# Fiberglass Cloth & Resin Calculating

I’m going to be starting up some board building in the coming weeks. I’d like to know is there a way to calculate how much fiberglass cloth & resin needed for a surfboard depending on its size? I’m sure everyone has a different amount but I figured I would ask to get an idea of how much of each to order.

Greenlight published a very handy resin amount chart that I think is about perfect.  If you’re new at it, use the suggested max amounts.

This is one that considers the weight of cloth, number of layers, length of board, etc.

https://cdn.shopify.com/s/files/1/0689/1441/files/Resin_Amounts_Per_Board_Length_Chart.pdf?6010205388050185260

Mr. Mellor,
Can you explain how to use that chart? It gives a minimum and maximum but doesnt tell how they came up with the answers. Yard x oz. x multiplier doesnt work with their answers.

Im guessing to get their minimum they use second length board with a 1.5 multiplier. Example 5’5" is 1.81 yards rounded. 1.81 x 4oz. = 7.24 x 1.5 = 10.86 which is 11 rounded which is minimum for the 5’0" - 5’5" board. Clueless on how they got the max because with a 1.75 multiplier it comes to 12.64 not 18

After glassing a few hundred boards, this becomes second nature.

I glass a shortboard with one bucket of resin.

Total.

When I worked as a production glasser, I used a lot.

That changed when I started buying it myself.

Hi Wisco-

If it’s a ‘how much to buy question’, you could research that by looking at the contents of a retail ‘BYOB’ kit that is similar to your first planed build(s).

http://www.foamez.com/surfboard-diy-building-kits-c-23.html

http://greenlightsurfsupply.com/collections/surfboard-building-kits

PS Looking good Barry!

Go big…

Take notes

Hi -

I can see where it might get a bit complicated.  I’m not sure how they arrived at their amounts.

In the past, I used to recommend that people start their calculations with:  The length of the board, the weight of the cloth, and the number of layers.

Do the math and figure out the total weight of the cloth being used and multiply that by 1.5.   That should give you a ballpark estimate on how much total resin to use.

A 9 foot board will need about 3 yards of cloth.  If the cloth is 6 oz fabric and you’re doing a double layer for the deck, the weight of the uncut cloth will be 36 ounces… less after you cut it to fit the outline.  Sooo… 36 X 1.5 = 54 ounces of mixed resin.  The Greenlight chart says 36 - 50 ounces of resin for the same glass schedule.  Close enough.

That’s just my recommendation for a 9 footer, double 6 deck lamination and allows for some waste.  A beginner using MEKP catalyzed resin will likely find himself ‘flooding’ the board and squeegeeing off a lot of excess in an effort to save time.  If you’re using UV catalyzed or epoxy resin, you will have more time and can get by with using resin more sparingly.  Epoxy is more expensive so there is definitely an argument for wasting as little as possible.  With epoxy blends of slow/normal cure times, a beginner has the luxury of not having to hurry like with MEKP catalyzed polyester.

I think there are plenty of horror stories around here of people getting caught with their resin kicking off before the laps are tucked, bubbles galore, etc. With those horror stories in mind, I’d say catalyze a bit on the slow side and allow yourself enough resin to make a mess on the floor rather than fucking up that blank you spent so much time shaping and decorating.

So you can use the chart or do the math (or both) but either way beats stuff I’ve read here like, “just use 18 ounces per side” with no concern regarding length of board, weight of cloth, or number of layers.

If the amounts given result in way too much waste, cut it back a bit… go for the “minimum” amount on the chart, multiply cloth weights X 1 or 1.25 if doing the math, or however you figure it will work for you.  After the very first lamination, you’ll have a better idea.

PS - I’ve also read here that using epoxy somehow saves resin… I’ve found it still takes a certain amount to saturate the cloth.  If using the normal or slow cure resin, you may find yourself using it more carefully/sparingly and still have plenty of time to work it around but my experiences haven’t resulted in a significant weight savings one way or the other.

I laminated some 8" x 24" XPS test pannels a while back.  As a hack, the best I could do with 6 oz E-glass was 2.25 oz epoxy (resin + hardener “volume”) per square foot of XPS foam.  As a hack, I suspect I would need more for PU and EPS.  For a 7-6 board, my number is very close to the high recommendation on the GreenLight Chart.

Brian said his GreenLight Chart is for units of weight in oz.  Resin Research  and Green Room epoxies can be mixed by volume, 100:50 (2:1) – 100 oz resin by volume = 110 oz by weight; 50 oz hardener by volume = 49 oz by weight; 150 oz by vol of resin + hardener = 159 oz by weight.  Multiply the (mixed) weight recommendation by 0.94 to get mixed “volume” of resin needed (150/159 = 0.94.)

My assumption for “estimating” the surface area to laminate one side of a surfboard is that the surfboard is an ellipse that is 6" wider and 6" longer than the actual board.  Surface area of an ellipse is 1/2 width x 1/2 length  x 3.1416 (pi).

Bottom line,  just use John Mellor’s method and/or the GreenLight chart.  They are a good place to start.  For a hack like me, I go with the highest recommendation plus a few extra oz.

EDIT:  BTW give the man some points so he can interact…

_____

For monolithique build, the lower resin/fiber ratio for better strengh is not right for standard build, better to be on higher ratio : thicker skin (resist better to buckling) and waterproof. Lam don’t need to be over saturated for sure but a dry lam full off pinholes is worst for durabilty. Lenght x width x glassweight x number layer x 1,5 to 1,8 depend of porosity of foam. Ended with some resin in bucket, resin you pull off when you lam.

Length, width , polyy or Epoxy.  Weight and Type of cloth.  Come on man you may be a beginner, but you should know better.  We can’t pull it out of our—(ear).  Really surprised none of the Sway’s Boyz didn’t  ask.

That’s a great table for hand laminations.

When using a wet out table and bagging, I’m using about 10 to 20% less epoxy than their minimum.

Mix up 15 ounces of Resin Research clear resin. Laminate the bottom of the surfboard. You will learn in a big fat hurry if that is too much or not enough resin. For the rest of your life you will remember that day and you will now have the wisdom needed…

Stingray

i gotta say i need to get better at this hahaha. i seem to always make too little and need to make another 100 - 200 mls.

hahaha. oh well.

A great man once said, “the mark of a craftsman is not that you never makes mistakes its how well you incorporate them into the finished product.”

RIP dovetail surfboards, “such a good guy”;(

The model aircraft guys aim for 1:1 cloth:resin.We used to weigh the cloth and shoot for around 1:1.4 cloth:epoxy. When Stump went lower epoxy he used a steel squeegee and bagged, but often ended up a bit too dry in patches. I’m nowhere good enough at laminating to hit low ratios. Like Sk8 I often have to mix a “bit” more.

Sealing EPS blanks helps reduce resin load. Coated the blank in Zinsser paint/beads and sanded back and that helped reduce resin absorption by the blank. No delams so far on that board.