Referring to the entry on the sailboat radio controlled I built back in 2006 (ancient works: Sailing Radio Control), I wanted to explain how it was made, at least the part of the model, from which the molds were obtained and hence the parts and everything else. Also, I put up for sale all drawings I had to make at that moment with everything you need to build the sailboat as I did. If you are interested, you can find it here: RC Yatch
As we said in that entry, everything starts with the drawing of sailboat, in my case, I got the sailboat 2000 America Cup, Luna Rossa.
The resources at its disposal at that moment were far from what I have now, but with a bit of imagination you can still continue doing interesting things.
First, computer work. Based on 2D drawings, obtain the 3D hull split it into two: Hull & Deck. These two pieces will stick later, forming a hull with a watertight seal. And of course designing the other components and their location. All that we can go ahead and plan on 3D, we would save having to improvise on the actual model, which is a big advantage, of course.
Once I have the model of the first piece, hull, you have to plan how we are going to build. Since I did not have CNC, decided to make the three-dimensional shape with polyurethane foam shaped panels. They can be bought in any supermarket DIY, with a format of thermal insulation panels. I got 3 cm thick. Well, the idea is to go by then every 3 cm sections of the hull shape, then gently sand it to the desired shape.
In the drawings on sale are in DinA4 format DXF templates to print and cut the foam directly, so it is very easy to mount this model. Obviously mount a strong enough foundation for it remains straight, go support it all, a sort of “false keel”. Everything has to be well stuck with a “compatible” glue. Do not ever stick with glue, glue solvent-based or polyester resin … because you will be left to you without polyurethane foam. I personally use Epoxy resin, and a tip, do not use glue around the edges, because when hardened, when sanded, the edges remain marked, as the areas with glue are harder than the foam, not be thoroughly abraded.
Once this all well attached, and you can start sanding! Fine grit sandpaper, I recommend starting a 300 grain, with patience and care not boot chunks of foam. The trick is to sand down the inside left edge of each section at the minimum. Right there we must stop.
When form convinces you, you have to harden the surface. You can use a layer of fiberglass and more resin Epoxy (albeit more expensive, worth it) Here I recommend always before you start working with resin, have all the materials on hand and ready, as well as the site clean and tidy right, because it is very annoying to have to go find scissors, for example with gloves smeared with resin. When everything is ready, you should get something like this:
The idea of this is to get a smooth and geometrically perfect as much as possible to make the mold to be released our boat. And it’s not like, obviously. This is where the more laborious process begins. You have to putty and sand until a mirror polished surface. Putty to take well to the fiberglass layer, need to pass fat grain sandpaper to scratch the surface and get a good grip. With a 40-60 grit will suffice. Nor have to sand too much, do not want to go through the fiberglass and foam reach, obviously.
Putty bodybuilder, readily available, and easy to apply. We must put past not very generous putty, but enough to cover the surface. Here and depends on the skill of each. Ideally, the model must be covered with a layer of a homogeneous and constant thickness everywhere, which, by hand, is not easy, but with a little tact can get a good result. Remember that excess putty, corresponds to more work sanding, so beware of excesses.
Obviously, with a CNC milling machine, this step is not necessary, as directly mill on excess putty, and stay perfect in the absence of a small sanded, but it is also true that we could have done the entire model without going through the foam, but hey, if you do not have a CNC, this method is very valid!
It is important to be sure that the way that we obtained with the sandpaper, so I made some templates that are included in the plans, to see not only that we no sanding for more, but we are leaving the symmetric model
After a lot of sanding and lots of putty should remain something like this:
Well, now we just need to define the edges. When we get to make the mold, this should have defined some surfaces perpendicular to the hull, which will, on the one hand delimiting us to the end of the piece, ie, where we cut the carbon part later, and another to be able to support excess fiber. These surfaces, taking advantage of what we have all 3D modeling, what can we draw from perfectly flat:
You will find in the drawings the supports, which can be perfectly foam, and that will make the surface strips of plywood of 3 or 5 mm. These surfaces, I recommend applying some putty to facilitate the release, although there is no need for a high surface finish, ie not have to sand as much as in the model.
You ought to have something like:
Now the hull is ready to take the molds. But beware! do not forget that the boat has two parts! With deck also have to repeat the same procedure.
Well, now you are ready for the molds, but that will be in the next post.