Hi
Having trashed my rudder last year and the temporary repair now starting to fail i am in need of a replacement and am considering fabricating one myself from fribreglass.
I have a fixed rudder i was considering making a mould from the blade of that and then laminating two seperate halfs in glassfibre to form the blade with an alteration made to the rudder head to incoperate a pivot for fixing to a ceevee stock.
I am a little unsure how to fill/reinforce the core of the blade and the pivot point and was wondering if anyone has any experience in this and has some helpful advice or opinion to share please
Thanks

Foam or cedar cores are most common. There used to be a guide on the cherub website on making foils which should be equally applicable to merlins in all but shape.

As a thought - rather than make a mould where you have the problem of bogging the two halves together, rather make a core of foam or cedar for a one-off with carefully made templates. This is not as time-consuming as you might think given how soft and easily worked these lightweight cores are. Then lay e-glass or carbon over it with a slight excess of resin and fair back to the perfect shape. Carbon is obviously stronger but takes much more resin to wet out so you need to be rather careful to realise a significant weight saving. I've had two "professionally" made moulded rudders expire on me in a N12 and had to rebuild them with proper cores. Saving a kilo or so vs. having it let go when you most need, the choice is yours and it rather depends on what sort of sailing you are going to do. Good luck with it whichever way you go!

Thanks
Had looked at making the core and then laminating it but was concerned about gettig the profile right, thought moulding from a female mould of a tried and tested blade profile would save me some time/effort but aware this brings with it a new set of difficulties.
Cherub site has a very basic guide for making the core but again nothing for female moulding

I have made some rudders recently using ply. If you glue two sheets together on a flat base it elimanates any twist, you plane down to get the shape and the beauty is that the laminates in the ply let you see what is happening as you go and ensures the shape is good. A good random orbiat sander helps to get the final shape once you have got the basics with a plane. Finish with a sheath of glass/ epoxy and you have a very strong an fairly light foil for a fraction of the cost of buying.

Got a bit of experience with this, I had a centreboard for my Phantom cnc'd in polystyrene, then carbon coated, worked well and was remarkably light about 1 kg). Stiff enough for my weight when capsized. Did this through Phil's Foils in Canada - cheaper than UK suppliers, but not sure about the exhange rates now though. It was some time ago, so things might be dfferent now.

I am thinking about direct tooling (cnc'ing the mould), there are a couple of great looking foaming epoxy products on the market to fill the internal void. Good video on the Matrix Composites (Sicomin) site.

Buy one from JT out of his new CNC mould!