Peter,

We have been spar and boat builders a very long time.

I believe that you are wrong about epoxy shear strength.

If you remember breaking the very brittle pieces of linen and FR that
protruded from the completed joint, you should understand the problem
with FR. The woodworking epoxies don't get that brittle. This helps to
prevent the joint shear failure that is the common mode of a spruce/FR
structure.

We started the change to epoxy from FR about 40 years ago. It was a
carefully orchestrated and cautiously arranged so no work that went to
any client would ever be at risk with an untried application.

Spars were the last conversion. We made the family DNs masts with epoxy
in the late 60's. Two (that I know about) of the FR spars failed in
the in the next five years - both were joint failures - neither was
catastrophic, but visible splits developed in the varnish.

During Fall Off Soundings 1968, I made a mistake with that season's new
spinnaker pole. It got flexed so badly that the varnish flaked off both
the compression and tensile sides (it was hollow spruce done in four
grooved staves) but the finish was still intact along the joints. (My
father was not pleased with me and I got to refinish the pole before the
next race.)

Matt Colie

Peter Hendra wrote:
On Fri, 9 Mar 2007 07:51:16 +0100, "Meindert Sprang"
wrote:

"g" wrote in message
...
I used this kind of glue when I made my boat.
Resorcinol glue is a waterproof two-part system that meets or exceeds the
requirements of MIL-A-46051 (Type 1, Grade A), (Type II, Grade C), and
MIL-A-22397 (Grade A). It resists outdoor exposure, cold or boiling water,
heat, molds, and solvents. Pot life: 3-4 hrs. Mix Ratio: 4 to 1 by weight.
Excellent for use on wood structures.
But but but..... resorcinol needs an exact fit between both parts and then
you need to clamp the parts together. There is no way you can glue to panels
or strakes of a boat together with that, let alone make fillets. There is
only one glue that allows this: epoxy (with a proper filler).

Meindert

Hi Meindert,
Agreed in principle, but..... I built my yacht triple diagonal over
stringers with resorcinol before sheathing it with glass cloth and
epoxy. Where I couldn't clamp the first layer to the stringers I
screwed them down through a block of waste wood and removed the screws
later - thus no gaps. In other places and for the second and third
layers I used bronze serated boat nails and punched them flush. What I
like about using resorcinol, apart from its aforementioned virtues is
the pot life. Also, epoxy has no sheer strength. Taking advice from
professional wooden mast builders, I glued my box section 45 foot
wooden mast together with it. To this day, not a problem. Most
resorcinol needs a thickening agent. I bought a powder made from
ground up olive pitts of all things. A factory that makes ply near me
uses ordinary domestic flour.

A tip that someone gave me for using epoxy after I had almost finished
building. To "clamp" wood such as mouldings firmly and correctly in
place when you do not want to nail or screw and cannot apply a G or F
clamp, apply epoxy along the join excepting for a couple of small
spots. Apply a dab or molten glue from a hot glue gun and then hold it
in place for 30 seconds. It does not move at all. Saves one hell of a
lot of frustration especially when pressure from a clamp causes it to
slide.

cheers
Peter
N.Z. yacht Herodotus

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