EC! Laminate Sample #13:
- Reinforcement: 1708 biaxial glass with stitched mat, 1oz chopped strand mat
- Resin: Totalboat General Purpose Laminating Polyester
- Core: 1/4″ End Grain Balsa
Panel weight: 25.1 oz per square foot / 7.66kg per square meter
Thickness 0.4in / 10mm
Overview:
This sample is similar to #6 and #8, but this time I’m trying out an end-grain balsa core. It’s hard to see how well your core is bonded if there’s gel-coat, so this one is just clear resin in one shot. Turns out there were some significant voids/bubbles of trapped air under the core.
This is one of the big problems with coring open molded parts – it’s hard to be sure your have the core bedded down completely. Two possible fixes for this are: 1 – use a thickened core bedding putty and place the core down starting on one side and working it in a line so air gets pushed out the “front” for the joint. 2 – use weights (or a vacuum bag!) to press the core down into the first skin. Let the resin gel and then laminate the top skin.
For larger parts, this multi-step process is the only option because the gel time of polyester resin is typically pretty quick. It is a rugged and easy to build laminate and is suitable for projects where light weight is less of a priority but cost, gel-coated surfaces, and molding of complex geometry are important.
Video:
Laminate Schedule:
NOTE: I made a mistake (using the same template for meters and yards) with the estimate in the video. This is a corrected version. Correction highlighted in orange.
Things to Improve:
Fewer voids and less air! Really though – that’s about it. I was trying to show how easy it is to get voids behind your core – and how hard it is to tell if they’re there if you have gelcoat. Core bonding putty and some type of pressure are the two best ways to deal with this. I should have taken the time to mix some filler into the resin I used to bed the core. Next time!