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BOARD nose modification ? strength ?
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U2U2U2



Joined: 06 Jul 2001
Posts: 2978
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Tue Sep 24, 2013 11:17 am    Post subject: BOARD nose modification ? strength ? Reply with quote

Iam deep in thought about a winter project, the immediate question is, if I remould the nose to make it broader/ change shape and need to add too , then obvious I need the addition of materials . Depending on the donor board, this may not be more than a nose repair or could involve a graft on the sides more than length

My initial concern is strength to the point of close to the original platform,
not much use in doing this to have it shatter on 1st impact.

What material would be the most likely to widen, and then add strength ?

seems a good start here

http://boardlady.com/wipeout.htm

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zirtaeb



Joined: 03 Jul 2009
Posts: 2148

PostPosted: Tue Sep 24, 2013 11:23 am    Post subject: Reply with quote

Done 3, none well.
OTOH, I seldom do anything well.
Cut initially with a skill saw, angled. Finish rounding with a surform or body file.
Chamfer the existing skin, for more holding power.
I like to use a lightweight spackle, then shape that. Better to shape more than you think, to make up for the next 3 steps of added material.
Glass with 2 layers of 6 oz fiberglass. Two layers is the strength of a normal short surfboard.
Some people even bother to sand and paint it, a real finish.
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isobars



Joined: 12 Dec 1999
Posts: 13315

PostPosted: Tue Sep 24, 2013 2:40 pm    Post subject: Reply with quote

Strength alone generally transfers forces elsewhere, often to no good end. Energy absorption, OTOH, soaks it up and either returns it or disperses it safely.

Thus padded noses and, if nec, masts. Doesn't look as elegant initially as well-faired sculpting, but the impact damage it prevents averts repair time, repair weight, water penetration, hassle, expense, worry, sailing conservatively to avoid damage, etc. I've sailed and crashed the daylights out of several boards well-known to be exceptionally fragile, with no damage since the day I began padding them. An ounce of pads beats half a pound of extra resin and water.
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dcharlton



Joined: 24 Apr 2002
Posts: 250

PostPosted: Tue Sep 24, 2013 4:23 pm    Post subject: Reply with quote

Wow! The lack of wind is really bad when we're thinking about winter projects in September...

Just venting, where's my FALL????????????

DC
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zirtaeb



Joined: 03 Jul 2009
Posts: 2148

PostPosted: Tue Sep 24, 2013 4:32 pm    Post subject: Reply with quote

Seems pretty decent breezes today, Tuesday. But ya gotta drive to find it.
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thombiz



Joined: 25 Jun 2007
Posts: 542
Location: Corpus Christi

PostPosted: Wed Sep 25, 2013 12:30 am    Post subject: Reply with quote

Hi Gary, I've redone several board noses and for the most part they turned out well. Here is the approach I would take:
a. Cut the nose off square. This will expose the styrofoam core, and the high density outer foam.
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.
d. Shape the new styrofoam, then bond the new bottom high density foam including the reinforcing overlapping the remaining original reinforcing by 3". Shape the new top high density foam then bond to hull with appropriate reinforcing. The new reinforcing will lap the existing by 3 inches. Then bond the new outside reinforcing being careful to overlap the original reinforcing by about 2" using a tapered overlay.
e. Smooth and finish in the normal way.

I find it easier to use solid high density foam for the frontmost 3" of the nose. I usually just glue together 12 layers of 1/4" high density foam. I also reinforce with about 3 layers of 6 oz s-glass on the frontmost 10" of the nose. For the outermost skin on the top and bottom I use a layer of 6oz. under and a layer of 4 oz over the 6oz. I find I get fewer pinholes to fill by using the 4 oz. over the 6 oz. Be sure to mix in some microballoons into your epoxy to reduce resin weight. It also produces fewer pinholes in the surface. Also, seal your high density foam with a mixture of epoxy and microballoons with a consistency like soft peanut butter. Spread on the top and bottom of the high density foam, let harden, then sand off excess. This will keep the high density foam from wicking up large amounts of epoxy away from the reinforcing, leaving a nearly dry joint and reinforcing.

Bob T.


Last edited by thombiz on Wed Sep 25, 2013 10:51 am; edited 1 time in total
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U2U2U2



Joined: 06 Jul 2001
Posts: 2978
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Wed Sep 25, 2013 10:09 am    Post subject: Reply with quote

for the nose this ?

H100 Divinycell Plain, 6lb./cu.ft., 39.4" X 78.7" (21.53 sq. ft.) rigid PVC (Polyvinyl Chloride) structural foam used in sandwich core construction.


Thanks I now think I can obtain satisfactory results.

I have most of these materials.

Cheers Mate

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thombiz



Joined: 25 Jun 2007
Posts: 542
Location: Corpus Christi

PostPosted: Wed Sep 25, 2013 10:49 am    Post subject: Reply with quote

The Divinycell will work fine, but you will have to seal it as mentioned above. My experience with Divinycell is that it wicks epoxy away from the bond joint more than any other high density foam I have used. Sand the faces of the divinycell smooth, then mix up the epoxy/microballoon slurry and spread on the surface to be sealed using a plastic squeegee, forcing the mix into the surface, then let dry, and sand smooth with 120 grit sandpaper. It sands very easily and once smooth with require very little epoxy to create a good bond joint with the reinforcing.
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U2U2U2



Joined: 06 Jul 2001
Posts: 2978
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Wed Sep 25, 2013 11:22 am    Post subject: Reply with quote

got it.

BTW all the slotboxes I installed have held up great

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swchandler



Joined: 08 Nov 1993
Posts: 5482

PostPosted: Wed Sep 25, 2013 1:51 pm    Post subject: Reply with quote

Bob, as always, you offer great information and advice to do the right job. I always enjoy your practical and well thought out contributions.
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