David wrote:

bulkhead. Once this is done then the hole for the mast can be cut. I usually cut the mast hole an inch larger than the mast. When installing the mast I wrap the mast in 5mm thick rubber sheet taped together for a tight fit, I then caulk the bottom of the remaining gap with 6mm diameter rope and fill the  gap with thickened epoxy. This gives a flush join at deck level which can be waterproofed with narrow strips of canvas set in clear silicone.

And here I thought that the "only" way of dealing with partners was wedges and a boot. I am now wondering: A) can this be written up in a more comprehensive form and added to the information section? B) how many other ways of dealing with securing and sealing the mast at the partners are there? and are there limits depending on size? (aside from welding steel masts to steel partners) While this applies to any keel stepped mast, most sailboats are deck stepped and the art of keel stepped, unstayed mast mounting is of particular important to the JR.

I am assuming that the mast hole being 1inch/25mm larger means diameter rather than radius.

Thanks David - having measured up on the boat now I would agree with you.

The second mast position suggested by Arne sits just in front of the existing deck hatch as I suspected originally (pictures one, two and three). I suspect a very slight forward rake might be helpful to assist with clearance from the hatch itself. I think the hatch may also need to be reversed to open away from the mast. 

The internal position of the mast doesn't seem to interfere too much with the berths in this position. I need to revisit this with something like a length of plastic pipe the same diameter as the mast, but it doesn't really impact on access to the berth, but is more an intrusion at about thigh level when lying down which seems to leave both berths useable. 

The good news is that the mast step location here is basically into a forepeak locker which has no lining, tanks etc. so the bottom of the locker is just the hull moulding - the sides meeting in quite a sharp "v" at the base at this point. See picture here. It looks like this would be a fairly straightforward location to glass in a mast step. 

The reinforcement to the partners at deck level will require some more thought as internal reinforcement inside the cabin may not be straightforward. My initial thinking was to fabricate a fairly substantial external "plate" supporting a tube through which the mast is stepped. As per the photos the cabin top is raised above deck level in this area and I envisaged that this could sit on top of the raised area with a flange following the same profile and through bolted through the vertical sides of the cabin top (as well as being through bolted around the mast tube). I need to sketch this out probably as I'm not sure the written description makes sense. The deck does seem fairly solid (and the anchor windlass has been bolted through it with a backing pad for many years with no issues!) but it is difficult to know how much reinforcement is really needed here. 

My only real concern looking at this in profile from the side is whether the mast position is too far forward in relation to centre of buoyancy as the hull really narrows down up forward and is there an issue with having the weight of the mast this far forward? The opened  hatch in the photo gives a good indication of the mast position. That said, I presume it is the centre of gravity of the entire rig (including sail bundle) which is relevant so maybe there is less difference than it would seem between this and Arne's original suggestion with the mast slightly further aft, but more balance on the sail...

I did occur to me as I was writing this that I neglected to measure the amount of bury this mast position gives, which I will need to check at the weekend, but based on the requirements noted in PJR I don't think this would be an issue.

Clearly there is a lot of planning and design still needed, but it does seem as if a conversion should be viable which gives me more confidence! 

Anonymous wrote:

 

It sure is. I have always liked that (PBO Nov 2011) photo of Poppy squared away. (See her in the background?) That photo says it all. 

Thanks Graeme - I remember reading that article actually! Definitely a case of "a picture paints a thousand words"..

Thanks all - some very helpful advice here!

I will be down at the boat at the weekend so will have a better opportunity to look at this, but I think that revised mast line would be forward of the deck hatch. 

As per Graeme's notes / sketch I need to work out how the (already fairly tight) system of doors between the heads / wardrobe works with all this. Currently it's a fairly clever arrangement where the wardrobe door (to starboard) can close off the fore cabin leaving the separate heads door (to port) closing off the heads from the main saloon or you can open that door to close off the main saloon giving what's effectively a much bigger heads compartment for changing etc. 

I will get my tape measure out at the weekend and try and work it out. 

I hadn't really considered offsetting the mast, but in my head I had always assumed that an offset mast would be offset to starboard given that the sail lies to the port side of the mast so it effectively keeps the sail closer to the centreline - although PJR seems to say the offset doesn't make much difference to sailing performance.

In terms of sail area my initial view was to err on more rather than less on the basis that it is easy to reef if needed, but I appreciate this can be taken too far! We don't really plan to do much racing, but would want to make sure we get reasonable downwind performance. 

The existing 135% roller genoa is approximately 20sqm so quite a bit larger than the one shown in brochure plan. And yes it does suck downwind unless you are prepared to fly a spinnaker, which for me is not viable / safe when shorthanded. We do have an asymmetric cruising chute, but that isn't much help either when sailing lower than a broad reach.

The closest comparison in terms of sail area I guess is sailing goose wing with the genoa poled out, but I would imagine the junk rig is a bit more efficient than this in terms of presenting the sail to the wind and having more area higher up in the clean wind? So on that basis the 37 sqm feels like it should be about right. Ultimately she is not a very easily driven hull so a junk sail which is big enough to sail effectively downwind in very light airs is going to be unrealistically large and I'm probably going to be motoring in that scenario. 

I have bit of insight into how a transom hung rudder would work as we have self steering gear mounted on the transom which requires quite a long bracket at the top to get the shaft for the self steering gear vertical, so I think it would be possible, but would be quite a big modification and may be easier to redesign the existing skeg / rudder. Leisure Yachts did make a Leisure 29 which is the same hull design but lengthened to give a longer cockpit and this did apparently solve the weather helm issues. 

David,

as for sail area, I guess Jon should have a say here. Now I had a closer look at the original Bermudan rig. Tracing the sails, the mainsail came out at only 12.7sqm and the shown working jib is only 12.2sqm. It will thus take a large Genoa 1 to reach a sail area of 37sqm. Downwind, these rigs really suck.

My suggested JR with 37.5sqm in it, although not big, will produce a lot more oomph than the original rig. Upwind, the JR is taller, even with a shorter mast, and downwind that single sail will make much better use of its area than that masthead Bm rig ever did.

I notice that Jon’s boat sits downriver from Ipswich, almost next to the North Sea, so maybe it makes sense not to overdo it. A SA/Disp of 18.1 isn’t that bad, after all.

Arne