The Latest "Skinny" on Cold-Moulding
I overheard a conversation the other day where it was claimed that, after 25 years of cold-moulding popularity, it is finally becoming apparent that epoxied wood laminates are NOT holding up to the constant motion stresses and fatigues of blue-water sailing.
Is that true?
Can anyone with lengthy cold-moulding experience verify or contradict this rumor?
On a side note, is anyone experienced making their own veneers from lumber?
I have lots of western red cedar, but my table saw can only slice thin veneers at a maximum width of 3 1/2 inches, but the Goudeons recommend veneer widths closer to 6 inches.
So I was wondering, if I buy an old band-saw, could I cut 1/8 inch veneers accurately and even from 6 inch widths?
This reply could go on forever concerning cold mould hulls. The key to cold mould building is that the boat is properly engineered. But heck along the coastal regions of midlatlantic, strip plank construction and carvel planked hulls, after 25 years if not properly maintained, go bad. We need more information on what boat you are intending to build.
There have been many high end hulls all built out of solid veneers. Rybovich in Palm Beach used mahogany for double diagonal planking as did Huckins Yachts did for their PT boats long before epoxy was used in a production setting. The key is stable woods. Band saws with a resaw style blade is used for slicing veneers but needs some setup in the beginning with a supplement guide block. So use a short piece for cutting samples, as with most bandsaws, they require some tuning. Unless this is done, blades have a tendancy to not run completely straight when running wood what appears to be a straight line to the blade setting at rest.
I hope thats not too confusing. Western red cedar is pretty stable as long as its dried for your job. But needs to be reswan and sanded uniform thickness in a drum sander, if you have access or you can also use a planer. In both cases, depending on your two pieces of equipement, uniform veneers require a backing board to make smaller veneers rigid enough for uniform thickness. Uniform thickness is important for a fair hull. Shape of the hull actually dictates how wide the veneers that you use should also end up. In some of the bow sections, or in vee bottom entrys, smaller in width will be required anyway. Plywoods are just easy to aquire, especiallly in your area. But buy good stuff. Your hull comes out better and its less work in fairing for a better finish job. What type of boat building experience do you have?
Thanks for that reply Oyster, that was great.
It's not confussing, and it would make perfect sense if I could visualize it.
I just don't have a visual picture of either the supplementary-guide-block for the band-sawing, or the backing-board for the planning.
The cheapest, most spartan, blue-water, pocket-cruiser possible.
No, actually, the best equiped, strongest built, and most luxurious, blue-water, pocket-cruiser that I can afford.
In my case, however, they both describe the same boat.
So I'm looking for a 27' to 30' ocean-going, monohull design, well balanced with an easy sea-motion, that can be built with the materials I have on hand.
Which is lots of seasoned oak 4"x4"s and lots of uncut western red ceader timber.
I have a large diesel lincoln welder, but the cost of pre-primed boat-building steel around here is $1- a pound, so steel is out.
Even marine 1088 plywood is out.
Maybe, with epoxy at $60 and up a gallon, I shouldn't be looking at cold-moulding nor strip-planking either.
Plank on Frame may be the only option I can afford. Funny, because I hear that in some places wood is the most expensive option.
Moreover, I'm seriously considering a home-built Junk-rig.
My skills are carpentry and cabinet-making.
With wood as my material, I'm searching for the right design as I prepare a boat-shed.
I like the lines and reputation of the Bristol Channel Pilot Cutter 27 or is it 28.
I would really like to find an equally seaworthy design that was non-proprietary share-ware off the inter-net.
Know of any?
Do you think I should still consider cold-moulding as an option for my project?
The Gudeon's say one pound of epoxy for every 20sqft of surface for laminating cold-moulded veneers.
So, if we're talking say, 450sqft for hull and deck, and how many 1/8" veneers(?) 6(?) for a total of what, 2700sqft, divided by 20spft per pound, gives us 135 pound of epoxy.
But how many pounds of epoxy is in a gallon?
By the gallon, it's $85 each around here.
Over the net, I see some discount epoxies in larger quantities for cheaper.
If I could get my epoxy for less than $1200, I might consider cold-moulding.
What do you think?
You need to look at George Buehler's designs. He designs them you folks just like you. His boatbuilding book contains several sets of his plans and is worth the cost of the book alone (around 25 bucks). Check out his web site > www.georgebuehler.com <
There are many designs that fit your bill of fare. Stroll right on over to this site for a while. Next your concern of the costs must be removed, like thrown out the window. You are entering the rediculous zone of throwing away money from any rational point of view. This is about your mental stability, the lure of the sea, the mental excercize of the mind body and spirit working hand in hand here.
The first thing you must do is to plan your project and double your figures. At that time if you feel its too much, then don't start it. Take your money and buy used in the beginning. In almost all cases its cheaper over the long haul if this is your first project and money is of concern. Forget about price per gallon for the epoxy resins. In bulk its not that bad. Doing cold mould requires a lot. But long term, sometimes its actually cheaper.
I once asked Bruce King why he chose to design boats with cold molding. His response was: if you build a 10 million dollar yacht and 7 million of it is in the interior fittings, you want to make your very best effort to make sure the hull that carries it all will last as long as possible. He felt that that was to be found in a well excecuted cold molded hull. If done well, you would have a hard time showing me anything else that would outlast it.
I appreciate all the imput.
The more I read about cold-moulding the more I warm to the idea.
I have lots of western red cedar, and as far as boat-building is concerned, the recommendations I've been receiving indicates cold-moulding is the best use for that wood.
A molded hull isn't the build I'd recommend to the first time or beginning builder. There's a lot of building necessary before you actually get around to piecing together a boat. It's also not the easiest method to repair, when the need arises. Strip planking is a common use of red western with much of the same benefits as molded and a lot easier for the amateur to get a handle on. Ashcroft or double planking would be a slightly better choice, if the hull could tolerate the method and thicker planks can be employed.
Set-up work is unavoidable, so my choice will be based on the design I choose, and strip-plank, even if only as a core, may be called for.
Have you, or anyone else here, had experience with Double-Planking?
What's the best advantage you've found with Double-Planking?
I personally have never repaired one. But there are several hulls that have used strip plank for bulking up, and then skinning veneer diagonal and then skinned over with glass. This is my prefered method of building if I wanted to do something by myself and with ease.
This is a wonderfull site for glued lapstrake hull. It can be built with several methods. Be very carefull when you visit this site.
Here is just one example of strip planked and veneer. I have several more but will await to here from you after digesting this.
Double plank or what was formerly known as the Ashcroft method is a type of molded construction. Both layers go on at an angle similar to what Oyster shows in the last photo. The angle is usually determined by what direction the planking material will "flow" around the mold without puckering. This generally works out to be about 15 to 30 degrees. Double planking has the planking flowing in the same direction and the inner layer's seams are covered by the outer layer. Both layers can be placed on the mold at the same time. It can be used with solid wood or plywood as the planking material.
I've seen and repaired double and triple diagonal and was on a large boat that was quadrupial diagonal with 1/2" stock. Repairs on all molded boats isn't the easiest construction method to fix. I'd rank it one of the hardest. You can't just cut out the bad section and fit a new piece in.
Double planking can be taken to the next logical step. That is to alternate the layer angles (double diagonal, triple, etc.), the first can lean forward, the next aft, which will produce a stronger hull. This is typically how a molded hull is done, though most cold molded hulls use quite thin veneer stock in several layers, unlike older molded hulls, which may have half as many layers of twice the thickness per layer. This also means that each layer has to be complete (or very near so) before the next can go down, slowing the planking operations.
A well engineered, molded hull can be one of the lightest wooden hull methods. If the outer planks are set fore and aft, it has a look of carvel with none of the leaking. Stripped hulls often have a molded outer layer or three (and inner, but not always), to prevent "print through" of the strip seams, which can happen as the boat ages. This technique can be taken advantage further by using a light, stripped core of say spruce, that could be skinned both sides with mahogany, for example. It makes a light, strong "sandwich" structure. The same principles are used in composite, cored structures.
The biggest advantage I've found with double planked methods is the speed you have in skinning the hull. Once your done, there are no more layers to apply. A molded hull can have many layers to apply, before the hull is finished.
The methods that don't require a lot of goo to complete are what I've found the fastest and cheapest to construct. Epoxy, as you've learned, can dramatically increase the costs of a project. It also is messy, can be difficult for the amateur, is toxic, causes nasty reactions to some folks just being near the stuff, requires more prep (usually to keep it off things you don't want goo on) then more conventional fastening methods. A 15' skiff can double in materials price, just with the use of epoxy dependant building methods. Wooden construction, involving epoxy methods, being done correctly for longest life, should be embalmed in goo. This means every piece, every side, hole, notch, weep hole, everything, needs to be coated with epoxy. That's a lot of exposure to the stuff, if you're the sensitive type. I'm lucky and have minimal sensitivity to the stuff, but many aren't as lucky and literally can't be around it without some sort of reaction.
On the other side of the epoxy coin, it is a wonderful adhesive and wood treatment. The proper use of penetrating and laminating epoxy can make surprisingly strong, water tight structures, that are long lived and very durable. It doesn't need the high clamping pressures some other adhesives do, it's gap filling and can serve as a structural element itself. It's invention has born out whole new methods of boat construction, that would be hard pressed to be successful using another adhesive.
In the end, the design selection process and it's construction method options available to that boat, will be a very personal decision. This decision will need be based on your experience, skills, tools, work environment, materials availability and other variables, only an honest assessment from you can answer. Read up on the different methods, on the designs you're interested in and try not to buy into the material advertising hype or well written study plans text. For the back yard builder, it's never as easy as it sounds in the book or on the label and will take twice as long, cost twice as much, use up twice as much stuff and cause your wife to cuss at you twice as hard for spending so much time (and money) on it. Good Luck . . .
This is another 32 foot hull built with strips and skinned with the diagonal veneers. This boat has been built by one individual by himself. You can bulk the hull with thicker components as they are easier to handle and encapsulate the hull with glass, which incorporates the two unlike parts for structual integrity and stabilizes the wood. SOme of these builds causes a lot of controversy with some of the purists. So beware and weigh all replies with that in mind. Remember plywoods have many layers all sealed with problems stemming from water that is introduced into the inner layers even if the plywood has never been glassed. Nothing is fool proof in boats. Proper maintainance and care for details when mounting parts with beddings and sealing of hardwarde is very important in these methods.
Thank you Par and Oyster for your informative replies.
Par, when I think moulded, I think glued.
But, are you saying that with Double-Planking you plank with metal fasteners rather than with epoxy?
And, if you don't use epoxy, are the planks able to freely swell and contract without stressing the next inner or outer layer of connected planking?
And are you saying that with Double-Planking you plank on to a male-mold rather than on to a set of bent frames?
Oyster, I really like that 6 1/2 ton, shallow draft, Murray G. Peterson design.
I'm leaning towards a shallower draft design.
Except, I suppose with a shallow draft Monohull, one needs a lot of expensive lead ballast to achieve self-righting ability.
Still, If the patterns and off-sets for this design were CHEAP enough, I'd be very tempted by the cutter option of this design, even though I might want to convert it into a single mast junk rig.
Also Oyster, I really like how the first photo of the 32 footer illustrates how the frames were constructed.
Remarkably, the frames appear to be about 36 inches on center, and yet they still produce a fair shape in the strip-planking.
Once strip-planked, are the frames then removed, and the interior of the hull fiber-glassed, or do they remain in the finnished hull?
Also, I went to the 'glued lapstrake flickr' link, but, because of your warning, I didn't explore beyond their home-page which didn't explain how they cut and glued the lapstrakes together.
Still their photos were good.
My warning was a bit tongue in cheek. That fellow has done one of the most first class jobs on that boat. I am truely a fan of lapstrake. I guess I should have posted a gemlin with the post. The laminated frames stay in the boat. But they are smaller than a normal planked hull with that type of construction.
There are also some wonderfull sharpie designs, shallow draft and centerboard designs out there. There are also some designs with a modified draft incourporating leaded keel and centerboard design.
A far as spacing, the thicker the planking the wider the spacing.
The original double planked hulls (Ashcroft method) used a few different things between the layers, but they didn't have water proof glues so, tar, varnish and lead were the common materials used. In the modern versions of this method, glue is used. I have a 1956 double planked powerboat which was done with resorcinol, but I suspect it could be done with any type I adhesive and of course epoxy.
The planks are laid over a male mold or plug, built of marginal materials if a one off. Usually cheap ply station molds and furring strips is all that are necessary for a mold. The mold can or may not incorporate a keel, stem, bulkheads, etc., but most do have some finial structure in them. The first few planks are placed on the mold at the angle that works best and stapled or tacked down. Next the outer layer goes over top of the first, covering the seam of the inner layer. The temporary fasteners are pulled as the outer planking goes down. This overly simplified process continues until she's planked up. It's a common planking method for vacuumed bagging techniques, but it can be done by hand with fasteners too. The method has been around since the middle 1800's as far as I know, maybe it's much older a construction type.
This method eliminates much of the need for a internal frame work or structure (frames, floors, stringers, etc.), just like any other molded method. I've used plastic staples and metal ones through a piece of plastic banding strap (makes it easy to pull them out). Once the glue sets, you don't need the fasteners.
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