Re: Reapply gelcoat to hull?
Hey YD and ondarvr, thanks for weighing in on this; I believe you both bring up good points regarding the duratec product. I can tell that this is a bit of a hot topic in this forum and I would like to comment a little further. Although the manufacturer states that a 1:1 ratio works well (and in most cases it does) it does have it's limitations. Because it is essentially thinning out the pigment levels it does make it more transparent on skim coats. I personally only recommend this ratio when working with whites and creams as you're starting out with a white base which has a high pigment level to begin with. When working with dark colors (reds, blues, greens, etc) the starting base is neutral (essentially clear and un-pigmented) and by nature is more transparent than a white base of the same thickness. This is why gel repairs on dark colors can be much more difficult, as more often than not there is slight blotchy-ness throughout the hull from the manufacturer (as the gel layer gets thinner it becomes a lighter shade). As far as this level of transparency when mixed with whites requiring excessive buildup to achieve coverage I haven't run into this. Playing devil's advocate a bit, A highly pigmented gelcoat can achieve complete coverage with thin coats (often coats that are too thin to fully cure) and that itself can cause issues with color, gloss and waterproofing degradation. Personally I've found that when using the Duratec 1:1 mix (with whites) although it does require a little more layup compared to an un-thinned mix, by the time you have complete coverage over the repair you also have a proper level of buildup for a complete cure.
As far as a loss of UV protection from using this product I guess I can't definitively say one way or the other; what I can comment on is that I have not had an issue with fading or bleaching or yellowing of a repair even after a few years of direct sun exposure (at least in our region where the boats are in the water and sun 6 months of the year and covered in snow the other 6 months; it very well could be an issue in southern areas that get hit year'round). One further thought I do have on the UV issue is that what it may lose in protection from displaced pigments it may make up for it with a higher gloss and a less porous surface. Much like varnish, a mirror finish is able to reflect the UV rather than absorb; this is a bit of speculation on my part.
In reality, a book could be written on all the nuances, trade-off's and considerations that need to be taken into consideration when working with gelcoat. By no means do I claim to know ALL there is to know about the topic, but I have had quite a bit of experience and trial and error experiments with the stuff. A professional should be aware of these things (and the good ones are; there is no doubt that the above post'ers are experts on the topic and truly know their stuff!) ** However, for the sake of someone trying to learn the tricks of the trade as they are doing the repairs themselves (often for the first time) I still stand by my recommendation for the Duratec product. Yes, like ondarvr said there are trade off's, however in my humble opinion I believe that more often than not this is an acceptable one. It makes application easy(er) and the finishing process faster with less room for error during the curing process (this is a big consideration in my opinion); while still providing excellent durability and finish.
By no means am I saying that anyone is right or wrong in their opinions on this, everything that has been mentioned in this post is accurate. I just happen to be one of the people that leans towards the benefits of Duratec outweighing the drawbacks (most of the time).
This is one of the reasons I have really grown to appreciate this forum; anytime there is a group of people that is knowledgeable in their field offering advice and experience to people wanting to learn (although at times there may be some slight differences in opinions) it works out for the betterment of the community! Thanks Guys!
http://forums.iboats.com/showthread.php?t=465692
