Epoxy Filler

Cowie

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18 Nov 2020
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Could anyone recommend a epoxy filler which still retains some flexibility.
(Other than sikaflex)

Job in hand is fairing a keel
 

savageseadog

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Bear in mind that epoxy such as West will set quickly so doing a large area could be an issue. A slow epoxy is probably available. We have been using the Internaitional product which we bought cheaply, it's years old but keeps working and has a long set time.

There is colloidal silica and glass microballoons as well as Talc. The International keel filler is definitely Talc based.
 

Cowie

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18 Nov 2020
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Bear in mind that epoxy such as West will set quickly so doing a large area could be an issue. A slow epoxy is probably available. We have been using the Internaitional product which we bought cheaply, it's years old but keeps working and has a long set time.

There is colloidal silica and glass microballoons as well as Talc. The International keel filler is definitely Talc based.
Thank you for the input I'll give the International a spin
 

Keith 66

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Talc as a thickening agent is easy to sand but it sags something awful, you need to put some colloidal silica or cabosil in it as well as this is far more non sag.
 

Ceirwan

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Epoxy filler for fairing a keel is almost certainly going to crack unless you have the worlds stiffest keel hull joint.
Unless you're repairing an encapsulated keel or something like that.
 

Cowie

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Hi Ceirwang

Fairing in a Dehler 36 keel to hull it has always been done with Sikaflex but the finish has never been achieved even when wet and dry sanding, using all recommend grades. As to the amount of movement this is up for debate.
 

savageseadog

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It's fairing we're talking about. Fairing a keel is basically a similar process to using car body filler on a car. Talc is the thickener. The filler can be finished to a very high standard. It doesn't sang if correctly blended.

The keel Hull joint is a different animal and a different material is needed.
It matters not if the Talc is permeable or not as it will be applied to a primed keel and will be overcoated. As the Talc is embedded in epoxy I don't believe there will be much, if any, permeability.
 

Ceirwan

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Hi Ceirwang

Fairing in a Dehler 36 keel to hull it has always been done with Sikaflex but the finish has never been achieved even when wet and dry sanding, using all recommend grades. As to the amount of movement this is up for debate.
I quickly googled the boat. Looks like a fairly standard keel. Most likely cast iron.
The issue is that the GRP around the keel is far more flexible than the epoxy, so even something flexible like G-Flex will most likely still crack.

The only use I know of for epoxy in this kind of keel joint is to fair the mating surfaces when fitting the keel to ensure a perfect joint. The thickened epoxy is smeared across the hull joint & a the boat lowered onto the keel with plastic release film between the keel & hull.
Excess squeezes out & after its cured the two are separated again & the final fit is done with a flexible sealant.
By all means try the flexible epoxy, but I think it will be an expensive disappointment.

It's fairing we're talking about. Fairing a keel is basically a similar process to using car body filler on a car. Talc is the thickener. The filler can be finished to a very high standard. It doesn't sang if correctly blended.

The keel Hull joint is a different animal and a different material is needed.
It matters not if the Talc is permeable or not as it will be applied to a primed keel and will be overcoated. As the Talc is embedded in epoxy I don't believe there will be much, if any, permeability.
I had a quick google & this study seemed to indicate that Talk in a polyester resin made a large difference t o the water uptake, naturally it would be less with epoxy, but why take the chance when you can buy a big tub of something more suitable for underwater use from most online distributors for very little indeed?

(PDF) International Journal of Engineering & Technology IJET-IJENS Vol:13 No:02 122 136802-6060-IJET-IJENS © April 2013 IJENS Fabrication and Characterization of Woven Natural Fibre Reinforced Unsaturated Polyester Resin Composites
 

goeasy123

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Call CFS Fibreglass Supplies on 01209 821028 and tell them what you want. They have a big range of fillers. There's a chap there is a wiz on mixing them to get the result you want.

I wanted an easy to sand fairing for my keel. He gave be 3/4 miro-balloons + 1/4 colloidal silica to prevent sag.
 

Cowie

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Call CFS Fibreglass Supplies on 01209 821028 and tell them what you want. They have a big range of fillers. There's a chap there is a wiz on mixing them to get the result you want.

I wanted an easy to sand fairing for my keel. He gave be 3/4 miro-balloons + 1/4 colloidal silica to prevent sag.
Thank you for heads up, will call, them this particular area has always niggled me.
 
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