Wednesday, January 23, 2013

Part 2 - tooling up

I was thinking of calling this port 'tooling around' because that probably best sums up what I've been doing for the last month. No-one cares about that though, instead Im going to run through the process for creating all the moulds needed for the new build.

Because I still have access to the CNC router - its now being housed by my mates at Street&Garden Furniture Co. - it was pretty straightforward to send every part, big or small, to it and create a set of female moulds. Detailed things were made in ply or MDF, and the large simple shapes were cut from 'Isoboard' EPS insulation foam, recommended by the guys at CG. I designed the boat and made the 3D model so that everything would be able to be done this way, and it was super quick to pull parts out, create the toolpath and press print. I set up a new dust extraction system to deal with the polystyrene dust, and it works really well. didn't miss a drop.

Here's a photo of the setup, and another after a weekend's of successful routing.



The bigger parts took an hour or two to cut, the smaller ones obviously were quicker. I had a couple of small issues cutting the foam where it melted etc, but that's boring so I won't go into it. Thick parts were made in layers 75mm thick, and then guled together with epoxy later. The rough-ish surface (3mm step) sanded back easily and I then sealed it with some epoxy and colloidal silica bog. Then another quick sand, another layer of thinner epoxy/silica, carefully applied with a credit card, and you're done! The moulds all held a good vacuum with no problems, important because you can't envelope bag it as it compresses the foam, and the surface quality was generally within range of 'high build'. It's gotta be the quickest way to make large composite parts.



The MDF/ply bits are now pretty straight forward. I've learnt that it's better to cut them with a much finer stepover (1.2mm or so) so that you almost don't need to sand them. It takes a bit longer on the machine, but saves you lots of stuffing around later. Then one coat of resin and a sand and they're good to go. The foil strut mould was the last thing I did, and turned out the best.

8 comments:

n4rkla said...

Looking good Nick. So jealous.

cmaas said...

Nicely done. The design looks really good.

You're not making pre-preg parts in those EPS molds though right?

It's interesting that you've designed the wings with a foil section. Am I seeing that right?

I for one would like to see ANY build pictures you are willing to post. I love this stuff.





nick flutter said...

Thanks guys! naa no prepreg, just bagging and then a post cure (of sorts). more on that later!

Nick

Andrew said...

Hi Nick,
Great to see that home built Moths and CNC are at least x2 in Australia.

EPS looks interesting, MDF is a pain to finish but I have heaps left over from the farrier molds. BTW love the painters planks for rails on the CNC, priceless.

Andrew
www.andrew-mcleod.com

nick flutter said...

Wow Andrew, amazing project, thanks for the link. Bruce mentioned you were building the boat, hadn't found the blog before. I'm daunted by the scale of it - I'm having moments of doubt just building a moth, I take my hat off to you for accomplishing something like that. I hope the rest of the build goes smoothly, I'll keep an eye on it from a safe distance.

EPS is quite good for some things. My deck mould is a good example, I'll do a post on that process later on. Not so good as you get more detailed, but it is cheap and quick to cut. I've got finishing MDF to an art form I think - the 1mm step made it super easy. I use quite a thin epoxy and heat it slightly to soak into the surface, and then sand / polish that. works well, really quick. I'd say I spent one hour total on my foil mould between coming off the machine and laying up the part. Will have to see if I get a good release when I open it up tomorrow.

Ha the painters planks were very premeditated! It was the cheapest way to buy a large alloy extrusion, I looked at all sorts of things. I bought three 6m planks and cut them up. A builder told me it was a "waste of good planks!" haha

Anonymous said...

What? You finish coat your MDF? Wax, PVA and go!

Karl said...

Oh that was me. Karl

Karl said...

OK I have no idea what just happened.

Looking good though!

What package did you arrive at for CFD?

K