Scale

Thank you everyone
I've already drawn this hull at 3/4" in several revisions, done offsets twice and never been able to get dimensions closer than 1/2" for offsets.
I've lofted it once and it seems pretty close to the offsets, within 1/4 of an inch.
One of the problems with 3/4" scale is that the sail plan won't fit on 24x36" paper. I'd hate to change scales for different perspectives.
The other problem is I have several plans from Atkin and Alden drawn in 1/2" scales with offsets in 1/8 ths +or-. How did they do it???

 

As I said before, measure inside to inside. If it exacty splits the white space between the 0 and 1/2" ticks, it's 1/4". If it is real close to the 0 but beyond the mark it's 1/8-, a little bit further out 1/8, not quite to the exact middle 1/8+. It is easy if you do it enough and understand that the last 1/8th is going to be covered by the paint anyway....

 

I can loft in the method that I described (foreshortening) and read 1/16" on 11" by 17" paper easily. You just have to be open to the suggestion.

 

Chandler
The answer you are looking for is to take your offsets to a tick strip. Take the tick strips and measure them with a verniers micrometer. Take the readings and convert them to scale....This should easily give you accurate readings to 16's or 32nd's if you desire. Hope this helps.
I know what you mean, it's impossible to try and determine 1/8ths of an inch from any type of scale.
Chandler

 

I have a similar problem as imperial scales appear unvailable in HK. I was planning to use a computer conversion program and translate into metric or buy a conversion calculator. I believe I saw one advertised on the internet. does anyone see any problems in this Idea as I am more at ease with metric when scaling even though Aussie education taught me in imperial? I still use a dual measuring tape and if a measurement is exact in inches my eyesight prefers to use inches. I guess I should buy a digital tape measure sometime.

 

You can buy a pretty basic scientific calculator for $ 10 or $20 that has some memory ie. store reclaim that makes any type of conversion pretty painless.

 

Download it here:

http://www.consoft.de/Default.aspx?art=multicalc

Do´nt use the currency converter, is never up to date. But Multicalc is very handy for SI unit conversion.

Regards
Richard

 

In light of all that has been said --- it still comes down to the loftsman to complete the design process and the nav arch to confirm what was done meets the requirements of the design.
Sooo - it doesn't matter what scale you use, when it comes time to fair the boat, draw it full size on the loft floor and if you need to, re-input the values back into the computer for your nesting of plate or correct sizing of carbon fiber fabric, etc., etc., etc.

 

It gives me a warm fuzzy feeling to think that people were using pencil and paper that recently.

 

People are still using paper and pencil

 

If you have an Internet connection near where you are doing your paper work, you can look here:

http://www.onlineconversion.com/

As a computer programmer, at one point I was deeply offended by the fact that people used pencils at all. Even worse, I found myself using one constantly. Not even a pen, mind you.

Now I use that as a measure of application usefulness. If you turn the computer on in order to solve a problem, then FINALLY the computer program is more useful than a pencil.

It seems to be such a humble measure of success.

 

fractions are exact 1/1 of the time. you can't say that about decimals.

 

Poida, on metric vs Imperial:

There's little difference between the metric and Imperial systems and I use both. It is easier to do calculations in metric. Boat designers do lots of calculations, boat builders not so much.

I have a foot (sorry) in both camps; when designing I may think and calculate in either decimal feet and pounds or meters and tonnes. I'll draw at a scale of 1 cm to the foot if it suits my purpose. But I (have my computer) convert to feet-inches-sixteenths to build, every time.

There's a good reason for that. I'm less likely to make a mistake finding the mark in Imperial measure. In metric I have to find the meter mark, then the centimeter mark, before I can tick the millimeter. In Imperial I have to find the feet, then the inches, then the sixteenths. So far so good, no functional difference. On a short rule on a sheet of paper, who cares?

But take a look at the scales on a tape measure! Because there are 2.5x as many numbers on the metric scale the letters are smaller, the nearest meter number is 3x further from the mark than on the imperial scale and I can have trouble spotting it. Then it's harder to find the decimeter with 100 to chose from in each meter than with only 12 inches to the foot.

The Imperial system is based on the practical needs of folk who make stuff. The metric system (SI if you must) is based on the practical needs of folk who work at a desk working out taxes and scientific stuff.

Them neat digital readout tapes might solve the problem, haven't tried one yet but that might get me to shift to the metric system exclusively. It's nothing to do with being an ex-Brit!