Quagmirian

Mihawkler? OP, I can put together some rough plans as a starting point if you would like them.

Yeah, as I said, it's supposed to look technical and confusing without really showing anything. On the subject of panel shape, I can't help but notice that accuracy canopies often have a trapezoidal looking planform. Is this intentional or some unwanted side effect? Image taken from PD's facebook page. [inline pd_cropped_sized.jpg] Also, I finally found out what the 'STAB SLK' dimensions are on PD trim charts, and I have modified my stabiliser drawing appropriately. [inline stab_slack.png]

Thank you. If you like, you can jump the canopy when it is made. Here's a technical looking image which should hopefully make it look like I know what I'm doing, even though I have no idea. [inline 2740_194_150_stab_new_tilted_small.png] I think I've also decided on a name for this range of canopies, based on a similar looking older canopy. I don't think there'll be any confusion. [inline logo_idea2.png] In terms of where I go from here, I'm still faffing with some design details and what sort of seams I will use, but as soon as I can find somewhere to work I will begin production.

Learning on static line, my problem was the opposite of this. I remember vividly my first freefall from 5000 feet. 'SHIT, AM I REALLY GOING TO GET OUT THIS HIGH?' I also remember my first ride to full altitude, trying to not look down.

Call me a wuss, but I think pranks are best left on the ground.

Narrow risers with large rings? I think I know what my container choice will be then.

As far as I know, reducing the number of chordwise lines is actually a bad thing in terms of load distribution to the canopy. The fewer lines you have, the bigger the gap between them and the bigger the bulge upwards in the wing as there is less to support it. So at a certain point you will offset any reduction in line drag with a decrease in canopy efficiency. That could all be rubbish by the way, best to ask RiggerLee.

Am I wrong, or is that a 9 cell reserve? Not saying it had anything to do with the hesitation, just an observation.

I can't quite build an entire canopy at the moment due to a lack of that money stuff. However, I have managed to get a couple of copies of Poynter's manuals from the library, which I am certainly not scanning into my computer for later reference. I haven't read them from cover to cover yet, but there are a few things that have caught my eye. ***"In flight, the span of the ram air canopy is often shorter at the leading edge than at the trailing edge due to cell inflation"Have I got this wrong, or is this the reverse of what you were saying about aeroelastic issues, RiggerLee?

The Unit has no D lines I think.

Just when I think I understand what's going on, I'm reminded that I know nothing in the grand scheme of things. Oh well, at least I'm making an effort. How about this then. A 'twisted' topskin with more width towards the nose, allowing the end cells to open up properly, and a rectangular bottom skin, to counter the effects of ovalisation towards the tail. [inline parts4.png]

I think I have it. Here's what my panels look like without seam allowance. So is this twisting thing a good idea or not? Obviously it's only going to be perfect for one angle of attack, but it's better than having no twist at all, right? [inline parts3a.png]

I'll take it then.

I think, at last, I'm beginning to understand what you're talking about. Generating panel shapes is not just about making the top skins wider due to the anhedral, it's actually about trying to compensate for the reduced angle of attack towards the wingtips, if I understand correctly. I had to consider a donut shaped ram air canopy to understand this. Unless you put some twisting in the wing, it will not have an equal angle of attack over the whole wing. A normal canopy is only about a quarter of this donut but I think the same rules apply. If I have it correct, I can now see why rotating the rib about the angle of glide produces a better canopy. As you say, this will make the bottom skins trapezoids which are wider towards the leading edge, right? [inline rib_rotated_small2.png] In other news I have managed to get my local library to find some copies of Poynter's manuals. It'll cost me a bit to get them out but I'll no doubt have a lot of questions answered.

I drew it myself in PS. I used my new trim and I have also wrongly assumed that each line will be evenly tensioned. Is there any way I can improve this? The glide angle really is just a guess based on my current brown thing. I'm assuming in increase of glide from 2.5 to 3.5, based on a thinner airfoil, higher a/r etc. The trim is also just a guess from the last canopy. That was based on the Pd 7 cell and then flattened. This trim is based on a flattened PD 9 cell. I'm assuming that the suspension point will be at the 25% chord point. The aoa in full flight looks to be about 11 degrees, which makes it pretty flat trimmed. I do prefer flat canopies though. So this will just generally improve performance in all areas then? It sounds like a good idea and I can see where you are coming from.

A little update here. I've changed my design again. I'm going for a 210 sq ft nine cell, made from the same lovely coloured fabric I used for the brown thing. [inline parts.png] I got some brass grommets set in my slider, but due to a misunderstanding the inner diameters are only 3/4 of an inch. Is this big enough for a canopy lined with Dacron or will I have to go with Spectra? Also, here's a diagram which doesn't really show much but will probably convince some people that I know what I'm doing. [inline 2794_194_139_small.png]

Rascal?

Thanks for the replies. Nothing particularly exciting. [inline canopy_logo4.png]

I've had this same query myself. I rang up PD to ask about it and they won't tell where the cascade is for this exact reason; they don't want you manufacturing linesets. The only solution they suggest is to take a measurement from an existing canopy that is still in trim.

Yes, well, I do lots of stuff I shouldn't really do. At least now I know the stall point I can fly more confidently and work to make improvements. Someone just happened to be walking by when I was launching the other day and took these interesting but not necessarily useful pictures. [inline small1.jpg] [inline small2.jpg] [inline small3.jpg] [inline small4.jpg]

That sounds about right. I downloaded Javafoil and put my airfoil in it and I have no idea what I am supposed to be looking for. [inline javafoil.png]

Why can't rapide or soft links be used on tandem reserves?

I had a go at making a slider for my new project. [inline AK000003.JPG]

Every canopy I jump turns slowly to the right. I think my right leg is thicker than my left.

There are a few things I don't like about the brown thing. Firstly, the control range is a bit short on the toggles (it's a flat trimmed canopy), and secondly, the turns are a bit snappy after about half brakes. There's plenty of flare power and toggle pressure though, so I thought I'd try and solve these problems by moving the most inboard control line half a cell outboard, like this: [inline new_ust_config.png] Any thoughts?