Jefa GRP rudder blade production
Jefa Marine produces a wide range of standard rudder blades for boats from 22 to 75 feet length. This unique product line offers the boat builder a modern rudder blade without investing in expensive molds. The rudders are made in our modern GRP factory and are available in many sizes depending on the boat size. What makes the Jefa rudder blades unique and distinct from all other rudder blade producers and yard made rudder blades is the production in solid aluminium molds. This unique production method allows very high pressures to be used in the gluing and foaming process and results in an extremely precise end shape. Traditional glass fiber molds don’t allow any pressure from inside the blade, so one can’t be sure of a good bonding of both sides and the final shape of the rudder.
Another unique feature is the overlapping parts of the blades. This feature substantially strengthens the blade integrity making it nearly impossible to split. Traditionally the rudder halves are glued heads on together, allowing only a very small contact area which causes the blade to split easily.
The cross section shown in the picture at the right side perfectly shows all advantages of our unique production method. Due to the high pressure foam filling system, the foam is guaranteed present in all remote ends of the blade so no air pockets can be present. Also well visible is the large overlap at the front and the huge glue contact area at the aft side of the rudder blade.
The left illustration shows the way the Jefa rudder blades are build. The blades are made of one layer of 300g chopped E-glass and 3 layers of 600g. The metal (Aluminium or Stainless Steel – for details see this web page) rudder stock is MIG welded to the spokes which are glued to the rudder blade at each side. On top of that there is extra lamination at one side of 2 layers 600g glass. This extra laminate is very important as any movement between the rudder stock and rudder blade is fatal for the lifetime of the rudder. All rudder blades comply to the ISO 12215-8 norm ( the CE regulations). Please look further on the page for more detailed information on sizes, production methods and specials. All Jefa rudders are delivered in a gel coat finish and should be treated with non-water penetrable epoxy coating and anti-fouled. This will prevent water entering in the gel coat and underlying GRP structure. For detailed instructions, please open this PDF instruction leaflet.
Video showing the rudder blade production:
The manufacturing process of the rudder blades:
Jefa rudder blades are very stiff, strong and durable as they are made in a solid aluminium mold and foam filled under pressure. The production process will be explained in the below sequence.
All rudder molds are produced out of a solid piece of aluminium in our machine shop. Custom molds can be made to suit a specific rudder blade design.
All molds are high gloss polished to achieve the best possible blade surface.
The mold is carefully cleaned and the edges are taped and covered in plastic.
Both mold halves are polished with mold release wax.
The molds are hand painted two times with gel coat, with a ½ hour interval.
Sharp corners on top and bottom are filled with polyester glue, radius 10-12mm.
One layer of 300g powder bonded mat, with polyester resin is added.
4 layers of 600g emulsion bonded mat, with polyester resin.
The mold is cut clean, the extra laminate at the top and front is for a better connection between the two blade halves.
The rudder stock is carefully positioned in the mold.
The rudder stock is carefully positioned in the mold.
Polyester glue is added on all contact places.
The rudder stock is carefully glued to the blade.
2 layers of 600g is added on each spoke for extra connection.
The edges are glued with polyester glue.
The spokes are glued to both blades and laminated to one side.
The form is filled with PU foam. This foam will dramatically expand in size and completely fill up any free space in the blade. Within 90 seconds the molds have to be closed, otherwise this set is a loss.
Just before closing.
Finally both parts meet and are secured as the pressure runs up high due to the expansion of the foam.
A vent hole in the mold assures any air is pushed out so the foam is completely spread in the blade.
After a few hours rest, the mold parts are separated and the blade edges can be finished by hand.
The shaft entrance in the blade is sealed with Sicaflex 221
The finished rudder.
A destructive test clearly shows the overlap and foam filling.
The unique production process in metal molds and high pressure foam guarantees a complete filling of the blade.
The cut of the bottom of the blade. The large overlaps are clearly visible and will ensure the blade parts will never separate.
Rudders not transported by ourselves are individually packet in carton boxes and grouped on pallets.
For shipping large quantities of rudders to yards, a special pallet that can take up to 20 rudders has been developed.
Modifications to the standard rudders:
Via inserts in the mold, it’s possible to modify the rudder blade shape. Inserts can be made for the bottom and the top of the blade.
RUD30 rudder blade with a modification in the bottom and in the top.
The complete finished RUD30 blade with modifications.
Detail of the modified bottom of the blade.
RUD30 rudder blade with a modification in the top for a production boat builder.
The aluminium insert in the RUD30 mold.
The ready rudder blade RUD30 with special top.
Detail of the special top side.