Step Three: Proper Lay-Up Technique
Pre-Layup Notes
- Before mixing any resin, lay out the fabric and precut to size and set aside
- Avoid distorting the weave pattern as much as possible
- For fiberglass molding, ensure the mold is clean and adequate mold release is used
- View our video presentation “MAX EPOXY RESIN MIXING TECHNIQUE”
- Mix the resin only when all needed materials and implements needed are ready and within reach
Fabricating Lay-Up Procedure
- Lay out fabric and cut to size.
- Mix proper amount of resin needed (see below to determine how much resin is needed).
- Apply mixed resin to fiberglas in even coats. Always apply the resin to the fabric instead of placing the fabric over a layer of resin. This method allows adequate saturation and prevents air entrapment.
- Add additional layers of fiberglass as desired, layer by layer.
- Use a roller or spatula to press out entrapped air from the layup, being careful not to distort the fabric weave.
- Allow to cure for 24 hours.
Determine Fabric Weight
Typical Fiberglass Weights
1 yard of 8 OSY fabric 38 inches wide = 224 grams
1 yard of 10 OSY fabric 38 inches wide = 280 grams
Place the entire precut fiberglass to be used on a digital scale to determine the fabric to resin weight ratio. Measuring by weight instead of using ounces per square yard ensures accurate composite fabrication and repeatability.
Determine How Much Resin is Needed
For High Performance Prepreg (Pre-Impregnated Resin):
Maintain 30%-35% minimum resin content by weight
For General Hand Layups:
Maintain 40% resin weight and 60% fabric weight
Equation to Determine How Much Resin is Needed
(Total Weight of Fabric Divided by 60%) x (40%) = Weight of Mixed Resin Needed
FW = Fabric Weight
RC = Target Resin Content
RN = Resin Needed
(FW / 60%) x (40%) = RN
The calculated Resin Needed is the total amount in grams of resin – both Part A resin and Part B curing agent – needed for every square yard of fabric.
For Example, 1 square yard of 8 OSY fiberglass = 224 grams
(FW / 60%) x (40%) = RN
(224 / 60%) x (40%) = 149.33 grams of resin needed for every square yard of 8 oz fabric.
Computing for Resin and Curing Agent
Use the RN amount to calculate the amount of Part A Resin and Part B Curing Agent is needed.
If the Mix Ratio of the resin system is 2:1 (or 50 PHR):
2 Parts Resin: 66.67% x 149.33 = 99.56 grams Part A Resin
1 Part Curing Agent: 33.33% x 149.33 = 49.77 grams Part B Curing Agent
99.56 + 49.77 = 149.33 grams
Fiberglassing and Vacuum Bagging
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