Simple way to measure epoxy

Discussion in 'Fiberglass and Composite Boat Building' started by JEM, Jul 20, 2006.

  1. JEM
    Joined: Jan 2004
    Posts: 299
    Likes: 3, Points: 0, Legacy Rep: 38
    Location: Greensboro, NC

    JEM Senior Member

    Epoxy is made of 2 parts: Resin and Hardener.

    Most epoxies call for a 2:1, 3:1, or 5:1 ratio of Resin and Hardener. One way to measure the appropriate amount to use metering dispensing pumps that are offered by many suppliers. Another method is using a graduated measuring cup.

    These pumps typically are very reliable but they do break down after a while and let air into the pump. This causes the pump to "burb" and give an inaccurate amount of Resin or Hardener. So if you don't have reliable metering pumps or just want to use a more visual method, here's an easy way that doesn't require using pumps (or purchasing graduated measuring cups).

    Helping in the demonstration is our 8-year old assitant who happens to be the "E" in JEM (JEM Watercraft). :D

    Please note: This method shows how to mix a small amount of epoxy with a 2:1 Resin-to-Hardener ratio. This can be adjusted for more epoxy or different ratios.

    You'll need some clear plastic cups and a permanent marker.

    [​IMG]

    Place one cup inside another.

    [​IMG]

    Decide how much total epoxy you want to mix at one time. In this example, we selected about 1/2 of the plastic cup.

    With the marker, draw a line on the outer cup. Label it "H" for Hardener.

    For a 2:1 ratio, you have 3 total parts: 1 part Hardener and 2 parts Resin. So we marked our line about 1/3 up toward half the cup. If your epoxy is 3:1, then you'll have 4 total parts. Mark about 1/4 the way up.
    [​IMG]

    In this next part, we use water. Much cheaper and easier to clean up if you make a mistake.

    With an empty cup still inside the marked cup, fill to the marked line.

    [​IMG]

    Remove the inner cup and set aside. Measure 2 more parts so you have a total of 3 equal parts.

    [​IMG]

    Place a cup back inside the marked cup, and pour the 3 equal parts into the cup.

    [​IMG]

    Mark another line on the cup and label it "R" for Resin.

    [​IMG]

    So when your ready to mix, first fill the inner cup with Hardener up to line H, then fill with Resin to line R. Remove the inner cup and mix. Save the marked cup for the next batch.
    [​IMG]

    Easy! :D
     
    1 person likes this.
  2. lewisboats
    Joined: Oct 2002
    Posts: 2,329
    Likes: 126, Points: 0, Legacy Rep: 1603
    Location: Iowa

    lewisboats Obsessed Member

    Very Slick...even I could follow that one.

    Steve
     
  3. CET
    Joined: Sep 2005
    Posts: 114
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Utah

    CET Senior Member

    Very clever! Thanks for sharing this.:cool:
     
  4. JEM
    Joined: Jan 2004
    Posts: 299
    Likes: 3, Points: 0, Legacy Rep: 38
    Location: Greensboro, NC

    JEM Senior Member

    I didn't come up with this idea. I read it on a couple different build forums. But I haven't seen it "demonstrated" anywhere.

    My daughter was wanting to do something for my webite, so it was a quick but useful project. Lots of other ways to measure and dispense epoxy.
     
  5. djwkd
    Joined: Jul 2006
    Posts: 380
    Likes: 2, Points: 18, Legacy Rep: 51
    Location: Newcastle-Upon-Tyne

    djwkd Senior Member

    Hi,just wondering if you can use just paint or just varnish,are if not what is the best thing to apply to waterproof a boat?:)

    thanks.
     
  6. sal's Dad
    Joined: Apr 2005
    Posts: 109
    Likes: 7, Points: 0, Legacy Rep: 85
    Location: New England

    sal's Dad Atkin/Bolger fan

    After a discussion on some other forum (yahoo Bolger? Duckworks?) I made a simple balance scale yesterday:

    - A scrap of wood, 3/8" x 3" x 30" (size doesn't matter - that's just what i used)
    - Using a pencil or whatever as a fulcrum, find the center of gravity (middle of the see-saw, where it balances)
    - Put 2 screws through the board, so it will balance on the points. Shave one end as needed so it balances well enough for your tolerance.
    - Draw a line across near one end of the board
    - Measure 1/5 that distance, on the opposite side of the fulcrum, draw another line here (for a 5:1 mix)
    - Use 2 identical cups - one on each line. Put any amount of resin in the closer one, then fill the further one with hardener, til they balance. That is your mixture.
    - Pour back and forth between the cups, mixing. No need to measure anything.
    - If you are a stickler for accuracy, draw a third line, 4 measures out on the epoxy side, so that 3 empty cups balance perfectly, when placed on the lines. Leave the 3rd cup empty.
    - Write instructions to yourself on the board.

    I couldn't believe how easy this was, after all those years with d****d pumps, and inaccurate measurements!

    Sal's Dad
     
  7. Salty Dog
    Joined: Mar 2006
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Sunshine Coast, BC, Canada

    Salty Dog New Member

    sal's dad - Sorry, but NO. While your approach is correct, there's an error in your logic. When epoxy mixing ratios are given, they are for volume, not weight. Part A and Part B do not weigh the same therefore the ratio changes if you want to mix by weight. And to further complicate the issue, the weight ratio changes by epoxy manufacturer. Mine worked out to be 1.68:1 for the 2:1 epoxy I used. You could use a kitchen scale and weigh equal amounts of your Part A and Part B to determine the weight ratio or email the manufacturer and ask for the data. To build the balance, I took a piece of scrap ply 18" x 4" and drilled a cup size hole in each end. I put 100 pennies in one cup and 168 pennies in the other. Then I found the balance point and routed a 'v' groove across the board for the fulcrum. I had less than 3 oz resin left over after mixing 3 gallons of epoxy in batches as small as 2 oz. I then got fancy and added a microswitch and light that indicates when to stop adding hardener.

    [​IMG]
     
  8. sal's Dad
    Joined: Apr 2005
    Posts: 109
    Likes: 7, Points: 0, Legacy Rep: 85
    Location: New England

    sal's Dad Atkin/Bolger fan

    Yes, Salty Dog, of course you are right; the distances from the fulcrum need to reflect the Mfr's recommended ratio - whether weight or volume. I have been using WEST System for many years; their container says 5:1 by either weight OR volume.

    My point is that you don't need to get fancy; just drawing the lines in the right place on the board gets you the proper mix. The holes in the board are a nice touch, but they limit you to specific containers. And I am a lazy slob, prefer driving a couple screws to all that fancy router work ;-)

    Again, using the balance to put the proper amount directly into the mixing containers is far, far easier and more accurate than trying to get precise volumes into various disposable cups.
     
  9. JEM
    Joined: Jan 2004
    Posts: 299
    Likes: 3, Points: 0, Legacy Rep: 38
    Location: Greensboro, NC

    JEM Senior Member

    You're either watching epoxy fill to a line or watching a lever balance. I don't know that I'd call one easier than the other.

    Luckily, hyper-precision is not required with 2:1 or 3:1 ratios. Gets more critical with 5:1.

    But different strokes for different folks.
     
  10. jimslade
    Joined: Aug 2005
    Posts: 304
    Likes: 3, Points: 0, Legacy Rep: 27
    Location: north Markham

    jimslade Senior Member

    automotive paint suppliers will give you a mixing stick that has all the ratio numbers on the stick. I use one every day. Also they sell paper cups that are perfect cylinders.
     
  11. Raggi_Thor
    Joined: Jan 2004
    Posts: 2,457
    Likes: 64, Points: 0, Legacy Rep: 711
    Location: Trondheim, NORWAY

    Raggi_Thor Nav.arch/Designer/Builder

    Very nice.
    I use a digital kitchen scale :)
     
  12. Russ
    Joined: May 2006
    Posts: 47
    Likes: 3, Points: 0, Legacy Rep: 17
    Location: La Ceiba,Honduras

    Russ 60 year plastics veteran

    Heres another Epoxy measuring tip. Check the can and if the ratio is by weight or volume, most unfilled systems are, simply pick up a clean stick and mark it. If the ratio is 4 to 1 mark it , for example mark 4 inches then 1 inch, then pour to the marks. It doesnt matter how much or how little you mark, it will be correct.
     
  13. lewisboats
    Joined: Oct 2002
    Posts: 2,329
    Likes: 126, Points: 0, Legacy Rep: 1603
    Location: Iowa

    lewisboats Obsessed Member

    but that only works if you are pouring into a cylindrical or cubical container.

    Steve
     
  14. Raggi_Thor
    Joined: Jan 2004
    Posts: 2,457
    Likes: 64, Points: 0, Legacy Rep: 711
    Location: Trondheim, NORWAY

    Raggi_Thor Nav.arch/Designer/Builder

    Vertical sides at least :)
    Or constant sectional area :)
     

  15. lewisboats
    Joined: Oct 2002
    Posts: 2,329
    Likes: 126, Points: 0, Legacy Rep: 1603
    Location: Iowa

    lewisboats Obsessed Member

    S'what I said...Innnit? Hick!

    Steve
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.