April-May 2013 filling and sanding the hulls.
After insulating our shed we made ourselves a large, flat work table.
This 3m x 4m table is large enough to clad three or four foam panels with fibre-glass at a time.
We will eventually cut components such as frames and internal doors from these large vacuum infused panels.
Filling the Seams with Epoxy and Microballoons.
In March, we started heating our newly insulated shed with electric heaters. It is not only more comfortable to work in, but also necessary for working with a Epoxy and Microballoon mix. The hull has to be made air tight before cladding with fibre-glass using vacuum infusion. CoreCell is inherently air tight, but not the seams, these have to be filled and sanded first.
Jolanda spent a good half an hour sawing up off-cuts of MDF into mixing sticks. We had already accumulated a stockpile of old yoghurt and sauce pots for mixing up the epoxy, we had cut up the lids to make nice, flexible scrapers that are perfect for getting deep down into the seams. Once mixed, the epoxy is only good for approximately half an hour, so to avoid wastage, we made lots of small batches.
In the next two to three years we expect to use hundreds of plastic pots (see below). If you have any laying around, they will always be welcome here. You can take the opportunity to nose-around our project as well.
To make the epoxy/microballoon mix, first mix the epoxy and hardener, a little bit of Aerosil will improve its gluing properties. Then add in the microballoons. Microballoons keep the paste light whilst adding volume. The final mix resembles a large pot of Chocolate Paste.
This film shows how we made it. According to the Microballoon instructions, the red powder is better for sanding than the white, so we took the manufacturers advice and didn’t do any tests first.
Just like using any other kind of filler, there is always a risk of getting air bubbles in the seam. Air bubbles can provide a path for false air when a vacuum is being generated, so to prevent this, we filled in three layers.
To fill the seams, push the first layer deep into the seam, remove any over-spill on the panels straight away. Apply the second layer within twenty-four hours, but do not fill the seam completely, once again, remove over-spill from the panels immediately. The final layer should be applied royally, once hardened, the excess can be sanded down using an orbital sander and will leave a perfectly smooth finish.
Bringing on the following layer within twenty-four hours of the previous one means it will have a good surface to bond to without having to key the previous layer first. We planned our work in such a way that we were able to fill for three days in a row without having to sand or rub-down.
We are glad we initially only installed the slats on the outside of the mould leaving the inside free accessible. We have full access to the surface of the hull without damaging the foam.
The Inner Hull walls
Once the outer walls of the hulls were foamed, filled and sanded, we were able to start on the inner walls.
The chamfer panel forms a 45 degree joint between the hull and the bridge deck. The chamfer panel has a complex shape, so we allowed for this by leaving material protruding out. This excess will be removed at a later date once the chamfer has been shaped properly.
Working in the bow area was not easy, there is a limited amount of space to work in and the panels have to bend in two directions. To make shaping easier we used 20cm panels instead of the 40cm used on the rest of the hull. To prevent damage to the foam when walking back and forth to the work area, we removed our shoes and worked in socks only.
The stern extends 20cm past the last frame. So to ensure the slats were aligned properly we made and fitted a temporary tail-board, then fitted supports to secure them in place. These supports are fixed to the ground. Once happy with the shape, we were able to continue with filling and sanding.
Preparing the 10.5m long chamfer panels made a nice change. We temporarily fixed the panels edge to edge and marked the joint. These reference marks will come in handy later when we lay the panel into the mould. To aid shaping of the chamfer panel, Paul divided the template drawing into 1m sections and printed them out on the plotter at a scale of 1:1, joined them up and laid them on top of the panels. He was then able to quickly and accurately transfer the shape to the panel. A piece of cake!
Next weeks we're busy with sanding and filling seems and finishing touch of the hulls.
Material for the frames and vacuum infusion have already been ordered. It looks like we will be able to lay-up the first glass-fibre mats in the last week of June. We will use these frames as tests to perfect vacuum infusion before moving onto the hulls.
January 2013 (and February/March)- Brrr we had a long cold winter.
We took a week off following the New Year celebrations, and therefore have some catching up to do.
Battens and Frames
As you might already have read in the ‘Building Method’ section, after positioning the frames, the longitudinal wooden battens then have to be fitted. These battens will enable us to form, shape and fasten the foam panels. Because we are using a female jig, we had to take into account the 20mm thickness of the battens.
The distance between the frames varies between 50cm and 100cm. The battens we used are 420cm long, the long length gave us the advantage of being able to bridge four frames at a time, thus giving us a nice, smooth curve. There are also fewer joints to make between the battens-ends.
The first step was to accurately fix battens left and right of the Center line along the length of the keel.
The Center line previously been marked out on the frames. These two battens together form the keel, the backbone of the mould. After the centerline we installed a batten on the waterline. Schionning designed the G-Force 1500C with the home builder in mind. The hull above the waterline is fairly straight compared to that below the waterline. This means the foam will be easier to shape and require less support. Battens above the waterline could therefore be placed further apart. The hull below the waterline is heavily curved, so the panels require more support, we therefore had to mount the battens much closer together.
Joining the battens is easy and doesn’t take long. It is however, important to make sure that they follow the profile of the hull; this will prevent bulges in the finished hull.
The bow requires the most attention.
The bow was very tricky to lay-up because of the extreme compound curves. The hull bends round not only lengthwise, but also in height. Our 20mm battens are simply not flexible enough to follow these curves. This problem was solved by laminating two 9mm flexible multiplex slats and bonding them to form a single batten. The missing 2mm was filled with a thin strip.
The outside of the hull will be foamed first. To make access easier, any internal battens will be fitted at a later date.
In mid-January we reached a milestone:
the two hulls were finally ready for installing the foam panels.
Working with foam, a nice challenge.
This is the first time that we’ve worked with foam, we did however do a lot of research beforehand. We decided to use as wide a panel as possible. This will reduce the number of seams in the hull and also reduce the chance of air leakage (see the section on ‘Building Method’).
Our ‘CoreCell’ panels were originally 122cm wide by 250cm long. Using a circular saw, we cut each panel into three panels each 40.5cm wide and finished the panels off by chamfering the edges with an electric Router. Chamfering the edges makes filling the seams a lot easier.
Thermo forming the foam panels.
CoreCell foam is easier to form when warm. The optimum temperature for forming is about 60°C. Henny (Fram) had good experience by using a hot air paint stripper for thermoforming the foam up to 40cm width. He also 'promised' that it would take a little practice, probably 6 panels or so, to get a ‘feel for it’.
The first panel went well, but was very tricky. The problem was getting the right amount of heat into the panel and keeping it there without causing local overheating. Foam cools off quite quickly and the panel loses its flexibility. It takes to much time to thermoform 40 cm /20mm panels. Henny used 16mm CoreCell panels wich needed less heat than our 20mm.
One possible solution was to reduce the panel width to 30cm, but that meant having more seams. After a bit of head-scratching Paul decided to use two hot air guns mounted in a simple wooden frame. Now we're able to introduce more heat and cover a greater area in one pass. After four or five panels using the new, improved double hot air gun we had it down to a tee. Besidses enough heat it's also very important to heat it under tension. This really speeds up the process!
Foam that has been formed should be kept in place while it cools. We temporarily held the panels in place using wooden slats that were themselves either screwed or clamped. The foam panel was then fastened to the battens from the outside using self-tapping wood screws. It was nice to be able to work for so long without using a drop of epoxy. This is definitely one of the advantages of this method of construction.
We started laying-up by placing the first panel roughly in the middle of the hull where it’s less curved. The next panel was placed to the left of that panel and the second to the right, slowly working our way out towards the bow and stern.
We developed an efficient routine. Paul first formed and clamped a panel heading the bow, then moved on to the next heading the stern. At the same time Jolanda ran a line of tape over the battens. The tape forms a non-stick barrier between the seams and the wooden battens, protecting the battens from any leaking resin. She then moved on to fixing Paul’s previous panel from the outside, always staying one panel behind Paul. The forming and clamping, and fastening and taping activities took about the same time, so we were able to work perfectly in sync.
We found ourselves having to modify the panels slightly as we got closer to the more curved bow and stern. This slight re-shaping was necessary to keep the panels vertical and maintain a good fit. With the curves at the bow it's easier to form 20cm of 30 cm panels instead of 40cm.
Once we got used to working with foam we were able to work quite fast. Laying-up the foam panels took all-in-all about 90 hours. You can see a slideshow showing step for step how we did it in the "How do you do it?" section.
Cold, cold and even colder.
We were hoping for a mild winter this year, but temperatures have been hovering around freezing for a long time now. Our plan was to have the starboard hull ready for filling the seams now, but it’s been too cold. The resin/micro-balloons mixture used to for the beading can only be used above 10°C and to do the epoxy infusion we need temperatures of at least 18°C. Final curing of the hulls will require heating them to 50°C for approximately 24 hours. This seemed like a good time to invest in thermal insulation for the workshop. Insulating the workshop would be a project on its own. We finally managed to install insulation panels over the 10mx20m work floor without using additional vertical supports. Any supports that we added would get in the way of the hulls.
With the insulation in place we can now concentrate with the task of building a boat.
Now, at the end of March we're glad we finished the insulation job. Soon we will start with the resin/microbaloons and hopefully we can do the first vacuum infusion tests in the end of April.
December 2012. We were finally able to start building the jigs for the hulls.
The design that we bought from Schionning was so new that we had to wait while the first set of drawings were being scrutinised for CE approval.
We made use of that time by going ahead with preparations for the build. We also took the opportunity to make a scale model of the jigs for the port and starboard hulls.
These models turned out to be very useful, giving us a good idea of what the final jigs will look like. After studying the models for a while we decided that some frames looked a little weak around the outside, and that others needed strengthening at the bottom. Based on our new insight, we decided to modify the frames by adding an extra 10cm around the outside edges and strengthen others where we felt it necessary. We were able to do all this with our available stock of forty MDF panels. It became clear to us that Schionning had put a lot of thought into their design, and how to build it. Where possible, parts have been designed with straight edges. This allows us to make efficient use of our building materials.
Building the Jigs
As you’ve may have already read, by 'Building method' we decided earlier in the planning phase to work with a female jig. We install battens in the female jig to get a good mould. In autocad we subtracted the height of the slats from the frame profiles. There are eighteen frames per hull, many of which are made up of three pieces. We had to cut out eighty-six parts in all.
We have to use three datum lines in order to accurately position the frames: the Waterline, the Centreline and the Deck-line.
These were all clearly marked on each of the frames.
Paul designed a cutting plan that allowed us to cut all the pieces out of our MDF panels with as little waste as possible.
We did consider having the pieces cut professionally using a computer controlled laser-cutter or router, but in the end decided to do it ourselves. This is where our A0-plotter came into its own.
On Friday 7 December all the materials necessary for the jigs had been delivered. Full of enthusiasm, we made a start.
Using A0 size prints from our plotter, we were easily able to transpose drawings onto the MDF panels. It was tempting to trace around the cut-outs from the port hull and use these as a template for the starboard hull. It would appear to be a lot faster this way, but if you make a mistake, you’ll have two parts to re-do instead of one. There are only a few variations of jigs, but if you saw the frames in one go you know exactly what to look out for and the job goes quite quickly.
After three or four evenings Jolanda had managed to transpose all the frame drawings onto the MDF boards and Paul had already sawn a few out.
When not jig-sawing, Paul spent time to assemble the frames, it was also a good opportunity to see if our plan was working.
Spending hours lugging large MDF cut-outs around, getting down on your knees to assemble them and then moving the completed,
full size frames around is absolutely exhausting.
It’s a nice thought knowing that this will not last for forever, and that in just a few days we will be able to start working with luxurious,
light and easy to handle foam.
Whilst assembling the frames, we took the opportunity to strengthen the weak looking areas fit legs.
We also fitted temporary battens to keep the frames in shape.
Look at our photo compilation if you want to see step-by-step how we made the buildingframes..
In this facebook album you can look at more pictures.
Aligning and rigging the frames.
Whenever we’re busy working away on our boat, tended to find ourselves drifting off and thinking ahead to the next steps. It is this curiosity that becomes the driving force in the build and keeps the pace up. Hopefully we’ll never lose this drive.
After completing a few frames it was clear that our plan was working well. We decided to finish the remaining frames together at a later date, but first we wanted to make a start on assembling the starboard jig. Following the positioning of frame 1 comes the positioning of frames 2 to 18. Starting with the stern as a reference, each frame had to be accurately positioned in all three planes, and relative to each other. The final position of each frame was then marked on the floor.
This is what we managed to achieve in the first month of building.
Here you can see how busy we’ve been:
We’ll start fitting the slats; these will form the base for the foam layer. By the end of the month we hope to have a fully foam-clad hull.
Started with buildingframes
Battens in buildingframes
Foam in hull and insulating shed
Insulating shed and foam in hull
April/ May 2013
Filling and sanding Microballoons
More foam in hulls