New dagger board.

[trebor]

Hi all, I have snapped my Plywood dagger board in half (inverted in strong winds, gybing, tried to rock it back up to avoid an assist), does it need to be marine ply? due to the thickness of board about 3 eights of an inch thick, it is about 3 feet long and a foot wide. I would like to use wood if possible, if a piece of wood would be stronger, what type?

[phil58490]

I think your easiest option may be to use a dagger board from something like a Laser if it could be made to fit. If you want to make one, I'm guessing at the size, but a board from something like an Enterprise or GP14 could be cut down and reshaped. I've bought two laminated timber boards recently off ebay, both cost less than the timber I bought to make a Solo centre board. Just had a quick look but there is nothing suitable on there at the moment. I think laminated would be stronger than plywood as timber has its greatest strength along the grain and very little across it.

If you want to play in the workshop, have a go at vacuum bagging the board blank with epoxy resin and fiberglass, lots of sites on the web telling you how its done. I have made a Solo centreboard and rudder like that and I am very please with the results. (Thanks ED for the inspiration, it was time consuming but relatively easy).

[trebor]

Hi Phil, I have tried a Topper dagger board and a Minisail, but both are way to thick, the slot is only 15mm wide you would have to remove loads of material from sides to go in, the dagger board is literally a piece of ply round at the bottom, no shape to edges with a slotted top handle, the nearest to it is off a Polycell boat, what wood is most suitable?

[Rupert]

The advantage of solid wood is that all the grain is running lengthwise, so it is less likely to snap. If you laminate different types of wood together, so it ends up stripy, then it limits the chance of it warping. Western Red Cedar and some sort of straight grained dark wood put together will work. It really is very thin - I had the same trouble with the wooden MS - that was about 16mm. I happened to get given an old Albacore board, so used that, but had to plane it down with a power planer a huge amount. Would be easier to start from scratch. Get it glued, then run it through a planer-thicknesser, if you can find someone who doesn't mind a glue joint going through.

[trebor]

Hi Rupert, This sounds similar to a Mirror Dagger board that is at club, looks very nice, this would add a touch of age to boat.
This is 3rd Saturday on the trot I have broken something, last saturday I ran aground at speed and broke rudder, saturday before dagger board again, pulled it staight out of bottom of boat, capsized 3 times in strong wind, practicing releasing sail, the handle and bungee left other side, very difficult righting boat with no board.

[Ed]

For thin boards, or down to that thickness 15-18mm, I just don't see how you are going to be able to make anything that is really strong or in any way stiff.

Yes, a solid or laminated board will be better than a ply one....but still most of the strength needs to be in the skins rather than the insides.

I would just get a bit of good quality ply at a couple of mm thinner and then cover with enough glass or carbon to give some hope of rigidity.

Carbon would be better and there is some cheap carbon about on ebay at moment. carbon uni even better. Failing that then some 300g bi-ax glass.

But just don't be scared of doing this, it isn't hard....or that expensive.

If you wanted to be really strong, you could add one or two carbon webs running longitutionaly between the skins. I say strong....it still might not be that stiff.

cheers

eib

[trebor]

Hi ed, The existing board is 9.5mm thick, approx 18" sticks out of hull fully down, I have got a piece of ply 12.5mm thick, I will make a quick board this week ready for Saturday, then try to make something stronger with more time to spend on it, I like the look of the laminated Mirror board. I will glue one together and see how strong it is.
The boat is in excess of 30 years old, I have had it 2 years and now I am really sailing boat hard and getting placed, the board only broke due to abuse. I would have won this race by a mile, the buoy I capsized round was second to last. so a normal capsize would not have cost win, just unfortunate to invert.