1 setstats

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.
  
 
K-designs

http://www.ikarus342000.com/CATpage.htm http://www.ikarus342000.com/INTRO.htm
updated 04.10.2006
Routing the deck hull corner on a DUO 800 Mk.I. Besides a Pelican under construction

  plyw./glass/epoxy                           balsacore/glass/epoxy                    foam/glass/epoxy
Okoume plywood 9mm,1m2  = 13,36                   balsacore, 12mm, 1m2     = 26,87          Divinycell H80,12mm,1m2 = 131,08
Spruce 25x25mm 2m #     =  2,40                   Biax.glass 450Gr/m2,1m2  = 38,70          Biax.glass 450gr/m2,2m2 =  65,40
Glass cloth 220Gr/m2,1m2=  5,55                   Glass cloth 220Gr/m2,2m2 = 11,10          Glass cloth 220Gr/m2,1m2=   5,55
Epoxy 0,380 kg          =  4,75                   Epoxy     670 grams      =  8,54          Epoxy      1,12 kg      =  14,06
                                                  Peel ply 1m2 *           =  3,40          Peel ply 2m2 *          =   6,80
                                                                                            Polyfilm **             =   1,92
                                                                                            Suction fleece 2m2 ***  =   7,70
total                  $  26,06                    total                   $ 88,61         total                   $ 239,51

# 2 stringers, * will be removed after curing for better surface, ** material for vacuum pack,
*** necessary to remove excessive Epoxy from the lay-up

Copyright � 2006  by B. Kohler   all rights reserved