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KAROO 1930 by Mark Pearse - 1:12 - 20' open sailing boat half model - SMALL


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Hi everyone

 

This is my second venture into model boat building. The first model was an unbuilt yacht design by a Sydney amateur yacht designer; this one is a much earlier design by the same man - E.C. "Cliff" Gale. Karoo was a 20' open sailing boat with a bowsprit & gaff sloop rig. Karoo was raced & was also a family boat. Incredibly they (Cliff & Mrs Gale, plus 3 strapping young sons) used to pack her full of gear for holidays & spend a week or two aboard on Pittwater, Broken Bay & the associated waterways Cowan Creek, Coal & Candle Creek etc. 

 

I'm doing a half model of the boat, as a gift for our sailing club model wall. The Karoo was a quick boat, I know because a copy was built about 20 years ago & despite her being given a fairly conservative sailing rig she is well able to keep up or beat with larger yachts. 

 

As with the last model the drawn information is not complete, but there are some photos of the original boat. And also I have one of the sons - Bill - who at 95 or so still has an astonishing memory when it comes to yachts. The drawing would have been done from a design half model, Cliff shaped the design in a bread & butter half model, layers dowelled together, & separated them to get the drawn lines.

 

I plan to show some details beyond just the hull: gunwale & toe rail, lower section of the mast, bowsprit, rudder & tiller, centreboard. 

 

 

Coincidentally, it was 90 years plus 10 days ago this drawing was done:

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The lines show a shallow dishy hull with clean underwater lines; the shape is beamy & shallow. A 40% beam:length ratio is wide, but beamy is (or was) quite common in Sydney:

hull_01.thumb.jpg.1fed848016737b22d282e94b3a1bb919.jpg

 

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Here, cantering under spinnaker at Pittwater, in the early 30s:

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This is the rebuilt version, she was slightly lengthened & made finer in the bow. Interestingly the owner's one comment is that she tends to bury the bow downwind under spinnaker. I'm guessing the original didn't do that, or as much, with more buoyancy in the bow.

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On the left, A12, with a removable cuddy cabin for cruising. 

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Edited by Mark Pearse
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  • 2 weeks later...

Another worth while build ... Can't wait to see you tackle this one. Thought I saw it in Open Boat by I.H. Smith but that can't be since those are 18'

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4 hours ago, cog said:

Thought I saw it in Open Boat by I.H. Smith but that can't be since those are 18'

Hi Carl

Nice to hear from you. You are widely read on boats if you know this book. I'm guessing you're thinking of the 18 foot skiffs, & there is certainly some influence. The Karoo is like an 18' skiff with more boat & less sail.

 

The skiffs had larger sail areas & 10 or 12 crew to keep it up & work it all - spinnaker poles had 3, 4 or 5 pieces each around 3.5m long. Their hulls are wider & shallower, but the lines are certainly similar. Cliff Gale did race the 18 foot skiffs, & his thinking in the Karoo design is influenced by them. Karoo would be manageable single-handed if it wasn't very windy, & raced with 3 or 4 crew. 

 

18' skiff Brittania, 1920s - so same period as Karoo

2141315692_ScreenShot2020-05-05at1_20_46pm.png.32c2fd6963e3a7b5dd3b06b030c2ff1f.png

 

HistoricSkiffs2013-0165.jpg.781ca599355755337a49e6ac85baf5ee.jpg

 

 

 

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I like those skiffs, Mark. It is certainly on my bucket model list. Time, however, is of the essence, and I've got not enough of it. Hence, I'll enjoy you building one.

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  • 2 weeks later...

Hi Vaddoc

 

Good question, & I believe the expert opinion is that in a yacht there's a beam:length ratio that shouldn't be exceeded. However, the conventional wisdom isn't foolproof - our own yacht is 3m beam & 7.3m hull length, so very beamy - as a design almost 90 years old she is comparable sail performance to a modern cruising yacht of the same length, & in lighter winds we can usually convincingly beat comparable modern boats. The Karoo isn't a yacht as such, but I think some things do apply.

 

A hull's 'righting moment' is key, it balances the wind power. The two simple ways of giving righting moment are ballast & positive buoyancy. Ballast is easy & we all understand that. Positive buoyancy is the resistance of a shape to being pushed into the water - so it "pushes back" when you try to tip the boat. A beamy boat has more than a narrow shape simply because it's wider. So ..... you can then get rid of some ballast & make the boat lighter - less weight, less wetted area etc. It's a balance, there is no one approach that is right or wrong, the best designers can do this remarkable balance...& they can still come up with a great looking boat.

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If I recall well from reading, the drag of a wider beamed boat is less than a narrow boat/ship. There is a set back, though: You can't deal as well with strong winds as a narrow beamed ship which has far more volume beneath the surface, hence, the search for the ideal beam is an ongoing adventure

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  • 1 month later...

Hi Carl, Vaddoc, others

 

Thank you for your concern & I'm very happy to say that I'm mainly well - apart from a heavy snow-skiing fall 2 weeks ago. Neither arm is up to sailing at the moment, but with the Spring sailing season soon I'll be ready for that. In their eternal wisdom our government decided that sailing & fishing were forms of exercise & so we did plenty of both during the worst of the lockdown in Sydney, the remarkable photo below was taken by a friend - us on a family outing one autumn day on an almost empty harbour. 

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The half model is going slow. The thing I've been researching is to confirm that the outside line on the sheer plan (on the drawings above) is the rabbet line ie: does not include stem or keel timbers. I borrowed a half model of the Yeromais (copy of Karoo, slightly revised bow lines), below. It's been made to the rabbet line, I think.

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I'm not ready to start building, but the prep is ticking over. I'm considering a planked half model, so the stem & keel timbers would be separately visible. I want to be sure it's correct, history can be based on errors. I've been able to get some poor photos of the Karoo as she is now, I've yet to do a close examination of them, but I believe they support my thoughts. I hope to visit her soon, when Karoo is next slipped, so I can take some dimensions etc. It's a couple of hours north of here at Lake Macquarie, she's been covered to a motor boat used as a starter boat for sailing clubs over the last 30 or 40 years.

 

Little bit more on the "beam" discussion - Vaddoc you will be interested to hear what I read: in the early 1900s Cliff Gale (designer of Karoo), raced on a lot of smaller skiffs, one of which was in the 10' class. They would now be called an "unlimited" class, so no limit to the sail area; the one rule was that the hull itself could only be 10' long. This boat had a 10' beam, so as wide as it was long....sounds impossible, & it was difficult to build. I will copy recent photos of 10 footers, the beam works because the hulls are shallow - hence "skiff". It doesn't look crowded, but 3 or 4 men in 3.1m is pretty tight. I would guess these are 2.5m beam. (my boat is visible behind in one, the pale grey stern)

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Wow, all these images of these very beamy boats are amazing. Beam as long as the boat it self, I think the following pic shows this well 😁:

walnut.jpg.f9d6a833c565b90f1df29a34102c6f00.jpg

Mark, is it easy to explain what your issue with the plans is? 

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Hi Vaddoc

 

The clues are in the drawings. In the body plan, the detail below shows the curved line of the planking stopping at a horizontal line, not faired into a deadwood or keel.

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It's probably clearer in the plan view of the lines, below. At the bow the hull lines do not show the pointed or rounded shape of a stem, they lines stop where the planking would meet the stem. The lines resolve as a line perpendicular to the centreline, not the smooth resolved shape of a stem profile.

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Below you can see the planking & stem & keel clearly with he paint removed. The second photo shows the rabbet line in dashed red; the yellow ochre line shows the hull profile if it was a centreboarder like Karoo(ie: no ballasted keel below the deadwood). I think the lines show the red dashed line, & left the rest to be resolved during construction. 

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1671005208_ScreenShot2020-07-14at8_24_27am.png.ffb8520c15d7fdc2479ef89c4570c7f2.png

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Mark, this is very unusual but maybe there was no keel? The plans really do not show a dead wood. Have a look at this you tube video bellow, there is just an apron with the garboard planks nailed on and absolutely no deadwood or keel. The apron seems to stand out a bit proud and that's it. 

 

https://www.youtube.com/watch?v=kMaClFVOf30

 

At 3:06 they prepare the apron to accept the planks

3:21 to 3:24, no keel whatsoever

Then when they transport the boat, it sits very low on the ground.

 

Vaddoc

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Hi Vaddoc

 

I was wondering what video was in store for us - it was the Brit! I've sailed a couple of times as main sheet hand on this boat, it was fun & hard work. But she actually does have keel timbers below the rabbet line, although not much at all. Otherwise there would be nothing for the bottom edge of the garboard to sit against. There's a deadwood aft, but again not large. I think Karoo probably had a more of both than Brittania, but maybe not much. If you see how the lines drawing of Karoo shows the lowest line parallel with the waterline, that was another clue - you would expect the deadwood to slope downwards towards the stern, as in the profile photo  below (Karoo replica being repainted) you can see the boat gets slightly deeper as you go to the stern.

 

IMG_1126.JPG.74269a08945b22ca79353f277840fe8e.JPG

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look in "the open boat" page 109 photo 9e. Does she have a fin you can lift? - pg 120 and further photo 11 b, c, & h or go to chapter 14 - pg 148. I've never seen Karoo, so it is more or less guessing from this side of the globe

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