11507Re: Can of worms question....(long)
- Nov 1, 2005Hey,
I'm with Chuck. I think you're comparing apples and oranges.
I used lots of PL on the light schooner, but that is with ring nails.
The two help reinforce each other, but the PL isn't much good without
the nails. It's TOO flexible.
Epoxy, however, is a rigid plastic. And it's generally used with glass
fabric to vastly increase gluing area.
So, apples and oranges. PL is great for nail & glue, but not all hull
forms are easily realized with this method.
But I think the MAIN thing is that you can't compare nail/glue joints
with glue only joints. Glue only grabs the glued SURFACE, so the piece
itself can more easily rupture. A mechanically fastened joint reaches
all the way through at least one of the parts, the fasteners adding
their strength to that of the part.
--- In Michalak@yahoogroups.com, "mrusson" <mrusson@g...> wrote:
> Dear Group,
> I wanted to ask the groups opinion about PL Premium versus the ever
> popular Epoxy. After some research into polyurethane adhesives such as
> PL and 3M 5200, i learned something. After looking into the flexural,
> adhesion and modular properties of polyurethane, i began to like it a
> bit more. It was mentioned to me that using a polyurethane adhesive to
> glue butt blocks or structural areas was a bad idea. After looking into
> the combination of mechanical fasteners used with PL adhesives, i don't
> worry so much about the joint. PL exhibits a flexural advantage over
> Epoxy in that it can absorb blunt flexural impacts and not fracture.
> Epoxy on the other hand reaches a point where the resin actually
> breaks. I did a few little tests at home this week and came up with the
> following. After glueing two pieces of 1/2 AC ply together, with no
> surface prep, i observed that the PL bond compared to the epoxy bond,
> actually held up better in a direct impact. I smashed the joints using
> a 200 pound anvil hung from a ceiling hoist in my garage. The joint was
> impacted from the side at the same height and weight each time. The
> epoxy cracked under impact where the PL did not. Surface delamination
> of the AC ply glued with PL was about as severe as epoxy. I admit this
> is a low tech test with no real data, but i can definately see the
> strength associated with Polyurethane adhesives. Food for thought i
> M Russon
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