Join Date: Sep 2008
Location: Victoria B.C. Canada
Thanked 101 Times in 92 Posts
Rep Power: 9
Re: Bedding Deck Hardware With Butyl Tape
Spacers are not necessary. The butyl will stop flowing after a short while. Ultimately the hardware item will be very close to the deck and that is the reason that the fastener holes are chamfered (countersunk). This gives an "O" ring of sealant around the fastener. For a given amount of movement the thicker the sealant the more movement is allowed before the seal breaks. When the hardware moves under strain, and it will slightly, the sealant used must allow enough stretch without the seal being broken. Butyl excels at this, more so than any other sealant, which will harden over time and lose its elasticity. My CS27, like Maine's CS36T, was built with butyl under all deck hardware and there are no issues 30+ years later - including the hull/deck joint.
Living aboard in Victoria Harbour