longer boom for ocean 47

[blue-max]

This idea germinated when I wanted to arrange a fixed cockpit canopy - some what like found on catamarans ( which could support solar panels and catch rainwater) but because the boom ends before the end of the cockpit the main sheet cuts across the cockpit - and any canopy - when it is payed out. Also I have read that this model is under canvased and the main seems too small at 39 m2 which is why light wind sailing performance is not great. I need a new mainsail in any case so this seems a good time to change the boom.
Any views about fitting a longer boom maybe from a cruiser / vision 50 and where to find a used one?

[Symphony]

Chance of finding a second hand boom are pretty slim - not the sort of thing that people throw away! It is a standard Selden section, so a Selden dealer, some of whom are also sailmakers such as Kemps or Crusader would be a good starting point.

[Craig]

A longer boom and a greater sail area as a result will do a number of things.

1. Change the aspect ratio of the sail. ( wider compared with height). This may not give any improvement in up-wind performance and only increase down-wind performance slightly.
2. The centre of effort in the sails will be moved aft. This will increase the tendency to round up. Most Bavarias seem to round up before broaching so this would increase this issue.
3. When sailing down wind in rolly conditions the end of the boom will hit the water. This can happen with standard rigs, so a longer boom will increase this tendency. The force of hitting the water is likely to break the boom, particularly if you have a preventer on.
4. Forces on gooseneck will be increased.

The approach used by a number of boat builders is to build a Targa bar over the cockpit and put the traveller and main on that. This also gives a more solid support for solar panels etc.  Previous boats I have owned had Boom Tents for use while at anchor. They were always a pain to use as the boom had to be kept still and had to be taken down every time I wanted to sail. They are useless in strong winds.

If you go the Targa bar approach, Turkey is the place to get the work done. A friend with a Bav 46 had once fitted in Marmaris but used it for supporting the solar panels and for dinghy davits. The cockpit was fully enclosed and gave great living space, particularly in winter. Their main was attached to the traveller in front of the cockpit.

Craig
"Shirley Valentine"
Gold Coast
AUSTRALIA

[blue-max]

Craig,
Thanks for your comments. I am considering a targa bar but as a centre cockpit it will be smaller than the typical stern mounted arches one sees. I am wondering about the risk of dipping the boom, the possibility had not occurred to me, but I do think the sail plan for this model is quite small. I have tried without success to compare the sail plan with the 47 of the same period as both models share the same hull.

[Symphony]

Think you will find the Ocean 47 hull is unique to that model. The sail area is 90 sqm and SA/Disp is 17.5. The nearest in the cruiser range of the time was the 46 which has the same WL length and beam but significantly less ballast (30% ratio) which also has 90 sqm and a higher SA/Disp of 20.

The Ocean hulls were deeper and had greater ballast (38% for your boat) reflecting their target market. So, in comparison with the cruiser models which were aimed more at the Med charter market the Ocean could be described as undercanvased - but not if you compared with other similar centre cockpit boats aimed at the long distance cruising market such as the Moody 46 (15) and Oyster 485 (14).

[blue-max]

Hello symphony,
Maybe I am mistaken but I have seen a B47 which was a similar age and appeared to have the same hull - it was at the same boatyard and is now offered for sale by sunbird in marmaris. However as you say its a heavy displacement design so should be feasible to take a bigger sail area albeit needing to reef a little earlier

[Symphony]

You can, of course increase the sail area by lengthening the boom, but you run the risk of upsetting the balance of the boat and increasing weather helm because you are adding area aft. So you may need to actually reef earlier to bring the sail area forward to reduce weather helm.