"Air draft? We don't worry about stinkin' air draft."
The folks on the AICW may find a transit speed of 6K as their norm if they have to get a bridge open , as the bridge tenders usually wait for transiting packs of sail boats .
Air draft played a role in my decision to refit my Willard 36 and move it to Florida, and in the design of the hardtop to keep it low. When I moved to Florida, I was certain it was go-fast country. No place for a slow trawler. But then I spent some quality time aboard a friend's Horizon PowerCat 52 with a 28-foot air draft. Leaving aside fuel burn, she's capable of almost 20-knots which goes to zero at majority of bridges on the ICW, and 6-kts in the many, many no-wake zones (St Pete FL). Plus he tapped bottom a while back which cost several thousand dollars in prop repairs.
My takeaways that brought my displacement trawler into play for Florida, at least in my mind:
1. If I remove the mast on my W36, I could fit under vast majority of the bridges. Goal is Loop ready at 14'6". Means I need a davit crane for the dinghy, and went with Nick Jackson pipe davit.
2. 6-1/2 kts without pause is about the same as 18-kts that slows to slow-bells in no-wake zones; and to zero at bridge openings;
3. Hard-top enclosure. I really doubt I will enclose the space. I may provide forward Isenglass for the massive rains we get around here, but that's about it. Breezes are adequate for us. Only question mark are mosquitoes. Hoping a ThermaCell will resolve.
Point being is that bridge clearance was an important factor for me in the design of my hardtop. Water draft was an important factor in deciding a displacement trawler made sense in skinny-water country like Florida. My Willard draws just under 4-feet, about the same as my friends PC52. Difference is my boat has a well protected prop so I am perfectly comfortable nosing into 4-foot waters with precautions (taking into account tide, sand bottom, etc.). My friend starts twitching at about 10-feet, with palpitations below about 7-feet. At 6-feet depth, his knees give out and needs oxygen to keep from fainting (slight exaggeration, but you get the idea). That's a huge advantage here.
Apologies for the thread diversion.
Peter