Super STOL Floats?

[Dave Krall CFII SEL SES]

I don't think you want the bouncing action of the airframe separate from the float. I don't have a lot of float time, but I think you pretty much want the floats and airplane to be pointed in the same direction at all times. If you have the suspension between the two, as you hit waves, or just trying to get on a plane or when you touch down, the bows of the floats could end up not parallel to the fuselage, and I can envision a situation where an oscillation would occur between the airframe bobbing one way and the floats trying to catch up and bobbing out of phase, possibly becoming a catastrophic situation and ending up on your back. I know when mounting floats on a new design the angle of incidence of the float can be kind of critical to performance, and suspension would not allow a constant angle. Also, during step turns, you can put a HELL of a side load on them (you can turn a float plane faster and sharper than you would EVER even THINK about turning a land plane), and if the plane were allowed to "lean" due to shocks, it could be a bad day real fast.

I don't know this for a fact, I have done just enough float flying to be dangerous. I WILL say I have never seen a float plane with suspension-mounted floats. It may have been done, but I've never seen it. I have seen planes from cubs and 172s to the last (only) DC-3 on amphibs, Beech 18s on straight floats, and my wife got her MES rating in the only Apache on amphibs in the world. Plus all of the cool stuff at the International Sea-plane fly-in in Greenville Maine. Not one had suspension mounted floats.

What your saying makes some sense for conventional seaplanes, especially with rigid floats. SS planes are at the edge of the known performance envelope, landing slower and it could very well be useful to have a limited amount of shock absorption to prevent bending of the forward struts at their attach points.

The inflated Full Lotus floats themselves are very shock absorbing and have the benefit of absorbing rougher water landing hits without strut damage however the absorbed energy must be dealt with in the following bounce at very low airspeed....

[danerazz]

My thought (and I don't know for a fact by any stretch of the imagination) is full-lotus floats flex and rebound a little, but they are still "rigidly" attached to the airframe. If you attached floats to the suspension of an airplane, they could pitch (and the floats as an assembly could roll) independent of the airframe unless you could get the back and front of the floats to move in unison in relation to the fuselage so they stayed at the same angle of incidence to the plane. I see this as very undesirable at any speed and can picture it becoming a divergent oscillation.

Then again, it might work great!

[Dave Krall CFII SEL SES]

My thought (and I don't know for a fact by any stretch of the imagination) is full-lotus floats flex and rebound a little, but they are still "rigidly" attached to the airframe. If you attached floats to the suspension of an airplane, they could pitch (and the floats as an assembly could roll) independent of the airframe unless you could get the back and front of the floats to move in unison in relation to the fuselage so they stayed at the same angle of incidence to the plane. I see this as very undesirable at any speed and can picture it becoming a divergent oscillation.

Then again, it might work great!

They flex just about as far as you will bend them before permanently distorting the stiffeners, well over 18 inches. And they can rebound a lot, as in landing on a pair of giant superball material type floats! (checkout Akavidflyer's little bounce story on seaplaneforum.com....)

FLF are typically rigidly attached, often with the same brackets as conventional floats. They do sell a tubular bracket meant for the 2" tubes to go right into as well.

Results in experiments in float strut shock absorption would depend highly on the amount of travel in the shock system. A little travel in a stiff shock meant primarily to prevent structural damage in rough water landings might work well but, a longer travel shock with less resistance might allow entry into the nasty scenarios you mention above.