Kurt,

I just erased my complete message. Hopefully I can repeat it sensibly. Given the erase I did I have some doubts in my capability.

I will never thin my epoxy for the following reasons.
1. Every time I have tested a glued joint of coating by breaking it (West and System 3) it has always broken in the wood. This means I am getting as much strength out of the epoxy as I paid for.
2. Every test based report I have read shows that the strength of the epoxy is reduced. Why would I want to do that?
3. The total strength of the external coatings depends upon the first layer. You will see cars where the primer has failed, cracking thru the topcoat and causing pealing. In Aerospace we have had significant and costly problems where the primer was poorly applied or the original surface was not properly prepared.
4. No one has ever demonstrated that greater "penetration" exists or enhances the strength of the total coating. In fact #2 above suggests it is not possible to get greater strength overall. Has anyone ever seen a photo-micrograph of the difference in "penetration"? The Gougeons long ago tried to say that the epoxy does not penetrate uncut wood cells. It only penetrates the cut cells in the very outside layer of the wood. Of course it will penetrate flaws, cracks etcetra which great results. The whole idea of "penetration" has been exaggerated and oversold.
5. Gougeons very carefully explained that their epoxy is 100% solids - no solvents. The point was that solvent evaporate away during the cure, leaving small micro passages, which can allow penetration by water vapor - leading to moisture in the wood, leading to the conditions which allow rot. You could say that subsequent layers would be full strength (no solvents) but why would you ever degrade the coating?

I do have a friend who uses thinned epoxy on RC aircraft. In his case the balsa wood is seriously lower strength that even Cedar, so the full strength can never be used in that situation. Also he crashes the models long before any wood rot could ever develop, so he just doesn't need full strength.

Last, I find that I get significantly easier and more consistent application of West (slow hardener) when it is above 100 degree F in the garage. My suggestion is to use a heating pad under the hardener and resin if you have to work in less beneficial temperatures - I.WE., 90+ or below. An unfortunate consequence of not working in the Texas summer. :)
FYI - the epoxy does not seem to kick off significantly faster when it is 100 degrees - non nonsensical be I don't have any problem.

ET would skin me for such verbal diarrhea.

Marc