Can You Repaired A Plastic Boat Hull With Fiberglass

How to build a foam sandwich composite boat

Foam Sandwich Manual from bateau2.com tutorials

These notes will describe step by step how to build a gunkhole in foam sandwich composite.

The notes below are not about comparing materials, nosotros focus exclusively on building. Advisable foams for the methods we describe below are Divinycell, Klegecell, CoreCell and Airex (2007). We volition only use epoxy as resin: no polyester or vinylester.

Cream sandwich is a well proven material, light and strong. It is particularly well adapted to the edifice of ane-off hulls. It is well suited to apprentice boat edifice because it does not require a female mold or any special equipment.

We will describe what is commonly called the open mold method. In one case you principal the open up mold technique, you can graduate to vacuum bagged or infused hulls. We will focus on the techniques specific to cream sandwich. Please refer to general boat building books for details most edifice steps common to all methods such as strongbacks fix, bulkheads alignment, outfitting, etc.

Most books about boat building draw the techniques nosotros apply in great detail. We recommend "The Gougeon Brothers on Boat Construction".

The techniques we show are common to all hull types, power or sail.

Editor annotation: the current upward to appointment version of this text can exist constitute in the bateau2.com tutorial section.
kiwi

Overview of the hull edifice method:

We will create a foam hull shape effectually a wooden jig, fiberglass the outside, flip the hull, remove the jig and fiberglass the inside peel. Later completion of the hull, the internal components volition be added. The deck will be built the aforementioned way as the hull.

Those familiar with our plywood epoxy (run up and glue blended) method volition recognize the procedure.

The differences in building methods between plywood blended and foam sandwich result from the divergence in stiffness betwixt the ii materials. Plywood is stiff and volition require less molds. In plywood cored blended, the frames and bulkheads tin frequently be used equally molds. In favor of the foam is the ease of cutting and the flexibility: no demand to fight the cadre material while bending the panels or planks.

Cream is more flimsy and must be supported by a more than dense structure. Nosotros volition use either closely spaced molds or battens on molds or a combination of the ii.
A major divergence is the lamination schedule. The fiberglass skins used in cream sandwich are much thicker than in plywood sandwich.

Building a foam sandwich boat stride by step:

• build a jig
• plank the jig with foam panels
• fiberglass the outside
• flip the hull
• remove jig
• fiberglass within
• install internal construction
• install systems: mechanism, tanks, electrical
• build superstructure

In pictures, hull only:

one. Molds	two. Battens (optional)	3. Cream	4. Drinking glass outside	five. Glass inside

This file will focus on the edifice of the hull, deck and structural elements. For the accommodations, systems installation and paint delight see our on line tutorials or refer to specialized books and supplier's technical documentation.

Materials and jig types:

The specifications for the jig such equally the number and spacing of molds and the use of battens depends on the type of core materials: foam sheets or foam strips.

Wide foam canvas planking:

The foam can exist used in large sheets (the size of a plywood sail). In that case, we will oft use scored foam (= contoured foam). Boats with hull panels close to developable surfaces can utilize plain sheets of foam.

pocket-sized piece of contoured foam

Scored or contoured foam is foam with deep cuts on 1 or the two sides. It conforms easily to about any shape.

Jigs/molds:

The battens (or slats) are required to back up the very flimsy sheets of scored foam or to shape the solid foam accurately.

In most cases, battens spaced 6" betwixt centers will suffice. Before installing the cream over the battened molds (sometimes called a slat mold), some builders cover the whole assembly with a canvas of plastic to forbid the resin from leaking through gaps and bonding to the jig.

The cream sheets are commonly attached to the mold past nails or screws.

Those fasteners are removed after the hull is turned over. Headless nails can be pulled through the battens from within.

In some cases, nails with buttons are required. Buttons are pocket-size pieces of plywood acting as a washer.

The slat mold method is the nearly common in professional gunkhole building. A proficient slat mold can be used many times.

It is more labor intensive than strip planking methods non only because of the slats but to employ the large panels requires 2 men.

Next: Foam strip planking

Jacques Mertens
www.bateau.com
Vero Beach, April 2007

The data above is based on Jacques Mertens feel with cream sandwich structure since 1977 and on technical literature from:

• CoreCell
• Airex
• DIAB products: Divinycell, Klegecell, Renicell
• Dupont Nomex
• Nidacore products
• Raptor

Thanks to Evan Gatehouse for the technical proof reading and suggestions.

Thanks to our builders who volunteered to proof read for comprehension and grammar, in detail Glover Housman.

Copyright 2007 Jacques Mertens

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