Float design for performance - some concepts and experiences

skywagon8a said:

Here is a sketch of some representative miscellaneous bottom shapes. We can reference the sketch number as part of our discussion so that we all are speaking of the same shape. These in no particular order.

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#1 Flat bottom.. more lift for getting on the step. Best in very smooth water. Takes a beating in rough water. Sometimes sticks to the surface and will not lift off from glassy water, works better with a small ripple to break the surface.
#2 Nearly flat with double curved bottoms. EDO's initial attempt to correct #1's issues. Was an improvement but still had high impact loads.
#3 Single curved section tends to smoothly roll the water sideward.
#4 Medium sloped flat skins, simple cost effective construction, a compromise for most water conditions.
#5 Deep V shape is best for rough water in that it pushes the water to one side while slicing through the waves. Low impact loads. Tends to ride lower in the water so requires more power and speed to lift off.
#6 Same as #4 with the EDO style boosters for more lift while on the step.
#7 Double fluted stretch skin provides the best combination for most water conditions. More expensive to manufacture.
#8 Like #5 with PK's version of booster angles.
#9 Like #4 with a booster on one side (for illustration) and chine spray rails just ahead of the step. The spray rails assist in capturing the side flow of water while climbing on the step in order to increase low speed lift.
#10 Similar to #7 with a double keel. Perhaps helps with low speed lift.
#11 (no time now need to edit this post)

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You missed EDO 1140 ald 1320 bottoms



Glenn

cubdriver2 said:

You missed EDO 1140 and 1320 bottoms

View attachment 62424

Glenn

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I thought the 1320s were like #7? Never really looked at the bottoms. Those are like #3.

Here's an installation print for EDO 1320's on a L-4/J-3. My 1320's were built for an L-4 and later converted to Taylorcraft fittings. The single Data Plate is inside the right forward float compartment. They look similar to #3 above with a gentle concave surface. The displaced rising water gets gradually turned and exits the chine parallel to the waterbody's surface, then turns up and away from the float. That's their secret (and later Baumann's copies 1420 and 1500 models)

https://archive.org/details/piperj3_Bin_368_60-S-908A_J3_Edo_1320_Float_Instl/mode/1up

Gary

BC12D-4-85 said:

Now another couple of questions please. What about the shape of the float bottom aft of the step? Best duplicates design forward of the step?, or is #4-5 just ok? Any reason for boosters back there?

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The only reason for the section of float behind the step is to support the airplane while it is at rest and during slow taxi in the water. Likely the most favorable shape for the aft bottom would be #3 since it would gently turn any water outward without much in the way of impact loads. Also for tail low landings the water would be spread sideways. If it were a flat bottom, you could get a abrupt nose down reaction which would be desirable.

And what about ease of step turns with the designs above when you have the time? A CAP owner ran aground again recently with CAP's presumably turning on a river (not sure yet).

Gary

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Step turns, particularly on one float would have less opposing drag with #4 bottom. The others have a sharp edge which would grab the sideways flowing water thus retarding the rate of turn. Of course you must be careful not to overdo it. I'll not attempt to instruct in step turns on the internet. Someone is likely to get in trouble.

#4 above looks like EDO 1400-1650-2000-2130's? Flat lines for the deadrise keel to chines.

Gary

BC12D-4-85 said:

#4 above looks like EDO 1400-1650-2000-2130's? Flat lines for the deadrise keel to chines.

Gary

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All were modified to #6 for the extra lift from the boosters. Not certain about the 1400s?

^^^^Yes I missed that booster addition. #4 was the original EDO 1400 design, but as noted in #1, they performed poorly until EDO later added the boosters per #6's design.

Now for a few pictures of local floats when I get them. Wipline and Baumann did it right as we shall see (Edit: for Cub sized aircraft at least).

Gary

I have to make some observations about float bottom #1. A local J-3 aficionado bought and installed a set of Greenwood fiberglass flat bottom floats on his J-3 ..... they had no step. A wide flat bottom full length of the float. He said they were approved though I never saw the evidence. He had me fly them. They would get up on plane, then the pitch attitude had to be precise. Too far forward and it would porpoise, too far aft and it would skip/porpoise. Rotate to liftoff, it would skip/porpoise. To lift off you had to jerk it quickly or it would (you guessed it) porpoise. Landing was the same in reverse. Either porpoise or skip unless the angle between the bottoms and the water was just right. Well, he was enjoying it for a few week when on one landing the bottoms ripped right off the floats. I still have doubts these were FAA certified though he insisted they were.


The very first seaplanes prior to WW1 used a front float and another at the tail. The front float was in the location that our current floats are from the step forward.

This is well written on characteristics of seaplanes.
https://www.flytheshark.com/guide-to-seaplane-flying/characteristics-of-seaplanes/

My Baumanns are from 05’ so not sure why the ones from 07’ didn’t have them��*

Glenn Curtiss did all the early float research. One of the smartest man alive back then. And ball as big as coconuts

https://glennhcurtissmuseum.org/education/who-was-glenn-curtiss/

Glenn

Here's a start of pics of some of the local floats Cubs and similar types might use. The reason for this is these tend to get woven into other threads and are hard to dig out if interested. If this thread takes up too much bandwidth with pics let me know and I'll remove some.

First are the MCW 1850's for PA-18S-150 STC SA1099WE. I've never flown or seen them in action but was told they do well. Basically molded composite (fiberglass) with metal edging. Don't know the weight. The round tubing structure might slow things down.

Gary

Here's Aerocet 2200's https://aerocet.com/products/2200

Gary

Here's Wipline's 2100's https://www.wipaire.com/wipline-floats/wipline-2100-floats/ Note the tapered booster, flat V bottom in front of the step, and a concave V bottom aft of that.

Gary

And here's Baumann BF2100's The owner is pleased.

Gary

Finally but not the last for any reason are the proven EDO 2000 bottoms. The most common in this part of the woods.

Gary

The Baumanns were the best performing float on a Cub/Husky/scout size airplane, at least before Aerocet came out with their 2200s. Too bad Basler bought the company and ended all production.

MTV

Tell you what,, been parked on the south shore of Lake Spenard since 1985. I have watched thousands of ops on and off the water. It's almost never the float that is the performance factor. My neighbor had low hours, a beautiful cub on baumans. I loved the big hatches and flat top. But John in his maxed out Goose would do better getting in the air. He has since moved, haven't seen his cub around the lake in a while. Hopefully he got it figured out though.

A good tight set of Edo's rigged well with the fairings on the spreader bars is hard to beat. Quiet, and quicker at everything. Take off those tear drop fairings and you loose speed, add noise and splash more water. There is something that changes the spray pattern. If you watch a cub with edo 2000's and hatches, water from between the float will kind of boil over the float hatches and soak the top of the float. With the fairings only back compartment seems to get wet. Not that it never happens, its just usually turning in a strong wind or something, or taking off with whitecaps. But on a calmish day, it doesn't throw water as much when you push the throttle forward and get on step.

Putting a little wax on before they go in the water helps performance too.

At a minimum it makes the lake hood line scrub off much easier.

There's no doubt that EDO 2000 floats are simply some of the best floats ever built, at least for small aircraft. And, there are a LOT of them around.

You are absolutely correct also that there is some requirement for the pilot to participate in the process of getting airborne. Not all do much to help for sure. And, frankly, the EDO 2000s are some of the "friendliest" floats for pilots....they really don't have any bad habits and technique required is pretty minimal....not absent, mind you.

My experience with the Baumann floats began when we traded in a Model A-1 Husky for a Model A-1B. The B Model Husky was not initially approved on EDO 2000 floats, for reasons I don't pretend to understand, but the Baumanns were. We put that first production B model Husky on those Baumann floats, and they were magnificent! Takeoff performance was excellent, huge hatches with no noted weight limit.....seriously, and they were really fast through the air. As we acquired more Huskys, other float models were discussed, particularly Wipline 2100s. At one point, I took the Husky down to ANC and we put an almost identical Husky on a set of Wip floats. Three of us then each flew each airplane, in side by side takeoff performance trials.....after an appropriate period of practice for all involved to figure out each float. What we found was that takeoff performance was pretty close, with the Baumanns out performing the Wips consistently, by a relatively small distance: Between 50 and 100 feet, but mostly really close to 50 feet.

The Wip floats also had nice lockers, though placarded for weight, and were really nice floats. The Baumanns were a bit faster in the air....between 5 and 7 mph. These planes both had electronic tachs so were making comparable power, but there's a possibility that they were rigged a bit different. That said, I've always felt that the Baumann floats were fast in the air. They are kind of short, stumpy looking floats, which always puzzled me, but they work.

Nowadays, I suspect the Wipline floats and the Aerocets are the hot ticket on a Husky or Scout.

MTV

Good point about the driver having some skin in the game. Getting there takes time of course, and doing lots of different loads and conditions. Not going to get at that level fresh out of a rating. Unfortunately many just fly for fun, and aren't tasked to get stuff from here to there which becomes The School. Also I suspect MTV and maybe others are what amounts to a very limited instructor base when it comes to reality float flying. Find them and learn.

Edit: As far as performance between floats I've considered them to be a tool to get around on water. I like using the best tool for the job if possible and affordable. As far as cruise there's always some consideration for that but it's been 2nd on my list.

Gary

Interesting comment about the spreader bar fairings for the EDO 2000’s. I’ve never seen any close up. How are they attached? Are they something that can be purchased and put on?

Do the “spray rails” commonly put on 2000’s have any performance attributes, or are they mostly to help keep water out of the prop? Seems like they might help push water under the float, but I’ve never been able to watch them in action.

Jim

Found this older thread on Float Performance which I missed earlier. Never too late to take prompt corrective action when I screw up (my former supervisor used to tell me). Have a read there and maybe combine the ideas and experiences>

https://www.supercub.org/forum/showthread.php?45418-Best-Performing-Floats

Gary

55-PA18A said:

Interesting comment about the spreader bar fairings for the EDO 2000’s. I’ve never seen any close up. How are they attached? Are they something that can be purchased and put on?
Jim

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See P/N 43 pics. Used to be made from a molded semi-flexible plastic-like material. Painted silver that with time and a lack of maintenance (paint) would turn white and slowly disappear off the floats. Water can intrude and freeze during cold weather if no low point drain established. Riv-nuts or similar were installed into the floats and the fairings screwed on. Stepping on them results in eventual destruction, but they likely help performance both on and off the water.

Gary

55-PA18A said:

Interesting comment about the spreader bar fairings for the EDO 2000’s. I’ve never seen any close up. How are they attached? Are they something that can be purchased and put on?

Do the “spray rails” commonly put on 2000’s have any performance attributes, or are they mostly to help keep water out of the prop? Seems like they might help push water under the float, but I’ve never been able to watch them in action.

Jim

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I'll have to look, but there was a company out of canada selling them. Took a bit of work to split them and get them to fit good. Screws and nuts hold them on.

55-PA18A said:

Interesting comment about the spreader bar fairings for the EDO 2000’s. I’ve never seen any close up. How are they attached? Are they something that can be purchased and put on?

Do the “spray rails” commonly put on 2000’s have any performance attributes, or are they mostly to help keep water out of the prop? Seems like they might help push water under the float, but I’ve never been able to watch them in action.

Jim

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Check with Kenmore. They were included as a separate kit with all 2000s and 2130s which were shipped after at least 1970. https://www.kenmoreairharbor.com/contact-parts.html

They are installed using AN526-C-832R6 screws (72 pcs.) and C-7000-832-C Tinnerman (56 pcs). 16 AN526-C-832R6 hold the 40122 splice plate which joins the two sections under the spreader. This information comes from EDO drawing #40119. As I recall there are pilot holes in the fairings. Be certain where you drill the holes that you have clearance inside for the tinnerman. Some of the pilot holes are too close to a hat section inside the float, so you may need to move the hole a little bit.

The only negative issue in using them would be if you operate out of salt water. They could trap enough water to start corrosion.

An example of #10. I did a poor job with this sketch.

The Seamaster amphibious floats were made in Renton Washington with a double keel. These floats had a rectangular aluminum box with a fiberglass bottom and side sections. At the time only Wipline had a similar sized amphib. The Seamasters were approved on the 185, 206, Helio and Cherokee six. How many of you have flown a Cherokee six on floats? It's a nice flying floatplane. Too bad the low wing interferes with docking etc. Unlike aluminum amphibs with thick keels, these floats can only make one landing gear up on pavement. Later EDO wanting to build an amphib larger than their 2790s bought the Seamaster and marketed them as the Dolphins. These floats couldn't take the abuse in a working environment of rough water. There was at least one in which the side section ripped off. Thus EDO scrapped the Dolphin and developed their own 3500 amphib.

Also the Seamaster had a terminal velocity on the water. This speed was just below the speed needed for a 206 to fly. So it was necessary to use normal seaplane take off trickery for all takeoffs. These floats are better suitable for a Helio than for planes with higher stall speeds.

These fairings are on my 2960s.

You are missing the strut's fairings.

kg said:

View attachment 62455These fairings are on my 2960s

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Are you aware these fairings were developed on the Piper Comanche? Piper used to put everything on floats. The Comanche's speed was not very impressive, thus they underwent a speed improvement program which evolved into the fairings which EDO then included with the 2790 and 2960 floats.

skywagon8a said:

You are missing the strut's fairings.

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I see.. this explains the reference above about stepping on them.

This was my first summer on floats. This thread has been very informative for me! Thanks!

kg said:

I see.. this explains the reference above about stepping on them.

This was my first summer on floats. This thread has been very informative for me! Thanks!

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There should also be a set of spreader bar fairings on the outboard side of the floats covering the ends of the spreaders. The same as the ones you have shown without the big hole in the middle.