[Alberg30] Deck Coring

[George Dinwiddie]

I don't trust option 1 for the long term.  For one thing, it's
very hard to get the core really dry, and epoxy doesn't bond
very well to water.  I'm not sure how well it bonds to shreds
of dirty rotten core, either.  Actually, I'm sure it will bond
to that, but that may get in the way of good bonding to the 
glass.  And you still generally end up having to do major
cosmetic work when you're done.

I also don't know why you've already decided on epoxy resin?  Why?

My choice was Klegecell for the core.  I don't have the part number
handy, but it was the highest density foam core sold by Fiberglass
Coatings, Inc.  I get the flat sheets and cut as needed.  I bedded
the core in polyester resing thickened (mayonaise) with one of the
W.E.S.T. products, cabosil, or glass beads.  

For the layup, I used a mat/cloth/mat schedule using (from memory,
not guaranteed) 1.5 oz. mat and 8 oz. cloth.  I continued to add
layers of mat on top until I reached the level I needed.  Of course,
you won't be able to use this schedule if you use epoxy, as the 
binders in the mat is incompatible with epoxy resins.

People often assume (I certainly used to.) that epoxy is better
than polyester.  Not necessarily so.  It has advantages and
disadvantages.

In my experience, and in the advice of Tim Silvio (the best glass
man I know), epoxy resins are trickier to work with.  You need to
be precise in your measurements and you have to adjust by using
different hardeners, not by adjusting the amount of hardener.
Polyester, on the other hand, is pretty forgiving.  For the
amateur, I think it's a clear winner for most projects.  Even
for the pro, I'm not sure it's cost-effective to put patches 
of epoxy layup on a polyester boat.

If you want some hands-on lessons, you can come over.  I've still
got some small areas that need attention. ;-)  The areas I've done,
lower deckhouse, lazarette and cockpit sole, are rock-solid.

 - George

> C.B. Currier said:
> 
> One of my boats Daybreak #458 has evidently had severe deck core rotting to
> the point where It should be repaired(extreme spongieness/flexing of deck).
> I have been evaluating this for the past year and have not really come up
> with a decisive direction to move in. It is a shame since the actual
> majority of the deck looks good. I mean - the deck flexes on the foredeck
> appreciably and in the stern. No flex on top of the cabin or along the rail
> port & starboard.
> 
> I know that the two options really open to me are as follows:
> 
> 1. drill, rout, fill w/epoxy-microfibers compound all over the place
> 
> 2. Cut off the deck secion by section, put new core (foam: which type ?)
> epoxy in, glass over - apply noskid
> 
> the Question:
>     is #1 a good reliable cheap way of doing this repair, regardless of the
> issue of leaving the old rotten remains of the core ? Has any one done this
> job lets say in the past ten years and had poor results? How about good
> results?
> 
>     If I go with # 2 which foam and glass should I use, how thick? I am
> already resolved to using MAAS epoxy so the other details are more important
> to me.

-- 
 ----------------------------------------------------------------------
  George Dinwiddie                             gdinwiddie at alberg30.org
  The gods do not deduct from man's allotted span those hours spent in
  sailing.                                    http://www.Alberg30.org/
 ----------------------------------------------------------------------

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