Designs of catamarans not in metric but SAE

I just bought the design from team scarab siren 8.4 catamaran. It is a beautiful design. I would build it if I spoke metric. I am a carpenter and cut wood every day. It would be much more efficient for me if the plans were in inches . Can any one suggest a designer for me? I am looking at a catamaran in 27' to 30' range thanks. Also would like to build the hulls upside down to simplify construction. Thank you

 

I am the opposite - I find metres so much easier to use than feet and inches!

I am sure that if you get yourself a good metric measuring tape you will quickly realise that a dimension of (for example) 21 7/16" is very easy to measure when it is 545 mm on the metric tape.

I think that you will find that most plans nowadays (apart from those from some American designers) are in metric rather than imperial units.

 

I am sorry, but your reasoning is flawed.

The hardest thing for me was finding a two sided metric tape.

But oncd you accept 25.4mm is an inch; you quickly realize 25 divisions is better than 32 or 16. Instead of accepting 1/8" error or 3mm, I went down to 2mm as 1/16th was impractical.

The metric system is far easier.

755 mm, for example is 29.725 inches, there is no person who wants to use sae and try to draw 29.725 inches

My metric starrett tape, on the other hand, was junk. Like I said, two scales when I only wanted metric, and a lousy tab that held onto nothing well..

If you need some semblence of sae measured; you just make a standards board in your shop with the comparisons; to help you learn and become proficient.

 

If you have a mobile phone there are very good conversion apps that will turn millimeters into inches eights and sixteenths.

I was young when Australia moved from imperial to metric. Always hated metric and as an engineer there are good reasons why it is garbage, but our world is run by politicians and paper shufflers who can't divide by 12 or 16....

There are older plan sets that were dimensioned in inches but more modern designes tend to have better proportions. RK's siren is a good example. You don't need to be accurate to a thou. Cut a tad oversize and fit each piece with a block plane. If there is a gap just fill it with a paste of wood flour and epoxy. Provided it's not more than 1/16 it will be fine.

 

I think it will be quite a lot more difficult to locate modern designs that aren't metric based.From a designer's point of view it would be a peculiar decision to offer plans that are dimensioned in a system that is only used in Burma,Liberia and the USA.The potential market is much larger for SI based countries and their sailors.Which makes it a lot less likely that those of us outside those three countries will have any familiarity with current Imperial based plans.

 

Metric https://proanaut.blogspot.com/2023/06/metric.html

 

John Marples is a good designer that's plans come in imperial measurements.

 

If you are going for a marples design he has chines hulls and he has the constand camber hulls. The latter use door skins which are not as cheap nor readily available as they once were. I suggest you look into that before committing to a design.

It really isn't that hard to go through your Kendrick plan and write each measurement in inches eights etc.

 

One thing that occurs to me re this discussion is COST.
The scarab plans are cheap - i believe $2/300ish ?. To go to any other design will probably cost you $2000
A lot of boat can be had for $17/1800 dollars.
So it would make sense to learn metric & spend your dollars wisely ?

 

Have a chat to Kurt Hughes on multihulldesigns.com he can do the design in either standard and full size patterns or dxf on request, great to work with.

 

There are two easy solutions:

1. Buy a metric tape and if the plans say, for example, 3.2 cm simply measure that.
2. Divide all dimensions to convert to inches. This introduces rounding errors.

 

When I was a plant manager we would get plans and blueprints in either metric or inches, the entire crew would rather have metric plans.

While it did take a day or two to convert from one to the other in the beginning, it soon became effortless. Measuring, cutting, checking, adding, subtracting, all of it was easier on metric blueprints.

 

I did all conversions for my Kraken 25 trimaran by factoring out an inch as 25.4mm. Makes it easy 12" to a foot so 12' became 3657.6mm, 25' became 7620mm etc, second nature after a while. It's a measurement system not a straight jacket, I like the suggestion of a metric tape or you can get a hybrid with mm and SAE marked together.

 

These a few you tube vids out there about traditional south pacific boat building.
They use a piece of string and fold it multiple times to get their measurements.

Just pace out how long you want the boat, cut a piece of twine to match - then fold that string heaps to get the fraction you want.
The scale may be off a bit, but the proportions will be correct. I'm no mathematical wizard - but pretty sure metric cant do this.

 

Any tradesman does that on a regular basis. I can work in both systems. Further, I never said metric is garbage. I appreciate you not putting words in my mouth. A design made in standard units will convert to b@st@rd units in metric, which is a nightmare for a shipwright.