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PostPosted: Wed Mar 19, 2014 7:04 am 
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Hello all,
Last night I began working on an old pair of EPO's that were severely worn out. The fibers were like hairs on the outside. I followed the advice on the forum of wetting them with West 105/206 (slow hardener to aid in out-gassing) and then used a squeegee to make the epoxy as thin as possible. But when I did the first coat, the fibers wouldn't all lay down flat. Now I have an incredibly bumpy board. I did two coats hoping that the second coat would even things out a bit. No luck there.

Image
Image

Now I'm thinking I need to sand it flat and see if I can get it back smooth again. How much should I sand? I'm worried that sanding too much will expose the fibers again. I also don't want to make it too thick or the board won't fit in the castings.

Anyone have any suggestions? I'm not sure anyone has done a board in the past that was in as bad of shape as this one.

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PostPosted: Wed Mar 19, 2014 9:12 am 
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On the EPO's I've done, where there were exposed fibers, I lightly sanded them off first using 80 or 100 grit paper. Obviously you don't want to go overboard here, but I think you're better off starting with a smooth surface rather than trying to get the fibers to lay back down. Starting with a clean, roughed up surface is critical. Lightly sand the entire rudder with 100 grit or higher sand paper to give the epoxy something to grab on to (a sanding sponge works well). Then clean the rudder really well with acetone. Also, when I did this, I only did one side of the rudder at a time so the epoxy wouldn't drip. I painted the unthickened epoxy on using a disposable 1" brush.

I know one of the rudders I resurfaced had a lot of exposed fibers and started out really bad, but I sanded off the exposed stuff, resurfaced and painted it and it came out really nice. I think if you're worried that sanding off the exposed fibers is going to weaken the rudder, you'd still be better off sanding them away and then add a new ply of glass fabric over the rudder when you coat it with epoxy.

Anyway, you've got epoxy on there now. I'd sand it all down smooth and then maybe put another thin coating on. The problem now is the surface is so uneven, you're going to have a tough time getting it back fair. I would use coarse sand paper on a sanding block to knock down all the high spots and then use a sanding sponge to fair it out.

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PostPosted: Wed Mar 19, 2014 9:23 am 
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Thanks so much. So you're saying that I can just sand off the fibers? I didn't know that they would break off that easily.

Luckily I've only done one side of each rudder.

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PostPosted: Wed Mar 19, 2014 10:26 am 
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All I have to offer (in case you didn't know) is.....get that major sanding done as soon as the epoxy has cured enough that it's not too gummy. If you wait too long, it'll be hard as a rock.....especially if you added any silica to inhibit running.

Good luck!

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PostPosted: Wed Mar 19, 2014 10:29 am 
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Luckily I didn't add any filler. I'll sand tonight and see how it goes.

I was surprised at how slowly it cured with the slow hardener. Temperature was 70 degrees in the basement. It took all night to harden to a semi-tacky texture.

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PostPosted: Wed Mar 19, 2014 11:10 am 
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Contrary to rattle 'n hum's advice, I would suggest you let the epoxy fully cure before attempting to sand it. If it is not fully cured, it will gum up your sand paper and make removal even more difficult. It's better (easier) to sand epoxy that is good and hard than soft epoxy. Just use a more coarse grade of sand paper.

And yes, I would sand off all loose fibers prior to coating with epoxy. As I said above, I would sand the entire rudder lightly (scuff the surface to a cloudy haze) before coating.

Regarding cure time, this is all based on temperature. Slow hardeners are typically for 80 degress or higher. If you were at 70 degrees, then it is certainly going to take a while to cure. Also, since the resin is being spread over a large, thin area, it doesn't build up heat which adds to the cure time. The resin in your mixing cup will cure much more quickly than the resin on the rudder blade because the resin in the cup builds up heat which is not easily dissipated.

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PostPosted: Thu Mar 20, 2014 10:35 am 
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I sanded a little this morning and it looks like I'll be able to make this work. Thanks for the advice! I'll post pictures once I'm done.

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PostPosted: Thu Mar 20, 2014 11:07 am 
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Apparently there are differences of experiences/opinions, maybe due to the use of different products, etc. I'll clarify mine for the consideration of future readers if not Zach. As I stated above, one would not want to sand when the epoxy is still too gummy. However, there is a big difference (in time and hardness) between the point of just being not gummy and being "fully cured." After a day or so, when the epoxy is just cured enough that it's not gummy, it's still relatively easy to sand in my experience. After a week when it's fully cured, it's much more difficult.

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PostPosted: Tue May 13, 2014 5:56 am 
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Hey I have been working on my EPOs as well, depending on your location (temperature) you might have better luck with a quicker set epoxy. For me living in new hampshire trying to get anything to set under 60 deg is tough. The other advice I got off the forum that has been a huge help is to use graphite filler 423 from westsys its very thin and easily sanded. If your using the quick pump system, 1 squirt ea with about a half teaspoon graphite will do the trick for painting one side on each board. the last bit of advice is put on very thin coats, roll it on first with a micro roller, then tip with a foam brush.

here is what I have done
sand with 100 (I had exposed fibers too)
first coat
sand 220
second coat
sand 600 wet
third coat <- hopefully get this done tonight
sand 1200 wet?
wax/polish

hope this helps, you if you search EPO repair you can find the quick build page that I used.


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PostPosted: Tue May 13, 2014 7:18 pm 
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Damn i'm glad i found this! I have a set of EPO's needing the same treatment. Are older EPO's the same size as the new ones?

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1978 H16 (sold)
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PostPosted: Tue May 13, 2014 8:19 pm 
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Fxloop wrote:
Are older EPO's the same size as the new ones?


Yes the original EPO's and EPO2 should measure just about the same, and in some ways they are sometimes better... I have seen (minor) symmetry issues on several different EPO2 rudders that I have yet to see on the original EPO rudders.

I haven't got to play with the EPO3 rudders yet.


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