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Longest Freefall RC Skydiver

Our fun RC record attempts.

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pietermu
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Re: Longest Freefall RC Skydiver

Unread post by pietermu »

OK what I will do is to put my Altimeter on the the skydiver. it is built for rockets the altimeter so it will pickup also the velocity as well on the recording. I will get back with my findings and maybe post the Excel sheet of the downloaded recording also.
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Re: Longest Freefall RC Skydiver

Unread post by MegaTesla »

sabackflipper wrote: I think the figure of 10m/s represents acceleration due to gravity. So for the first second the skydiver will fall at 36km/h. Second number 2 will see the skydiver reach 72km/h, and this will continue until terminal velocity is reached. Someone please correct me if I'm wrong.
You're correct.

The math gets really complicated to do if exact air resistance (drag) is taken into consideration. Since we do not know the exact drag we can guess terminal velocity. Let's take a guess that the skydiver will reach a terminal velocity of 12m/s (50.4km/h).

If we do NOT take drag into account, the distance that it will travel to reach that speed is:
s=(v^2 - u^2)/(2a) , where v = end velocity, u = starting velocity, a = 9.8m/s^2 gravity
s=(12^2 - 0)/(2*9.8 )
s=144/19.6 = 7.35m

Time it will take to reach that.
s=ut + 0.5at^2
7.35=0 + 0.5(9.8*t^2)
t^2=1.5s
t=1.2s

Now assume it will actually take twice as long to reach that speed with air resistance. I'm guessing distance travelled will be around 20m. This is rather insignificant...

When travelling at a constant speed the math is easy. For a 40s free fall, minus 2.4s to reach terminal velocity:
s=vt
s=12*37.6=451.2m

So total height was probably around 470m. If this sounds too high it means the skydiver's terminal velocity is less than 50km/h.

I might be completely wrong, but this is how I see things.

Pieter
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gideon.edge540
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Re: Longest Freefall RC Skydiver

Unread post by gideon.edge540 »

Pieter
Het my A-license gekry met skydive en gaan nou vir Skydive Sam saam opvat met n Ditter, meet die spoed waarteen hy val en hoe lank hy geval het ens, dan kan ons die spoed sien waarteen hy val en nie te wonder wat die spoed is nie.
Die skydiver Sam teel nou redelik vinnig aan en ons sal moet begin oefen vir skaal hierdie jaar en julle moet ook kyk of julle kan af kom vir skaal sodat ons kyk of ons laas jaar se rekord kan verbeter.
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Re: Longest Freefall RC Skydiver

Unread post by pietermu »

Dit sal gaaf wees van jou Gideon. Ons sal ook nog dieselfde tipe ding diekant doen. Daar sal natuurlik ook 'n verskil wees in info a.g.v van die verskil in ASL. Ek sal graag wil sien wat jou bevinding is. Ek neem aan jy gebruik die Pro Dytter!

Ek verstaan so in die geledere van die aanteel.
Ja, die skaal hoop ek om die jaar by uit te kom. Kom draai jul weer by Henley die jaar?
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Re: Longest Freefall RC Skydiver

Unread post by gideon.edge540 »

Yes Pieter
Ons sal jul seker weer sien by Henley en weer so maak soos laas jaar en dit weer geniet.
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Re: Longest Freefall RC Skydiver

Unread post by rcskydiver »

OK, its been a while but at last we had the chance to strap a skydive data logger to our diver to solve the question: How fast is the freefall speed? :D

We used a VISIO 2, which is used in real life skydiving as a altimeter and data logger and works on the differences in barometric pressure to do its calculations during freefall. Just being slightly bigger than a watch made it perfect to test on our diver!!

Some stats of the logger:
Jump 1: Height 701m, deployment altitude 268m, freefall distance: 433m, freefall time 21 sec, gives avg speed of 20.62m/s
Jump 2: Height 865m, deployment altitude 182m, freefall distance: 683m, freefall time 33 sec, gives avg speed of 20.69m/s

The average speed was calculated using the average of the two jumps 20,655m/s x 3,6(to convert to km/h) = 74,35km/h

The max it peaked at was 79km/h and avg speed under canopy was 34km/h(max speed was 47km/h, this was flying downwind back to the field)

These stats also show just how stable the diver was in freefall to achieve these close averages!!

At least now we know its not hurtling towards the ground the same speed as we do!! :lol:

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Re: Longest Freefall RC Skydiver

Unread post by rcskydiver »

Oh while I'm here,

The highest double drop of a rc plane as far as we know was raised to 932m by Kobus Stofberg and myself, we sacrificed the freefall time in exchange for some very long canopy ride time!!!

Both divers were flown back and caught in our hands!!
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Re: Longest Freefall RC Skydiver

Unread post by pietermu »

rcskydiver wrote:Oh while I'm here,

The highest double drop of a rc plane as far as we know was raised to 932m by Kobus Stofberg and myself, we sacrificed the freefall time in exchange for some very long canopy ride time!!!

Both divers were flown back and caught in our hands!!
=D> =D> Very nice Fanie. Congrats to both you and Kobus on the high altitude drop :!:

Johan and I earlier in this year took Bastardio to 1300m without a jumper. Would have loved to do the jump from there.

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Re: Longest Freefall RC Skydiver

Unread post by Nico Rautenbach »

pietermu wrote:
rcskydiver wrote:Oh while I'm here,

The highest double drop of a rc plane as far as we know was raised to 932m by Kobus Stofberg and myself, we sacrificed the freefall time in exchange for some very long canopy ride time!!!

Both divers were flown back and caught in our hands!!
=D> =D> Very nice Fanie. Congrats to both you and Kobus on the high altitude drop :!:

Johan and I earlier in this year took Bastardio to 1300m without a jumper. Would have loved to do the jump from there.

Blue skies!
Hi all! Pieter lanklaas gesien!!!

Acceleration of Gravity =9.8m/s/s

Vf=g*t

Vt=(9.8m/s2)*ts=_m/s

Distance=d

d=(0.5)*(9.8m/s2)*(8s)2=_m

Hope this helps!! :wink:
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pietermu
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Re: Longest Freefall RC Skydiver

Unread post by pietermu »

NASAFI event 3-8 October 2016
Attempt: 8 October 2016
Low Cloud base (900m AGL)
Drop was estimated at 1150m AGL due to failure of GPS reading.
55cc Stick: Marius Marais(Tzaneen)
Timekeeper: Jan Fourie(Springbok)
Skydiver 1; Definite 45s free-fall was achieved: Hannes Hattingh(Centurion)
Skydiver 2; None event
Perfect deployment with perfect landing on target.
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Re: Longest Freefall RC Skydiver

Unread post by Airbandit »

#-o Cool video
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Re: Longest Freefall RC Skydiver

Unread post by Wonko the Sane »

Pietermu

Het iemand dalk al vir hettie saam gevat op ‘n regte dive om te sien hoe sy travel. Ek het al saam ‘n tennis bal en golf bal geval en dit was interresnant om te sien hoe hulle verskil... geen video...sorry...baie lank terug... miskien kan jy jou tx saam vat om haar te werk.... :shock: :? :? 8) :lol: :lol: :lol:

W
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Re: Longest Freefall RC Skydiver

Unread post by Wonko the Sane »




W
I don't care what you think of me! Unless you think I'm awesome - then you're right, carry on!

My flying is not that bad....I've never left one up there..

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