Gary Pearce wrote:

Ironically the CNC for a model will be quite a lot higher pro rata as the cutter needs to be around 1mm or less, you have to move much more slowly or you snap the bit. 

The "sweet spot" for the ply looks like the Birch at $136 so thats $272 for the ply so thats AUD 659.50 total. 

Which is a very large amount for a 1.2 (ish) metre model boat that will never get wet but one needs to consider this as a "design cost" from which others may hopefully benefit in future.

We shall see.

Gary Pearce wrote:

Brunzeel (Brookvale) have 1220x2440x1.5 hoop pine for AUD 80

BTW: your thought about routing grooves on the plywood: it looks effective, but you need to be using quite thick plywood if you do this, otherwise you will be substantially weakening it.  Especially if the grooves happen to match up on either side.

David Tyler wrote:

Gary, thanks for the heads up on the missing line. I've added it, and uploaded a new version.

Yes, the board case position markings are just that. The cases will have to be made up separately and then fixed to the bulkheads. I was hoping that they could be marked along with the grid lines, but if that's not possible at model scale, it shouldn't matter. They would be useful at full size, but if it can't be done, then we can add some dimensions and pencil them on.

I imagine the hoop pine is a bit soft and weak for the details of the tabs, maybe? I think I'd go for the DMK birch. Mister Ply seems far too expensive for what it is.

FYI the CNC folk only need a pen tool to add the daggerboard lines. Full size they suggest a small groove. 

I wonder if tabs on the case ends (fore & aft)  into the bulkheads might make things more foolproof but need to think if thats possible for assembly.  Of course full size one could put vertical grooves in the bulkheads to look like a nice boarded effect .... if you were painting them :-)

CNC folk are recommending the birch which they have used before and like so thats probably the way to go. 

I will let you know what transpires.

David Tyler wrote:

A new version of the one sixth scale parts drawing, with the side decks added.

Once on the CAD a few minor discrepancies emerged. These would be easy for him to work around but its probably best long term if the master drawings are amended.

Station 3 is not joined at the top and so can not be cut out. It appears to only require a straight line across the top.

It was not immediately clear what the dashed lines for the daggerboard positioning were. On his CAD they appeared as tab holes that were not closed off at the ends. but on QCAD they just look like dashed lines which confusingly exceed the boundaries of the station. Are they markings of some sort for the daggerboards ? This particular shop don't normally use pens for marking and scribing marks into 1.5mm ply sheet is not really possible. 

Oh and he said he has some nesting software which may improve ply usage - he will see.

On the plywood front I have prices from 3 suppliers for 1.5 mm ply.

Brunzeel (Brookvale) have 1220x2440x1.5 hoop pine for AUD 80

DMK (Brookvale) have 1220x2440x1.5 birch (we think) for AUD 136

Mister Ply&Wood have 1200x1200x1.5 for AUD 143 (i.e. AUD 286 per full sheet)

I should get a quote from CNC shop mid next week and may then try a second CNC house if the price seems too high.

Cheers

David Tyler wrote:

 I'd say that having done the plywood assembly, the job's halfway there.

But yes using this technique you really _are_ much further down the track than "normal" when the structure is complete.

On top of which this will assemble very quickly IMO.