Used Sailboat Hull Design, Evolving Opinion:

When reviewing blue water sailboats for sale, know your heart’s position on Cored-Hull vs Solid Glass.  

Traditionally, I preferred sailboats with a cored hull as if it were Integrity’s hallmark.  Cored hulls have been the practice of solid names like Southern Cross, Pacific Sea Craft, and Gozzard (although other quality builders use solid glass).  These proven sure footed ocean going sailboats, if maintained, are worthy options in the used sailboat market (trumping opinions on core vs solid glass).  

By “cored hull” I am referring to one layer of glass at least 3/16 inch thick fiberglass pressed against a synthetic layer of core .5 to 1 inch thick.  

I say “synthetic” because, despite it’s weight, stiffness, and cost benefits, balsa wood (common core material) has no place on a blue water cruisers- Not even in the deck (although hard to avoid).  There is no balsa aboard Shannon or Island Packet Yachts.  When balsa gets wet, and it will (despite what the sales person says), it turns to mush.  So Balsa is great when new but this article is for used sailboats buyers and we like synthetic core.  

Cored hulls have benefits. Simply put, they’re thicker.  Cored hulls offer insulation from temperature and possibly sound.  It’s almost like having two hulls so when a floating object lacerates your outer hull, your boat keeps sailing if your inner hull remains uncompromised.  Lastly cored hulls present fewer condensation issues inside (most applicable in extreme temperatures).

While these benefits are real and hold value, cored hulls, present an opportunity for moisture to collect where it can’t be dried.  Even if owners use proper methods to fill holes when adding fixtures, the two layers of glass create a chamber which, over decades, traps moisture. What happens when that collects and freezes? What is it’s impact on the glass and the core it self?  These are unknowns and when helping customers find a 25+ year old used sailboat to carry them over the horizon, I prefer fewer unknowns below the waterline. 

My current boat has an air-x cored hull.  I feel safe with her integrity but if privileged to buy another boat someday, I’m drifting towards ocean going sailboats with solid glass hulls.  There is simplicity in it.  You have fewer unknowns as the water meter readings really tell the story.  You know what you’ve got which inspires confidence in your boat.  When far from land and help that confidence is priceless.  John Kretschmer (sailed over twenty Transatlantic crossings) refers to the value of “confidence in what your boat can do” as essential to successful storm sailing.

Lastly, I’ll leave you with some quotes from sailors I respect.

“I prefer solid, un-cored hulls below the waterline.  I appreciate the advantages of cored hulls, especially in the topsides and deck, where they reduce weight and offer strength in certain applications.  But down south (below the water line) I want solid glass.”

-John Kretschmer:  Sailing a Serious Ocean International Marine. 

Boaters’ Rules of Thumb #72

Hull thickness, solid fiberglass: The general rule is that skin thickness in inches should equal at least 0.07 plus the waterline length in feet divided by 150.”

- John Vigor: Seaworthy Offshore Sailboat: A Guide to Essential Features, Handling, and Gear (Mar 21, 2001)