Wood Choices for Cold Molding

Why is that?

 

Coldmolding doesn't always use veneers. Strip planking is also a form of cold molding. If you are going to laminate with fiberglass over it, strip planking is cheaper and faster.

 

Hi Toot, I have found this brief but accurate description of what wood cold molding is in boatbuilding:
http://www.oceanpix.co.uk/Boat-Building-Guide/Boat-Building-overview.htm

 

Thanks for that. It's surprising to me how different the nautical methods for low-volume composite construction are from the aerospace methods. And heck, apparently sometimes things that sound like composite construction techniques are really nothing of the sort!

Thanks for the assistance.

 

100 gallons of resin seems like a lot. However, in amateur construction, time and materials are much higher.

 

Hi Gonzo, I agree 100 gallons seems very high for essentially a sheet plywood construction. Works out at 1 gallon per every sheet of 8ft x 4ft. sheet of ply.
I wonder how much got wasted? What is the cost of epoxy and 3/8" marine ply in the US? Am I right to estimate that the marine ply and the epoxy alone would be in excess of US$16000? If so I wonder what Michelle spent on Moondancer all up, not including the value of the time spent constructing?

 

Because plywood is essentially air and resin tight. The holes allow equalization of pressures on both sides of the ply, they reduce the possibility of pools or bubbles forming between layers, and they are a place for excess resin to go.

Tad

 

I may be really nitpicky, but I think strip-planking is a form of strip-planking

Strip-planking usually refers to square or rectangular strips of wood placed at roughly zero degrees to the centerline, usually with edge fastenings of some form. Sometimes strip-planking is sheathed with glass or other fabric outside, or on both sides. Sometimes a strip-planked hull will have frames, sometimes not.

Cold-molding refers to the building up of hull planking using multiple thinner laminations of wood, usually oriented in various directions.

Sometimes (as I mentioned further up this thread) strip-planking is sheathed or cored with diagonal layers of planking, and the whole works is referred to as cold-molded. The biggest boat I've done this way is Scheherazade, at 154', her cold-molded hull is 3.5" thick in six layers, the inner and outer are 13/16" fir running fore and aft, the middle four layers are 7/16" red cedar, all diagonal.

Tad

 

There is strip planking, there is cold-molding, and there is a combination of the two.

You see, the mold needed for strip planking is very basic and simple compared to the mold needed for cold-molding. If you strip-plank the first layer, then cold-mold the next two layers, you can save a lot of time without sacrificing much strength or weight. Plus, the interior looks pretty since the inner skin is running fore-and-aft. If you carefully read a previous reply this method is briefly mentioned.

Anyhow- a book by Hub Miller called "The Laminated Wood Boatbuilder" discusses EVERYTHING you'll want to know on the subject! I bought my copy from Amazon. I, too, am designing a cruiser (albiet sail) and considering this method of building the hull.

 

Tad Can you comment on this thread?

http://www.boatdesign.net/forums/showthread.php?t=13081&goto=newpost

FL I apoligise for highjacking your thread....

Ray

 

Fastlearner,
I don't think anyone has even addressed your question of where to purchase cold molding lumber. I'm looking for that answer as well.
Cold molding whether with a foam or wood strip core, eliminating the female mold, is pretty much the only viable option for building large one off high end wooden vessels unless you want to build replica.
I'm sure that statement will raise some eyebrows

 

chandler,

In the classified section of the current issue of WoodenBoat I find at least 3 companies advertising cold molding veneer, and a number saying they supply custom cut boat lumber. I don't know what "reasonable cost" is anymore, it seems to me that all costs these days are unreasonable!

Ravenwood Services 10877-528-9453
Fir and Cedar milled to your spec 360-385-9022
Woods Unlimited 510-895-2619
White Cedar 207-354-0511
Classic Yacht Services 250-743-3837
West Wind Hardwood 1-800-667-2275

Let us know what you find.

Tad

 

Just my $.02

As an experienced (and admittedly amateur) builder, I will vouch for cold molding as a technique that's very much alive and thriving, at least where I am (New England). I also personally know of at least two champion sport fisherman builders in the Mid-atlantic region who only build cold-molded for boats up to 50' and have a passionate, loyal following.

I have built both strip planked and built up boats and I much prefer the built-up cold molded boats. I've also been taught many tricks to increase strength/reduce cost by builders more knowledgable and experienced than myself, such as using polyurethane adhesives between laminations instead of epoxy.

Cold-molding is slower than some other construction methods but it's faster, more cost effective, and reliably strong for the amateur. Defintely more so than, say building a mold and/or trying to hand-lay fiberglass. I've witnessed many abandoned amateur projects where someone tried to get too ambitious with fiberglass and wound up with a giant sticky unusable mess.

The primary benefit of cold molding in plywood veneers is you can get a sense of the hull shape prior to spending serious money. While building bulkheads and station molds isn't cheap, the overwhelming majority of the hull costs are in the plywood and glass. Once the station molds are installed on a stronback and the stringers in place, the builder has a very good sense of the hull shape and can fair out any bumps or wobbles. Even during the lamination process, it's easy to take off high spots between layers. You certainly can't do that with molded FG - it's either fair or it isn't.

I am currently getting ready to bring what will be my largest project to date off the boards and into the shop - a 37' cold-molded single-diesel motorcruiser based on a lobster boat hull design. It will be cold-molded to 1 1/8" hull thickness and glassed, and designed for use as a three-season liveaboard here in New England. I have no qualms about going cold-molded. It's a technique I know to be reliable, economical, and proven.

 

On the Island of Manteo just inside Nags Head there are more than forty builders of "Carolina style" sport fishermen. This does not include builders in other parts of the NC coast or in SC. Most are in the range of 40 to 67 feet and cost up to 2 mil or more. Except for a few who still strip plank with white cedar (juniper) most are cold molded plywood. A couple tried to do molds for fiberglass hull but the clients all wanted their "own" boat and the molds could not be economically amortized so they all went back to wood, which the clients like better anyway. There are some commercially built so called sport fishermen, say Hatteras, but they are not considered by many of the local as good boats. All the same and too heavy.

Its probably true that solid planking is stronger for molding but none that I know of use it on larger boats. All that I see use 6mm occoume and screw the ply layers on through metal fender washers. Many now use NC cut frames and interior parts like engine beds, etc. No one make boats with greater flare than these guys.

Its easy to spot the wooden sport fishermen from other boats because they are really fair, thats FAIR with no FG wobbles or wrinkles. These boats daily take on the roughest water around and make it back in fast if need be, so they have to be strong. Lately the well heeled have taken a liking to the style and are having their "cruising" boats built that way in the same Carolina style. The Hatteras factory is about 25 miles away and they are selling boats too so I gues it keeps our guys working.

 

You can buy plywood in any thickness starting a 1mm, 2mm,3mm,etc up to about an inch. World Panel out of Fla. has a warehouse in Eastern NC.
I have worked in handfull of shops here, in NC. Most of the builders use Okume or Marrani (sorry for the bad spelling) for the sides where flexability is needed and fir on the bottom. I build plank over frame and then add a layer of ply.

Bryan