Might a parallel tube/3D printed component mast appeal to you at all, Graham?  I’d be happy to do a little more design work on this, if you need a diameter at deck level greater than 177mm.

David Tyler wrote:

Might a parallel tube/3D printed component mast appeal to you at all, Graham?  I’d be happy to do a little more design work on this, if you need a diameter at deck level greater than 177mm.

Hi again,

I have looked through the entire thread on that 7-inch mast now.  Not that I am any wiser on how it is done.  I would have to find an experienced 3-D print technician, I guess, even if I had the appropriate files from you. I was interested to note the heavier wall-thickness of the alloy tubes you used than I had on Arion.  I have no idea however if 7-inch dia at the partners with the heavier wall would be OK for 40 sq m of sail area.  Interested in your comments on this, too.

Graham wrote:

David Tyler wrote:

Might a parallel tube/3D printed component mast appeal to you at all, Graham?  I’d be happy to do a little more design work on this, if you need a diameter at deck level greater than 177mm.

I have been looking at available tube sizes.  There seem to be two options.

The first is to use a 177.8mm X 12mm bottom tube (ID of 165.1mm) which comes in a 6m length, followed by a 162mm X 6mm middle tube (ID of 150mm) which also comes in a 6m length, with a short 150mm X 3mm topmast.  Assuming 1m of bury for each tube, this would give a 2m topmast.  Or I could cut the tubes, or increase the bury to give a 3m topmast.  I have no idea if it is strong enough but suspect it might be given the wall thickness of the lower two tubes.

The second option is more complex.  I can get a 200mm X 12mm tube, (ID of 176mm), but only in a 4m length. Then a 168.24mm X 4.75mm tube but only 3.3mm long, followed by the same 150mm X 3mm tube, but it would be 5m above the join.

The first option seems more elegant, if strong enough, which I think it might be.  Once I have 2-3 panels reefed down, the yard will be in a strong section of the mast, for sure.

I think there’s something amiss with these figures, Graham. 177.8mm (7”) - 165.1mm (6.5”) indicates a ¼” wall (not 12mm), which is not strong enough. On the other hand, 200m x 12mm is too strong and heavy, and is over the guideline of wall thickness<5% of diameter. Are you sure it has a 12mm wall? 8" x ¼” wall (203.3mm x 190.5mm) should be available, and would be my choice, followed by decreasing steps of 1” in diameter - 7”, 6”, 5”. It’s rare to find tubes that sleeve perfectly together without needing any internal sleeves, and I think it’s just as well to accept the internal sleeves and their accompanying 1˚ conical fairing pieces that will permit step-downs of 1” in diameter. 

Could you post your source for these tube sizes, as one of them, 168.24mm, seems to be rather non-standard, neither imperial nor metric. 

David Tyler wrote:

Might a parallel tube/3D printed component mast appeal to you at all, Graham?  I’d be happy to do a little more design work on this, if you need a diameter at deck level greater than 177mm.

In essence, all I did with the first stage is to replace the messy, labour-intensive method of using epoxy/glass to fill the gap between two tubes, and then fairing the join with something approximating a cone, with a method that reduces the amount of time, labour and skill to minimum. 

From there onwards, you could treat the assembled tubes in a similar fashion to a one piece tapered tube, or indeed a wooden mast, using the traditional/PJR methods of making a masthead fitting, deck partners and heel. But I wanted to see if I could automate the whole business still further, by designing those areas with 3D components that required the minimum of hands-on input from the busy rig maker. 

3D printing is an “additive” manufacturing method: instead the “reductive” methods of taking a chunk of material and cutting away some of it until you have the shape you want (turning and milling metal, all woodwork) you squirt molten plastic out of a tiny nozzle in a way that’s controlled by a computer program to build a part up in layers. That’s it - not complicated in its basics, but needs some skill and knowledge to make sound and strong components out of suitable materials. Casting and injection moulding are also “additive” methods, but they need more skill and knowledge, and crucially, more investment in tooling and machinery. Whereas with a relatively low cost 3D printer that requires no further patterns or moulds, and readily available materials, there’s little to limit what can be designed and made at home. If one can imagine it, one can print it. And now there are 3D printing services in all major cities. Just as one would send a file to a 2D print shop to have them put some ink onto paper (as we do to produce the JRA magazine), now one can send a file to a 3D print shop to have them put down some plastic or metal in the shape you desire (or even concrete - you can have a house printed for you!). A quick search for “online 3D printing services in Australia” yields plenty of companies to approach. 

My own printer will make anything that will fit into a 250mm cube. That’s what limits me to making eg deckrings for a maximum mast diameter of 7”. Commercial printers run “print farms” of machines capable of 300mm cube and larger - rows and rows of machines turning out everything you can think of. Look closely at many household and industrial items that are only produced in low numbers, and the chances are that you can tell that they've been 3D printed.

Thanks for this.  I have looked up 3D printing services here, and as you say, there are plenty of companies to choose from.  I like the mast on that Westerly Konsort, and assume the files you made for that project might be a close fit if I could source the same-sized tubes?

Before I can go down that road, though, I'd have to source the appropriate sizes of tube here.  As so often in Australia (I don't know why - she'll be right mate, maybe) that seems to be a problem.  I can source a 6m length of 7in tube (177.8mm with 12.7mm wall thickness, which gives an ID of 152.4mm) for the bottom section, and a 5in tube (127mm with a 4.3mm wall thickness) for the top section, but it seems that there is no off-the-shelf tube of 6in diameter with 1/4in wall thickness in Australia.  The only standard 152.4mm tube here has a wall thickness of 3.35mm, which is not strong enough.  I will make some phone calls and see if I can get one custom made, but it will be pricey, if it is possible.  People have built Colvin Gazelles here though, which use that size of tube.

I could use a 4m length of 200mm x 12mm (ID 176mm) for the bottom, with a radical step down to a 6m length of 162mm x 6mm, then a topmast of 150mm x 3m.  With a bury of one metre for each join, that would give a 3m top section.  The fairing for the first join would need to be much longer than you used on the Konsort.

I'd prefer to source a 152.4mm x 6mm middle section if I can find one. I'll make another post when I get some feedback.