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Flotation Exemption to Expire

keys2pines

Well-known member
So after July 2024, won't have to worry about pulling a new boat off the bottom of the canal or lake? Where's the fun in that?! Hopefully the boat manufacturers will be able to comply without adding crazy weight to the boat.
 

OneBFC

Well-known member
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.
 

Slidin Gator

Well-known member
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).


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.
 

JLP3314

Well-known member
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.

I'm wondering if that could be achieved in another way?
Say something similar to our automatic PFD's or emergency life rafts that inflate when they hit the water?
Dang sure throws me a curve ball wanting to start a build...

Edit: So much for my idea as it specifies FOAM!?
 

Slidin Gator

Well-known member
Edit: So much for my idea as it specifies FOAM!?
The rules also allow for sealed chambers vs foam but requires that the boat meet the requirements with the 2 largest chambers flooded. Gil Brackets on offshore boats is one example of a sealed flotation chamber.
 

Trapper510

Active member
Flotation is a little more than the bow out of the water. There are 4 different tests the hull has to pass for flotation.
Some major builders dont even pass them all the time. Fairly intense testing
 

Slidin Gator

Well-known member
Flotation is a little more than the bow out of the water. There are 4 different tests the hull has to pass for flotation.
Some major builders dont even pass them all the time. Fairly intense testing

Trapper,

You are referring to the Level Flotation requirement for outboard boats, which is definitely more stringent. I am quoting direct from the CG link that Ole Yeller posted at the start.

1.0 APPLICABILITY
The flotation regulations apply to monohull boats less than 20 feet in length, except sailboats, canoes, kayaks, inflatable boats, submersibles, surface effect vessels, amphibious vessels, and race boats. The word “regulations” (plural) is used as there are three flotation subparts applicable to three classifications of boats. Following is a summary of the applicability by boat type and subpart.
Subpart Boat Type Flotation Required
F Inboards, sterndrives, and Air Boats BASIC FLOTATION
G Outboard Boats Rated for More Than 2 Horsepower LEVEL FLOTATION
H Outboard Boats Rated for 2 Horsepower or Less and Manually Propelled Boats MODIFIED LEVEL FLOTATION
Monohull inboard, sterndrives and airboats less than 20 feet in length must comply with a flotation system called Basic Flotation. Basic flotation is the simplest type of flotation mode. It simply requires that the boat be manufactured with sufficient flotation material to keep it afloat in the event of a swamping. It does not require that the boat remain in an upright or in any specific position. It may float, and usually does, in a “spar” position, the bow sticking up and the stern sunk. Many sterndrive boat builders opt to provide flotation material to meet a higher standard.
 

Trapper510

Active member
You are correct but during the test to get a passing certification the boat must float fully submerged no more than 6 inches total. There are 4 separate tests done.
1 with 100% rated capacity in the center 40% box. 1 on either side with 30% capacity in the 30% boxes and then a total submerged test. The boat must not capsize in the 2-30% tests and only list a certain angle. The full submerged test shall sink no more than 6 inches below the surface. This is the one that allows for ejected passengers to hold on to until rescue. Not an easy test to pass and some major boat builders have boats that do not pass.
Flotation has to be placed properly for and aft to have a chance to pass the coast guard test. If you have ever watched the tests performed it is a intimidating operation for a boat builder.
 

Slidin Gator

Well-known member
Trapper,

I disagree, you are describing Level or Modified Level Flotation, which any airboat/sterndrive builder is welcome to meet if they wish (but are not required to) vs. an outboard boat that is required to meet. if you have specific requirements to reference, please post.

The quote above says an airboat may float in the "spar" position, which means grass rake pointing up. How would that equate to cage 6" from the surface?
 

Trapper510

Active member
You are missing the point and are quoting the old regulation that is going away In 2024.
I just had a long discussion with the coast guard inspector for my area 2 weeks ago on this very subject and the exemption being removed from airboats and mud boats and the reason behind it. The new guidelines are forthcoming and we will se how it works out. For the time being we will just be on 2 different pages. I will continue to follow my direction and you yours. You build boats to sell the way you want and I'll do the same.
No hard feelings.
 

Slidin Gator

Well-known member
You are missing the point and are quoting the old regulation that is going away In 2024.
Now I understand, thanks for clarifying. I completely understand the implications of the Level Flotation requirement on a top heavy airboat. Would hate to have to make the cage out of foam!

I don't build boats to sell, I spend enough time building and rebuilding the stuff I tear up.
 

Trapper510

Active member
Yep there are going to be a lot of builders going back to the design board to get their boats to pass the flotation process. Going to an interesting 2 years and how they coast guard applies them to airboats. They are a different animal and the only way my wife will travel these rivers.
I have added flotation to my hull but that's just for our safety in these waters we run. Much different than we ran in Louisiana. Deep and fast.
 

JLP3314

Well-known member
Is the USCG trying to put all the small boat builders out of business by 2024 then?
Sure seems like it if all the boat have to conform to that criteria!
I can't ever see an airboat being perfectly balanced to float upright with folks hanging onto the sides, (just due to the dynamics of how airboats have to be built to perform and plane out in deep water).
 
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