Help Needed - motor/wing size?

[gabecass]

I need someone to help me with a formula/equation to determine power thrust to body weight I.E. HP ,thrust,CC needed to get a pilot off the ground pilot weight 115.kg naked

so add the usual items to this Clothing first of course ,wing, reserve, fuel, gadgets GPS and Flying a wing within the weight range.

How much thrust, Horse Power needed per kg of Body Weight

if there is a simple equation out there I would appreciate it in printable format

Am I the heaviest pilot flying solo ? if you are around my weight or heavier would you drop me a PM describing the set up you fly .

Hope This Makes sense

Thanks in advance Gabe Cass

[pete_b]

I need someone to help me with a formula/equation to determine power thrust to body weight I.E. HP ,thrust,CC needed to get a pilot off the ground pilot weight 115.kg naked

so add the usual items to this Clothing first of course ,wing, reserve, fuel, gadgets GPS and Flying a wing within the weight range.

How much thrust, Horse Power needed per kg of Body Weight

if there is a simple equation out there I would appreciate it in printable format

Am I the heaviest pilot flying solo ? if you are around my weight or heavier would you drop me a PM describing the set up you fly .

Hope This Makes sense

Thanks in advance Gabe Cass

It would also depened on what wing you are flying, I think

Pete b

[Phil_P]

Basically, if you have a wing with a lift to drag ratio of 6:1, then you need 1/6th of the amount of the weight you are lifting in thrust.

eg, 6:1 L : D wing, AUW 120kg, so minimum thrust required to maintain level flight at best LD speed = 20kg. (120 / 6) Anything more than that will mean you can climb.

Phil

[Farmer_Dave]

Cant see how that would work Phil. My AUW is 150 and I fly an 8-5 to 1. So does that mean that less than 25 kg thrust would keep me airborn.? A Raket 120 puts out about 45 kg but I cant see one flying me somehow. Having said that I do fly at quarer throttle. Maybe I missed something. Just ignore me. Hello Gabe. 14 th August

[gordon_dunn]

Yes.. doesen't seem right... i'm 70kgs my H&E R120 produces 70kgs of thrust, and i fly straight and level at around 80% throttle..... 12kgs thrust would not be near enough.

[norman]

...thrust,CC needed to get a pilot off the ground pilot weight 115.kg naked

i am 6'6" and weight 120kg in my cotton socks. With my motor and wing plus I weigh around 170kg. A Parajet Macro with 180cc and around 70kgs of thrust popped me off the ground quite nicely.

I currently have a Fresh Breeze Monster (310cc) which generates around 75-80kgs. That is purpose designed for tandem flying - it blasts me off the deck very well. I wasn't even using full power for the takeoff and climb last time I flew and it did the job (running in).

'Mein Motor'

To answer your question more fully and reflect what others have said here, it is really important to consider your wing. With a bit of a draft I could get airborne on the Macro with a 30m Revolution, launching in nil wind was..... quite a challenge. After a couple of falls and a few busted props I realised I needed a bigger wing (at that level of skill) as ours is a game of the balmy surface winds of morning and evening - I bought a Dudek Synthesis 34.

Others with similar all up weights have had similar experiences, even those with plenty of PPG experience. One big chap here (a PG pilot of lots of experience) has resorted to a Synth 42 tandem wing for really easy launches in nil wind. This is generally thought to be a little extreme as launching in 12mph could present a challenge, but you can see his point.

On reflection it may well be that the ideal wing for us larger pilots is probably around 36m. The new Paramania Fusion at 32 - 36 may be just the ticket but others with more experience may like to comment on that.

It seems to me that optimum wing size also relates to experience. Pilots with well developed technique really appreciate the handling qualities provided by smaller wings. Launching them requires that skill but once airborne they have a lot to offer. Design quality is also playing its part here, the Fusion and the Nucleon have notable improvements in their launch and handling characteristics over previous designs. Pilots flying them refer to this and state that they can drop a wing size and reap rewards in handling because of it.

This is a personal view - my belief is that beginners need a wing that will launch easily above almost all else (given that it is a DHV-1 wing). If you cannot launch consistently and safely the mountain seems a tough one to climb and frankly people are prone to give up. This game needs a fair bucket of courage at the beginning and failed launches erode that as confidence dips in relation to the amount of dirt eaten and props busted.

After post solo consolidation you can hone your technique, gain a greater appreciation of what you are doing and build the confidence you need to really enjoy this sport. Without it the door merely can remain ajar on the rewards of flight.

Edited July 9, 2009 by Guest

[Phil_P]

To all you nay sayers

Remember that I did qualify my statements with 'to maintain level flight'. Obviously, the getting off the ground bit is 'climbing' so will require an excess of thrust.

An easy way to check out your TRUE L : D is to start off at a given height in still air (or fly an averaging course) say 2000 feet, then time your descent to 1000 feet. from the time and the distance you can work out a vertical velocity. Use a GPS ground speed, hence requiring still air (or if you believe it, the quoted air speed of your wing). the two figures in ratio is your L : D ratio (or glide ratio, it's the same thing). I bet it comes out at a lower value than you expect.

Another thing I think people should question, is whether their wing really DOES have a L : D ratio of in excess of 8:1 at their body weight. What the manufacturers are claiming is that for every kilo of drag (which is opposed by thrust) their wing will generate 8kg of lift. That is exactly what a L : D ratio IS.

At my maximum all up weight I weighed about 165 kg, I personally think that at that weight, my Swing Arcus at max trim probably had a L : D closer to 4:1, meaning I would need just over 40kg of thrust to maintain level flight, and remember, you nearly always will need more power at fast trim than slow. Given the relatively modest performance of the Solo, I don't think that is too wide of the mark.

Personally, I take pretty much ALL manufacturers performance figures with a very large pinch of salt. You might not like the results of all the above, but it is the truth.

Phil

[norman]

Phil,

I would really love to know what fuel consumption and TAS figures a 42m Synthesis produces. I think the results might be very revealing and compliment your post above. If I recall correctly Ian W reckoned his Synth 34 performed really well against other wings, even without letting the trimmers out or touching a speed bar. He was flying at a considerably lower AU weight than I am and that might scale to an interesting result.

[pauldeakin]

Manufacturers normally fly the wing with a standard paragliding harness when they work out L : D , the additional drag from a paramotor makes a big difference to the L:D, for example it could be 8:5 with a standard harness and less than 6:0 with a paramotor.

Paul D

[Farmer_Dave]

Bloody good point Paul

[Phil_P]

All the more reason to calculate your own true glide/ L : D ratio

[tommcb6016]

I would speak to your instructor about it and possibly try out some different motor/wing cobos before you buy, I think you will want at least 70kg's of thrust though.

Tom

[gabecass]

Ok Nitty gritty is a bailey 175 suitable for my weight ???? 115 kg that is naked weight

I have a 34 synth so I am within the weight range but still struggle with take off and climb rate 75 ft -100 ft per min

Gabe Cass

[Phil_P]

Well the Bailey gets me off the deck easily at 108kg on an APCO Thrust HP 09 in Medium which measures at 27.5 m2 flat, if that gives you any reference.

The Bailey I have found generates rather more thrust than it's HP figures would suggest. I can only put this down to the prop, which seems very efficient.

[Farmer_Dave]

Ok Phil. Found a little info which might help me to understand a bit anyway.

An 8.5 / 1 glide ratio capable wing is still approx the same with more weight hanging, ie a paramotor. It wont become 6 / 1 but it will go faster at 8.5 / 1. Faster forwards and naturally faster downwards.

The thrust figure you gave might have baffled me (quite easily done) because I was only thinking of static thrust, which, I understand is different from the mobilised figure. Is that right ?

Dave

[Farmer_Dave]

Gabe. That climb rate is not going to give you a good safety margin. What trimmer setting you getting that figure on? I'd expect to gain 75 ft in just over 10 seconds

[Phil_P]

You are quite right Dave, as the propeller reaches what is called it's 'pitch speed' the dynamic thrust actually tends towards zero. If the motor always had an excess of thrust above that required to overcome drag, then it would theoretically just become faster and faster, or in the case of our machines, the rate of climb woul just increase.

I am working on some figures to try and give an idea what we might expect as dynamic thrust at a given speed.

Phil

[Farmer_Dave]

Nice one Phil. I was reckoning the drag (from the cage by comparison with a freeflight harness) might be overcome by leaving the engine at idle, or just over. Mine seems to move a fair bit of air on tickover. If you stop the flow completely then the extra drag might steepen the decent angle slightly I guess. I'll try to measure it sometime though.

[norman]

If you leave the motor at idle you might have a little drag from the prop disk. Leave just a little thrust set and you provide a 'zero thrust' setting that counteracts the drag from the cage and motor assembly. That is the theory at least...

[alan]

My head hurts now so im off to bed lol let me know the outcome but in simple terms please over a bottle of rum.

[Farmer_Dave]

Dont you worry about the number crunching Alan. That Fusion's got a lovely glide. Just fly it and enjoy !

Dave

[alan]

Dont you worry about the number crunching Alan. That Fusion's got a lovely glide. Just fly it and enjoy !

Dave

Thanks Dave i did my first xc flight with it last time over Hornsea on the east coast of Yorkshire and although it was early afternoon and very thermic it seemed as stable as my Synthesis wing.

Tried for a early evening flight and disaster struck i got the bottom of my foot caught in my foot stirrup that i use to get in my seat and ended up hopping on one foot trying to cut the engine and falling on to my knee and breaking a propeller some thing you will not know about i hasten to add, they do look good those flat tops, Alan.

[Farmer_Dave]

I'm sorry to hear about your prop Alan. I imagine it must be a bit disappointing. When I was training I almost had such a moment when the leg straps weren't tight enough and started sliding down my thighs. I did get of but almost aborted.

Like to know what sizes your Fusion and Synthesis are, and any comparisons on speed and handling. They are the 2 I'm looking carefully at as I'd like a faster wing now. It might fit this thread but if not you can pm if you want.

Thanks

Dave

[bathboy]

I'm sorry to hear about your prop Alan. I imagine it must be a bit disappointing. When I was training I almost had such a moment when the leg straps weren't tight enough and started sliding down my thighs. I did get of but almost aborted.

Like to know what sizes your Fusion and Synthesis are, and any comparisons on speed and handling. They are the 2 I'm looking carefully at as I'd like a faster wing now. It might fit this thread but if not you can pm if you want.

Thanks

Dave

Gabe, Dave,

If it helps, I think the wing type, size and what you do with it is as important as the motor thrust.

From my limited experience with three different wings, all about 20 flights, all with the same-ish thrust, from a 6 year old Parajet (172cc) Compact motor with 3x99cm prop.

1) Nova Rotor 31 + trim out = average speed 15mph = rare use of full power = good economy (never tried with speed bar)

2) Action 27 + trim out = average speed 25 mph = frequent use of full power = poor economy

(+speed bar needs full power for level flight)

3) ReAction 31 + trim out = average speed 25 mph = medium use of full power = medium economy

(+speed bar 3/4 power for level flight)

That said the Nova felt 'nicest' to fly low and slow in no wind, the Action 27 felt safest to fly in crap wind, changes direction fastest, but the hardest to launch in no wind.

For me the ReAction 31 is 'almost' the best of all worlds... but if the wind was always 5mph or above, I'd go back to the Action 27 and carry more fuel!

IMHO the Action/ReAction is the safest wing section/design. Until another section has been around as long with so few (no?) incident.

None of these are scientific tests with a 'standard' weight. Beer capacity can adjust me from 90-95kg and fuel carried changes from 5ltr to 12ltr.

Cheers

Paul

[Farmer_Dave]

Thanks for those stats Paul. Which one were you flying at mine 2 yars ago ? Did you fly out across the moor that evening and how did it fare for speed against the rest of the gaggle ?

I have the Reaction on my list of maybes if it's cheap and s/h but I dont think it's as fast as the Synth or the Fusion. The Fusion would have economy I reckon. When I flew it on normal trim my engine was just chugging along like on my Atis 2. Great glide. Want to fly one again with instrument s next time. I do prefer a smaller wing so G R is an issue. Always open to suggestions though and want to fly them all on the same day. If someone could be there to lay them out and just pass me the risers I wouldn't even stop the engine. Then I'll write a review. LOL

See you soon too I reckon. Might have such a day !

Dave