Why being reclined is inefficient? Paramotor geometry part 19
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- čas přidán 17. 04. 2017
- Being reclined by 10 to 12 degrees is pretty safe, but in this episode, we will explain, that is inefficient and slow!
Flying perfectly straight is the most efficient and most safe way how to fly, but not the most comfortable. Today we will explain, how reclaiming your paramotor by 10 to 12 degrees will influence your paramotor and your efficiency.
In the final conclusion we found out some pretty interesting results!
Feel free to have any question at info@scoutparamotor.com
Topics that will be covered in this classroom:
*Please, be aware that we are adding videos each week, so there can and will be changes to this list.
1. Intro: Searching for the ultimate best paramotor - what is or will be your flying style?
2. Paramotor suspension, part 1: Why suspension is the most important characteristics of a paramotor?
3. Paramotor suspension, part 2: Why weight-shift is more fun and more safe?
4. Paramotor suspension, part 3: How much weight-shift authority you get from your paramotor?
5. Paramotor suspension, part 4: Pitch stability under power
6. Paramotor suspension, part 5: Speed bar behavior
7. Paramotor suspension, part 6: Ground-handling and running with a paramotor
8. Paramotor suspension, part 7: Comfort in flight
9. Paramotor suspension, part 8: The sectret questionmark suspension.
10. Paramotor suspension, part 8: The big comparison of paramotor suspension systems
11. Torque: Why and how much torque we face?
12. Torque: Why don't we use counter-rotating propellers?
13. Torque compensation on high suspension paramotors
14. Torque compensation on medium and low suspension paramotors
15. Torque: SCOUT Dynamic Torque Compensation.
16. Comparison of torque compensation systems
17. Gyroscopic effect on paramotors
18. Geometry of the paramotor frame, part 3: Why being reclined is dangerous?
19. Geometry of the paramotor frame, part 1: Why being reclined is inefficient?
20. Geometry of the paramotor frame, part 4: Big comparison of paramotor frame geometry
21. Harness geometry, part 1 - getting in and out of the harness
22. Harness geometry, part 2 -Why some harnesses are more comfortable than others?
23. paramotor safety, part 1: Load test of paramotors
24. paramotor safety, part 2: Attachment of the gooseneck bars to the main frame
25. paramotor safety, part 3: crumple zones and back protection
26. paramotor safety, part 4: Beware of getting the throttle cable into the propeller
27. paramotor safety, part 5: propeller clearance
28. How much power do you need?
29. Standard 125 cm prop or larger?
30. How much does weight matter?
31. Do you need a clutch?
32. Electric starter or manual?
33. How important is aerodynamics of paramotors? fuel tank hanging low
34. How much fuel capacity do you need?
35. What is the ideal paramotor for tandems?
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Music: / tracks - Sport
Nice thing about these videos is that it demonstrates you really have thought through the design for effective but simple solutions, elegant thinking :)
@Kyree Axl ... wtf has fuxzone got to do with my comment or indeed the video ?
Fucking spammers !!
@Stetson Charles .. wtf has fuxzone got to do with my comment or indeed the video ?
Fucking spammers !!
Videos are very good and educative.
Please make one video of durability on different brands? (main reason why I don´t have carbon scout)
Many times I fly on slippery ice and minor slips happens.
Also video on tandem flying with paramotor would be interesting?
Great video but I think I would still sacrifice the 6% for the added comfort. I would also sacrifice 6% to have slightly quicker takeoffs. This video has made me adjust my angle a little straighter though :)
This is a great video series, & I am learning quite a bit. Is it possible to have the pilot recline, yet keep the propeller vertical? I could see many advantages, but with the disadvantage of more complex, dynamic suspension geometry.
+Mark Rogers you have hit the nail! Wait for the next video...
As a free flight pilot I prefer to be very reclined when flying, since it gives me the most command over weight shift. I really enjoy the higher math, and advanced geometry presented in your recent videos.
I would like to see more, and so propose you make a channel for those of us who really enjoy the math. That way you can avoid scaring away the people who are less inclined to work out the figures. Either way, keep up the fantastic work! These are very helpful.
All paramotors have some minor fore/aft tilting once power is applied/released. This is why manufacturers recommend a tilt of 10-12 degrees. It is not for comfort, it is so when power is applied the line of thrust is in an optimal position.
czcams.com/video/Do5jqAdM6bI/video.html
SCOUT paramotor So the wing on a Scout paramotor stays perfectly in line with the center of gravity, it does not pitch back once thrust is applied?
Every well balanced paramotor stays in line with the glider, not just the SCOUT. Of course it depends on correct harness adjustment.
staying in line with glider I mean the paramotor tilts backwards on full throttle just as much the gliders steps back. Just like on a swing.
just experiment with tachometer and different angles of paramotor. At same altitude see what rpm necessary for level flight with each angle. Always a balance between form(being comfort) and function (being efficiency)
Would it be possible to build in the recline into the frame and harness ?
Btw, nice to see you include a little bit more of the maths, though it would be nice if you went through the units with a quick example to make things absolutely clear :D
anyhow, thanks again for another interesting video :)
freezatron
yes you are right! We have the recline angle built in the scout frame. Apart obvious advantage in flight, there are certain disadvantages as well. All these will be covered in the next video...
I'm guessing the disadvantages are to do with launch and landing body posture, greater pitch angle change during transition from feet down to up and thus a more pronounced gyroscopic precession effects on launch ? :)
+freezatron very good guess!
seemed the likely outcome of such an arrangement ;)
I can imagine the solution being something along the lines of having the seat portion of the harness on a "crossed trapezium" brace so that it could slide forward when seated and back when standing to reduce the transition angle. There is an elegant solution to this, I'm sure of it :D
Of course props with delta flapping hinges would also help here ;)
Something I proposed previously using a bolt on yoke with a through bolt to hinge the prop but was deemed a little too complex.
A simpler solution, using a thin sprung steel sheet as the delta hinge & damper connecting the hub and blades so it is effectively a single piece unit. Could be designed such that the blades bolt on to steel sheet delta hinge (which is sandwiched in the middle of the hub) for compact storage and ease of replacing the sprung hinge (for fatigue reasons) Plus this would work for props with more than two blades.
Not complex to install or use with a positive benefit.
Would be an easy upgrade to install. and minimal extra weight
"Just" needs designing, but then you guys are innovators :D
i wonder about the effects of a negative thrust angle when the thrust is facing 2 or 5 degrees downwards for example...is it possible that you increase the wing loading therefore gain speed?
+Yasha G yes. Sure
interesting...that could be a nice feature to alter the vector during flight. i can do it with my low suspension bars but i use my body to incline or decline the thrust by moving fwd and bckwd in my harness but some more comfortable mechanism would be nice..
+Yasha G it's possible with speed bar
There is a math error here. Your formula relating loading to speed is correct with its SQRT, but when you plug in numbers you wind up squaring instead of taking the square root. This happens initially at 2:40 (when you even say "square function") where sqrt(0.96) is 0.98, not 0.92, then again at 4:38 for your 1 degree calculation, and finally at 5:19 for each column in the table.
Note that this isn't just a typo where SQRT was used when SQR was intended. The formula is derived from the lift equation where the lift is proportional to the square of the velocity, and thus the velocity is proportional to the square root of the lift (or wing loading).
I noticed this error aswell
Which means that the speed loss is not nearly as much as claimed. I also wonder what it does to his efficiency calculation. The conclusion of this video, that reclined is more efficient, but not worth the loss of speed, should be reconsidered in light of the math error.
In my opinion the calculation is faulty because FIRST we need to find the reduced total thrust needed.
I am calculating the total thrust needed based on the inclination starting from :
H=W*s/v and H=T*cos(alpha)
T*cos(alpha)=(W-T*sin(alpha))*s'/v' and v' = ((W - T*sin(alpha))/W)^2*v and s' = ((W - T*sin(alpha))/W)^2*s
T*cos(alpha)=(W-T*sin(alpha))*((W - T*sin(alpha))/W)^2/((W - T*sin(alpha))/W)^2*s/v
Concluding to: T(n) = W*s/v / (cos(alpha) + sin(alpha)*s/v)
Based on the the given parameters: take-off weight W(t)=120 kg , sink rate s(0)=1,5 m/s, speed V(0)=10 m/s, thrust T(0)=18 kg (W*s/v=120*1,5/10), calculating with 10 degrees inclination the results are as follows:
1. total thrust needed: T(n)=s(W-(W*s/v)*sin(a))/v*cos(a) =17,81 kg
2. the unloading of the glider is V=T(n)*sin(a) = 3,09 kg
3. SQR = ((W-V)/W)^2= 0,95
3. new sink rate: 1,5*0,95 = 1,425 m/s
4. new rel. speed: 10*0,95 = 9,49 m/s
The difference in total thrust is 0,19 kg only, while the speed loss due to the lower horizontal thrust of 17,54 kg is 0,5 m/s (5%).
Their results are similar, but mathematically incorrect.
Please let me know if you think different.
This is why the big airplanes have elevator trims to adjust the pitch angle in horizontal flight for the most economical flight( or to lift more load , if necessary) . There must be a trim procedure for the paramotor "elevator" ( propeller vertical pitch )
Português
lot of nrs on efficiency... loss of 300gram per angle...and fuel usage getting lighter??.nothng about the risk of prop torque when tilted... the vids are great...stick to the flight scenes in Rockys.
risks of being reclined are described here: czcams.com/video/GnIjgz1e48s/video.html