Height correction and level setting using a scribing block as a cheap height gauge

[Toolmaker]

At this time I am fairly new to both wooden ship building and MSW. As such this is possibly a risky post as I might be either preaching to the converted or just plain wrong.

Although having completed just three builds, I have no doubt that the journey becomes akin to “wood engineering”. I have two 1/48 scale builds on the go and am committed to trying to work within +/- 0.5mm which equals about an inch in real world. I’d be interested if anyone can quote records with regard to accuracy of the day in the early 19th century.

 

Enough of the post introduction and on the the meat of the subject;

I have not seen much use so far for this tool on MSW but I feel it is under utilised. I see lots of spirit levels but sometimes think the user may not be getting the results they believe they are.

 

My two current builds have been set up on build boards made from spare kitchen cabinet panels. They are very flat and as spare, also very cheap. The top surface of the build board then becomes the datum. You don’t need to worry if your fixed work surface/table isn’t flat or level, just work from your build board datum. I think with a little experience it is easy to work within 0.2mm or 0.008”.

 

The tool has different names depending who tells or sells it. To me it was a scribing block used for marking out but it could be a simple height gauge or comparator. You could attach a dial indicator (known as a clock) or just a simple scribe as I have.

Above it is being used to adjust the heights of the bulwarks. In this instance I am not setting a known height, just matching the height of starboard and port.

 

This next picture I am matching gun port heights. Using the fine adjustment screw whilst moving the scribes point back and forth across the gun port until a touch is felt/heard. You then slide your scribe block to the opposite side and set your wood height accordingly. You will find you are quickly working within very fine tolerances without effort. 

 

The following picture looks to show a point I am trying to make. I have tilted my build board by an inch or so. Tilting it makes it easier to see the laser etch marks used as guides on the gun ports. Using a spirit level in this instance would be inappropriate here, but the scribing block method still works the same.

 

 

If you are building a flat keel model you can use the scribe block to set known heights from plans using an engineers rule or slip gauges to set the height. This takes a bit more effort if you are working on a curved keel model..

 

These scribe blocks are available for around £35 or $40. I’ll leave you to decide if that seems a worthwhile investment. If so, I would add a couple of caveats;

1. As per norm, make sure stem and stern are vertical to the build board.

2. That the build board is wide and long enough to move the scribe block around the model.

 

Now, If you have taken the time to read all that, thanks

 

Paul

Edited April 9, 2023 by Toolmaker

[Bob Cleek]

Oh yes, a "surface height gauge," as it seems to be called here on our side of the Pond, is a very handy thing to have, as your post has very well illustrated. In recent times, the simple "manual comparitor" models seems to have become less common. Most marketed now have the capacity to measure with a digital readout to a high level of tolerance and some even have provision for a cable connection for a CNC input. These guys cost two or three grand! The simple model you have is one of those things I'd love to snag at a garage sale, but I haven't seen one in a long time. Alternately, I use my dial indicator stand with a sharpened rod inserted in the hole for mounting the "clock" or I just take a suitably-sized block of wood and shim a sharp pencil on top of the block to the desired height and slap a piece of tape over it. Not what you'd call "highly accurate," but, as they say, "close enough for government work."

 

(Beautiful photos on your post, by the way! I'm sure a lot of the newer modelers will find your information very helpful! 

 

 

 

 

[Toolmaker]

12 hours ago, Bob Cleek said:

Beautiful photos on your post, by the way! I'm sure a lot of the newer modelers will find your information very helpful! 

Thanks Bob, trying to be helpful is the aim really. I’ve posted a bit on soldering and metal prep as that’s what I know a little about. Being a recent convert to wooden models I hoover up knowledge from here so only seems right to offer some suggestions that aI am more knowledgeable about.

 

To close my input here (unless any questions arise). I’d say the scribing block and some basic slip gauges are very useful basic editions prior to the full digital height gauge.

I’m fortunate to also have a basic set of slip gauges. Mine are metric.

 

A 1mm slip sat on one gunport;

 

A 1.3mm slip sat on the opposite side;

 

We have interference with the scribe point so the difference in height from the build board is less than 0.3mm or 1/2” in real world at 1/48 scale. Good enough for me.

Im glad you found it interesting.

 

Thanks

Paul

 

[Robere210]

Good to see people here are using the accuracy of machinist tools in their builds.

[wefalck]

As a kind of tool-junkie I have actually all those tools ...

 

Their usefulness for the individual builder depends a bit on the space you have available. As you noted above, one needs a solid datum surface on which the model sits and enough space on this datum surface to move the gauge around. This is something not everyone may have on the building board.

 

I used my height gauge, however, to mark out water-lines for painting ...

 

On the question of accuracy to which the shipwrights worked, I am not sure that this is a good question to ask. I don't think they worked to specific (measured) tolerances. In most cases ships and boats were constructed within a sort of framework, be it a shed or a scaffolding errected for the purpose. A line was stretched at height above the future keel and distances were measured/marked from this with plumbs and squares. This ensured the overall dimensions and the symmetry of the hull. The shipwrights sort of worked inwards from this frame. Hence, they were not concerned by cumulative errors in individual parts, as everything was made to fit into this enveloppe.

 

I gather from this strategy derives the use of spirit levels by modellers.

[Toolmaker]

50 minutes ago, wefalck said:

On the question of accuracy to which the shipwrights worked

Thanks for taking the time to reply on this. That’s interesting to hear and gets the imagination working in consideration of the old craftsman.

Regards

Paul

[tkay11]

On the question of slip gauges, I use cheap feeler gauges which were popular for measuring valve clearances in cars. I have four sets of them, each of which covers 0.05mm to 1mm. I now use them mainly for obtaining accurate cuts with the table saw, but of course there are plenty of other uses too, including height measurements. I think I bought them from eBay for about £2.50 a set, but that was some years ago.

 

Tony