Once you decide on the resin and reinforcement fabric, it’s not hard to estimate how much of these materials you’ll need for your project. Just keep in mind that fabric types and weights will impact the resin-to-fabric ratio.
Use this fiberglass lamination calculator to help you determine an accurate estimate. This helps you figure out the entire weight and cost of the laminate–whether it’s covering an entire hull, or just a composite part.
If the estimate is too high, you can rethink the individual laminant layers and ply orientations in ways that might lower the weight and cost before beginning your project and, better yet, before placing your order.
All woven cloth has a small amount of fiber crimping (bending) that happens during the process of weaving fibers together.
A little crimp is unavoidable, but severely crimped or bent fibers are unable to support loads properly, especially compressive loads–the resin won’t be able to keep the fibers straight because the severely crimped fibers aren’t straight to begin with, and the laminate can buckle.
When you order woven cloth, whether fiberglass, carbon fiber, or aramid (Kevlar), be sure it’s sent to you rolled on a cardboard roll, and not folded.
Woven reinforcement cloth that’s been folded will have crimps and won’t be as strong as woven cloth on a roll.
Options for Calculating Needed Resin
For a bright finish if you’re sheathing a boat in a single layer of reinforcement material, you’ll need enough resin to wet out the material, plus extra resin to fill in the weave texture that is still exposed after the initial layup. For these fill coats, you’ll need to apply an extra one to two coats of resin.
To complete the estimate to use resin to wet out and fill the weave of one layer, you’ll need to know:
- The total surface area to be laminated
- The ounce-weight of the laminant per square yard
1) Calculate the total surface area (in ft2) of your laminating project:
How much surface area are you laminating? Think in terms of rectangles. Begin by looking at all sections to be laminated, including any irregularly shaped areas, as rectangles. Then do the following:
- Measure the length and the width of each rectangle, either in inches (if fairly small) or in feet (if large).
- For each rectangle, multiply the length times the width to determine the area.
- Add the individual rectangle area calculations to get the total surface area.
- If your original measurements are in feet, the surface area calculation will be in square feet. Use this number as "A" in the equation.
- If your original measurements are in inches, you’ll need to convert the total to square feet first. Divide the number by 144 square inches to get square feet. Use this number as "A" in the equation.
2) Use the Area Measurement to Calculate the Amound of Resin Needed
Take this area number and the ounce-weight of your fabric information and plug it into the following equation from the Gougeon brothers’ book on boat construction to get the amount of resin needed to wet out the laminant and fill the weave using three coats of resin.
A x [(Wf x 0.00085) + 0.0075]
A = The total area (A) to be covered by reinforcement fabric. Units are in ft2 (square feet)
Wf = The total weight (W) per square yard of reinforcement fabric f to be used in the laminate. Units are in oz/yd2 (ounces per square yard) because that is how woven reinforcement cloth is specified. For example, 10 oz. fiberglass cloth weighs 10 oz/yd2.
3) Use the Area Measurement to Calculate the Amount of Reinforcement Material Needed
Other than CSM which is specified in ounces per square foot, reinforcement materials are typically specified in ounces per square yard.
The area measurement you calculated above is in square feet. To calculate how much woven or nonwoven reinforcement material you need, convert square feet to square yards.
The area measurement you calculated above is in square feet. To calculate how much woven or nonwoven reinforcement material you need, convert square feet to square yards.
For example, if your total area is 126 ft2, 126 divided by 9 square yards is 14 square yards. You need 14 square yards of reinforcement material.
If you want to know the weight of the dry laminant, multiple the ounce-weight of the fabric times the total area in square yards.
For example, if you need 5 square yards of a 12 oz/yd2 fiberglass cloth, the total fabric weight is 60 oz.
To simplify the process of calculating materials for a layup using multiple layers of the same type or different types of laminants, think about it like this:
- First, determine the surface area to calculate the amount and weight of a single layer of the laminant. If using different fabric types/weights or different weights of the same type of fabric, repeat for each.
- Second, add the weight of all the layers and use the total weight to determine the amount of resin needed for wet out.
Calculate the Amount and Weight of the Laminant to Determine How Much Resin You Need
Your initial estimate should be for wetting out one layer of laminant. Once you know the estimate for one layer, you can add or subtract as needed.
How much surface area are you laminating? Think in terms of rectangles. Begin by looking at all boat sections to be laminated, including any irregularly shaped areas, as rectangles. Then calculate the surface area of the project in square yards by doing following:
1) Calculate the total surface area of your laminating project
- Measure the length and the width of each rectangle, either in inches (if fairly small) or in feet (if large).
- For each rectangle, multiply the length times the width to determine the area.
- Add the individual rectangle area calculations to get the total surface area.
2) Calculate the total surface area to square yards
This step allows you to compare the area to the cloth fabric weights that are measured in square yards (such as fiberglass (woven/nonwoven), carbon fiber, and aramid (Kevlar):
- If your original measurements are in feet, the surface area calculation will be in square feet. Divide the number by 9 to get square yards.
- If your original measurements are in inches, the surface area will be in square inches. Divide the number by 144 to get square feet. Then divide the number again by 9 to get square yards.
3) Calculate the total weight in ounces of one dry laminant layer to determine the amount of resin needed.
- Multiply the square yard number times the ounce weight per square yard of the reinforcement material (laminant).
- If you’re using more than one type of reinforcement material, repeat the step above for each type, and add the numbers together to get the total ounce weight.
- For Fiberglass, Carbon Fiber, or Aramid (Kevlar): The weight of the laminants equals the weight of the resin needed. This amount of resin is only for wetting out the cloth. An additional amount will be needed if you are also filling the weave (see Note below).
- For nonwoven cloth (such as 1708 biaxial): The weight of the resin needed is approximately 1½ times the weight of the nonwoven cloth. Nonwovens use more resin for wet out due to their added stiffness and weight compared to woven cloth.
- Optional if using CSM: Calculate the ounce weight of CSM for one layer. Note that CSM is specified in ounces per square foot, and the weight of the resin needed will be twice the weight of the mat, since mat is heavier than cloth.
- Calculate the total surface area to be laminated with CSM, as indicated above. The surface area calculation will be in square feet.
- Multiply the amount of CSM times the weight (in ounces) of the particular CSM you’re using to get the total ounce-weight of CSM needed.
- Multiply the total ounce-weight of the CSM times 2 to determine the amount of resin needed to wet out one layer of CSM.
Optional: Calculate the total weight of one layer of the laminate.
Once you know the weights of laminant and resin, you add them together to get the total weight. You can compare the combined weights for various laminants based on these calculations and decide whether to use one type of fabric or another depending on weight, cost, and overall strength, flexibility, and abrasion resistance needed for your particular laminating project.
Wetting out means saturating the cloth completely so there are no air pockets or voids, which look like white spots. Wetting out is done during layup. After curing, the weave of the cloth is still partially exposed, and needs to be filled using additional resin. This is known as filling the weave, and it’s done for cosmetic purposes only after the final reinforcement layer is in place.
The amounts of resin calculated previously are what’s needed to wet out one layer of laminant. After applying the laminant layer(s), you need an additional amount of resin to fill the weave, prevent print through, and create a surface that’s level and smooth for finishing.
Once you know the amount of resin needed for wet out, double that amount to get the amount of resin needed to fill the weave.
Additional Note: For a painted finish if sheathing a boat using epoxy resin, instead of filling the weave with epoxy resin, you can spray the prepared surface with a high-build epoxy primer. Spraying has the advantage of creating a surface without the pinholing effect you might get applying the primer by brush or roller. Spraying a high build primer to fill the weave may also save you some time over filling with epoxy resin.
Comments
0 comments
Please sign in to leave a comment.