Hull Construction Questions

[Jeff]

Sail Magazine's Sept edition has some great info on how fibreglass boats are built and a list of questions boatbuyers should ask about hull construction. Does anyone know if Beneteau (or other builders like Hunter and Catalina) have detailed info available on their hull construction materials and techniques to allow a purchaser to assess and compare build quality. Questions I'm looking for answers on are on things like:What is the Gelcoat/exterior finish above and below the water line?What is the principal resin used in the hull laminate ie. epoxy, vinylester, etc.How are the hull and deck laid up? ie. vacume bagged, CSM, chopper gun, etcWhat is the predominant hull material used ie. unidirectional, biaxial cloth, woven rovings, CSM or Chopper Gun? What is the fibre/resin ratio? ie. 70%, 50%, 30%How are hull-to-deck joints sealed? What is sealant?What mechanical fasteners are used and on what spacing? bolts, screws, rivets, etc.  If anyone has any insights on this info and where to get it, pls advise, thx.

 

[Jack]

Good Question

It used to be that layup schedules were closely held. I would like to know the answers to the questions you asked.

 

[Robert W. Bonney]

Beneteau

I recently ordered the brocures and schematics from Beneteau on several of their boats. I don't have them with me but will check them when I get home. I believe they answer some of these questions.

 

[Joe Dickson]

Check the Hunter Reference Library on this site...

There is a section in the reference library called Hunter Q

 

[jcherubini]

Hull core samples.

At Cherubini Boat we used to save all the through-hull cutouts for the customer's inspection. They were cut with a hole saw and we strung them on a little piece of line thorugh the mandrel (pilot) holes. From these, taken from various places above and below the waterine, we were able to use them to show gelcoat thickness, outer mat, quantity of structural textile, and especially the quality of the resin saturation. In the days before vacuum-bagging, lay-up could be hit or miss with some builders (not us however!!).I strongly recommend that anyone ordering a boat from the factory insist on these core samples from the actual hull they are buying. Previous owners may have such samples from work they did or may have kept the ones the factory gave them (a bit dusty but good paperweights!). Also the builder ought to provide specifications on how the hull is laid up and what the various layers are. If they can't, they may be leaving it up to the 'glass shop, which will not suggest a consistent procedure.Moulders will use plain mat at the outside (against the mould) because it avoids print-through and provides a smooth surface, but too much mat will not be strong (a Corvette is almost ALL mat). Mat is just hair and glue. Once the trixial or Fabmat starts coming is where you see strength. Modern builders use various single-strand cloths but on various angles in order to simulate multi-axial lay-up; this is good but there can be waste there as well. It sounds 'duhhh!' but the goal is the best strength with the least weightÐ- a heavy bare hull does nothing for boat performance. And too much resin (more green or blue in the core and less white or grey) signifies a very hasty or careless lay-up which will result in a very brittle hull-- this, unfortunately, is common, as shooting resin is cheaper than laying up textile and the thickness can be the same.At Cherubini Boat back in the '70s we were noted in the industry for having one of the most sledgehammer-proof hulls in the world-- a full 2 inches of mostly Fabmat at the turn of the bilge along the keel!!! By today's standards this would be overkillÐ- but nearly 30 years on, the hulls are still robust and there probably aren't ANY not intact.There is simply NO replacement for a solid hull lay-up (and no cure for a bad one) and so every opportunity to investigate integrity in this area on an older used boat ought to be taken.JC 2