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Interesting Observation


poz
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For the past couple of years I have flown a Pap Thor 250 under a 27m Niviuk Link, clocking up a couple hundred hours. Here are the numbers:

Cruise rpm: 4800.

Consumption 2.8 lph

Speed (trims out) 28mph

Me: 85kg (bare arsed)

Machine (44kg with 6 litres)

However, I recently got a new wing, well the same wing but in a 23m version which in reality is considerably less fabric.

Cruise rpm: 4500.

Consumption 2.3 lph

Speed (trims out) 31mph

Me: 86kg (bare arsed) I've put on a kilo recently :(

Machine (44kg with 6 litres)

Smaller wing much easier to launch and land.

Very surprised with these numbers, I guess it's about parasitic and induced drag. Not sure which is more responsible for the better performance, but I have a feeling I'm going to be enlightened :) 

 

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  • 2 weeks later...

Hi Tom. Out of those 3 I have only flown the Link. My previous wing was a Revo 2 which I flew for 5 years and didn't have any bad experience apart from a glide ratio which was slightly better than a breeze block. Not entirely a bad thing as it's easier to predict where you will land, and if you have a tight space in which to come down, is essential. The Link is basically a PG wing so therefore has the opposite problem in that it doesn't want to come down. In a tight space with a warm field it's presented problems for me more than once.

Hope this helps.

Dan

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Poz. There could be many reasons why your numbers may not make sense..  If it is the Exact same wing with no Design changes..  The only things i would say would be different flying on that day, climbing harder, or higher.  A few 100 rpm over the hour will change your figure a fair bit

Are these figures from one flight?or average over X hours.... Did you weight the fuel in and then run out or weigh out left over fuel?   

I have noticed that different days will return different Eco figures with the same wing.  The 250 is great with atmospheric changes unlike some other engines/carbs and can be tuned lean way past where other engines  would go POP due to the great cooling,  Doing this you do risk long term bearing failure.. 

Your figure are around the same figures my Mac fly 250 customers are reporting Circa 3lph flying sub 20m wings. My Viper 3 22m was 2lph @ 115kg all up, My speedster2 24m is 2.3-2.4lph and my Viper 4 18m is 2.35...  Flying Faster with more agility when i want to play, and as an added bonus beating my old four stroke eco figures for around an extra 5kg added weight but with about 30kg's more thrust.. win win!!! 

 

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