Wood Choices for Cold Molding

[FastLearner?]

Hello,

I’m new to this forum and want to say hello and thank everyone for a very interesting and informative forum. I am new to boatbuilding (I’ve been thinking and reading about it for years but haven’t done anything about it yet) . I know I have a lot to learn yet but one day I would like to design and build a trailerable planing cabin cruiser for offshore fishing in so. cal. and Mexico waters, similar to a Blackman, Radon or Davis. In the mean time I have been reading a number of books about design, hydrostatics, stability, materials, etc. Anyway, recently I have been focusing on the materials/construction method I will use. I have been leaning toward cold molding, strip planking, or a combination of the two methods.

Here’s my question: what woods are commonly used today for cold molding? Are thin marine plywoods used or are unlaminated (initially) veneers the preferred material? If the latter, where does one find veneers at a reasonable price? I have looked and have been unable to find any reasonably priced veneer thus far. Any help would be appreciated. Thanks in advance.

[frosh]

Hi, first of all cold molding is rarely done now especially on anything bigger than a canoe. I have done a larger outrigger canoe by this method using 2 layers of 1.5mm marine ply and covering with one layer of carbon fabric and one layer of very light fibreglass fabric, all with epoxy.
Having said that I would not recommend it generally for a first project (needs a fair amount of skill and experience), and for any project where you are only building one hull as the mold is quite a lot of work and cost. Also the whole process is very labour intensive hence slow going.
If you want to go cold molding anyway, as strip planking requires a mold also, then use three layers of marine plywood, you decide the thickness depending on many factors. Then you won't need a structural sheething and can get away with a single layer of fibreglass to protect the timber and seal off the joins.
Also if there are any concave sections (eg. in the bow region), cold molding is even more tricky than usual. :)

[FastLearner?]

Thanks for the reply, frosh. I'm surprised by your comment that cold molding is not used much anymore, as I thought I had read somewhere it is a popular method for one-off construction. Anyway, thanks again for the info.

[frosh]

Fastlearner, If you want to use wood for boat construction, then you should decide first whether it will be round bilge or hard chine in shape. For a one off project, hard chine is easiest, cheapest and quickest, using sheet marine plywood.
If you really want round bilge, then maybe sheet plywood for topsides and cedar strip for the bilges. Bottom could possibly be sheet ply as well.
If you have any experience laminating with resin and fibreglass, you might consider using a core material such as divinycell, klegecell etc and fibreglass/ epoxy.
It is well worth buying a plan, and following the designers exact instructions. There are very many traps for beginners, not only with material selection, and construction method, but also getting an efficient and safe hull shape that will work correctly. :)
You will have enough challenge just following instructions and building, let alone designing as well. :cool:

[FastLearner?]

I don't need a rounded bilge but I do want flare in the bow portion of the top sides. For me, designing the boat myself is more than half the fun, so using stock plans isn’t an option. Thanks again for the feedback.

[Toot]

I do a fair amount of custom composite work for cars and I've done a bit for planes, but none for boats. I'm sure I can answer your question to a degree, but first I need to know what the heck you all are talking about.

What you mariners are calling "cold molding"... are you talking about wet layups around a reusable female mold with a foam or wood core in the middle? Or using a sacrificial mold (eg foam that you will later dissolve), or simply a "mold" which will later be included into the structure such as building with a foam core which will be glassed on both sides?

[Tad]

Cold-molding rarely done? Compared to what? I disagree.

In North America and Western Europe cold-molding is generally seen as almost the highest quality building method. Because man hours are high, (fitting and bonding multiple layers of planking to supporting structure) it makes sense to use quality materials, thus creating high quality boats.

Cold-molding generally refers to a hull skin made up of multiple (often diagonally opposing) layers of solid lumber/veneer or plywood, bonded with epoxy. This is usually sheathed outside and sometimes inside with fiberglass or dynel fabric. The combining of strip planking inner and cold-molded outer skins is often done in sailing yachts where the highest loads are longitudinal bending from the rig. All diagonal layers over a longitudinal structure is most popular for powerboat construction. This usually incorporates the engine beds as main longitudinal framing, with bulkheads as transverse members.

A cold-molded structure can be light and stiff as all parts of the boat can be bonded together as structural members.

Usual materials are Western Red Cedar, Atlantic White Cedar, Douglas Fir, and various mahoganies (African and Philippine). These woods all bond really well with epoxy. If you are building a cold-molded boat get a copy of the Gougeon Brothers Book, it's the best reference no matter who you buy epoxy from.

All the best, Tad

[FastLearner?]

Tad, thank you for your reply. In your experience, for cold molding is plywood the most common choice these days, or is veneer still used a lot?

I checked out your Web site and you have pictures of some beautiful boats!!!:!:

[wdnboatbuilder]

Tad has put this subject to rest. very well said. in the boat that you see in my pics is 1/8" ply molded together. had to use to get the curve in the fwd end. light weight..........well maybe in bigger boats but not in small craft (12-21'). but sounds like these would be too small for what your looking for. Alot of your weight is going to be in the stringers not the skin. I can not say enough about the super structure that you have to contend with. the beefier the better for you and your crew. If it were me wood is the only way to go!

[frosh]

Hi FastLearner, I don't mean to discourage you as boatbuilding is a fabulous enterprise, all the more so when constructed in wood BUT---
If you are not about to embark right now on the design and then construction of the dream boat, then fine! You have a lot to learn first. The best way to learn is by reading, researching what others are doing, and then getting some experience by actually doing a project prior to the main one. Mistakes, poor quality due to inexperience and lack of skills are inevitable in the first try. Much better in the lead up project than in the real one!

Tad is talking about very high end (read very expensive, deluxe boats by craftsmen) that are definitely not in a price range attainable by most of us, when saying that large boats are cold molded all the time.
Wdnboatbuilder gives you a false sense of how easy it is by agreeing fully with Tad and also saying that you will be looking for a boat over 21ft, and implying that with due care to structural issues you should have no problems!

My advice is simply, don't jump in too quickly as there is a lot of time and money involved, and without the requisite knowledge and experience it can all be easily wasted.

[Tad]

FL;

Thanks for your kind comments.

Most of the large cold-molded boats currently being built in the eastern US, lots of semi-custom sportfisherman, passenger catamarans, etc. are using plywood. Amateur builders and shops doing speedboats (Van Dam, etc) are using veneer or solid planks.

The plywood covers area quickly, builds thickness quickly, and it's easily available at reasonable price. These guys use it in full sheets where they can, and cut it into wide (12-15") strips and layer it diagonally in areas of high or compound curvature. I'm not a cold-molded plywood fan, because you can't vacuum bag it unless you drill it full of holes. Also half the wood grain is running in the wrong direction and cut in little short pieces. These structural deficiencies are only obvious when you do panel testing of plywood vs solid wood.

Veneer or solid wood cold-molding should be stronger, and properly engineered will be lighter for the same stiffness. People complain that veneers are hard to find currently, true, but they are available. Of course using 1/4" or 3/16" laminations means custom cutting which ups the cost.

Properly engineered cold-molded construction can be light, and will be lighter than solid glass construction. But it won't be lighter than foam cored glass construction. But impact resistance will be much better.

Frosh,

I would always agree that building a dinghy first, then tackling a larger project would be recommended, but it's not absolutely necessary for someone who is methodical. If anyone comes to me and says " I want to design and build a boat", I'll say go to it.

Arld is a retired gentleman living on the south coat of Norway, and he's building a boat. I'm sure he's built something before, (birdhouse, end table?) but never anything the size of a 28' heavy displacement double-ended motoryacht. She's built cold-molded using an inner layer of fore and aft strips on laminated ring frames covered with two diagonal layers of mahogany. He's about 5 years into the project, and just finishing the third layer of planking. I tried to convince him to build a simpler hull form, and I modified this one to take the reverse out of the garboard, but he insisted on building about the toughest, curviest shape imaginable. The workmanship is perfect in every detail. Go Arld!

Tad

[FastLearner?]

Tad – thanks again for sharing the detailed information and your obviously very educated opinions about cold molding. You’ve answered my questions about ply vs. veneer/solid planking. Much appreciated!

Frosh and others – thank you for your feedback as well. Your concern about me getting in too deep is a wise one. I do plan to build a couple of wooden boat projects (non-cold molded) before taking on the roughly 25’ fishing boat project I am just dreaming about now. I am reading a number of books on boat design and building, naval architecture, etc., including one devoted to the cold molding process. I also am reading the Gudgeon Bros book, which is excellent. I appreciate all your comments.

Happy building.

FL

[wdnboatbuilder]

I'm not giving anyone hear any false assumptions on how easy anything in boatbuilding and designing a boat is. All I said is that the Gougeon Brothers Book is a good one and offers a hell of alot of information. If this guy does not pay close attention to the structure his boat ain't worth a **** in any kind of seas. I really don't apperciate you people putting words in my mouth. boatbuilding and design has a hell of alot more to do with than just super structures but where the f--k you going to put all the **** that you want in the boat and how it is going to handle that 7 or 12' wave your going to tske one day. if you feel i gave you a false sence then your stupid........frosh.

[frosh]

Wdnboatbuilder, you are either having problems with the english language or being unjustly abusive, or both. Maybe a couple of courses at night school might help!:mad:

[FastLearner?]

I wanted some info on using ply versus veneer for cold molding. Tad answered my questions. Let's leave it at that. Thanks.

[Toot]

I'm not a cold-molded plywood fan, because you can't vacuum bag it unless you drill it full of holes.


Why is that?

[gonzo]

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.

[frosh]

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

[Toot]

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! :eek:

Thanks for the assistance.

[gonzo]

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

[frosh]

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? :eek:

[Tad]

Why is that?

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

[Tad]

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.

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

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

[Seafarer24]

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.

[cudashark]

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

[chandler]

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 :)

[Tad]

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

[Smartbomb]

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.

[tom28571]

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.

[mulletbucket]

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

[Pericles]

Hello Tom,

The Sculley and Jarrett Bay sites demonstrate your points about coldmoulded Carolina sports fishers very well. They are beautifully shaped and I wonder whether you are toying with the idea of building a smaller version for yourself:?:

I am in the midst of moving house, so that I can start building my very own stitch and glue motor yacht, with the help of my three sons. They are willing to work with me, because they figure I'll live aboard and they can have the house. They aren't wrong actually!

What I am finding intriguing is the way the boat keeps evolving in my mind's eye. I love the look of the Sterling Atlantic 43 flush decker style married to the Devlin Czarinna/Sockeye pilothouse and aftcabin design, but with a monohedron hull form with large flat chines for speed and powered with water jets. I no sooner get the outlines settled, then along comes another idea. Just look at the Vicem Down Easters. Bloody gorgeous!.

One idea concerns erecting the shelter for building. Steel scaffolding poles can be purchased quite reasonably and the supplier I talked to here in the UK is willing to buy them back, when construction is completed. Properly erected, they will support hoists and provide working platforms alongside the hull as it grows. Being a temporary framework means no building permission needed. A wood framed construction would attract the attention of the planners over here. Strange, but true.

The Renn Tolman skiffs are partly built in a cradle, whereas Sam Devlin sometimes uses moulds and builds the hulls upside down. As a monohedron hull form is basically one profile for most of its length, how about draping the wired bottom panels over an A frame of scaffolding to create the basic V shape and attaching the separately formed bow by butt jointing it on with overlapping layers of ply outside and then inside to obtain the desired bottom thickness. This hull bottom is glassed inside and out and the fairing completed. The outer bottom is fully finished before it is set into a strong cradle ready for the hull sides to go up and the bulkheads installed. The basic hull is turned only once and final painting is simplified. OK, it's different, but my first idea was to use a 35 foot length of very thick and tough plastic sewer pipe mounted horizontally as a "horse" and build from that. No hook or hogging then eh?:(

Regards,

Pericles

[Boston]

Im going to go with Tad on this one
as compared to solid wood ply is just not going to turn out as strong a product in this application
the issue of the inner veneer's of the pywood being shorts is a obviously inferior to solid veneer's without this issue

cheers
B

[cudashark]

I absolutly dont agree.

I used 5 layers of 3/16 inch mahogany veneers to build this and it is far stronger than "solid" wood.

Ray

See the build in the gallery section for user name "cudashark"

[Boston]

I think you misunderstand me
I do not consider ply to be solid wood

Im betting you used mahogany in that mahogany build of yours ( nice looking job by the way )
I would consider mahogany veneers to be solid and plywood veneers to be made up of a laminate material
not solid like the mahogany you used

point being that if you rip a sheet of ply you end up with half the inner veneers being of extremely short pieces
certainly a situation to be avoided in a truly quality build like the one you have shown here

I like the idea of mahogany but its mind bending expensive compared to my other choices

[Boston]

hmmm
not sure were my post just disapeared to but basically I suggested we misunderstood one another

I dont consider ply to be a solid wood
mahogany is

a veneer in cold molding can be made up of ply a laminate type wood or solid veneers of wood

my bad if I did not make myself more clear
B

[cudashark]

I think I do misunderstand Boston.

When I think of solid wood I think of a chunck of 4 or 6 quarter solid wood. When I use a ply it is a veneer of many layers glued togeather to make a strong panel.

Ply comes in many pefabricated variaties and grades of quality. I use a lot of solid face frame construction with ply cabinets to build most projects.

Ray

[Boston]

yup
its walking a pretty fine line
in cold molding your making your own full length laminate layers if you use solid wood to begin with
but if you use ply and then slice it to say 4 inch widths
well break open the ply and you will see every other layer is made up of grains going the short way
not a great way to gain the most strength
might as well use solid wood in the veneer's as you did with the mahogany build you presented

nice job to by the way

B

[dskira]

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.

I have to disagree with this statement. Strip planking has nothing to do with cold molding.
I will say it can be a "base" for the cold molding.
But I agree with the second part of the statement about cheaper, while it is time consuming also.
Well thought in advance the cold molding can go pretty fast.
You do not need to laminate on top of strip plank. Just edge glued and fastened is enough. A lot of O-Yolle still sailing after been built in the 1920 with this very classic method.
I don't really understand why the trend is to epoxy everything. No real need if the based is well done.
I built and raced my own IOR made of cold molded (just three layers on space frames and close longitudinal) and just painted for years, nothing ever shown. We used at that time the Aerodux glue and a gun stapler.
Latter on I built several fishing trawler with very thick square section planking in a strip plank fashion, with thick paint in between on the edge and heavily fastened .
Also I built small sailing boat with strip plank, never used epoxy. Still sailing.
But I suppose using epoxy sheathing will make boat lighter and stronger with thinner scantling.
I will not use plywood for cold molded, half of the wood if for nothing, and the boat will end up to heavy. Veneer of thin plank is the only way to go.
And I admit I never used the vacuum system. Must be quite a good way to make sure the gluing pressure is the same everywhere.
As usual, my two cents.
Daniel