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Hi buddy, hello everybody,
Shelby Cobra at which you worked is awesome!
There are several reasons which may causing dry spots at the infusion process:
- too high vacuum (boiling of volatile components)
- improper type of resin for infusion (low molecular weight solvents)
- poorly sealed or injured bag
- cracked mould
- too fast resin flow
- containing moisture fibres (water vapour problems)
- not degassed resin
Looking at the pictures you pasted, I'm pretty sure that your problem is, however, either leakage or cracked mould. If the bag and mould don’t hold vacuum, you will not infuse quality products no matter how hard you try.
After removing the item from the mold, do you have lots of tiny, quite annoying to remove, dots of resin remaing on the surface of mould? If so, this is the trace after that resin in the dry spots had once been. (and evidence of leakage, not a lack of impregnation at resin flow). Another confirmation of my theory is the fact that while you use the same factors and technology, you can make a good item from time to time.
While it may seem that the fibers after compression does not spring back, it does, just like a quilt. And that's why, even with minimal loss of mould containment, the vacuum pressure of "standing up" fibers cause
resin replacing with the air taken in fibers heterogeneity - see your photo.
However, I would definitely recommend 5 min. degassing prior to infusion. To cut a long story short, I'd suggest about 20 mBar (absolute pressure) for degassing and about 50 mBar for infusion.
To better diagnose your problem there is a need for more data - what exactly is vacuum level in your pump? (you definitely shouldn't use a two-stage oil pump directly to the infusion), what type of sealing type and bag you are using, how looks your mould.
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