milk money

[peter anderson]

hi all,
having a problem with the epoxy laminate on my cedar strip outrigger. last year took it back to bare timber, west system epoxy/fibreglass with 2-pack PU as finish. looked great until the weather warmed up,(30+ degrees) then a milky stain began to appear in the epoxy layer. any suggestions to remedy as I'm dreading having to sand it all off & start again- the canoe is 45' long x 60" around the hull at centre!

 

[sandpiper]

Good morning Peter. After reading your topic, I got out my book on West System. I went to the trouble shooting chapter. Here is the result: Clear coating turned cloudy. Possible causes: Moisture from condensation or very humid conditions reacts with amines in uncured hardener. It could also be: Entrapped air from aggressive roller application. In the solution they talk about do the job again using hardener 207.Use 205 or 206 only in dry conditions. Apply epoxy in thin coats. Looks like you might not have the choice. "Play it again Sam"!! Maybe an other member has a better idea. Best of luck to you. Sandpiper from Canada

 

[peter anderson]

thanks for your reply. The milky effect is in the actual laminate, & does not appear to be amine blush. it started to appear after a spell of hot weather; has been slowly spreading over the canoe. the filler (epoxy) coat seems ok & the 2-pack clear is standing up fine, retaining gloss 12 mths later despite the canoe being stored outside 365 days / year. the canoe was stripped back to bare timber & dried out inside my old factory for a month prior to glassing, so in theory it should have been fine. before laminating I brushed a sealer coat over the canoe, washed & lightly sanded before glassing. mixes were done in 1 kilo lots, so it's not that a particular brew was not mixed properly, as the effect is all over the canoe. weather at the time was dry, av.26 degrees. the only thing I can think is that there may be moisture coming through from the inside of the canoe- however the floor is laminated 30" wide on the floor/sides, which would seal it completely inside in that area at least.the canoe is planked with 40x12mm strips, epoxy glued in the seams, so there can't be moisture migration across individual strips. the milky patches seem to be random & as pointed out earlier slowly spreading. 206 hardener was used throughout. it doesn't appear any worse in the bow & stern where there are enclosed buoyancy tanks which would tend to be very humid inside. through the racing season it is kept upright & usually has a little bit of salt water puddled in part of the hull. (drain plug in centre)
keep my fingers crossed this year & gird my loins for the Big Sand next off-season!

 

[Todd Bradshaw]

Can you see a faint weave pattern if you look very closely at the milky areas? I've seen strippers which were overheated and developed big milky-looking areas where the wood core expanded from the heat and the fiberglass laminate literally got stretched (which fiberglass doesn't do very well). Structurally, they were still within reasonable tolerances, since only part of the many small strands fractured, but there was no way to blend the milky look back in.

U.V. damage generally turns WEST epoxy yellow and rubbery, so that's probably not the cause. Epoxy isn't quite as waterproof as many people believe, so it might be possible for heat to drive moisture out of the wood and into the resin, but I don't remember hearing of such a case. Gougeon Brothers tech people are very good and quite helpful. It might be worth a phone call to see what they think. If it was my boat, I'd paint it before ever seriously thinking about sanding the glass off. Unless you're EXTREMELY good with a disk sander it's a very difficult job as well as very unpleasant. A milisecond after the sander cuts through the last of the glass layer, it cuts a big dished dent in the soft cedar underneath. Once you're done, you have to fair out the whole hull to get rid of all the lumps and then paint it to cover the fairing compound. You would be better off using a heat gun and scraper to get the glass off and then sanding the last of the goo off. With epoxy, that's also a tremendous amount of tedious work, but you would have fewer dents.

 

[peter anderson]

thanks for your input.definitely not from the glass being "stretched"- i've been using epoxy for 25 years & never struck this problem before.
as i spend a large part of each working day swinging a disc sander over surfboards i'm sure i could take it back to timber (VERY carefully!) without chewing up the canoe but as you say it's a dirty job & i really don't want to do it. meantime the 2-pack is holding up well so i'll probably just recoat & pretend i can't see the white bits.
regards,
peter