Will have to add 4 small wheels and then you can classify it properly for what they really are.
All Terrain Vehicle
No longer mislabeled a boat, problem solved.
ATV designation does not solve the problem by far, at least not for me. Many place I run outlaw motorized vehicles. But because it's flooded marsh land, they have to allow boats. Since Airboats are boats, Airboats are legal (let's not go messing with that).
Google "Amphibious Car Registration" if you want to see another possible can of worms that wheels open up.
This is going to really change design and handicap the industry!
It could change design for sure, particularly for fiberglass hulls, but I don't think it's a handicap, used properly the result would be stiffer hulls that run better. But in reality what the CG is requiring is not that difficult to achieve.
Following the links provided and skimming through the compliance manual I find that Airboats come under the Sterndrive classification, which only calls for "Basic Flotation". The definition from the manual is as follows, but it basically means that the boats bow has to stick out of the water.
Basic Flotation: A flotation system which will keep a swamped boat from sinking when its passengers are in the water clinging to it, provided that the aggregate weight of the motor, passengers and equipment carried in or attached to the boat does not exceed the boat’s maximum weight capacity. With Basic Flotation, the swamped boat may float at any attitude.
It basically says that the stories we see of some guy sitting on the bow of the boat for 3 days in the ocean until being found is exactly as the CG intended. For the purposes of an airboat, it means the grass rake sticks out of the water, which is much easier to achive vs. a requirment that the boat has to float right side up.
As an example, say I want to meet this requirement on my present rebuild. I came up with 2,500 lbs all in boat, equipment, fuel, riders. If I follow the letter of the rule book I could probably get the flotation requirement under 1,800 lbs (for instance, Aluminum weighs 2/3rds it's air weight submerged in water).
Here is Hull #2, got everything stripped off. Time to chisel some poly rivets, this is why we have sons, he wants one of these boats, and I need lot's of rivet etc. work done. Anyone with a keen eye will see that the rudder just had a run in with another trailer in the yard. Big "F" for...
southernairboat.com
For now, assume I need to provide 2,400 lbs of flotation so my grass rake will stick towards the sky in the middle of Lake O'. Out of all the options on how I might want the boat to float, nose to the sky makes the most sense as it makes it easy to attach a tow line to raise and refloat.
Water density is 62.4 lb/ft^3. The lowest density closed cell foam that is worth using is a nominal 2 lb/ft^3 density, I'm gonna assume 2.4 lb/ft^3 to allow for some water absorption.
62.4 - 2.4 = 60 lb/ft^3.
I net 60 lb of flotation for every cubic foot of foam.
So I need 2,400/60 = 40 ft^3 of closed cell flotation foam. That foam will weigh 40 x 2.4 = 96 lbs, let's call it an even 100 lbs.
I need to shove 100 lbs of foam as close to the bow as possible. For a 6 foot bow width with 1 foot of foam height, 40 ft^3 of foam would require 6-2/3' of foam length. So basically the front half of the boat, 1 foot deep in foam.
100 lbs, isn't a game changer and that 40 ft^3 of foam takes up a lot of cargo space. But, properly utilized, that foam can really stiffen up a hull and likely lead to weight savings on structure. I can also envision how the foam can be used to eliminate adding a cooler, etc.