Motorsport Composite Fundamentals: Resin Application

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Resin Application

06.57

00:00	In this module we'll focus on the tools used for the application of resin during the lamination stage of a wet layup construction, which is our primary focus for this course.
00:10	The goal is to thoroughly and evenly distribute the resin through the reinforcement, while also minimizing excess resin and avoiding pulling the reinforcement out of position, distorting the weave and creating voids.
00:22	Resin application is very similar to painting, so there's a lot of crossover between the equipment used.
00:28	With that in mind, we're not going to dwell on the super simple details here and stick to the composite specific considerations.
00:35	Let's assume we've got our resin mix in containers and ready to use.
00:39	We're now ready to start laminating layers of reinforcement and resin, or even start with a gel coat.
00:46	The most commonly used tool here is brushes.
00:49	Those suitable for composite work are relatively long and soft, which minimizes the pull on the reinforcement, helping to keep it in place.
00:57	Wider ones are naturally more efficient for bigger areas, whereas narrower ones are more agile for small tight areas.
01:04	If you're limited to a single option, I'd recommend using a wider one as they cover more bases and we don't want to be slowed down by only having a narrow one while the resin is going off.
01:15	Good chemical resistance is most important to avoid shedding bristles into the resin or gel coat.
01:21	If we're using brushes with chemical resistance, then we can soak them in acetone to clean them, being sure to shake them dry before storage and their next use.
01:30	We should be able to get at least a few uses out of them.
01:34	Another option is to use a squeegee.
01:36	These are firm but flexible flat rubber blades that can be used to spread the resin over the reinforcement.
01:42	The benefit here is that they make fast work of moving large amounts of resin and can also be used to remove excess resin from the layer.
01:50	They're also easy to clean, being such simple shapes.
01:54	The typical approach is to pour resin over the reinforcement and then work it around with the squeegee, but of course this is also commonly done with a brush.
02:02	If you're painting your house, the main alternative to a brush is an application roller, and composites are no different.
02:09	And just like with painting, it can help speed up the process.
02:12	The width of a roller follows the same idea as before.
02:15	Wider is more efficient for larger jobs and narrower is more maneuverable on the tighter stuff.
02:21	There's more differentiation between the rollers than with our brushes though.
02:25	The rollers designed for painting very smooth surfaces aren't ideal for most composite jobs due to the texture of the reinforcement that we're trying to completely wet out.
02:34	We're better off with something designed for a rougher surface, and that means that a short pile fleece roller is the go-to for applying resins and gel coats.
02:42	These are compatible with all resin types and are non-loss, so like our good quality brushes, shouldn't leave any debris behind in the resin.
02:51	The handle and frame parts of the roller are reusable and if treated well could last a lifetime.
02:57	The roller itself can be cleaned with something like acetone for reuse as well, but can also be changed out for different options or replaced.
03:05	Again, what we've just discussed is for application rollers.
03:08	However, rollers for wet layup lamination in composite works are more typically used for the purpose of consolidating the layup and driving out air bubbles, rather than wetting out the reinforcement.
03:20	These rollers are much firmer, if not completely solid, and not concerned with carrying and dispersing resin.
03:26	Bristled rollers, PTFE, plastic finned rollers and aluminium finned or paddled rollers are all examples with varying rigidity.
03:34	Generally speaking, softer rollers are good for lighter laminates where we want to be careful we're not pulling the reinforcement out of place, and firmer rollers naturally allow us to apply more pressure to consolidate thicker and heavier layers.
03:48	Fins are more suited to woven fabrics, where paddles are better suited for unidirectional reinforcement.
03:54	They're great for consolidating woven fabrics and helping to work out air bubbles, reducing the chance of any voids or pinholes.
04:02	The risk of working with a metal roller is that we can scratch the gel coat of the mould surface, so some extra care is required over the plastic options.
04:10	The other form of solid roller is known as a disc roller.
04:13	As the reinforcement is wet out, it'll pull and move to some degree.
04:17	We use the disc rollers to press the reinforcement into tight corners and avoid any gaps.
04:22	A tool often called a dibber is used for the same reason in pre-pre construction, to help manipulate and press the reinforcement into sharp corners and details.
04:32	These are essentially stiff plastic handles with different shaped ends, although it's fairly easy to fashion up your own with something like a plastic sheet or 3D printing one from the many models available online.
04:45	Lastly we have spray guns and while these typically aren't used for resin application during the lamination of reinforcement fabrics, they can be used to apply resin gel coats and various other coatings, primers and adhesives.
04:58	Spray guns are naturally in a very different price bracket, requiring considerable investment, but they are worth having if we're planning on doing lots of large parts.
05:08	On our spray guns we'll use much larger nozzles at around three to four millimeters, so they're able to spray much thicker fluids at a higher flow rate to speed things up.
05:18	This of course is at the expense of accuracy and the quality of the finish coat, but since the gel coat surface finish is controlled by the mold surface, it's not particularly critical and the same goes for the likes of adhesives or primers that will be sanded flat anyway.
05:33	Spraying these thicker liquids through a normal painting spray gun nozzle would be inefficient and likely cause blockages.
05:40	To summarize this module, the aim of resin application during the wet layout process is to thoroughly and evenly wet out the reinforcement with resin, avoiding voids, air bubbles and pulling the reinforcement or excess resin.
05:54	Brushes are the chemically resistant ones that won't leave behind bristles.
06:01	Squeegees are also great for moving resin around quickly and removing excess.
06:05	Rollers help speed up the process with softer options helping to carry more resin for application.
06:12	There are firmer options with raised features to help consolidate the laminate and work out air bubbles.
06:17	These are typically PTFE coated, plastic or aluminium, so they'll hold up great to all the abuse that comes with composite construction if looked after.
06:26	Other roller tools like discs can help to press the reinforcement into sharp corners to prevent voids or areas that will be filled with resin without any reinforcement.
06:36	Likewise, plastic dibbers are used to help consolidate pre-preg reinforcement into sharp corners and details in the mold.
06:43	Gel coat spray guns make quick work of laying down coatings or thicker liquids compared to more conventional spray guns.
06:49	They're tailored to be easy to use and clean at the expense of precision.