Scarlattikvarten's History

Building 1985–6

First layer—3 mm thick plywood—of a deck.

Second layer—4 mm thick obeche veneer—being trimmed to fit.

Working on the outer layer of the deck. This is 1.5 mm mahogany veneer.

Staples and vacuum bagging to hold down the outer veneer while the epoxy cures. The vacuum is generated by a slaughtered vacuum cleaner. Hence not much vacuum but leak tolerant.

Molded deck with one coat of clear epoxy. It looks good but had we known how convenient strip-planking is we would never have gone for cold-molding. Malcolm Tennant's plans specifies strip-planking for decks and hulls. I don't remember why we opted for cold-molding.

Deck hatch coaming. We borrowed molds for this and the hatches from a friend who had built a 39' cat with rounded decks. The hulls radius was not the same so we cut away the flange of the coaming before bonding it to the deck.

Raw deck hatch on coaming.

Here one hull is starting to grow. The 8 mm thick cedar strips are glued to each other while being nailed to the frames. The glue was a home-made mix of epoxy and saw dust. The strips are just straight strips with square sides. The width varies to make it easier for them to follow the curvature of the frames.

Here is how far one gets in day one of building a hull shell: one side of the hull fully planked and the other side almost fully planked. The reason for the difference is the fact that the planks from side one must run beyond the centreline at the keel.

Day two has been spent on trimming down the excess planking of side one at the keel and adding the last planks of side two. Some hand planing and machine sanding also belongs to day two.

This picture shows final work of day three: glassing the outside of the hull shell. Since the glass is unidirectional there is no need for overlap along its sides. The wood fibres are the only load carriers in that direction anyway.

Sanding the inside of the hulls was both exceptionally noisy and dusty so after a few hours one felt a bit fuzzy.

Time for glassing the inside of the hull shell with the same type of unidirectional glass as was used on the outside. Just before this step the shells weighed 70–75 kg.

This photo shows the forward bunk meeting the forward bulkhead. All interior parts where pre-fabricated including all coating. Using measurements from the mold frames we could make all parts fit very accurately. Only minor trimming at the gunwales was needed. All parts were bonded to the hulls using home-made epoxy bog (epoxy + Q-cell micro balloons).

These two photos show the almost complete basic interior of a Spyder hull.

You may make out the UDWR glass used to spread loads at the rear beam attachment being laminated here.

Aligning hulls and cross beams.

Laminating UDWR glass for main beam sleeve.

Heavy UDWR glass to spread loads at dagger board sleeve exit.

Carbon pre-preg does not have looks like this.

Laminating a rudder.

Engine nacelle under construction. 4 mm plywood was used.

Afloat! Sailing is still about a week's worth of work away.

New crossbeams 1988–9

Cross sections of the new cross beams. The mast beam is 35 cm deep. Materials are 6–7 mm birch plywood oriented with the veneers at ±45° to maximize shear stiffness. Spruce stringers and some UDWR glass are used to improve bending characteristics. These materials were deemed best choice within my economical flight envelope at the time. Birch plywood and spruce was used for airplane construction and I am not surprised. You need very high quality glass fibre laminates to beat them. Today carbon would be a rather obvious alternative.
NB.Local reinforcements and other details are left out of the drawing.

Aft beam and mast beam under construction. Three sides in place and I am working on bulkheads and local reinforcements.

This is a bad shot of the reinforcements where the mast beam end interfaces with the hull. The underside of the beam and the hull sheer line are located at the very top of the photo. The task of the plywood patch is to transfer compression forces into the hull structure. The carbon does the opposite. Carbon replaced glass here after I had some issues in this area. Everywhere else glass has worked fine. I simply didn't use enough of it here.

Here is how the mast beam scarf works when we put the boat together in spring. Note that the mating cone is less than 1 dm deep.

The beam is in place but bolts are yet to be tightened. Note the glass that takes the load from the aluminium piece and spreads it over a large area of the beam.

The aft beam is bolted down in a more conventional manner. These threaded (M12) studs are 'only' bonded to the wood using over-sized holes penetrating almost 20 cm into the wood reinforcement. Unidirectional glass is wrapped over the wood reinforcement on each side of each stud and spread out down the in- and outside of the hull.

Vacuum bagging unidirectional carbon to mast beam after having removed dolphin striker in 2004.

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