I am about to embark on constructing some new centreboards for the old Mozzie so that it can go faster (The old ones are big, long, heavy and I know that one is warped). The class restrictions are pretty basic which gives alot of scope to do whatever you want with length, width below the maximum limits provided.
I also hope to use the free fore/aft space in the cases to rake the boards backwards. Is there anyone who has experimented with length and width and what is the optimum for both ? The latest foils appear to be 10" wide and approx 1050 mm long. Has anyone used shorter lengths or widths to their advantage. How much can I play around with rake in the case without affecting centre of effort or if it does provide lee helm how much mast rake can be used without affecting downwind performance ? What timbers are best ?

Hi Peter
Be careful not to overlook rule 5.11 - "The leading and trailing edges of the centreboard slots shall be parallel and within 10degrees of the perpendicular from a straight line along the tops of the main and rear beams."
This means you can't pack the bottom of the case to allow the centreboards to pivot fore-and-aft. You can however achieve the same effect by tapering the top of the centreboards like this:

You will need to read a couple of places in the rules 8.1 through 8.4 along with 5.11. The way the South Australians measure the 10 Degrees angle is by putting the Center Board in the case and measuring the angle from the deck. This measuring method will stop you from doing what you propose unless the method of measuring changes. Center Boards are the place many people have played with and most have end up with what we are using now. I was sailing a Boga this year in light winds and with the kite up we could get the boat to sail sideways through the water to the point that sitting on the boat we could see it. The problem I can see with smaller boards is that in light winds they may not be enough. If you change the boards please keep us informed.

Peter

To Peter Cobden. Was it your Mozzie with the 8" centreboards at Loch Sport ?

Peter,
Not my boat, it has 11" centre boards. Most of the new boats we built have 10" centre boards. I know one person is using Jim Boyers new 9" A-Class boards and one other boat has Tony McKenzie 9" boards.
As for 8" boards I don't know who is using them.
Peter

Discovered that the leading edge rake angle on my Mossie is 5 degrees. This gives me another 5 degrees of rake that I didn't previously consider. Hope to make up some fibreglassed foam guides and install them in the case slot. This should provide the additional centreboard rake I'm looking for and give me some scope for raking the mast back. Those with older mossies should also check their case rake angles.

After much consternation finally bit the bullet and fitted the fibreglassed foam wedges 17/10, 18/10 and 20/10.

Saturday morning 22/10 9:00 am started cutting and fitting rubber strips to the fore and aft faces of the new slots. 11:00 am started cutting the aft sections off the existing centreboards with a hand saw. 12:10 pm applied Everdure primer to the exposed bare timber and set aside to dry. 1:00 pm had Mozzie on the beach for opening day race.

1st impressions: feels faster with slight lee helm. Will eventually adjust mast rake to suit. Now have to fill the gaping cavity at the leading edges left by the inserted wedges (not quite long enough). I have plenty of foam left over so will model some this week and glue it in place next Satuday morning and see if there is further improvement. Also need to feather the trailing edges of my modified centreboards.

Thought I should finally put this to rest. Revised centreboard cases and centreboards have made an enormous difference to boat speed and handling. Now have no vibrations from centreboards at high speed and reaching with centreboards fully down is a dream compared to the old design. Am now able to keep the other newer Mozzies honest even with the ancient sail that I keep persevering with. So to those of you with old Mozzies kicking around I would strongly advise the change.

Regards,

Peter Foulsum
p.s. Finished 2nd on Yardstick and 2nd on Handicap in club pre-christmas series. Maybe it was because others broke stuff capsized or didn't turn up.