Opinions sought: on 103 build (SS or AC)

Discussion area for builders of Pietenpol aircraft, both beginners and experienced folks. Share ideas, ask questions and help build the Pietenpol community.
Post Reply
User avatar
Piper
Posts: 20
Joined: Fri May 21, 2021 2:08 pm

Opinions sought: on 103 build (SS or AC)

Post by Piper »

Specifics are in the next (much longer) post (sort of an appendix) if anyone is interested.

(1) How difficult would it be for a person (125 # 5' 5" tall) to get into the cockpit of a Sky Scout without a flop or into the front cockpit of an Air Camper.

(2) Does the plywood sheet under the wing mounted fuel tank serve a structural purpose if there is no tank?

(3) Would moving the inner lift struts and compression struts together about three inches have any negative effect? (The idea being to narrow the fuselage by about that amount and keep the lift struts at a 90 degree angle.)

(4) Would anyone care to share their opinions on the "by the original plans" wooden Air Camper landing gear?

(5) Has anyone flown in an Air Camper with a "half-door" in the forward cockpit?

(6) Can anyone think of a problem arising from "scaling down" a fuselage, making it about three inches less wide and less deep, and a commensurate proportion (roughly ten percent) shorter behind the rear lift strut.

(7) If a train left Baltimore at 7 PM carrying (just kidding)

Thanks

Jacqueline
Last edited by Piper on Sun Jun 06, 2021 11:49 pm, edited 1 time in total.
User avatar
Piper
Posts: 20
Joined: Fri May 21, 2021 2:08 pm

Re: Opinions sought: on 103 build (SS or AC)

Post by Piper »

I'm in the process of building a "vehicle" compliant with all of the applicable regulations of FAR Part 103.

It will be a modification of either the Sky Scout or Air Camper. I have sets of both plans and the handbook purchased from "Mr. Andrew" as well as copies of a dozen 1930s and one 1960s article on their design and construction.

The literature and my own modeling from the official plans indicate that a SS without a powerplant could be built at about 200 pounds and a two-seat AC without a powerplant at about 260 pounds.

This "vehicle" will be powered by a (most likely inverted) Hirth 33 that I have on hand. With an inertial starter, ignition, exhaust, belt reduction gear, and a two blade Powerfin 'E' composite propeller on an Apex hub it weighs 53 pounds.

For either design the five gallon fuel tank will be placed directly in front of a minimalist Instrument panel that will host (L-R) a Bowden cable throttle, a "smile and ball" wing level indicator, and a CHT gauge. Airspeed will be will be shown by a "ball in tube" air pressure indicator mounted on the right forward wing strut.

I will be the only person operating this "vehicle" and am 125 pounds 5 foot 5. I can easily operate the "vehicle" in an 18 inch wide space. so my plan is to narrow the fuselage to that INSIDE dimension. I also thought I would decrease the fuselage's depth to maintain proportions. Improving the visibility over the front deck would be a side benefit.

Without a fuel tank in the wing, that structure can be altered. Made simpler and lighter. I can "hangar" a "vehicle" with a one piece wing on my property.

The pull for the inertia starter is on the left side.

OPTION ONE: SKY SCOUT

Pilot position would be moved forward about four or five inches.
The "flop" might be eliminated depending upon a mock-up test.
The wing would be built with a full center rib, without a wing fuel tank or its supports.
Inner compression struts would be relocated inboard about 1.5 inches each to allow the lift struts to remain at a 90 degree angle.
The motor mount would have to be extended forward a little, I need to do a mock-up to determine exactly how much based on alternative arrangements of accessories and additional weight of the larger mount.
I am considering decreasing the depth and width of the fuselage to 21 inches from 24.

OPTION TWO: AIR CAMPER

260+53 is 59 more than 254, but there are a number of structures I would remove.
Per my reading of the regs: I have to eliminate a cockpit, meaning the rear one.
Eliminating the flop, eliminating the radiator cut out, and the fuel tank and its supports.
I would decrease the width and depth of the fuselage as well as shortening it to SS length basically making it a Sky Scout with the cockpit located between the lift struts. (Not that that is a bad thing.)

Any opinions or ideas are welcome.

Thanks

Jacqueline

My opinion as to the "relevant" portions of Part 103. I have computed Max Speed (per Appendix A) and Stall Speed (per Appendix B) of the circular and have an eight to twenty percent "cushion."

Appendix

AC 103-7, 1/30/84,
12. ELEMENTS MAKING UP THE DEFINITION OF AN ULTRALIGHT VEHICLE.
a. Single Occupancy. An ultralight cannot be operated under Part 103 if there is more than one occupant or if it has provisions for more than one
occupant.
b. Sport or Recreational Purposes Only. An ultralight cannot be operated under Part 103 if it is operated for purposes other than sport or recreation or
if it is equipped for other uses.
c. No Airworthiness Certificate. An ultralight cannot be operated under Part 103 if it has been issued a current U.S. or foreign airworthiness certificate.
e. Powered Vehicles. A powered ultralight cannot be operated under Part 103 when it has an empty weight of 254 pounds or more, has a fuel capacity exceeding 5 U.S. gallons, is capable of more than 55 knots airspeed at full power in level flight, and has a power-off stall speed which exceeds 24 knots.
18. POWERED AIRCRAFT WEIGHT
b Acceptable Methods for Determining the Weight of an Ultralight. The completed assembled ultralight should be taken to a draftless location and
placed on:
(2) Two or More Scales. A determination may be made on two or more calibrated scales if they are located at all pints where the ultralight contacts
the surface when parked and it is resting fully on those scales without any stabilizing assistance, In this case, the sum of the scales will be used.
19. MAXIMUM FUEL CAPACITY OF A POWERED ULTRA LIGHT VEHICLE.
a. Determination of Fuel Capacity. The total volume, including all available space for usable and unusable fuel in the fuel tank or tanks on the vehicle is the total fuel capacity. The fuel in the lines, pump, strainer, and carburetor is not considered in a calculation of total volume.
24. CONTACTS WITH FAA INSPECTORS...
You should inform the inspector that you are operating your ultralight under Part 103 and provide evidence that it meets the applicability of 5 103.1.b
b. "Satisfactory Evidence."
(1) The use of the graphs provided in Appendixes 1 and 2 will be 6 acceptable for determlnatlon of the maximum level flight speed and power-off stall speed if your ultralight has no special limitations to maximum speed or power and no special high-lift-devices.
Last edited by Piper on Tue Jun 08, 2021 1:54 pm, edited 1 time in total.
User avatar
Terry Hand
Posts: 78
Joined: Thu May 18, 2017 2:37 pm

Re: Opinions sought: on 103 build (SS or AC)

Post by Terry Hand »

If you are making all of those changes, you are not really building a Pietenpol Air Camper. You are building your own aircraft version, based on the Air Camper/Sky Scout designs. No judgment here. Just an observation.

If that is the case, why don't you save yourself a lot of work, and just do this -

https://en.wikipedia.org/wiki/RagWing_RW1_Ultra-Piet

http://rogermann.org/ragwing/

Just my $.02 from a guy that has spent about 8 months away from his project. We aren't getting any younger (I don't even like to buy green bananas anymore), so every day spent designing is a day NOT spent building. I am getting back to mine this week.
Semper Fi,

Terry Hand
Athens GA
tom kreiner
Posts: 70
Joined: Sat Feb 25, 2017 9:49 am

Re: Opinions sought: on 103 build (SS or AC)

Post by tom kreiner »

You read my mind, Terry!

Actually, the proposition of redesigning the entire aircraft is daunting, even to an enginerd like me! Even the issue of determining W&B from Jacqueline's post is concerning, as she's mentioned not only downsizing the fuselage, but reducing it's length, then adding a rather small engine. Nothing could be simpler, RIGHT!!!!

The best advice you gave was to steer her towards the Ragwing Ultra-Piet, and perhaps she'll learn more from the old Matronics site, which has devolved a defacto Ragwing Ultra-Piet forum.

Best of luck with this project.
User avatar
Piper
Posts: 20
Joined: Fri May 21, 2021 2:08 pm

Re: Opinions sought: on 103 build (SS or AC)

Post by Piper »

Hi

I want to thank you for responding.

I assure you this will not be my first build, I am an experienced A&P mechanic and a certified commercial pilot, but I wish to build something that I cannot be arbitrarily prohibited from flying at my leisure from my own property.

I have purchased the RW-1 plan set from Mr Mann, and have considered it. I have also participated in the construction of a Kimbrel Banty and a modification of Mann's RW-5 Heath Replica (so I have studied the RW-4, 5, 6, and 7 plans). If the Part 103 weight limit was just a smidge higher, say 280 pounds, or if the stall speed worksheet allowed for the use of actual weights instead of standard weights I could simply build either an AC or a SS pretty much to plans.

Working the numbers, I know that this is all possible, and would love to hear from anyone who has done any of these things.

(1) Getting into and out of the "vehicle" without a flop or half-door.

(2) Using the "Cub" or AC wooden landing gear.

(3) Using an "automobile leaf spring" tail skid, a fiberglass tail skid, or the "V" SS tail skid. (Grass field)

Holding certification necessary to my employment, I wish to avoid potential conflicts over (mis)interpretations of rules that are often often contradictory with one another, I am choosing to use the most restrictive interpretation of each espoused rule.

My desire is to build what I consider a "real" Pietenpol, using the "official plans" I purchased from Andy. But like most everybody I will add my own personality to the build.

I have performed three complete analysis of the aerodynamic loads, weights, and balances of the RW-1, SS, and AC. I'm not knocking the RW-1, but my primary issue with the design is that it seems to be designed for ease of production-- odd for something being individually produced. The Pietenpol has to my mind a much superior stress analysis. The RW-1 appears to be safe, but the Piet should be able to take grater loads because the structure is designed to carry the actual local loads.

Again regulations require a minimum level of safety while simultaneously prohibiting improvements over that minimum level.

Look at the wing and empennage plans, without mathematics you can see that the Piets have dimensions based on aerodynamic load. The RWs are designed for symmetry and interchangibility. Their structure is uniform-- but the loads are not. It's like a chain being lowered from a tower. Ideally the upper links should be stronger than the lower links (because they must support the lower links as well as what is at the end of the chain.)

On the RW some parts are overbuilt (which due to regulations is a weight concern). Since failure will occur at the weakest point-- and I don't work for an airport authority that installs a twenty foot wide, ten foot tall gate with razor wire, electronic locks, and a remote video surveliance system, in the middle of an unlighted mile of 36 inch high spit rail fencing around the airport and declare the place secure-- at the very least repositioning the RW's parts will increase the strength of the structure.

Even my 1930 AC plan differs a bit from my 1933 AC plan (I rather like the aesthetics of the squared-off horizontal stabilizer). BHP himself revised the front end for the lighter Continental and Corvair powerplants. There were approximately 900 variations on landing gear design (I rather like the "stock" three point SS design-- I hope Pilatus is sending Andy royalties :D ). Moving the fuel tank and adding a half door are in the plans. There is an "official" plan to extend the fuselage and to to move the pilots seat back to accomidate a taller pilot, people have extended the lift struts and increased their rake.

I submit that these are all "real" Pietenpols.

When you look at the center of lift and the center of gravity the SS is just a slightly scaled down AC that only seats a single occupant-- important because notwithstanding the fact that anything mechanical can be modified-- to be compliant a ULV cannot be "modified" to hold a second occupant. (Heck years ago I "rebuilt" a certified Aeronca AC-2 from an "airworthy" dataplate and a pile of rusty metal.) The SS has about a six inch shorter fuselage with one less frame than the AC. The front has been effectively extended five inches by raking back the lift struts. Each tail surface is about five inches shorter.

The AC was balanced for fight. With fuel and a passenger if there was one carried on the CG. With lighter air cooled engines BHP extended the nose of both the AC and SS forward. I weigh 125 pounds and am 5' 5" tall. I must move the seat forward or move the controls back. Moving me forward about five or six inches places me in an ideal position with the flight controls "per plan," and it moves the CG forward.

I'll revise my language in the earlier post but I intended to either build the "vehicle" in it's entirety to a scale (IE 95%) or to build a single occupant aircraft of the AC layout to (full or scaled) SS size. I never intended to "willy-nilly" resize things and invalidate the engineering already performed. (I am greatly concerned that building a scaled down (IE 90%) AC would be a regulatory 'Trojan Horse' because I could obviously simply add a front cockpit after certifying it's weights.)

So on to particulars: (I have completed my modeling since my initial post.)

(1) Pilot position will be moved forward about five to six inches in the SS (official plans show how to do the opposite).

(2) The "flop" will be eliminated regardless of which "vehicle" is built (a minor modification).

(3) The wing will be built without a cutout, with a full center rib, and without the fuel tank or its supports (per official plans).

(4) Inner compression struts will be relocated inboard about 1.5 inches each to allow the lift struts to remain at a 90 degree angle.

(5) The width and maximum height of the aircraft fuselage will be decreased from 24 to 21 inches.

(6) The motor mount will be extended forward a little, I need to do a mock-up to determine exactly how much based on alternative arrangements of the muffler and other items as well as the increased weight from the longer mount (there are multiple official engine mounts, one will be adaptable).

(7) On an AC pattern "vehicle" the SS wing would be used (making it a "Sky Camper?)

(8) On an AC pattern "vehicle" the fuselage will be of SS length and have the SS lift strut rake. (Air Scout?)

Any opinions or ideas are welcome.

Jacqueline
Last edited by Piper on Tue Jun 08, 2021 9:22 pm, edited 1 time in total.
User avatar
Terry Hand
Posts: 78
Joined: Thu May 18, 2017 2:37 pm

Re: Opinions sought: on 103 build (SS or AC)

Post by Terry Hand »

You seem like you have your mind made up. So all I can say is, “Good luck”.
Semper Fi,

Terry Hand
Athens GA
Earl Brown
Posts: 54
Joined: Mon Nov 04, 2019 12:24 pm

Re: Opinions sought: on 103 build (SS or AC)

Post by Earl Brown »

As Terry said, it sounds like you are looking for validation on something you’ve already made your mind up about.
There are plenty of aircraft that already fit what you are trying to do, but, it’s experimental aviation. So while it won’t be an Air Camper or a Sky Scout, go ahead and build “your” aircraft.
User avatar
Piper
Posts: 20
Joined: Fri May 21, 2021 2:08 pm

Re: Opinions sought: on 103 build (SS or AC)

Post by Piper »

Hi

I'm not looking for validation, just other people's experiences. It's easy to do the math and simple but time consuming to chop up cardboard boxes and make mock-ups. But what naggs me is the element over time...

EG: Moving the seat fixes CG, and eliminating the flop saves weight. But will getting in and out be a total PITA especially as I get older? I can't spreadsheet that.

Thanks
Last edited by Piper on Fri Jun 11, 2021 6:53 pm, edited 1 time in total.
User avatar
Clay Hammond
Posts: 36
Joined: Thu Feb 23, 2017 11:46 am

Re: Opinions sought: on 103 build (SS or AC)

Post by Clay Hammond »

Yes. It will absolutely be more of a pain in the ass. The flop was incorporated to make it less of a pain in the ass, no doubt after it had showed itself to be a pain in the ass to BHP.

The airplane is very much already a distillation of good airplane design within a certain style...i.e. golden age light aircraft (flivvers), and its evergreen appeal is due to that. One's desire to modernize, improve or modify is valid, don't get me wrong. Everyone has their unique set of needs and wants. Just be ready to give up things in that pursuit of your own perfection. Universal perfection is rare...but for what it is the AirCamper has come very close.
____________________

Visit Old Rhinebeck Aerodrome
www.oldrhinebeck.org
User avatar
Piper
Posts: 20
Joined: Fri May 21, 2021 2:08 pm

Re: Opinions sought: on 103 build (SS or AC)

Post by Piper »

Everything is life is a trade-off, a balancing act. But I chose to construct an AC or SS because if you are building for the sheer fun of flying, I haven't seen anything that is supported today that offers nearly as much.
Post Reply