We are having an early Christmas here with parts and supplies arriving often with many more to come. One of our recent additions is two 50 foot rolls of butyl tape, specially ordered off of the internet. What is butyl tape you ask? If you’ve been following this blog a while I’m sure you already know as we used it plenty to re-bed deck hardware and stop leaks.

But for those who haven’t and for the Chemist inside us all (especially you Dad) butyl tape is made from butyl rubber which from Wikipedia:

Butyl rubber is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for Isobutylene Isoprene Rubber. Polyisobutylene, also known as “PIB” or polyisobutene, (C4H8)n, is the homopolymer of isobutylene, or 2-methyl-1-propene, on which butyl rubber is based. Butyl rubber is produced by polymerization of about 98% of isobutylene with about 2% of isoprene.

Structurally, polyisobutylene resembles polypropylene, having two methyl groups substituted on every other carbon atom. Polyisobutylene is a colorless to light yellow viscoelastic material. It is generally odorless and tasteless, though it may exhibit a slight characteristic odor.

Butyl rubber has excellent impermeability, and the long polyisobutylene segments of its polymer chains give it good flex properties.  The formula for PIB is: -(-CH2-C(CH3)2-)n-

A synthetic rubber, or elastomer, butyl rubber is impermeable to air and used in many applications requiring an airtight rubber.

Polyisobutylene and butyl rubber are used in the manufacture of adhesives, agricultural chemicals, fiber optic compounds, ball bladders, caulks and sealants, cling film, electrical fluids, lubricants (2 cycle engine oil), paper and pulp, personal care products, pigment concentrates, for rubber and polymer modification, for protecting and sealing certain equipment for use in areas where chemical weapons are present, as a gasoline/diesel fuel additive, and even in chewing gum.

Interesting! Basically we use butyl tape mostly in place of caulk like 4200 for many applications where a water tight seal is needed because it works better, is easier to work it and is VERY long lasting (30 years good enough?).

Tate thinks I have a love for butyl tape and am passionate about capturing it in action shots. While somewhat melodramatic he may be right.  Tate introduced butyl tape to me before we even owned Sundowner.  We were fixing some leaks from the deck hardware on my mom’s sailboat when he suggested we use butyl tape.  Say what?

I call him Tatelopedia.  Wanna hear an in depth analysis of World History including religious and political forces at the time? He’s your guy.  Wanna know what spices to put in just about any dish, ask Tate.  Need to design a highly complex and dynamic working database? Call Tate.  Curious about how in the heck to stops leaks on a boat, yeah Tate’s the man. He is my walking encyclopedia. A really good thing to have onboard.

Believe it or not, all butyl tape is not created equal. There are different shades of white, grey and black. I’ve always read that on a boat grey butyl is the way to go. The black tape stains gel coat and topside paint while the white isn’t as flexible or sticky. Alright, grey it is.

I bought our very first roll of grey butyl from a local RV store. Notice this is not a Marine store so the cost was minimal at $14 for a 30 foot roll.  It was something like this.  We used it on my mom’s boat to rebed stanchions and cleats, and then on our boat when installing the engine panel,
engine panel butyl
and when rebedding the genoa tracks.
rebedding genoa track butyl tape
This butyl seemed pretty good, flexible, good adhesion and durability in the Louisiana sun. We’re talking over 100 degrees and close to 100% humidity All SUMMER!

Unfortunately I finally ran out of the RV store butyl while rebedding the genoa tracks so took to Amazon to order some more and found this stuff for only $5 a roll. WOW, what a great deal I thought and hearted the internet so much more that day. I ordered 2 rolls. With high hopes I finished rebedding the genoa tracks and temporarily sealed cracks in the caprail joints which took about 10 hours with this new cheaper butyl. The outcome wasn’t good.

Thanks goodness I’ve had the opportunity to see how different types of butyl tape hold up to the elements. In direct Louisiana sun I give you the 2 different butyl tape formulations after at least 6 months :
cracked caprail
with RV store butyl tape on similar crack
rv butyl tape
with cheap Amazon butyl
butyl tape cracked

The cheap Amazon Butyl shrank and separated along the joint in about 6 months, defeating the entire purpose. I suspect the direct sun caused the butyl to heat and shrink.  Half of the genoa tracks were also rebedded using the cheap stuff but I’m hopeful it won’t shrink as drastically since it isn’t in direct sun.  The RV store butyl used on a similar caprail crack in the second photo has held up for almost 2 years now with no cracking.

Please note this is just a temporary fix for the cracks in the caprails.  We think they let water in the boat when it rains and needed something quick, easy to remove and durable to keep the water out until we have a chance to properly seal these cracks.

Tate noticed right off the bat the cheap Amazon butyl wasn’t the same as from the RV store. He suggested we trash the remainder and instead order some high quality grey butyl tape from Compass Marine Services. The price is about $16/roll plus shipping for 50 feet of grey butyl tape.

We received our 2 rolls the other day and I have to say this stuff is the real deal. It is FAR more stickier than either of the previous two butyl tape varieties and I am impressed. I had trouble today removing the new butyl from a ziplock bag because the end of the tape was STUCK on the plastic. Seriously I couldn’t get it off. I pulled slowly to see how far it would strecth and well…
stretched butyl tape
Geesh. The cheap stuff from Amazon peeled right off not stretching a bit
poor butyl tape
Here they are side by side. They are both grey, but the new stuff is obviously a darker grey.
grey white butyl
To review, this is cheap amazon butyl over a caprail crack
butyl tape cracked
and this is the same crack sealed with the new stuff using about half the quantity of the cheap
new butyl tape
I feel REALLY good about this stuff!!

Tell me again why science isn’t taught aboard boats?