Monday, February 21, 2011

1/300 Patrol Boat Project: How to Scale

I noticed in an earlier post that I didn't really answer a question about how I scale down the boat plans using a copier. I thought I would just post it rather than add to the running comments, which is about two weeks old.

What I do is print out the plans. I then scale them down. My boat is 30 meters long, so I am going to solve for x; x being the length of the boat at 1/300 scale.

If 1 meter = 1,000 mm, then 30 meters = 30,000 mm.

Why first convert to mm? I could have also used centimeters, but the important thing is that units must always be the same in both the numerator and the denominator. Therefore, the scale or ratio is 1 mm = 300 mm.

Now, you solve for x:

x mm/30,000 mm = 1/300

x = 1/300 x 30000 mm

x = 100 mm

So at 1/300 scale the 30 meter boat measures 100 mm or 10 cm in length.

Now, comes the reducing part. You want to reduce the drawing down to 100 mm. You measure the length of the boat in the drawing. Let's say its 15 cm long. You know you have to reduce it in size so that its length is 10 cm. You divide 10 into 15:

10/15 = 0.66

When you copy your original, go to the ZOOM menu and reduce down to 66% That should do it. It helps to have a ruler handy to make sure it is at the proper length.

I hope that helps. There are are some online scale converters to speed things up. There used to be a pretty good online calculator, but I noticed that its gone. The nice thing about this one was that you could enter any scale you want to. Others that I have seen have pre-set scales that are either for building doll houses or standard models. I wouldn't be surprised if there was some sort of app that will do it for you. Eh...its not that hard to do it on your own. Besides, its good to dust off and exercise those neuronal connection involved in algebra!


  1. No problem Jim. I realized that I never did answer your question!