Portland Course Plotter Navigation Divider Marine Nautical Protractor

Standard nautical nav plotter. You can spin the center part around to have the variation so you don't have to do the math in your head. The only thing slightly confusing is that it would appear to me that the variation scale is labeled exactly backward, but if you think about it, it's easy to set it right.

Wanted to love it but couldn't. It may have been a fluke, but mine arrived with a misaligned washer that tipped the rotating dial away from the baseplate and skewed course/bearing readings. I may have been able to fix it, but that shouldn't be necessary and I don't know that it would stay aligned. Given its size, heavy weight, and the spotty state of the paint on a new plotter, I returned it and found a better lexan option from an aviation shop.

Received over-priced product assembled backwards. If I were someone new and just learning Im sure this would create alot of unnecessary confusion. How hard is it to screw on one part the correct way?!!!