Tuesday, June 02, 2020

Cutting frames

One advance since the plans for La Passagere was filed away is the silhouette cutter. What better way to produce frames than transfer the plans to the computer and let the machine do the work?

I scanned all the drawings in and then re-drew them in the cutting software. While doing this I decided to make the model a bit bigger - the original version seemed to be an exercise in micro-modelling and when it comes to boats, this just means loads of messing around minimising and distributing weight. Technically interesting maybe, but I can't get excited about it. You also end up with a model that can only sail when the weather is perfectly calm.

Stuff that, I'll just it bigger.

Drawing out the bits was interesting as the beezer curve tool isn't like the one I'm familiar with in Paintshop Pro. They work in sort of the same way, but not exactly the same. Still, I managed.

All the bits were cut in 1mm plastic. I made all of them twice so they could be laminated up to get some thickness and (hopefully) strength. The cutter won't go all the way through, but it cuts enough of a groove to make final cutting with a knife easy.

One lesson learned is that when drawing something like a frame that should be mirrored around the centre, draw half of it and mirror. Don't rely on the original drawing you are copying being accurate. One frame wasn't, although fixing this didn't turn out to be too difficult.

I used a guillotine as a building board because of it's a nice flat surface, and that I'd had it out to chop up the plastic to fit it in the cutter. 

The basic frame went together OK, but when I started to cover it, things got wobbly. The original model was made of wood and it's a lot stiffer than styrene sheet. The glue joints proved to be less strong than I'd hoped too. 

Basically, trying to cover the hull with single pieces of 0.5mm thick plastic was going all wrong. I couldn't cut the pieces perfectly and trying to trim them to fit didn't seem to work very well. 

So it went in the bin. A nice idea, but not a success. I think there is something in this method, but I need a stiffer material and that won't go through the cutter I have. 

I should have remembered building my scratchbuilt Brede which also has a plastic hull. The boat never gets sailed because it always feels fragile. That and the hull is annoyingly not the perfect shape. 

Despite this, I think the project was an interesting experiment. OK, I've ended up with bin filler rather than a model,  but I've learnt quite a bit. One thing is that I've learnt I hate making boat hulls. Too many curves. Too important. 

However, this project isn't dead. It sleeps as I have another idea for the hull, but it will have to wait for a while...


James Finister said...

If you have the drawings done could you not get the parts laser cut in ply?

Or, indeed, scale them down and build a static 4mm version

I must say that this is just the type of prototype that appeals to me. I think Midwest Models used to do a similar "short" ferry based on the same hull as one of their tugs.

Anonymous said...

Wasn't the original model planked because with the hull shape it couldn't be done with a broad sheet?

Phil Parker said...

The model was large sheets because it was a hard chine.

However, as I say, all is not lost. All you need is a large collection of vac-formed model boat hulls...