Filling old rubbing strake screw holes

richardwvm

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Hi Folks,

I intend to replace the rubber D shape rubbing strake on my small GRP yacht. The previous owners have obviously done this at some point in the past, however they didn't fill the old bolt holes and failed to make a good job of the new ones; she leaks like a sieve.

I want to remove, fill with epoxy and start over. Unfortunately all the hole filling videos and tutorials I've seen thus far happen on a flat horizontal surface, mostly not all the way through the fibreglass. Should I simply mix the epoxy with more additive (e.g. West System 403) so it's thick like a putty or just use an epoxy filler type product?

All the holes are all the way though the fibreglass, so I'll have to tape up the backs I guess, but it's really overcoming gravity without it falling out the hole and dripping down the hull that I can see being the main issue.

Any ideas and advice much appreciated.

Regards,

Richard.
 

Tranona

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You can bulk out epoxy to almost any consistency. With your job strength is not an issue, but you need to pay attention to adhesion in the holes. so, use woodflour or wood fibres plus some microballons to increase smoothness and paint the inside of the holes with neat epoxy before you fill. Tape the back to avoid it going right through and the front to ensure it stays in while it is curing. You will probably have to experiment a bit with your mix to get it right. Don't mix too much at a time as the bulk can lead to exothermic reaction and it goes off quickly - and very hot!
 

VicS

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Hi Folks,

I intend to replace the rubber D shape rubbing strake on my small GRP yacht. The previous owners have obviously done this at some point in the past, however they didn't fill the old bolt holes and failed to make a good job of the new ones; she leaks like a sieve.

I want to remove, fill with epoxy and start over. Unfortunately all the hole filling videos and tutorials I've seen thus far happen on a flat horizontal surface, mostly not all the way through the fibreglass. Should I simply mix the epoxy with more additive (e.g. West System 403) so it's thick like a putty or just use an epoxy filler type product?

All the holes are all the way though the fibreglass, so I'll have to tape up the backs I guess, but it's really overcoming gravity without it falling out the hole and dripping down the hull that I can see being the main issue.

Any ideas and advice much appreciated.

Regards,

Richard.

If you have the epoxy and 403 filler that sounds like a good way forward.

Filler seelction table here: http://www.westsystem.com/ss/filler-selection-guide/

I take it all the filled holes will be hidden so personally I'd probably just use car body filler ! Cheap, readily avaialble, easy to use, mixing proportions not critical, and sets quickly.

Even when visible I use it , filling to just below the surface level the finish off with gelcoat filler.
 

knuterikt

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Clear packing tape is perfect for this.
I have used this successfully onsdag both vertical and underside horisontal surfaces.
Mask inside,
mix epoxy and hardener
Apply unthickend epox
Add colodial silica to make the rest thicker
Apply epoxy
Use the tape to push epoxy into the hole and keep the epoxy in place while drying.
Remove excess epoxy.
Almost no sanding neded.
 

richardwvm

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Hi knuterikt,

Sounds like a good method, did the unthickened epoxy not run out while adding silica to the mix? I guess you were using the thickened epoxy like a bung to hold in the runny stuff?

R.
 

bigwow

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Before filling the holes I'd use a countersink bit to make the holes cotton reel shape, so there is no chance of the filling falling out either way.
 

Scoresby

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I believe that the simplest and best way to fill small holes is as follows:

1. Use a 'finger file' to chamfer around the edge of the hole. This will provide a better key than using a cutting tool (countersink etc.). Although a combination of a countersink and some fiddly sanding with coarse (60/80 grit) sandpaper would be fine.
2.Clean with acetone.
3.Apply some 'styrene and fibres' eg. Isopon P.40 or similar. Ensure that you leave the surface well proud so that all possible low spots will be eliminated.
4.Before the filler goes too hard but not so soft that it lifts out of the hole, take a sharp chisel and gently carve the protruding pellet of filler to size. If you try and take too much off the pellet in one go it may lift out.
5.Just start off with a few holes at a time until you get the feel for the job. If you fill too many holes the filler might be too hard to carve and will require a lot of tedious sanding.

A paint stripper type heat gun is also very useful as you can use it to control the drying rate of the polyester.
If you use polyester based filler as opposed to epoxy then you avoid a lot of potential problems and save money.
 

vyv_cox

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If you use polyester based filler as opposed to epoxy then you avoid a lot of potential problems and save money.

The advantages of epoxy over polyester are, 1). Its adhesion is considerably better, so less likely to fall out 2) polyester shrinks slightly as it cures, whereas epoxy does not. The resulting annular gap with polyester may let water in and the filler may fall out.

If doing a lot of this work, which I am doing when replacing corroded steel bolts with stainless used for holding on wood trim on my 1973 motor-sailer, I use Milliput. Excellent stuff, sets wet, done by hand with no need for pots or measurement, easily abraded back to a flush finish and can be painted to match the surroundings. http://milliput.com/
 

Scoresby

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The advantages of epoxy over polyester are, 1). Its adhesion is considerably better, so less likely to fall out 2) polyester shrinks slightly as it cures, whereas epoxy does not. The resulting annular gap with polyester may let water in and the filler may fall out.

If doing a lot of this work, which I am doing when replacing corroded steel bolts with stainless used for holding on wood trim on my 1973 motor-sailer, I use Milliput. Excellent stuff, sets wet, done by hand with no need for pots or measurement, easily abraded back to a flush finish and can be painted to match the surroundings. http://milliput.com/

Whilst I agree that most epoxy resins have theoretically superior adhesion properties over polyester resins, the figures most often quoted in technical specifications for epoxy include a 2 hour post-cure at 70degreesC. There is not nearly so much difference without the post-cure.
From a practical standpoint however I can say that I have repaired thousands of screw/bolt holes without a problem using polyester. Quicker, cheaper and much much less to go wrong especially when the conditions are not ideal.
I will say however that using a pre-mixed epoxy filler sounds like a much better idea than a diy epoxy-putty. Less to go wrong.
 

richardwvm

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So I removed the old rubbing strake yesterday and the installation was worse than I thought! I think I may actually grid back slightly inside and apply a layer of CSM to each hole / cluster of holes, then fill with epoxy filler/putty externally. It would appear they'd also used household silicone sealant and no reinforcing plastic strip inside the 'D' shape profile; we could pull it off by hand!

Will try and document with photos for others future reference.
 
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