mattthomas4444 said:
Carbonfibre said:
If you are an experienced laminator then separating a tank and bonding it back together is certainly a realistic option, but if not then this isnt a simple job as suggested on here, and may well result in a scrap tank!
Carbonfibre,
Thanks, judging by your name, I think i will take your advice, however I really would like to do it myself, im trying to save as much money as possible, and getting someone else to do it would probably cost the same as a new steel tank. As far as the novalac epoxy goes, i searched it a bit, and found many different types, is there a specific type that you recommend? Also, what types of GRP should i use, sheets of it or actual individual fibers? Should i use a mat (Chopped Strand Mat) of GRP, then follow with "woven cloth" or "glass fiber tissue" to add a smooth finish? Also, should i sand in between layers, or leave it? Finally, what should i do for prep work, I dont quite know what crushed glass would do. Sorry for all the questions, I am not too familiar with F/G.
Thanks a bunch,
Matt
Unfortunately the content of this thread provides a very good example of the seeming lack of understanding of the problems likely to be faced by anyone using alcohol bearing fuels in old type GRP tanks, and how to overcome them!
I will provide some accurate guidelines here, and some points on resin selection which are supported by manufacturers chemical resistance data:
1) VE resins: Vinyl ester resins are more chemically resistant than common polyester types, but novalac VE materials which are after specified post cure fully resistant to alcohol fuels, are not easily available in small quantity's as shelf life is limited, and suppliers are not willing to throw un sold product away .
2) Sealing a complete tank: Secondary bonds between dissimilar materials should be avoided if at all possible, but reasonable results can be achieved using crushed plate glass, to mechanically abrade the interior surfaces, and subsequent application of a low viscosity novalac epoxy, with chopped GRP fibres added to increase film strength when cured.
3) Epoxy resins: Commonly available bisphenol A epoxy resins have a higher level of chemical resistance than polyesters, but are not recommended for use which involves long term exposure to alcohol bearing fuels.
4) Cutting open tanks: If tanks are to be sectioned to add chemical resistance layer, ideally the interior surfaces need to be blast cleaned using a relatively gentle media, scoured with acetone, and chemical resistance layer applied to all interior surfaces in the form of one layer of 100 gsm csm, followed by synthetic veil resin rich layer, all laminated using a novalac epoxy resin. The sections ideally must then be bonded together within the time period available to achieve primary bonding. Finally the bonding line then needs to be sealed completely through the introduction of a small quantity of thinned novalac epoxy, and the tank manipulated to ensure bonding area is fully coated.
5) Problem areas: If tanks are damaged to the extent that alcohol has permeated and softened the lay up, then damaged areas need to be mechanically removed, and properly repaired using novalac epoxy and powder bound csm. Secondary bonds rely entirely on mechanical adhesion, and proper preparation work is crucially important. Use of unmodified tank sealing products in relation to GRP tanks is unwise, as the brittle nature of cured thin film slosh coatings, linked to vibration means that cracking is almost inevitable.
6) Due to difficulty related to sourcing the correct materials its possible that some GRP tanks being produced currently are not likely to be able to resist alcohol bearing fuels long term, so before contemplating purchase of any recently made GRP tank, buyers need to assure themselves that a written guarantee of at least a year is supplied with the tank being considered.
) just to make sure I go about it correctly. Maybe the type of fiberglass to use? Should I apply new F/G to the whole tank or just the seam where I cut? maybe the type of resin to use? What's the best type of sealant to use? if I apply it when the tanks cut open do I have more options? (a brush on type?)
