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[Antipodean]

Heya folks. I thought I would share a lesson I learned today about buying plans from online sources.


A few years back I bought a Plaudit plan at 1:16 and one for a 85' Harbour tug at 1:24 from a guy on flea bay. Seemed genuine and the plans looked great.
I started the build on the Plaudit and found out the scale was miles off and the plans weren't that close to the real vessel anyway, that became the Lady Lou and I have resized those plans for the Plashy at the correct scale. Turns out they were 1:20 instead of 1:16 , not too hard to fix, just enlarged it a fraction.
Now that I have the time and some really good oak boards to build the tug with I got out the plans and set to work on translating them from 1:24 to 1:16 (42.5" to 63.75") to keep it in line with rest of my "fleet"
Took a measurement of the keel at various spots and the max length I could get was 40.25", slightly short of the correct length. Now I get to do math for a while to get the right scale measurement to get it to the size I need. It would be so much easier to work with if they had made the measurements off by a more rounded number but c'est la vie.
So just a word of warning, not all plans are created equal and not all sellers on flea bay know what they are doing.


Ian

[BrianB6]

Every draftsperson, architect etc. is consantly told NEVER copy off drawings. Always check the scale.
Worth putting a line with scale measurements on the drawing to check since paper and drawing film moves considerably with variations in humidity.

[TheLongBuild]

Never buy a copy 

[grendel]

as a draughtsman the biggest issue I see is pdf plans, even if they are exactly to scale when printed, unless you actually specify scale at 100% or click the print actual size boxes, most pdf programs will fit the plan to the page size - even if the page size is correct it will scale the drawing to 97%, not much, but enough to throw any measurement taken from that plan.
That said, working from a correctly scaled pdf is probably a good way to go for the layman, personally I would prefer the CAD plan (as I have the software to measure direct from the CAD file).
Grendel

[grendel]

its also worth noting that any large format printer is only accurate to about 0.5% - that can be 5mm per metre on a large drawing.
Most CAD software allows for printer calibration to adjust the printer.
To my knowledge I have never ever seen this used in practice, I have used it just twice in a 30 year career - and that was for a personal project.
So even a properly done plan printed from CAD can be out by 5mm over a 1m boat.
even humidity can affect the paper the plan is printed on in a similar amount as the printing process, your plans could shrink by 5mm during a dry summer, or stretch the same on a damp winter.
Never trust any plan not hand drawn on draughting film, that is the only stable material in the world of draughting.
This is why we work directly from the CAD program for measurements.

[warspite]

I always had a theory about dyeline printing (yea I know - showing my age), when the original is placed against the transfer media and shoved into what can only be described as a mangle (believe me some of the results resembled this look as well) as the two wrapped around the Perspex tube with the light source, inevitably the transfer media took the longer route being on the outside, slipped & stretched the drawing etc. scaling off a copy of a copy of a copy etc when the master was left out of the equation, i.e. a modified copy was altered for the next reiteration rev a , b , c , d ........z etc, it was always the case of no one wanted to have to redraw the whole drawing again.

[grendel]

one of my first jobs was with a company that had an old machine, with a single mercury vapour lamp, we only had 2 bulbs, and the started was a capacitor bank that had to charge for 12 hours to fire up the lamp. the drawing office manager remembered the wood frames you put the drawing and paper in - then took it outside into the sun for ten minutes, then placed the result into an ammonia filled cylinder to 'develop'.
Grendel

[geoff p]

About 40 years ago I got a loan of the builders layout plan for the "Earl of Zetland", and at work had it transferred to microfiche.  At home I put the 35mm transparency (which was what the microfiche was effectively) into a projector, shining onto a white wall, adjusting the distance till I got my required hull length (1-metre) and simply scaled off whatever I needed.

It wasn't particularly accurate but then again, nor was my boat-building.

Geoff,
Thailand

[Antipodean]

Well, I have to say you guys seem to know what you are talking about. I never knew how far off a plan could be or how much paper could stretch or shrink.
Seeing as these plans are not too far off I am going to work off them to expand them to the scale I want and see how it goes from there. Either way I am going to be building a tug that is over 60 inches long.
Not sure why I need one that big but it sounds like a nice idea.

[cdsc123]

Here's another thing to be careful of, not naming names but the plans I bought were from a well known and respected source. I found they were totally distorted see the picture and note the short set of frames which have been cut out and placed over what they should look like. Now that is distortion! 

[Antipodean]

I am also finding it hard to sort out metric measuring equipment as it is harder than heck to work this all out using the inches. Coming from New Zealand we went metric a long time ago and it is what I am used to but America still has a love affair with fractions. 1/16ths of an inch are not a friend of mine on the calculator.


Those frames look like a set I had a while back cdsc, another boat but just as badly copied. 

[NFMike]

You could make yourself a scale rule specific to this plan, so you put the rule on the plan and read off how long each distance is on your model directly in whatever units you want.
If the plan is distorted by being 'longer' in one direction you'd need two rules - and not mix them up!

If it's more distorted than that then this is probably not the plan you want at all 

[warspite]

I am also finding it hard to sort out metric measuring equipment as it is harder than heck to work this all out using the inches. Coming from New Zealand we went metric a long time ago and it is what I am used to but America still has a love affair with fractions. 1/16ths of an inch are not a friend of mine on the calculator.

Depending on your calculator - theres a button on most scientific types like a CASIO fx-83ES they sell for school kids in your local super market these days (not sure about your neck of the woods), it has a button who's sysmbol is a blacked out rectangle above a open rectangle box with a line between the two, set out just like a divide line (in the model stated there is also a sysmbol dipicting the full units and division part in orange related to the shift button).
 
To convert from imperial to metric it is simply a case of typing either the number of inches or the number of parts > press the button, enter the fraction base, i.e.
say its 5/16, then enter 5 - press the button, enter 16 - the press the X (times) and enter 25.4 for the millimetres, then enter, if there are inches, enter the number for the inches and then press the button before continuing with entering the 5 etc., the resulting number is the millimetres in 5/16 - 7.9375mm.
 
Apologies if you were already aware of this. 

[derekwarner]

Guys...it's just like working how many fluid ounces are in a glass & wondering if the Publican trying to short change us with new glasses marked in Ml? 

I do use my CASIO calculators for real work...but @ my age still prefer the true & tried method for understanding what 5/16"represents 

1/8"= 0.125 x 0.5 = 0.0625" for a 1/16

Five of those are 5 x 0.0625 = 3.125

3.125 multiplied by 25.4 = 7.9375 mm which is the same answer warspite arrived at  ............

But this is where it all goes bananas.........a 5/16" dimension is a "whole number" in terms of tolerance unless it is referenced as 3.125 +/- 0.015

But when we metricate the original 5/16"dimension we end up with a dimension of four .decimal places........... ......crazy..........Derek

[grendel]

for a rule of thumb - 1/16" =1.6mm 1/8"=3.2mm, now I know this makes your 5/16" 8mm a whole 0.0625mm different, but as a rule of thumb it seems to work for me.
Grendel

[Antipodean]

Well, my wife has proved she cares about me. I mentioned to her last night I need to go to the office supply store to look for the appropriate measuring sticks and she just turns around and magically produces a 30 cm ruler from her desk and hands it to me.
Now I can forget the inches and get back to reality.
I have enjoyed reading your posts though folks, I have learned a lot, mainly I have learned to make sure my stuff is packed in marked boxes when we move house.




Grendel, a quick question for you. Wouldn't your method cause problems over longer measurements?

[grendel]

yes but I just use it up to 1" after that its 25.4mm per inch, 304.8mm per foot, one of the good things about being a draughtsman from board to CAD is that most of the standard conversions I can transpose without a calculator for scaling I also work from a standard scale line, draw a line at an angle from one end, then measure a set measurement that you want the original scaled to, then connect that point to the same measurement on the scale, parallel lines to this line convert from one scale to the other.
Grendel

[Antipodean]

After a few starts and stops I have got the keel drawn up, this thing will be a beast if I can build it. 1570 mm long  430 mm wide.
I know the only thing , besides SWMBO , that can stop me is sourcing certain parts eg. a 4 1/4 inch 4 blade propellor.


I do want this boat as I am drawing so I will work something out.
Removable ballast and batteries will be a good idea.

[warspite]

yes but I just use it up to 1" after that its 25.4mm per inch, 304.8mm per foot, one of the good things about being a draughtsman from board to CAD is that most of the standard conversions I can transpose without a calculator for scaling I also work from a standard scale line, draw a line at an angle from one end, then measure a set measurement that you want the original scaled to, then connect that point to the same measurement on the scale, parallel lines to this line convert from one scale to the other.

ooooooo I remember doing that - those were the days