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Board project, core repair
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surfalex



Joined: 08 Aug 2008
Posts: 68

PostPosted: Thu Jul 26, 2018 4:01 am    Post subject: Board project, core repair Reply with quote

My beloved Starboard Flare had gained almost 4ibs of water due to a hidden crack underneath the pad
usually Iíd take my waterlogged boards to the dump, it seems almost impossible to extract this much water. Out of curiosity I started cutting holes to see how far the water had reached. As you can see , a pretty large section of eps core around the front straps were dug out ( soaking wet )
I was able to extract 5 Ibs of wet EPS foam and now Iím actually curious if I can somehow rebuild the core.
Would a two part marine urethane be an option for this big of a fill ?
Other option would be to rebuild the core with new EPS foam. This would be more complex, I would need to cut open the entire top divinycell layer in other to ď fit ď and glue the new EPS foam into place
The urethane method seems easier , just not sure how well it would bond, itís also very brittle.



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thombiz



Joined: 25 Jun 2007
Posts: 678
Location: Corpus Christi

PostPosted: Thu Jul 26, 2018 7:55 am    Post subject: Reply with quote

Yes, you can replace the original EPS foam with 2-part urethane. The urethane will bond very well to the EPS and it will be stronger in flexural strength and compression strength. Be cautious though because the urethane must be mixed in precise proportions and you will have a very short pot life. You will have about 40 seconds to blend and fully mix the components and start the pour. Also, the urethane foam is very exothermic meaning it gives off heat as it cures. If your board's skin was formed with heat then it will be prone to temporarily going soft and warping as the urethane sets up. You can avoid this by leaving some of the EPS foam right at the skin of the board. Leaving a 1/4" thick EPS at the skin will prevent the skin from heating and warping. Also, pour in smaller batches to reduce the possibility of overheating. Aim for pours resulting layers about 1" thick to prevent overheating. The outside skin of the board is typically made with fiberglass between the EPS core and the high density skin. When you repair the access holes, you will need to bond the repair glass to that existing glass to return the high density skins strength. I usually use a hacksaw blade to scrape out a small amount of the foam just under the inner OEM fiberglass and carefully bond a new piece of glass to the existing glass much like an internal bandaid. This will give the repaired hole strength similar to the oem construction.
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U2U2U2



Joined: 06 Jul 2001
Posts: 4738
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Thu Jul 26, 2018 8:23 am    Post subject: Reply with quote

I use this all the time, itís POUR foam, use 8lb version.

It bonds and cures fine with EPS, works easily . Need to top with layers of glass/carbon.

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surfalex



Joined: 08 Aug 2008
Posts: 68

PostPosted: Thu Jul 26, 2018 12:32 pm    Post subject: Reply with quote

Thanks thombiz for excellent reply. The " internal bandaid " makes sense.
Sounds difficult to get a patch of fiberglass to fit in a tight " hacksaw blade sized " space. Do you install the glass patch dry and then try to inject the the resin from the sides to get it to bond with old glass ?
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dllee



Joined: 03 Jul 2009
Posts: 3903
Location: East Bay

PostPosted: Thu Jul 26, 2018 12:55 pm    Post subject: Reply with quote

Use the hacksaw blade to push in the cloth and epoxy/chopped glass mix.
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U2U2U2



Joined: 06 Jul 2001
Posts: 4738
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Thu Jul 26, 2018 7:49 pm    Post subject: Reply with quote

Pour foam does kick, as it cures, heats up. Ive never had a prob with it melting the core.

Epoxy, different book. Their are many ways to do this. KISS

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mrgybe



Joined: 01 Jul 2008
Posts: 4451

PostPosted: Fri Jul 27, 2018 4:57 pm    Post subject: Reply with quote

I am a complete novice with serious board repair but I'd like to give it a go with a really old (1989 I think) Mistral Screamer, my first short board which I loved and would like to sail again. It has a soft deck. Anyone know whether the repair materials suggested above would be suitable for a Screamer of that vintage? It is a DCS. Thanks.
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thombiz



Joined: 25 Jun 2007
Posts: 678
Location: Corpus Christi

PostPosted: Fri Jul 27, 2018 7:05 pm    Post subject: Reply with quote

Another way to bond repair fiberglass to OEM fiberglass between EPS foam and high density foam at site of repair. One thing to consider is making one or two big holes by incorporating several small holes into one big hole. Might actually be easier.


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U2U2U2



Joined: 06 Jul 2001
Posts: 4738
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Fri Jul 27, 2018 7:16 pm    Post subject: Reply with quote

mrgybe wrote:
I am a complete novice with serious board repair but I'd like to give it a go with a really old (1989 I think) Mistral Screamer, my first short board which I loved and would like to sail again. It has a soft deck. Anyone know whether the repair materials suggested above would be suitable for a Screamer of that vintage? It is a DCS. Thanks.


The inside should be EPS, looks like a cheap ice cooler. The materials for repair are the same.
See::
Boardlady.com

EPS will melt with too much or quick setting epoxy, used either slo or tropical/extra slow.

A site like Fiberglass supply supplies all you need, common things like sandpaper , paper can be obtained at the local hardware

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4Boards....May the fours be with you

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http://4boards.co.uk/
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mrgybe



Joined: 01 Jul 2008
Posts: 4451

PostPosted: Sat Jul 28, 2018 12:07 pm    Post subject: Reply with quote

Thanks.
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