Jkralovec 0 #1 September 27, 2009 First of all, I'm not thinking of getting a Velocity, I fly a Sabre2 135. As you know, my canopy has 9 cells and the specter has 7 cells... WHY do Velos have 21 cells??? Quote Share this post Link to post Share on other sites
airtwardo 7 #2 September 27, 2009 Cross Bracing of the wing for a smaller, more aerodynamic profile. Think of it as a really well reinforced 7 cell. ~ If you choke a Smurf, what color does it turn? ~ Quote Share this post Link to post Share on other sites
jcd11235 0 #3 September 27, 2009 A cell is defined as the chamber between load bearing ribs. If you count all of the chambers between the load bearing ribs on a Velocity, you'll get 21. Thus, the Velocity is a 21 cell canopy.Math tutoring available. Only $6! per hour! First lesson: Factorials! Quote Share this post Link to post Share on other sites
thedude325 0 #4 September 27, 2009 Quote WHY do Velos have 21 cells??? To annoy your packer... Quote Share this post Link to post Share on other sites
mjosparky 4 #5 September 27, 2009 QuoteA cell is defined as the chamber between load bearing ribs. If you count all of the chambers between the load bearing ribs on a Velocity, you'll get 21. Thus, the Velocity is a 21 cell canopy. Cell: The compartment formed by the top and bottom surfaces and two adjacent load bearing ribs. Each cell is usually divided by a non-load bearing rib to form two half cells. Cells are numbered from left-to-right by full-cell number; use left (L) and right (R) to designate the appropriate half cell. The entire compartment” between load bearing ribs is just one cell. Any divisions within this cell are “half cell” or in the case of Velocity 1/3 cell. It is a seven cell with 2 non load bearing ribs in each cell. Sparky Source: PIA TS-100My idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
diablopilot 2 #6 September 27, 2009 Interesting. The definition might need to be re-evaluated, since the function of a crossbrace is to transfer some of the load from the base of a load baring rib to the top of a non load bearing rib.Of course we could just stop calling them 21 and 27 cells and call them what they are, crossbraced 7 and 9 cell canopies. ---------------------------------------------- You're not as good as you think you are. Seriously. Quote Share this post Link to post Share on other sites
jcd11235 0 #7 September 27, 2009 QuoteQuoteA cell is defined as the chamber between load bearing ribs. If you count all of the chambers between the load bearing ribs on a Velocity, you'll get 21. Thus, the Velocity is a 21 cell canopy. Cell: The compartment formed by the top and bottom surfaces and two adjacent load bearing ribs. Each cell is usually divided by a non-load bearing rib to form two half cells. Cells are numbered from left-to-right by full-cell number; use left (L) and right (R) to designate the appropriate half cell. The entire compartment” between load bearing ribs is just one cell. Any divisions within this cell are “half cell” or in the case of Velocity 1/3 cell. It is a seven cell with 2 non load bearing ribs in each cell. Sparky Source: PIA TS-100 The diagonal ribs are load bearing ribs, hence 21 cells by the PIA definition.Math tutoring available. Only $6! per hour! First lesson: Factorials! Quote Share this post Link to post Share on other sites
airtwardo 7 #8 September 27, 2009 I thought they decided each load bearing rid had a line attachment? ~ If you choke a Smurf, what color does it turn? ~ Quote Share this post Link to post Share on other sites
jcd11235 0 #9 September 27, 2009 QuoteI thought they decided each load bearing rid had a line attachment? Don't the diagonal ribs share line attachments with the vertical ribs at the line attachments?Math tutoring available. Only $6! per hour! First lesson: Factorials! Quote Share this post Link to post Share on other sites
riggerpaul 1 #10 September 27, 2009 QuoteQuoteQuoteA cell is defined as the chamber between load bearing ribs. If you count all of the chambers between the load bearing ribs on a Velocity, you'll get 21. Thus, the Velocity is a 21 cell canopy. Cell: The compartment formed by the top and bottom surfaces and two adjacent load bearing ribs. Each cell is usually divided by a non-load bearing rib to form two half cells. Cells are numbered from left-to-right by full-cell number; use left (L) and right (R) to designate the appropriate half cell. The entire compartment” between load bearing ribs is just one cell. Any divisions within this cell are “half cell” or in the case of Velocity 1/3 cell. It is a seven cell with 2 non load bearing ribs in each cell. Sparky Source: PIA TS-100 The diagonal ribs are load bearing ribs, hence 21 cells by the PIA definition. I've got to go with mjosparky's interpretation here. In light of the new construction of a cross-braced canopy, the PIA specification needs some small changes to avoid ambiguity. In the PIA definition, a load bearing rib is one that has line attachments. In the past, the count of load bearing ribs and line attachment points was one and the same, and distinguishing between them was irrelevant. The spec also mentions that load bearing ribs are usually separated by non-loaded ribs, and that part of the definition becomes a bit ambiguous when you consider the construction of the Velocity. So now maybe it would be better to discuss the line attachment points directly, rather than indirectly though the concept of the loaded rib. I would argue that it is the line attachment points that are important, not the load bearing ribs. To be a cell, you really need a line attachment point on either side of it, or it will not be able to hold its shape when you inflate it. So, rather than saying "between load bearing ribs", the spec would say "between line attachment points". This altered definition is equivalent for a conventionally constructed canopy, and it is unambiguous when considering the construction of the Velocity as well. Quote Share this post Link to post Share on other sites
jcd11235 0 #11 September 27, 2009 Agreed. If the definition of a cell is changed as you describe, then a Velo would be considered a seven cell canopy. As the definition stands currently, I don't see the ambiguity, nor, apparently, do Performance Designs.Math tutoring available. Only $6! per hour! First lesson: Factorials! Quote Share this post Link to post Share on other sites
riggerpaul 1 #12 September 27, 2009 QuoteAgreed. If the definition of a cell is changed as you describe, then a Velo would be considered a seven cell canopy. As the definition stands currently, I don't see the ambiguity, nor, apparently, do Performance Designs. The ambiguity, as I see it, is that the diagonals, while clearly load bearing, have only another load bearing rib between them. This very different from what the current definition leads you to expect. With the current definition and a conventional construction, you can have any number of cells that you want. There has, in fact, been an eight cell canopy, of conventional construction. With conventional construction and the current definition, we have seen 5 cell, 7 cell, at least one 8 cell, and 9 cell canopies. No problem applying the definition to any of these. With the Velo, if you are calling it a 21 cell canopy, you cannot make anything that is not a multiple of 3. So I have a problem calling each of those things "cells". In my view, a "cell" should be an indivisible unit of construction. You should be able to make a 1 cell airfoil. But you cannot do that if you are saying that a Velo is 21 cells. If you use the line attachment as the defining attribute, the definition can be applied uniformly to a canopy that uses either conventional or cross-braced construction without any sort of confusion. Look at the line trim chart for a Velocity and you clearly see that it has 7 repetitions of something. If you want to say it has 21 cells, then the definition of cell is not consistent. If it is 21 cells, tell me, where is the middle cell of the first 3, and how does it relate to the PIA definition of a cell? Would you be saying that the middle of the first 3 cells is that one that has a non-bearing rib on either side? That doesn't fit the current definition at all. Calling it 21 cells is just a marketing concept. Over the years, we came to a sort of conclusion that "More cells equals more performance". This held true with the progression from 5 to 7 to 9 cells. Performance is really about aspect ratio, drag, rigidity of the wing, and stuff like that, not the number of cells, per se. In the end, the current PIA definition cannot really be used to describe a Velocity at all, so using it to count the cells doesn't really make much sense. To describe a Velocity, we NEED to modify the PIA definition. The easiest way to do that is to talk about the line attachment points, and when you do that, the Velo is a 7 cell. Quote Share this post Link to post Share on other sites
jcd11235 0 #13 September 27, 2009 QuoteIn the end, the current PIA definition cannot really be used to describe a Velocity at all, so using it to count the cells doesn't really make much sense. Sure the definition can be used to describe a Velocity. Counting each cell, i.e.each compartment formed by the top and bottom surfaces and two adjacent load bearing ribs, we come up with 21 cells. Until PIA changes the definition of a cell, the Velocity is legitimately called a 21 cell canopy. It isn't a marketing ploy; it's an adherence to the definition of a cell as defined by PIA. Whether or not PIA should change the definition is a separate topic and one deserving of it's own thread.Math tutoring available. Only $6! per hour! First lesson: Factorials! Quote Share this post Link to post Share on other sites
Sangi 0 #14 September 27, 2009 I'm surprised that nobody has started bitching yet that 83 jump wonder flies a 135 Sabre2..."Dream as you'll live forever, live as you'll die today." James Dean Quote Share this post Link to post Share on other sites
riggerpaul 1 #15 September 27, 2009 QuoteQuoteIn the end, the current PIA definition cannot really be used to describe a Velocity at all, so using it to count the cells doesn't really make much sense. Sure the definition can be used to describe a Velocity. Counting each cell, i.e.each compartment formed by the top and bottom surfaces and two adjacent load bearing ribs, we come up with 21 cells. Until PIA changes the definition of a cell, the Velocity is legitimately called a 21 cell canopy. It isn't a marketing ploy; it's an adherence to the definition of a cell as defined by PIA. Whether or not PIA should change the definition is a separate topic and one deserving of it's own thread. I need to understand exactly which sections you are calling a cell. To begin, I think you are saying that between 2 line attachments, there are 3 cells. Is that right? Now I'll try to describe what I think you mean when you talk about the first of the 3 cells. Each of the line attachment points has a roughly vertical rib above it. Is the first cell the compartment formed by the aforementioned rib, the top skin, and the diagonal rib? If this is not what you mean by the first cell, please explain where the first cell is. Anyway, now on to the second of the 3 cells. Is the second cell the compartment between the two cross-bracing loaded ribs, including the 2 unloaded ribs? Is the third cell the compartment between the second cross-bracing loaded rib and the next roughly vertical rib? Is this about how you are defining the 3 cells that are between 2 line attachment points? If so, I do not accept that your first and third cells have any bottom skins. The compartments I described as the first and third cells are triangular. They have a top and two sides, but no bottom, or rather, the bottom is a line going from front to back, not a skin. According to the definition, and according to your own post, you need a top skin and a bottom skin to talk about a cell. If you are defining the cells differently from what I described here, please explain to me where each of the 3 cells between the line attachment points are. (Really, I'm not being sarcastic here. I just what to understand what you are calling a cell. Because we can't really discuss it if we aren't understanding what you call a cell.) Quote Share this post Link to post Share on other sites
jcd11235 0 #16 September 27, 2009 QuoteI need to understand exactly which sections you are calling a cell. I am using the PIA definition of a cell: the compartment formed by the top and bottom surfaces and two adjacent load bearing ribs. Each chord-wise row of line attachments (except the outermost line attachments) is connected to three load bearing ribs, one vertical and two diagonal. QuoteTo begin, I think you are saying that between 2 line attachments, there are 3 cells. Is that right? Yes, since the PIA definition defines cells in terms of load bearing ribs and not line attachments. QuoteEach of the line attachment points has a roughly vertical rib above it. Is the first cell the compartment formed by the aforementioned rib, the top skin, and the diagonal rib? In addition to the intersection along the bottom skin, yes. QuoteIs the second cell the compartment between the two cross-bracing loaded ribs, including the 2 unloaded ribs? Yes, which is consistent with the PIA definition. QuoteIs the third cell the compartment between the second cross-bracing loaded rib and the next roughly vertical rib? Yes. QuoteIs this about how you are defining the 3 cells that are between 2 line attachment points? No. That is a decent description, but I am defining the cells as PIA does, i.e. each compartment formed by the top and bottom surfaces and two adjacent load bearing ribs. QuoteIf so, I do not accept that your first and third cells have any bottom skins. They intersect with the bottom skin, fulfilling the definition's requirements.Math tutoring available. Only $6! per hour! First lesson: Factorials! Quote Share this post Link to post Share on other sites
riggerpaul 1 #17 September 27, 2009 QuoteQuoteIf so, I do not accept that your first and third cells have any bottom skins. They intersect with the bottom skin, fulfilling the definition's requirements. The PIA document defines a cell as, "The compartment formed by the top and bottom surfaces and two adjacent load bearing ribs." I read that to say that a cell has 4 sides - top skin, bottom skin, left rib, and right rib - that combine to enclose a space. Some of the cells as you count them are triangular, having only 3 sides. The bottom skin that intersects does not serve to define the compartment. That, in a nutshell, is why I don't think it is correct to call a Velocity a 21-cell canopy. I don't expect that we will come to an agreement on this. That's okay. At least we are clear about how and why we disagree. Quote Share this post Link to post Share on other sites
jcd11235 0 #18 September 27, 2009 QuoteI read that to say that a cell has 4 sides I don't believe that interpretation to be justified by the definition. We'll have to agree to disagree.Math tutoring available. Only $6! per hour! First lesson: Factorials! Quote Share this post Link to post Share on other sites
DeNReN 0 #19 September 28, 2009 When I pack a Velo...I count 7 cells when flaking the nose....... Quote Share this post Link to post Share on other sites
diablopilot 2 #20 September 28, 2009 Quote When I pack a Velo...I count 7 cells when flaking the nose....... and I count 14---------------------------------------------- You're not as good as you think you are. Seriously. Quote Share this post Link to post Share on other sites
virgin-burner 1 #21 September 28, 2009 Quote I'm surprised that nobody has started bitching yet that 83 jump wonder flies a 135 Sabre2... having jumped again, you really got some sense back, ey!? “Some may never live, but the crazy never die.” -Hunter S. Thompson "No. Try not. Do... or do not. There is no try." -Yoda Quote Share this post Link to post Share on other sites
Jeffrey 1 #22 September 28, 2009 As Sparky mentioned, have a close look at page 1 of TS100-AT. The committee wants to update it. http://www.pia.com/PIAPUBS.htm Jeff Quote Share this post Link to post Share on other sites
DeNReN 0 #23 September 28, 2009 Quote Quote When I pack a Velo...I count 7 cells when flaking the nose....... and I count 14 Please explain Quote Share this post Link to post Share on other sites
phoenixlpr 0 #24 September 28, 2009 One cell of the cross-braced is divided in 3 and the middle part is closed.... Quote Share this post Link to post Share on other sites
DeNReN 0 #25 September 29, 2009 Quote One cell of the cross-braced is divided in 3 and the middle part is closed.... Do you count 7 or 14 when flaking the nose on a velo? Quote Share this post Link to post Share on other sites
