rtfm
Well-Known Member
Hi guys,
I have been planning out the build process for the Razorback project, and based on current available income to spend on the project and available time (cash is the big constraint, however), unless I win LOTTO, the Razorback project is going to take me another six years to complete.
Six years!? I am very disappointed. After early progress (my fuselage is now almost ready to glass), things have slowed down dramatically. The money well has run dry. I am still going to try to have the fuselage glassed by Easter - but after that progress is going to be stop-start.
So I have made a hard decision: I can't spend another six years watching other guys flying - so I have decided that what I need is a very simple, small and cheap aircraft I can fly by this Christmas. Low and slow is fine. At least I'll be flying while I build. I looked around locally, and while there was actually an aircraft going for under $5k, I wouldn't want to fly in it. Besides, it was in pieces. Other more respectable microlights are going for about $12k and up. I have decided that I can build a very small and light plane for about $6.5k, including engine and instruments. This will actually add another year onto the Razorback build - but it is a trade-off.
Airframe:
What I have done is to return to an earlier design I produced before I decided to go for the current concept. It is based strongly on the little Russian gyro which I first saw pictured in the Rotary Wing Forum. This little aircraft sports a single-piece airframe made out of 2" foam, covered in glass. It took me all of 30 minutes last weekend to transform a couple of 1" sheets of foam into a fuselage, ready for glassing. Surface area of fuse = 11.5sq ft. It doesn't get easier that that.
From the pictures I have attached to this post, you can see the build concept quite clearly. My design naturally dispenses with the rotor, adds a proper tail section and mounts the wing on a triangulated support structure consisting of two braces and a rear anchor. This allows me to change the wing AoA if I need to (ie lower or raise the rear anchor point).
Landing gear:
Front attaches directly to the firewall. Rear will be glass or aluminum sprung, mounted to the keel (as in many gyros) with the addition of a lateral brace. Wheels: still looking. Brakes: still looking.
Engine:
A number of possibilities suggest themselves. I only need about 30 hp, so I may go for one of the industrial engines (Honda, Briggs & Stratton) as used on many UL planes (approx 25hp). Both of these engines are sold here in NZ at extremely good prices. Or I may go for one of the tiny 660cc engines out of one of the Japanese Kei cars (no redrive, 48hp @ 3500RPM, or redrive, 65hp @ 6500RPM). Tons of these available. Maybe I'll stumble across some other possibilities. There are lots of options. I just need to decide on an engine, tie down the weight, and adjust the strongback angles (especially the firewall angle) accordingly.
Control linkages: All cables
Seat: Integral with airframe (ie make it, and bond it to the strongback)
Fuel:
Behind the seat, faired in to effect a bit of a streamline effect.
Radiator:
Also behind the seat (on opposite side of airframe from gas tank). Air intake in belly scoop like P-51. Plenum chamber a mirror-image of fuel tank on LHS.
Fairing:
Minimal fairing - cover the engine and sweep back to enclose the legs. Windshield will be flat sheet, bent and fastened to fairing.
Instruments:
Flight: Stratomaster Flight II ($500)
Engine: Stratomaster Universal engine monitor ($350)
GPS: My iPaq handheld running OziExplorer software (allows scanning in of full size air maps, and moving map functionality)
Radio: One of the hand-held options. Probably 2nd hand.
Wing:
Carbon spar (a-la-Marske)
Solid foam core
Single layer 8.8oz Satin weave cloth (a-la-Strojnic: glass layup on smooth surface, remove when still plastic and vacuum directly onto foam core)
Split flaps (across entire 70% of inner wing), 30% chord.
Span: 22.2ft
Chord: 3.17ft
Area: 70sq ft
H-tail area: 15 sq ft
Aerodynamics:
Tail arm: 9.2ft
Cht: 0.5 (probably a bit low)
Vht: 0.04
Static Margin: 7%
Airfoil: NACA747A315 (low pitching moment + very low drag. Reasonable Clmax)
CG movement: 2" between full and empty tanks
Stall: 35kts
I am really hoping to get this completed by Christmas. Then I can fly while I continue on the large project.
Comments welcome
Regards,
Duncan
I have been planning out the build process for the Razorback project, and based on current available income to spend on the project and available time (cash is the big constraint, however), unless I win LOTTO, the Razorback project is going to take me another six years to complete.
Six years!? I am very disappointed. After early progress (my fuselage is now almost ready to glass), things have slowed down dramatically. The money well has run dry. I am still going to try to have the fuselage glassed by Easter - but after that progress is going to be stop-start.
So I have made a hard decision: I can't spend another six years watching other guys flying - so I have decided that what I need is a very simple, small and cheap aircraft I can fly by this Christmas. Low and slow is fine. At least I'll be flying while I build. I looked around locally, and while there was actually an aircraft going for under $5k, I wouldn't want to fly in it. Besides, it was in pieces. Other more respectable microlights are going for about $12k and up. I have decided that I can build a very small and light plane for about $6.5k, including engine and instruments. This will actually add another year onto the Razorback build - but it is a trade-off.
Airframe:
What I have done is to return to an earlier design I produced before I decided to go for the current concept. It is based strongly on the little Russian gyro which I first saw pictured in the Rotary Wing Forum. This little aircraft sports a single-piece airframe made out of 2" foam, covered in glass. It took me all of 30 minutes last weekend to transform a couple of 1" sheets of foam into a fuselage, ready for glassing. Surface area of fuse = 11.5sq ft. It doesn't get easier that that.
From the pictures I have attached to this post, you can see the build concept quite clearly. My design naturally dispenses with the rotor, adds a proper tail section and mounts the wing on a triangulated support structure consisting of two braces and a rear anchor. This allows me to change the wing AoA if I need to (ie lower or raise the rear anchor point).
Landing gear:
Front attaches directly to the firewall. Rear will be glass or aluminum sprung, mounted to the keel (as in many gyros) with the addition of a lateral brace. Wheels: still looking. Brakes: still looking.
Engine:
A number of possibilities suggest themselves. I only need about 30 hp, so I may go for one of the industrial engines (Honda, Briggs & Stratton) as used on many UL planes (approx 25hp). Both of these engines are sold here in NZ at extremely good prices. Or I may go for one of the tiny 660cc engines out of one of the Japanese Kei cars (no redrive, 48hp @ 3500RPM, or redrive, 65hp @ 6500RPM). Tons of these available. Maybe I'll stumble across some other possibilities. There are lots of options. I just need to decide on an engine, tie down the weight, and adjust the strongback angles (especially the firewall angle) accordingly.
Control linkages: All cables
Seat: Integral with airframe (ie make it, and bond it to the strongback)
Fuel:
Behind the seat, faired in to effect a bit of a streamline effect.
Radiator:
Also behind the seat (on opposite side of airframe from gas tank). Air intake in belly scoop like P-51. Plenum chamber a mirror-image of fuel tank on LHS.
Fairing:
Minimal fairing - cover the engine and sweep back to enclose the legs. Windshield will be flat sheet, bent and fastened to fairing.
Instruments:
Flight: Stratomaster Flight II ($500)
Engine: Stratomaster Universal engine monitor ($350)
GPS: My iPaq handheld running OziExplorer software (allows scanning in of full size air maps, and moving map functionality)
Radio: One of the hand-held options. Probably 2nd hand.
Wing:
Carbon spar (a-la-Marske)
Solid foam core
Single layer 8.8oz Satin weave cloth (a-la-Strojnic: glass layup on smooth surface, remove when still plastic and vacuum directly onto foam core)
Split flaps (across entire 70% of inner wing), 30% chord.
Span: 22.2ft
Chord: 3.17ft
Area: 70sq ft
H-tail area: 15 sq ft
Aerodynamics:
Tail arm: 9.2ft
Cht: 0.5 (probably a bit low)
Vht: 0.04
Static Margin: 7%
Airfoil: NACA747A315 (low pitching moment + very low drag. Reasonable Clmax)
CG movement: 2" between full and empty tanks
Stall: 35kts
I am really hoping to get this completed by Christmas. Then I can fly while I continue on the large project.
Comments welcome
Regards,
Duncan
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