timelapses movies, those super accelerated clips that are becoming viral on the web, have an hypnotic effect on me , even more if they describe a building process of a hi-tech boat; in the very last days one of these movies has been posted by several FB and Twitter friends; I attach the clip here in low resolution, you can find it in full rez on the FB link down below; this 60 seconds movie describes the building process of a high tech new generation IMOCAs, the 60 footer ocean racers class that we put under the magnifying lens talking about stability and foils in this post; this clip is really interesting because it gives a good idea , although super fast, of how these boats are made ; I’m going to try to slow down the movie, extracting several frames and explaining the main phases of construction, given the fact that few years ago I’ve been professionally involved in a 100 footer cruiser-racer construction using the same technology; the pictures not taken from the clip come from my own archive; for those who are normally involved in “traditional” GRP boat production, forget everything you used to do or take for granted; this is a completely new exciting world, a world of totally clean molds, of really controlled temperatures and humidity in the boatyard, of dust-proof containers where to store Nomex to avoid dust contamination, a world where the weight of every single bolt on the boat is carefully checked, where sandwich panels are tested to destruction before starting the construction, to make sure that they’re strong and stiff as predicted by naval architects ; it’s a fascinating and challenging hi-tech world.
00.00-00.15 : here we can see the “disposable” female molds of hull and deck; these molds will be probably used only for this boat or maybe for other one or two sister boats with lesser modifications, not more than this; so it’s not important that molds are strong and durable as those normally used for production boats;
Hull mold, plywood frames are perfectly aligned using laser level on the tripod the you see in the picture
Hull mold: plywood surfaces are now put in place, fastened to the mold frames and faired
fine, but what’s a female mold ? basically the beach sand molds we used to play with when we were kids, or the biscuits molds are the classical and most knows kind of female molds;
getting back to our big female mold, it’s a very big wooden model made by perfectly aligned plywood frames, plywood surfaces, that will be faired to reach a perfect smooth surface finishing; carbon fibers layers will be pushed in this mold , and hull and deck will be build inside their respective molds ; making these objects it’s not a science fiction hi-tech work, it’s much more a matter of good woodworking craftsmanship, and a matter of huge amount of fairing hours ; there is just one hi-tech trick: since all the molds will be “cooked” several times together with hull and deck, we’ll detail this later, all the stuffs related to them, fairing compounds, paints, and so on, have to withstand temperatures up to 100 celsius degrees without melting ; another small trick: molds have to be air tight , otherwise we’ll have leakages when putting the hull or deck under vacuum
00.19: the writings on the video jokingly say: “molds are covered with glass fiber”; come on guys, don’t joke, in this super tech boat there ‘s not even one pound of old heavy blendy glass fiber, only 100% carbon fibers !
In this case boat is build with so called “prepreg” carbon fibers, mostly “UD” (that’s to say unidirectional fibres, in hi-tech boats jargon), which is yet soaked with resin in the exact proportion, so that we don’t have to soak fibers with liquid resin as it happens in “normal“ building systems; UDs carbon fibers are stored in 40 cm width rolls, kept in a freezing containers (-18° in order to keep the resin inactive) until few hours from their use ; fibers are slightly sticky and they’re covered with a greasy card on one side and with a colored thin plastic film on the other face (the greenish one that you can see in the picture below) , when applying the carbon fibers in the mold we’ll remove the greasy paper and leave the thin plastic film on, until we set up the next layer;
deck mold with first carbon fibers layer
this picture is is taken when deck external skin work is over and the carbon layers have been cooked under vacuum; in this stage works on core elements are beginning ; you can see several high density corecell elements placed on the deck, probably on high load areas like the ones where padeyes, tracks , winches, blocks will be later fitted
00.20: new scene ! We’re watching the hull mold now, the first frame is quite interesting, we see a uniform brown surface; this is a thin PTFE adhesive wrapping (hugely expensive…) that cover the whole mold surface; it will provide a perfect and smooth extraction of the hull from the mold when construction is over (in the standard GRP boat building systems we use less expensive mold wax to achieve the same result)
the whole hull mold surface is covered with a thin PTFE adhesive layer ; in the canting keel area, in the center of the mold, some reinforcements works are taking place; pipes that you can see in the picture are probably vacuum pump piping lines
00.24 : a really interesting sequence ! The blue wrapping that you can see is exactly the thin plastic protective film on the UDs carbon fibers, in this case fibers are oriented at 45° from boat centerline; normally fibers layers in the hull skins are oriented by boat length (0°) or angled (+/- 45°) or transversely (90°) , this array of fibers has the task of withstand the stresses from waves (at 30 or more knots…) and the huge rig, together with reinforcement structures; in over-stressed local areas (rig chainplates, keel box, foils inserting points, water dynamic intakes) extra carbon layers provide extra strength; in the next frame we can see a further carbon layer , this time a “Zero” degrees layer (aligned with boat length) with carbon fibers marked by a different plastic color cover , that means different weight of fibers (in terms of gr/square meter); in this clip a very important operation is omitted, it’s called “de-bulking cycle” : it consists in putting under vacuum the whole hull surface for several hours to press tightly the carbon layers one over each other and all of them on on the mold, and this operation has to be done after each hand laid up layer of prepreg carbon fibers ; in the pictures you can see the huge vacuum bag stored in the mold side, down in the picture (the light blue one) ; so for each carbon layer the whole circus take place: put the mesh, fit the vacuum gauge and the vacuum lines; seal the vacuum bag with sticky tape, put the hull under vacuum, check that the bag doesn’t leak, wait several hours, dismantle the bag and all the other stuffs and go on with the next carbon layer, everything in a 100 square meters hull, not bad at all;
a unidirectional carbon prepreg layer laid down in the so called ” -45° ” direction; you can clearly see the light blue protective plastic film on the carbon fibers (each carbon fiber weight and type has a different protective film color, to avoid mistakes)
a further carbon layer, this is a ” 0° ” layer with different carbon fibers weight from previous light blue one , fibers are oriented as by boat length
00.35 let’s get back to deck mold: in the clip we’re now watching the finished deck being removed from the mold ; several operation have been skipped in the timelapse, let’s take a look at them : in this kind of constructions , both for hull and deck, we start from the outer skin of the sandwich, made approximately by 6-7 carbon fibers layers plus local reinforcements, pressed by debulking cycles like we’ve seen before , then we have to cook everything we put in place;
yes “cooking” literally, because using prepreg fibers means that we have to take all our mould up to about 80°C degrees and leave it at this temperature for a good amount of hours; in order to achieve this result we build both hull and deck in areas that can be enclosed with insulated panels and heated up to our required temperature (we had a 3000 THREE THOUSAND cubic meters volume “oven” for our 100 footer); temperature is raised, kept steady and lowered via a computer operated system, and an array of thermometers keeps the parameters under control in several points of the hull, during the whole operation; parameters like the heating and cooling ramps are given by resin and carbon fibers supplier ; when the temperature rises the resin within the prepreg carbon fibers became liquid , flows within the carbon layers, the excess of it is squeezed by the pressure made by vacuum (the whole cooking operation is made under vacuum), when the hull cools down the resin became solid , always under vacuum pressure; the result of this complex process is a monolithic piece with super-compact carbon fibers kept together by the optimum quantity of resin , not one pound more than required, in this way we produce a hull really light and with astonishing stiffness and mechanical properties ; after the external skin cooking cycle and cooling down, we’ll set up the core of the sandwich; in this kind of boats we normally use Nomex ( a kevalr honeycomb, see picture) or Corecell (a high performances tough foam, chemically is a Styrene Acrilo Nithril foam); these too have to be glued and “cooked” under vacuum pressure on the carbon skin; now we’ll close the sandwich with the internal skin and further local reinforcements, so another cycle of carbon layers, debulking under vacuum, and a final cooking process under vacuum, all these operations both for hull, deck, and all the internal reinforcement elements
Nomex (on the left, it’s a kevlar honeycomb , a stuff that has to be handled very carefully, especially during the process of gluing it on carbon skins) and Corecell ( the yellow foam on th right, chemically speaking it’s a Stiyene Acril Nitryl foam) ; this are the materials used for sandwich panels core , used in hull, deck, and internal structures in this kind of boats; a Nomex or Corecell cored sandwich panel featuring thin carbon fibers skins, is extremely light, strong and stiff
this is one of the “king size tables” where bulkhead and internal structures are made; these parts too are made in carbon-Nomex sandwich, vacuum bagged and cooked at 80 degrees, just like hull and deck .
00.35 the deck is raised out of the mold, rotated and set on temporary scaffolds, now fittings and deck gear can be fitted on board, in a situation where we can easily reach every portion of the deck, more comfortably than after joining hull and deck together; deck is then painted white
deck is out of its mold, rotated, painted in white, and placed on temporary scaffolds; we can start to fit the deck gear
00:40 the deck is placed on the hull and joined ; in the meanwhile all the internal structures, (bulkheads, stringers, floors,beams) have been laminated in the hull (see the movie frame) ; all these parts have been made with the same process and materials (sandwich, external skin, Nomex core, internal skin, cooked and under vacuum) in big sized tables dedicated to their production, tables in which we can operate with vacuum pumps and cook the parts with dedicated heated removable top covers , even in this case everything is kept under control by a computer operated array of thermometer ; in order to keep construction times as tight as possible, hull deck and internal structures are produced together ; so these operation like laminate carbon layers, put parts under vacuum, cook them , and so on, are repeated hundreds of times, and every single part and every single process must be done with maximum care to each detail, there are no “secondary importance” parts in these boats; it’s a work that I like to call a “high-tech craftsmanship work” where manual abilities and experience of each single operator goes together with a top level use of technological devices
deck is placed above the hull, where all the internal stiffening structures are now in place, glued and laminated with hand laid up carbon fibres, resin and high strength bonding compounds : a work made with high precision, skill and great attention
00.45- end : structural works are mostly over, it’s time to fit deck gears, systems and the supercomplex navigation electronic system and autopilots, which is fundamental in the “sailing astroships” ; then the hull hull is wrapped with adhesive plastic film with sponsor graphics (this solutions is by far easier and more practical than traditional paintings) ; the boat is read y to fitted with keel and rig, and launched for the sea-trials
the HUGE hull of a 100 footer cruiser racer: work on the hull skins and core is over but launch is still long months far away
few more words: in this 60 seconds clips are squeezed THIRTY THOUSAND working hours of a about twenty people or more team ; I hope that with these notes I have been able to take you in the boatyard with them to understand how much care, commitment and skills there is behind the boat that you’ll see sailing in the picture below.