Building Options & Misc. 022410 page 10
2010 update. A new drawing and description for the PB-1 will show the 48”
Horizontal Stabilizer, and the matching elevator DIA TL-19B. Build the PB-1
with the 48” Horz Stab sections and 7/8 x 058 as shown. The discussion on
aileron and tail size is just a discussion for reference questions. Build
all models with the split angle aileron and 48” tail as the plans indicate.
DIA TL-19B
Aileron Option: On the Poorboy you can remove the aileron deflection (angle
difference between the root and end of the aileron). This angle difference was
put into the Poorboy design to soften the stall characteristics, it also
increases lift if rigged in the inline outboard pattern. A builder can remove
the angle difference if he is aware that the stall character may change. The
plans call for an abrupt angle difference at the strut position on the aileron,
the PB-1 has an extra rib at the strut location and the angle difference is set
right at that point and it is fairly easy to cut the tube where these two ribs
angle difference occurs allowing a person to eliminate the offset by putting a
splice over or inside the tube and riveting in the changed angle (the new angle
being “no angle difference in the aileron”). If a person didn’t like the results
he could go back to the split angle style by redoing the splice tubes position.
We recommend using the split aileron on all models as that is what we tested for,
the suggested rigging position is to have the outboard position in line with the
rest of the wing, this puts the inboard section down five degrees into the air
stream (like a slight flap position). A reminder that improper center of gravity
is critical to stall behavior as is anything else.
Size and wall thickness of airframe tubes change with the models, keep in mind
which model you are building and watch for the correct references for you model.
Center of Gravity calculations 022410 Pg-11
The Poorboy is designed and plans written for people who may or may not have
aviation experience. On the CG (center of gravity) topic we make it clear that
you need a proper and correct reference for calculating the CG. An incorrect
CG is a life threatening condition.
CG calculation on the Poorboy was done with half full fuel in the tanks, pilot
in the seat (flying configuration).
29% of wing cord balance point, about 17 ½” from Leading edge of wing.
I use the U.S. Department Of Transportation (Federal Aviation Administration) Pilot’s
Weight and Balance Handbook # EA-AC 91-23A. Formula for tail wheel type aircraft.
I used a plum bob line off the wing leading edge for a datum point, look at the correct formula for your
datum line application in the manual.
You cannot do an empty weight CG without the pilot because the pilot’s weight is too high a percentage
of the overall aircraft to exclude the pilot from the calculation.
Elevate the tail about a foot or so, so that the bottom of the wing is at the normal flying angle (angle of
attack is around 5or 6 degrees).
Don’t take my word for anything, there are several ways of figuring weight and balance.
I follow the instructions in the weight and balance handbook EA-AC 91-23A, there may be a newer
addition of this publication. See (FAA-H-8083-1)
Some handbook sources.
http://www.avshop.com/prodinfo.asp?number=163
http://www.amazon.com/gp/product/1560273771/104-0651358-687129?v=glance&n=283155
March 18, 2007 Aircraft weight and balance manual is available as a free download
at http://www.faa.gov/library/manuals/aircraft/media/FAA-H-8083-1A.pdf
Poorboy Construction 022510 Pg-12
Tube cutting is best done with a hacksaw, 24T blade. A tube cutter can be
used but it thins the wall at the end of the tube after de-burring and the
cutter can introduce small fractures or cracks that are hard to see so be
observant. A chop saw works well but the heat can effect some metals temper.
Tubes should be de-burred on the cut ends with a de-burring tool both on the
inside and outside of the cut surface. De-bur on the inside because anything
you insert into the tube could be scratched, on the outside to prevent scratches
on brackets etc., a round and flat files will do fine. A de-burring tool works
well. De-bur holes that are drilled into the tube with a larger drill bit, file,
or de-bur tool removing just enough material to make it smooth.
Hole location on tubes can be difficult to align when drilling a “through”
bolt hole, one way to get alignment is to use a piece of graph paper cut to make
a collar or “ring”. Align the paper on the tube and tape the circle seam, slide
the collar off the tube and flatten in half, use a marker to dot the creases.
When you slide the paper ring back on the tube the marked creases will be exactly
180 degrees opposite each other and inline by the edge of the paper or graph line.
Slide the paper collar back on the tube and mark the hole location and use a
center punch before drilling.
Center punch all drill positions before drilling. Tube and brackets can all be
drilled undersize (1/8 bit) and then have some chance at correction if a slight
problem exists, this makes the larger bit easier to drill also. On bracket or plate
brackets that are identical try to match drill using one to overlay the others and
use the 1/8” bit first. Pin the first drilled holes with a bolt, rivet, or drill
bit to keep everything in alignment.
Tubes are shaped with a tube bender when necessary. If you haven’t done this
in the past you may want to get some inexpensive conduit and try a few times to
get the hang of it. Place the bender and the piece your bending on top of a piece
of plywood so you don’t scratch up the work piece. You need the plywood and good
foot pressure to give good support to the work piece or it may buckle. A ¾” and
1” conduit bender are required for this project, these are conduit sizes and do
not match inch OD sizes. A ¾” bender is used on 7/8” and ¾” tube; a 1” bender is
used on 1 1/8” and 1” tube. Place your foot on the bender (foot location) and
keep good down pressure applied as you make the bend. You do not need to make
bends in steel to their final shape, you can make partial bends repeatedly and
slowly bring the piece to its final shape. You can reverse the bender and make
“minor” corrections in the opposite direction but if you get too far out of shape
it may be easier to discard the piece and start again, note that repeated movement
back and forth will weaken the piece. Aluminum hardens as you bend it and if you
wiggle it back and forth trying to get the right shape it will weaken significantly,
you can make progressive bends in the same direction but a reverse bend should be
very minor. When making progressive bends put the tool in its original position
with each increase in bend radius.
Other bending devises may work as well or better than the conduit type so if you
have access to better benders by all means experiment and use them.
Hardware: All hardware needs to be “AN” quality aircraft hardware. In order to
keep from marking up the bolts and wearing the nylock nuts you can use generic
hardware during building, you must not keep any lower grade hardware during
final assy.
022510 Pg-13
The plans list bolt sizes by diameter and type (like drilled or un-drilled),
however length will not always be correct. You can expect some error in
lengths so it will be a good idea for you to double check what the plans are
telling you on bolt lengths. You can figure it by learning “AN” numbering
system as described in most aircraft hardware parts books. A bolt gauge is
included in the diagrams (need to correct for print scale) may I suggest
that you buy a better bolt gauge. Note the difference between bolt length
and grip length. A locking nut should have at least one thread showing past
the end of the nut.
POP RIVETS: We recommend stainless steel rivets as the first choice. An
example is P/N SS42-SSBS, at .12 cents each (cheaper in qty), steel rivets
are quite a bit cheaper, monel are a better choice. No aluminum rivets are
used in this plane except as “temporary” fasteners except where noted. Rivets
are either stainless steel, regular steel, or a special monel rivet. The
stainless steel rivets can be substituted with a steel rivet but the steel
rivet tends to corrode over time so if you are in a high humidity area they
are less desirable (you can paint or varnish steel rivets to control corrosion).
The stainless steel rivets are a pain in the neck if you have to remove them
but they are strong and don't corrode. Removal....of a rivet is done with a
drill bit 1/64” smaller than the rivet size, drill and remove the head with a
chisel or wobble the stem of the drill bit in the top of the rivet to break it
off. If the rivet spins when you are drilling it you need to rotate the drill
angle and revolve around the hole position (wobble) to remove the rivet. If
the hole becomes two far enlarged you would need to go to the next size rivet
for a proper fit (exp..1/8 rivet to a 5/32 rivet). Rivets are 3/32, 1/8, 5/32,
3/16” diameter, there is a “grip” length associated with any rivet, look at the
“total thickness” of the items that are being riveted and be sure the rivet
minimum grip length meets or exceeds the requirement. A few solid rivets are
used on the controls they are to be flattened or “mushroomed” on the end.
Aluminum fabric rivets can be used on droop wing tips.
* Each construction step is associated with a file numbering system that
matches construction with pictures, diagrams, parts list, and hardware list.
You will notice a two letter indicator on each of these files or portion of
a file. (exp. AF (airframe), MG (main gear), WG (wing) etc.)
* Diagrams are done on graph paper, if you have difficulty in finding some
dimension look at a known dimension for that piece of the drawing and count
the lines (boxes). exp. 1 box = 1”, 1 box = ½”, 1 box = ¼” etc.
Help: The plans are intended to give sufficient information to build a
PoorBoy if you have some shop or mechanical experience. There may be
builders in your area or people with aircraft building knowledge, they are
usually quite willing and helpful if you ask. Check your area for Ultralight
or general aviation clubs, many fixed base operators have a repair shop and I
have gotten a lot of help from their A & P mechanics. The Poorboy builders
have a forum http://groups.yahoo.com/group/poorboy/
Substitutions: Most builders have idea’s they want to try out, sometimes
they have better ways of doing things but please remember to check with others
when making changes for safety.
The description sequence of building can be altered, you can build any section
first, hang-cage (fuselage), tail, wings etc. The tail is one place to start
that gives you some building time without a lot of investment. I like to do
the A-frame and hang cage.
Hinge construction using formed hinge sections. 022510 Pg-14
A regular flat piano hinge is standard however a rolled and shaped style hinge option you see
explained here is a novelty hinge style and is perhaps a bit stronger and I think is nifty however
it does slow down the building process.
The Poorboy rolled hinge installation style. Start off by making the hinge press, this is
done with a ¾” x 6” bolt, cut off the head, the non threaded area (grip length) is 4”. Make a press
cap from 1” outside diameter gas pipe (nipple etc.) and with a 4” no thread area cut it in half lengthwise,
file it smooth and remove imperfections. Put a strip of duct tape on one 4” edge of the press cap and
tape it to the bolt so it is easier to handle when you are pressing the hinge pieces. Position the piece
of hinge with the factory curled hinge portion facing away from the bolt, squeeze the hinge strip in the
hinge press using a vise. You now have a hinge half that is contoured to fit a ¾” to 1” etc. tube for the
tail feathers hinges, you may not want to use this on the ailerons as the bigger tube limits deflection angles.
Using two of these formed hinge halves rotate one half 180 degrees in position to the other half and
insert the hinge pin, this gives a slight “S” shape to the 3 ½” to 4” hinge segment you have just built.
Take a look at the pictures, I hope this will make it clear enough. Install the hinge with ½ hinge segment
up (Leading tube) and ½ of the hinge segment down (trailing tube) as shown. This hinge segment will give
you about 50 degrees rotation in either direction from straight in line position on a 1” tube installation
(+ 100 degree total rotation). Where a hinge strip requirement is greater than the 4" segments just put
more segments side by side and use a common hinge pin. Leave the hinge pin 1/2" longer than the hinge
segment on each end and bend the sticking out ends 45 degrees, using a drilled AN4 bolt (drill the hole
to 3/32") bend the hinge ends. This style of hinge pin installation is a bit unsightly but it is very easy to
view for safety inspections and allows easy pin removal in case you want to remove a control surface.
As stated earlier the hinges can be more easily done using a single half on each adjoining tube, facing the
hinge curl to the attached tube and forward tube hinge half up and the rear hinge half down. It is acceptable
with most configurations, just be sure you check total angle of hinge movement for your installation needs.
A-FRAME
021110
Pg-15
Use PB-1 information only, please ignore PB-U (Penny Piper), PB-H, and PB-2
references.
A-Frame Bow. Dia-AF-1 Pic-AF-1
Optional:: start by purchasing 10 ft of ¾ emt conduit, cut into two 4’ lengths,
use these two pieces as practice before you bend the 4130 steel bow.
The Bow is made of 7/8” x .058 x 4ft long 4130 steel tube. THIS IS THE HARDEST
(most pressure required) BEND ON THE AIRPLANE. Mark and center punch both sides
of a through hole position located at the center (24” from either end of the tube),
use a graph paper ring to get the holes in alignment. Drill a 1/8” hole on both
sides of the tube. Insert a ¾” x .049 x 3 ¼” long 4130-steel piece of tube into
the bow tube and center it to the 1/8” hole, slightly round the cut ends of the
insert before installing. Drill 1/8 hole into the insert at one of the 1/8” bow
holes, (be sure the insert is centered), (“or” drill 1/8 centered hole into the
insert before you install it into the 7/8” tube being sure you can align it to one
of the 1/8” bow tube holes).
Put a 2” sheet-rock screw into the hole to hold the insert in place, this screw
is the bottom reference for the bender (parallel inline with the benders handle)
and you want the screw to stick out straight as it goes through the bow tube and
insert. Drill the opposite “top” insert hole with the screw in place so the insert
does not loose alignment.
On top of the bow tube mark a line 1” on both sides from the top hole. On the
bottom of the center screw position mark a line on both sides of the Screw 1 ½” to
each side. Slide a bending support tube 8” onto one end of the tube you are bending
(the back side “tail” of the work stock to be bent and place on a piece of plywood
to prevent scratching when you make the bend. You will need this support tube for
leverage, any 4’ long pipe that gives a snug fit will work for the support tube
(a 1”x .058 x 4’ tube fits perfectly). Tape the support bar in place so it doesn’t
move around when you make the bend. You probably will not be able to make the bends
without the use of a support tube because the leverage will bring the work piece
off the ground unless you have the support tube extended length sticking out the
back side giving you the mechanical advantage for leverage, I even insert a big
screwdriver in the end of the support bar and tie a rope around the screwdriver
handle so I can pull at the same time that I make the bend for additional leverage
(tape for safety). You will need all of your weight on the foot position of the
bender, if you are a light person you may need help.
Position the tube on the bender with the support bar attached (RIGID ¾” EMT p/n
B-1678 Bender) so that the top 1” mark falls on the back side of the benders Hook,
and the bottom 1 ½” mark falls on the body at the start of the bend radius support
of the bender. The screw should be protruding straight out and parallel in line
with the handle of the bender and on the bottom side of the benders hook.
This is a fairly hard bend so keep good foot pressure on the bender, the bend is
about 70 DEGREES (go slightly less until you check everything). Bend the other side
of the bow by reversing everything (including the bend support bar) and this also is
about 70 DEGREES, “NOTICE” Pay particular attention to keep the bent arm in plane
with the handle on the second bend or your piece will not be in-line on the legs of
the bow. “Lets say that again!” Keep the two bent legs of the bow in line (in plane)
with each other, (use the benders handle for reference compared to the first bend).
A muffler shop or someone with a hydraulic bender and 7/8” jig can bend this
piece also in place of using a conduit bender as in the instructions.
021110 (See DIA AF-1 and DIA AF-2) Pg-16
The side legs are made of two aluminum (AL) tubes for each leg, a 1” tube
inserted into a 1 1/8” tube. These are .058 wall and are 48” long. From the
bottom of the side legs to the bottom of the seat support tube is 10 ½”.
The first hole for the frame strut bracket is at 9 ½” (three holes are from
the bottom of the leg at 9 ½”, 11”, 12 ½”). Use a graph paper circle to
locate these “through” holes” that are 1 ½” apart to match the double
U-bracket. The Rans W-WCL attach brackets are very nice piece of hardware
and cost about $5.00 a piece, you can make your own from 1.25 X 1.25 X 1/8”
6063-T52 U Channel stock from Aircraft Spruce & Specialty, P/N 03-39150 at
$3.75 a foot. Note.. the double U-bracket = (channel attach bracket) should
be exactly 1 ½” hole spacing but double check and match everything to the
channel attach double U-bracket holes (P/n W-WCL), use the double U-bracket
as a pattern to check hole locations. Make the flat strut frame brackets
that go under the double U-brackets and assemble on the side leg tubes
(See Pic-AF-2 & DIA-af-2). Install bolts and assemble the brackets to
the legs. **Note** The Diagrams for flat strut brackets and gear leg
brackets list the aluminum material as 6061-T6, a stronger bracket can
be made using 2024-T3 material and if cost is not a consideration this
.125” is the better material. The prototype PB-1 is flying with the
.125 6061.
Insert the steel bow tube legs (top of the “A” in the “A-Frame) into the
aluminum side legs of the A-frame, install and set the crossover tube in
position, set the bow to crossover seat tube height dimension for the
pilot at 42” (from bottom of the steel bow tube to the top of the cross
over tube). The outside distance at the bottom end of the side legs
should be 52” (outside), and at the seat cross support it should be
about 42” (inside distance of the A-Frame tubes at top of the seat
cross-over tube location).
Now is the time to decide how large your seat area needs to be for the
pilot.
The distance between the bottom of the bow tube arch and the top of the
cross-over tube (seat rail) is 42” in the plans and is adequate for most
pilots, you can increase this for a quite large pilot, this will not
bother the instructions as the root tube is set by angle not by distance.
You can lengthen the nose if need be also (see nose section) Make final
angle adjustments to the 4130 steel bow tube and line up everything.
You should have two side legs with four frame (strut) brackets underneath
four double “U” brackets. 3 ea. AN3 bolts (3/16”) hold the brackets
together on each leg (use temporary hardware). These too side leg
assembles slide onto the bow tube legs (do not drill yet, just tape
in position). Now the cross over “seat support” tube is also two tubes,
one inside the other like the legs (1” inside 1 1/8” .058 al. tube).
Cut the cross over tube to 42” and position in the bracket and drill
one hole only in each end matched to the flat plate bracket. The “A”
is complete, insert a bolt in each end of the cross over tube.
After cutting the 42” seat support tube (cross over carry tube), check position and alignment
of the A-frame assy.