Preview: Mastering Epoxy with Russell Brown, Part 3 – Fillets, Hardeners & Fillers

13 Responses So Far to “Mastering Epoxy with Russell Brown, Part 3 – Fillets, Hardeners & Fillers”

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  Dennis Annotti says:

  What ratio of filler is recommended for making thickened epoxy for glueing parts together. Russel recommend 406 And 404 but does not give ratios.

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    Nate Rooks says:

    Hi Dennis –

    We’ll get Russell to go deeper into bonding in the near future, but right around 6′ in this video he gives his recipe for fillers – 2 parts 207 : 2 parts 206 : 1 part 204 – as the magic mix to get the right thickness, consistency, and sandability.

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  Alex Zimmerman says:

  I’m in the midst of building my 8th ply & epoxy boat, but there is always something to learn. These videos from Russell Brown are excellent for fine-tuning my technique.
  One little tip I discovered, for thoroughly mixing the dry fillet mixture, is to use a length of small chain as an agitator in the mixing container. It makes the mixing go more quickly and the result is more homogeneous, as the colloidal silica tends to stay in clumps otherwise.

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  Taran Card says:

  Hey, these are great videos:
  when I have done this on small boats i laid my fillets and immediately applied a tape of cloth which was painted in with thin epoxy. this meant i did not have to do intermediate sanding..

  is there a reason you don’t do this?

  Thanks again.

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    Nate Rooks says:

    Hi Taran – Glad you like them!

    In this case, Russell had already fiberglassed all of the panels before assembly, as seen in Part 6 of this series. He was also trying to make this PT-11 as light as possible, but the epoxy fillets bonded to the fiberglassed panels are plenty strong on their own.

    Your way sounds great too – certainly extra strength if needed in that application.

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  Trevor Burdon says:

  Excellent videos but surprised to see Russell hand measuring the filler. Easy to spill and have it disperse in the air.

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    Nate Rooks says:

    Trevor – good point. He was doing this very close to an exhaust fan.

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  lee davis says:

  I’m really learning a lot from this series even though I have been “messing around” with epoxy for over 30 years, building and repairing composite boats. I’m preparing for my spring project now rebuilding an old Panga hull using coosa and honeycomb cores for decks and bulkheads. These filleting skills are going to come in handy. I’m wondering how to source the material for the chisel sticks? I heard Russel mention Mcmaster Carr , can we get a part # or description of the material and how he works it to the correct shape?

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  Patrick Daniels says:

  Loving these technique tips! Also feeling bad for Russel Brown cos he should be sailing!!

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  Ian Hendrie says:

  I am really enjoying this series. My takeaway from Russel’s videos is that I have to slow down and focus. Thanks.
  On an aside, denatured alcohol is not commonly available in Canada as a solvent, but is sold as alcohol fireplace fuel at stores such as Canadian Tire. I find it much better than acetone.

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  Michael Mittleman says:

  Mastering Epoxy with Russell Brown contains a virtual treasure trove of wisdom and technique. Well done.

  Here are some things that have worked well for me:

  1. Denatured alcohol is a solvent for WET epoxy. When cleaning tools such as fillet sticks, a few swipes across an alcohol-soaked rag will remove the epoxy residue.

  2. One item that may be superior to chisel sticks are inexpensive putty knives. Different widths are readily available and they never lose their edge. After use, wipe down with alcohol.

  3. One technique that leaves a glass-like finish to fillets is to use a gloved finger that is wet with alcohol and trace the fillet surface. A small cup with alcohol in it allows the builder to easily refresh the finger tip with more alcohol. The time to perform the smoothing is critical – aim for the point when the surface is just starting to cure, about 45 minutes after the fillet has been applied.

  4. Instead of dipping one’s hand into epoxy filler tubs, use another stir stick like a spatula to transfer filler to the epoxy cup. This keeps the filler powder from adhering to gloves.

  5. Get a bundle of wooden paint stir sticks to mix the epoxy, transfer fillers or shape into fillet sticks. They are very inexpensive, effective, reusable and disposable.

  I have never seen fillet seams that do not require subsequent sanding. Sometimes it is a little sanding and sometimes a lot – but sanding is almost always needed. Some areas of filleted joints are challenging to sand properly, i.e. to be smooth and uniform in shape. I hope Russell Brown can spend more time discussing this and sharing techniques and tools.

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    Nate Rooks says:

    Michael – these are great tips!

    A couple of notes:

    – Russell makes his chisel sticks with an angled edge, which helps to pull up the residue and pull it away from the fillet. A putty knife works well (and could be cut to a similar shape), but maybe not quite *as* well as these custom bits.

    – Paint stir sticks are great, and even better when making sure that the bottom is square (many paint stir sticks have rounded edges). Russell cleans and reuses them, and they develop a nice epoxy-shine.

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  Andrew Selmes says:

  This video set is timely advice for me as I’m about to fit the seats to my dinghy and will need to fillet inside the watertight compartments and around the top of the seats. Thanks for a great site.