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are we interested in air speed or ground speed ? Does it matter

Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

are we interested in air speed or ground speed ? Does it matter

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Old 02-10-2009, 12:26 PM
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mk1spitfire
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Default are we interested in air speed or ground speed ? Does it matter

Just curious how people feel about this. I mean with the wind you planes ground speed is consiberly more as it speeds past you. That ground speed is surley the refection how fast you model feels.?
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Old 02-10-2009, 12:30 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

If I can feel the air pound my chest when it goes by I'm good

When we did our rally we used a radar gun so I guess that's pretty close to ground speed. For me it isn't a big deal just a refrence point to base how crazy I am. [sm=what_smile.gif]
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Old 02-10-2009, 01:11 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter


ORIGINAL: mk1spitfire

Just curious how people feel about this. I mean with the wind you planes ground speed is consiberly more as it speeds past you. That ground speed is surley the refection how fast you model feels.?

To me, ground speed is irrelevant information - I am only interested in how fast it is moving through the air it's in, since how it feels and responds in the air is a direct reflection of its airspeed. As to visual impression, if I am flying a fast airplane I am not sure I even am aware of the difference in ground speed upwind or downwind to be honest, although I guess I might notice it from time to time. With a slow airplane then sure it's noticable, but that does not apply here.

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Old 02-10-2009, 01:23 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

You say that with the wind the airplane feels how fast its ground speed is? That is not accurate. I fly full scale planes also and I will tell you that if a plane has a 45 kts tail wind and you are already flying at 150 knots (Airspeed) then your (groundspeed) is 195 knots but your airspeed stays. The airplane does not know or feel that it is going that extra 45 kts therefore it is not affecting anything other than ground speed fuel efficiency, and getting somewhere much faster. {An example} (Never exceed speed) for a full scale airplane is different in that since because if your never exceed speed is 175 and you are going 195 ground speed the airplane doesn't know that you are going over 170 kts because it thinks your still going 150 kts, so therefore you are not exceeding the aircrafts limits.

Very simple actually.



Matt
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Old 02-10-2009, 01:28 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

When a car or fast motorbike passes you at high speed, you notice that. .!!!!

The bonus of ground speed is the downwind leg is percieved to be faster with aircraft.

As you watch and fly your plane as it zooms past yourself the ground speed is very relevant.
These gizmo that measure speed are airspeed so guess you just add wind speed on for ground speed.


Are doppler checkers airspeed only?
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Old 02-10-2009, 01:32 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter


ORIGINAL: Patterndude1

You say that with the wind the airplane feels how fast its ground speed is? That is not accurate. I fly full scale planes also and I will tell you that if a plane has a 45 kts tail wind and you are going 150 knots then your groundspeed is is 195 knots but your airspeed stays. The airplane does not know or feel that it is going that extra 45 kts therefore it is not affecting anything other than speed. {An example} (Never exceed speed) for a full scale airplane is different in that since because if your never exceed speed is 175 and you are going 195 ground speed the airplane doesn't know that you are going over 170 it thinks your still going 150, so therefore you are not over the stress limit.

Very simple actually.



Matt
Yer, though if you are not in the plane and only watching the plane as you generally do with a rc model then the ground speed is whats relevant surley?? Just as a fast car whizzes past you.(ground speed)
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Old 02-10-2009, 01:34 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

Why would ground speed be relevant in your oppinion? Ground speed doesn't really matter for an rc airplane.
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Old 02-10-2009, 01:37 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

If something whizzes past you, wether its a car on the ground or a rc model 1 foot off the deck then the speed of that object is detected by the eye as shifting fast reletive to ground speed.
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Old 02-10-2009, 01:40 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

It's all about bragging rights [8D]
Again back to our rally we took readings from two readings in each direction and gave an average of the fastest one in each direction. None of it really matters other than talking trash with the other fast guys.
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Old 02-10-2009, 01:42 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter


ORIGINAL: vicman

It's all about bragging rights [8D]
Again back to our rally we took readings from two readings in each direction and gave an average of the fastest one in each direction. None of it really matters other than talking trash with the other fast guys.
Ha..! I reckon Im faster than you.!!!
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Old 02-10-2009, 02:07 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

Case in point

We use the whole mile over here not a klik.[8D]
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Old 02-10-2009, 02:14 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

In Wyoming and S. Dakota the downwind leg is faster no matter what your doing.

GAWD this place sucks sometimes!! lol
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Old 02-10-2009, 06:25 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter


ORIGINAL: mk1spitfire

Are doppler checkers airspeed only?
Doppler is ground speed. No bragging rights for ground speed in my book.
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Old 02-12-2009, 10:25 AM
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Default RE: are we interested in air speed or ground speed ? Does it matter

What a great thread... This question comes up fairly often in different forms. The most common form is the, "my Patriot/OS .55 goes 180mph and I've got radar to prove it", thread. That turns into
"well... maybe... down hill... at 6,000ft... with a 30mph tail wind". This usually ends with "yes you have 180 on a radar gun, but no, you are not really doing 180 with an OS .55". The obvious crux of the question is, do you mean ground or airspeed?

For me, when these discussions come up (for bragging rights), you need to look at the average of two, level, passes in opposite directions. Without this I could launch an LT-40 in a hurricane and, for at least for a short period of time, claim I had a 200mph trainer with an OS LA .40 and I've got radar to prove it!

Bill
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Old 02-12-2009, 10:36 AM
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Default RE: are we interested in air speed or ground speed ? Does it matter

Bill,
Thats what we did with the speed rally we held last year. We had two passes in each direction and took the average of the two fastest.

The thing that really struck me was how the pylon racing planes had the same speed within say 4-5 mph in both directions. The next thing that I found interesting was the tremendous drop in speed from the hotliners. They would blow by the first time with incredible speed but after that they would drop 20+ mph with every pass. I expected some drop but not that much.

If you are interested we logged the speeds, model type, and power system on our website for people wanting to see what did well.
http://www.caldwellaeromodelers.com/...dSheet2008.pdf

You will notice we had a wide variety of planes show up. It really was a fun event.
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Old 02-12-2009, 03:08 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

I enjoy watching the entire flight. When I see the plane at X speed unload to V max in the dive, I enjoy that portion of the flight as much as I do watching the plane gradually lose momentum during the level pass, then I get a kick out of watching it climb to do a return pass. I also like knowing what all the speeds involved were, in a dive and on the flat. If by chance my plane hits 180 in a dive, then I enjoy knowing that...and no one is going to tell me any different or how I should go about enjoying myself. I especially love watching the downwind passes, it's like Mother Nature has hit the nitrous button for me.
For those who think they deserve a Medal of Honor for only acknowledging the level speed in calm air, have at it...but don't try to tell me how I should play with my toys.
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Old 02-12-2009, 05:35 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter


ORIGINAL: combatpigg
...but don't try to tell me how I should play with my toys.
I like flying backwards over the ground in a stiff breeze and downwind passes are fun, but no bragging rights.
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Old 02-12-2009, 09:00 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

Bragging rights to what? The North American piston / prop driven speed record? What is that record BTW and who has bragging rights to it?
Everyone else is either in 2nd place or worse and has a lot of catching up to do.....
the record on this continent is probably held by a FAI pylon racer.
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Old 02-12-2009, 09:57 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

Now would that be indicated airspeed or calibrated airspeed
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Old 02-12-2009, 09:59 PM
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Default RE: are we interested in air speed or ground speed ? Does it matter

C'mon Mike, Don't be a prude.
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Old 02-13-2009, 12:25 AM
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Default RE: are we interested in air speed or ground speed ? Does it matter


ORIGINAL: combatpigg

Bragging rights to what? ...
How fast their airplane is. A lot of people make speed claims and it would only make sense if those that do use the same guide lines. Claiming 200 mph when they neglected to tell you there was a 40 mph tail wind is worthless, don't you think?
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Old 02-13-2009, 12:26 AM
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Default RE: are we interested in air speed or ground speed ? Does it matter


ORIGINAL: RocketRob

Now would that be indicated airspeed or calibrated airspeed
How about True airspeed?
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Old 02-13-2009, 12:28 AM
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Default RE: are we interested in air speed or ground speed ? Does it matter


ORIGINAL: vicman

C'mon Mike, Don't be a prude.
Maybe we should add in the Earth's rotation. [X(]
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Old 02-13-2009, 12:51 AM
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Default RE: are we interested in air speed or ground speed ? Does it matter


ORIGINAL: mk1spitfire

.............That ground speed is surley the refection how fast you model feels.?

to me the plane has more 'feel' when going into the wind, flying in 30-35 knot winds the down wind leg is considerably smoother and groves right along, with the head wind it's bumpy and more pitchy. as far as speed i go by indicated air speed (JetCat sensor) as the plane could care less about ground speed, stall speed is determined by allot of factors with ground speed NOT being one of them.
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Old 02-13-2009, 01:24 AM
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Default RE: are we interested in air speed or ground speed ? Does it matter

Mike, someone else pointed out that a .40 sized trainer could go 200 in a tornado. I say, what's wrong with that? If I was witness to a plane that was under my control going 200 and was able to "take it all in", I would get a kick out of knowing that it did 200. I would tell the World [and I doubt that this trick has ever been done].
When a DSer is radared at the bottom of a dive, does his speed "count"? It does to him and that is all that matters. It is just a matter of degree how far you want to take the "unassisted" part of the equation for what you think counts. Maybe the only recognized clockings should be with no dive what-so-ever, just level passes? Set the ceiling at 50 feet and clock the plane in a 665 foot stretch in zero wind only [none of that 2 way average BS for me].
This forum isn't really about extreme speed, never has been. The only extreme speed guys [except for ILJ] have been run out of here for being too hardcore. If a guy wants to come here and claim 200, share his set up, talk about how it was clocked, etc., I'm all for it, it's not meaningless to me.
If a guy wants to come here and talk about a RC garbage can lid that he clocked at 200, I'll read about that with some interest, too.
I don't think any of it is worthless or meaningless, all the claims have some relative value. I come here to learn and to be entertained and the claims are just numbers...no matter where they come from.
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