Hey guys, an update with a new piece I pulled yesterday.
The piece is small and has a very deep contour to the mould (good for practicing on). There is some bridging on the small tip of the teardrop but that is another lesson I am learning to cope with. I have a couple pinholes, but more-so whole bubbles in the final part (especially on the tip of the teardrop where it bridged). However it is MUCH better than the last piece I tried. I followed Fred's steps as close as I could. I warmed everything up, and allowed extra resin to flow into the part after closing off the vacuum line (which I think helped a lot). Here are some of the notes I have made from this sample:
1.
There is no need for infusion mesh on the vacuum side of the laminate. I had originally thought it might help distribute the vacuum across the part better, or aid bringing resin to the vacuum line. I had also wondered why the resin seemed to froth and create more bubbles right by the vacuum line. I now realize that the infusion mesh is what is creating this frothing, as there are a large amount of bubbles that are only contained where the infusion mesh is. I realize that this doesn't really effect the final part (as the vacuum line is far enough away from the part that it shouldn't matter) but I had always wondered why it seemed to make more bubbles at the vacuum line and I believe this is why. I know in the video "how to make a car bonnet", Matt places infusion mesh along the vacuum side, but I am going to try my next infusion without this. Also, he uses peelply, while I do not.
2.
Once the resin reaches the vacuum hose, the resin in the middle of the part still contains air entrapped in itself. I have researched and it is due to one of three things. One, there is a leak somewhere (I did the vacuum drop test and it was sealed up). Two, the resin is off-gassing (I have heard that epoxy resin's do not tend to do this as much as vinylester or polyester resins, and it is quite dry in my shop so I do not think it is caused by this). Three, there is air entrapped in the resin from mixing that has not come out of the resin before infusing (this is where I think my problem is). How important is it to de-gas the resin before infusing it? I have found that even if warm it and let it sit for 10 minutes, there are still some bubbles in the resin. Also, the working time on some of my epoxy is only 30 minutes if mixed in large enough quantities, so letting it sit for a long time really is not the best for some applications.
3.
Of the few pinholes I have, they appear more frequently the closer towards the vacuum hose I look. This may have something to do with letting even more resin travel through the part as Fred had stated. The real problem with this, is that I will end up with too much excess resin in the catch pot, and could have a potential fire hazard as the large mass of curing epoxy could overheat and catch fire. Is there someway to perhaps re-infuse the resin once it reaches the vacuum hose? Almost like a cycled system until all of the air is taken out? This seems complex, and maybe not possible while keeping vacuum on everything, but just at thought.
I will be making the exact same part once I clean up the mould, but this time I am going to get rid of the infusion mesh on the vacuum side, and try de-gassing the resin to see if that makes a difference. If anyone has any advice, tips, or arguments to what I have said above, please feel free to comment. I hope that this thread can help not only myself, but others as well.
-Mike-