Anonymous wrote:

So I’m sure we can do something similar for your conversion, first choosing the tube size to be stepped into the boat, then the diameter of the next one, and that should be enough to get the required height. Then between us we can design and print all the components to make a mast and step it.

A modern version of the hybrid mast that has a wooden topmast going into a tube. Might this be something that other JRA members would be interested in?  

David, thank you for your help with this. And thank you for the original concept, which i think is superb.

I have drawn the junction between 4¹/₂" and 4" tubes, using a printed collar/fairing piece similar to your design.

I have assumed that the top of the collar needs a physical thickness, it can't taper to nothing. I think 2mm would be the thinnest I would want to go with PETG. The bottom of the collar is approx. 3mm. I've allowed for the tube to insert into the other by 460mm. I hope a 2mm step wouldn't snag anything.

I would plan to print on it's side, to avoid layer line weakness.

The thinner tube would need some form of physical stop, I was thinking of perhaps riveting a ring inside the larger tube at 460mm depth?

This is all on the assumption of using 4m of 5" tube, 4m of 4¹/₂" tube and 3m of 4" tube. With 1.2m buried and 2x460mm joints, this would give me just under 9m above deck, which may even be too much.

As you have suggested, a combo of 5", 4", 3" may be strong enough. This would give more substantial joining collars and would be slightly cheaper. Either way, the whole mast would come in at less than £500 delivered, much less than the £800 for a Norsk Hydro tapered pole.

What do you think?

Andrew, I think the main question is whether the boat’s value from your point of view increases or decreases if you convert it - and the resounding answer is that it increases hundred-fold - but I would say that, wouldn’t I?

You might recall a magazine article written by JRA member Jeff, about how he came to lose his boat Sesi on the rocks. He came to see me this week, to talk over how he could get an unstayed mast to convert his current boat, a Westerly Konsort. The first thought was the Hydro tapered tubes, but the strength of the largest of these was not quite enough.

Now that I’m getting into 3D printing, it seems to us that the way to do is something like the old Needlespar way of sleeving a smaller parallel tube into the top of a tube that is sized for the righting moment of the boat - but using 3D printed tapered sleeves above the join as fairing pieces. We asked for Arne’s opinion on the size of this bottom tube, as three heads are always better than two, and decided that 7" diameter x ⅜” wall would be strong enough and that I could manage a deck ring at this size, but not bigger. My printer can make a maximum height of 220mm, so if we step down from 7” to 6”, two sleeves would result in a taper of 1.5˚, which looks reasonable. Then a 5” tube with two similar tapered pieces would get us up to a maximum length of 14m, using three tubes 5m long, 7”, 6” and 5” dia, with a bury of 0.5m at the two steps.  

So I’m sure we can do something similar for your conversion, first choosing the tube size to be stepped into the boat, then the diameter of the next one, and that should be enough to get the required height. Then between us we can design and print all the components to make a mast and step it.

A modern version of the hybrid mast that has a wooden topmast going into a tube. Might this be something that other JRA members would be interested in?  

Slightly tongue-in-cheek posting here. I'm working out the details of converting my 20' Hunter Medina (with big thanks to Slieve and Graeme).

There's a lot to think about, the main one being where to source the mast, it seems like it might be the make or break. I can't afford the time to make a wooden mast and can't really afford the £800 to buy a tapered pole (plus it looks like Norsk Hydro might be going bust - Thanks for the heads up David Tyler).

It did occur to me that as old boats are two a penny now, will the £3k that my current boat cost me drop to very little if I convert her to a junk rig?

I'm sure it has been discussed many times but it seems a mystery that junk rigged boats aren't more widely accepted and valued. I remember going on Weaverbird in Scotland many years ago and thinking "why aren't all boats like this?" It has probably been said way too often.

As I said, tongue in cheek, I intend to go ahead if I can find a mast - any ideas?