Not on the topic of the sail, but more on increasing seaworthiness of the TS16, I have been cautioned that my boat can be very difficult to right in a knockdown.
The factors seem to be:

1. The lack of dedicated floatation in the standard design.

2. The lack of built-in ballast. It is confined to the steel swing-keel of about 60kg.

3. The fact that the boat can tip easily and stabilises readily at 180deg, making it difficult to right.

The measures I plan to take to deal with these issues:

1. Install a water tight bulkhead as part of the modifications to accommodate the new mast. This will allow the bow to float as high as possible.

2. Make the new mast step as water tight as possible to reduce water ingress in a knockdown.

3. Adding as much floatation as possible (at least 600kg of displacement), probably in the form of cheap styrofoam blocks under the deck and cabin floor, and in the rear of the side storage lockers. This to try to make the boat sit as high in the water as possible in a knockdown, making it easier to self-right or to be righted manually.

4. Adding about 150kg or more balast as low as possible, possibly in the form of lead bolted to the skeg/keel somewere.

5. Making the mast as buoyant as possible, possibly with seals at the ends and/or a mast float to make the mast positively buoyant to reduce the likelihood of a 180 knockdown.

Can you think of anything else I could do? Another weakness is that the centreboard trunk lets water into the cabin in a knockdown. What could be done to reduce this, other than making the boat sit higher in the water?

Steve,
I like that you are load conscious, but I think you will be all right here. One issue with rising and falling AR with constant number of panels, is the ratio “P/B”, shown in Practical Junk Rig, PJR. P is the vertical height of a parallelogram panel. Although I have drawn a range of master sails with AR from 1.80 to 2.25, I have only built and used sails between AR of 1.87 and 2.15.

The P/B of that AR-2.15 sail (Broremann) was 0.6m/2.45m = 0.245,

and Johanna’s AR-1.87 sail had P/B = 1.2m/5,8m=0.207.
(The P/B of the master sails is shown in Fig 4.5 in Chapter 4 of TCPJR).
The difference does not sound radical, but here is how I reason:

• ·         When the AR of a 7-panel sail raises much over 2.15,  the spans of luff between the battens may end up so tall that the luff gets reluctant to stay straight  without a downhaul to stretch it. Better then to make the sail with eight panels.

• ·         When the AR drops below 1.85, I am worried that it will be difficult to produce as much camber (6 – 8%) as I want. Better then to make the sail with six panels.

Battens
On the sail of Frøken Sørensen the boom and most battens are 22/2mm (batten 2 is 35/2mm). These are on the light side for her, but are probably plenty good on your boat.

Finally, your boat is very generously rigged, even by my standards. This is an argument for choosing the 6-panel rig; to shorten the mast as much as possible. I would also encourage you to fit the heavier centre-plate you talked about  -  and compensate with more flotation...

Good luck.
Arne

 

Arne Kverneland wrote:

That sounds reasonable, or maybe even a little over the top, but it depends of what alloy you use. How much will it weigh?

BTW, tonight I drew up another version, this time a 6-panel sail. I added it as an appendix to the last note.

Arne

 

I would think a maximum of 20kg with everything fitted. A 6.5m tube 100mm x 3mm weighs 16.4kg. With 3 sections of reducing diameter it should be less than that. The difficulty is going to get tube sizes that will nest reasonably. I will have to source a few different suppliers I think to get what I will need.

If I can only afford the standard softer alloy I might need to look at a low aspect sail to reduce stresses higher up the mast, but this is what I used for my last boat and I have had no sign of bending in any conditions so far.

If I was to use a straight sided mast of 100mm x 6.2m would that work ok do you think?

Ok, I think I've managed to make sense of your mathematical gobbledygook Arne, and I am able to work out the dimensions of the sail, and the panel cambers.

Now I need to consider a mast.

I was considering a 3 section nesting mast of aluminium tube. I did this for my sailing dinghy according to the B & B Yachts design. The tubes are of decreasing diameter and the gap is filled with fibreglass cloth and epoxy wrapping. It makes for a very strong mast and lighter than a straight aluminium tube.

If I start with a bottom section of 101.6 x 3mm and then progressively smaller, would that work for the JR?

Steve,

yes I realise now that page 1 became a bit over-loaded.  I will see if I can make a drawing with correct dimensions on it one of these days.

However, you should be able to find the numbers yourself. Then you need...

• a print-out of the master sail with AR=1.85, found on Chapter 4 (Both sheet 1 and 2) 
• A calculator and pencil
• That linear scale factor  F=0.67953

By multiplying all the dimensions on than master sail (not areas) with F (0.67953), you will find all the dimensions for your sail. It shouldn't take more time for you than for me.

Arne