Mast Partner Repairs and Installing Mast Collar

The voids at the mast partners, visible from below decks, required filling prior installing the new mast collar backing plate.  The largest void starboard and aft side of the deck opening was large enough to require a piece of 1/4” plywood as filler.

cutting plywood biscuit to fill void at mast partners.

The other voids were small enough to allow the repair to be completed with thickened epoxy.   

I planned to fill the voids then clamp the new backing plate in place while the epoxy cured.  The backing plate will ensure the epoxy fully fills the voids and prevent the epoxy from sagging while curing.  

However we did not want the backing plate permanently adhered to the cabin top.

Using duct tape as release agent on new backing plate.

Epoxy will not bond to either face of duct tape.  Covering the top surface of the backing plate with duct tape allowed us to use it for clamping the repair in place.

Using new backing plate to hold repair in place during curing.

Curing epoxy generates heat - the curing process is an exothermic reaction.  Too much heat and the epoxy cures (“kicks”) quickly and creates a weak bond.  In extreme circumstances the curing process can generate enough heat to start a fire.  What causes excessive heat?

A greater volume of epoxy – filling a large area = increase in heat

The more dense the epoxy – adding a thickening agent  = increase in heat

Insulating the epoxy – clamping it between the deck and backing plate  = increase in heat

Hot sunny conditions - July day in eastern NC = increase in heat.

We were concerned about the epoxy kicking too quickly.  Using West Systems tropical hardening catalyst served to slow down the reaction.  We also used every trick in the book to cool the deck above the repair.

Attempting slow down the curing with shade, ice, and a fan.

We shaded the area, placed bottles of frozen drinking water on the deck, and used a box fan to circulate fresh air across the surface.

Voids at mast partners filled with epoxy and plywood biscuit on right. 

Success – the epoxy cured properly and the backing plate released easily.

Anne came up the the wonderful idea of using a screen tool for applying butyl-tape 

Anne used a screen tool to roll a bead of butyl-tape into the gasket channel on the mast collar.  The butyl tape will create a water tight seal between the deck and the collar.

Working as a team, Anne topsides, and myself in the cabin...

Teamwork.

we bedded the thru-bolts and stainless rod with UV resistant 3m 4000 sealant.

New mast collar backing plate installed.

And, yes somewhere along the way we added a couple coats of white paint.

Additional images and notes from this project can be found in the Mast Partner Repairs Photo Album