The believed abstraction of a 12 foot clinker dinghy.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

The idea of a false floor and open transom was a fleeting moment.

I made a rough pattern out of core flute material so that I could adjust the shape to a point where the look was appealing.

Curved transoms look great but I did not want to start cutting into the strakes along each side to accommodate this.
With the pattern I was able to establish the fact that I could curve the top edge while keeping the perimeter on the original transom plane.
I also moved the bottom edge inwards slightly to create more aft rake.
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When I obtained the desirable curve, measurements were taken for the construction of a jig.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

The jig consisted of a panel of MDF for the base.A wedge shaped piece was placed centre,the thick end measurement equaling the deepest part of the transom's top edge curve.
The coreflute pattern was then placed across the wedge to establish the transom perimeter which was then drawn onto the MDF.
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A batten was then bent across this wedge to establish the landing for the panels that made up the transom lamination.
The landing surface was planed until a fair curve was reached across and down the length of the wedge following the drawn curve of the transom.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

The panels I made from recycled Kauri floorboards.
Kauri which most of you will know is a New Zealand native timber that was used extensively in the boat building industry back in the day.
The qualities that this timber possesses across the board (excuse pun) for boat building is, I think, unparalleled.
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I made up three panels.Each panel was 6mm (1/4") thick and by area enough to cover the jig.
The first panel was laid over, then each subsequent panel was made a little smaller in area to allow battens to be fastened around the edge.
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After first dry fitting, thickened epoxy was then liberally spread over the panels.The curve of the panels combined with the stiffness of each panel created enough pressure to ensure a good lamination when fastened.
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The best panel which would be viewed from astern was left till last as this will be bright finished.The inside face will be painted.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

So this is what I ended up with after removing it from the jig.

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I checked the symmetry of the hull at the aft end to make sure nothing had moved or twisted and was happy with the result.
The next step was to scribe the transom in.The beam measurement at the most aft point of the sheer was my datum. Transfering this measurement to the transom piece I then placed my coreflute pattern square and even off these points and drew around it.
I knew this line would be slightly larger than the transom opening also allowing for the land angle from inside to out.After cutting out I placed the transom inside the boat and started to scribe in, slowly moving the transom back toward the stern as it was trimmed.
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I reached a point where the land of each strake was nestled against the transom quite nicely.This created more aft rake which I liked.This can be seen by the skeg protruding past the lower edge of the transom.
After a few minor adjustments I fixed it here with a thickened epoxy mix and small screws.
After curing the strakes were trimmed flush.
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The next step was to measure out the lands for the new hood ends of the damaged strakes.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

Before removing the damaged strakes I transferred the line of each lap to the transom edge.I checked the symmetry each side of the keel to make sure it looked ok.

I then cut the strakes back staggering the joints which will be scarfed.Now at this point I will raise the question of the close proximity of the scarfed joints.If the dinghy had been constructed of solid timber with riveted and roved laps I would not have attempted to do this.It is however ply with battened seams and with scarfed joints will be a very stiff part of the hull when complete.The stern sheet framing will also follow this line of joints.All will be revealed later in the thread.
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The lands pictured were later trimmed further as each strake was fitted to create a fair curve and run.

I then proceeded to form the 8:1 scarf joints.Using the plane and following the lines of the lamination in the ply was straight forward to create the taper on the bench.
In the dinghy it was a different story as I had to form the taper under each lap.This I did with a multi tool,then finished with a broad chisel.I placed a block under the work to support the edge as I went.
The 4mm ply sitting on the hull was a piece that I managed to score off a friend just an hour before covid lockdown here in NZ.There was just enough to complete the job while we were in isolation.

[Peerie Maa]

Re: The believed abstraction of a 12 foot clinker dinghy.

Before removing the damaged strakes I transferred the line of each lap to the transom edge.I checked the symmetry each side of the keel to make sure it looked ok.

I then cut the strakes back staggering the joints which will be scarfed.Now at this point I will raise the question of the close proximity of the scarfed joints.If the dinghy had been constructed of solid timber with riveted and roved laps I would not have attempted to do this.It is however ply with battened seams and with scarfed joints will be a very stiff part of the hull when complete.The stern sheet framing will also follow this line of joints.All will be revealed later in the thread.
[ATTACH=CONFIG]66288[/ATTACH][ATTACH=CONFIG]66289[/ATTACH][ATTACH=CONFIG]66293[/ATTACH]

The lands pictured were later trimmed further as each strake was fitted to create a fair curve and run.

I then proceeded to form the 8:1 scarf joints.Using the plane and following the lines of the lamination in the ply was straight forward to create the taper on the bench.
In the dinghy it was a different story as I had to form the taper under each lap.This I did with a multi tool,then finished with a broad chisel.I placed a block under the work to support the edge as I went.
The 4mm ply sitting on the hull was a piece that I managed to score off a friend just an hour before covid lockdown here in NZ.There was just enough to complete the job while we were in isolation.

The Scandinavians, who invented clinker building were not too bothered about scarfs being close together. With well-cut scarfs, and good glue you have nothing to worry about.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

Fitting of the strakes started closest to the keel.
One strake was fitted each side per day to allow for decent clamping of the scarf and overnight curing of the thickened epoxy.
Small screws were used along the laps to hold, then removed the next day.
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The final fit of each strake was made by paring the landing until the run of each strake looked fair.
The edge of the previous strake was beveled to receive the lap of the following piece.

[stromborg]

Re: The believed abstraction of a 12 foot clinker dinghy.

Thank you for the tutorial. I have a 60-ish year old plywood lapstrake runabout (hiding under a tarp until I have time to get around to it) with similar soft spots.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

My pleasure Steve.Glad to be of some help.
I totally agree with that quote from H.A. Calahan by the way.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

As you can see in the bottom image of the last post I have rigged up a block and tackle arrangement which allows me to rotate the dinghy.
This enables me to position the hull at a comfortable working angle to the great relief of my rotator cuff tendons.
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The inside of the hull was completely scraped/sanded and epoxy sealed.
The epoxy sealer I used is made here in NZ and is a thinner less viscous liquid with anti fungal additives to deal with any potential rot problems.
Then every lap was strengthened with an epoxy fillet.The fillet recipe consisted of 1 part 404,2 parts 406 and 2 parts 407 by volume of West System fillers.
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I ended up increasing the fillet width around the transom perimeter for peace of mind.
Most of this will be hidden by the stern sheets as will be revealed in future posts.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

Now we come to the sternsheets or in layman's terms,the back seat.
Another piece of coreflute was cut out and placed in the stern to get an idea of the look.
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After a few minor tweaks I drew a more accurate shape onto a solid panel.Along this line I placed the stations that the laminations (Kauri, 6 of 90x3mm) would lay against.
This lamination would form the frame for the front bulkhead of the seat as I also plan to have watertight compartments.
Not only would it be this shape in plan but it would also replicate the same crown/camber as the deck,hence the 90mm (3-1/2") width of the stock to allow for the curve.
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[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

Now this is where the post heads off in a totally different direction for a moment and that is...toward the bow.
I had replaced the transom and it seemed now that the aft end was looking nice the bow would need to come up to standard.
I was constantly thinking about how I would do it, so much so it was distracting me from the sternsheet construction.So I just got on with the job of replacing the stem.
This is what the original stem looked like.Laminated Kahikatea (white pine) and what seemed to be lots of polyester resin.
So with a trusty reciprocating saw and planer off it came.

I then laminated a couple of strips of wood around the profile of the stem.A piece of mdf was hot glued to this on which to draw the new stem profile.
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The idea of a reversed raked stem appealed after seeing an image of the catboat "Molly B"designed by C.C.Hanley.
I would just like to point out at this stage that I design and draw pretty much on the fly to a stage where I just like the look.I enjoy the process and results,
hence the "believed abstraction" heading for this thread.
So after drawing and erasing a few lines I came up with something that appealed and allowed a little leeway for altering the shape if needed.

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Made two patterns,selected the Kauri,cut the shapes and then joined them together complete with a spline.

[John B]

Re: The believed abstraction of a 12 foot clinker dinghy.

Looks fantastic Mike. That's a lucky little boat to have found you.

[Mike1902]

Re: The believed abstraction of a 12 foot clinker dinghy.

Looks fantastic Mike. That's a lucky little boat to have found you.

Cheers John.
I've been a WoodenBoat forum lurker for a while now.
Feeling I now had something to contribute thought this project would be good to share,especially now the CYANZ forum has died.

[John B]

Re: The believed abstraction of a 12 foot clinker dinghy.

I have a 12 ft clinker too. Its a Cox design. It's pig ugly and was built with no regards to standards.