on the spreaders rather than the front of the mast so they light up the area for reefing the mizzen).

I have been looking up how to install wiring in a mast and avoid them rattling as the boat rolls. Seems the best way is to install electrical conduit and rivet it to the inside front of the mast. Not sure yet about this.

I also want to sort our lazy jacks for the mizzen to control the sail better when we lower it.

I have bought a rivet gun and (very expensive) Monel rivets (they are an inert metal which means no galvanic corrosion). I have also order Duralac which is used to insulate stainless steel from the aluminium.

At this point I’m in two minds about putting the mizzen mast up. It will be very handy for sorting the fit of the dyneema shrouds/chainplates; the solar panels; the pushpit and later the hydrovane. However, one of the beauties of the way we are fitting the dyneema shrouds is how easy it is to remove them from the mast when it isn’t up. If we don’t have the mast up all winter the boat will be quieter and there will be no wear or UV dammage on the shrouds or chainplates.

Anyway it is now raining and expected to rain all day on Tuesday, so back to inside jobs in the morning.

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