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Have I got this garboard layout correct?


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I'm working up a layout for a friend and wanted to see if I have it sized correctly.  The Keel is 14s x 40m and apparently the shoe is counted in the sizing.  I don't know the shoe thickness, but best guess is 4 inches.

 

The rabbet line is let in 4 inches at midships and 3.5 inches at the front and rear.

the garboard strake is 8s x 14.5m

1st diminishing strake is 6s x 14m

2nd and third are 5s x 14m

the solid gray curved line in the image is the Mold Line

the dashed black line below it is the ML offset 4 inches, e.g. the standard plank thickness

B3xL0Er.png

The two "guessed at" factors in this are:

1. the size and number of diminishing strakes

2. the distance between the top of the keel and the Mold Line.

 

The drawing I have scaled with the bottom of the shoe being at 40 inches below the mold line, but that doesn't jibe with the overall keel dimensions.  The overall keel would have to be around 44"  it would have to a bevel rabbet.

 

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I would change the angle of the rabbet to encompass the full garboard thickness.

Since the position of the surface of the frame is hidden when planked, I think that the adzmen

would only dub the proud outboard corner of the diminishing strakes off.  The resulting smooth surface

would be a slope that is a bit more eccentric than the curve that you have plotted.

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So Jaager, you think it would be more like this with the light blue line being the surfaced line? This number and size of DS's seems more reasonable.

 

The rabbet line is let in 4 inches at midships and 3.5 inches at the front and rear.

the garboard strake is 8s x 14.5m

1st diminishing strake is 6s x 14m

2nd is 4.5s x 14m

the solid gray curved line in the image is the Mold Line

the dashed black line below it is the ML offset 4 inches, e.g. the standard plank thickness

The solid blue line is the dubbed off line

iE4AsNo.png

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A wedge was not cut in the face of the garboard edge where it meets the keel.

The right angle face was kept.  The angle of the rabbet was adapted to meet it.

Thus, unlike on the plan, it was not a fixed dimension internally. 

This will fix your too deep notch at the top of the keel.

The object was to provide a space for caulking the seam, without there being an

acute angle to chip off on the garboard.  There would be one if the keel were kept intact and

the face of the garboard was trimmed to mate it.

 

In a fully planked hull on a model, which face is trimmed does not make much difference, since it is

hidden anyway.

Edited by Jaager
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These are the references I am working with.  The cross section isn't the exact ship, there are no references for that ship, this was a sister ship launched by the same builder/designer just a few months earlier than the one I am working on. It doesn't show the smoothing, it just shows the board layout.

TEt1mNS.jpg

This list of notes was taken from the table of offsets, the only document that I actually have that I know is specifically concerning this hull.

p1ov9Fq.jpg

I can only guess as to what it means, and my guess is that it means the depth, e.g. at the rabbet line.

 

 

 

 

 

 

 

 

 

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I don't know what to say about that rabbet.  I see it as weakening both the keel and the garboard. 

The upper half of the seam could not be caulked and it limits just how deep the oakum and pitch could go.

If I were the ABS, I would want to do the experiment.  In use, there would be a lot of movement and stress along this location.

As far as the dubbing, that is from what was done at the wale.   The 17th C  there was a step function between it and the bottom plank - on either side.

This evolved into a smooth transition from below and a step function above for a time.   By the 1850's

the transition was smooth both below and above,   That there was a wale is not obvious.

Edited by Jaager
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On 7/5/2018 at 5:47 PM, Jaager said:

I don't know what to say about that rabbet.  I see it as weakening both the keel and the garboard. 

The upper half of the seam could not be caulked and it limits just how deep the oakum and pitch could go.

If I were the ABS, I would want to do the experiment.  In use, there would be a lot of movement and stress along this location.

As far as the dubbing, that is from what was done at the wale.   The 17th C  there was a step function between it and the bottom plank - on either side.

This evolved into a smooth transition from below and a step function above for a time.   By the 1850's

the transition was smooth both below and above,   That there was a wale is not obvious.

Just a side curiosity question, regarding the non-grooved method you are discussing, how does it work near the stem and stern when the loft of the hull form can start approaching angles greater than 45º?  At 45º a 7 inch garboard would be rabbeted 5".  On the piece I'm working on, the forward most frame (probably a cant frame at this point) is at 82º from horizontal, would the rabbet be 6-15/16" deep? Or did they thin it out fore and aft?

Edited by rtwpsom2
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I am guessing here, but what ever the angle of the rabbet is for the garboard to fit at the dead flat - that would be

continued fore and aft and the edge of the garboard trimmed back to match it.  This would not really  compromise

the plank and would preserve the keel.  Also, at the skeg,  the deadwood was cut into for the bottom plank lands.

In deadwood area aft as well as toward the bow, there is no advantage in a garboard that is thicker than the bottom plank.  I have not seen any aft stations

where the curve is any deeper for the garboard..

The ship builders were not the sort to do any more work than was necessary.  The hogging stress was mitigated by the depth

of the deadwood. A thicker garboard would = insignificant additional strength, and a lot of pointless work and material cost.

Edited by Jaager
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