Measuring needed overhead clearance

[BandB]

I am sure you have all considered this but does the amount of fuel and water you have aboard count!

Wifey B: Most boats vary 2-3" but some vary as much as 6" going from full load to light load. Also a few boats that have cleared in Chicago by adding weight to help them under.

 

[Benthic2]

... I would not rely on air draft calculated by geometry....

Geometry has been around a for a few years, its pretty accurate.

In 1856 surveyors measured the height of Everest from 100 miles away. They were off by 33 feet ( or about 0.1% ) That kind of accuracy for a 25 foot measurement would be about 1/3 of an inch.

Its pretty reliable.

 

[AlaskaProf]

Well, I was a mechanical engineering student for the first couple years undergrad and I can do that math, but as my radar arch is fast approaching the underside of a bridge, I'm not sure I want to rely on that calculation.

Karl,
One hopes you would do the calculation BEFORE getting under way.



Here's another useful calculation:


I have four crew members and two six-packs of Amber. It is 30 miles to King's Grocery in Friday Harbor. What speed must I make to avert the mutiny?

 

[BeeJay]

Karl,
One hopes you would do the calculation BEFORE getting under way.



Here's another useful calculation:


I have four crew members and two six-packs of Amber. It is 30 miles to King's Grocery in Friday Harbor. What speed must I make to avert the mutiny?

Hmmm....... trick question, what sort of anchor ??

 

[JoeApicella]

Best method

Find an area where the water depth is a little less than the estimated air draft. Scuttle the boat and when it sits upright on the bottom, measure the distance from the highest point to the water level. Add this to the depth and you have your air draft. Of course, in tidal areas you have to act fast to get an accurate measurement.