Web: www.poorboyaviation.com E-Mail: hartungj@srt.com
PoorBoy Versions April 2011 Pg-5
Ultralight type planes have gone through continued development starting
somewhere in the 1970’s. A rediscovery of the basic fun and experimentation
produced a transitional progression of development that the law of the land
didn’t quite know how to keep up with, that led to a mess as the Federal
Aviation Administration (FAA) tried to regulate the airspace. People were
soaring down hillsides with hang gliders, small engines on the hang gliders
appeared and the FAA came up with the 155 lb foot launch rule. Next came the
hang glider with a seat and wheels, larger engines and a accompanied weight
increase of airframe and the part 103 254-lb rule came into effect to cover this
basic level of machine. The developmental progression didn’t stop or even slow
down but the FAA did, the FAA seemed unwilling to allow further development and
the part 254 lb rule held for about the next 20 years. Other countries (Canada,
England, France, Germany, etc.) progressed in the 1980’s and 90’s with Micro-
light categories in their laws allowing for the additional development of the
Ultralight movement, the US rules didn’t change until October of 2004 and
finally gave a boost to the life of aviation with the Sport Pilot Category.
The Sport Pilot License and associated Light Sport Aircraft (LSA) is the current
rule. The Ultralight rule was fortunately saved (thank God) and the FAA left
the 103 rule in place. This is my quick and probably narrow description of
what has taken place on the Ultralight scene in the last 30 years and is not
inclusive nor exactly accurate. I offer this bit of history to introduce
the different models of the PoorBoy.
Most single place fixed wing Ultralight aircraft in the past 20 years
(probably greater than 95%) were overweight but otherwise would meet the Part
103 rule. The obvious reason for this is airframe strength, most designers were
unwilling to cut the airframe formula that close to the safety margin of the 254
lb weight limit. There are 254 lb. Legal Ultralights that have had reasonable
safety history’s built in the past and still offered in the present but it is
difficult to keep them that way because of additions. Some designers break the
rule or give false information, try to find ways around it by not having niceties
like breaks or windshields etc., and others simply refuse to offer a claimed 254
lb. 103 legal model. It should be obvious that if you plan on building a 103 legal
“254 lb.” Ultralight that you cannot let its weight grow with additions or you miss
the point of the 103 legal effort in the first place.
I personally don’t like 254lb. Ultralights because I prefer the standard model
PB-1’s safer airframe. As I see part 103 a 254 lb. plane usually misses the
mark in weight or soon does after someone adds anything like windshield,
brakes, or instruments. Once you miss the weight goal then the exercise of
shooting for strict 254 is pointless and you may then have a more limited
strength airframe and the better choice is to build a PB-1. I support the
concept of the 103 limits in speed and flight envelope for an Ultralight. I
also support the rule's single place aircraft requirement for an Ultralight and
think that idea is paramount to an unlicensed sport vehicle of this kind.
April 2011 Pg-6
The PB-U is not a real plane, please ignore the PB-U references that you see
imbedded in the plans, (still too heavy).
The PB-1 is the standard model and will come out heavy by the 254 lb. rule,
the PB-1 can fly in the 103 envelope in every other part 103 requirement.
The PB-H (heavy load) are also imbedded in the plans and is about 20 lbs
heavier than the PB-1 because of heavier airframe members, this models options
are for pilots over 250 lb. pilot weight.
The PB-1 Poorboy: We have designed, built and flown the time off the PB-1
prototype. It costs a good bit of money and effort to bring a version of the
plane into existence, I explain this so that anyone interested in the Poorboy’s
will understand additional prototype models are limited in the real world of
time and money.
Performance: The range of performance is going to be similar to most of the
Ultralights you see on the market varying of course by the amount of power
applied. A few planes like Titan are meant to be clean and fast by design,
the Poorboy is not one of those. Poorboys have a low aspect wing and are
meant to perform in the Ultralight flight envelope, they will go faster but
fuel economy and engine life are matched to the best overall function without
excessive effort on streamlining. We keep the Poorboys in the Part 103
flight envelope by adding a split aileron that slows stall and limits upper
speed range.
Wing tip choice will effect stall speeds and so will aileron rigging. The
PB-1 prototype w/droop tips and a 200 lb. pilot stalls at 26 to 27mph. (28mph is
max stall speed for Ultralight).
Wing Tip Options.
There are four wing tip configurations you could use.
1. Cut tip. This is the wing just ending flat with no “tip”.
The Cut tip is a bit faster for speed due to less lift, it has a
higher stall speed also that raises the stall speed too high for
the 28mph limit in the part 103 rule.
2. Rounded tip. 16” to 18” rounded bow, adds 2.5 ft to wing span.
The rounded tip adds to lift by decreasing spill around the end of the
airfoil and increases the wing span, the rounded tip is a common type
of wing tip.
3. Droop tip. Nice looking, adds 1 ft to span.
The droop tip adds to the lift a good bit, decreases the stall as well
as increase lift, increases drag and may slow the upper end speed
some (looks cool and is my favorite).
4. Flat plate tip. Attached to “cut End” and is oversize to the
airfoil and adds to lift performance. The flat plate tip adds to lift
by damning the wing end and limiting air migration around the tip, it
adds lift similar to a droop tip because it is larger than airfoil
size, it is inexpensive and does not increase the wingspan. The flat
plate tip is easily removed and re-attach if you wanted to fly in the
cut tip configuration.
PoorBoy uses a USA 35B airfoil (but significantly modified in application),
attached baton style rib on 8” rib spacing (to limit scalloping on dope and
fabric wing), cable linkage on rudder and elevator, push/pull torque tubes
for aileron control.
The Prototype PB-1 uses a Rotax 503DC and the information about the PB-1 is
based on that configuration. Performance numbers on any plans built Ultralight
will change depending on how the ailerons are “rigged”, wing tip choices, and of
course the engine choice (35hp Min. to 52hp 503DC). 503DC Rotax is recommended,
however I am now flying a PB-1 with a 35hp Cuyuna UL202 and it flies very well.