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Oct 09, 2009, 02:24 PM
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F5D pylon racer


Hello everybody,

We are students looking for an extremely strong RC plane to purchase for scientific use. The plane will be flown on a cable, much like a kite on the sea-side. (The eventual goal is wind energy recuperation)

An F5D plane is a very good candidate, we think.
We have the following specs:

* good handling and stability
* wingspan about 0.8 to 1.1 m, wing area about 0.1 m^2
* speed range 30 km/h - 300 km/h
* capable of withstanding 20 kg of distributed load on the wings, when supported by the fuselage alone.

Is it possible to find a plane as strong as this; and can we buy it in Europe?

best regards,
Kurt & Joris
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Oct 09, 2009, 02:42 PM
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pabork's Avatar
1m wingspan planes has about 10sq dm wing surface
so it means You would have 2000g/dm when 100g/dm is really heavy/fast ship
Oct 09, 2009, 04:19 PM
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We don't know what the normal load for such planes are..
Maybe somebody can give some links to planes that can handle te biggest loads possible?
Oct 09, 2009, 04:34 PM
Registered User
And F5D plane weighs 1kg ready to fly. During turns around the course, the G-force in sharp turns exceeds 20g. So the airframe will easily withstand a distributed load of 20kg on the wings.

But a wing that small is not suitable for lifting 20kg off the ground no matter how strong the wind.

Presumably your intention is to be able to exert a pull of up to 20kg on the tethering cord and use that for power generation. That should work OK, but only if the wind is strong enough.

An F5D model is optimized to fly at speeds up to 200mph, at lower speed it generates much less lift. To maintain a 20Kg pull you would need a very strong wind which you are unlikely to find close to the ground. The application would work better with a wing designed to produce more lift. This would be thicker and thus easier to make strong. F5D models have high ratio, extremely thin wings for low drag and don't need to produce much lift to keep them in the air.

If you are looking for an off the shelf model, an F5B model is more likely to suit (if I understood the application properly). It too can easily withstand 20kg and with the larger wing area will fly properly and provide some pull, at much lower wind speeds.
Oct 12, 2009, 11:51 AM
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Thread OP
Our intention is indeed to let the plane pull as hard as possible on the tethering cord to use that for power generation. We currently estimate that the plane will fly at speeds of about 200mph.
Because of this high speed, an F5B maybe isn't such a good idea, or is it?

Perhaps you can give some of the typical airfoils used for F5D planes, or maybe some manufacturers of F5D planes?

Thanks a lot!
Oct 12, 2009, 12:59 PM
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Darron's Avatar
Quote:
Originally Posted by planepowerKUL
Our intention is indeed to let the plane pull as hard as possible on the tethering cord to use that for power generation. We currently estimate that the plane will fly at speeds of about 200mph.
Because of this high speed, an F5B maybe isn't such a good idea, or is it?

Perhaps you can give some of the typical airfoils used for F5D planes, or maybe some manufacturers of F5D planes?

Thanks a lot!
I've seen these projects but they normally use canopy style kites with a much larger surface area than an F5D model.

How would you get the model to 200mph? or to an altitude where the wind speed is that high?
What will the weight of the tether be at that length?
How much energy do you expect to get out of the system?
- hint - we use 1000 Watts to get these models flying at 200mph.

For models and manufacturers see www.f5d.co.uk or www.f5d.de

Interesting project.

Darron
Oct 12, 2009, 01:46 PM
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You would certainly be much better off with a kite. Easier to control, works well in low windspeeds, doesn't break when crashed and can be sized for the amount of pull you want.
Oct 12, 2009, 02:38 PM
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rcelectfly's Avatar
Quote:
Originally Posted by planepowerKUL
Because of this high speed, an F5B maybe isn't such a good idea, or is it?
High quality F5B planes like Avioniks and Surprises have the same speed capability of a high quality F5D plane.

Chuck
Oct 12, 2009, 02:48 PM
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flying evader's Avatar
If you are not thinking of powering the plane you may get away with a dynamic soaring plane...
Oct 14, 2009, 03:50 AM
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Currently we're thinking of getting the Arianne P5 ( http://www.soaringusa.com/products/p...ategory_id=265 ).

Anybody who has any experience with this plane? Who can tell us how much g-forces the plane can handle? Or how thick the wing is?
Oct 14, 2009, 04:23 AM
Needs to do 52 legs !!
jjmouris's Avatar
I thinkt they are trying to get away buying an F5D plane on the schools budget.



Regarding wind speeds, you will not find wind strong enough to keep an F5D or even an F5B plane airbourne anywhere on this earth. Maybe on Mars it could work.

Airliners have to deal with "jetstreams", these are high speed winds that are at about 30.000ft altitude and higher. Those do get up to 100knots or more but there is no way you are going to get a teathered plane that high. The cable alone would be to long and heavy.

In other words, you need a much lower speed and wingloading plane. Suggest you have a look at the HLG / DLG section. Or better yet, forget about RC controlled planes and go for F1A and F1B free flight models. Those will do what you are considering nicely. Even the 20G momentary loading.
Oct 14, 2009, 07:14 AM
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Thread OP
Actually, school is making us buy a plane ;-)

In the beginning, we will swing around the plane in a circle of 4m in diameter, at speeds up to 80 km/h. This amounts to 20g of rotational forces.

We already have a glider (1.6m span), which we have got up to a speed of 100 km/h just using the wind while being tethered, using a cord of about 50m long. In the future, the cord-length will be much longer (300-600 m). The forces the plane will undergo are to high for our glider, and that's why we're looking an other plane.

Because of these high g-forces, we were advised to look at F5D-planes. We have posted a topic in the HLG section, but we have doubts that they are strong enough for these forces?
Oct 14, 2009, 02:51 PM
Registered User
A few parameters about F5D models you can consider. Attached is a picture of the FAI (F5D) pylon course. It’s a triangle with two 180m + one 40m segments = 400m total. Currently the models are achieving sub-60 second total times doing 10 consecutive laps ~ 4000m. But you have to factor the first laps are slower due to zero velocity hand launch & the true flight trajectory is not 3 triangle sticks. It’s probably closer to 450m/lap by skilled pilots. Our radar & on-board measurements indicate speeds of 300 km/hr, which fits pretty good with this total time & course trajectory cartoon. Assuming V=300 km/hr, turn radius of 20m & model weight of 1000g (rules minimum), I calculate centrifugal force of 35 kg = 35G’s. A 15m radius = 46 G’s.

In racing reality there is a tradeoff: sharp, low radius turns (high G) require proportionately high lift from the wing to sustain it. The wings can only deliver a max Cl before stalling (maybe its 0.7 or 0.8, I dunno) & the drag is climbing rapidly which translates into scrubbed speed through the turns. So even if a 15m radus turn is possible, which I think it is, F5D pilots may be turning softer & therefore longer trajectory if it means their goal total time is reduced.

But the important thing to note here vs your application (which I don’t quite understand) is these models ‘cycle’ between two different high-G turn modes & relatively straight line 1-ish G mode. For example, a 60 sec race = 6 secs per lap. But based on simple trajectory distance estimate, the model probably ‘turns’ pylon 1 in over 40-50m = 10% of total = 0.6 sec duration at high AOA. From a wing loading standpoint, that’s different than an airfoil operating in a sustained high G-load & high AOA say like a windmill or propeller blade. Because F5D models are built quite light to comply with class rules, you could construct them stronger just by adding more carbon in the sheeting, stronger core materials, stronger spars, more than 1 spar etc. So their G-load capability would improve, but not their aerodynamics.

You might want to check out Dynamic soaring models & construction methods which don’t have these constraints. They just keep adding carbon to get the job done! Some DS models are approaching 400 mph (600 kph) & you could probably get some insight from their videos or feedback what sort of equivalent turn radii they see. (It looks pretty similar to our pylon 2-3 from what I can judge). Another good source of info is Hepperle’s site.

http://www.mh-aerotools.de/airfoils/index.htm
Oct 14, 2009, 03:03 PM
DS JUNKY
I would expect a strong f5D plane to withstand 50g's. I'm not entirely sure what your research is trying to prove. The L/D on all these models is a big compromise based on what it is designed for. An airfoil suited for your task at hand will offer much better performance.
Oct 16, 2009, 09:25 AM
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Florrain's Avatar
Hello,
I suspect that in fact you intend to DS a plane on the line.
This can be done with F3B ships that use cycles through the wind gradient to increase speed and winch line stretch and then get an even stronger kick and zoom to high altitude.
I might be wrong but I think you are trying to achieve a similar type of cycle hence the high speeds you are speaking about.
My views on this type of flights is that you will need good directional control and an effective rudder as well as flaps to adapt to the very wide speed range and line pull that you will get.
For this reason, I think the tiny fins on F5D racers might be a problem.
Building one with flaps is always doable but I think looking a good 2m DS ship is probably a better option.

I know that DS has also been achieved with power off controle line ships but then the lines are attached to a wingtip and the best configuration for the plane is surely not symetrical. Wing, tailplane and fin geometry would definitely be asymetric for best performance and G loads will not be the same direction as an RC plane.
@+
FL


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