Hull Construction

[fretbrner]

Hey everyone. I have put in an offer on a boat but there was one thing that seemed different about the hull that I haven't seen before. Usually it is just fiberglass throughout. To be honest, I have not been on many boats built in the 80's as this one is from.

The picture shows an example of these bars running that run fore and aft the whole length and only out in the opening in the head. I am assuming they would essentially be the stringers and the ribs?

This was not a home built hull and it comes with the original plans from the factory.

Anyone else see this in a fiberglass boat?

[atoll]

not uncommon to find stringers formed using cardboard tube cut in half lenth ways or PU foam ,which is then laminated on top in older production boats to provide stiffness.

newer production boats generally have a lattice type interiour moulding these days that incorporates the floor and notches for bulkheads etc,as well as a ceiling moulding.

these are glued to the hull with bonding paste or epoxy rather than laminated these days,to save weight and labour

[Franziska]

The cardboard or PU stringer "former" are perfectly fine. Their only purpose is to shape the stinger.
The actual load bearing is done by the laminate on top of these formers.

PU stringer former have the advantage that water can not fill the hollow stringer system if it ingresses somewhere.
Some people actually made little drain holes at the lower end of stringer systems.

Usually you'll find those stringer systems on non sandwich one off constructions.
Production boats are built with tray moldings as stated above.

[billknny]

Not only is this 100% normal on any hull that is made of solid fiberglass--it is required. Many boats have just fore and aft stringers. This was laid up by somebody who wanted to be SURE the boat was stiff and was willing to spend extra labor to do that.

Solid fiberglass as a construction material is very strong, and very tough, but is not very stiff. These are the ribs and stringers to add that required stiffness. They can be molded into shape in lots of different ways, foam, wood, yes, even cardboard tubes. The material inside is not important, it the the overlay of fiberglass that is what adds the required stiffness to the hull.

Cored hulls are a lot lighter and stiffer, but less "tough". Every thing is a compromise. Because for the extra stiffness, cored hulls can sometimes skip the molded stringers, or have them much more widely placed.