Week 18 - Rudder / Centreboard

Both the rudder and the centreboard were fashioned in a similar way.
I decided to build them out of a 6mm core of 316 stainless steel and glue marineplywood on each side of it. This results in a very strong sandwich which resists undesired contact with  the ground or other things that could affect damage.

The first photos show the rudder with the 6mm steelplate welded on a 1" stock.
I changed both designs a little bit compared to the original drawings. The rudder to keep it lower for a free view on the transom and the centreboard because of the changed centreboardcase relating to the benchbridge and the cabindesign.

The marine plywood was glued on the steelplate with thickened epoxy (with colloidial silica) after a prudent surfaceclean and sanding. Then I shaped a profile with the target of getting a smooth transition from the deadwood of the woodkeel to the rudderend. For that reason the rudderblade became quite fat in it's dimensions! But later when seeing it fastened on the boat it will be balanced proportions I promise.

The final profileshape of the rudder is visible on the photo to the left.
You can also see the centreboard ready for sheeting with fibreglasscloth and epoxy. In both cases we used a plain weave and not biaxial cloth as on the hull.

When sheating the first side we pulled the glasscloth over the edge and cut it after the epoxy got "green" (depending on the temperature about 2 hours after mixing).
Then we laminated the other side in the same way which results in an overlapp at the edges.

Back to the rudder... thank's to the fact that the rudderblade was welded on a stock we could clamp the whole thing in a vice which allowed to sheat both sides at the same time.
Beside that the photo also shows the different veneerlayers of the plywood which were shaped to a profile and therefore got that special pattern.

The glasscloth could be pulled around the rudderstock and along the outlineedge we made a lot of small cuts with a scissor to make it easier to get the weave molded around the rounded edge.
The pictures don't show the process of spreading a coat of thickened epoxy with added glassbubbles after about 1 1/2 hours over the whole surface. This will be an easy to sand surface to later get rudder and the centreboard nice and fair.

On the right side you can see the finished centreboard just before getting fitted on the boat. The whole surface has got 2 coats of antifoul.
At the pivotingpoint we glued a stainless steel bush in and on the topside there is a hole in the corematerial which formes an eye. This is the point where the shackle of the pulley-block is attached. This arrangement allowes a comfortable control from the cockpit.

Some chiselwork had to be done for fitting the rudderheel at the aft end of the woodkeel.
The fitting is an own design and is welded together out of 5mm 316 stainless steel.
The flange of the rudderstock is gliding on the visible nylonbush which has got a drainhole on the bottom.

Finally we got the rudderstock in and skrewed the fitting fast.
But before screwing we sealed the whole bare wood with epoxy and also covered the whole contactsurface with butyl mastic.
Well... that should be really rigid!