You got my curiosity going to the point that I had to get up and go downstairs to my shop to look at the Divinicell I have in my possession, to see if these claims of a "rough surface" have any merit. After using boxes and boxes of 1-1/2" H130, ¾” H100, ¾” & ¼” H80, ¾” H60, and ¾” H45 I have to ask if we are talking about the same Divinicell? Are you dealing with seconds? I have never seen density variances of 25% on any of their products...
Looking at the fine cell structure of H80 in front of me it would seem that attempting to "fill the open cells" with bog prior to glassing may be something that makes sense academically, but does it translate to any appreciable weight savings in actual construction?
After bogging you have to go back and impregnate the cloth using enough resin to get a complete bond to the bogged surface...and your resin system better have a very long pot life if you have aspirations of bogging the entire hull surface and then laminating the cloth while the bog is still wet. 1) Who is this technical engineer for Divinicell that made this claim and where on their web site can this information be verified? 2) What is the ratio of resin to glass bubbles/micro balloons that is being used? 3) If it takes 300 grams of pure resin to fill in the cut cells of a sq/meter of material how many grams of bog does it take to fill in the cut cells? What is the resulting proposed saving of weight? 4) Does the 300 grams /per/sq/m consider only one side of the foam or both the front and back surfaces of a sandwich? 5) Is this something that only works at the desk with a calculator? Or will it be reproducible in the work shop? 6) Will a carefully prepared small test panel (even up to a full sq/meter) give you an accurate sample, taking into consideration the difficulty of reproducing this on the large skin surface area of a hull unless you employ a small army of expert laminators working in unison? 7) Your bond is only as strong as its weakest link. Resin/Filler/Foam. Is the bog stronger or weaker than the H80? 8) Could the very thing you are trying to avoid (filling in the cut cells of the foam with resin) actually work against you? Could having the resin filling the cells actually give a better mechanical bond, and possibly increase stiffness a very slight amount? When using West System resin on wood do they call for bog over the wood to prevent the resin from soaking into the grain? No, just the opposite. Almost any adhesive will perform better when the bonding surfaces are roughed up, why should this scenario be any different? In the commercial use of Divinicell that I have participated in the past, we never used bog between two structural components for concerns of delamination.(This last comment is contingent on the bog being weaker than the particular PVC cross linked structural foam being used).
If one is using open cell Styrofoam bogging is imperative, but the closed cell???
