There are vast differences in butyl tape. Some you buy on the net is not even butyl at all but rather a water soluble putty tape. I have had three or four customer send me a rolls they bought advertised as "butyl" that melted in water. I have no idea what it is but it is not butyl. It rips instead of stretches and melts in water..not good.
One guy even emailed me a video which I will try and find.
If you buy a roll that is not from me at least buy a genuine glazing butyl. It has to meet some minimum glazing industry standards and the RV or roofing stuff does not. While not the same as the stuff the boat builders used to use it will be far better than many of the cheap RV tapes or roofing tapes of unknown origin or make up. RV advertised butyl it is often of poor quality and can continue to "bleed" and is also often not even butyl. These are usually high solvent tapes made to be messy gummy stuff for jamming in roof cracks on RV's. You really can't buy this stuff based on price alone, as I found out.
I buy direct from the manufacturer in multi-pallet skids and pay more for the good stuff than re-sellers four times removed from the manufacturer are selling the cheap stuff for.
I spent six months evaluating butyl tape before I found one that met standards I felt were suitable and comparable to the older stuff the builders used to use. With EPA regs changing all the time this was difficult. Not too wet or solventy, enough durometer/harness, but not too much, and very, very stretchy & flexible an a wide working temp range. When I found it the only problem was that it was not made in gray, only black. Black can be very, messy, trust me my prots lights were bedded with NFM's black stuff and it is horrible....
The big problem with RV tapes is that the quality is all over the map and I found after putting them side by side it is kind of like going to Vegas. This is what forced me into sourcing some known quality stuff for the boating community.
Much of the RV stuff I found is now produced offshore and the quality and consistency was all over the place, a real crap shoot. Tracking back the manufacturers led me to some interesting finds. Some of the stuff you are buying the manufacturer is selling for $0.45 - $0.65 roll and uses "fillers" to get the price down as purer butyl rubber is absolutely not cheap.. Some is really wet/solventy, some is really soft with little density, some lacks the elasticity and some failed my cold weather testing. I ordered about 16-20 different rolls / brands of RV tape and about half was absolutely unacceptable and the other half could possibly work ok for a while but was still not as good as a quality glazing tape.
Some of it stretched less than an inch in sub 20 degree weather and some went 6 inches but none stretched as long or as far as the best performing stuff or stuck to parts as well. One roll I had, of "unknown" quality, got hard and brittle just sitting in my barn. I have a roll of quality tape I bought in 1998 that I show customers who pick up at my house.. Still not much different than it was in 1998 other than sticking to the backing paper a little more. One roll I ordered of eBay was foam rubber not butyl this despite the picture and description on ebay describing it as butyl tape.
While you can certainly get lucky I found that after buying over 40 different rolls/brands only about four or five were products I would be willing to use on a regular basis. That is a pretty dismal ratio and less good than simply going to Vegas.. Just like Polyurethane sealants such as 4200, 5200, Sikaflex etc., of which there are hundreds of "brands", people use the good ones in the marine environment because they work well and are time tested and proven.
Also butyl is only another tool in the shed for bedding and all the other products still have a place and, I still use them depending upon the situation.
All that said I have a friend who bought some pretty poor quality butyl and its been three years and it is still not leaking, so the prep counts for a lot. I honestly would not have given this stuff three weeks. He's going to rebed it once it leaks so now we are curious to see how long it lasts..
Bottom line is if I have to put my name on it it's going to be good stuff....
These are a few pics of from guys who bought RV stuff on-line and later bought the stuff I now sell.
On-Line RV tape sold as "butyl rubber tape":
Bed-It Tape:
I know the tape on our 33 year old CS is still preventing leaks, over 80% of the boat is un-rebedded, and this is the closest product I could find that that.
If you're happy with what you have and it works then stick with it. I just can't really say how long it may last as the qualities of "butyl tape" are all over the map.....
