Aluminum Float/Hull Plans?

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JortzysCorner

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Hi All,

I was wondering if anyone might know of a resource, or have a set of aluminum float/hull plans? I would like to design an amphibious ultralight/LSA for myself over the course of the next year. I am an engineer & work for a metal fabrication company, so the idea is to design it in CAD & then have my company laser & form most everything out of aluminum. However, I am not familiar with hull design, internal support structure, & the appropriate angles & lofting that would help the aircraft plane (non pun intended) and get out of water more quickly. I was hoping I could obtain a set of plans & use that as a reference & initital means of educating myself. Likewise, if anyone knows of any good books/resources pertaining to hull/float design, those references would certainly be welcome. Thanks!!
 

Riggerrob

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Construction drawings of all aluminum floats are available from Murphy, Zenith, etc. You can learn a lot by studying their proportions.
Even studying the basic proportions of factory floats: Aerocet, CAP, Edo, Wipline, etc. will help you understand the basics.

You can learn a lot about sea-worthiness and simplified metal construction (e.g. spot welds) by studying a Republic Sea Bee. Sea Bee plans are not available, but you can buy plans for Mr. Spencer's Air Car wood and composite, 4-seater flying boat.

The Czech Mermaid was an all-metal, 2-seater flying boat sold in kit form a few years back. Thurston Seafire is an all-metal, amateur-built, 4-seater flying boat. You might be able to find plans. Thurston also wrote 3 books about small airplane design. He includes a few useful tips that he learned while developing his Grumman G-65 Tadpole, Colonial Skimmer, Lake Amphibian, Teal, Aeromarine Seafire, etc. series of small flying boats.
NACA published a bunch of reports about seaplane tests (wind-tunnel and water-towing of models) back during the 1930s. But look at the later USN flying boats (e.g. Martin Marlin and Seamaster) for the later refinements (e.g. long hull finesse ratios).
There some basic rules-of-thumb like installing both the hull step and main wheels 15 to 17 degrees aft of the center-of-gravity, displacement double the gross weight, tie-downs strong enough to support the gross weight of the airplane, etc.

As for angles, bulkhead outlines, etc. look at the plans of the more popular wooden and composite homebuilt flying boats like: Anderson Kingfisher, Aventura Buccaneer, Avid Catalina, Aero Garr Sea Hawk/Glass Goose, Osprey, Petrel, Taylor Coot, Volmer Sportsman, etc.
You cannot buy plans for Aerodyne Icon or Dornier S-Ray, but can learn a lot about sponson configuration from photos.

If you want to study bleeding edge seaplane technology, go look over the threads on Burt Rutan Tri-Gull amphibian. But even Burt had to completely re-design the landing gear from tail-dragger to nose-wheel after he broke a ski during early testing.
Avoid falling down the rabbit-hole of hydro-foils or air-cushion landing gear as both have been test-flown and proved impractical.

I too have been sketching a 2-seater flying-boat. It is a high-wing, with sponsons/seawings to allow it to dock on conventional floating docks. The engine is a Rotax. My first calculations used a Rotax 912, but that was not powerful enough to take-off from high mountain lakes during hot summer afternoons, so the project was shelved for a few years. Now that super-charged, 145 horsepower Rotax 915 is available, I probably should review that project. One of my goals is to be able to fold it small enough to park on the back lot of a marina in downtown Vancouver and fly directly from the harbor. My sketches include a nose-wheel stolen from an Aerocet float. Main wheels retract side-ways so that they also serve as dock bumpers.
Will I ever be able to afford to rent space at a Vancouver marina? Hah! Hah! Hah!
Either way, being able to fold to trailer width would reduce storage fees.
 

Riggerrob

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Go read the thread on "#550 Zenith Floats" and you will learn a lot.
Most of what is written about twin floats directly applies to flying boat design.
The next variable is how wide to build the cockpit ... which determines hull beam.
The third variable is whether to install wing-tip floats or sea-wings/sponsons.
 

blane.c

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Post #3
 

Riggerrob

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www.kenmoreairharbor.com contains illustrated parts lists for popular models of EDO aluminum floats. Kenmore bought the aviation assets of EDO Corporation during the 1980s and continues to over-haul EDO floats.
 
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blane.c

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If I remember correctly they are not 80% oversize, each is about 50% of total weight of aircraft. Also in the article it says near the last that they may need a tail float, the floats do look short aft of the step?
 

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blane.c

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Too small even for a Part 103 ultralight?
See post #7

 

Martin W

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Designing floats can be a "black art" ... drag and aerodynamics are a factor of course ... but things like how and when the floats get up on "the step" almost has to be done by experiment ... not CAD ..... I have been told that many float planes cannot lift off smooth glassy water ... need a bit of chop and waves. Good luck with everything.
 

blane.c

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Designing floats can be a "black art" ... drag and aerodynamics are a factor of course ... but things like how and when the floats get up on "the step" almost has to be done by experiment ... not CAD ..... I have been told that many float planes cannot lift off smooth glassy water ... need a bit of chop and waves. Good luck with everything.
Usually on glassy water you will back taxi the take-off area in a zig zag pattern to provide "a bit of chop and waves".
 

JRC

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Go read the thread on "#550 Zenith Floats" and you will learn a lot.
Most of what is written about twin floats directly applies to flying boat design.
The next variable is how wide to build the cockpit ... which determines hull beam.
The third variable is whether to install wing-tip floats or sea-wings/sponsons.
Agree Members of EAA.or Chapter 1660 Tampa KTPF airport on Davis islands...We are planning to use a mod'd Float design for the fuselage of our Baby Benoist project FMI text 813-784-4669
 

Riggerrob

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Hi. maybe this (if you can read Spanish)
Page 4 has 2 diagrams of 2 different ways to vent air into steps: tubes and curved steps.

Apparently vent tubes are available as an STC on Republic Sea Bees. Has anyone compared take-off performance with and without vents?

How effective are those vertical tubes? Grumman Mallard wheel wells drain directly into the step area allowing both water and air to descend rapidly overboard.

How important is venting the step?
 

JortzysCorner

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I appreciate all the responses & reference information, from everyone. I have found the Zenair website & the thread you guys have mentioned to be very helpful. These references should be enough to get me started down the right path. As for the next variables, Riggerrob, I know I'm going to want wing tip floats. As for hull/cockpit width, I was thinking just 28".....this is negotiable, but I am a smaller guy (5'10 - 160lbs wet), so I was thinking of going narrow to save weight to be used in other areas. Hence, the reason wing tip floats are likely.

Also, does anyone have a good idea of how much of the hull/fuselage weight would be considered essential operating equipment for a seaplane? On the EAA website, they don't provide a clear answer. I thought it used to specifically state "320lbs Max" for an ultralight seaplane regardless of what extra floatation equipment was added. Just need to be below that. Also, I don't know that 320lbs is accurate. I had just read that in the past, & can't seem to find that value anylonger. If someone has a good reference, I would appreciate it. Just want to have my design constraints verified before I truly start the design process.

Thanks Again!
 

rtfm

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Construction drawings of all aluminum floats are available from Murphy, Zenith, etc. You can learn a lot by studying their proportions.
<SNIP>
An excellent overview - which I shall be going through in detail. I have made a few preliminary drawings of floats for the Fleabike. So this is gold... Thank you.
 

blane.c

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I appreciate all the responses & reference information, from everyone. I have found the Zenair website & the thread you guys have mentioned to be very helpful. These references should be enough to get me started down the right path. As for the next variables, Riggerrob, I know I'm going to want wing tip floats. As for hull/cockpit width, I was thinking just 28".....this is negotiable, but I am a smaller guy (5'10 - 160lbs wet), so I was thinking of going narrow to save weight to be used in other areas. Hence, the reason wing tip floats are likely.

Also, does anyone have a good idea of how much of the hull/fuselage weight would be considered essential operating equipment for a seaplane? On the EAA website, they don't provide a clear answer. I thought it used to specifically state "320lbs Max" for an ultralight seaplane regardless of what extra floatation equipment was added. Just need to be below that. Also, I don't know that 320lbs is accurate. I had just read that in the past, & can't seem to find that value anylonger. If someone has a good reference, I would appreciate it. Just want to have my design constraints verified before I truly start the design process.

Thanks Again!
It is way down the document @ 18 powered vehicle weight.


(I like to point out the second sentence)

(2) Floats Used For Landings On Water. Only the weight of the floats and any integral, external attachment points are excluded. All other items associated with attachment of the floats to the airframe are included in the vehicle’s empty weight. Up to 30 pounds per float may be excluded by the FAA without requiring substantiation of the float’s actual weight. This exclusion was allowed under the rationale that float-equipped ultralights would not usually be operated in the vicinity of airports and large concentrations of people and, thus, would be even less of a safety hazard than those which had conventional landing gear. While amphibious capability would appear to negate somewhat that rationale, some allowance for the “float” capability is made.

(i) Amphibious Floats. up to 30 pounds per float may be excluded by the FAA. The weight of all attached items associated with the installation and operation of the landing gear is included in the calculation of the dry, empty weight specified in 5 103.1(e)(1). Satisfactory evidence of the weight of those components must be available.

(ii) Amphibious Fuselage. Where the fuselage is intended to function as a float during water landings, up to 30 pounds (tile average weight of a single float) is allowed by the FAA to be excluded from the empty weight where the ultralight is capable of repeated water takeoffs and landings. (Operators may be required to demonstrate the water operational capability of their vehicle
in order to receive an allowance for the added weight.) Up to 10 pounds per outrigger float and pylon is also allowed by the FAA.

(iii) “Float” provisions not discussed here should be reviewed with FAA personnel at a Flight Standards field office.
 
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