A few years ago I saw a couple of Adamcraft sailing dinghys and was taken with the simplicity of their appearance on the water.

More recently there was an article about Adamcraft in the Model Boats magazine (Sept 2023) which rekindled my interest.

A search of the Sarik plans catalogue on-line came up with MM153, an 21" clinker built dinghy which looked similar to the Adamcraft model. A few days, and a few pounds later, the two sheet printed plan arrived. Studying the plan, I soon realised that what looks to be a simple boat when its completed, is far from simple when it comes to construction🤔. This wasn't helped by the fact that the plan was originally published in the Model Mechanic Magazine" July 1948. Some details are missing from the plan, no doubt covered in more detail in the magazine, but I couldn't find a back issue of that mag! However, I like a challenge!

The first issue to resolve was the overall size. The plan is drawn at 1/8th scale giving an overall length of 21". I decided to scale it up to 1/6th scale giving an overall length of 28" (710mm) as I find small boats struggle a bit on choppy water. The larger size should give more stability while still being relatively easy to transport.

Down to the local printshop who scanned the plan and provided me with two .jpg files. These I was able to rescale on my PC. Many of the enlarged parts, like the bulkheads will fit onto an A4 sheet so I was able to print those as templates using my inkjet printer. Other part outlines don't need to be printed full size as they can be marked out directly onto the timber using the dimensions on the plan (suitably scaled of course!). As the plan was drawn pre metrication the original dimensions are all imperial. I don't like trying to measure out 3 11/16" or 1 25/32" not to mention having to scale those dimensions from 1/8th scale to 1/6th so a few minutes (hours?) with a spreadsheet and I had the required measurements scaled and converted to metric equivalents. The metric dimensions were then added to the plan in red ink, before printing out working copies.

Next, I'll finally be able to start cutting some timber! 👍

The keel includes a keel box for a centreboard. I'm planning to make a fin and weighted bulb rather than use a centreboard but retained the box for appearance. I think it will be safer to have some weight down low to prevent the dinghy heeling over too far and shipping water. The fin will slide into the keel box and be held in place with retaining pins through the box.

The keel is made from eight separate pieces. Patterns for each piece were printed on A4 sheets, glued to the timber blanks and then cut out. A full sized plan was then printed on 3 A4 overlapping sheets and used as a template for assembling pieces into a complete keel.
The timber is oak, salvaged from an old tabletop with ply used for the keel box and the false rebates

The hull is built inverted on a jig. There are four bulkheads which will form part of the completed hull, together with three temporary moulds which ensure that the planks are laid to the correct form.

The bulkhead shapes were printed and then glued to 4mm birch ply before cutting out. The same approach was used for the moulds although these were cut from 12mm construction ply.

The bulkheads and moulds all mount onto a timber strongback which was marked for cutting out using the scaled up dimensions from the plan.

The strongback was then screwed to a flat board and the bulkheads and moulds were fixed in position. The front pair of bulkheads are bolted together using two threaded rods which run through holes in the strongback. A similar arrangement is used to hold the rear pair of bulkheads in position.

Finally, the keel was fitted into the notches along the centreline of the bulkheads and moulds. It was glued to the bulkheads but not the three central moulds. Everything was checked for square before the glue dried. The complete assembly has turned out to be very rigid, which is probably going to be a good thing when it comes to fitting the planks.

Before starting the planking, the location of the top edge of each plank was marked onto the edge of the bulkheads and forms. The edges of the three forms were also taped to avoid the risk of any of the planks sticking as the forms need to be removed once planking is complete.

The planks are 2mm thick mahogany strips cut from some salvaged 25mm thick boards. They were cut over thickness and then sanded both sides using my homemade thickness sander.

There are 24 planks required in total, 12 on each side. Each pair of planks (port and starboard) should be identical but are different from all the other 11 pairs. The plan includes full size templates for the planks so these were used to mark out the planks before cutting on the bandsaw. The ends of the planks need to have rebates planed along their edges (arrowed in photos 3 and 4) to overlap the previous plank. This gives a flush finish to the planking at the stem and transom.

Once shaped, each plank is glued into position along it's length and clamped until the glue has set. It is difficult to shape and fit more than one plank a day as the glue needs to set before the clamps can be removed for use with the next plank.

As the planking continues, the planks become more and more curved to the point where it is not possible to cut a plank from the 25mm wide mahogany strips. Curved blanks had to be made using two or even three pieces scarphed together. A curved plank, ready for fitting made from three pieces can be seen in the first photo.

A second problem that became apparent was that the templates included as part of the plan were not the right shape for the enlarged scale being used. The planks required more curvature than shown on the plan. I think this was caused by the change in scale rather than an inherent error in the original plans. Changing the scale of a 2D drawing of a plank which is going to be bent into a 3D object doesn't work.

The templates had to be dispensed with, and each plank marked and shaped to fit by trying it in place on the hull over and over again. It took around 2 hours to shape each plank before it was ready to glue and clamp into position.

Finally, all the planks were in place and the completed hull could be removed from the strongback. The three central formers were removed giving a clear open interior.

Before fitting the ribs, I cut gunwales from oak and glued and clamped them in position. These were flexible enough to bend into shape and clamp in position without steaming. Unfortunately, the ribs have a sharper bend and could not be bent dry without splitting.

A steamer was constructed using offcuts of plastic drainpipe (I knew it would come in one day!). Steam was generated using an electric wallpaper stripper. Strips of oak with a cross section of 25 x 4mm were steamed for 30 minutes and then clamped in a jig overnight. The bent strips were then cut using a bandsaw into 4 x 4 mm ribs.

While I have a good collection of clamps, I didn't have any of a suitable size to allow the ribs to be clamped in place along the keel. So more of the oak (recycled tabletop) was used to make a couple of long reach clamps using 8mm threaded rod for the clamp screws and to reinforce the frame.

Finally, the ribs were glued into position, two at a time.

In traditional clinker built boats the planks are nailed together with square shank copper nails. These are clenched on rooves or copper washers in the inside. At 1/6th scale, this would be difficult to achieve (!) so I opted for a sipler approach of using 0.6mm dia brass pins.

The pins for the first rib were fitted by drilling 0.4mm holes from the inside of the hull, through the ribs and planks. Once that datum had been established a compass was used to measure the distance between ribs on the inside of the hull. This dimension was then transferred to the outside so that the holes for the pins could be predrilled in the correct position at the edge of the planks. The occasional hole in the wrong position was redrilled. Those in the wrong position are not noticeable and will be sealed when the hull is varnished.

In total 550 nails were fitted!

The plan includes templates for the floor boards. I decided to split the boards in half lengthways to make the completed floor easier to remove.

The templates were glued to some 3mm thick cherry planks, cut out with the bandsaw and then glued to support beams.

The completed floor panels fitted into the hull with very little adjustment needed. Much easier than the hull planking where the increase in model scale resulted in the templates becoming distorted.

At this stage, the hull was given several coats of yacht varnish inside and out because it will become more difficult to apply any finish to the inside as construction continues.

I want to hide the radio gear as far as is possible. Not easy with an open dinghy. There are two enclosed spaces, one at the bow, and one at the stern.

A wooden tray and support were added behind the forward bulkhead for the receiver. The tray slides out through the bulkhead and is held in the closed position with a magnet. This position keeps the receiver as high as possible for better reception and hopefully will avoid any water that might get into the boat.

The rudder servo is mounted between the rear bulkhead and the transom. Once the rear deck is in place only the servo shaft will be visible. The deck will need to be removable to allow access for servo maintenance.

There isn't anywhere to hide the sail winch so it is mounted as low as possible at the forward end, just behind the forward bulkhead. This will hide it from view when the boat is out on the water. A mounting bracket was made from a short length of aluminium angle.

The mast passes through the forward thwart with the foot of the mast resting on the keel. There is no information on the plan detailing where exactly the mast rests on the keel so I decided to make an adjustable mast step so the position can be adjusted.

A short length of brass angle was marked and drilled with 1.5mm holes. The spacings are not as even as I would have liked, but the best I could do, and near enough. The angle was then cut down to leave a row of notches. An additional length of brass was silver soldered to the angle to produce a 'T' section.

For the foot of the mast, a fitting was made to push on to the end of the mast, with a slot which fits over the brass T section. A pin fixed across the slot (difficult to see in photo 3) engages with one of the notches in the T section.

Finally, the T section was glued and pinned in position on the keel.