Arne should know all about using stones as ballast. The Norsemen did so aboard their longships. I believe the idea was that they rolled out in the event of capsize.

Rocks

Whilst Blondie is out of the water we decided to take out all the magnificent river stones that formed the internal ballast. They might be traditional but loose stones don't seem too seaworthy. Although the stones looked numerous they weighed remarkably little and now take pride of place in our garden. The distribution of the stones was around the stern of the boat as follows: Lazarette 12.3 kg; Port Quarter berth 24.2 kg; Starboard Quarter berth 38.9 kg and in the bilge around the companionway area 73.5 kg. A total of 148.9 kg. Maybe they were placed there after the inboard engine was removed?

In a way the ability to remove the stones and replace them with bolted down lead may be an advantage to trim the vessel after the conversion to JR - change of mast position etc. 

My question is whether the stones placed in the quarter berths - close to the maximum beam of the boat need to be replaced in this position with a similar weight of  lead? Could placing all the lead in the bilge make the boat too stiff? 

Any suggestions would be welcome

Robert, yes, you are quite right, I picked the round for 8% camber from AR=2.0; my mistake. Somehow I didn't error on the 6% camber.

As you will see, there is not that big difference. The difference in round is much bigger if you jump from 8% camber (R=15.3cm) to 10% (R=21.7cm).

If you want to ensure that the camber does not come out with less than 8% in the lower panels of the finished sail, even if you stretch the sail along the battens (like I have done on my Frøken Sørensen), you can interpolate and choose a round mid-between those needed for 8 and 10% camber, and use R=18,5 cm.

Good luck!

Arne

Robert,
I just looked over the numbers you show us of your planned sail: The height and sail area are OK, but your found round (35cm!) of the lower panels is way too big.

Now I checked that table of the master sails in Chapter 4. With a planned camber of 8% the master sails lower panels need to be cut with a round of 21.4cm (on both upper and lower side of the panels).

Since your sail has been crimped to a factor

F_l=3710mm/5077mm=0.7307,

the round must also be crimped to

R= Master sail’s R x F_l =21.4cm x 0.7307= 15.6cm

The round of Panel 1 (from top) should then be around 3.9cm (1/4 of R) and
the round of panel 2 should be around 7.8cm (2/4 of R).

The round of panel 3 should be 9.3cm to give around 6% camber (just as you found).

Arne

PS: Note that the resulting camber depends a bit on how much you stretch the sail along the battens. With the sail quite slack, the camber will come out very close to the numbers in the table in Fig 4.5 of Chapter 4. If you stretch the sail to minimise wrinkles along the battens, the camber may drop from the planned 8%, down to 7%. Not a big deal.

Zane,

Thank you for your input, you make some very good points.

It was good to meet you over Easter and welcome to the junk rig community.

Pleased that you are now safely in Gulf Harbour and ready for more sea trials.

Regards

Rob