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Epoxy Tricks


Howard
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Storing epoxy hardener in the same cabinet as solvent based materials is dangerous.  The resin is a solvent based material and is flammable.  The hardener is an oxidizer.  Adding electricity and heat to that cabinet makes it significantly more dangerous.  OSHA prohibits all of those (stored together, heat in the cabinet, electricity in the cabinet) in commercial establishments. It wasn't clear what exactly you stored in the cabinet, but thought you might want to know Bill.

 

Dave:

 

Are you saying OHSA prohibits storing epoxy resin Part A and hardener Part B together in a heated cabinet? The West System's epoxy book suggests doing that very thing by storing them in an old refrigerator with a light left on. If true, they need to revise their book and get that out of there. A lot of people are doing it. Mine are stored side by side, but on an open shelf.

 

Part B (for most epoxies anyway) is the catalyst, which is an oxidizer.  Part A, and all oil based paints, plastic coatings that are not water borne, alcohol, mineral spirits, acetone, xylene, toluene, etc are solvents or solvent borne/based materials and therefore flammable.  The storing of oxidizers and flammable liquids together in the same cabinet is prohibited by OSHA. 

 

Heating any cabinet containing either by a source that could reach ignition temperatures is prohibited.  Running an electric circuit through the cabinet is prohibited.  These are because putting a possible source of ignition in a flammables cabinet is dangerous.  Even if you use a metal air tight cabinet when you have the solvent and the oxidizer together you are supplying the oxygen. 

 

OSHA wants you to store solvents in metal containers by themselves.  They want you to store oxidizers by themselves in a separate metal container.  They want no source of possible ignition in any of them.

 

Compared to many other reacted materials epoxy is a slow reaction.  Some say it is therefore very safe.  As an individual you are not accountable to OSHA, only places of employment are.  You can choose to do what you want.

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Howard, most of the fillets on a boat will be at obtuse or acute angles, which is why you're seeing what seem to be large radius spec's. I use the 3:1 rule for my plans, but on racers, I have reduced this (on small craft) to save a few pounds of goo. There are 3 types of fillets to employ, heavy structural, light structural and cosmetic. The cosmetic fillet is as the word suggests and just to make things pretty and easy to clean, so a big radius is usually preferred. A good example of this would be seat boxes in a cockpit. Washing out a cockpit is much easier with a generous radius at the sole/seat box interface. I find a CD works good for this, though you'll use a lot of goo. To prevent this I'll place a triangular hunk of wood or foam in the corner first, then fillet over it. Contrarily, I might have a structural fillet holding the seat box down and a cosmetic fillet over it, to clean it up. Both of these techniques use about 1/2 as much goo, then a straight CD shaped fillet.

 

Fillets serve several functions, which is why the 3:1 rule is popular. Joining the pieces is fairly easy with a small fillet, but this doesn't address the issue of stress concentrations, which is one reason we use larger fillet dimensions. A 1:1 fillet may be enough to hold things together enough where the fail line is in the wood, but it doesn't prevent a stress riser from forcing the joint open prematurely. Boats experiences lots of flexural and impact loading, which causes load paths to vary and rise dramatically, frequently. This cyclic action is what breaks stuff and if you have natural stress concentrations, these are the locations things will break. If you can slow the "ramp up" of a load path change, these can be mitigated to a large degree.

 

The other two fillets I mentioned are structural, the light structural fillet usually doesn't have a fabric skin, while the heavy structural fillet does. The differences are mostly filler material related, though the fabric does play a role, mostly in compression and tension, but also to help deal with load transmission transitions. As a strain moves down a panel and meets a perpendicular structural element, the load will naturally want to transition to this element. If the change point is abrupt, such as that with a small radius fillet, or even a cleat, glued to the panel, the strain at this intersection rises dramatically and the "entrance" or "exit" of this dramatic increase in density will be the failure point. So, the fillet radius slowly increases the transition point to the higher density area at the entrance, and slowly decreases the density point on exit, mitigating the hard point to a large degree. This is especially true with acute angle transitions.

 

This is the very reason that most boat manufactures are now using foam or polyurethane beds, under bulkheads and other structural elements, before the tabbing (tape/fabris) goes on. The load paths are preserved, yet the huge radius, provided by the staggered overlap in the tabbing, makes the transmission relatively smooth.

 

My latest testing has shown for small craft (dinghies, canoes, kayaks, etc.) fillets aren't as necessary for strength and stiffness as you'd think. I've used triangular bits of wood, glued in place, substituting the fillet on the inside of the joint, with tape on the outside and this seems to be lighter and just as strong. There's less "goo factor", but more wood working and fitting. If a cosmetic fillet is applied over the wooden fillet, a clean, neat and seamless joint, with less goo, but the same strength and stiffness.

 

Lastly are safety margins. You may have a 1:1 or 2:1 fillet that gets the job done, but how much "margin" does it have? If the 2:1 was extended to 3:1, would the result be a longer ramp up to the hard point, delaying failure and do you expect the builder to always build to your spec's? Considering the widely variable possibilities, in a back yard build, error on the side of too much fillet, seems a reasonable precaution.

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I've been reading this thread with interest, and use some of the techniques mentioned, which I'll talk about further down.

 

But I really really do not understand the dislike of pumps. I've been building boats using epoxy since 1976, and have ALWAYS used  pumps. First from the Gougeons, then MAS, and RAKA and SYS 3, and epoxy from Graham  for the last 8 or nine boats, and many repaIr jobs, with absolutely zero problems, unless I myself did something stupid ( and I  HAVE done that :wub: ).

 

I do check the calibration often, and if the pump isn't putting out what it should, I scrap it and put in a new one- They aren't but $10 bucks.

 

I've never weighed a batch in my life.

 

So I'm at a lost as to the dislike.

 

Now- on the other methods.

 

I use the clear cup, marked with 2 parts then one more, or 5 and one more (West), for small  batches Works quite well.

 

Another method is using a straight sided container (MUST be straight sided) and marking a stick with the ratio. Pour resin to the first mark, hardener to the second, stir and go. And I have mixed TINY batches that way- the little cup that's found inside the lid of a spray paint can is perfect.. I've used as small as 1/8 and a 1/16th  on a very small stick.

 

On larger batches, like when fiberglassing a hull, I'll use washed out tin cans, and maybe 4 or 5 inches or more of resin. Yes- with a 2-1 ratio this gives 6 inches or more of resin once mixed. If on a large job I'll pre-pour 6 or 8 (or more) cans with just  resin, so when I need more it's simple to add hardener, and keep going. I glassed the hull of a Princess 22 this way, working alone, in a shop that was at 104 degrees-- and believe me, ya gotta move FAST :rolleyes:

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I'm using B&B's pumps, have been since I started my project about May 1st '13.  Until today I had had only one problem.  I put it (the pump) aside and used a replacement to finish the job I was in the middle of and afterward cleaned the offending pump, solvent (acetone) etc. and it seemed to be fine, check valve ball moved freely so  set it aside and haven't tried it since.  Today I went to mix a batch of type A and slow Type B which had not been used in a while and the pump didn't pump; I set it aside and tried the "fast" jug (with it's own pump which I'd been using almost daily for the last several weeks, it didn't work either.)  I went back to the "slow" pump, cleaned it up and it still didn't work.  I assume that the swab "thingy" (the thing that in bicycle pumps we called the "leather" which had to be oiled occasionally to keep them working, in the oil field we called it a "swab") is not sealing properly.  (I keep a pump in a jug of "slow" hardener and one in a jug of "fast" hardener)

 

Question:  Are these pump that short lived?  Doesn't seem to be much to be done for the "swab".  I'm leaving it (them) overnight in a warm room.  Hoping that will help.

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DON'T use acetone. Acetone will screw up things inside the pumps. Use white vinegar. Vinegar is acetic acid and will emulsify uncured epoxy. Then you can flush with water and dry.

 

And no, they are not that short lived, normally. I've had some go a year or two, in warmer conditions

 

You can clean brushes in white vinegar also. I keep a can full on the bench, and just drop the brush in between uses. Shake it out well and it's good to go, for at least a few days. After that, toss and start a new one. Rollers I stick into a baggie and shove in  the freezer over night. Works for a day or two, then they need to be tossed.

 

I find very few uses for Acetone

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Thanks for the info Charlie.  I do use vinegar for most clean-up.  The stuff is amazing.  Just thought in this case the acetone might be better.  My bad!  I assume it damages the (whatever) plastic? in the pump?  Believe me I will cease and desist with the acetone!  That probably explains the problems I've had in cleaning syringes with the stuff.  It seems to attack the rubber or neoprene whatever it is on the plunger.  After a few hours they seem to work ok though.  .........I read somewhere that one should follow the vinegar with with a wipe down with acetone. 

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The only thing I use acetone for is cleaning oily surfaces, such as oily woods like teak before applying a coating or glue (epoxy) to them. I freeze my chip brushes in baggies between uses.  It gets me 3 - 6 uses over a couple days.  My wife has gotten used to that.  Not sure what she would say to finding rollers in the freezer.

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I've had pump issues also, I've tried alcohol and acetone and found they won't free the ball very well. Thanks for this info. I learn something new every day. Acetone eats gloves also.

Try pulling the pump out of the can and heating it with a hair dryer on low heat and slowly from a distance. Wives like this almost as much as Charlie's roller freezing technique :P

 

I haven't had any issues with acetone eating gloves, What material gloves are you referring to?

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It really doesn't eat the blue gloves but they seem to get very soft and tear when using acetone. Not a big deal, but I was just wondering why. I tried vinager today works great for resin, but seems to not get along with hardner when I tried in a hardner pump. I think I detected some foggy gas  when I poured vinager into the hardner pump tube.  Alcohol seems to work better in that pump.

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Most of my posts have been in the manner of asking for help.  Today I have a couple of ideas that might prove helpful to someone out there:

For those who may not have thought of this, in the process of cleaning up my pumps and trying to get them working again, I discovered a handy trick: if you have a spare or back-up pump and an empty resin jug, pour a little vinegar in the jug, swish it around a little, discard, repeat a time or two then fill the jug with clean vinegar, insert the pump and you've got a very handy place to store the pump as well as a tap for the stuff.  Especially handy when your hands are covered in goo and you need a squirt of vinegar to clean up.  I also discovered I have a total of six of those pumps two of which came from something unrelated to boat building but identical to the B&B versions.

 

BTW, one of the pumps that I disabled with acetone yesterday is working fine today.  I think the pump soaks up some of the acetone which changes the characteristics of plastics but after a while the volatile acetone evaporates and the plastic recovers.  Just a guess; I am definitely not a chemist!

 

One more thing:  I think by the time I've finished my boat I will have established a number of pumps per square foot needed.  Point being, for beginners I suggest to from the start, keep a record of the size of each job in square feet and the number of pumps used.  You should pretty quickly learn how much to mix for each gluing session.

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Resin in cool temps will form "crystals" which will appear as white flakes in the resin. B&B resin seems less tolerent to cool temps than WEST and you may see a copuple inches of white cloudy goo settle to the bottom of the jug. If you attempt to pimp out a squirt all systems clog. Solution: put resin jug in a pail of worm/hot water. I set it up in the kitchen sink and let freshly heated water trickle into the pail to speed things along. Soon the resin will clear and you're good to go. 

 

  Bottom line - keep your resin in room temp = 70+ F.

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Another epoxy trick which has nothing to do with boats, unless it is a flying boat (seaplane). I used WEST to glue a 1/32" thick balsa skin to a foam core wing. The foam core I cut out of a bead board block with my hot nichrome wire rig. This is a small plane - 1/2 size "Tiporare" aerobatic pattern plane - with a 32" wingspan so weight was a concern and 6 lb/cu ft balsa soaks up WEST like a sponge. Trick = I gave the balsa skin a quick coat of 50/50 thinned nitrate dope which semi-seals the wood but leaves plenty of grab tooth for the epoxy. Then I filed 1/64" nootchs about 1/8" apart of the edge of an expired AARP plastic card and mixed goo. Goo is spread out with smooth edge then screeded off with notched edge leaving thin ribbons of goo, plenty to glue skin on foam. Foam core with both sides skinned is put in  my wing press and gently squished for the cure. Figure roughly 400 squre inchs of glued on skin with less than 15 grams of epoxy. cool . . .

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 Solution: put resin jug in a pail of worm/hot water. I set it up in the kitchen sink and let freshly heated water trickle into the pail to speed things along. Soon the resin will clear and you're good to go.

This thread is getting very long, but it also contains a lot of good stuff.  I therefore suggest we start a new thread for all the epoxy tricks that spouses of epoxy users like a lot.  With this one we have several already.

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LOL- When I HAD a spouse here, she would get involved in things like this- WE, rebuilt the carb on the out board, in the kitchen

 

And the dinghy in the living room was HER doing. It was really windy and was messing up her varnishing, so she brought it inside..

 

Kinda wish she was still around :rolleyes:

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Charlie, I think my dislike of pumps come from the coolness of my shop. I had a pump stop pumping in the middle of a job when I was mixing small batches to keep working and hated to disrupt my work. If you've ever tried to clean crystalized epoxy out of a pump it is no fun. I have three gallons of epoxy that are totally crystalized sitting in my shop that I need to heat up to reuse. Thank goodness they don't have a pump in them. My guess is you living down south in a warm climate contributes to your success. I will say that before I bought 2:1 epoxy, I'd used West System for years with no crystallization, but I like the 2:1 stuff better and its less expensive.

 

Take Care,

Steve

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I've had pump issues also, I've tried alcohol and acetone and found they won't free the ball very well.

Try pulling the pump out of the can and heating it with a hair dryer on low heat and slowly from a distance.

 

I live in RI and I still find it worth while using pumps.  This does not mean everyone should like them.  It is all a matter of developing habits that make them work, like storing in a warm place between uses.  If using them is important you find a away.  If it is not, then you find another way.

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Is it possible that the melting temperature of the crystallized stuff is higher than the crystallization temperature?  I moved several jugs of the crystallized stuff from the cold concrete floor of my shop to the warm mechanical room (water heaters etc) of my house 78 degrees a few days ago thinking for sure it would be back to liquid in a day or two.  Not so.  Am currently waiting on it to finish liquifying in a hot water bath.  Probably should have put some insulation between the jug and the concrete floor even inside.  I'll try that and report back.

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