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View Full Version : Legal Part 103 single-seat trike as flying boat (like Polaris or Sea Trike)?



mrscotty
02-16-2015, 02:24 PM
I am searching for an inexpensive low-n-slow Part 103 one-seater Trike with floats--no x-country, usage in favorable wind conditions only. Looking at the non-103 two-seater "flying boats" from Polaris and Sea Trike from the '80s and '90s gave me a crazy idea... why not use an inflatable boat with planing hull on a legal Part 103 trike? Here's an example configuration of what I mean:

Simple trike (e.g. without faring):

Ace Magic Laser

Wing:

??something with more load capacity to handle additional weight of boat hull??

Light, powerful motor:

Simonini Victor 1 Plus (6 HP more and 40 lbs less than Rotax 447 DC)

Inflatable Boat:

PHP-310 Performance Air Floor Inflatable from West Marine
(73 lbs + rigging and small rudder)

Certainly, the trike frame, wing and motor will need to be selected to handle the additional weight of the boat in order to have enough MTOW allowance, but it should be no problem meeting the legal weight limits of Part 103.

Of course, the manufacturers of the two-seaters claimed on their websites that their designs are safe and superior to regular straight floats. On the other hand, there are opinions in the Internet that these trike boats are too top heavy and unstable [e.g.: www.sydneymicrolightcentre.com/HTML/floats.htm] (http://www.sydneymicrolightcentre.com/HTML/floats.htm]). There's even a crash video on youtube [https://www.youtube.com/watch?v=P_TqMixB6wo], but that looks more like pilot error than general instability--the way he came down would have trashed just about any trike, regardless of the undercarriage and terrain.

Does anyone have first-hand experience with the safety of these flying boats? With the weight of the wing and motor up so high, how is the stability when the boat starts rocking? Is it possible to get the weight of the motor and pilot low enough for it to be safe without sacrificing visibility by having the pilot too low in the boat?

It is strange that these Polaris and Sea Trikes seem to have all but disappeared from the market after the brief popularity in the '80s and '90s. Did they die off because of safety issues? My suspicion is that they stopped being produced because the manufacturers didn't want to bother with the certification for S-LSA and the fiberglass/metal hulls being used back then were too heavy for legal Part 103 one-seaters.

Assuming that safety is not the issue, the new high-pressure inflatable floors being readily available may make this an interesting alternative. The PHP-310 from West Marine is only about $1400, which is considerably cheaper and also lighter than a set of floats. As a comparison, the RIB-310 Double Floor Rigid Inflatable from West Marine costs $3000 and weighs in at 130 lbs. The planing characteristics of the PHP-310 are still supposed to be pretty good--I read claims that it only takes 5 HP for 1 person.

So, is this a clever idea or is it something worthy of a Darwin award?

Mike M
02-16-2015, 08:04 PM
No, I have no experience with this topic.

Sounds like fun! Take one of the ultralights designed as a two-seat trainer, put it on a boat, splash away! Advisory Circular 103-7 from the FAA website says one may up the vehicle empty weight above the 254 number by 30 lbs because of the hull, no matter what it really weighs. And by 10 lbs per outrigger, or by 30 lbs per float, no matter what they really weigh. So if one called the inflatable boat a centerline float instead of a hull, then used some auxiliary floats instead of outriggers, 30 plus 30 plus 30 plus would allow a bunch of empty weight allowance and one still wouldn't exceed the design gross weight of the basic vehicle. Maybe even a few more aux floats if one needed?

or not. your mileage may vary. Still sounds like fun! Keep everybody informed of your progress, OK?

Greg Wilson
02-21-2015, 10:18 AM
In regards to the weight allowance for floats or hulls, that is true. However be aware that an ultralight, like any aircraft, is a compromise, change one thing and it will change something else. The part 103 item that is easiest to check and so most likely to be checked, is weight, but it must still meet all of the rule requirements regardless of exemptions to specific parts. If you add weight with floats or a parachute, the stall speed must still be not more than 24 kts CAS. The stalling speed if checked would make many "ultralights" unlicensed airplanes because weight gain has increased there stall speed. Weight, fuel capacity and number of seats is easy to check stall speed is not, so would it be a problem in the "real world", likely not, but it could be. The gross weight specified by many manufacturers is to control the stall speed, it is not due to structural issues. A heavy pilot can increase the stall speed to beyond what is allowed.

FlyingRon
02-21-2015, 10:27 AM
Martha King crashed in a Polaris once. Injured her wrist.

Michael Percy
02-28-2015, 08:13 PM
I have a lot of experience with float trikes, especially the Cygnet. Catamaran style floats provide much better stability than the monohull types that have fallen out of favor due to their tendency to capsize in a little cross wind. Two floats spread out gives the stability you need to counteract cross-wind. In a trike, the wing is very high. Even higher than a full-size high wing airplane like a Cessna 172 or 182. So you have a 100 pound wing mounted at the very top. The engine too needs to be high enough to give the prop clearance from the water. Finally, if you have a passenger in the typical trike they are seated a little bit higher than the pilot so they have a view. It all adds up to a high center of gravity. Flying solo on calm water in no wind, the FIB is not likely to capsize. But as soon as the wind gets above 5 or 10 miles per hour, or boat wakes unflatten the water, FIBs are prone to flip, even in experienced hands, in a split second of inattention. But the catamaran concept spreads the flotation wide enough to give enough stability for the pilot(s) to get out and both stand on the same float.

Check out the L-103 Explorer (www.flyamphib.com (http://www.flyamphib.com)) and the Cygnet at www.AirtimeAircraft.com (http://www.AirtimeAircraft.com).



I am searching for an inexpensive low-n-slow Part 103 one-seater Trike with floats--no x-country, usage in favorable wind conditions only. Looking at the non-103 two-seater "flying boats" from Polaris and Sea Trike from the '80s and '90s gave me a crazy idea... why not use an inflatable boat with planing hull on a legal Part 103 trike? Here's an example configuration of what I mean:

Simple trike (e.g. without faring):

Ace Magic Laser

Wing:

??something with more load capacity to handle additional weight of boat hull??

Light, powerful motor:

Simonini Victor 1 Plus (6 HP more and 40 lbs less than Rotax 447 DC)

Inflatable Boat:

PHP-310 Performance Air Floor Inflatable from West Marine
(73 lbs + rigging and small rudder)

Certainly, the trike frame, wing and motor will need to be selected to handle the additional weight of the boat in order to have enough MTOW allowance, but it should be no problem meeting the legal weight limits of Part 103.

Of course, the manufacturers of the two-seaters claimed on their websites that their designs are safe and superior to regular straight floats. On the other hand, there are opinions in the Internet that these trike boats are too top heavy and unstable [e.g.: www.sydneymicrolightcentre.com/HTML/floats.htm] (http://www.sydneymicrolightcentre.com/HTML/floats.htm]). There's even a crash video on youtube [https://www.youtube.com/watch?v=P_TqMixB6wo], but that looks more like pilot error than general instability--the way he came down would have trashed just about any trike, regardless of the undercarriage and terrain.

Does anyone have first-hand experience with the safety of these flying boats? With the weight of the wing and motor up so high, how is the stability when the boat starts rocking? Is it possible to get the weight of the motor and pilot low enough for it to be safe without sacrificing visibility by having the pilot too low in the boat?

It is strange that these Polaris and Sea Trikes seem to have all but disappeared from the market after the brief popularity in the '80s and '90s. Did they die off because of safety issues? My suspicion is that they stopped being produced because the manufacturers didn't want to bother with the certification for S-LSA and the fiberglass/metal hulls being used back then were too heavy for legal Part 103 one-seaters.

Assuming that safety is not the issue, the new high-pressure inflatable floors being readily available may make this an interesting alternative. The PHP-310 from West Marine is only about $1400, which is considerably cheaper and also lighter than a set of floats. As a comparison, the RIB-310 Double Floor Rigid Inflatable from West Marine costs $3000 and weighs in at 130 lbs. The planing characteristics of the PHP-310 are still supposed to be pretty good--I read claims that it only takes 5 HP for 1 person.

So, is this a clever idea or is it something worthy of a Darwin award?

mrscotty
04-26-2015, 06:32 AM
Thanks for the feedback. I think I'll drop this idea for now.