cold molded hulls

[Jonathan Chouinard]

Hi everyone, I have been thinking about starting my tiki for the past year now, but I'm not quite to the point where I have a suitable building space.  During this transition, I've had ample time to contemplate the building method that these Tiki's take to build. 

     In thinking about this build, it has occurred to me that this boat appears to contradict Mr. Wharram's whole philosophy, specifically being one with nature and such.  Occume marine plywood is made from a tropical hardwood that isn't particularly sustainably harvested, and isn't known for its rot resistance.  Epoxy is very toxic and is well documented for causing welts and allergic reactions.

     This train of thought has led me to contemplating other methods of building these hulls.  Has anybody successfully produced a hull using the cold molding technique?  I was thinking that by starting with thin strips of cedar, followed by veneer of something, then foam or corecell type material,  followed by a thin layer of fiberglass, kevlar, carbon etc it would produce a very lightweight but strong hull.  My main concern is that Wharram's plans aren't good enough to do an accurate job of making station molds.  Has anyone made a CAD drawing of a tiki design?  

    I'm hoping somebody can shed some light on the subject.  My inspiration for this line of reasoning is the Susan schooner thread on the woodenboat.com forum.  The guy built a beautiful yacht from locally grown timber, Lowes lumber, etc.  I like the idea of using local stuff, a little bit at a time, and not shipping plywood from africa, asia, south america etc.    

[Jonathan Chouinard]

That is very interesting, I would love to hear your research about using bamboo!

robin craig jones said:

Hi Jonathan

 

I am also looking into building a Wharram or similar traditional voyaging catamaran using the cold molding technique and bamboo double diagonal strip planking with a lattitudinal planking over the double diagonal. There are industrial PVA glues available that would build a very strong hull whos tripple planking alone would give sufficient structural integrity. A bamboo pole if dried straight can be split in 8 pieces simply and once fed through a thicknesser you are left with planking with a 45 degree angle on each side. You can butt these together by turning one plank one way and the next the other. Although this hasn´t been used in boat construction as far as I am aware, there are people using this technique to build planes and race bikes with a higher rigidity and strength to weight ratio than carbon and kevlar. I share your thoughts on the poisonous nature and contradiction with Wharrams philosophy, he himself said he hopes one day bamboo could replace these technologies. Although it doesn´t grow in england it could be a sustainable healthy answer to your problems. I am soon going to be in touch with some one who has very successfully used these techniques for other projects and would be happy to share what types of glue to use etc. 

Hope this helps or at least lets you know your not the only one thinking along these lines.

I would definitely appreciate feedback from anyone else concerning this idea

[Geminidawn]

That sounds very interesting! Bamboo is basically a tall grass and very fast growing and a nuisance in some places, utilising it a lot more in the boat building world may save many thousands of precious old hardwoods. Your biggest expense would be the glue, for strip planking or double diagonal you'll need a lot of it. However I don't think PVA industrial or not has what it takes in a marine environment. Personally I never use the stuff, even for interior joinery.

Have you ever tried "Double Diagonal" or "Strip Plank"? Strip Plank is ok and a practice I use often. Double Diagonal on the other hand is unbelievably time consuming. If you wish to experiment with it try it out on a small canoe for a taster before you disembark on anything major.

Great use for Bamboo though! Looking forward to hearing more about this!

robin craig jones said:

Hi Jonathan

 

I am also looking into building a Wharram or similar traditional voyaging catamaran using the cold molding technique and bamboo double diagonal strip planking with a lattitudinal planking over the double diagonal. There are industrial PVA glues available that would build a very strong hull whos tripple planking alone would give sufficient structural integrity. A bamboo pole if dried straight can be split in 8 pieces simply and once fed through a thicknesser you are left with planking with a 45 degree angle on each side. You can butt these together by turning one plank one way and the next the other. Although this hasn´t been used in boat construction as far as I am aware, there are people using this technique to build planes and race bikes with a higher rigidity and strength to weight ratio than carbon and kevlar. I share your thoughts on the poisonous nature and contradiction with Wharrams philosophy, he himself said he hopes one day bamboo could replace these technologies. Although it doesn´t grow in england it could be a sustainable healthy answer to your problems. I am soon going to be in touch with some one who has very successfully used these techniques for other projects and would be happy to share what types of glue to use etc. 

Hope this helps or at least lets you know your not the only one thinking along these lines.

I would definitely appreciate feedback from anyone else concerning this idea

[Ann and Neville Clement]

Life is short.  If you follow the plans you will finish sooner and get out there sailing sooner too.  If you plan ahead when you work, you will not waste hardly any epoxy because you will have a little list of places where you need a bit more filleting and you can put it there.  We are about to build a small sailing dinghy and will be looking for some fir ply to build with.  Perhaps someone will suggest a good source where we intend to build which is in Providence, Rhode Island over the summer.  Peace IV was built with okume and it is expensive and a tropical wood so we did feel concerned about that, but with all the care we used in building, we expect Peace IV to be in service for a very long time.  Ann and Nev

[George Ray]

 

Seems to be lots of room for innovative development along these lines.

What does the the Wharram design group have to say about such things.  Maybe it would be too hard for them to stretch and change when they have a formula that works. Change is difficult especially when one has built a comfortable and well respected and worn smooth wonderful rut in this life. But maybe this is the great idea that will set their design and eco passion on fire and it was only waiting for the spark of this thread.

What would/have some of the other great multihull minds like, Jim Brown or Chris White or ???? .. say/said on this interesting topic?

 

 

Cylinder Molding construction:

http://www.multihulldesigns.com/pdf/cm33.pdf

 

Constant Camber:

http://www.smalltrimarandesign.com/Trimaran-Articles/Construction-M...

 

[Ann and Neville Clement]

Always the best idea is to stick with the plans.  Ann and Nev

[Jamez]

hi Jonathan, if you haven't already, you might like to check out the Gougeon boatbuilding book for a run down of different construction techniques.

DD/resourcinol  used to be a very common method for round bilge hulls (mono and multi) more recently largely supplanted by ceder-strip and foam. Pic of DD GBE hull attached. It is pretty hard to beat ply for lightness under say 8 metres LOA, without going to considerably greater expense. 

Just my 2c, but probably best to build to the plans or find another design that suits your requirements/preferred build technique better.

 

Jonathan Chouinard said:

wow excellent response, thank you.  I didn't realize that cold molding needed so much bracing, I thought that was a benefit of it.  I would love to build my boat in cedar strip, but like you said it would probably take forever to finish it!

[Bob Bois]

Ann and Neville Clement said:

Life is short.  If you follow the plans you will finish sooner and get out there sailing sooner too.  If you plan ahead when you work, you will not waste hardly any epoxy because you will have a little list of places where you need a bit more filleting and you can put it there.  We are about to build a small sailing dinghy and will be looking for some fir ply to build with.  Perhaps someone will suggest a good source where we intend to build which is in Providence, Rhode Island over the summer.  Peace IV was built with okume and it is expensive and a tropical wood so we did feel concerned about that, but with all the care we used in building, we expect Peace IV to be in service for a very long time.  Ann and Nev

 

Ann and Nev, Downes and Reader can get good Doug Fir marine ply. Also, check out Atlantic Distributors.  Take care, Bob

[robin craig jones]

Hi Geminidawn

 

I agree about the PVA but the glue theyve been using isnt a traditional pva and I am yet to hear back about what it is exactly, but it works in the same way and gives a very strong bond. As far as I can see any building technique that isnt properly protected from the marine environment eventually fails, wether it be delamination, rot or rust. I haven't had experience using the double diagonal or strip plank techniques but am willing to spend the time nesecary. At the moment I am still in the stage of researching and figuring things like not being able to use traditional fastenings like screws etc. for fear of splitting the bamboo. I will definitely experiment on something small in the mean time. Áll this aside though I think it is a very promising avenue to follow and besides the cost of glue virtually free as far as materials are concerned especially in places where bamboo grows. Every part of the boat could be constructed with these techniques, from cross beams to spars. You could even make sheets of bamboo ply with a simple press for parts of the build that required it. I have built other structures like yurts and bridges using lashings and bamboo poles with great results so am pretty excited about taking it a step further and creating laminated structures. It seems like the perfect mix of traditional materials and technology.

Anyway thanks for your feedback I was a bit hesitant to post these ideas as everyone has there own techniques that work well and the tried and true normally is because it works. Still the prospect of a cheap strong building technique is a very tempting one worth the time and effort of having to figure it out and use bits and pieces of what works already.

 

Cheers Robin

Cheers Robin  

Geminidawn said:

That sounds very interesting! Bamboo is basically a tall grass and very fast growing and a nuisance in some places, utilising it a lot more in the boat building world may save many thousands of precious old hardwoods. Your biggest expense would be the glue, for strip planking or double diagonal you'll need a lot of it. However I don't think PVA industrial or not has what it takes in a marine environment. Personally I never use the stuff, even for interior joinery.

Have you ever tried "Double Diagonal" or "Strip Plank"? Strip Plank is ok and a practice I use often. Double Diagonal on the other hand is unbelievably time consuming. If you wish to experiment with it try it out on a small canoe for a taster before you disembark on anything major.

Great use for Bamboo though! Looking forward to hearing more about this!

robin craig jones said:

Hi Jonathan

 

I am also looking into building a Wharram or similar traditional voyaging catamaran using the cold molding technique and bamboo double diagonal strip planking with a lattitudinal planking over the double diagonal. There are industrial PVA glues available that would build a very strong hull whos tripple planking alone would give sufficient structural integrity. A bamboo pole if dried straight can be split in 8 pieces simply and once fed through a thicknesser you are left with planking with a 45 degree angle on each side. You can butt these together by turning one plank one way and the next the other. Although this hasn´t been used in boat construction as far as I am aware, there are people using this technique to build planes and race bikes with a higher rigidity and strength to weight ratio than carbon and kevlar. I share your thoughts on the poisonous nature and contradiction with Wharrams philosophy, he himself said he hopes one day bamboo could replace these technologies. Although it doesn´t grow in england it could be a sustainable healthy answer to your problems. I am soon going to be in touch with some one who has very successfully used these techniques for other projects and would be happy to share what types of glue to use etc. 

Hope this helps or at least lets you know your not the only one thinking along these lines.

I would definitely appreciate feedback from anyone else concerning this idea

[Brian Paton]

Hi Jonathan

I was wondering about building a cheap single hull out of inferior and cheaper wood, then take a mould and the use the resin infusion process to make the two hulls for the real boat.  This way you could have a very strong and light hull with a foam core.  It would come down to cost but the time to infuse the two hulls could be done in under a month. The only time consuming bit would be the initial plug, but you could employ some part time help to get the perfect hull form.  You could do the deck the same and eliminate wood in the hulls altogether.  I also think doing it this way would give a much superior product.  No rot, stronger, lighter, higher resale.  Like someone else said here these designs are old and with new techniques and products that are on the market there is no reason why these boats can't be built to modern standards.  Except cost.

 

Brian 

Jonathan Chouinard said:

I think that both the process and the product are important.  Wharram's newest designs are over 20 years old by now, and there have been vast improvements in materials and processes.  I like the look of wharram's designs, which is why I am interested in building one of his boats, but I'm just contemplating on efficiency in building.  Of course ply and epoxy works fine, but I'm sure there are materials out there that are lighter, stronger and quicker to build with.  I'm curious what those materials are.  I would think that building in fiberglass/foam sandwich would make for a strong, light build.  It would be interesting to see some data on this.

Chuck Valley said:

Is it the process or the product that's important?

 

Chuck

[Omar M. Rashash]

The techniques proposed by JWD for the construction of their designs are, for the most part, the most appropriate considering the size of the boats and the skill level of the builders.  While other materials/methods are available to the amateur builder, they increase cost, increase the required skill level, and introduce additional risk into the construction process.  The Wharram hull can be easily constructed from tortured plywood and doesn't require the ability of the cold-molded to form a complex curve.  You would be hard pressed (no pun intended) to be able to construct a hull of layered or strips of wood, that has the same strength to weight ratios as factory manufactured marine grade plywood.

 

If you are 100% confident in your construction abilitilies, and truly believe that epoxy will stop all water penetration, then the selection of material for the hull doesn't matter.  You don't need marine grade plywood and PVA glues will work just fine.  If you choose GRP as a construction method you'll quickly see why it is usually left to professionals.  In GRP, the fiberglass/epoxy is the only element in the composite that is structural, the foam/balsa core is merely a spacer.  Any defects in the layers of glass will translate into structural deficiencies in the completed hull.  If you think it is difficult getting a single layer of 6 oz. glass to lay down on a sheet of plywood, imagine what multiple layers of glass over foam would be like.

 

Something like 80-85% of the cost of bulding a boat is labor.  Considering what the overall construction cost will be, trying to save money on materials, particularly by substituting inferior materials, is not cost effective.

 

We, as a society, tend to substitute technology for skill.  While it may make sense in some circumstances, table saw over a handsaw, power sanding over hand scraping; we should try to keep things in context.  These are small, one-of boats, built by amateurs using available materials in locations and conditions that are not necessarily ideal for boatbuilding.  Cold-molding is attractive to the boatbuilding industry because complex shapes may be constructed, extremely strong hulls built (for their weight), with a minimum of skilled labor.  The artistry represented by highly skilled boatbuilders constructing a carvel planked hull is replaced by lower skilled workers more adept at epoxy and sanding.  Building a cold molded hull is more labor intensive than carvel planking, but the workers will earn 1/2 the hourly rate paid to the boatwright.

 

HTH,

 

Omar

[Tom]

Given the rising prices of raw materials and the decreasing prices of used boats, perhaps you would be better off restoring a fine vessel from the days of yore?

 

Not giving you shit at all...just check out the market!  Restoring an older wood monohull, perhaps an old fishing schooner, is now cheaper and faster than building a new boat!  Just please please please don't replace oak with pine.

 

Anyway, it might be worth checking out.  There are some great deals out there right now!