Cold Molded Boats

Why do you think you've lost strength with wood? Wood is the superior material.

I used to sail a 150yr old wood boat that still had the vast majority of its original wood and fasteners. When wood has an issue, it will show signs before catastrophic failure. You can fix wood rather easily. Wood is a naturally produced laminate with a bonding agent as strong as most we produce. All in all, the only material really better longevity wise for building boats out of than wood is 90/10 copper nickel.

No wood was a good marketing mantra because people associate wood with work, they just weren't telling you what work you were trading woodwork for. Every material requires work and has a life limit and failure threshold. "No wood" means whatever the consumer is smart and experienced enough to assign it.

You are fine. Blackwell builds a bulletproof boat. Don't let this crap falling apart bother you your boat is built with the finest woods and epoxies no comparisions to this polyester foam cored improperly built mess.

Those Carolina boys would never build a boat that they would not want to be caught out 60 miles off Hatteras in the worst weather they could see.They staked their lives on their boats long before they started building them for the general public.

And there lies the problem

You've got that dead on. It doesn't matter near as much of what the boat was built of as it does who built the boat, and I'm talking the guys on the shop floor, even moreso than the management. Although management can shoot down good guys on the floor by giving them inferior materials and have them build to insufficient spec.

Up north, the wet/dry/wet/dry/wet/dry cycle encourages rot in the lower sections of the boat (not just the bilge). Dry rot fungus also finds its way wherever there is wood.

So the "no wood" sales pitch was the "no rot" sales pitch.

Every material is a compromise for certain people in certain situations.

I think Ken Bracewell can probably tell some stories about how sound wood can be (or not be) even with the best builders when there isn't the best maintenance.

Wood is Good!

From Chapter 8 of the US Forest Products Handbook

"8.6 Wood Degradation and Protection
In the absence of biological attack (due to fungi and insects), the degradation of wood under rain and ultra-violet light occurs at a very slow rate - the surface layer is removed by 1 mm per 20 years. Biological attack is therefore the major cause of wood deterioration.
Fungi are low forms of plant, which grows through the wood, using cell walls as food. With fungal attack, wood becomes brittle and weak. In order for fungi to grow in wood, there need to be a proper temperature, a moisture content above 19% (except for a special fungus called house fungus which can live and grow under much dryer conditions) and an ample supply of oxygen. Therefore, when wood is dry, or completely immersed in water (so the supply of oxygen is low), fungal attack is not a problem. When wood is in contact with soil ground, where water tends to be collected, degradation occurs at the fastest rate. Besides fungi, insects also attack wood. Insects such as termites, carpenter ants and marine borers (which live in salt water) literally eat up wood as they all use wood as their food.
The simplest way to protect wood from fungal attack is to cover it with paints, stains or waterproofing chemicals. The penetration of these materials into wood is, however, quite limited. Surface cracks or splits can allow water to get into the underlying wood. For reliable protection against both fungal attack and insects, pressure treatment needs to be carried out. Chemicals are injected under pressure into the wood. In most cases, the wood surface is incised by toothed rolls to allow the chemical to be impregnated deep into the wood. Common chemicals employed for this process includes pentachlorophenol, creosote and inorganix arsenicals. These chemicals are effective for controlling both fungal attack and insect attack. "

In the end Fiberglass is popular as it is low maintenance.

Improper design and construction techniques will still ruin the best materials.

In my experience people these days use the term "cold-molded wood" to include multi-layered wood construction (typically marine ply strip laid diagonally) over a male mold form as well as strip plank molded construction (often cedar or similar). However, it is almost universal that the hull is then encapsulated in an FRP outer skin which adds both stability/strength and secures lower maintenance. Equally, and for similar reasons I believe, the interior exposed wood surface is normally resin saturated but often with added FRP reinforcements abutting any ribs, stringers,floors or bulkheads - if not otherwise fully encapsulated in FRP too.

The result is another form of composite vessel really with the wood forming the core rather than providing the total structure. Such methods typically provides a strong, relatively light structure and has been commonly used for racing boats and many high end custom builds.

The chances for water ingress are minor and maintenance performance is similar to any plastic fabrication. It would be rare if any modern cold-molded wooden boat was really, in effect, a wooden boat in the traditional sense and the issues of wood deterioration are largely irrelevant. I detect a prejudice against wood by some but it may be through a lack of understanding about modern methods for its use. No caulking needed these days that's for sure!

Yep, no "paying the Devil" on a cold mold.

Been a while since I heard that old expression! However with any male molded vessel the quid pro quo is the long boarding to fair the hull! Henning , have they invented a salty sailor's expression for that penance yet?

Missed the Message - "Wood is Good"

Blair

I think you missed the point of my post.

"Improper design and construction techniques will still ruin the best materials."

In the end these type of debates are about an optimization exercise and design aesthetics.

BTW - Cold Molding is a cost effective way to build Custom and Low Rate production components...

TGIF...

Hi all,

I would have to second SandEngXp statement - "Improper design and construction techniques will still ruin the best materials." And the whole Bertram-Gate was a great example of this. You see it in formula 1 e.g. When the rear spoiler falls off when just going along the straight under aero load.

Also, would love to get feed back on a cold molded hull with a lay-up of Kevlar on the outside and inside of the hull for impact strength. I’ve noticed a few custom builders using this setup? And why isn’t there any/many more builders using this same setup/tech?

Far

I worked on a cold mold (3 layers wood, Port Orford cedar) where we put the Kevlar between the layers as well as the base layer on the outside with glass on top of that and glass and carbon on the inside.

One-Offs

Just don't put it on the far outside layer as the long board crew will have your hide.... ....done that twice....

This would be a good way to improve the point load/point impact resistance of this type of construction as it balances up the strength of the combined laminate while still having the benefit of the high specific stiffness of the wood. In addition on the far inside layer it provides best use of Kevlar's 2x higher tensile strength v. compression strength. ( Concrete in Reverse. )

I think one of the biggest problems in todays construction is the use of vacumn bagging? Everything has to be just right, amount of resin and glass, environment, or it's a waste of time. You would think that since this technique has been used for many years now, that there would be better quality control and standards that have to be met?