Weight gain is established by saturating the specimen in a moisture environment. Relative humidity of 85 to 95 percent is typified. The specimen is weighed initially and then periodically until there is no more weight gain. This process can be accelerated by introducing heat. In all the varied composite materials tests, utilizing fiberglass, there has never been shown more than a 1.7 percent weight gain. Typically, weight gain is 1 to 1.5 percent at 95 percent humidity.
Another fascinating thing is that when the specimen is subject to dry air, the weight gain goes out at the same rate it enters. In other words, if it took 90 days to achieve full saturation in the humid environment then it will take another 90 days to lose this weight in a dry environment.
So what does all this mean in regards to fiberglass floats? Let's look at the numbers. Being that the actual fiberglass portion of the float assembly weighs 340 lbs. per set, typical of a 3500L, then the total weight gain potential would be 340 x 1.7% = 5.78 lbs. This assumes that all the laminates are totally wet. We know that not to be the case, a fair amount of the float is above water, so the number is conservative.
The fiberglass portion in an amphib is 20 lbs. more, taking the number to 6.12 lbs. possible weight gain. It should be noted that amphibs typically don't stay in the water for any long period of time, so the numbers will be less.
We should always be comparing apples to apples. The Aerocet 3400 amphibs are designed to handle aircraft with gross weights up to 3775 lbs. They incorporate the displacement and the landing gear strength accordingly. We also go to great lengths to keep as many of the hydraulic lines aluminum versus rubber flex lines for weight savings and to avoid service issues.
Isn't it funny that comparisons are made by the competition not telling the complete story? An example is weighing our floats with double steps and theirs without any. They don't talk about the weight of additional hardware(interconnect system between the rudder and ailerons) and flying surfaces (larger rudder) they need to make their 182 capable of passing certification. Overall weight differences should always be compared apples to apples looking at the complete installation and size equivalence.
It should be noted that around the first of the year, in 2006, Aerocet converted their laminating process to a new method called infusion. As a result there is almost no element of weight variance. This allows us to achieve consistently light parts typically beating the posted weight affidavits.
One more thing, Aerocet floats are tough. Unfortunately, people do stupid things and engines break. We have seen over and over where the floats have saved people lives. One situation was landing a Cessna 185 in sharp six foot waves out in the open coastal water with temperatures barely above freezing with a broken crankshaft. The floats didn't break and the three aboard the plane were rescued. The plane was destroyed in the retrieval process. Had the floats failed they would have only had about 20 minutes in the water. The rescue team didn't get there for 40 minutes. Aerocet received a call the next day thanking us for the strength of the floats. These same floats are flying commercially on a Cessna 206 today in Alaska.
Another case is where a person up off of Vancouver, B.C. stalled a 185 in some sort of a strange wind shear at over 30 feet up. The plane came down so hard that all the struts broke off at the aircraft. The rear struts penetrated the cabin and brushed the pants of the rear passenger. The plane came down and crashed into the spreader bars, bending them in a dramatic fashion. The floats held together on all the seams and were still floating the occupants who had very sore backs but survived fine. An observer who saw the incident could not believe how strong the floats are and how they kept this plane afloat. Weight versus strength is always a balance.
We have also implemented a rip-stop bottom laminate structure. By changing the bottom fabric over to a knitted design we were able to orient the main outside fibers to all span chine to chine (side to side). What this does is stop any damaged area from peeling back in layers under hydrodynamic force. A tough float is now even tougher.