Thank you David for yet again taking the trouble to give clear answer and reasons. I will pay attention to that. I think I have understood correctly: the buttresses would be placed so as to allow the U-bolts to go between them, radially, in the correct places…

I've seen plenty of concrete encased ballast in fc boats but never the dust. Interesting. But thanks Ron- it is the inevitable crevice between the two dis-similar surfaces that was niggling in the back of my mind - I was supposing it shouldn't be a problem where it is up against epoxy - a bit like your fibreglass. 

But..hmmmm...its all starting to sound like a bit of a bother, and to look like David is right (again!)

I was keen to hear from someone who has encapsulated ballast in concrete so thanks again Ron.  

Thanks guys, much appreciated.

Polyester resin is a bit cheaper than epoxy here, but given the need to purchase a sufficient amount to ensure not running short, it won’t be much cheaper. I might go with polyester, but have not yet seen a reason why not to use concrete. I am going to mull for a few days.

Here’s another one. 

Mast head fittings for a tapered hollow aluminium mast top.

(1) The construction

I have trawled the fora for combined wisdom on this (what a job, especially with my slow internet speed) and found many ways, of which Arne’s most recent cup arrangement might suit me best.

Or this even more elegant detail, which might be possible for me to have welded, since my top mast extension is not yet installed and not too unwieldy to transport.

(See photo provided by "Deleted user", May 2016)

I note that David T seems to prefer hanging U-bolts from the top plate, rather than what would have seemed to me to be the neater method of shackling blocks to hole drilled in the triangular buttresses.

No doubt there is a good reason for David’s preference?

My peculiar problem is a tapered aluminium top mast extension which seems not to be circular in section, so the direct weld (as in photo above) might be a good way, or packing with a castable resin might be the answer to fitting a Arne-type cap.

Otherwise, (and possibly anyway) the hollow tip of the mast head should perhaps be made solid by filling with resin, if thought necessary. Any such resin casting should be done now, while the mast is in two sections and I can turn the topmast extension upside down to do it. Or welding, while the thing is still “wieldy” enough to be transportable to an engineer’s shop.

(Annie and Arne’s webbing tangs might be just the thing for me, but I have not got started on sewing yet and maybe that method should wait until another time.)

Any suggestions would be welcome.

(2) The number and disposition of tangs

Here I am completely at a loss through no prior experience of the rig. Aware that it matters, but a little confused and I just want to be told what to do here.

I looked at a post from David T which described his disposition of tangs (3 o’clock, 6 o’clock etc) but now I can’t find it.

My configuration is probably reversed from the normal – my mast will be offset to port.

This is a detail I don’t want to try and work out by myself – how many tangs do I need and how should they be disposed? Thanks.

Yes, it leads to the right album, but if the right photo is opened, you could link directly to that:

http://www.junkrigassociation.org/Sys/PublicProfile/
38026503/Photo/82521785/86529062/0?dh=0&cppr=3

note that the URL has 'PublicProfile' in it - that's the thing to check.

You can use the cheapest polyester resin for this job. Mixing some sand with it, to a just-pourable slurry, absorbs the exothermic heat (as does the lead), so you don't have to do it in very thin layers.

The link doesn't work, Graeme - it's not to a photo in a public album.

But anyway, isn't this trimming ballast, to correct fore and aft trim? If the rig moves forward, shouldn't it be moved aft? I think it's unsafe to bond it in until you have the rig in and the boat afloat.

Tystie's lead ingot ballast was set in a resin/lead shot mix, and Ivory Gull's cast iron ingot ballast was set in a resin/sand mix.