Originally Posted by scottthardin
My 7.5 year old boat has been sailed a lot and I am now entering a period where numerous leaks
are appearing. I had a bit of an urgent situation where I used butyl tape and ss fasteners to bed portlight covers in a way that made sense given that I might change the cover material out in the near future. A friend mentioned that butyl tape could work well for all rebedding issues where fasteners are involved such as stanchions, genoa
car tracks, and the ss bases where my shrouds enter the boat and are subsequently attached to chainplate bars.
Have others used butyl tape extensively for above-the-water-line bedding efforts? I always thought marine
grade silicon was what one used for such situations but my friend thinks butyl tape will give me longer life and easier serviceability. What do others think?
As is the case with everything, use the correct material for the application.
Properties: Excellent gasket under compression
, very elastic, terrible adhesive
, easy to spread, excellent UV resistance, 24 hour cure, faster formulations available, 20 year life expectancy (if bond doesn't fail). Clean-up with vinegar.
Pros: Beads and spreads easily. Skins quickly.
Cons: Poor sealant/material bond.
Unpaintable, wreaks havoc to any surface that will ever need to be painted.
Great for mounting Beckson ports
and trim rings in fibreglass. (The only sealant
that will not void their warranty.)
ports in metal frames.
Poor choice for most deck fitting applications. Likely most misapplied product.
Excellent gasket, elasticity - excellent elongation / poor spring, poor adhesive
, difficult to spread, medium UV resistance, never cures.
Pros: Properties remain consistent for product life.
Cons: Exposed material picks up dirt for life. Can be "worked out" of a joint that has constant movement. Smears onto anything that comes in contact for life.
Not for use where a bond is required to hold parts
Great for bedding deck fittings that are "firmly" mechanically fastened by other means and don't rely on material for adhesion.
Poor for use in joints that my work, or where objects may come in regular contact with material.
3M 4200 (or 4000 UV):
Excellent gasket, good elasticity, good adhesive, good bead and spread, poor UV resistance.
Pros: Much stronger material / adhesive bond than silicone sealant.
Cons: Even 4000 UV will only last a few years in high UV areas before breaking down.
Applications: OK for deck fittings, except for UV issues.
Excellent gasket, excellent elasticity, excellent adhesive, good bead and spread, poor UV resistance.
Pros: Tenacious material / adhesive bond.
Cons: Difficulty breaking bond. Usually requires being cut apart. (Heat makes removal
much easier if parts
Applications: Excellent for hull
deck seams and bonding/sealing deck fittings.
Personal Note: 3M 5200 often gets a bad wrap on internet forums
for 2 reasons:
Reason 1: It does what it does so well. Some cite difficulty removing components adhered with it. IMHO, it is an excellent deck fitting bedding material for this exact reason, who wants a deck fitting bond to come apart unintentionally?. It has a tenacious bond which is not likely to break (and leak) for the life of the boat. In the "unusual" event that one needs to remove a stanchion base (or similar) just heat it up and push a putty knife under it. Takes 60 seconds.
Reason 2: Many people tighten fasteners excessively, leaving insufficient material thickness in joint.
Instead, fasteners should only be finger tightened until material oozes through join, but leaving at least 1/16" material between parts.
After 5200 cures DO NOT TIGHTEN FASTENERS.
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