Having taken a few months off from building, its time to start a new build before the weather improves and the grass needs cutting.

I currently have two yachts, a Wee Nip and Ellen, a Gaff rigged Pilot Cutter. I sail the Wee Nip most weeks, and the Pilot Cutter occasionally when the weather is suitable (it needs a 'good blow'). I decided to build something between the two in terms of size. A bit of on-line research came up with the Racing Sparrow. A design by New Zealander Bryn Heveldt. I bought a second hand copy of his book, which includes a full size plan. There is also a website where copies of the plan can be downloaded for free.

https://racingsparrow.co.nz/

The cost of the book was less than the cost of getting the free on-line plans printed at a print shop. I have downloaded the free plan so that I can print parts of the plan on A4 sheets to use as templates. I soon found that there are differences between the plan included in the book, and the on-line plan both in terms of the hull shape, and the overall scale of the plan.

I chose this design because it is a size I hope will be easy to transport, it is plank on frame construction using balsa which I haven't tackled before, and it looks good!

The book includes step by step instructions for the complete build, including details of the materials and tools required. Good for a complete novice to boat building, although there are some strange anomalies when it comes to metric and imperial dimensions. For example 1/8th of an inch is converted to 4mm while 1/16th is converted to 1mm!

First task is to start accumulating bits and pieces, and to order the balsa.

Using the electronic copy of the plan, individual paper templates were printed for each bulkhead. These had to be printed at an enlarged scale of 107% to match the size of the printed plan which came with the book. A slight curve was added to the top of each bulkhead to give some shape to the deck when it is eventually glued on.

A building board was prepared using a length of salvaged veneered chipboard panel (I'll be running out of this soon 🤔). The centreline of the hull and the location of each bulkhead were marked out on masking tape.

The bulkhead templates were glued to 5mm thick balsa and cut out using the fretsaw. I bought the fretsaw secondhand a few years ago and it proved to be so useful when building models.

Plywood supports for the bulkheads were also cut using the fretsaw. They vary in height along the hull length to provide a concave shape to the deck (I think there is a nautical term for this, but can't remember what it is!) The balsa bulkheads were glued to the ply supports while lying flat on the workbench using hot melt glue. Once set, the composite bulkheads/supports were glued to the building board, again using hot melt glue. As you can see, holes have been cut in some of the bulkheads, both to save weight and to provide internal access to the whole length of the hull for running wires and sheets.

Finally the keel box and a few other supports were glued between the bulkheads in accordance with the plan.

Before starting the planking, a chamfer was sanded on the edge of each bulkhead using a long sanding stick which spanned adjacent bulkheads. As the structure was flimsy at this stage care had to be taken to support the bulkheads while sanding.

The plan calls for the hull to be planked with 1 x 4 mm balsa strips. I suspect the suggested 1mm thickness may be another imperial/metric conversion issue as it seems very thin. I decided to us 1.6mm (1/16") balsa.

An adjustable strip cutter was first constructed from a few bits of wood and a utility knife blade. This made converting the balsa sheets into 4mm wide strips a simple task.

The plywood bulkhead supports are wider than the bulkheads. This made fitting the first strips at the gunwhale very simple as they were simply rested onto the plywood supports and glued/pinned to the bulkheads. Two strips where added along the keel, and a further two added one each side half way between the keel and gunwhales. Care was taken when adding these strips to ensure that the bulkheads remained vertical. The length of the hull means that no joints are needed in the strips.

With the basic framework in place, it was then simply a task of adding more strips alternating from side to side. The thin narrow strips are easy to flex and twist into position ensuring that they align closely with the previous strip.

Continued with the planking, adding planks alternately to each side. It didn't take very long to do as balsa is quick to cut and fit.

The clearance under the hull provided by the plywood supports was very useful as it allowed enough room to slip fingers in to support the planks from behind.

Once all the planks were in place, initial sanding was carried out. In a few places, the edges of the planks didn't fully align leaving a step between adjacent planks. I didn't want to sand too much off so short offcuts of planking were added to fill the step, and then these were sanded smooth.

With the hull sanded smooth, a layer of glassfibre cloth was applied with two coats of epoxy resin. This to strengthen and seal the outside.

I've never been a big fan of hot melt glue but I did use it to attach the bulkheads to the building board before planking commenced. Now using a hot air gun I softened the glue to release the hull. This worked really well, so at last I've found an application where hot melt glue comes into it's own - the ability to remelt it and release the hull.

The hull feels very delicate despite the glass and epoxy coating. I hope it will be more robust once the internal fittings and deck are in place. The weight of the hull at this stage is just 150 gms.

The stern has an angled transom which was cut/sanded to shape and then glued in place.

When fitting out the test of the hull, great care was taken to ensure that all the parts to be added were the correct length so that no stress was put on the hull which might cause it to twist out of shape.

A length of M6 threaded rod has been used for the maststep. This is glued and screwed into the supporting balsa block. A thin sheet of aluminium was threaded M6 and added to the maststep (photo 3) to spread the load. Just forward of the maststep a fairlead is fitted to carry the sheet which will control the jib sail. The fairlead is made from copper tube with both ends faired out.

The receiver was tried in position and two lengths of sleeving fitted for the aerial leads to thread into.

The rudder servo is fitted as shown in the plan. This connects to a brass horn on the rudder post using a length of bicycle spoke.

The plan suggests using a long arm servo for sail control but I have had bad experience with long arms and prefer to use a sail winch. A suitable winch was sourced and mounted into position. A mounting box for the battery was also put together so that it isn't left to rattle about in the bottom of the hull.

The plan also suggests that both the main sheet and the jib sheet should run through a single fairlead in the deck, the jib sheet then being routed forward across the deck before attaching to the jib boom. This routing has to be either round, or over the hatch neither of which options seem like a good idea. I opted to run the jib sheet below the deck, bringing it up through a second fairlead to just below the jib boom. To help with this below deck routing, a ceramic ring was fitted to one of the bulkheads. These rings are readily available from fishing tackle suppliers as replacement parts for fishing rods. With everything in place, a check was made that the sheets can be routed without any snags.

Finally, the support members for the two hatches were fitted. I've opted to make the hatches as small as possible, consistent with being able to fit and remove all the radio gear. This to help keep the inside of the hull dry. The picture shows the hatch size on the plans in blue and the size I have opted for in red. Hope I haven't made them too small 🤞

Before fitting the deck, the inside of the hull was given a coat of epoxy resin. This was warmed in a waterbath before application to make it easier to apply in the restricted spaces within the hull.

The deck is made up from two sheets of 1.6mm balsa. These were simply cut to size and glued in place with plenty of pins. The balsa was thin and flexible enough to follow the shape of the deck supports without the need for any contouring.

Once the glue had set, the deck was given a layer of fibreglass and two coats of epoxy resin.

The keel comprises an aluminium strip clad with balsa and a lead bulb weighing 1.3kgs.

The 3/4" x 1/8" aluminium strip was prepared by cutting to length and then adding holes/notches at each end to help with gluing in place. The balsa cladding was made up as a tube from 4 pieces of balsa glued together. Once the glue was dry, the cladding was sanded to an aerodynamic shape.

The plans suggest making a plaster mould from a wooden master to cast the lead bulb. The master was constructed from three pieces of wood glued together and shaped to the required profile. The central piece had a slot cut in it for the aluminium keel. I was not convinced about being able to produce a plaster mould which would include a negative of this slot. I didn't have any plaster of paris available, but I do have a large bag of builder's finishing plaster left over from some house renovation so decided to use that instead. The wooden master plug was suspended in a cardboard box and plaster was poured in to halfway up the plug. After a week, the plaster had still not set! It had simply dried to a mud like consistency.🤔 On to plan B I decided to use the technique previously used on the Gaff Rigged Cutter.

A series of graduated holes were cut into pieces of plywood which were then glued/screwed together to form a mould. The aluminium keel was clamped in place and 1.6kgs of molten lead poured in. After a couple of hours, the rough casting was released from the mould and carved to shape using a craft knife and surform tool.

Finally a jig was constructed to hold the keel over the inverted hull with the end inserted into the keel box. It was then glued in place with a mix of epoxy resin and chopped fibreglass and left for several days to set hard.

With the keel in place, time to start painting.

The underside of the hull and the keel have been given several coats of grey etch primer from a rattle can. Each coat was sanded and any irregularities filled with knifing putty. After three coats, its looking nice and smooth.

With the keel fitted, the hull no linger fits in the temporary stand so attention turned to making a proper stand. An internet search came up with drawings for a stand for the IOM yacht

http://nmsclub.org/files/documents/IOM-Boat-Stand.pdf

The drawing was scaled down to a suitable size and then the stand was constructed from scraps of timber found in the workshop.

With the hull supported on its new stand, plywood lippings were added to both hatch openings. Once glued in place, two layers of masking tape were added around the lipping and the plywood sides for the hatch lids were then glued together while clamped in place. The tape ensures that the hatches will fit accurately and allows for the thickness of the paint which is still to be applied. Two layers of 1.5mm balsa form the top of the hatches

With the hatches complete, the deck was also given several coats of grey primer. The stand was also painted with 'quick drying woodstain'.

The hull has been painted with several coats of 'Appliance white' from a rattle can, rubbing down carefully between coats with 1200 grit wet and dry, used wet.

There is a 'Racing Sparrow' logo available to download from the website: https://racingsparrow.co.nz/free-model-boat-plans/
This was edited using graphics software to produce a pair of handed logos, suitable for use on either side of the hull. The blue of the logo was adjusted to match the colour of a pinstripe tape I bought on-line.

The two logos were printed onto clear inkjet decal paper following the instructions which came with it. Once these had been lacquered they were applied to the hull, followed by the pinstripe tape.

With everything in place, the hull was coated with several coats of clear lacquer. It will now be left for a week to fully harden before moving on to the mast and rigging.