Nice work Cap looks like it will be a damn fine yield!
EF, sorry to hear that I steered you in the wrong direction for your build (I use the method of, sanding heatsink to 1000 grit US, using high performance thermal grease, pressing hard for 30 sec to create vacuum and thin even layer, add kapton tape to stop lateral movement.) I have installed and retired many hundreds of 20mm stars and COBs. If I had drilled them all to mount them, I'd still be working on it or I would have never got the projects done. Also, my heatsink surface would be drilled with thousands of holes but they currently have none which I appreciate. I have changed my 20mm setup 2 or 3 times and have already changed my COB setup 2 or 3 times and added 20mm to them. So in my case drilling and mounting them all would have been a nightmare. Flattening the heatsink surfaces however, was a job that only had to be done one time and continues to serve its purpose, so I believe it is a more worthwhile investment of time although not completely necessary to grow good bud.
The SOLERIQ test has nothing to do with comparing vacuum method vs COB holders, it has to do with screwing the COB directly VS screwing the COB holder. (That said, I am very skeptical that COB holders provide superior cooling over the vacuum method.) I am not defending the "screw down the COB directly" method and the article itself states: "screwing with too high torque can cause the CoB to bend which can have an adverse effect on the thermal interface." However there are problems with this demonstration I would like to point out.
The thermography scan cited did not contain enough information to determine anything conclusive. They failed to show the thermal scale and we have no idea how much power they are pumping through the COB. The more heat you run through it, the more the thermal interface comes into play. We have no idea how long they let the test run, did they allow enough time for thermal stabilization? Did the thermograph automatically adjust its thermal scale in each experiment or were they done side by side or with a fixed scale? Also, I would never advocate the use of a thermal pad regardless of mounting method and the test showed poor performance no matter which way it was screwed down with a thermal pad so I ignore A and C. And finally, we have no idea how they prepared the heatsink surface or what the surface is made of (could be plastic). It seems they used a relatively poor performing thermal grease (~6K/W, only half of the PK3 we use).
In summary, I would put my recommended mounting method up against any of these with full confidence that it would be the best thermal performer and would hold up with time. The only downside, it is not pretty, but it was not meant to be. Also, my method should not be used with stars smaller than 16mm because the vacuum pressure is not high enough to be reliable. I have sold lamps using the vacuum method to folks that trusted me and I want to reassure them. Again,
this test has nothing to do with my argument, but I call BS that D would outperform B to any significant extent in practice. I accuse the experiment of being poorly designed or intentionally skewed but I am open to being proven wrong
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its what just white led is missing in comparison to hps IMO. I think I am gonna use mo's red kessils as a test to that end. turn it on like 5 min before lights out and off 5 min afterwards. They will only get two weeks of that so we will see. I think it is probably more critical from the get go so they start setting earlier. The earlier they set the bigger they get IME. HOwever.... oddly, my grow is seeming to pick up speed this week.
