Feeling confused. I’m about to dive into my transom/stringer rebuild project. I’m going to use vinylester, but not sure which brand. Any suggestions?

It seems the consensus is to mix by weight.

Reading instructions online or watching videos, they start with a certain amount of resin in a cup on a scale. The amount of resin is weighed in Kilograms/grams/OZ. Good. That’s a measure of weight.

But then they talk about adding catalyst by drops/cc/ml. That’s a measure of volume.

How do I calculate 1-2% catalyst if the resin is in grams and the catalyst is in drops?

What am I missing?

Contact the manufacturer.

Or, use West System epoxy. Has calibrated pumps for the different components so it's dummy-proof. Even I could do it.

Volume

Buy a dispenser bottle for youre catalyst.
Best investment you’ll make.

typically 1 - 3% dependent on ambient tempt and required working time.

X# OZ’s resin = X# CCs catalyst.

All the suppliers have charts for this, that they will give you if you ask.

i go by weight... works fine up to now !

https://www.uscomposites.com/

U.S. composites vynil ester 700 resin. Mix it by volume. (each mix, mix it for 2 minutes vigorously !)

Pre cut your glass and stack it by total sq in for each mix, use this formula

32 oz resin for 1296 sq in of 1708 fiberglass. 1296 is 36 x 36 or 1 sq yd.

16 for 648

8 for 324

4 for 162

2 for 81,
this makes it easy to calculate a pour/mix for each part of the job since each cut and mix will vary but this way it's easy to keep consistency on mekp amount with out over mixing and wasting resin.


Consistency is key across every part of the job or waste goes astronmical.


If your going to weigh anything, weigh 4 ounces of resin and write it down, then pour a quart and thicken it with cabosil, once you have somewhere between mayo and peanut butter consistency break that quart into 8 batches by weight.
this way your cabosil and mekp amount will be consistent and on deck ready to go.

Extra tools, prep and plan. I got 2-3 gallons of acetone going, 1/2' dirty for pre soaking bubble roller heads etc etc, 1/2 as a tool rinse and a clean gallon or more for final clean.
i'm super cheap so everything except roller covers gets cleaned wiped and used over until it's shot.
Let your mix cups sit a day or so and the dried resin will peel right out.

How big is yoir job ? How many feet of stringer and bulkead, post some pictures.

reach out to our resident pro glassdave and he'll get you dialed in on it, his advice will help you get great results.

I'm using US Composites Vinylester as well with LBI Vinylester Bonding Compound
https://www.lbifiberglass.com/produc...ring-compound/

I use this calculator for figuring out MEKP
https://vernese.com/mek/

Thanks for all the replies, x2 for US Composites here, I’ll probably go that way.
Speed, I checked the calculator and with Sonic’s dispenser idea, is almost a no brainer.
Especially with Safari’s detailed plan, I feel like I’ve got a good start.
I don’t really know how many feet of stringers and bulkheads I’ve got, but I’ll get some measurements and photos soon. I need 10 posts before they will let me post pix, but will do so soon!
Thanks all!!!

The biggest improvement to my Fiberglassing abilities, and was drastic, was finding and using this dispenser bottle and the ratio chart.

The bottle has a scale on the dispenser section of bottle.

I’ll get a picture of it later today.

I have it taped on the front of my toolbox in the shop.
Simplest one I’ve seen.

Lists cc of catalyst per ounce of resin.

Go to that chart, squeeze that amount into the dispenser section on top of the catalyst bottle and you’re done.

Only variables are ambient temperatures of area you work in which can double or reduce by 50% the amount you used to get it to go off when you want.

And that you’ll get used to it time.

I use the same bottle and i taped this in my engine compartment since i do all my mixing in here.





Also, buy more 1708 thank you think you'll need. Next time I'll but 8" tape because that would have saved a lot of time and effort.
Get a good pair in of scissors or one of those pizza cutter style electric cutters (i used them in my project)

Finally, be ready for a shock when they tell you how much shipping will be for a 5 gallon bucket for resin is.