google-site-verification: googleffe3ebaef4e4b443.html Oztayls-Restoring and sailing a vintage scow Moth: Mast rebuild

20 May 2013

Mast rebuild

After a final clean up with a wire brush on a drill to clean the last traces of old epoxy and to remove oxidation from the alloy sail track, I laid down a bed of epoxy on the mast and the track. While this was going off, I rigged up a “clamp” to hold the mast firmly so that it wouldn’t move while working on the mast.

A kettlebell proved to be very useful for keeping the mast in position. That’s the alloy sail track lying on the deck.


A bed of epoxy laid along the length of the mast. I did the same with the sail track.


The idea I had was to utilise the “wet on wet” ability of epoxy. By letting it go off a bit, the track would grip the mast and not slide off while it was being attached. This worked very well and there was just enough movement possible to allow fine adjustment of the track’s position. The other reason for letting the epoxy cure a bit was to ensure that the bed of epoxy forms a barrier between the carbon and the alloy. This is to prevent electrolysis which would eat away the alloy track, especially when a bit of salt water is added to the mix.

The track is attached. Packing tape clamps the track very effectively. It was important not to clamp too tightly as I didn’t want to push too much epoxy out of the joint.


While the epoxy was curing, I began adding the aramid fibre “stitching'”. Aramid fibres, (also known as Kevlar, Twaron or Nomex) are about 7 times stronger than steel. After impregnating the fibres with epoxy, I used a  twist tie wire to pull the thread through the holes in the track and then simply glue them down.

The next pic shows one of the aramid fibre ties. In this pic you can also see the slit cut in the track to prevent the track kinking when the mast bends. These slits are cut all the way along the track.


I then turned my attention to the joint between the carbon fibre tube and the alloy mast base. This was first wrapped with bidirectional glass tape. Subsequent layers were unidirectional carbon fibre as follows:

  1. bi-directional glass tape
  2. unidirectional carbon laid vertically
  3. unidirectional carbon laid horizontally
  4. unidirectional carbon laid vertically
  5. unidirectional carbon laid horizontally

This was then wrapped with gladwrap and bound tightly with packing tape to squeeze out excess epoxy resin. The result is a very strong joint. Al that remains now is to drill the hole for the boom gooseneck and give the mast a coat of polyurethane to provide UV protection for the epoxy.

Oh, I forgot. I do have to make a new 3-point stay spreader as the original one was corroded and cracked.

Mast (800x532)MastjointMastjoint2


At Monday, 20 May, 2013 , Blogger Alex Newman said...

Good clear description of the process: I especially like the wet-on-wet bit.


At Friday, 24 May, 2013 , Blogger George A said...

Hi: I just discovered your scow blogspot and have added it's URL to the "blogs I follow" list on my site. You may find interesting as I post about the Classic Moth Boat scene here in the USA.

Best regards,
George A.


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