Question on fillet mixture

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NickAndJena

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This week I hope to mix up some fillet material to fill the gap between the perimeter of the transom boards and the boat hull. In my ultimate wisdom, or lack of experience (choose one), we ordered some stuff I thought would be good for mixing a putty-like fillet material. No no no... I didn't get cabosil, although I probably should have.

My new question in the transom replacement thread is this...

Will I have any luck mixing 1/32" Milled Fiber with epoxy resin to be used as a fillet?

Here is a short description of what I'm referring to. From our friends at US Composites (http://www.uscomposites.com/fillers.html):
1/32" Milled Fiber
Milled fiberglass powder added to epoxies and polyesters to increase strength of putty and add surface toughness/hardness.

I will do a test run, but I thought I would ask the masters...
 
J

J. Mark

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Re: Question on fillet mixture

I think the milled fiber is just about perfect for that application. It is what i am using to tab in my deck.
 
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NickAndJena

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Re: Question on fillet mixture

J. Mark said:
I think the milled fiber is just about perfect for that application. It is what i am using to tab in my deck.
Click to expand...

Cool, thanks for the reply.

I'm going to mix a test batch tonight and see how it goes. I'll post some photos later on.

Nick
 
ondarvr

ondarvr

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Re: Question on fillet mixture

Only using milled fibers makes it difficult to form a good radius and will allow the resin to sag, Cabosil will help prevent sagging and make a smoother consistency putty so it will b easier to form a the desired shape. Talc will make an even smoother putty.

If you need to shape it by sanding, then add glass bubbles also.
 
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NickAndJena

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Re: Question on fillet mixture

Initial test results show that the fillet we mixed tonight was a bit too 'heavy'.. It kept sagging on the vertical joints rather than staying put as it did on the horizontal joints. We mixed:

4 oz batch of epoxy
7 tablespoons of milled fiber
7 tablespoons of baby powder (talc and fragrance)

I think next time we need more talc and less fiber.

Would it make sense that the fiber was the ingredient making it heavy?
:confused:
What is a good recipe here? It seems everyone has an opinion on this but there must be some valid guidance. I've done some reading on the topic but most people suggest buying a pre-mixed batch of the putty... That's just way to easy for me I suppose, any opinions or advice would be greatly appreciated.

By the way, the subject boat is a fiberglass boat (see url in my sig), not a wood boat so the wood flour really isn't something I'm considering.
 
ondarvr

ondarvr

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Re: Question on fillet mixture

Cabosil (fumed silica) is what stops the sagging, the other items can make it thicker, but won't do the same thing.
 
G

"G"

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Re: Question on fillet mixture

Fillers like these you mention are common in filling holes/patching where structural strength isn't critical like on a transom. My suggestion is saturated fiberglass shredded fibers like what they used in "chopper" built boats. (They use this same technology in reinforced concrete today.)
Building back from old to new we used (alternating) cloth, mat, mesh and fiber. That was what the FG pro's of the day told me to use. Then again; that was back in the late 70's when I worked on/repaired 40' and 50' vessels that hit rocks, tore holes in the hull etc. I never had a come back, blister issue or failure from doing the alternating glass methods. That says something about the procedure doesn't it? Sometimes old technology is better. I'd give it credence at least.
 
C

capri1600

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Re: Question on fillet mixture

For a structural puddy I use flox (ground cotton). Much more strength than micro balloons and easier to work with that milled fibers.
 
erikgreen

erikgreen

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Re: Question on fillet mixture

For non structural work you need to just mix the glue to a nice stiff consistency using a powdered or otherwise fine filler.

If you want strength, use the milled fibers, the longer the better, but they tend to permit sagging as mentioned, so you need to use a powder filler with them.

Myself I use wood flour, which I rarely measure. I just mix the resin fully, then pour in wood flour, mix, and adjust.

It's thick enough to not sag when it's very hard to mix and when it forms whirls and bumps in the bottom of the bucket that don't self flatten or "melt".

Rule of thumb: Mix longer than you think you have to, scrape the sides.

Put a small blob somewhere flat to see how much it spreads to gauge thixotropy (sagginess).

Erik
 
drewpster

drewpster

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Re: Question on fillet mixture

I recently broke up an old fish box a friend of mine built for his bass boat. He removed the box to do some re-rigging. He built the box out of luan covered in fiberglass cloth. Inside the box he used homemade filler to reinforce the corners inside the box. (small 1/4 fillets) He used epoxy (Mas) to build the box. The filler he made was epoxy mixed with plain old cabosil and milled fibers. He wanted to get rid of it because it was "cheesy" looking in his opinion and he wanted build something else.
If I ever had any doubt about the strength of epoxy fillers, I do not now. This thing was tough! We broke it up so that it would go in a trash can and we had to use a hammer to do the job. Even with those small fillets this thing was hard to break up.
Trust me, add some cabosil and fiber to catalyzed resin and it is going to be tough. Mix it to a peanut butter consistency and your golden.
 
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NickAndJena

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Re: Question on fillet mixture

Thanks everyone. This is great advice, I appreciate the discussion. I'm going to do one more test run to see if I can keep a batch from sagging. This test will include wheat flour (someone suggested that), and another batch will be using talc again. Since I want this to be strong, I'll add a portion of the milled fiber powder too but not as much as I did last night.

More to come on this. Worst case I can adjust the project plan and order the cabosil. I do have some other tasks on the project list that I can do in the meantime, but wanted to get the transom completely done before moving on.

Thanks again!
 
i386

i386

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Re: Question on fillet mixture

I mix mine in small batches in plastic margarine type containers using a plastic spoon. I use Cabosil. My method is just to add the filler until it won't run off the spoon. It looks similar to vaseline but not quite as thick. Just pick something and keep at it. You'll get the feel for it.
 
Mark42

Mark42

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Re: Question on fillet mixture

NickAndJena said:
..... I'm going to do one more test run to see if I can keep a batch from sagging. This test will include wheat flour (someone suggested that), and another batch will be using talc again......
Click to expand...

I've used wheat flour. Makes a nice white paste that doesn't sag. Let me know how the talc works.
 
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NickAndJena

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Re: Question on fillet mixture

Tonight I ran into a slight snag. I was removing the 4x4's holding the new transom boards to the stern of the boat and had some of the smaller bolts break off. We were using 1/2" carriage bolts which came out fine, but also had some smaller bolts 1/4" in diameter as we were using the pre-existing holes in the boat's transom. Anyway, tomorrow looks like I'll be grinding those out with a Dremel tool. :(

Why am I even saying this you ask?

Well we didn't get to the test tonight, I'm going to do the test tomorrow after doing some grinding. I knew Murphy wouldn't stay away too long. Anyway, I'll post the results to this thread when I get to it. Sorry for the delay.
 
drewpster

drewpster

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Re: Question on fillet mixture

I know its a little late, but in the future coat your clamping bolts with wax to make them easier to remove after the resin cures.
 
erikgreen

erikgreen

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Re: Question on fillet mixture

NickAndJena said:
Got it. Thanks. :rolleyes:
Click to expand...


and if they get stuck you can remove them with heat. Carefully apply a propane torch to one end of the bolt until it loosens... you don't need to burn the surrounding resin, just heat the bolt enough to free it.

Erik
 
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NickAndJena

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Re: Question on fillet mixture

erikgreen said:
aCarefully apply a propane torch to one end of the bolt until it loosens... you don't need to burn the surrounding resin, just heat the bolt enough to free it.

Erik
Click to expand...

Nice. I'm about to eat some dinner and then head out there to get them out. I'll try this method first. A lot easier than grinding, although I think some of the bolts broke off and are now recessed. I may have to grind those ones out. I didn't think about heating them though. Appreciate it Erik!
 
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