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Estimating epoxy amounts - West System

This formula will help you estimate the amount of mixed epoxy needed to wet out fiberglass cloth (assuming a resin-to-fiber ratio of 50:50) and apply three rolled epoxy coats to fill the weave of the cloth, i.e. "fill coats."

The formula includes a waste factor of approximately 15%; however, more (or less) may be needed depending on the job and personal application technique. The epoxy is applied at standard room temperature, approximately 72F.

Gallons of mixed epoxy=A x[(Wf x 0.00085)+0.0075]

A=Total area covered by fiberglass. Units are in square feet (ft2)
Wf =Total weight (W) per square yard of fiberglass (f) cloth used in laminate. Units are in ounces per square yard (oz/yd2), i.e. 6 oz fiberglass cloth weighs 6 oz/yd2.

Let's use the Optimist pram in the previous article as an example:

Bow: 322 in2 Transom : 507 in2 Side x 2:3784 in2 Bottom:3444 in2 Total sq in: 8057 in2
  /144 Total outside sq ft: 56 ft2

The INSIDE is covered with 6 oz fabric and three fill coats. The bow box is covered with 6 oz fabric on one side only.

Bow: 322 in2 Bow box: 720 in2 Transom:507 in2 Side x 2:3784 in2 Bottom:3444 in2
Total sq in: 8777 in2 /144 Total inside sq ft: 61 ft2

Outside calculation 56 ft2 [(12 oz/yd2 x 0.00085) + 0.0075] = 0.99 gal
Inside calculation61 ft2 [(6 oz/yd2 x 0.00085) + 0.0075] = 0.77 gal
Total 1.76 gal mixed epoxy

Note: a Group Size B resin and hardener makes 1.2 or 1.3 gal of mixed epoxy depending on hardener.


Epoxyworks 18 / Fall 2001

Copyright 2001, Gougeon Brothers, Inc. All rights reserved.
Last Modified on 10/28/02.
Reproduction in any form, in whole or in part, is expressly forbidden without the consent of the publisher. EPOXYWORKS, Gougeon Brothers, WEST SYSTEM, Episize, Scarffer and Microlight as used throughout this publication, are trademarks of Gougeon Brothers, Inc., Bay City, Michigan, USA.

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