Dealing with compounding errors

[Don Case]

Is there any secrets/methods to work around compounding errors? In my case the R+S is 28" and there are 30 of them. If I start at one end and measure 28-28-28 etc when I get to the end I will be out quite a bit. An other way is to use a ruler and mark off 30 increments each one being of questionable accuracy but averaging out to 28". Is there another way?

[kurtvd19]

Look up the fan sheet used for determining plank widths - check the planking tutorials to see how the fan sheet is used.

You can adjust the spacing to any width by moving the fan.

 

[Jim Rogers]

If cutting you need to account for the blade kerf otherwise a compounding error occurs.

 

[Louie da fly]

I agree with Kurt - the fan sheet is the way to go for the job you're doing - but Jim is also correct when cutting.

 

I used to be a building designer - when measuring up a building I was taught to do a "continuous measure". Measure everything in relation to a specified "zero" point. So if measuring a wall with windows, doors etc, rather than measure from the corner to the first window, then the width of the window etc etc, I'd hook the tape measure to the corner of the wall and treat that corner as zero, and then all measurements were taken in relation to that point - i.e the distance from the corner to the window, then from the corner to the other side of the window, then from the corner to the next window etc etc.

 

Steven

[Don Case]

 

 

Kurt, I couldn't quite see what you getting at but now that I've thought about it I can see a gllmmer of how you would use the framing fan for spacing frames. I'll sleep on it🙂 

 

That's more to what I was getting at Steven, how you actually measure it. If you have to put a frame every 1/2" you can cut a stick 1/2" long and step it off and compound the tiny mistake you made when you cut the stick or you can use a yardstick and put a tick mark at every 1/2" mark. Each mark my be out a hair but they will average out. I just thought there may be a third method that I hadn't heard of. Maybe the framing fan😃

[CDR_Ret]

May I suggest that the best way to avoid cumulative errors is to measure each frame's position from the same reference point?

 

I had the very same issue with my Galilee plans. 16-inch double-frame room, and 12-inch space. 58 frames.

 

I used a spreadsheet (Excel) and created a formula to calculate the positions of the aft, middle and forward faces of each double frame referenced from the aft-most frame. Each of these positions are 28 inches farther forward along the hull in relation to the previous frame's. The results can be accurately calculated to whatever precision you choose, and in whatever units you need (including fractions, if desired).

 

After the spreadsheet is filled in. You can use a long precision ruler to accurately mark your frame positions.

 

Hope this helps.

 

Terry

Edited March 3, 2021 by CDR_Ret

[SJSoane]

I agree with the cumulative measuring idea. One way is to measure from a set point out to every frame. Another way is to draw the frames on a jig at the base of the hull (see below). Either way, every time you place a frame, measure where its face ought to be. If the frame needs thinning down, sand the face on sandpaper glued to a sheet of plywood. That keeps it flat, and you can use calipers to check the thickness of each edge to ensure the two faces are parallel.

In my project below, the frames turned out to be varying thicknesses to keep the whole thing the right length as I added to the hull, but the differences are so slight that you never see the discrepancies.

 

Another subtle opportunity here. In my case, I set a square against the face of the frame. If it was slightly out of square to the base vertically, I used the sandpaper on plywood to gently adjust top or bottom to get everything back into square.

 

Mark

 

[Don Case]

Thanks all

[CPDDET]

I'm going to butt in here with a question.

 

Being somewhat new to this hobby I'm still learning the terminology as I work on my POB Bluenose. I realize this post refers to a POF build and pretty much understand the question being asked. But what does "R+S" refer to?

[CDR_Ret]

22 minutes ago, CPDDET said:

But what does "R+S" refer to?

There are many here who have a much more detailed understanding if this concept from a historical perspective. But it simply means the combined width of a frame (room) and the distance between frames (space).

 

So room and space (R + S) is the total distance from, say, the forward surface of a frame to the forward surface of the next frame. The way I understand it, the concept is meaningful only if the frames are set square, have the same sided dimensions,  and are equally spaced. But I could be mistaken....

 

Terry