The Offshore Voyaging Reference Site

Characteristics of Boat Building Materials

iStock_000019140769Small

A sure way to start a fight on a boating forum is to ask what the best boatbuilding material is. If you do, you’ll likely be rewarded with a drawn-out battle between the metal-heads, the wood lovers and the plastic addicts, running to hundreds of posts before getting either modded or Godwinned to oblivion.

The reason nobody ever gets a clear win in these fights is because there is no generally applicable right answer. Most private vessels in the 20 to 100 foot range fall very near the balancing point where you could get excellent results in aluminum, fibreglass or wood composite, and a significant fraction of those boats could be built equally well in steel or in traditional wood methods. What really matters is whether it’s designed and built correctly—it’s quite possible to build a modern ultralight ocean racer out of wood, and it’s quite possible to spend a few million dollars on a wallowing pig made from the finest aerospace composites.

That being said, there are quantitative ways to compare the structural properties of different materials, and we’ll look at a few of them today.


Login to continue reading (scroll down)

More Articles From Online Book: How To Buy a Cruising Boat:

  1. The Right Way to Buy a Boat…And The Wrong Way
  2. Is It a Need or a Want?
  3. Buying a Boat—A Different Way To Think About Price
  4. Buying a Cruising Boat—Five Tips for The Half-Assed Option
  5. Are Refits Worth It?
  6. Buying a Boat—Never Say Never
  7. Selecting The Right Hull Form
  8. Five Ways That Bad Boats Happen
  9. How Weight Affects Boat Performance and Motion Comfort
  10. Easily Driven Boats Are Better
  11. 12 Tips To Avoid Ruining Our Easily Driven Sailboat
  12. Learn From The Designers
  13. You May Need a Bigger Boat Than You Think
  14. Sail Area: Overlap, Multihulls, And Racing Rules
  15. 8 Tips For a Great Cruising Boat Interior Arrangement
  16. Of Cockpits, Wheelhouses And Engine Rooms
  17. Offshore Sailboat Keel Types
  18. Cockpits—Part 1, Safe and Seamanlike
  19. Cockpits—Part 2, Visibility and Ergonomics
  20. Offshore Sailboat Winches, Selection and Positioning
  21. Choosing a Cruising Boat—Shelter
  22. Choosing A Cruising Boat—Shade and Ventilation
  23. Pitfalls to Avoid When Buying a New Voyaging Boat
  24. Cyclical Loading: Why Offshore Sailing Is So Hard On A Boat
  25. Cycle Loading—8 Tips for Boat and Gear Purchases
  26. Characteristics of Boat Building Materials
  27. Impact Resistance—How Hull Materials Respond to Impacts
  28. Impact Resistance—Two Collision Scenarios
  29. Hull Materials, Which Is Best?
  30. The Five Things We Need to Check When Buying a Boat
  31. Six Warnings About Buying Fibreglass Boats
  32. Buying a Fibreglass Boat—Hiring a Surveyor and Managing the Survey
  33. What We Need to Know About Moisture Meters and Wet Fibreglass Laminate
  34. US$30,000 Starter Cruiser—Part 1, How We Shopped For Our First Cruising Sailboat
  35. US$30,000 Starter Cruiser—Part 2, The Boat We Bought
  36. US$30,000 Starter Cruiser—How It’s Working Out
  37. Q&A, What’s the Maximum Sailboat Size For a Couple?
  38. At What Age should You Stop Sailing And Buy a Motorboat?
  39. A Motorsailer For Offshore Voyaging?
  40. The Two Biggest Lies Yacht Brokers Tell
42 Comments
Oldest
Newest
Inline Feedbacks
View all comments
Colin Speedie

Great post, Matt.

And proof yet again (as you point out) that it’s the design and build process that makes all the difference.

I’m looking forward to the future posts already!

Best wishes

Colin

Dick Stevenson

Matt, Nice analysis, well presented, and it is a help to have the comments about different materials side by side. I am continually impressed by how often these discussions come down to the skill of execution rather than outright choice of material and I suspect most of the bar-room controversy stems from this source rather than materials. As you say, materials reveal themselves clearly while construction skill is often masked.
Dick Stevenson, s/v Alchemy, St. Petersburg, Russia

Justin Catterall

Matt, thank you for the very interesting post… and putting your cards on the table. It may have been posted elsewhere, and I’ve missed it, but to see that you’re building a strip-planked wood/epoxy trimaran is most interesting. I think you’re daft[1], but it’s very interesting.

Justin C, by the sea.

1. If it’s just another Dragonfly then what’s the point, if it’s another B&Q then, Wow! WTF, good luck, and you kick ass! … but you’re still daft[2].

2. …’cos I can’t see the appeal – but what do I know, I want a moderate to heavy displacement cutter/ketch, and I don’t care what it’s made from (within reason).

FAIVET DANIEL

Bonjour
Cet article généralise la plupart des matériaux utilises dans la construction navale, a l exception du ferro- ciment ( qui a été abandonne)
C ‘est difficile a comparer sans inclure les techniques de fabrication qui doivent être appliquées dans les règles de l art
En fait je rejoins l analyse de l auteur de cet article , il n y a pas de meilleur matériaux mais du savoir faire dans chacun d eux ?…. D Faivet

Ken Page

Is there to anyone’s knowledge someone who’s tried wood laminate layered with fiberglass mat in epoxy? By that I mean a veneer of wood, a layer of mat, then wood, then mat etc, etc? Maybe I’m missing a major weakness to that method but it seems to me that it can’t be that far fetched. What if a thin layer of mat was woven with veneers and crossed diagonally, would that benefit somehow a cheaper build cost with added strength? I’m just throwing ideas, maybe worthless I know.

Eric Klem

Ken,

The trick when combining materials is to get them to carry the share of the load that you want. To carry any load, a material must deflect. Therefore, you generally need materials with similar values for Young’s Modulus if you want to be able to distribute the load between them. If one material is much stiffer than the other, it will carry basically all of the load until it yields.

Another thing is as Matt pointed out, the bigger the structure, the more load it can carry(for example an I beam). Designers generally try to put two strong materials at the extremes then attached them together with something very light and less strong. Balsa cored hulls are a perfect example of this and they work really well provided that no water gets in. My first statement still applies to these hulls as the outer skins carry the vast majority of the load.

I do not know of anyone trying what you describe but someone may have done it. I hope that this makes sense and is helpful.

Eric

RDE

Exactly right Eric
Putting matt in between layers of a cold molded hull would simply weaken it on a weight basis by adding excess resin on the neutral axis of the quasi-beam structure where it contributes little to stiffness. At the same weight it would end up being thinner and thus less efficient in bending stiffness.

One point: balsa cored hulls produced by epoxy resin infusion are no more susceptible to damage from water intrusion than foam cored ones because each individual balsa block is isolated by an impermeable epoxy resin barrier that precludes moisture migration. Precisely because of this resin absorption into the core they are substantially heavier than an equally stiff foam core structure.

Erik de Jong

There is 1 yard in the Netherlands that I know of combining wood and fibers in that way. “Waarschip”, see: http://www.waarschip.com/new/, has been building plywood boats for over 50 years now. I think it was in the early 90’s when they started advertising that they could build their boats with Aramid reinforced plywood. It was a plywood type with a thin aramid sheet between the individual layers of wood.

One of the things you run into when designing a boat, is minimum plate thickness or slenderness of structures. For steel, you can’t go thinner than 3mm in order to weld it properly, that is a lot stronger than you need for a deck plate for example, but you don’t really have a choice. For aluminum, the same story, welding thinner material than 4mm is going to be problematic.
Plywood boats are a lot stiffer than you need for a boat, because you need a minimum thickness for your impact resistance. “Waarschip” introduced the plywood-aramid plates for this specific reason, the plywood only has half or a third of the regular plywood thickness, but due to the aramid fibres, a better impact resistance compared to the regular plywood previously used.

With this method, they successfully reduced the weight of their plywood boats significantly while maintaining a great hull stiffness, and a more than usual impact resistance.

When I was attending university (Naval architecture), I’ve seen some comparative lab tests of this plywood and regular plywood, and it impressed the living h#ll out of me I must say.

Unfortunately, the yard went through several bankruptcies, several restarts and several owner changes in less than a decade, and the aramid-plywood does not seem to have survived these changes.
Too bad, it was a really great yard, my brother still owns one of these boats, very low maintenance, and virtually indestructible. For reference: his Waarschip 1010 is 34ft and weighs only 2100 kg including 1000kg of cast iron keel and has been hard-raced (offshore) since 1983.

Best regards,
Erik de Jong

John Harries

Hi Ken,

If you would like a more in depth expansion on Eric and RDE’s excellent replies, you might want to read this post by Matt that really helped me understand the issues in mixing materials.