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The Unofficial Bearhawk FAQ

Technical Tips and Tricks

 

How to Notch Tubing by Budd Davisson

To determine the length and angle:
1. Lay the tube to be cut across the tubing to be bridged and make a magic marker line on the tube that's right over the two tubes centerlines.
2. Cut on the lines. That'll give the angles, but the tube will be a little too long.
3. Cut the notches to line up the notches:

1. Lay the tube on your bench top and slide it a few inches any direction so it leaves a scuff mark full length on the tube.
2. Take a magic marker and make a mark at each end of the scuff mark.
3. Using the sharp edge of a square edged grinding wheel cut a  "V" at the marks, then grind another "V" opposite that one. That sets the axis of the cut.
4. Using your eyeball and the magic marker, extend the length mark around the tube.
5. Grind the Vs down to the line on one end.
6. Slowly dress the radius into the tube to meet the tubing with minimal gap.
7. Now go to work on the other end but slightly modify your original line that indicated the length and angle to take into account the changed length that occured when you notched the other end.
8. Index the tube on the other end with the already radiused notch where it's supposed to be and look down on the uncut end where it crosses the other tube. You'll be able to eyeball the depth of the notch within 1/16" and mark it. If it's a cluster with three pieces intersecting, you'll be able to eyeball the cuts much more closely than you'd think possible.
9. when grinding the radius on the final end, move slowly and it'll eventually drop into position.

You'll be amazed how quickly you develop the ability to envision where metal has to come off to make it fit. If gas welding, the gaps aren't particularly critical, just try to keep them under .080 with .030-.040 being optimal. And don't worry about smoothing the edges any more than just knocking burrs off. You're going to melt that edge anyway.

This entire process should take from 7 to as long as 10 minutes per end. Plus it gives you the ability to fudge the length because you're working down from too long to just right. Using a mechanical cutter means you have to be dead nuts on the length or you're screwed.

Any kind of mechanical tooling is a total waste of time unless you're going to be doing a production type of set up and then the hot set up is an old power nibbler being guided by a fish mouthed piece of thicker tubing clamped to the tubing. That's what all production houses used until the CNC nibbler or laser came along.

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Riveting Tips and Tricks

 

1. When riveting flush rivets (AN426), run a line of masking tape either side of the line of holes (on the gun side) and you'll find that the gun doesn't wander around anywhere near as much.
2. When riveting AN470 rivets put a piece of masking tape over the machined head of the rivet. You will very rarely miss another one or get another smiley.
3. When driving 3/32nd rivets use about 35-40PSI. The longer the rivet attachment the slightly higher the pressure.
4. When driving 1/8th rivets use about 65-70PSI. Again, when you need to use a longer rivet attachment increase the pressure slightly.
5. Try as best you can to drive the rivet in one go rather than multiple goes. Hold the rivet gun and bucking bar as square to the rivet as possible and just let the bucking bar do the work. If your pressures are right you'll see the head forming before your eyes and it will feel right. There's no other way to describe it.

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Go Fast Tips (from Dwayne Parkinson) The more asterisks, the higher the priority

*****1) Streamline the landing gear shock struts

*****2) Build tear drop fairing inboard of the wheel pants that fair the inside axle stub/gear leg intersections and brakes
**3) Fair the intersection of the strut with the bottom of the wing
4) Internally mounted antennas
5) Flush mounted Nav/Strobe lights in wing tips
6) Flush screws instead of round on the doors windows and boot cowl
7) Flush latch on oil door
****8) Make sure area where air enters the engine compartment is as smooth as possible by tightening up baffling, etc.
9) Make sure area where air exits the engine is as smooth as possible
10)  Make sure the volume of cooling air going into the engine = the volume of air exiting the engine
*11)  Flush mounted gas caps
12)  Tail wheel pant 
***13)  Reflex flaps
14)  Reflex ailerons
15)  Flush mounted pop out tail lift handles similar to Cessna product
*16) Streamline flying wires
*****17) Wheel pants / Pressure recovery wheel pants like on an RV (I don't know what that means)
18) Flush camlocks on the engine cowl
19) Aerodynamic or rear facing step peg rather than a round peg sticking out from the landing gear (used to step into plane)
20) Replace wing root vents with vents that can be opened or closed when needed. 
21) Aerodynamic exhaust pipes angled back rather than sticking straight out the bottom of the plane
**22) Tight door and window seals
23) Gap seals where appropriate
24) Light prop optimized for cruise speed (or possibly ground adjustable)
25) Replace window catch on the bottom of the wing with lift gate type shocks used in SUV's and mini-vans.
26) Use small wheels
27) Wheel hub covers
28) Flush mounted door latches
*****29) BUILD LIGHT (no insulation, few avionics, spartan interior, minimal primer and paint, etc)
30) Find the best weight/HP ratio for the engine

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Hardware parts list (from AviPro QB list, modified with vendors I have used to acquire parts)

 
Item Vendor Qty Part Number Comment
         
Bearhawk Plans R & B Aircraft 1    
Brunton Flying Wires Private individual 1    
Wings Avi Pro 1    
Fuselage Avi Pro 1    
Main Tanks Avi Pro 1    
Aux Fuel Tanks Avi Pro 1    
Wing Struts w/fittings Avi Pro 1    
Wing Tips Avi Pro 1    
Firewall/boot cowl Avi Pro 1    
Cowling/nose bowl Avi Pro 1    
Flap return springs R & B Aircraft 1    
         
MISCELLANEOUS        
Freight from Avi Pro Avi Pro 1    
Wing crating Avi Pro 1    
         
LANDING GEAR        
Heim rod ends for landing gear Avi Pro 1    
Landing gear Avi Pro 1    
Shock struts Avi Pro 1    
Landing gear O-rings and snap rings R & B Aircraft 1    
Shock strut springs (set) Scott Special Tools 1 EH200-800 816-421-2444
Cleveland wheels and brakes kit   1 199-62  
Tires   2    
Axle nuts 1 1/2 x 16   2 MS21025-20  
Cotter pins 2" B & B Aircraft 4 MS24665-360  
Axle shims 1 7/8"   2    
AN5 Bolts, nuts, washers for brakes     MS21042 recommended Determined by brake type chosen
Jam nuts for rod ends        
Filler plug 1/8"NPT shock strut        
         
BRAKES        
Brake cylinders B & B Aircraft 4    
1/4" aluminum brake line   16    
AN fittings for 1/4" AL brake line        
flexible hi pressure hose        
fittings for hi pressure hose        
Adell clamps to secure hoses        
AN3 bolts/nuts for Adell clamps        
poly tube/fittings for supply side        
         
PULLEYS - ailerons        
Pulley - on wing tube support B & B Aircraft 2 MS24566-4B is 3.5   
front spar pulleys   2 MS 20220-2  
fuselage side by wing strut   2 MS24566-3B  
         
PULLEYS - flaps        
At wing root-top   4 AN210-3A  
Fuselage bottom B & B Aircraft 6 MS20220-1  
         
TURNBUCKLES        
flap system B & B Aircraft 2 AN 135-32S  
aileron bellcrank cables B & B Aircraft 2 AN 135-32S  
aileron bellcrank to bellcrank B & B Aircraft 1 AN 135-32S  
rudder cables B & B Aircraft 2 AN 135-32S  
elevator cables B & B Aircraft 2 AN 135-32S  
trim system (1/16" cable) B & B Aircraft 1 AN 130-16S  
         
ROD END Bearings        
AILERON Bellcrank BEARINGS B & B Aircraft 4 R4FF   
pushrod-sticks to bellcrank   2 GMM-3M-570  
aileron pushrods   4 Aurora XM-3  
flap pushrods   2 GMM-3M-570  
trim pushrods B & B Aircraft 4 MM-3  
aileron/flap rod ends for hinges B & B Aircraft 10 REP4H6  
CABLE - 1/8   140 7 x 7 or 7 x 19 Stainless by the foot
CABLE - 1/16   30 7x7 or 7x19 Stainless  by the foot
Cable Shackles    14 AN 115-21  
    2 AN 115-32  
Cable Thimbles   100 AN 100  
    6 AN-3   
Nicopress Sleeves   100 18-3-M  nickel?
    6 18-1-C   
Fairleads 3/4"   18 PN40701-00 small hole
         
BOLTS AND FASTENERS        
Stick and Flap Assemblies B & B Aircraft 6 AN3-6A  
  B & B Aircraft 3 AN3-7  
  B & B Aircraft 8 AN3-10  
  B & B Aircraft 1 AN4-16A  
  B & B Aircraft 2 AN4-23  
         
Rudder Pedals and Brakes B & B Aircraft 4 AN3-5A  
  B & B Aircraft 2 AN3-12A  
  B & B Aircraft 2 AN3-6  
  B & B Aircraft 4 AN3-7  
  B & B Aircraft 2 AN3-11  
         
Wing Attach/Landing Gear B & B Aircraft 16 AN4-24A Requires 3 washers
  B & B Aircraft 2 AN5-14A  
  B & B Aircraft 2 AN5-21A  
  B & B Aircraft 2 AN6-15A  
  B & B Aircraft 2 AN6-21A  
  B & B Aircraft 2 AN6-22A  
  B & B Aircraft 2 AN6-23A  
  B & B Aircraft 4 AN6-26A  
  B & B Aircraft 2 AN7-11A  
  B & B Aircraft 2 AN7-12A  
  B & B Aircraft 2 AN7-16A  
         
Inside Wing B & B Aircraft 12 AN3-5A  
  B & B Aircraft 6 AN3-7A  
  B & B Aircraft 6 AN3-10  
  B & B Aircraft 4 AN3-13A  
  B & B Aircraft 2 AN3-21A  
  B & B Aircraft 2 AN4-10A  
  B & B Aircraft 2 AN4-20A  
  B & B Aircraft 2 AN4-27A  
  B & B Aircraft 2 AN5-6A  
         
Aileron and Flap Attach, etc. B & B Aircraft 40 AN3-5A   
  B & B Aircraft 4 AN3-13A  
  B & B Aircraft 10 AN4-13A  
         
Tail Surfaces B & B Aircraft 4 AN3-5A  
  B & B Aircraft 2 AN3-6A  
  B & B Aircraft 4 AN3-7A  
  B & B Aircraft 4 AN3-11A  
  B & B Aircraft 2 AN3-14A  
  B & B Aircraft 2 AN4-6A  
  B & B Aircraft 10 AN4-10A  
  B & B Aircraft 2 AN4-14A  
  B & B Aircraft 2 AN4-15A  
  B & B Aircraft 2 AN4-17A  
  B & B Aircraft 2 AN4-24A  
Clevis pins B & B Aircraft 4 MS20392-2C49  
Motormount Attach B & B Aircraft 5 AN6-30A w/two washers  
Door Hinges B & B Aircraft 8 AN3-6A  
Clevis pins B & B Aircraft 4 MS20392-2C67  
         
Pulley Bolts B & B Aircraft 2 AN4-11A  
  B & B Aircraft 4 AN4-20A  
  B & B Aircraft 2 AN5-21A  
         
Nuts B & B Aircraft 150 AN3 NyLoc  
  B & B Aircraft 30 AN3 Castellated  
  B & B Aircraft 75 AN4 NyLoc  
  B & B Aircraft 12 AN4 Castellated  
  B & B Aircraft 20 AN5 NyLock  
  B & B Aircraft 17 AN6 Nyloc  
  B & B Aircraft 4 AN7 NyLoc  
         
Washers - two thick and one thin for each type bolt B & B Aircraft 500 AN3 - 230 thick and 115 thin  
  B & B Aircraft 200 AN4 - 106 thick and 45 thin  
  B & B Aircraft   AN5 - 16 thick and 8 thin  
  B & B Aircraft 200 AN6 - 34 thick and 17 thin  
  B & B Aircraft 12 AN7 - 8 thick and 4 thin  
Screws for floor boards - depends on material used        
         
Rivets B & B Aircraft 0.5 MS20426AD4-4 need 1/4 pound
  B & B Aircraft 0.5 MS20426AD4-5 need 1/4 pound
  B & B Aircraft 0.5 MS20426AD3-3 need 1/4 pound
    0.3 MS20426AD3-3.5 need 1/4 pound
  B & B Aircraft 0.5 MS20426AD3-4 need 1/4 pound
    0.3 MS20470AD3-3.5 need 1/4 pound
  B & B Aircraft 0.5 MS20470AD5-16 need 1/4 pound
    200 AD41ABS  
         
Nut Plates (wing/tank panels) B & B Aircraft 475 MK1000-06  
  B & B Aircraft 4 MS21051-06  
  B & B Aircraft 30 MS21073-06  
      1/4 x 1 7/8 x 5/16  
      PN 74354  
      PN 74347  


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Common Bearhawk Tire Sizes

Size   Diameter    Width
600------17"------------6.3"

700------18.25"--------7"

800------19.2"---------7.95"

8.50-----22.1"---------8.85"

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Most Common Drill Sizes (from small to large)
 

Drill Size Decimal
(inch)
Common Use
1/16 0.0625 Holes for safety wire
3/32 0.0938 Pilot holes before final drilling to #40
40 0.0980 Holes for 3/32" rivets
1/8 0.1250 Pilot holes before final drilling to #30
30 0.1285 Holes for 1/8" rivets
27 0.1440 Holes for #6 screws
5/32 0.1562 Pilot holes before final drilling to #21
21 0.1590 Holes for 5/32" rivets
19 0.1660 Holes for #8 screws
3/16 0.1875 Pilot holes before final drilling to #12, #11, or #10
12 0.1890 Holes for 3/16" rivets
11 0.1910 Holes for 3/16" bolts
10 0.1935 Holes for 3/16" bolts in UHMW plastic
1/4 0.2500 Holes for 1/4" bolts
 

Full Drill Size Reference
 

Number/
Letter
Fractional
(inch)
Decimal
(inch)
Metric
(mm)
80   0.0135  
79   0.0145  
  1/64 0.0156  
78   0.0160  
77   0.0180  
    0.0197 .5
76   0.0200  
75   0.0210  
74   0.0225  
73   0.0240  
72   0.0250  
71   0.0260  
70   0.0280  
69   0.0292  
    0.0295 .75
68   0.0310  
  1/32 0.0312  
67   0.0320  
66   0.0330  
65   0.0350  
64   0.0360  
63   0.0370  
62   0.0380  
61   0.0390  
    0.0394 1
60   0.0400  
59   0.0410  
58   0.0420  
57   0.0430  
56   0.0465  
  3/64 0.0469  
    0.0492 1.25
55   0.0520  
54   0.0550  
    0.0591 1.5
53   0.0595  
  1/16 0.0625  
52   0.0635  
51   0.0670  
    0.0689 1.75
50   0.0700  
49   0.0730  
48   0.0760  
  5/64 0.0781  
47   0.0785  
    0.0787 2
46   0.0810  
45   0.0820  
44   0.0860  
    0.0886 2.25
43   0.0890  
42   0.0935  
  3/32 0.0938  
41   0.0960  
40   0.0980  
    0.0984 2.5
39   0.0995  
38   0.1015  
37   0.1040  
36   0.1065  
    0.1083 2.75
  7/64 0.1094  
35   0.1100  
34   0.1110  
33   0.1130  
32   0.1160  
    0.1181 3
31   0.1200  
  1/8 0.1250  
    0.1280 3.25
30   0.1285  
29   0.1360  
    0.1378 3.5
28   0.1405  
  9/64 0.1406  
27   0.1440  
26   0.1470  
    0.1476 3.75
25   0.1495  
24   0.1520  
23   0.1540  
  5/32 0.1562  
22   0.1570  
    0.1575 4
21   0.1590  
20   0.1610  
19   0.1660  
    0.1673 4.25
18   0.1695  
  11/64 0.1719  
17   0.1730  
16   0.1770  
    0.1772 4.5
15   0.1800  
14   0.1820  
13   0.1850  
    0.1870 4.75
  3/16 0.1875  
12   0.1890  
11   0.1910  
10   0.1935  
9   0.1960  
    0.1969 5
8   0.1990  
7   0.2010  
  13/64 0.2031  
6   0.2040  
5   0.2055  
    0.2067 5.25
4   0.2090  
3   0.2130  
    0.2165 5.5
  7/32 0.2188  
2   0.2210  
    0.2264 5.75
1   0.2280  
A   0.2340  
  15/64 0.2344  
    0.2362 6
B   0.2380  
C   0.2420  
D   0.2460  
    0.2461 6.25
E 1/4 0.2500  
    0.2559 6.5
F   0.2570  
G   0.2610  
  17/64 0.2656  
    0.2657 6.75
H   0.2660  
I   0.2720  
    0.2756 7
J   0.2770  
K   0.2810  
  9/32 0.2812  
    0.2854 7.25
L   0.2900  
M   0.2950  
    0.2953 7.5
  19/64 0.2969  
N   0.3020  
    0.3051 7.75
  5/16 0.3125  
    0.3150 8
O   0.3160  
P   0.3230  
    0.3248 8.25
  21/64 0.3281  
Q   0.3320  
    0.3346 8.5
R   0.3390  
  11/32 0.3438  
    0.3445 8.75
S   0.3480  
    0.3543 9
T   0.3580  
  23/64 0.3594  
    0.3642 9.25
U   0.3680  
    0.3740 9.5
  3/8 0.3750  
     0.3770  
    0.3839 9.75
W   0.3860  
  25/64 0.3906  
    0.3937 10
X   0.3970  
Y   0.4040  
  13/32 0.4063  
Z   0.4130  
    0.4134 10.5
  27/64 0.4219  
    0.4331 11
  7/16 0.4375  
    0.4528 11.5
  29/64 0.4531  
  15/32 0.4688  
    0.4724 12
  31/64 0.4844  
    0.4921 12.5
  1/2 0.5000  
    0.5118 13
  33/64 0.5156  
  17/32 0.5312  
    0.5315 13.5
  35/64 0.5469  
    0.5512 14
  9/16 0.5625  
    0.5709 14.5
  37/64 0.5781  
    0.5906 15
  19/32 0.5938  
  39/64 0.6094  
    0.6102 15.5
  5/8 0.6250  
    0.6299 16
  41/64 0.6406  
    0.6496 16.5
  21/32 0.6562  
    0.6693 17
  43/64 0.6719  
  11/16 0.6875  
    0.6890 17.5
  45/64 0.7031  
    0.7087 18
  23/32 0.7188  
    0.7283 18.5
  47/64 0.7344  
    0.7480 19
  3/4 0.7500  
  49/64 0.7656  
    0.7677 19.5
  25/32 0.7813  
    0.7874 20
   51/64 0.7969  
    0.8071 20.5
  13/16 0.8125  
    0.8268 21
  53/64 0.8281  
  27/32 0.8438  
    0.8465 21.5
  55/64 0.8594  
    0.8661 22
  7/8 0.8750  
    0.8858 22.5
  57/64 0.8906  
    0.9055 23
  29/32 0.9062  
  59/64 0.9219  
    0.9252 23.5
  15/16 0.9375  
    0.9449 24
  61/64 0.9531  
    0.9646 24.5
  31/32 0.9688  
    0.9843 25
  63/64 0.9844  
  1 1.0000  

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Tap and Drill Reference

INCH SIZES - NATIONAL COARSE
TAP SIZE DRILL SIZE
#0-80 3/64"
#1-64 #53
#2-56 #51
#3-48 5/64"
#4-40 #43
#5-40 #39
#6-32 #36
#8-32 #29
#10-24 #25
#12-24 #17
1/4-20 #7
5/16-18 F
3/8-16 5/16
7/16-14 U
1/2-13 27/64
9/16-12 31/64
5/8-11 17/32
3/4-10 21/32
7/8-9 49/64
1"-8 7/8
1-1/8-7 63/64
1-1/4-7 1-7/64
1-1/2-6 1-11/32
1-3/4-5 1-35/64
2"-4-1/2 1-25/32
INCH SIZES - NATIONAL FINE
TAP SIZE DRILL SIZE
#1-72 #53
#2-64 #50
#3-56 #46
#4-48 #42
#5-44 #37
#6-40 #33
#8-36 #29
#10-32 #21
#12-28 #15
1/4-28 #3
5/16-24 I
3/8-24 Q
7/16-20 W
1/2-20 29/64
9/16-18 33/64
5/8-18 37/64
3/4-16 11/16
7/8-14 13/16
1"-12 15/16
1-1/8-12 1-3/64
1-1/4-12 1-11/64
1-1/2-12 1-27/64
1-3/4-12 1-43/64
2"-12 1-59/64
TAPER PIPE SIZES - NPT
TAP SIZE DRILL SIZE
1/8-27 R
1/4-18 7/16
3/8-18 37/64
1/2-14 23/32
3/4-14 59/64
1"-11-1/2 1-5/32
1-1/4-11-1/2 1-1/2
1-1/2-11-1/2 1-47/64
2"-11-1/2 2-7/32
2-1/2-8 2-5/8
3"-8 3-1/4
3-1/2-8 3-3/4
4"-8 4-1/4
STRAIGHT PIPE SIZES - NPS
TAP SIZE DRILL SIZE
1/8-27 S
1/4-18 29/64
3/8-18 19/32
1/2-14 47/64
3/4-14 15/16
1"-11-1/2 1-3/16
1-1/4-11-1/2 1-33/64
1-1/2-11-1/2 1-3/4
2"-11-1/2 2-7/32
2-1/2-8 2-21/32
3"-8 3-9/32
3-1/2-8 3-25/32
4"-8 4-9/32
METRIC COARSE SIZES
TAP SIZE DRILL SIZE
1mm x .25 .75mm
1.1 x .25 .85
1.2 x .25 .95
1.4 x .3 1.1
1.6 x .35 1.25
1.7 x .35 1.3
1.8 x .35 1.45
2 x .4 1.6
2.2 x .45 1.75
2.5 x .45 2.05
3 x .5 2.5
3.5 x .6 2.9
4 x .7 3.3
4.5 x .75 3.7
5 x .8 4.2
6 x 1 5
7 x 1 6
8 x 1.25 6.8
9 x 1.25 7.8
10 x 1.5 8.5
11 x 1.5 9.5
12 x 1.75 10.2
14 x 2 12
16 x 2 14
18 x 2.5 15.5
20 x 2.5 17.5
22 x 2.5 19.5
24 x 3 21
27 x 3 24
30 x 3.5 26.5
33 x 3.5 29.5
36 x 4 32
39 x 4 35
METRIC FINE SIZES
TAP SIZE DRILL SIZE
4 mm x .35 3.6mm
4 x .5 3.5
5 x .5 4.5
6 x .5 5.5
6 x .75 5.25
7 x .75 6.25
8 x .5 7
8 x .75 7.25
8 x 1 7.5
9 x 1 8
10 x .75 9.25
10 x 1 9
10 x 1.25 8.8
11 x 1 10
12 x .75 11.25
12 x 1 11
12 x 1.5 10.5
14 x 1 13
14 x 1.25 12.8
14 x 1.5 12.5
16 x 1 15
16 x 1.5 14.5
18 x 1 17
18 x 2 16
20 x 1 19
20 x 1.5 18.5
20 x 2 18
22 x 1 21
22 x 1.5 20.5
22 x 2 20
24 x 1.5 22.5
24 x 2 22
26 x 1.5 24.5
27 x 1.5 25.5
27 x 2 25
28 x 1.5 26.5
30 x 1.5 28.5
30 x 2 28
33 x 2 31
36 x 3 33
39 x 3 36

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Planet Bearhawk

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"You shall love the Lord our God with all your heart, with all your soul, with all your mind and with all your strength." and "You shall love your neighbor as yourself." ( Mark 12:30-31)

 

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