Caswell Tank Coating

I won’t duplicate what you can find elsewhere on the web about the use of epoxy fuel tank liners  – please see my previous post (here) or the GT750 project site for some links to several good sources of information, but I must say that I smiled to myself when I was mixing in the catalyst as all I could think about was my previous experience with two part resin/catalyst experiments in the Sandy household. When I was a teenager, my brother and I helped my Dad fibreglass a sail boat we were building in the basement of our house in Ontario – as we laid down the mixed resin and glass mats, invariably we would run out of time and the mixture would start to set, the container it was in would get too hot to hold, the smell was incredible (as I think back on it, I’m sure we were all higher than kites on the fumes) and my Dad would be rushing around at the last moment trying to apply rapidly solidifying gel that was turning into solid plastic so fast you had to be careful your hands didn’t become permanent deck fixtures ! I have to report that my Caswell experience was not nearly as exciting, so just a very few comments:tank

  • The GT750 tank has several ridges on its underside that are difficult to get well coated inside the tank. You can see them in the photo to the right running left to right in the area of the tank  that would sit immediately above the frame. I used a small brush, and tried to coat what I could reach as best I could through the filler opening, but I suspect this was not entirely successful
  • My tank had been steam cleaned, but I still followed the instructions that came with the Caswell kit, and rinsed out the inside of the tank with water, ensured it was well, dried (I used an old vacuum cleaner that has a blower option, so I had a good stream of warm air blowing inside the tank),  then rinsed it again with lacquer thinners and a handful of screws (to knock loose any rust flakes etc.) and again made sure it was well dried
  • I made a small plate from scrap metal to fit the fuel petcock opening and used some old inner tube as a gasket – it worked fine. For the fuel filler opening, I just used an old filler cap and some Saran wrap (called cling wrap or Glad wrap in other countries) – the instructions say to use Saran wrap held in place with elastics, but the filler neck design doesn’t lend itself to doing this as you can’t easily make the elastics stay on
  • You can’t easily drain either cleaning solvent or excess epoxy from the tank – and getting all the screws out took a while. The fuel filler opening has a sleeve on the inside of the tank making drainage via the filler opening impossible, and as the bottom of the tank is pretty well flat on both sides of the centre of the tank where is it raised to clear the frame (you can see this clearly in the previously mentioned photo to the right), getting good drainage via the small  fuel petcock opening is not really easy either.
  • The Caswell tank  sealer seems to be quite temperature sensitive, and you do need to have a relatively warm work area, other wise the mixture is too viscous and doesn’t  flow well on the inside of the tank. I ended up doing two applications, as I was not happy with the first attempt – each kit provides enough material to do one application to two tanks, or two applications to the same tank. After the first application, when I checked what little I could see of the inside of the tank with a mirror and a strong light, there were clearly several areas that had not been covered at all. My first application was at about 20C and so for my second attempt, I made sure everything was a toasty 24C, and the mixture was noticeably thinner and spread much more readily inside the tank – without a scope, it is impossible to tell if the inside of the tank really is fully coated, but at least the little bit that I can see does now look pretty good.
  • There was no odour at all – doing this process inside the house would not be a problem
  • You have lots of time – the mixture does not start to set for about 40 to 60 minutes, so there was no frantic rushing around required ! And once it does start to set, there is a long ‘rubbery’ period that gives you time to clean out any openings or threads if you want to – and I also noted that lacquer thinners will remove any spillage or smears from the outside of the tank if that should be required, and if you are careful and perhaps a bit lucky, it will not damage the paint.
  • it would be nice if the mixture was tinted, as it would make it easier to see whether you have got good coverage, plus as the mixture is transparent what I can see now inside the tank is epoxied rusty metal. If I were to do this again, I would try to find a suitable colour tint to make the finished tank look a bit more professional.

Bottom line – from what I can see, I do now have a good coating of epoxy on the areas of the inside of the tank, so I’m finally ready to start painting !

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