What to mix with epoxy to make marine filler

Short intro... I have a small fiberglass boat with some crunched spots that the previous owner patched terribly with something.  I want to grind that out and do it right.  I have some good marine epoxy, but wondered what to mix in to make a filler.  It doesn't need to be flawless, but me and bodywork go together like lemon juice and a paper cut, so having better materials might mean that it just ends up looking terrible instead of hideous.

I have some powdered microfiber, but it's clumpy.  It mixes up kind of like grits or oatmeal.  I have tried rubbing it in my hands to break up the chunks, but haven't found the recipe there yet.

What would you mix in to make a nice smooth putty for fairing out a boat hull?

When you have clumpy micro balloons, I recall you're supposed to dry them out in an oven.  You might try the same with your microfiber. 

I thought about maybe buzzing them in my coffee grinder, but I don't want to end up drinking microplastics.

But is microfiber powder the best stuff to use?

What's wrong with fiberglass?  Cut some up small and put it into the epoxy.  

My first thought for "lumpy" was coffee grinder. Then I started pondering if I would sacrifice my coffee grinder for this. Happy I am not alone.

Go to garage sales.  Buy old coffee grinder.  Paint it OSHA yellow and keep it in the garage. 

If you are using epoxy, you can use wood flour which is basically fine sawdust. It's pretty cheap. That is what I used on the jet boat.

You can also use Cabocil fumed silica. Also cheap. Your local hardware store might stock it. 

alfadriver said:

What's wrong with fiberglass?  Cut some up small and put it into the epoxy.  

I will be using glass on some spots, but I can't get it fine enough for a final finish putty.  I'm looking to basically make my own bondo but have it be stronger than bondo for the inevitable scrape on a rock

Mr_Asa said:

Go to garage sales.  Buy old coffee grinder.  Paint it OSHA yellow and keep it in the garage. 

Not a bad idea.  The one I have in my kitchen is a $5 yard sale grinder.  Maybe I upgrade the one in the kitchen and retire this one to the garage.

Toyman01 + Sized and said:

If you are using epoxy, you can use wood flour which is basically fine sawdust. It's pretty cheap. That is what I used on the jet boat.

You can also use Cabocil fumed silica. Also cheap. Your local hardware store might stock it. 

 

Excellent.  Thanks. I hoped you would chime in.

The jet idea is still on the table for the boat, I'm just concerned that jet-ski sized propulsion will be a bit heavy and a lot overkill.  I want to plane, not die. 

I'm researching smaller housings/impellers that might be a better match for something like a 150cc engine.

In reply to Curtis73 (Forum Supporter) :

Maybe you need the power unit from one of these.

https://www.mokai.com/

I actually used to have a Mokai.  Never put it in the water because it was an "investment."  Found it at an auction sale brand new, never even took the engine out of the bag.  I won the bid at $175 and sold it a week later for $2700.

I have thought about a Mokai drive, but I suppose it depends if I can scale it up to 10-15 hp from the 5-6 it comes with.  It also depends on the type of plastic that the hull is made of.  As I recall, the jet was molded into the hull and it felt like it might be a polyethylene plastic which doesn't always take epoxy well.

Does anyone have sources for jet drives that I can shop... new or scavenged.  All of the PWCs I've researched are at least 500cc-1800cc.  I'm thinking more of a turnt-up GY6 150cc.

Hmmm... perhaps a new thread for that.

I think "micro-balloons" are what you're looking for to make the epoxy thicker and a better filler. 

West Marine has Micro-Fiber, also available at ACE Hardware for ~$14.  Why do the project twice?

914Driver said:

West Marine has Micro-Fiber, also available at ACE Hardware for ~$14.  Why do the project twice?

The microfiber I have is West Marine, as is the epoxy.

I'd second (third?) microballoons as the filler maker you're looking for. A little bit of epoxy and a whole lot of microballoons to make a nice peanut butter thick slurry. It goes on smooth and should not be chunky in the least. Makes epoxy infinitely more sandable without adding a ton of weight or giving up strength. Much better than microfiber. 

Hey Curtis, West Systems has a chart on their website that shows the uses and attributes of all of their fillers:

https://www.westmarine.com/fillers-putties/west-system

My only issue with micro-ballons is they are a PITA to wet out and mix in large batches. Almost like mixing oil and water. They are also more expensive and not as strong as Cabocil. 

In reply to CAinCA :

I KNEW they had to have that but I didn't find it.  Thank you.

Toyman01 + Sized and said:

My only issue with micro-ballons is they are a PITA to wet out and mix in large batches. Almost like mixing oil and water. They are also more expensive and not as strong as Cabocil. 

I'll see if I can find some.  Thanks.

Currently involved in a conversation over on boatdesign.net forums and they are losing their minds on why I don't put a 25hp outboard jet on it.  Because evidently the answer is a 275-lb outboard that would instantly sink the boat.  One guy contends that any water with lower-unit-killing rocks is not even water that you can boat on and I'm basically comitting suicide if I put a boat on that water.

In reply to Curtis73 (Forum Supporter) :

Some people have no sense of adventure. 

I wonder if you couldn't run a 150cc engine on a 300-400cc pump. I know the pump in the Jet Boat has several different pitch impellers available. It is also not a lot smaller in diameter than the pumps they run on 1000 cc engines. And if you go to a 4 stroke and turn it 4000 rpm instead of 6000 rpm the pressure and power requirements should be lower.

Maybe.

Also found this today.  Plastic impeller.  You can get it with an aluminum impeller as well, but pricey.  

GY6s typically top out at 8000 rpm, but they also have a built-in gear reduction.  Most of the scooters have... guessing... a 15" tire diameter which means at 60 mph they're spinning 1200 rpms or so.  Assuming the centrifugal clutch is fully engaged and the CVT isn't giving up too much, one could guess a 5:1 gear reduction?  Aftermarket gears are available as well for cheap, so getting a target impeller RPM should be possible.

I thought a good bit about something larger... 250cc or 300, but I can't think of any that don't come with an integral-cast transmission.  At least the GY6 you can cut off the CVT and just have an output shaft.

Curtis73 (Forum Supporter) said:

Also found this today.  Plastic impeller.  You can get it with an aluminum impeller as well, but pricey.  

I might have to order one of those.