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Transfer measurements/markings


achuck49
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Good Day

 

I will attempt to be as clear as possible with this question, no illustrations are available at the moment.

 

In some kits there will be printed, on one side only, the location of the rabbit (for example) but the other side will be blank.  How is this accurately transferred to the blank side (mirror image)?

 

I will use a cannon to determine the size of a gun port.  This information is marked on the inside of the hull.  How can I accurately move this information onto the outside of the hull, which is curved?

 

Some instructions/blueprints will clearly so where the rabbit is to be located.  This is, of course, a curve and shows only one side of the false hull, again a mirror image is required for the other side.  Once again, what is the most accurate means of transferring this information?

 

These are examples of my more general question.    How is information located on one part of the model accurately moved to another location?  Is there some type of tool/instrument involved that I have not thought of?

 

Thanks for any help that you can provide

 

Chuck Aldrich

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Chuck,

I had this same issue when I laid out my gun ports. I used a combination of a beam compass, center finding square, straight edges and lots of patience and remeasuring.

First I laid a line through the center of my barrels on the plans - hard to see in the picture but if you look closely they are there.

 

post-326-0-78543200-1471811237_thumb.jpg

 

Then I found a point on the plans that I could measure from, in this case I used the center of my cap rail where the port and starboard rails intersected. I opened my beam compass up to a point where it intersected my cannon center line on the cap rail making sure I was measuring to the center of the rail. I am using a regular compas in the picture as my beam compas is at work, or the cat has walked off with it... :D

post-326-0-48070600-1471811403_thumb.jpg

 

I dont have pictures of the next steps so I will try to explain. I am too far along on my build to try to show you the rest with pictures.

 

With out changing the setting on my compass I found the same point on the model and transferred a mark to the center of my hull wall. (I know there is a name for that portion of the ship but it is eluding me)  I did that for all the center lines then using a center finding square I marked a line across the wall perpendicular to the curve of the hull. I again used a center finding square to transfer that line down both inboard and out board. I now had a lines that were as close as I could get to being perfectly aligned. After that it was a simple matter to carefully measure out the same distance from my center line to set the width of my port cutouts. The height was set with a small combination square and a micrometer to strike a horizontal center line. Again carefully making sure I was measuring down the same amount on the inboard and outboard sides.

 

After that it was a simple matter of going to my religious house of choice, doing some heavy praying and cutting out my ports. The more experienced may have a more accurate/efficient way of doing it, but that is what worked for me.

 

I hope I explained it properly and that it helps.

edit -  Going off the center line like I did let me measure port and starboard with one measurement, ensuring my ports were lined up correctly

Sam

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If you have a computer and a scanner you can scan parts of the original plans, print what you scanned (flip it if necessary), and cut out what you need to put onto the wood or simply use as a reference. For something like a rabbet on a false keel, you can put some carbon paper under the printout to transfer the lines to the false keel. Or use a pin to prick a series of holes along the line in the drawing and then draw between the pin pricks on the false keel with a fine pencil. I often will take the scanned printout of some part and rubber-cement it to a piece of wood to get the size/shape I need.

 

Cheers -

John

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If you use John's method -  the amount of distortion that your scanner introduces should probably be determined and corrected.

I used a transparent 15 cm ruler as a source and printed the scan of it.  When matched to the original the scan has to be

X & Y scaled up by 102.5% to get the print to match the original.

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Be careful of using a  side view of a curve to determine spacing, distance along the ark of a curve is always greater than the chord, that is true even if the image was  perpendicular to the chord. A side view using C/L as the base, any curves will have constantly changing rates of distortion depending on the position of the radius point and distance from C/L. The top view and the compass arc method as shown by Sam will provide the more accurate locations of points along a curved hull, both inside and out.

jud

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