Epoxy .... "What", is a "Drop"?

[cal40john]

Epoxy is important to get the right ratio. Polyester you can vary the amount of hardener, use less in hot weather.

http://www.fiberglasssupply.com/pdf/.../mekpchart.pdf

[pcmm]

Originally Posted by cal40john

Epoxy is important to get the right ratio. Polyester you can vary the amount of hardener, use less in hot weather.

http://www.fiberglasssupply.com/pdf/.../mekpchart.pdf

With the "pumps" that are available with most brands of epoxy you don't even have to think about it! 2 pumps resin = 2 pumps of hardener! This makes epoxy significantly more accurate for mixing, and predicable too. The biggest down side is once you get above a certain temperature, you might want to switch from "fast" to "slow" hardeners, but I've not found that necessary yet.

[cal40john]

Originally Posted by pcmm

With the "pumps" that are available with most brands of epoxy you don't even have to think about it! 2 pumps resin = 2 pumps of hardener! This makes epoxy significantly more accurate for mixing, and predicable too. The biggest down side is once you get above a certain temperature, you might want to switch from "fast" to "slow" hardeners, but I've not found that necessary yet.

He said he was sloppy with his title, he said he is using polyester resin in a later post, not epoxy. He can vary the MEKP amount to change the reaction time.

[Island Time O25]

West System from WM uses volume ratios so that if you don't have their pumps handy you can still get it right by using small disposable plastic cups or cough syrup cups for measuring.

However, many other manufacturers use weight not volume for measuring which in turn varies between epoxy and hardener (I think epoxy is lighter than hardener). As I was recently re-positioning engine mounts (that's another story which I will tell in detail once I splash, hopefully soon) I used a commercial system from a carbon mast manufacturer (a boatbuilder friend used to work for them so I know the owner and once in a while get supplies from them at their cost-plus which is still about 2-3 times cheaper than WM). That owner told me that the mix ratio for that particular maker is very forgiving and allows for some discrepancy in the mix, which for that particular blend I was using was 56%/44% by weight which actually corresponded to 2:1 by volume. So I just mixed the 1st batch by weight using electronic postal scale, observed that it was exactly 2:1 by volume and did other batches using 2 1oz cups of epoxy to 1 1oz cup of resin.

My boatbuilder friend told me to use the smallest amount for each batch (i.e. do more small batches rather than few larger ones) and only use shallow containers to mix them in. He said 8oz plastic shallow containers from the salad bar are the best, filled to no more than 1/2 level, which I found to be very true as years ago I used 16oz plastic containers and found them to be PITA time wise.

So I kept doing 2oz epoxy/1oz hardener batches in a 8oz container which came out nicely to less than half of the container and allowed at least 20-30mins per batch work time (not that I needed that much time but it was nice to know that I had it just in case).

Actually the prep time - cutting out the mounts, sanding the area to be epoxied, measuring the angle of the motor and the shaft, etc. took about 2-3 days. The actual glassing in time was about 1-1.5 hours per mount. This was only my second major fiberglass project in exactly 10 years.

[Dave Lochner]

For filling holes left over from old fittings I've found West System's Six Ten or a similar product from Jamestown Distributors, Thixio (?).

These thickened epoxies come in a standard caulking cartridge with a special nozzle. Use what you need, and seal the tube. Easy, clean, quick.

The only downside is that the nozzles are single use, but at $2 a nozzle it is a lot easier than the clean up when using a syringe and not all that more expensive than a syringe.

[tinkrman69]

Originally Posted by SteveSails

Are you sure you are using epoxy and not polyester resin? Almost all epoxy resins that I know of specify a volume ratio such as 1:1, 2:1, 5:1 and have a fairly long working time. The polyester resins or fillers like 'Bondo' use only a few drops of hardner and set up very fast if you over do it. Double check what you got and let us know.

Steve

It sounds to me like Polyester resin...wether thickened or not. ten drops to the once at 70 degrees will give you about 15 to 20 minutes. at 90 degrees about two drops/oz. will give you about 30 minutes, mixing 5 or less ounces per batch. the larger the quantity the faster it will kick. I've mixed Qt's with as little as 10 drops total per QT. keep your resin in the shade or chill it before mixing. filling holes with resin, isn't very efficient. thickening it to a past and using cream hardener would work better and make less mess. Unless your filling holes in wood or epoxy constructed stuff I wouldn't afford the expense of epoxy for filling holes ... even still I would use a paste rather than resin. it wouldn't do a better job than poly in anything other than wood or epoxy.

[guyrj33]

Are you using Polyester resin, your description sounds like polyester not epoxy.

[TrentePieds]

Yep - OP sez he bought "resin AND epoxy. Two different breeds of cat! They require drastically different handling.

Resin - meaning polyester resin thinned out with styrene solvent - is for laying up GRP, not really for filling holes, unless the hole is so big that a laid-up patch is required.

For filling smaller holes, where only a 'bung" is required (a bung that will not be subjected to significant forces) polyester resin thickened up with talcum power is sold under such names as Bondo and White Lightnin' for auto body repair. Far, far easier to use for "small hole repair".

Mix it on a bit of disposable plywood, or cardboard or anything else that's disposable. Lay down a gob of Bondo the size of a golf ball. Next to it squeeeze out a mini-gob of hardener (it comes as paste in a tube) the size of a pea. Mix the two with a disposable stick - tongue depressor, ice-cream stick - whatever. The grey Bondo will pick up colour from the hardener to indicate that the hardener has been mixed in well and uniformly. Apply with a polyester trowel used for taping drywall.

Never mix more than a golf ball's worth. If too little, wait for the applied goop to harden, the sand to contours, then do another golf ball, and so on till you're good. Never let anything that has touched hardener or the poly/hardener mix go ANYWHERE near the can of fresh Bondo. If you do it will harden in the can, and there goes five and twenty bux :-)

Best that the ambient temperature should be about 60 degrees F. At 90, this stuff "kicks off" really fast. Once you feel it begin to go gritty, chuck the unused portion and start a new "ball game".

Get you feet wet working with this stuff before you "graduate" to lay-up resin - let alone epoxy :-)!

TrentePieds

[SURV69]

Originally Posted by SURV69

Jim ...does that mean that at 95 degrees, a drop migh t be bigger? If so, I was getting a double whammy

Steve: I'm afraid I used epoxy as a generic term ... it's polyester resin ... for a polyester boat

ALWAYS ... someone wanting to jump on a poster for simple misuse of a word ... as a kid(55 years), we called anything that required a bit of this and a bit of that as "epoxy".

It was wrong then and it's wrong now ... I think some posters rather enjoy picking things apart to adnauseum(sp), just for whatever reason ... but then, not actually addressing the original question.

If you know your epoxies from your resins, you already know that I am not talking epoxy, or that if I am, the epoxy would possibly take forever to set ... if ever.

So ... get with the program as they say ... when you know what the OP obviously didn't know, don't spend so much time making that fact so abundantly clear ... I get the picture ... it POLYESTER RESIN, I picked POLYESTER RESIN, because that's what my boat is made of ... and more importantly ... it's a lot cheaper ...

message received ...

[TurninTurtle]

Well... lets add to the confusion...

About half of the Epoxy bottle pairs I have say Resin on one and Hardener on the other.
The rest just say Epoxy on one and Epoxy Hardener on the other.

So the product manufacturers seem to think there is Epoxy Resin.

***************

The final answer to the original question:

Less catalyst and pre-cool the resin and/or smaller batches will give more working time.

[leftbrainstuff]

A drop is a scientific volume measurement. A drop can vary in size based on method of application or as a specified volume. There is no universal standard volume of a drop.

For two part polyester resin measurement I use either the manufacturer's suggested applicator or a pippette.

From a tube you may find that a drop is a result of the surface tension and ambient conditions. A drop therefore will be the smallest contiguous blob that leaves the nozzle. Rather unscientific.

Even making a cake requires specialized knowledge of weights and measures.

West system epoxy products have a 5:1 (or is that 6:1?) Resin to hardener ratio. Polyester tends to use drops of hardener. (Actually a catalyst that kicks off the formation of the long chain monomers that crosslink and 'set')

I recently used tap plastics two part epoxy for a honeycomb panel build hard dodger. It has a 1:1 resin to hardener mix and can be dispensed by pump without measurement. Much faster than using West product.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[knockabout]

epoxy 5 to 1 ratio 5 spoons of resin 1 spoon of hardener/slow-normal-fast hardener


to mix 180 marine epoxy with drops are you working on micro patching


perhaps you are using polyester /sets in 15 to 20 min

[foufou]

First off as others have mentioned, epoxy is a better resin for this job. I often use a metal can for my epoxy. Aluminum is best for transferring the heat produced by the exothermic reaction to the outside world. give a few more minutes of working time. With the appropriate hardener the heat/work time should not be an issue. have fun

[mawtty]

POLYESTER RESIN!
Use a little less catalyst and the reaction is slower.
Temperature: the reaction is exothermic. With too much catalyst it can 'boil' in minutes.

[Island Time O25]

Cost, working time, health and other issues and considerations aside epoxy is a much better media to work with than poly for the simple reason that it adheres to poly but poly does not adhere to epoxy. So if you're reworking an area which was previously patched up with epoxy you just can't get the poly to adhere to it properly.