Cold moulding - books & thoughts

[nickrj]

Hi all,

I've researched to the ends of the earth when it comes to homebuilding, and cold moulding comes up again and again as the final solution, when factoring the level of skill required, cost, longevity, strength and build speed.

I'd like to move up from my stitch & glue projects to my first cold moulding project - perhaps a sailing dinghy or small power boat. Can some seminal books be recommend for my journey down this path?

I also wanted to ask whether a core material can be used for the diagonal hull sheathing (before glassing) instead of plywood? For example, Nomex or similar. If sustainability is to be considered, are there any 'green' core materials? Or realistically is ply from non-exotic woods the most sustainable solution?

 

[Kayakmarathon]

see https://www.woodenboatstore.com/

 

[jehardiman]

Modern Wooden Yacht Construction: Cold-molding, Joinery, Fitting Out by John Guzzwell .
As for a core, why do you think you would want/need one?

 

[Olav]

Not specifically on cold moulding, but always worth a read and available as a free PDF for some years now:

The Gougeon Brothers on Boat Construction

 

[bajansailor]

I have a copy of this book by Ian Nicholson, and like all of his other books, it is very well written.
https://www.amazon.com/Boatbuilding-Cold-moulded-Strip-Planked-Ian-Nicolson-ebook/dp/B01E9GLRK2

 

[wet feet]

Modern Wooden Yacht Construction: Cold-molding, Joinery, Fitting Out by John Guzzwell .
As for a core, why do you think you would want/need one?

Prior to the Gougeon brothers book it was unusual to find a cold moulded hull with a core,they were made of multiple laminates of structural veneer or plywood.They tended not to be glass sheathed either but I will admit that a good paint job over a well faired glass skin does last a very long time.All of the books listed so far contain good information.

 

[jehardiman]

Prior to the Gougeon brothers book it was unusual to find a cold moulded hull with a core,they were made of multiple laminates of structural veneer or plywood.They tended not to be glass sheathed either but I will admit that a good paint job over a well faired glass skin does last a very long time.All of the books listed so far contain good information.

Actually the Gougeon brothers book (at least my 1985 4th edition copy) does not ever use a core in the hull construction no mater what the method. A cored flat deck yes, but a double curved hull, no. All a core does is increase the Sectional Modulus of the very thin glass or CF skins. It is not needed in the hull of wood based cold molding. It is only used in the deck for stiffness, not strength.

 

[wet feet]

I was referring, perhaps a bit tangentially, to the use of a strip plank foundation to the laminate. The cold moulded hulls which I knew prior to this time had hulls constructed solely of veneer.Things such as the International 14's by Farrar and Soutar or the Flying Dutchmen from Bob Hoare. The larger IOR hulls of the time were similar, but with a few longitudinals of square section to reduce the span that was unsupported. Strip planking simply didn't get a look in in that era. Cores of composite material are something I have yet to see in a wooden hull but I can see merit in the sensible application for those shapes that permit their use.

 

[Rumars]

"Cold molding" is just a general term applied to different construction methods, and comes from the use of room temperature setting glues as opposed to the glues that required heat and pressure (hot molding). While the term is usually associated with epoxy, other glues were common and are occasionally still used.
The actual hull construction methods are full monocoque and semi-monocoque, and the skin construction is a layered affair, monolithic or sandwich. There can be any number of layers, in any orientation sequence, with various thicknesses. Actual manufacturing can use individual veneers, preglued stacks of veneer (plywood), thin boards, thick boards, etc.
The use of cores (both foam and wood) to make sandwich panels is not very widespread, but it has been done, called COVE method by the yard that used it most (Schooner Creek Boat Works). They built very successful boats using foam cores with triple diagonal veneer skins.
The popular "cold molding over strip planking" is not a cored construction, just different thickness layers. It is similar to a monolithic fiberglass skin buildt with different weights of unidirectional fabrics.

To the OP, you can be as "green" as you want, Australia has a great choice of woods to make veneer from, and there are "green" glues.

 

[nickrj]

Thanks everyone - perhaps I didn't describe what I was meaning, or rather, perhaps I am misunderstanding something fundamental in the process. From what I have read and the images I've seen, the premise of 'cold-moulding' involves forming the basis of a hull shape with frames which are then strip planked. From there, a veneer/plywood is criss-crossed over the resulting shape and held together with epoxy. From there, the hull is glassed & faired. My query was essentially whether the veneer part of the build can be replaced with an aramid core material, to reduce weight and increase strength.

In further consideration of this idea, perhaps it is too hybrid of a concept - with all that epoxy and core why not go full composite... Maybe if the goal is to integrate aramid cores for strength etc it is simpler to build in a core bead & cove type fashion using a CNC mould... ?

 

[nickrj]

"Cold molding" is just a general term applied to different construction methods, and comes from the use of room temperature setting glues as opposed to the glues that required heat and pressure (hot molding). While the term is usually associated with epoxy, other glues were common and are occasionally still used.

To the OP, you can be as "green" as you want, Australia has a great choice of woods to make veneer from, and there are "green" glues.

Thank you, very helpful. I think this video of Thierry Dubois building the most beautiful La Louise best illustrates the method I'm interested in. I also like that he's managed to squeegee a hull of that size and avoid the complexity of vacuum bagging:

Regarding timbers, yes, I suppose Hoop Pine is a sustainable option here in Australia when it comes to veneers.

 

[Rumars]

Read the Gougeon book, it's free and will clear up the methods and terminology.

Wooden hulls of all kinds can be engineered to not need any fiberglass, aramid or carbon skins. Often such boats have only very thin cosmetic skins, for worm protection and better looking paint.
What you are describing is "cold molding over strip planking" and yes, the "cold molded" diagonal veneers can be replaced by structural fiberglass/carbon/aramid epoxy laminations. If such a skin exists on both sides, the strip planked wood becomes a core and the result is a sandwich panel.
Similarly, the strip planked portion can be totally eliminated, leaving you with only the laminated veneers, essentially a seamless piece of curved plywood.

First wood on your list should be golden cypress (cupressus macrocarpa).

 

[BlueBell]

cupressus macrocarpa

Introduced to New Zealand in the 1860's.

OP, what length hulls do you want to build?

 

[wet feet]

Thanks everyone - perhaps I didn't describe what I was meaning, or rather, perhaps I am misunderstanding something fundamental in the process. From what I have read and the images I've seen, the premise of 'cold-moulding' involves forming the basis of a hull shape with frames which are then strip planked. From there, a veneer/plywood is criss-crossed over the resulting shape and held together with epoxy. From there, the hull is glassed & faired. My query was essentially whether the veneer part of the build can be replaced with an aramid core material, to reduce weight and increase strength.

In further consideration of this idea, perhaps it is too hybrid of a concept - with all that epoxy and core why not go full composite... Maybe if the goal is to integrate aramid cores for strength etc it is simpler to build in a core bead & cove type fashion using a CNC mould... ?

Prior to the widespread adoption of epoxy,and over here that was the early 1980's,most of our cold moulded hulls were constructed of veneer over a male mould that had longitudinals laid over it at spacings that might be a couple of inches where the curvature was great or six inches where things were flatter.It was common to cover the longitudinals with parcel tape or other plastic sheet to prevent sticking,except where the designer had specified that a stringer was to be incorporated.sometimes these stringers were of greater cross section than the pieces laid to accept the veneer and the moulds had to be relieved accordingly.

The only aramid core I have encountered has been Nomex honeycomb and used correctly it does a wonderful job in composite applications.Many of which are cured using a combination of heat and pressure to allow the formation of good bonds with the film adhesive that it is laid over.I think the boating world probably uses more foam core than it does Nomex as it is a more easily understood substrate for laying further composite skins on top of.

For the CNC moulds that you are proposing,it would be helpful to have a bit of clarification about how much of the structure you would envisage machining.I have no doubt that cutting the transverse moulds and a stem former would be produced more swiftly and more accurately by having them cut by CNC.It saves quite a bit of time and isn't as hard on one's knees if the design can be had in a 3D CAD format.It can also save a good amount of material if the CNC programmer can make use of a nesting function to maximise sheet usage.If ,on the other hand, you mean to create an entire 3D mould by means of a large 5 axis machine,it will be a rather expensive exercise.Both in terms of creating a large block to carve away at and in terms of machine time.Technically,totally feasible and an excellent surface to apply a vacuum bag over.

After reading the books that have been recommended above how about making a small sample piece or two?Something like the lid of the archetypal treasure chest perhaps as you would be able to use it for the lid of a toolbox-or indeed a toybox-and see which methods and materials work best for you.