The hull - finishing touches

I managed to finish working on the stem and I replaced all the temporary fasteners except along the sheer since there will be some beveling going on there to fit the cabin top and deck and I don't want to destroy my tools on steel fasteners buried in the plating somewhere. For the rest: all the stainless fasteners (5x30mm on the chines, 5x35mm on the frames, 5x50mm in the stem and transom, 4.5x30mm along the stringers) are bedded with epoxy, countersunk and the holes filled with fairing compound. Tomorrow I'll sand the fairing compound down and see if any more is needed in preparation for glassing - I'll try to make the surface under the glass as fair as practical since the glass will have to be faired as well.

The trennels I used to replace the temporary fasteners in the stem are quite long as they are tying all the layers together and also bite into the deadwood. The key to success is making sure the glue fully fills the hole and encapsulates the dowel. I drilled 9mm holes for 8mm dowels and filled the holes "from the bottom up" about half way using a syringe and a piece of tube. The under sized dowel then squeezes the glue out along it's sides and voila, no air pockets (to speak of).

Don't have too many photos (working solo with epoxy, no time to shoot), here's the few I do have.

 

I tried to remove some of the stainless screws I used for keeping the turn of the bilge in place to better bed them with epoxy - turns out they were already pretty much glued, despite heating them up first with a soldering iron I still managed to twist off a head or two. I just left those in place, they will be plenty strong.

 ...and here's the hull in various stages of being treated with the fairing compound.

The sanding and final touches tomorrow or so if time allows.
cheers.

The stem cover

The stem in the Design requires an additional plate to tie it together. From what I have seen in others' blogs (including the Designer's) a 3cm plank suffices. BUT. The bow is then just held together by 6cm of wood with the grain running vertically and therefore, theoretically, could split/check. The Design does not call for any other reinforcements (aside from maybe some glass to cover the joint), no wooden crooks, not even steel bolts. I did  consider the latter, but for this size boat it probably is overkill, especially since I'm not aware of any setkas developing a problem at the stem.
For my own peace of mind I decided to reinforce it by laminating some maritime pine with grain running perpendicularly to the stem between the 2 parts of my Douglas fir stem. It does make my boat about 2cm longer than in the Design, but with a little bit of luck nobody will notice ;).

For gluing I used the last of my polish Epidian 5 + PAC combination with a little bit extra hardener (100:70 ratio as I did on the bottom plating) to make the glue a little bit more elastic and impact resistant.  All according to the manufacturer's specification. The cured resin is noticeably less brittle, but still much tougher than wood. Clamping force (not too much) was provided by wood screws and clamps.

The next day I removed the screws (with the help of an old soldering iron, they were properly glued in place). There is only about 3cm of douglas fir they can grab on to, not much point in trying to rely on them as reinforcement. In the leftover holes I will glue in oak trennels.

Also: I trimmed the stem and roughed out the outline of the cutwater. The hull is now close to it's final shape.

Next steps: replace all temporary fasteners with proper ones, fill and fair all the imperfections to prepare for glassing. Which I may or may not do next. But maybe I will first turn the hull upright and do the interior and deck first. We will see.

The bottom line

Plating the bottom. I started by cutting some limber holes, just along the bottom chines. I left the forward bulkhead without, the space there will be completely water tight.

The limber holes are glassed to protect the end grain:

 

Also, some minor defects are filled, no reason for them to collect dust and moisture.

For the plating itself I decided I want to try to scarf join the plates instead of using butt joints like on the sides. There will be 2 layers of plating so the scarfs will complement each other and make for a nice and flat bilge. I cut the scarfs by hand on 2 plates simultaneously in order to get the angles right. The scarf ratio is 10. Gougeon bros recommend 8 for epoxy joints, some poeple say 12, I went with 10.

As always, all mating surfaces are pre-wetted:

Then the plate goes on (with a squiggly line of thickened epoxy inside the joint) and is screwed tight using 3.5mm self drilling steel wood screws. Those will be replaced with 5mm stainless screws.

The loose scarf gets some additional clamping:

The scarf joint if screwed between a piece of scrap plywood (to force it to follow the bottom line) and a plank from below (don't have any pictures though, it is kinda hard to try to get everything done before the epoxy gels AND take pictures with all glued up hands...)

First layer done. Was not too hard, although it was stressful and kinda fiddly and time consuming.

The joint came out perfect, with some squeeze out on both sides; curving where it needs to curve.

After some trimming the temporary fasteners were replaced with the larger stainless screws. 30mm long along the chines, 35mm along the frames and 50mm at the transom. I filled the holes with slightly thickened epoxy to improve holding power - the wood surrounding the fastener becomes tougher and should make the bond stronger (to be tested). Just an extra precaution since I am using quite soft wood. I would not have done this in oak or ash for example.

The second layer went on in a similar fashion, first I prepared the plates and scarfed them.

I troweled slightly thickened epoxy on the first layer without pre-wetting the surfaces. Should the bond be slightly worse the large surface area will make up for it. I used 20mm fasteners to provide some clamping force (the bottom is relatively flat so not much force is needed). The scarfs are clamped using some scraps of plywood screwed to the plates on both sides of the joint to force them into shape.

After it all cured I trimmed the overhangs almost to where I want them. I will leave the final shaping/sanding for later when I'm ready to glass the hull.

The joints look quite ok:

It did took quite some hours of work but the final result does, finally, look like a boat:

Next step will be attaching the stem cover plate, replacing the rest of the temporary fasteners in the hull, filling and fairing the screws and holes and, finally, turning the hull to start working on the interior and the deck. I want to do the interior first, before installing the deck, otherwise it might get a bit cramped in there.

Tot de volgende keer.

Turn of the bilge - done. The story of a bitter victory.

Bending plywood proved to be a challenge. Maybe it's just the plywood/stringer material I'm using, but the results are not quite as good as I was going for. To cut to the chase: plywood does not like to be bent and is trying to go straight again exerting quite some forces on the skeleton. So if that is not stiff enough the water lines turn out not as smooth and fair as intended. This specific design does not seem to have enough stiffness, at least the way I'm doing it:) (maybe that is the problem). In hindsight I wish I had made an additional station between frames D and E (first and second counting from the stem). Also maybe an additional stringer or two. The deviations from the hull form lines are not very large, but noticeable, I'm not worried, it's all still structurally sound and hydrodynamically it will also not matter - not at the speeds a 5m sailboat is capable of. It's also very unlikely anyone but me will ever notice:) So enough yammering, on with the pictures:

Installing the bow section went fine as it was already pre-bent as described earlier. Installing the section directly aft of it was tricky due to the curvature at the front side and the length of the panel. I started at the bow, fastening one corner with a temporary bolt. This made bending the panel into place easier:

I used bolts also to force the butt blocks into shape, went with 8mm plywood, the 10mm was impossible to bend in such small pieces. I will reinforce the joint with extra glass on both sides.

While the epoxy it still malleable I clean up the squeeze out and make fillets on the inside. 

Trimming is quite easy:

No plywood is perfect:

Below, the subtle flaws in the curvature along the water lines are visible. I may have minimised this by choosing to join panels closer to the frame, but the effect would still be there. Just in between the stations, where nothing rigid supports the stringers the plywood tries to flatten itself out. It both pulls the unsupported bottom chine to the outside and the middle stringer to the inside.

Other things I could have done: install the bottom plating first. Would have prevented the bottom chine from developing the complication. But would have made installing the bilge plating way tougher. I could have gone the way most setka builders go: make it all flatter, avoid the large compound curvatures, would have helped some. I could have installed a (half-) frame and additional stringers. Next time maybe:)

Checking the global geometry shows all is well in terms of symmetry, straigntness and trueness of the hull:

On to installing the bottom now.
tot ziens.