It seems strange that 2 gliders of the same class could have such different weights.
The Northwing Horizon ET 180 is listed at 55lbs
http://www.northwing.com/horizon-hang-glider.htm
The Wills Wing Sport 2 175 is listed at 70lbs
http://www.willswing.com/prod2.asp?theC ... del=Sport2
I did notice the Horizon is listed as a Hang2 and Sport 2 as a hang 3 glider
The double surface on the Sport 2 is 74%
60% on the Horizon.
The horizon also has a soft rubber trailing edge on the down tubes so if ground handling is your biggest concern than you should take notice.
Still I don't know how they save 15lbs, does it have a crossbar?
Northwing Horizon 180 15lbs lighter than WW Sport 2 180
Moderator: Chip
About 8 of those 15 lbs comes from the 7000 series aluminum.
To get a better comparison, look at the weight of the sport 2 155.
Here is what WW says about the issue
Question:
Why does the Sport 2 175 size have 6061 leading edges?
Answer:
All current Wills Wing models use 7075 aluminum in the leading edges, except for the Sport 2 175 and the Falcon Tandem. Why do these gliders use 6061 leading edges? The answer lies in understanding what is different between the two materials, along with what is not different. The 7075 T6 alloy is approximately 75% stronger than 6061-T6. This allows the designer to use 7075 in a thinner wall tubing, typically .035 inches instead of .049 inches, and thus achieve substantial weight savings - typically six lbs in an entire glider airframe. Because of this significant advantage, Wills Wing designer Steve Pearson pioneered the large scale production use of 7075 in hang glider airframes twenty years ago, when 6061 was the universal industry standard, an innovation that some manufacturers have only recently adopted, and in most cases only on their competition class gliders. At the same time, while 7075 is inherently much stronger than 6061, it has the same "modulus of eslaticity" or inherent material stiffness. As a result, a leading edge made to the same strength in 7075 will be, because of the thinner wall, somewhat more flexible than an equivalent strength, thicker wall, 6061 leading edge. In most design applications, this is not a problem. However, when designing a wing for the broadest possible range of load carrying capacity, the ability to retain aerodynamic performance and optimum handling qualities across a wide range of loadings can depend very significantly on the degree of stiffness of the airframe. The stiffer 6061 leading edges used on the Sport 2 175 and Falcon Tandem allow these gliders to preserve the designed wing shape more effectively to very high wing loadings, which in turn allows these gliders to more effectively retain their intended flight performance and handling qualities across their larger than normal range of recommended pilot weights.
To get a better comparison, look at the weight of the sport 2 155.
Here is what WW says about the issue
Question:
Why does the Sport 2 175 size have 6061 leading edges?
Answer:
All current Wills Wing models use 7075 aluminum in the leading edges, except for the Sport 2 175 and the Falcon Tandem. Why do these gliders use 6061 leading edges? The answer lies in understanding what is different between the two materials, along with what is not different. The 7075 T6 alloy is approximately 75% stronger than 6061-T6. This allows the designer to use 7075 in a thinner wall tubing, typically .035 inches instead of .049 inches, and thus achieve substantial weight savings - typically six lbs in an entire glider airframe. Because of this significant advantage, Wills Wing designer Steve Pearson pioneered the large scale production use of 7075 in hang glider airframes twenty years ago, when 6061 was the universal industry standard, an innovation that some manufacturers have only recently adopted, and in most cases only on their competition class gliders. At the same time, while 7075 is inherently much stronger than 6061, it has the same "modulus of eslaticity" or inherent material stiffness. As a result, a leading edge made to the same strength in 7075 will be, because of the thinner wall, somewhat more flexible than an equivalent strength, thicker wall, 6061 leading edge. In most design applications, this is not a problem. However, when designing a wing for the broadest possible range of load carrying capacity, the ability to retain aerodynamic performance and optimum handling qualities across a wide range of loadings can depend very significantly on the degree of stiffness of the airframe. The stiffer 6061 leading edges used on the Sport 2 175 and Falcon Tandem allow these gliders to preserve the designed wing shape more effectively to very high wing loadings, which in turn allows these gliders to more effectively retain their intended flight performance and handling qualities across their larger than normal range of recommended pilot weights.
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addicted2climbing
- Posts: 182
- Joined: Mon Aug 20, 2007 9:50 pm
Hey OP,
While Wills reply makes sense they could have still used 7075 in a different wall thickness than the standard 7075 used in other gliders that would have still shaved weight and also would retain the same flex as the current 6061 leading edges. Only reason I see for not doing this is if in doing so it required a wall thickness that was not common to the tube manufacturer and therefore would not hav ebeen cost effective for a special ID tube diameter.
I want a glider frame made of Berillium. It would be rediculouly stiff and super light. Yet I was just quoted for a work project that a .625" diameter x 10" long tube is $500 and I need 2ea. So no way would that work price wise for aviation. Sure it being so stiff would be a bad thing as well.
Marc
While Wills reply makes sense they could have still used 7075 in a different wall thickness than the standard 7075 used in other gliders that would have still shaved weight and also would retain the same flex as the current 6061 leading edges. Only reason I see for not doing this is if in doing so it required a wall thickness that was not common to the tube manufacturer and therefore would not hav ebeen cost effective for a special ID tube diameter.
I want a glider frame made of Berillium. It would be rediculouly stiff and super light. Yet I was just quoted for a work project that a .625" diameter x 10" long tube is $500 and I need 2ea. So no way would that work price wise for aviation. Sure it being so stiff would be a bad thing as well.
Marc
You have asked the right person,
7000 and 6000 series aluminum have nearly the same modulus but vastly different ultimate strengths.
So you can use thinner 7000 series and get the same strength,
Yet no matter which you use; when it gets thinner it gets flexyier.
They are saying to get the rigidity they had to go thicker, and since it was so thick... might as well just use less expensive and better corrosion resistance of 6000 series.
Also I know a bit about Beryllium as well. I had a super cool tour of the plant that is making the james webb space telescopes mirrors.
1. its super poisonous
2. Yes it is stiff and light. the lightest and stiffest thing with any mechanical properties. (Li is lighter, but has no mechanical value to speak of)
3. Its kinda weak. In order to get the strength required, its going to take a bunch of it.
CFRP (carbon fiber) is way to go.
7000 and 6000 series aluminum have nearly the same modulus but vastly different ultimate strengths.
So you can use thinner 7000 series and get the same strength,
Yet no matter which you use; when it gets thinner it gets flexyier.
They are saying to get the rigidity they had to go thicker, and since it was so thick... might as well just use less expensive and better corrosion resistance of 6000 series.
Also I know a bit about Beryllium as well. I had a super cool tour of the plant that is making the james webb space telescopes mirrors.
1. its super poisonous
2. Yes it is stiff and light. the lightest and stiffest thing with any mechanical properties. (Li is lighter, but has no mechanical value to speak of)
3. Its kinda weak. In order to get the strength required, its going to take a bunch of it.
CFRP (carbon fiber) is way to go.
