A few years ago when I added a new fuel tank on my boat (http://sailingit.com/blog/boat-projects/fuel-system-part-1) I took Maine Sail's suggestion and used Weld Mount epoxy bonded studs to bolt the tank to the hull. The tank holds 9 gallons, so fully loaded the static weight of the tank+fuel is under 60lbs. The advertised strength of the studs is described as "a structural part with 500 Lbs. of tensile strength and 650 Lbs. in shear. Torque load is 90 inch/Lbs". I attached the fuel tank to the hull using 8 of the studs, which from a purely strength perspective is overkill by about 7 studs, with the thought process being that even if half of them somehow failed, the tank should always remain safe and secure so I will never have to worry about the chance that tank comes loose (you can probably guess where this is going by now).
Wednesday night I was moving / motor sailing the boat down the coast in some rough seas (18-25kts on the bow for 4 hours), the boat seemed to take it pretty well... Yesterday I was cleaning the boat and filling the fresh water tank and saw, much to my horror, that the fuel tank had completely came loose! All 8 of the studs rated at 500lbs+ had failed at their epoxy bond. The epoxy was still perfectly adhered to the fiberglass substrate in little cup shapes representing where the metal studs used to reside!
I just called Weld Mount and spoke with someone there about the failure and he said that is nearly unheard of for a failure mode like that, saying that it was most likely either a bad batch of epoxy adhesive (they haven't had significant issues reported), or that the tube of epoxy hadn't been properly refrigerated while in storage at the distributor (I purchased it from Jamestown). To be sure I described the installation procedure I used and he confirmed that there was nothing at all I could have done better than how I did it, having exactly followed the recommended procedure to a T.
They are shipping me (for free) a new tube of higher strength epoxy as well as new studs to re-do the whole installation with.
If you purchased Weld Mount AT-2010 epoxy from Jamestown (or elsewhere) around Feb/March/Apr of 2013 you should be very concerned with the strength of the bond, the studs may not be bonded anywhere near as strong as you think they are! The good news is that their customer service seems very ready and willing to make things right, and may even come down to the boat (the guy I spoke with lives roughly an hour away) to see the failure for himself. I would suggest going and putting some load on any of the studs (maybe smack them with a small mallet) and seeing if they fail, it's better to have them fail at the dock than at sea!
Luckily for me the failure did not cause any fuel leaks and the placement of the tank is such that it is unable to move about too freely, but this story could have so very easily ended tragically different had the nearly full tank ruptured or ripped off the filler hose and spilled 7-8 gallons of gasoline into the boat where it could have possibly found an ignition source...
Wednesday night I was moving / motor sailing the boat down the coast in some rough seas (18-25kts on the bow for 4 hours), the boat seemed to take it pretty well... Yesterday I was cleaning the boat and filling the fresh water tank and saw, much to my horror, that the fuel tank had completely came loose! All 8 of the studs rated at 500lbs+ had failed at their epoxy bond. The epoxy was still perfectly adhered to the fiberglass substrate in little cup shapes representing where the metal studs used to reside!
I just called Weld Mount and spoke with someone there about the failure and he said that is nearly unheard of for a failure mode like that, saying that it was most likely either a bad batch of epoxy adhesive (they haven't had significant issues reported), or that the tube of epoxy hadn't been properly refrigerated while in storage at the distributor (I purchased it from Jamestown). To be sure I described the installation procedure I used and he confirmed that there was nothing at all I could have done better than how I did it, having exactly followed the recommended procedure to a T.
They are shipping me (for free) a new tube of higher strength epoxy as well as new studs to re-do the whole installation with.
If you purchased Weld Mount AT-2010 epoxy from Jamestown (or elsewhere) around Feb/March/Apr of 2013 you should be very concerned with the strength of the bond, the studs may not be bonded anywhere near as strong as you think they are! The good news is that their customer service seems very ready and willing to make things right, and may even come down to the boat (the guy I spoke with lives roughly an hour away) to see the failure for himself. I would suggest going and putting some load on any of the studs (maybe smack them with a small mallet) and seeing if they fail, it's better to have them fail at the dock than at sea!
Luckily for me the failure did not cause any fuel leaks and the placement of the tank is such that it is unable to move about too freely, but this story could have so very easily ended tragically different had the nearly full tank ruptured or ripped off the filler hose and spilled 7-8 gallons of gasoline into the boat where it could have possibly found an ignition source...
