Epoxy Woes

[JPower210]

Hi Folks-  I love it when a build starts this way-  I have just started on a CS17 kit-  got my sides scarfed together-  on one joint, the one in the middle of the panels, my epoxy is not hardening fully-  I am not sure why, but suspect the mix ratio which I am fixing-  the epoxy is a little soft, able to be dented a bit with a fingernail pushed hard.  I have tried to disassemble the joint to redo, but there is enough of a bond that I am worried that I will destroy wood if I try and take it apart fully, and of course if I do that then I have the issue of shorter panels if I try and recut the scarf- so the question is:

 

Do I pull it apart and take the risk with the potential for having to scarf in another piece?

 

Or...use tape and glass the inside of the joint?  I will be glassing the whole outside so that joint would have glass on both sides.

 

There is enough bond now that handling the long panels and moving them has not caused any separation.

 

Thanks!

 

JP

[Chick Ludwig]

Is the spot that's not getting hard a different batch than the rest? How are you measuring out the epoxy and hardener? If it's the same batch, I suspect that it's not mixed thoroughly. Scrape the sides and bottom of your mixing container often as you mix, mix twice as long as you think you need to, mix BEFORE adding your thickener.

 

If it's a different batch, maybe you measures wrong. If yoy are using pumps, go back and forth between each pump. That is: 1 pump of epoxy resin, 1 pump of hardener, then back to the next pump of resin, and then the next pump of hardener' etc.  If you re-use your mixing container (Ido), be sure there is none left from the last batch other than a scim on the sides.Mixing thoroughly and scraping the sides even more thoroughly applies here.

 

If you just did it last night, maybe a little more time will help it to cure. If it's "fingernail hard", i'd guess that it would.I think that I would just glass either side of the joint, but if you have the extra wood, it would be safest to re-do the scarf. Ahhhh, the joys of building your own boat!!!!

[makenmend]

JP

 " the epoxy is a little soft, able to be dented a bit with a fingernail pushed hard. ''

How long ago was this done and what temprature do you have, how are you measuring your mix's ? what ratio,?

 

 I would be inclined to allow a longer set up if the ratio is only slightly off, Had similar situation earlier this year using medium hardner ( 3 to 1 using pumps), still as you described 2 days later, but did fully cure in a week.

 

MM

[JPower210]

Thanks Chick-  it was a different batch, and actually, different epoxy.  It's not my first rodeo with building so I am fairly confident on the mixing-  I am headed out of town for a couple days so maybe I will give it until I get back to make a final decision.  If I do cut it out and replace, do you see any issue with two scarfs in a fairly small span?  I am a little worried about hull fairness at that spot.

 

For B and B epoxy with pumps-  1 pump to 1 pump or 2:1?   I am using West mostly as I have a bunch, but got some B and B from Hokey Hydro on this site.  I unfortunately failed to ask him about the pumps-  I suppose the right answer is to weigh/measure the output of the pumps and see.

 

By the way- the OB20 you built is an inspiration to me- and that is the next project right after the 17-  Graham is working through a kit for me for the OB-

 

JP

Thanks MM- you are giving me a little hope 

[Hirilonde]

For B and B epoxy with pumps-  1 pump to 1 pump or 2:1?   

 

It is 1:2 ratio by volume.  If you bought the pumps from B&B then you will get this ratio by using 1 pump to 1 pump.  The beauty of these calibrated pumps is that you can set up the jugs next to each other, always pump left than right and lose total track of the number of pumps and still get the proper ratio.  No matter how much I mix I pump left and then pump right every time.  This way even if I space out completely the stuff works properly. 

[Steve W]

It does sound like the mix ratio. I have a chart for mixing by weight for 2:1 epoxies because the pumps everybody loves were not loving me back. 

 

I am not sure if this is the place to post this, but it falls under epoxy woes. I originally bought epoxy from B & B and it crystallized in a month in my 58 degree year round basement shop. I though there might be something wrong and bought my next gallon at duckworks. Same result. I learned to "double boil" heat it in a pan of water to get it fluid again, and store it near my furnace. Last summer I had Geo-thermal heat installed in my house (If you have propane or oil heat have this done ASAP, its like a miracle)  and now the furnace is room temperature at best. I picked up 6 gallons from B & B in February. They heated them all really good in the shop microwave. Last week I noticed all of the gallons had crystallized again. Normally, this wouldn't be a big deal, but the working gallon with the pump solidified and cleaning the pump is brutal. But by shear accident I learned how to overcome that simply.

 

I snuck up into my (wife's) kitchen and got a big canning pot and filled it with water and dropped a gallon in it with the pump still on and read the paper as it came up to heat. I just happened to look over at the pump and notices a drip forming at the nozzle so I went and got a board and a container. I set the board across the edge of the pot and put the container on it wit the nozzle above it and went back to reading the paper. As the water got hot, the epoxy started to expand and get forced up the pump, past the check valve, through the pump and the amount of a few tablespoons flowed out nice and clear and hot. Once I was sure it was not crystallized I let it cool down for a few hours and sure enough, the pump was working great. and I didn't even get sticky. It is important that I mention the gallon was pretty full, so the pump was sitting in the heated epoxy.

 

I did get busted by my wife using her pot and I'm banned from the kitchen for all things boat building, so I'm going to keep my eye out for another pot before I have to live in the shop.

 

Take Care,

Steve 

[Peter HK]

 

 

If I do cut it out and replace, do you see any issue with two scarfs in a fairly small span?  I am a little worried about hull fairness at that spot.

Admission time.

Back in 2006 when I started building my CS17 I made one measuring error (I blame it on that stupid imperial feet and inches nonsense instead of the sensible metric system I was used to).

It meant I ended up with a scarfed panel which was a bit short. I scarfed a short piece on to get it to the right length and it caused no problems other than to my equanimity.

 

If you do have to add a piece it wont be a problem.

 

Cheers

Peter HK

[PAR]

I don't have crystallization issues, simply because I live in a frost free area, but I did long ago. The simplest solution is to store goo and related equipment at room temperature. Now, you Yankees have difficultly with this and the easiest way to fix it is a warm box. A cheap foam beer cooler will do, with a lid. You can just place a drop light in it, with an incandescent bulb and it'll stay far enough above the crystallization temperatures, that the problem goes away.

When I lived in the mid Atlantic area, I made a 3' long x 2' wide and deep foam lined, plywood box. I wired a light base to one side with a 100 watt bulb. This wattage was way more than I needed and a 40 would have done, though on cold days, it kept it at a serviceable temperature, rather than just not crystallizing. I stored everything in this, mixing tubs, applicators, etc.

As you've learned, a water water bath will fix the crystallization issue and I've had to purchase many kitchen appliance replacements, because I've gotten caught. I have a microwave in the shop, that once graced the kitchen, a 50 amp stove that many a Thanksgiving diner once came out of, that now post cures stuff in the corner of the shop. A food processor, a blender, a rolling pin (which nearly was used on my head), several Tupperware bowels and containers, squirt and squeeze bottles, a dishwasher and other assorted items. Look, she will hurt you, so do it while she's a work, trust me on this . . .

[Hirilonde]

I worked outside in a pretend it was heated tent all winter.  I put my resin in a cardboard box lined with wax paper and brought it indoors when I wasn't actually pumping goo.  I found that the hardeners were not an issue, but that freezing temperatures made them a little hard to pump.  So I put them in the box  when it was really cold too.

[JPower210]

An update...  I did a little test with the epoxy pumps-  I thought that they were 1 pump to 1 pump, but they are not- they are the same- I mixed a batch with 1 to 1, and a batch with 1 pump to 2.  The second hardened up just as I would expect it to, the first ended up being like a hard block of silicone.  So, my current plan is to use a heat gun to try and separate the joint, and get all the goo off and try again.  If that does not work, then I will cut the panels and add new scarfs to make up the difference.  Anyone see any issues with the heatgun approach?

 

Thanks.

[Action Tiger]

I know a heat gun will pop cured epoxy blobs right off a concrete floor. I used to have a strip/glass canoe building addiction.

It should get your uncured stuff soft enough to separate. Cleaning all the soft stuff off would be my concern.

Good luck.

[ecgossett]

When you ordered the pumps, did you request a spacer? If not you can create one your self very simply by splitting a small piece of flex tubing down the side to fit around.

 

If you don't have any available measure halfway up for what a normal stroke is, and put a piece of duck tape around to remind you of where to stop. If you want to be fancy put line around, and then ducktape to make a fixed stopper.

 

I just cheat now and weigh most of my epoxy batches. Usually it's not large amounts, and my wife has an awesome kitchen scale that weighs' in grams. I have almost no waste now on epoxy.

[Hirilonde]

When you ordered the pumps, did you request a spacer? If not you can create one your self very simply by splitting a small piece of flex tubing down the side to fit around.

The pumps from B&B came with a spacer or not depending on use (resin or hardener).  Whether they came that way to B&B or whether Alan sits in the back of the shop and puts them on I don't know  

 

West System makes matching sets of pumps for their resin sizes and matching hardeners.  These calibrate to the 4:1 ratio of their product.  So you can do the same left / right technique.  

 

Weighing the stuff would drive me bonkers.  Except maybe for large batches.  If I have a small glue up to do I prep it, set is aside and wait for another to do at the same time.  And if I can't wait I waste a little.

[Howard]

Would it shock anyone to know I do all of those?

 

I have pump sets from B&B. The spacer looks to be 1/2" pvc pipe, cut to a certain length and a slice cut down one side so it will fit over the pump handle stem. I've measured........they are accurate. For the Part A epoxy side, 30 ml. For the hardener, 15 ml. One pump and one pump is then a 45 ml. batch. Without the spacer, it's two pumps.......60 ml.......and one pump.......30 ml.......so combined, that is 90 ml. That is a pretty big batch. For some jobs, 45 is even way too much...........I have small medicine dose cups that I can go as low a 7.5 ml. On the other hand.......if mixing a pint or two for a large glass job........pumping from either source amounts to heavy aerobic exercise..........so for those, I pour into calibrated mixing cups, or weigh.

 

So I'm pretty flexible. All depends on the job. One thing I don't do is get sloppy on the mix ratio. I'm usually paying pretty close attention and to date, have never had a bad batch. Other thing I normally do is save the mixing cup for a day or so to make sure each and every batch kicks off and sets up as I expect it too. If what was left in the cup set up, I assume what went into the project did too.

 

I too pulled a jug of B&B part A epoxy that had been in my basement all winter. Jug was full and it had a pump in it and at least half of it had turned solid. How to loosen that up? I put it in a 5 gallon bucket, then set that in the back of my truck with black bed cover and parked it in the sun. After a couple hours, it had all turned back to normal, including the now cleared out pump.