# Spreadsheet for Resin Usage Epoxy and Polyester

Hello Swaylockians,

I am getting ready for my next glassing session, and part of my pregame is seeing if I have enough resin, cloth, etc…

Are people using spreadsheets at all to calculate the amount of resin needed for their lams? Or are people good with rules of thumb such as 2oz per linear foot of board per layer of lams and 1oz per linear foot of hot/gloss coats?

I am using 6oz E-glass and Resin Research epoxy, 1 layer up top with a 3/4 length deck patch, 1 layer down low with a 1/4 length tail patch. The board is 8’ x 23’ x 3.5" . With the thumb rule I get:

16oz top + 12 oz deck patch,16oz bottom + 4 oz tail patch+16 oz hot coat+16 oz gloss= 80oz = 5 pounds= 2.2 kg or so. My spreadsheet calculating all by weight per unit of area comes close to this, using a resin to cloth ratio of 1.2 to 1 by weight. The jug of resin still weighs 8 pounds so I am plenty good to go without reordering.

I can hear Stingray saying ‘it’s a surfamaboard, it’s epoxy, just mix some more’…so true. I would still like to have an organized way of starting out close, provided I can feed it a good set of numbers like area or weight of cloth per operation. Some of the fiberglassing vendors have online calculators, but they seem to be aimed a bit more at selling rolls of cloth and gallons of resin than figuring out how much to put in the bucket for this lam or that coat.

Questions:

1. Is the rule of thumb fluid ounces volume? In that case I am probably off a little by weight.

2. I have heard it said that epoxy lams take less resin than poly lams. Is this really true in simple hand layups like this? Is there a finite number that goes with this?

3. If such a spreadsheet was deemed accurate enough, could it be placed on Sways as a document or coded into an applet for public use?

Thanks, -J

Come on guys bone up on this.  I’m not that familar with Epoxy lams.  One quart per side should be enough??  Where’s an expert when you need 'em??

Ideal epoxy/ cloth ratio is 1 to 1 by weight.  But you can’t get that by hand laminating.  And you always need to mix more than you apply.  You can always weigh your cloth, and double that for the amount of epoxy you need to mix.  But rather than formulas, just take notes.  A 7-0 HPSB mixes around 350 g of epoxy and 140 g of hardener for a single 4 oz cloth.  Size it up for what ever board you are doing.

Your milage will vary.  The better you are at glassing with epoxy, the less you need, because you are quicker, better with your squeegee, and you spill less.

Please pay attention to this!  DO NOT SCRAPE THE SIDES OF YOUR BUCKET TO GET THE LAST DROP OUT IF YOU RUN SHORT!!!  That last bit is always the unmixed dregs.  If it clings to the side of the bucket too much to pour out, it clung too much to mix well with the hardener.

Thanks Guys, I appreciate it.

McDing- your 2 quart (64 fl oz) estimate and my spreadsheet are within an ounce or two of each other for 6oz cloth. How did you do that?

Everysurfer- thanks for the baseline numbers. Would that number be for one side or two? Your HPSB is probably a more effecient shape area-wise than my board. I will take your suggestions about not scraping the bucket and will be taking notes: 1) amount/type of cloth used , 2) amount of resin mixed , and 3) amount left over and attributed to spillage or other losses.

If anyone else has a rule of thumb or hard facts about this don’t be afraid to post up. Some of us do not have the ‘calibrated’ eyes and hands of experience to temper an estimate.

Also, if anyone has thoughts about the quantities of epoxy versus polyester please feel free to comment as well.  It would seem for the selling point of needing less epoxy would have to come from some facts -like either a lower resin-to-glass ratio, or fewer fill coats to get the job done, or a combination of both.

As always, thanks, -J

I’m no expert. I always mix the stuff stuck to the sides and I always scrape it onto the board. So far it’s always turned into plastic.  I’d go 18 0z. on the bottom, 24 on the deck. Mike

I have never heard that advice about not scaping, but it makes sense.  I usually do as I saw Greg Loehr do in his Epoxy 101 video.  Dump out the whole bucket in long lines across the length of the board and then place the bucket upside down on the cloth to drain while you start using your spreader.  After about a minute it will have drained about as much as if you had scaped it.

Regarding how much to use…  It depends on a lot of factors:  how long are your laps, how thick is your cloth, are you doing the deck or the bottom?  I used to over mix a lot, and I let the excess dry in the bucket.  After it hardened I popped out the puck, sanded it flat, and then spray glued some sandpaper onto it.  This makes for exellent sanding blocks.  Over time I learned to start mixing too little instead of too much.  I have enough sanding blocks now.  Sometimes I mix up a second batch to finish off a lam.

BTW… I use a digital scale to mix my epoxy.  I hate being a slave to the volumetric lines on the cup.  There are many Swaylock’s epoxy people who hate gravity and don’t mind the volumetric slavery system.  I have the utmost respect for these individuals, but wish that they would just get with the program.  </sarcasm>

If you mix it right then that woiuld not be a problem at all.

If I was doing it i’d mix up about 16 oz of epoxy.  Pour 3/4 of it out on to the board in long lines. Put the rest aside for a bit.   Connect the epoxy by moving it to the shortest distance to wet out. Meaning it is ok to work side to side, cross ways, etc. just make sure the epoxy touches the cloth…let it wet out a bit, it can’t not be forced into the cloth like poly.

Now with the clear left over pour and work into the drape. if you need more epoxy mix it up in small batches. Mix these small batches by volume on a digital scale, very easy…very accurate.  Pull the drape out with your gloved hand and with the spreader make sure the cloth is touched by epoxy.

Now go back and work your lamination on the deck. Move slowly. If you get frothy epoxy, pull it off and wipe into bucket.  There shouldn’t be a lot of excess.  Once the top is down and tight, move to the rails MAKE SURE YOU HAVE A NON FROTHY SPREADER, keep it clean.

The only reason why you use less epoxy than poly is because you don’t have the run off onto the floor when you wet the drape.   With epoxy you don’t do the waterfall wet out drape thing.  Unless you are doing a Tint job with epoxy…then you waste a bit of epoxy.

Now if you are doing a color job with epoxy, my recommendation is to mix up enough + to do the job. Any left over can be put in a ziplock bag and put in the freezer to be used for fin plugs, leash plugs etc.  (warning, you need to put it in the freezer before it starts to therm, and it will only last a a few days to a week in the freezer. it’s not a long term storage)

Doing a clear lam is very simple with epoxy, you can just mix up more and keep going. The kick is slow so there is time to remix and conquer.  Bottom line: The less you move the epoxy, the better the cosmetics the board will have. If you tractor plow the epoxy from stem to stern, then you will get a frothy mess.  it will be ok for a white board, but if you have any color work, it will look like a monkey glassed it.

So…Start out with a ammount of epoxy that will get you started, then mix more…you really don’t want to over mix, because that is just wasting the product.  And if you take a wooden tongue depressor to mix you batch of epoxy and scrape it around the sides of your bucket, you won’t have to worry about non-mixed product.

Thanks for the tips Swied, Rooster and Insane. Thank you very much for the extensive writeup Resinhead. I would have monkey-plowed the epoxy into a foamy mess for sure otherwise. This will only be my second board lam with epoxy, I did the others boards with low VOC poly and iso gloss.

I took the planshape area from AutoCAD, added 3" lap all around, and drew up the deck and tail patches and fed them into the hopper. It’s now givng me 620g/17.5 fluid oz/22oz scale weight resin for the top+deck patch, 480g/13.55 fluid oz/17oz scale weight for the bottom+tail patch.

So bottom’s up and here we go! I will try to keep track of the weights and report back. -J

PS I rememberer this thread along the way, http://www.swaylocks.com/forums/how-much-resin-57 , where Jamie lays out his recipe for a 5’-7".

17.5 fluid oz top and 13.55 fluid oz bottom sounds too skimpy to me. Hope it’s not too late…

Your board is wide and thick. At 8’x23"x3.5" I’d use at LEAST 20 oz mixed material on the top. With the 2:1 volume ratio, you can increase in 3oz increments. IE: 12resin/6hardner=18oz. 14resin/7hardner=21oz. In this case, since you are new, and the board is big/thick, I would go one more: 16 resin/8hardner=24 oz mixed material for the top. Even though epoxy is pricey, I’d still rather have too much than too little. So if it’s not too late, I’d do 24oz mixed material on the top and 21oz mixed material on the bottom.

Thanks for the sanity check Jamie, it’s not too late. At the rate I am going tonight it might be prep only: sweep shop, cut/weigh cloth, re-run the numbers and lam tomorrow after work.-J

Scrape away at your own peril

So I decided to lam the bottom, no sense watching TV when you can be getting sticky in the workshop. Things went good, I dallied a bit too long on the bottom when I should have been wetting the rails. I guess they call it Kwik Kik for a reason…

Glass: predicted-375g, used- 342g, might be off due to hand trimming glass

Resin: predicted-480g, on board- 522g,  Mixed in two batches of 500g and 150g respectively

Waste: Spilt/leftover approx 128g . Almost as much as my second batch…and the last 53g of the second batch went exotherm in the cup.

Thanks for the help everyone. I will try again with the top and see what I get. -J

Glass weight (g/m2) x board lengh (m) x board width (m) x 1,8 = enough resin mix for lam with 2" laps without needing to overwork resin. Lam on resin sealed surface.

I’ve advocated resin amount formulas for years.  When building some giant longboards with up to triple layers on decks, I simply had to develop a method that would give me better than a general idea of resin amounts.  Too much would be a total waste, too little would be a pain in the ass.

Steer clear from ‘formulas’ that fail to consider number of layers, weight of cloth, size of board, etc.

I estimate my resin amounts by first calculating the weight of the untrimmed cloth.  To keep it simple I just figure the total length and assume a cloth width of 1 yard.  Include multiple layers of cloth as part of the total length… I.E. 2 layers on 6 foot board = 12 feet (4 yards.)

If cloth is 4 oz per sq yd, you will have a cloth weight of 16 oz. for that board.  When trimmed, it will be less but this is just for resin calculation.

My multiplication factor is about 1.5 giving a resin weight for 2 layers of 4 oz on a 6 foot board of…  24 oz.  A skilled glasser can get by with less but a little extra allows for quicker easier lap wetouts, minimizes pin air, and avoids the hassle of having to mix extra in the middle of the job.  If you find you have too much excess, simply reduce the multiplication factor.

I think you are on the right track to developing a formula that is very workable.  Just take notes and make adjustments on future batches based on your skill level and past experiences.

LeMat, Johnmellor-thanks for your estimating formulas. I am going to place them on tabs in the spreadsheet and see how everything compares.

-J

Don’t forget that you can lay the laps on top of the board before wetting them, then wet the laps out first and pull the resin back towards the center of the board then drape the laps back over the board’s rails. I’ll alternate between doing this method and laminating with the glass draped over the rails before wetting the glass when I use epoxy, which is most of the time. When you pull the laps back over the rails start from the center and work towards the ends to avoid problems.

Thanks Sharkcountry, that is a good tip. I think part of my problem is that I am only doing a board a year, so I don’t get to ‘practice’ very often.  I appreciate all the formulas,tips, and tricks people are sharing on the forum, it really helps. -J

Results in for the deck:

Glass: predicted-540g, used- 457g, changed cutlap location to be narrower due to 30" cloth width on 23"w  x 3.5"d  board. Next time I will use 32" so the lap doesn’t slide out of place, or something like a staple gun to tack the cloth to the stringer for better alignment.

Resin: predicted-600 (based on new cloth number), on board- 707,  Mixed in two batches of 580g and 217 respectively

Waste: Spilt/leftover approx 90g . Only about 30g left in the second cup, a little more on the floor and I wet out a brush for doing rice papers.

I am still getting too much on the board according to the numbers. I did waste less overall this time plus wet out and tacked some rice paper artworks so I am feel like I am making a little progress. -J

Bottom hotcoat: 335g total KK resin+hardener, 8 g Add F, had 20g left over. It seems like my 3" chip brushes (cheap brushes?!?) keep shedding even if I work them ahead of time with my fingers and tape.

Top hotcoat: 380g total KK resin+ hardener, 9 g Add F, had 48g left over, but I had another project in mind and staged so I used up most of the rest on that.

-J