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dvCali
Joined: 23 Aug 2007 Posts: 1314
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Posted: Fri Sep 27, 2013 9:09 pm Post subject: |
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thombiz wrote: |
b. Use a router with a plow bit to remove the outer reinforcing and most of the high density foam for a distance of about 3" from where you cut the nose off. Be careful to set the plow depth so that it does not cut the reinforing fiber between the outer high density foam and the styrofoam.
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Hi Bob, similar winter project here (but later: fall wind has been good!). Just wandering: why go through the complication of the router instead of simply sanding the 3" area from the cut and glassing over to the new front with 4oz S-glass? |
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dllee
Joined: 03 Jul 2009 Posts: 5329 Location: East Bay
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Posted: Fri Sep 27, 2013 9:41 pm Post subject: |
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I like sanding a bevel into the cut area, instead of routing, because I'm lazy and some very good board repair people do it that way.
A clean rout can make a better water seal, as the glass can butt into the L shaped notch.
But in practice, it seems a bevel can work just fine. |
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thombiz
Joined: 25 Jun 2007 Posts: 799 Location: Corpus Christi
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Posted: Fri Sep 27, 2013 11:48 pm Post subject: |
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The reason to cut back the high density foam is to expose and bond to the reinforcing between the high density foam and the styrofoam. Boards can delam in many ways, like heat, air pressure, etc. but one of the most common ways is to not have enough strength in the reinforcing between the high density foam and the styrofoam. A shortage of reinforcing allows the high density foam to deflect too much under load damaging the styrofoam. In this case, (remaking the nose) the possibility of mast whacks is very very high. Extra reinforcing will turn mast whacks into dents instead of breaks and cracks. High density foam can be incredibly strong and durable if you give it enough reinforcing. I've worked on a number of commercial boards with reinforcing in the .7 oz to 1.4 oz. range. This gives the the boards a very light weight at the cost of a short lifespan. You don't have to go overboard with reinforcing. I use 6 oz s-glass or 6 oz carbon in the footstrap area and 4 oz. s-glass or carbon in all other areas between the high density foam and the styrofoam. I usually double layer on the frontmost 16" of the nose. I've never had a delam on the boards I've built, even after 5 or 6 years and I weigh 225 lbs and sail some pretty rough water.
I have no problem with a tapered joint, I just happen to be better at making square joints. |
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thombiz
Joined: 25 Jun 2007 Posts: 799 Location: Corpus Christi
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U2U2U2
Joined: 06 Jul 2001 Posts: 5467 Location: Shipsterns Bluff, Tasmania. Colorado
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Posted: Tue Oct 01, 2013 2:43 pm Post subject: |
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thombiz wrote: |
b. Use a router with a plow bit to remove the outer reinforcing and most of the high density foam for a distance of about 3" from where you cut the nose off. Be careful to set the plow depth so that it does not cut the reinforing fiber between the outer high density foam and the styrofoam. You can sand any high density foam down to just above the reinforcing.
c. Sand smooth the styrofoam where the new addition will be added. Use a styrofoam bonding glue to bond the new styrofoam to the existing styrofoam. If in doubt on which glue to use, check Swaylocks. Bond the new to the existing.
Bob T. |
Confused on the "plow router bit" bit, is the bit called something else perhaps,other than plow.
Square cut off the nose..then is it joined like a dovetail or similar ? _________________ K4 fins
4Boards....May the fours be with you
http://www.k4fins.com/fins.html
http://4boards.co.uk/ |
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dllee
Joined: 03 Jul 2009 Posts: 5329 Location: East Bay
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Posted: Tue Oct 01, 2013 4:18 pm Post subject: |
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Seems to me, any router bit does the job just fine.
You're only cutting 3/16" groove depth into the Dcell, so you increase bearing surface for a complete waterseal. |
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thombiz
Joined: 25 Jun 2007 Posts: 799 Location: Corpus Christi
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Posted: Tue Oct 01, 2013 5:57 pm Post subject: |
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A picture is worth a thousand words: this is what I would use
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U2U2U2
Joined: 06 Jul 2001 Posts: 5467 Location: Shipsterns Bluff, Tasmania. Colorado
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dllee
Joined: 03 Jul 2009 Posts: 5329 Location: East Bay
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Posted: Tue Oct 01, 2013 9:44 pm Post subject: |
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Looks like the bit in the router I last used. |
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U2U2U2
Joined: 06 Jul 2001 Posts: 5467 Location: Shipsterns Bluff, Tasmania. Colorado
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