Hello wooden boat folks,

I have started a wooden drift boat build and ran into (created) a problem I would like some advise on. I am using West System 105/205 epoxy and using the 300 mini pump set. I checked the calibration by volume, I could not find a scale, it seemed very, very close. Although, I now see that something is terribly off. I have used about 1/2 gallon of resin and a full quart of hardener! Way off the correct ratio. I have used this improper ratio on all of my scarph joints and to glass one side of a side panel. This mix worked well on three test scarph joints, the plywood broke not the joint. The epoxy seemed to behave fine, it did not cure to quickly or slowly and its application properties were very workable.  The problem will stop here, I will find a set of scales or measure each batch by volume.

My question are these:

1) Will this ratio have sufficient strength? Or will the remaining fiberglass work provide enough strength to compensate for the improper ratio?

2) If I must break these parts apart and start over, how would I go about that?

Any other insight would be appreciated! Thanks in advance for any help.


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Dorf & Brad, thanks for the vinegar tip.....good to know! Bye bye acetone!

All, good stuff. Thanks for the replies, I'm gonna try that vinegar trick. I am adding a 16" wide strip of glass to each side of all of the scarfs and call it good. I bent all of the panels to a more sever degree than they will be on the boat, no signs of any distress. Feeling much better now.

As an aside....I called West System last Friday after I discovered the problem and left a message. They called back Monday morning, of course I was in the duck blind with a crappy cell signal. We finally made contact yesterday.

Two observations from that conversation. First, the tech (Tom P) really knows his stuff! He diagnosed the problem to a check valve in the resin pump. He also had strength values for improper ratios, very helpful in determining what my next step would be. Second, this company really stands behind the products they make! Had I got the chance I was going to ask them for a new quart of hardener, before I could, Tom told me they were sending a gallon of resin, a quart of hardener, a new set of pumps and a couple yards of glass cloth!

I cannot remember the last time I called tech support and found them to be helpful, let alone a company that stands behind their products. I was very, very impressed and felt they deserved some public kudos.

THAT is very cool. So good to hear a take like that. Kind of sad how few companies understand the value of trying to make things right.
I always mix by weight. You are far more likely to get an exact ratio. Years ago on my first boat, I ran short on hardener while doing the hull of the boat. At the time I didn't understand measuring glass to weight ratios and was winging it. A buddy bailed me out mid layup with a qt of west fast hardener. It even included a pump. I thought...sweet. Well, long story short, when you have a process that works don't go messing with it mid project. I used the pumps and wouldn't you know it one of my flow coats didn't kick off. Bad mix. If you understood the wasted energy I spent scraping gooey resin, wiping with vinegar, scraping more, wiping with acetone, scraping some more.....etc etc you would never use those pumps again.

One thing to note is that the ratio by weight is slightly differant by volume. Be sure to check whatever it is for your resin.
I use resin research which is 2:1 by volume or 2:.9 by weight. The easiest way for me is to understand what batches to make. I like stuff that is easy math.
My typical batches are like
10g resin/ 4.5 g hardener= 14.5 g total
20g resin/9 g hardener= 29 g total
40 g resin/18 g hardener= 58 g total
100g resin/45 g hardener= 145 g total
200g resin/90 g hardener= 290 g total
Or some mix of the smaller amounts depending on what I need.

If I go over, I use the 2:1 ratio then to balance out. I.e. Extra 2g resin, add 1 extra g hardener and your total point to hit goes up by 3 ( counting the extra 2 g resin and extra 1 g hardener). What the pumps might be better for is a mess free dispenser. Pump your cup on the scale and pump you resin is slowly till you hit your target. I honestly pour straight out of gallon jugs, with a ketchup type west dispenser you could have no mess and check that you ratios are correct. In theory they should be right, but the scale will tell you wether you have a correct mix. If I would have done that on my first boat I would have avoided days of scraping and nasty chemicals.

These mixes all fit in a 16 oz plastic keg cup form the dollar store. I use a cheap harbor fright gram scale. I keep it in a ziplock bag so it doesn't get all gooey. Much more difficult to mess up a mix this way. Pretty easy too.

Also, don't waste resin. It's expensive, and adding extra to your layup doesn't add any strength. For a hand layup the ratio of glass/resin is 1:1. If your glass weighs 200 grams, you need 200 grams total of resin. The math for that looks like
Total weight /2.9 = A
Resin= A x 2
Hardener A x .9
Double check your math before you mix!


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