Making a half model

Some of you might have seen my excited tweet about our half model last week when Si emailed me a picture over from Fibrefusion, the profile cutting company run by Steve Neal in Falmouth. Earlier that day Simon took over a memory stick containing his design for our boat, and Steve very kindly agreed to let him record the process of turning several large pieces of glued together MDF into an exact scale replica of Si’s design. Si also took a couple of videos, so I’ll try to get those up here in due course. In the meantime, here’s how to make a half model using a massively cool robotic three dimensional power chisel. You may want to try this at home.

Sadly, although the process of making a half model this way is somewhat akin to magic, it is not just a matter of inputting a file into the cutting machine and pressing go. The machine – a three axis router –  works from its own cutting software.

So before starting the cut, Steve had quite a bit of work to import Si’s design into the software and get it to the stage of being ready to cut. To over simplify what is in reality a complex process, it’s a case of giving the router a series of intricate directions that make up its cutting path, which in turn produces a physical replica of the original CAD drawing.

It’s also a question of working out how best to cut the shape out given the material and the cutting tools available. We used MDF, as it’s cheap, stable and readily available, but you could use an old toilet roll or some pipe cleaners if you like.

Once that was done, Steve set up the router to cut by selecting the appropriate tools and calibrating it. The sheets of MDF were then glued together to the required thickness for the eventual model, and placed on the bed of the router. The machine has a powerful vacuum which holds the materials being used in place during cutting to ensure accuracy.

The router then performs a series of cuts, each one more accurate than the last.

The first cut is a very coarse one, which produced a rough shape of the hull for us and discarded much of the redundant material.

As you can see, even by the end of the first cut the shape of our boat was beginning to emerge.

The machine then performs a second cut using a different tool. This produced a close likeness of the computer model and left the hull ready to be faired.

Finally the machine uses a third tool to sharpen any edges that the rounded second tool can’t make square, and to hone the final shape.

And that’s it, a finished model! Si gave it a quick light sand, but apart from that it came off the machine completely smooth and perfect. So here’s one we made earlier…

Including the time taken to set up the machine, change tools and make small adjustments during the cut, the whole process took less than three hours. It’s pretty incredible.

We’re both absolutely delighted with the half model, and incredibly grateful to Steve at Fibrefusion for all his patience, time and effort.  We now have a tangible representation of what is to come and a solid and sturdy scale version of our boat. Which is exactly how we like our models.


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