The mixture relation of epoxy to hardener has to be accurate. We
use a primitive balance which can be made in minutes. Download the free
BALANCE *drawing and description of charge to make one for your
self.
SKILL
and QUALITY
Everybody can glue pieces of wood i.e. plywood together
as is many times done in a wood/epoxy hull structure. Not a lot of persons
will have the experience to prepare core material ( special PVC foams or
honeycomb ) and apply say a biaxial glass lay up to this core and use vacuum
bonding. You have to learn a new trade with all its un securities. Besides there
is somebody with experience to help you. To mount deck hardware like winches
or sail tracks is easy on a wood boat. Perhaps you have to glue a backing plate
under the deck and thats it. In a sandwich construction, you have to know by
forehand where to place say, a sail track. Then you have to build in a wood
piece in the foam and then you can apply the glass lay up. Besides you have to
add some more layers in a structured way to spread the load. To check the
quality of a wood to wood connection can be done by eye. Good is good, you can
forget about it and go one with the next job. But how to check a good bond
between the core material and the glass laminate in a sandwich construction ?
Delamination is a very well known problem with sandwich constructions even
if the boat is built by professionals.
MONEY Here
we can be very short. Look at the table below. The prices are 2006 prices.
We don�t consider polyester/glass structures, first the are to heavy and
second the don�t last. The table shows the cost for 1 m2
SC 435
construction, a complete hull is made of 19 parts only, including beam pockets.
WEIGHT
It is impossible to build one of my
wood/epoxy designs as light and strong as specified with a polyester/glass
laminate. Very expensive material composites have then to be used. The costs for
these synthetic materials would be about 6 times higher. The prototype
PELICAN has an empty weight of 2200 kgs ( 4846 lbs ) measured on the
derrick as the boat was hoisted into the water. Compare this whit production
multihulls of the same size. The 60 ft. ZEEMAN was built in a western red cedar
/glass/carbon epoxy composite, empty weight = 5300 kg. This is also now a
competitive weight.
First you have
to build a mold. A female mold is out of the question. You will need about the
same time to build the mold as for the complete boat. Besides, a female mold
cost a lot of money. A male mold can be build from particle board and fir,
this will be not expensive. Now you can build up the sandwich lay-up.
After vacuum curing you can release the boat part from the mold. Out of
the female mold will come a hull with a good surface. If anyting wend well, only
light sanding will be necessary to get a boat with a good surface. The hull
from the male mold is a different story. You have to sand and fill many times
before you will end up with a satisfactory surface. I never forget an article in
a German magazine. The guy wrote very proud that his first hull was ready for
painting after one year of work ( it was a 13,5 m long hull ). Pelican number
two was going into the water after one year, built by one person. Why is
this. The most time saving factor is the plywood panel by it self, because
the panel has already a good surface. To safe more time, the panels are epoxy
impregnated flat on the floor before the are cut. The inside surface is then
already finished. The outside is covered whit a layer of glass cloth. Only the
small structure in the glass cloth has to be filled with epoxy putty and the
surface is ready for painting. Every part you build is a piece of structure of
the boat. Compare
this with all the working, which is necessary to build a foam sandwich boat and
it becomes clear why a plywood/glass epoxy boat can be build a lot faster.
updated
04.10.2006
Routing the
deck hull corner on a DUO 800 Mk.I. Besides a Pelican under construction
