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

[Mark Pearse]

6 hours ago, cog said:

Does she have a fin you can lift?

Hi Carl, yes there's a centreboard for certain - but a boat like Karoo would be pivoting & not lifting like the skiffs.

[vaddoc]

Mark, I thought you d enjoy the video! I see now what you mean, indeed there must be a bit of keel especially aft.

The only explanation seems to be that the body plan is to the outside of planks and that the keel has variable width, starting narrow at the bow, very wide midships and finishing very narrow at the stern. Despite being so narrow, a propeller shaft somehow needs to go through. The ribs will have to be half ribs slotted into the keel. At 20' and so beamy, this is actually not a small boat.

What the plans do not give us is how high the keel is, essentially the rabbet as you said initially.

Well, you certainly have some head scratching to do! 

[cog]

23 hours ago, Mark Pearse said:

Hi Carl, yes there's a centreboard for certain - but a boat like Karoo would be pivoting & not lifting like the skiffs.

Well there is part of your answer. I would expect the keel to take shape from the fin towards the stern, where it supports the rudder. Which implies there won't be much of a keel. Although, the Open Boat covers skiffs, the keel part holds for 17th century warships too. There is hardly any - I would almost go so far as to state there is none, compared to the bulk of the ship - and what could be defined as keel is most prominent at the stern.

[Mark Pearse]

Hi Carl

 

Sorry for the slow response - golly it's been a long time since I was here last. Yes, this boat has swing centreboard & it's just visible in the photo in post #29. I don't have the open boat book, so I'm not sure on the reference, but in this case (which is typical of a pre-1940 centreboarder) there would be a removable pin at the forward end of the centreboard case as a pivot. The front of the plate is usually straight & the aft edge curved.

 

I have made some progress: purchased timber, scribed the cutting lines & cut them out. I was considering planking over a solid model, but decided against it. So the timber is cut to suit the final size. 

 

I tried to get King Billy Pine, a Tasmanian Pine variety that is light weight & straight grained - but my local timber specialist didn't have it so I have used Huon Pine. The timber is a nice pale toast colour & will become a honey brown over time.

 

The next step is to scribe cutting lines on the timber & then do some rough shaping before gluing the pieces (lifts?) together.

 

Best wishes everyone.

 

 

 

 

[cog]

Thanks Mark, best wishes to you and the family. May we taste freedom again!

 

Taking shape .. nice colour wood indeed Mark.

[Mark Pearse]

many thanks Carl,

 

good to make contact again

 

 

[Jim Lad]

Good to see you back on the model, Mark.

 

John

[KeithAug]

Pleased to see you back at it Mark. I look forward to seeing her progress.

[Mark Pearse]

I started to pencil on the mould locations on the timber lifts, to help when I do rough shaping, of whether the sanded shape is straight, convex or concave.

 

I picked up an inconsistency in the drawings. It goes to the issue of which drawing do you give priority to when there's a discrepancy? In this case its pretty easy, fortunately. Also the fix should be pretty straightforward.

 

On the plans, this line was used to cut the the lift #6, it is the highest of the full length pieces. The red arrow points to it.

 

If you look at the transom, that line is pretty much vertically under the gunwale line. The small green circles show where the plan lines meet the transom. Numbers in red are the widths at 1:12 in mm.

 

 

Here's where the transom shape would have to conform to, if I was following the plan lines.

 

 

It's a lovely transom shape, it's an easy one. So, the plan lines will be adjusted to suit, as below, ie: following the gunwale. The pink is the shape of the top lift at the stern.

 

Good news is that I kept all the timber offcuts, & I won't recut the whole piece, I'm going to carefully add timber from the offcut.

 

[Jim Lad]

Always fun to find something not as you expected, Mark!

 

John

[vaddoc]

My first thought Mark was that the discrepancy in the plans was due to not projecting the transom as given in the plan to its angled plane. However, the transom in this boat seems to be pretty much vertical so this is not it.

Anyway, you fixed the problem!

[KeithAug]

Mark, all “buttocks” have dimples here or there.

[Mark Pearse]

Thank you all, & especially Keith - fortunately I wasn't drinking anything when I read that. 

 

Vaddoc, thank you - & one note on what you said: most boats built here at that time were done on a tight budget, & very few have exotic fitouts etc. The connection with what you said is that the bows & sterns are usually plumb - vertical. You get maximum boat for your timber that way. 

 

The 'lift' #6 (not sure if there's a technical name) needed to be corrected, as the previous post. I did that & also dropped the piece, so two minor repairs.

 

Below: the correction timber glued on, & the new ding on the bottom right, with a piece getting ready to be glued.

 

Below: now that's better. Transom pencilled on. Fascinating to see how slow Huon Pine grows. The lifts are about 12.5mm thick.

 

I am pencilling on all the positions of the mould, as shown on the drawings. So that when I'm rough shaping the lifts, I know if it's concave, convex or straight.

 

Before I start shaping them I need to try to setout the cockpit. I plan to show some basic details such as cockpit coaming, low part of the mast, rudder & tiller, gunwale. So, I'm going to hit the drawing board & see what I can work out - or guess - for the above.

 

Lastly, a bloke in a RIB was following our sailing race in January & took some lovely shots of our 24' gaff sloop Cherub. Of interest to any boat lover, but in terms of this blog, it was also designed by the designer of Karoo & the next boat after Karoo. So, if you'll indulge me.....

 

Approaching the start line.

 

Struggling to control the spinnaker pole on a tight shy run.

 

Before the start. 

[Bedford]

Cherub is beautiful Mark and looks perfect under sail. I know the Karoo will be a beautiful model well received at the club no doubt.

I would love to work with some nice huon pine, maybe one day.

[Mark Pearse]

Hi Steve

 

Yes, Cliff was a gifted amateur designer. I hope to be smelling the odd sweet scent of freshly cut Huon this weekend.

[Mark Pearse]

Using available information I've drawn up my estimate of the main parts of the Karoo. This is what I came up with, I've only drawn the details that I will be showing.

 

 

I used a mix of original Karoo photos & some of another notable open boat of a similar size & vintage, a locally very famous boat 'Vagabond'. There are very few, & not very detailed images of the Karoo, so I've relied quite a bit on the Vagabond images. The designer of Karoo had previously owned the Vagabond. There are many similarities, such as a short & slightly curved bowsprit, tall toerails with numerous drain holes 

 

This stern shot of Karoo was useful to estimate the width of the side decks, the gunwale width, & the rudder, also the coaming height & shape. 

 

 

These shots of the Vagabond were useful to see various details, which helped to confirm various things

 

 

 

 

The last shot is a beauty, the Vagabond is such a pretty boat, & is still around. 

 

I'm pretty happy with this plan setout, it "looks right" to my eye. I redid the top lift for the model & glued it to the second top one. I'll next scribe the cockpit opening onto that & cut it out.

 

all the best

 

Mark

 

 

[Tony Hunt]

It's looking very nice Mark.  The Huon Pine should look great when its finished to that lovely curvy shape.

 

I occasionally crew on a boat that races with the Amateurs, mainly in the twilighters in summer. Byzance, an S&S designed Swan 40, blue hull. I'll have to watch out for Cherub!

[Jim Lad]

'Cherub' certainly shows to advantage in those photos, Mark!

 

John

[Mark Pearse]

Hi Tony,

 

Yes I know the sky-blue Byzance. This half model is to be an addition to our trophy wall, the first Karoo trophy race was held this year Sunday 21st February, won by the gorgeous Peter Cole signed Tanami.

[Tony Hunt]

I'd love to see a picture of the trophy wall, Mark.

 

Tanami is ABSOLUTELY gorgeous, I agree.

[KeithAug]

Mark - I liked the "struggling to control the spinnaker" looks like broaching territory to me. I look forward to the next build instalment.

[Mark Pearse]

thanks everyone

 

Keith, we've never broached Cherub, they will go where you point them if your arms can manage it.

 

Anyway, back to the scale world, I've shaped the top part of the model. The top two lifts were glued together because the deck shape went across both pieces of timber. Unfortunately the top timber piece has a few wiggles in the grain & the hand plane did not like them at all. 

 

I removed most wood with sawn lines & a chisel.

 

And finished with a powered sander - it's an angle grinder with an attachment that gives a 1" wide belt sander.

 

Starting to look like a boat.

 

 

 

 

 

 

[Jim Lad]

Early days, but coming along very nicely, Mark.

 

John

[Mark Pearse]

thanks everyone

 

Amazing, a sunny day. The rain has been huge, much of the NSW coast has had over 400mm of rain in just the last week, & some places over 1m of rain in one week. Incredible volumes of water. But .... being selfish for just a moment, the sun certainly helps with taking photos.

 

I started shaping the half model lifts. I kept a lines drawing nearby to make sure I knew whether the shape between the edge & the pencil line was straights, concave or convex. When it was clearly getting close, but harder to remove more timber with certainty, I glued them together.

 

It's still rough, but most of the timber removals been done. In fact slightly too much on a couple of spots at the bow - patches required.

 

Sadly the sweet lines don't show yet. It may need to be mounted for them to show. I'm considering mounting it on a reflective surface. Not mirror, as there's a visual gap due to the glass thickness. I'm going to investigate polished stainless, even though the colour is a bit grey, the salty humid air at the sailing club wall would mean chromed brass would need frequent polishing.

 

Next step is sanding & more sanding. Then shaping added details.

 

 

 

 

 

Too much timber removed......

 

 

 

[KeithAug]

On 3/24/2021 at 9:32 AM, Mark Pearse said:

The rain has been huge, much of the NSW coast has had over 400mm of rain in just the last week

Mark - You even made the news over here. I always think bread a butter construction is a hard trick to pull off but the hull shape turned out quite pleasing.

[vaddoc]

You seem to be progressing very well Mark! I have no experience with bread and butter construction but I think this way of building a model is certainly challenging, with plank on frame the planks can show which frame is too high or low but with a solid hull I guess you just need to eyeball things. A lot of wood to be removed! 

[Mark Pearse]

Thanks everyone

 

The sanding is well progressed, I think hand sanding is the only way to do this. It's close in most areas now, time to keep a sharp eye on the shape. Fortunately a real shipwright (Ian Smith) made a half model of this boat & I've borrowed it, that will help a lot. I'll put up a photo.

 

To even out hills & divots I used a piece of 1.5mm thick styrene that is a bit flexible & wrapped the sandpaper around it. A friend makes architectural models so I'll go & get some thinner stuff as well, to help with the concave sections. Especially the turn of the bilge near the transom. And the bow still needs that patch....

 

 

 

 

[Bedford]

It's looking good Mark, I don't know how I'd go about making that. I can build up but the idea of cutting away to reveal the shape is beyond my understanding.

 

I know Ian Smith is building a ranger for his retirement, do you know which one it is?

[Mark Pearse]

Hi Steve

 

Yes, that's correct & Ian's boat is closely based on Ranger (her lines are a bit fuller than other versions of Ranger). If you search "youtube Ian Smith wooden boats" you'll find his channel, including recent videos on the Ranger build. My photos below are about 2 years ago.

 

This video is from several weeks ago https://www.youtube.com/watch?v=DlJK3pfdWBs

 

 

 

Edited March 30, 2021 by Mark Pearse

[Mark Pearse]

The hull has been sanded to shape, but not the final sanding. I've started making the extra pieces, rudder, tiller etc. I don't think a 'proper' half model has these, being a working tool to refine a hull shape. However, I am going to show them because it will show off a pretty hull all the better.

 

The patch at the bow is difficult to see:

 

But the patch on the topsides towards the stern is quite visible. The bow was done using epoxy with sawdust to colour; the topsides patch was using titebond, no colour added. I thought the titebond would disappear by being thin, however something didn't go to plan.

 

I started with a drawing of the rudder, which is made from a thick stock & a thin blade. The stock tapers away behind the hull as the transom tapers at the waterline.

 

Then made the pieces, unshaped below. The stock will remain squarish, this boat was generally a shapely hull with plain details. The rudder appears to hang below the hull, but I haven't yet added the lower part of the deadwood. That, plus the stem, will be an added strip.

 

Previous patch clearly visible. Hmmm.