Due to depth issues at the lake i sail i'm looking to cut down a centreboard to a better depth for the lake.  Currently we're having to sail with about half board with a max of 3/4 board in sections, and this on occasion is causing issues with the balance of the boat as the centre of effort is in the wrong place in relation to the board.

The rudder depth seems fine and the 400s at the lake don't have an issue so i'm going to go with roughly that length, am i going to be ok to just chop the board and keep the same profile or would people recommend a slightly different shape?  I'm aware that the board won't be class legal for opens etc, which is why i've got an old board to cut and keep the one currently in the boat the correct length.

Any comments or thoughts would be much appreciated.

The cut down board will be legal as there is no rule for length.

Just weigh the off cut and adjust your correctors and your certificate ....

Dinghy foils are oversized for 95% of sailing time. If you've gone too small you're most likely to notice coming out of tacks. If the board stalls out then the boat will feel all soggy and will be making lots of leeway and refuse to accelerate. For some reason IME its more likely to be a problem in the light than in breeze. The better you are at maintaining speed through the tack the less likely it is to bite you.
Which end to cut off and what profile to give it is an interesting question. Assuming its an elliptical profile I think I'd be inclined to take half the required amount off each end and reprofile the tip to a blunter ellipse.

..I think Barry meant to say that there is no minimum length for a centreboard; there is of course a maximum..

GGGG

The no minimum board length is good, saves some smart alec protesting for a boat not in class rules...not that i think a protest committee would uphold the protest more that its hassle that can be avoided.

As for shape, i'm thinking of taking the area from the bottom, simply as it preserves the width and handle at the top meaning no extra work to add packing etc.  My only thought is that the foil has a straight leading edge and then a curve back up the trailing edge leaving the deepest point on the leading edge.  This is opposite as to how it was on my 400 where the deepest point on the foil was the trailing edge (or as far as i remember it was).  Anyway i digress am i best just straightening off the bottom edge to preserve surface area or would i be better maintaining the shape of the foil and following the same lines as the existing board?

Interesting post. I have an rather long centreboard on my old girl 908 and this too will cause problems where I sail so cutting down does seem to be the way forward.

I would suggest for lake sailing, to start with cut it off square as per Enterprise outline shape. This will give the best low speed side resistance especially for roll tacks etc. From here you can start to trim the board to a better shape once you know how she feels. Just remember it is easier to take material off than put it back on.

why not fit a rs400 board or one from another class and preserve the one you have for another day or when you come to sell .

Hi Matt,

Many years ago I had a N12 with a centreboard about 6 inches (old money) shorter than the maximum. The boat was (still is) very fast inland and tacks quickly, the only disadvantage is on the sea in a chop when we struggle a bit up-wind. I have made a few centreboards in the past. If you use ply and a power-plane its not that difficult as the ply lets you see the shape developing, if you overdo it you can fill it and re-shape, finish with epoxy and it will be stiff and quite strong but be careful in a cpasize as ply isn't as strong as solid hardwood or a carbon job. Good idea to keep the original "as-is" so you can go back to that if it's not a success.

In the 50s Brian Appleton who was very light sailed the first 'banana boat' 'Lucky' no. 177. He had a centreboard made that had the same underwater area as the original but was almost as wide below the boat as it was deep. I don't recall that he had to to alter the centreboard case. The reason was nothing to do with the depth of the water on the Thames, he was hoping that the boat would be easier to hold upright. He was 5th with Joe Niven in the 1955 Championship in a river boat that was considered unsuitable for Championship sailing.

http://www.merlinrocket.co.uk/gallery/view_photo.asp?folder=gallery/vintage&file=177.jpg

photo in the vintage gallery, although not of the centreboard

Matt I could weep.

I remember that board coming back from paintcraft wrapped in bubblewrap.

Hi Jon E, 

Just to set your mind at easer, the board that has been cut down isn't the one that came with the boat, its another one that i picked up from ebay.  To be honest i'm not 100% sure it was a full rocket blade as its about 4" shorter than the one that came in White Whale.  Hadn't realised how long the rocket centreboards are and the one in the boat is in very good nick.

Have cut it down now to around the same length as a 400 foil but have tried to keep as much of the area as possible, just putting on a slight curve to the leading edge to try to loose some of the weed that can plague Southport.

Thanks for all your help.

Oh it's Southport we're talking about - grim memories of trying to hoist spinnakers in a GP14 with a less than sober Guy Wood at the helm in the middle of the night and near pitch darkness and a pole with the fittings the wrong way up - Hampton 24hr challenge (challenged we were!)