Hi all,

I am new to composites and I am currently trying to skin some parts for my car.

To begin, I had issues with bonding the fabric to the parts but I have seemed to solved my issue by not folding the excess behind the part for a clean edge. My main issue at the moment is sanding. I am struggling to get a nice flat surface and I am reluctant to use 120 to begin flatting as I always end up with scratches I struggle to sand out. What is the most efficient way to get a smooth finish without sanding forever. Also, what is the best way to remove drips that have cured and also a bulging edge where the resin has collected on a vertical edge on a part? I worry when I’m sanding I will hit the fabric.

My last issue seemed to be on the weave when I finished sanding, it looks like a void between the resin and the weave as well as moisture under the resin when damp outside.

I am using XCR resin and have been told it is self levelling and does not have air bubbles but I keep getting bubbles!

Thank you

+x

 

Warren (Staff) - 7/8/2019 4:08:24 PM

Another tip with drips is when the resin is just firming up (like firm cheese), use a scalpel blade to slice off most of the drips.  They cut through easily at this point leaving just the smallest base to sand and shape when the resin has hardened up fully. 

I massively appreciate the advise! It should hopefully solve my issues.

What would be the best way to heat the resin up? Use a hairdryer on the underside of the cup?

I am aiming to have very high quality aesthetically finished parts. What would be the best procedure to finish with a very flat/smooth and glossy surface? Are spray clear coats required?

Thank you again for your help,

A hair dryer will work okay or just leave tge pot on a radiator for a few minutes

You just need good patient wet sanding, using a block where appropriate. Change the water at each grit chage also.
Aim to get the resin flat to the touch using the coarsest grits and use the finer ones only to remove the marks left by the previous one. 

Be prepared to re-coat if necessary during the coarse flatting stage. A new brush used for each coat will also limit the possibility of 'fish-eyeing' which, I've found, can happen when using brushes previously cleaned with acetone. 

Finishing with a sprayed clear coat will likely give you the best cosmetics and most resilient finish but excellent gloss can be achieved without. It's just a bit more labour-intensive.
However, if your parts are likely to be exposed to the sun or other heat sources, it's likely that you'll experience shrinkage of the resin that can leave a bumpy surface, given the relatively high resin thickness. In this case, it's a good idea to give the coated parts an elevated temperature post-curw after fully coating and deal with any shrinkage impact during the subsequent flatting. This should help make them a bit more resilient to temperature afterwards but probably not quite as UV-resistant as a clear coat finished part.