Re: [Paddlewise] Reinforcing Flimsy Back Deck

Dave wrote:
> I have a vintage 1993 Eddyline Wind Dancer, which has a too-light layup
on the
> back deck, aft of the rear hatch.  It's strong enough, but just not rigid
> enough.  
> <snip>
> I suspect it will fail one of
> these days.  So, I have begun to reinforce it with epoxy/glass layers.
> 
> I laid in a sizeable reinforcement patch of 6 oz cloth, but that does not
seem
> to be enough.  <snip>
> 

Strength and rigidity are not necessarily the same thing with fiberglass,
even though Doug Lloyd has his personal preferences for a very stiff  boat.

It's very hard to make specific recommendations without seeing the boat, or
knowing exactly what you want out of the reinforcement, but here are a
couple of things to consider.

A single layer of 6 oz cloth will provide some additional strength, but not
much rigidity.  Better to use 2 or 3 layers of 6 oz cloth - applied at the
same time - which will give the most added strength for the least weight
and added thickness.  The multiple layers of the glass cloth will 'nest'
together better if they are all applied at the same time.  An additional
benefit of using multiple layers applied together is that you have a much
better chance of avoiding pinholes as compared to adding only a single
layer reinforcement.  

A simple experiment - cut out small test swatches of 6 oz cloth, setting up
1, 2, and 3 layer test pieces of the same dimensions (do this on a
polyethylene bag, as the cured epoxy will peel off PE).  Wet them out with
epoxy, using a minimum amount.  After the epoxy cures, compare the
stiffness of the test pieces against the number of layers.  You may be
amazed at how flexible a single layer of fiberglass is :-)  Another
interesting comparison would be to then add a second layer test swatch to
the already-cured single layer, and compare its stiffness - and weight - to
the two-layer-at-once test piece.

If you really want rigidity, you may want to consider using woven roving
(forget if it is 24 or 27 oz. cloth) for the reinforcement.  It will result
in greater stiffness, but not a very water-tight reinforcement (the glass
fibers are very large, but not tightly-woven).  It's also more difficult to
work with in general, especially to coax it to lay flat if there are any
creases in the heavy cloth (e.g. - if it has been stored folded).

With any reinforcement to the inside of the deck, it would be best to have
the reinforcement piece cover the entire deck side-to-side (all the way to
the side seams) to prevent the formation of stress risers at the edges of
the reinforcement(s) that would concentrate flexing stresses there.  

regards,
Erik Sprenne
at the southern end of Lake Michigan (where it's supposed to get into the
50's this week!)

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