Epoxy resin non official thickeners

[Wooden Boat Fittings]

Sawdust from a bandsaw is much finer than from a circular saw. I save all my bandsaw dust expressly for use as epoxy filler. Mix up the epoxy first, then mix in as much filler as you need -- usually a surprisingly large amount -- and make sure it's all wetted out thoroughly. If used for fairing a wooden hull, and even if the wood flour comes from the same timber as the hull, note that the cured epoxy-plus-wood-flour-filler will be much darker than the rest of the hull.

Mike

 

[Poignard]

They're out there

A sales engineer from Wessex Resins Ltd (UK distributor for WEST epoxy) told me he had been sent to investigate a complaint from a customer, who was building a boat, that the WEST epoxy he was using was not producing strong bonds.

He found out that the boat builder was using damp building sand from a pile he had in his garden.

 

[Bobobolinsky]

Fine sand is often used to repair ferro cement hulls and no-onne has mentioned chopped glass strands

 

[usernamenotvalid]

Fine sawdust is... fine. Built a few wood kayaks and it's very common among the kayak building community. Someone earlier said" If you use sawdust (fine) of the same wood that you are using it is colour-keyed which is handy." WRONG! use sawdust about ten shades lighter if you want to come close to a match. Dunno why it just is so. This page will give you a quick outline of what you need to know. Steps 2, 3 and 4
http://www.jemwatercraft.com/forum/viewforum.php?f=6&sid=247bff5f053deb6b9419af5adfa6c240
Kayaks are just like boats only littler. They still have to stay together and not leak. Out of curiosity I once filled a plastic bottle cap with some leftover wood dust and resin. After two weeks it took six hammer blows to crack it. Oh.. mix the sawdust and resin before adding catalyst.
Cheers John

 

[oldsaltoz]

Maybe i was doing it wrong, but when i built my stitch and tape dinghy i thought i would use sawdust for filling the seam fillets.
Test pieces were dreadful. Difficult to apply and rough when i did.
I bought a bag of micro balloons. Not overly expensive and they go a long way. Smooth to mix and apply and easy enough to sand.
Finished the dinghy and still use the same bag for odd filling jobs. Dont think i will run out soon.
I still don't know what a micro balloon is though.

Bubbles or resin is the answer, Micro spheres on the other hand are glass bubbles, more suited to underwater applications and a little bit harder to sand, but as hard as the normal lay up.

Good luck and fair winds.

 

[ThreeSummers]

Im constructing a plywood boat using epoxy resin for the first time. To make the resin suitably thick e.g. peanut butter type thickness, can handy every day supplies be used such as sawdust or anything else easily to hand e.g flour??

This is what I've used with epoxy on two new builds, one total rebuild (boat stripped to bare GRP shell) and several boat repairs and modifications:

For joining and structural filleting - microfibres, cotton flocking, wood flour are all fine. Micro-ballons are not. Consistency is the key - if laminating plywood, a relatively thin mixture (cheap ketchup, not Heinz) is good - the filler is there to prevent voids forming. For filleting your peanut butter is about right - mix enough in that it doesn't sag or run.

For decorative filleting (like smoothing panel overlaps) and fairing: use micro-ballons - it's the easiest to sand. But, make sure it's a very thick mixture - if your wrist isn't hurting from stirring it it's not thick enough - think decorative icing sugar.

For shaping - for instance building up on my boat the stem to a nice profile, then use colloidal silica - it's the hardest to sand, but it doesn't sag. Not good for structural use as it's more brittle than the other fillers.

Sawdust - a lot depends on how fine it is - the finer the better, but it's not as easy to get a smooth fillet like microfibres - remember that every lump, peak, bump etc. will have to be sanded smooth before the next stage. The smoother you can apply it, the less work you have to do.

My advice, go for the West fillers that are made for each application as they describe (I use West as an example as that's what I use). The cost is small compared to what you're going to spend on epoxy, wood, glass and sandpaper...

My 2p

Tim.