Creating an Offset Table

**jhoward114** · 11-26-2020, 12:18 PM

Perhaps a question that demonstrates my rank amateur status in this process: I'm restoring this boat below: I've got the boat, and this set of plans (see link). I do not have an offset table. From the plans at this link (https://drive.google.com/file/d/1oxv...ew?usp=sharing) can I create an offset table? Should I create an offset table?

For my restoration, the key work is to replace, redesign the keelson and stem, and then design and add some kind of sheer deck (5 or 6 inches wide, I think).

Attachment 73831 Attachment 73832 Attachment 73833

**Peerie Maa** · 11-26-2020, 12:33 PM

Why not tale patterns directly off the boat?

**jhoward114** · 12-05-2020, 09:43 AM

I'm leaning that way. I didn't know if avoiding the lofting process is sort of cheating...(I'm using Greg Rossel's excellent book as one of my go-to guides). But yes, I was thinking of creating patterns. The key tasks on this project (see link here: http://forum.woodenboat.com/showthre...at-Restoration) is a new keel or keeson (not sure the proper term) and adding side deck all the way back to the transom, about 5 inches wide, I think.

**debenriver** · 12-05-2020, 06:06 PM

An Offset Table is really a set of tabulated data that allows the shape of a boat to be passed on to another in a simple one-sheet document.

In the days before computers, a designer drew the lines of the boat at scale and then took a Table of Offsets off the lines by measurement with a scale rule.

The builder then used the Table of Offsets to draw out the lines at (usually for yachts) full size – called laying off, or lofting – thus correcting any scaling errors that the designer might have made.

The builder would usually then produce a corrected Table of Offsets, which would become the de-facto Table of Offsets for the design. Patterns and moulds were taken off the lines on the loft floor and these were often saved in case more boats to the design were built. The corrected Table of Offsets was held in reserve for other builders, or if no patterns etc. were retained.

But if you have the boat and a set of lines, there is no practical value in creating a Table of Offsets, unless you wish to pass the data on to others; or build another boat to the design.

Cheers -- George

**jhoward114** · 12-08-2020, 11:21 PM

Thanks debenriver and TerryLL. So, good to know that if I have the boat and it has not misshapen over the years, I can just forget an offset table and draw specs and measurments off the the boat. Can anyone direct me to a good illustration/video showing me how to replicate station forms from the existing shell?

**gypsie** · 12-09-2020, 12:18 AM

There's a bunch of ways, trying to think where they are.
Leo on the Youtube channel; Tally-Ho took some patterns from his boat when making knees, that technique may work for you. I also think i recall the Acorn to Arabella taking patterns recently.
I used cardboard and just cut it till it matched, on a small pattern, a couple of weeks ago.

When you say redesign the keelson - do you mean replace or repair? Is it the keel you mean? Swapping out a keelson would not involve patterning the boat - I'd have thought.
Whats wrong with it? Can't you cut out the offending part (presuambly rot..?) and shape a replacement?

14ft boat with 6" 'deck' along the sheer. Feels a bit beefy for that boat - but i can't see the pictures. I'd consider laminating it up by fixing to the existing, inside and out.

nice lines, she'd be pretty.

**Peerie Maa** · 12-09-2020, 09:11 AM

Originally Posted by gypsie

There's a bunch of ways, trying to think where they are.
Leo on the Youtube channel; Tally-Ho took some patterns from his boat when making knees, that technique may work for you. I also think i recall the Acorn to Arabella taking patterns recently.
I used cardboard and just cut it till it matched, on a small pattern, a couple of weeks ago.

When you say redesign the keelson - do you mean replace or repair? Is it the keel you mean? Swapping out a keelson would not involve patterning the boat - I'd have thought.
Whats wrong with it? Can't you cut out the offending part (presuambly rot..?) and shape a replacement?

14ft boat with 6" 'deck' along the sheer. Feels a bit beefy for that boat - but i can't see the pictures. I'd consider laminating it up by fixing to the existing, inside and out.

nice lines, she'd be pretty.

It is this: http://forum.woodenboat.com/showthre...at-Restoration

Mr Howard of Montana, we need pictures of the trouble spots in the keelson, preferably with a picture of the full length of it. The foredeck will have to come off to wok on the stem.