Hypercarbon, Kevlar, honeycomb, monocoque, fiberglass, composites, carbon fiber… it all sounds very technical, and maybe it’s Greek to you. You’re not alone, most rowers and coaches really have no clue what all the technical terms really mean, or more importantly how it translates to boat durability, stiffness, or speed. So here it is – our multi-part “give-it-to-me-straight, jargon-free” series: Composite Boats 101.Check out Part 1 and Part 2 if you missed them.

Over the past two weeks, we’ve talked about the way racing shells are currently being built – both construction and materials. This week’s post will cover the leftover questions we’re commonly asked about why boats are made the way they are. If you have a question that we may have missed, leave it in the comments section and we’ll get it answered for you.

What’s a “delam”?

“Delamination” (i.e. delam) is when the skin of the boat separates from the core. This happens when boats are dinged or bumped, and the bond between carbon skin and core is damaged. Delams are bad because they compromise a vital aspect of sandwich construction, and without proper repair, will spread. Honeycomb shells are particularly susceptible to delamination since they have such a small, fragile bond area. (See question below about foam core versus honeycomb core.)

What exactly is “shell stiffness” and why is it important?

Shell stiffness refers to the flex of the boat when the pressure of the rower is applied to it. The less stiff a boat is (meaning the more it flexes with each stroke), the less that each rower’s power is going straight to the water, translating to boat speed. In essence, the hull is acting like a huge shock absorber.

Shells can gradually lose stiffness over their life due to wear and tear. When we talk about durability in Pocock boats, one of the things we are referring to is the ability of the shell to maintain its stiffness year after year.

Every boat builder has their own independent flex testing results. You can see ours here.

What is Pre-Preg Carbon?

Carbon and epoxy come together to cure and harden in one of three ways:

• Wet Lay-Up hand applies the epoxy to the carbon once it’s laid in the mold.
• Pre-Preg Carbon comes with the resin already on it (or “pre-impregnated”).
• Infusion Lay-Up is a next-generation technology that uses a vacuum to pull the resin into the carbon fabric. It’s also a greener alternative.

Pre-preg is a one-size-fits-all method that’s the equivalent of “just add water”. It’s good for fast production with little skill required, but the results are far less precise than with the other methods. Pre-preg carbon needs to be stored in freezers, then cured at a high temperature. Rowing shells are cumbersome to move, ovens are expensive to build, and the correct temperatures are practically impossible to maintain. In short, a rowing shell shop is not the right environment for pre-preg carbon to produce optimal results. Instead, you end up with resin that doesn’t reliably cure correctly, which leads to more delams and weaknesses at vulnerable joints. For you that means more repairs, faster degradation of the hull, and shorter shell life.

Pocock boats are built using the wet lay up method. We do it that way despite the additional time and steps involved because when done correctly, it allows us to get optimal strength and stiffness out of the carbon. For you, this means that your shell will be more durable and last longer. Pocock and two European boatbuilders are the only manufacturers using a wet lay up process instead of pre-preg. We’re also using infusion layup manufacturing for some parts where it yields better results.

What’s the difference between foam and honeycomb core?

Honeycomb and foam are both lightweight materials that are sandwiched in between layers of carbon fiber or fiberglass. (See last week’s post to learn more about this production method.) Honeycomb looks just like honeybee honeycomb, and foam is a closed-cell sheet. We use foam because we think that the carbon adheres more completely to the surface, yielding a stronger, more durable construction that leads to far fewer delams down the road.

If you visualize holding a handful of drinking straws and trying to glue a piece of paper to the top of them, it would be tricky. There’s hardly any surface for the paper to glue onto. Same thing with honeycomb – there’s very little surface for the epoxy to adhere to.

What are the pros and cons of Kevlar?

Kevlar is another material that is sometimes used in racing shells. It’s a woven synthetic fiber that is tough, but not an optimal choice for racing shells because once damaged, it’s impossible to restore it to like-new.

Pocock hasn’t used significant amounts of Kevlar in our boats for 7 years, and most other boat builders have phased it out as well. The composites field has gone through significant advances over the past decade, and we now have materials that are much stronger.

What does Pocock do differently to maximize shell stiffness?

Every boat builder is working within the constraints of FISA’s weight minimums. We’re all trying to make the lightest, strongest possible boat. In addition to what we think is the best schedule of composite materials out there, we don’t post-paint our shells as other boat builders do.

Our white coloring is actually a layer of the boat, not a cosmetic paint. A paint job after the boat is built can add up to 15 lbs of extra weight to your boat, and because of FISA’s standards, that’s 15 pounds of “stuff” you don’t have in your boat that would make it more stiff and durable. If you want to know more about our “white-only” approach, you can read more from this recent blog post.