As it happens, I have found someone relatively local who will let me use their facilities. I know in the long term I will need my own machines etc, but for now I just need someone to show me the ropes and fill me in with some rigging knowledge and experience.
I build my canopies without folders. I just pin the fabric together at the reference marks on the top skins. And for the bottom seam I just pin the A B C and D, and fold by hand as I go. I really don't think I would be all that much more efficient with a folder, especially switching from one folder to the other etc. I have no plans to buy folders in the foreseeable future.
Last time I was in the badseed loft, his technicians were all building canopies without folders as well.
Hmmm. I guess I think a little differently. How many employs have you had? There are a couple of things that can really get you into the mind set of automation. The first is building big batches of things by your self. It really teaches you to break production down into stages where all the task are done together at one station or one configuration. The second is employees. It teaches you how to make things stupid. Stupid as in unskilled, thoughtless, automated. Folders are a part of that. If you can train them to use the folder, that's a big if, it's your best bet to get the consistence you need from an employ. And even doing it your self it can speed your own work once you become proficient with their use. As an example I love my lap seamer. And it's not a big deal to set some of these up. As an example the lap seamer is just on a front plate. The plane one slides out and the folder slides in, done. A tape foot in not in the way most of the time and I often just leave it on the 1/4 gauge. Same thing with the roll holder, doesn't bug me. The puller on the 116 is a bit of an annoyance some times but I can still do 90% of the things I would do with that machine. If it's annoying then I'll drop a straight head into one of the other tables.
What I'm basically saying is that they are tools. You can do a job with out the right tool but it's so much easier if you're set up right. If you're doing enough of one thing, and main seaming a canopy falls in that category, then I think a good folder can be worth it's weight in gold. And they cost about that much.
Well, I don't fold my top seams over on my non load bearing ribs, I just do a 1cm raw finish seam. For the bottom non load bearing seam and I just fold it in half, but its all along the block of the fabric so its easy sewing once you get it started. For the top non load bearing seams, I do a 1cm raw finish seam, and i just make 2 passes on a single needle. And for the bottom load bearing seam, I just hold like 20" away from the foot, and fold it as I go. The only seam that I think would really be any faster would be the top load bearing seam.
Two passes with a single needle? Dude you got to get a double. Not just because it's a singe pass but sewing it twice like that will tend to increase your shrinkage. Not to mention the esthetic issue of spacing. Do you have any pullers? That would also cut down on your shrinkage. It would make your sewing more consistent. And it frees up your hands to focas on the fabric in front of the machine. You'll sew better and much faster.
What about your loaded bottom seam? Are you doing it like a PD seam. I honestly don't know exactly how they do it in shop but I would set up a double up turn and single down turn folder. And what about all the little prep steps. Got to have a tape foot with a puller. If your doing that by hand you'll go insane. Use a tape foot once and you'll never, ever go back. How about a upturn on the bottom plate for all the edge tapes you're going to do. Just run it through along with your tape foot and puller and you'll have all your prep done in less then 1/4 of the time it would take you by hand. Tail, how you building it? A full roll for the tail could make that a whole lot easier to sew. And a bar tack goes with out saying. Automatic machines are a god send.
I think when you have automatic bar tackers and a machine for every task you stop being a home builder and start becoming a factory. About the loft I'm planning to use, there aren't any puller or folders but there are double needles which is a step up from what I'm used to. This also means I can go with neater seams as well. I'm thinking something like Nick's construction method should work well. And yes, I am going to modify my design slightly so that the rib lines up a bit better with the bottom skin.
Yah!! factory. Now that's what I'm talking about. And actually all the things I just listed to that guy could be done on one double needle sewing machine. Then go and barrow time on some bodies bar tack to finish up. But once you use a bar tack it will be your next perches.
Not really related, but my old container may have been attacked with a stitch ripper. Maybe it's losing weight and turning into a ground launching harness, maybe it's turning into a future rigging project, who knows.
Yeah, I've stabbed myself once already. If anybody wants to know, I managed to separate out the harness, backpad, main and reserve containers without destroying anything. I now have lighter ground launching harness I suppose.
Good news is that I managed to source some slider tape, so I made my new slider. Bad news is that the thread tension is really fd up and I may just take it apart and try again on a proper machine.
Also got some 800 lb Dacron for the brake lines, so I had a little practice and measured shrinkage for the first time.
It's hard to see the stitching on the slider. It may not be pretty but I'm sure it's fine. Worst case, you might break the thread on one side when it tries to stretch. Remember you may wind up changing the size any way. Odds are this wont be the final slider that you wind up with. So just go jump it and see where you are at before you rebuild it. On a separate note it looks like the tape is a little short. Like it doesn't go all the way to edge where it over laps at the corner. Personally I leave it long and fold it under a good ways at the end so that the grommet is going through at least 4 layers of that tape. Furthermore you'll often see a peace of type four webbing included at the corner. It's really just to give the grommet some thing good and solid to bight into. Then sew all that shit together to give you a good solid corner for the grommet. There's a decent bit of load there but the main thing is the grommet needs something that it can really grab to transfer that load into. It's not that the tape isn't strong enough you just need to transfer the load into it. And yes I have seen those corners tear out but it was like a brutally hard line dump. Or at least that's my theory. It could have been a brutal opening caused by the failure but I favor the former.
Lines look good. 800 is a bit heavy for most of the suspension lines but if it was cheep then go with what you got.
The stitching on the slider is really shit in some places. As in the thread loops under the material. Upper thread tension too low? I think my tensioner's broken, lol. I know sliders are relatively easy to modify/cut holes in/replace entirely etc so I won't lose sleep over it. To clarify, the tape does go all the way to edge and folds over but in some places there's fabric on top so it looks like it's too short. I've had my inklings about extra reinforcement at the corners but I didn't know for sure. On the subject of grommets, are plain grommets and washers acceptable at all for sliders? The 800 lb line was relatively cheap at £0.70/metre and I've used it to make the lower steering lines. The main suspension and upper steering lines will be 600 lb Dacron.
You mentioned earlier something about seams not lining up correctly, where should they line up? As in where does the rib meet the panel? On the load bearing stitch row (what I've been doing), on the second stitch row etc?
Diagram may help or just confuse more.
(This post was edited by Quagmirian on Feb 20, 2014, 3:11 PM)
You really want a good roll rim spur tooth grommet. A good grommet will have a washer with two rows of aggressive teeth on both the inner and outer edge that lock into the fabric. It's not just a ring in the hole of fabric. You are not pulling on the out side of the hole. You are pulling on the inside of the hole. The grommet should be one with the fabric, locked in all the way around. What you're setting it in needs to be heavy enough to permit this and to transfer the load to the structure. So you need some sewing around it. Enough to insure that all of the layers that the grommet is set in then distribute that load outwards to the tape of the slider. I know that's kind of long winded but it can be important. I've seen a lot of grommets miss used because people don't seem to understand this.
The proper way for the seams to meet is how ever you choose to sew them together. If it was me I would split the difference on the load bearing stitch line. In other words I would center the panel tape in the middle of the wider diagonal tape on the rib. You're bar tack is going to be as wide as the panel tape. You might as well arrange it so that that is centered on the tape from the rib. And it gives you as much leeway as possible in case you're sewing is... imperfect. Wait until you get a slave working for you. You'll need a little leeway in your construction.
Speaking of which, once you get a good sewing machine or two you need to start thinking about where you can acquire slaves. I don't know much about the cultural issues in England. Manufacturers here have gone in a number of ways. Asians are always a good bet. But they have to be old school, preferable immigrants. If they are too... integrated? into the country then they aren't really Asians any more. If they are fluid in you're English then you probable don't want them. You need some one fresher. Another possibility is LOL's. It stands for Little Old Ladies. Oddly enough they are some of the best sewers and workers. They do have their own issues. Bathroom facilities can be an issue. Let's just say they have different standards. In any case I recommend that you look around for groups or individuals that you can exploit. The real key that you should be looking for is desperation. Older is always better then younger. Single mothers with limited job prospects are usually a good bet. You may not be there yet. And you never ever hire some one until you absolutely have to. And only if they will make you money. But you should start to keep your eye out.
And the thread thing. Make sure you haven't just popped out of your tension plate. If it keeps popping out check how you are running the thread through the guides before the plate. It needs a bit of tension there to keep it from popping out of the plate. May be loop around then through the hole rather then going in a zigzag through the three holes as an example.
I noticed on your older towing pictures you looked like the brakes were out of your hands? I find that a very bad approach. Think directional control to counter lock out situations . Also imagine the towing line breaks the canopy might shoot forward. Looks like too much tension that low. You can of course use the rear risers to get some degree of control. Also the towing car line could be a lot longer and most importantly a tension gauge should be on board. Idk if you plan to do any towing anymore but I would recommend you check out some towing manuals of the pg community and get some help. You can do towing much much safer and stress free that way imho.
Also you seem to do some ground launching off that hill. It looks like a demanding place to launch . I would recommend you use a pg harness with a back protector. If you fall out of the sky nothing is good enough but they do work most of the time. That can save you tons of grief and issues from bad starts or crappy landings one is most likely to encounter.
You could get a lower hanging point to the carabiners and get a whole new feel for the wing and tons more weight shift. (there is stuff online about old carabiners breaking after heavy use or misuse. I would get new carabiners , they are relatively affordable) . Or just wear your skydiving harness underneath
I do understand pg is not something you would be primarily interested about and the wings are not parachutes. But stuff like this is very much part of it. A good place to learn tons about flying , wings, lines and the sky . Would recommend that sport
... I seem to recall that the Strong Set 400's did not have cross ports. Maybe some one can confirm that? ... It might have been an attempt to control the openings by slowing the inflation of the canopies by reducing the filling through the cross ports. I don't know that's just a guess. ... For example the I've seen the SET roll tips under and it's not really prone to popping out on it's own with out help. ...
Correct! Strong builds their SET 400 and SET 366 tandem mains without cross ports. SETs open fine without cross-ports. They open slowly, sequentially (center cell first and end cells later) and comfortably without cross-ports.
Most of the problems with tips folding-under only occur after suspension lines are allowed to shrink beyond factory trim. Those Spectra (polyethelene) suspension lines shrink out of trim in as few as 400 jumps. When the outboard A lines have shrink 3 inches more than the center A lines, the end cells take forever to inflate ... often only opening after the TI has pulled the steering toggles to hip level for 8 seconds.
In the worst case scenario - when outboard A lines are allowed to shrink 5 inches more than center A lines - a fist-full of end cell fabric gets trapped in a front slider grommet. The slider tries to drag the end cell down the suspension lines. Sometimes, the slide releases the end cell when it is halfway down the lines, but sometimes the TI has to pump the brakes to release the slider. In a worst-case deployment the slider refuses to release the slider ...
Bottom line, you can your rigger now (to replace tired lines) or you can pay him/her later (to repack the reserve with a new free-bag, handles, etc, then reline the canopy with a new drogue, risers, etc.) ....
Just to clarify. The A line attachments were built with the tape spread out and sewn like a wedge to distribute the load. It acted like a tapered wedge and if pulled through the grommet of the slider would lock in place. So the malls occurred when the outer A shrank more then the outer B. The lines were long enough and the cascade low enough that you could actually get differential shrinkage between the outer A line and the outer B that had the slider stop on it. If the stabilizer had ben deeper or if the A line had had a slider stop on it to prevent it from pulling through the grommet we would have had a lot less malls. The shade tree rigger solution for those working at drop zones too fucking cheap to pay for the line sets to reline their canopies was to take a old RW2 ring and whip stitch it to the out side A line. In a since It became the new slider stop now that the A line had shrunk below the B line slider stop. This falls under the heading of techniques generally referred to as "nigger rigging". Note, this is not a racial epithet but a slightly derogatory term for a field expedient repair. Although it should not be a replacement for proper maintenance it will eliminate that particular failure mode.
I prefer the term "African Engineering." Hah! Hah!
Seriously, sewing an extra slider stop - onto the outboard A line - is a temporary solution. The long-term solution is to replace the entire line kit when the difference across the A lines exceeds the factory spec (3 inches). My old boss used to grumble about all the time and money I wasted re-lining SET-400s when the (Spectra) lines still looked structurally sound. My fascist rigging standards kept the malfunction rate down to 1/1500.
After I quit, my old boss allowed lines to remain in service despite being 5 inches out of trim, then he wondered why certain rigs went un-jumped all summer?????
I got my grommets set in my slider but they're not spurred and not size 8 like I asked for. Ho hum. But apparently "they won't fall out", so that's alright. Luckily they weren't expensive either. I think I may just take them out and get a rigger to put some proper ones in.
I still have a few more thoughts about seams at the leading edge. When I sew the topskin down onto the non loaded rib, the leading edge of the rib wants to sit perpendicular to the rest of the rib, right? This means that when I join it to the bottom skin, the leading edge of the rib is sort of twisted. Is this a problem.
Also the extra reinforcement at the leading edge. I'm worried that a bartack may not be enough, especially with how I'm lining up the pieces. How about a Para flite style tab which wraps around the entire seam and then is sewn with a dense stitch pattern?
I know what you mean by a little wrap around tab. All I can say is that we've gotten along happily with out them for the last twenty years. Don't buy you're self headaches you don't have to have. Build it. Jump it. If it breaks look for the EASIEST way to fix it. Do not design some thing that is any more difficult to build then necessary. Don't worry your little head about problems that don't exist. Has it blown up yet? Then you don't need tabs.
Not much to update on but I did go to my local DZ yesterday and got the chance to look at the details on a few PD canopies. I might go back with a tape measure and a camera. And can anybody tell me whether smooth clean concrete is a suitable cutting surface for canopy fabric? Since I have nothing better to do, I got a sample of zero p fabric from the local mill and it's interesting stuff. Definitely coated fabric (nice and crackly sounding) but it's not slippery at all. I'll see if I have get some specs.
It's probable a spinnaker cloth. Para gliders and some of the old para flight canopies used fabric like that. It's very stable dimensionally but the tear strength isn't as good and it's a little touchier in terms of how you sew it. It has more of a tendency to perforate.