Rudder - Fitting the foam

Torkil made a great job shaping the foam, and we decided to go on with hand shaping on the next rudders as well (we are building three, one for each and a common spare).  Unfortunately, I forgot to take pictures during the process today as well.  After fine trimming the foam, cut outs were made to accommodate the high density inserts and the central core.
To make sure the two halves will not move around in the moulds during the next few steps, we attached the skins to the mould using a spray glue.  Then the foam was coated with a low viscosity epoxy while a substantial coat of micro fibre thickened epoxy was applied in the skins to make sure all possible unevenness in the foam blanks are filled.

High density insert being wetted out and put in place

The chord of the foam was cut back a bit as well, and the trailing edge filled with the same micro fibre/epoxy mix.  A central core blank wrapped in several layers of thick building plastic and peel ply were placed in the central core groove of each half, ensuring correct spacing.

Then the two moulds were brought back in the bag to cure under vacuum.

Starboard front beam exterior

I got the other front beam exterior laminated tonight.  Curing with slot "inserts" as I did with the other side.

After "de moulding":

Rudder - preparations for the next step

Torkil is working on the foam blanks, shaping them using templates from the full size patterns.

As one of the important properties of epoxy is the ability to adhere strongly to other surfaces, I was getting anxious about de-moulding the skins if waiting too long, so I de-moulded this afternoon.  The downside is of course that we now probably must use a little spray glue or something to make sure the pieces do not move in the mould during the next steps.  I probably should not have worried as the skins let go of the mould without much trouble, and left the moulds in perfect condition.  The surface was better than expected, very close to perfect.  I cut the skins roughly with a scissors and put them together to get an idea, and if there is any truth in the saying that if it looks right it is right, this will be a hell of a rudder!  No way to capture the impression in a photo, but anyway:

Then I made the HD inserts, shaping them to the inside of the skins but leaving them high as the whole thing will be routed back to the centreline as soon as the foam is attached.  I also made the core for the central "strong box".

Then I made this jig for the router:

Torkil will return with the foam blanks Monday night.  Check back for the rest of the story...;-)

Rudder - making the skin

As it is still really uncertain when the CNCed foam blanks will be ready, we (Torkil, who is upgrading his C24 rudder, and I) decided to start building and hand shape the foam.  As we plan to vacuum laminate the foam to the skin, an accurate shaping will not be necessary, just almost will do.  Unfortunately, I forgot to take any photos during yesterdays session.
First, we polished the waxed moulds and applied two coats of Norslipp. Then added tape to the edge where an external carbon tape will go after joining.  If I thought of it in time, this should have been added to the mould.  Wet lay up of the two skins and unidirectional reinforcements and then we put it under vacuum.  I unbagged today and it looks very good.  The next steps will be to glue the foam in, routing down to the centreline and join the two pieces as the centre box is added.

Forward beam mount - external lamination

I had the lower part of all beam mounts laminated when the hull was up side down.  I laminated the upper part of the port forward beam mount, covering the compression pad area and overlapping inside the upper folding strut slot.  After peel plying the whole area, I pressed pieces of foam scrap covered in vacuum bag in to the slot to make sure the overlapping part is firmly pressed against the mount.  After curing this was removed and revealed a very satisfying result.

Coamings - external lamination

Two days ago I finally found time for external lamination of the coamings.  First I had to fair the foam, and as it was already laminated on the inside, the construction was relatively stiff and easy to work on.  Some filling was required and this was done just prior to lamination.

The laminated cockpit.  Aft part of coamings still to make.  These will feature beverage holders and the engine controls.

And for the first time it is possible to see the final profile of the boat.  I'm happy.

Coamings. A guide to making glueing flanges

The foam moulds was easy to remove, and the flange turned out pretty good.  The second I made was better looking than the first one.

I trimmed the starboard side:

The method for making flanges introduced by Menno is so fast and easy, that I will describe it in more detail.  I use foam used for insulating concrete when building, called isopor.  It's light and easily accessible and quite cheap.  It is very easy to cut with a saw and very easy to sand, but it makes a mess.
First I cut a roughly sized piece of the foam and place it using a clamp.  Then the profile is cut with a saw.

Then it is removed and sanded and covered with plastic packing tape as a releasable surface. All corner where the fabric is going are well rounded.   A couple of minutes later it is ready for checking the fit:

I laminate the flange on the foam mould:

Put it in place, keeping it with clamps.

Add peel ply for easy secondary bonding.

When the tops goes on, the grooves from the rounded edges are filled with a mixture of epoxy, chopped cotton and silica. This picture showing the port side coaming.

The added 600 gsm pad under the possible winch position.

Coaming top being glued on, using screws and 20 kg of epoxy to keep it pressed against the flanges.

I also taped the seat to seat front corner on starboard side.