Aerocet 1100 bouyancy

[mdock]

I have a set of aerocet 1100 on my kitfox III with a 582. The empty weight is at 750 lbs, which others have said is typical. My concern is that at lower power, while taxing, the nose of the floats seem to only be a couple of inches out of the water. If i let off the throttle too quickly they will actually submerge. It seems hard to imagine that these floats are really rated for 1100 pounds. Someone mentioned that the floats were rated for 1100 pounds when they were straight floats, prior to the cutouts being made for the amphibious setup. Does anyone have suggestions for improving the taxi water handling of these floats? I saw someone had a spray guard on the inside of the floats, would that help? Also, what about filling the nose bumper and wheel wells with additional foam? Any suggestions are greatly appreciated.
Thank You,
Matt

[av8rps]

Matt,

It surprises me that a 582 powered Kitfox 3 is underfloated on 1100 Aerocets. My 912ul powered model 4-1200 should be much heavier, but sounds much like how you describe yours on the Aerocets. My ew on wheels is approx 635lbs. What was your empty weight on wheels?

I personally would put the Aerocet 1100's at about 1050 lbs, and 1100 for the straight floats. But the bigger issue than total buoyancy is that the float is short, so in order to have the step properly located, there's just not enough float forward, so forward buoyancy where you need it suffers, causing the bows to bury at anything less than a very slow taxi speed. (Although you will find adding a passenger and/or baggage brings the bows up, as you are slightly shifting the cg back)

You could make yourself some extended spray rails that attach to the inside of each float from the bow to near the step. I say to make them long so they do more than just deflect water spray. If longer tbey will hydrodynamically push the bows up when you are taxiing slow, plus help push you up onto the step quicker. Id make them out of aluminum and screw them on for ease of construction. If that works like I think it will, you could consider making a thicker spray rail out of foam and fibreglass, thereby not only using the water force to push the bows higher, but you would also gain some forward buoyancy from the foam. (1 inch of foam supports a lot of weight, and I don't think you need much up there to make a lot of difference).

Another option, although much more work, would be to experiment with moving your floats forward a few inches. Or to move them ahead and to add the spray rails. Although be aware if you move them too far forward it will get squirrly on the step, more difficult to get on the step, and have a tendency to porpoise uncontollably. My gut says you can move it no more than an inch or two before causing these handling issues. But that's just my gut feeling after flying mine a bunch of years.

I say all that because my Aerocet amphibs do the same thing as yours. I've learned to tolerate it by either plow taxiing (gets the bows up), or to idle my engine slower which slows my idle taxii speed. A fast idle taxii speed is what really makes the bows bury in my experience. But ultimately I will probably one day make these changes to my floats, or swap out to a bigger float (the reason I somewhat hesitate to sell my spare set of cz 1200 amphibs).

Hope this helps.