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Old 08-13-2016, 02:39 PM   #11
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Join Date: Apr 2011
Location: Mountain View, CA
Posts: 194
Here's a few condensed tips for anyone else thinking of doing this.

1. Buy all the fabrics, chemicals, and other supplies you think you might need up front. Getting sticker shock and second guessing how much I'd need was half the reason this took as long as it did. Downtime waiting to buy more or worse, running out halfway through a part and ruining it by trying to improvise.

2. If you're not vacuum bagging, you have to use really small strips of thin cloth to get the bubble-free coverage you need. The ribbing mold that turned out right was layers of really thin, thin, then lastly thick cloths laid in small patches. The thin cloths have their own gotchas; once wetted with chemicals, they wad up easily. Trying to lay down a large sheet of thin cloth over anything but a perfectly flat surface is equally futile for slightly different reasons to the thick cloths.

3. Measure your epoxy with a scale. Mix it 2 minutes. Scrape the sides of the cup. You can't overmix this stuff and if anything about the measure or mix was slightly off, it ruins the whole part in a way that can't be fixed.

4. You can't fix it. You either do it right the first time, or throw it in the garbage and try again. It's not like working with metal. Yeah you can patch little stuff, but that means _really_ little stuff. You can't fix the big stuff. Do not be tempted to sand away your shame. It's a losing battle and will make an unholy mess you'll have to clean up later.

5. Make sure your vacuum bagging is going to work before you mix up the chemicals. Once you've done that, the clock is ticking and you do not have time to find where your air leak is.

There are some great resources on youtube where people walk through the step by step of making parts like mine. I think watching those professionals now and knowing all the screwups they're _not_ doing would be more valuable by far than just seeing them make it look easy.

Last edited by jerrit; 08-13-2016 at 02:43 PM.
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