A note! I was passed a message from a builder that saw some bullshit on a forum that said everyone knows about this and wonders why I made the big effort to answer the question... utter rot. Be careful as the forums are seeded with partisans... with undisclosed interests to protect.

Builders who have ordered duflex and received the lovely pamphlet that comes with the stuff with explicate instructions and how too's will note that the word "outgas" is not found in their literature. A phone call made to ATL asking about this important question was not responded to. Why?? And I know for fact there are many boats out there made of duflex that have hundreds or thousands of pits filled with car finishing putty because that's all they knew. When I asked the wattel paint rep about this problem, that's what he came up with too. They all think the pits are just in the bogg but it's not nessearily so, they often penetrate to the balsa core. There are a lot of people out there trying hard to hide the faults this stuff has. If I had known, there is no way I would have spent the money when going foam would have been so much less expensive and more reliable.

The short answer is YES. At least the set of panels I have show that Duflex panels can outgas from the core readily.

As I mentioned in the previous installment, Bogged Down in Assumptions, I had asked builders if they had problems with outgassing and some said no and one said yes but he figured it was air trapped in the weave rather than from the core that was outgassing. So, now I know I was asking the wrong question. Going back and getting more information I have learned that before this article was published, many professional builders did not know what the cause is of the pits and holes that often occur in the bogg applied over the Duflex. Not that pits can't occur in the Bogg otherwise but if my hulls are any indication, the vast majority are from outgassing. In the article linked above, I noted that a large section of bogg that I did at night was absolutely pit free. This was further evidensed by more sanding done since the article linked above was written and still... not one detectable hole or pit whereas all bogg I've done before or since (that was all done during daytime, warmer hours) has pits.... lots of them!

So what does it all mean? Every one of those pits from outgassing is a path from the water to the balsa core and all that is preventing ingress of water is the means of sealing those holes/pits. Puty? Paint? Resin coat? Keeping in mind that if the resin coat is applied during warmer hours, it too will be subject to gassing. Will this be a problem some day for boats built without taking this all into account? It could be. Even if a seal is obtained on the surface with the means listed above, all it would take would be a scratch under the water line (rock, floating debris etc) to reveal a pathway into the core.

 then pressed the jar in place to form it all to smooth. I then let set and later cut away the excess plastic inside the circle.

This is when I noticed how poor the visibility was through the jar and cleaned that up before the fianl experiment.

 I felt that the cause of the permeability was the lack of resin in the fibreglass cloth. Besides the finishing work required because of the rough surface, could it be that the shortage of resin was an actual mechanical shortcoming?

Another scrap of similar type to the one tested, this one I will coat with resin and try the same test with it.

 This shot, 7:38 AM.

The Vacume test is really superfluous at this point but might as well continue for the sake of entertainment! The arrow indicates the position of the red water mark. I have to hold down the jar because the panel has swollen and warped from the absorbsion of water in the balsa.

Conclusion? Spreading resin over panels that have been delivered impoverished of resin from the factory benefits the panels as far as I can tell. Because of the trapped air in the lean panel resin, I would suggest the best result would have been to have the panels fully resined in the beginning., but doing them up post delivery is better than nothing. If I had it to do over again, I would deffinately have spent a few days and a few hundred $$ worth of resin to be able to do it on a flat, horizontal surface.

Since doing this experiment I have ground off a lot of previous work on my first hull to expose panel surface that I will cover with a thin bogg, resin mix (will only be using bogg in the mix to help keep the mix from sagging out of the weave where the surface is verticle) to try to fill as much as I can below or near the water line. Then start over with the bogg. This will all be done in evening hours of course.

If you have Duflex panels and are curious about this aspect of them, you don't need the vacume pump and bell jar. Simply using the tray and coloured water will indicate if you have reason for concern. Just cut off one side of the glass on any reasonable size piece of scrap and watch for an hour.

Not all Duflex panels from ATL composits have this resin shortage issue that I attribute to this kind of permeability problem. My 19mm panels were filled beautifully. Again.. see the "assumptions" article, microscope shots. Heat used in the manufactoring to speed curing may have a part to play in this problem as well.

Having resin rich panels will make them heavier but the resin you have to install after the fact puts any weight saved right back on.