Cosim Boy 2, the ONLY Sifow approved flight computer on the market!
Sifow School
New for the summer, learn at the School of hard landings and pick up the facts you really need to know.....MacCready? Pah! Scroll down the page, or select one of the following book marks:
Carbon Fibre, Wing Tips, Winch Launching
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History of gliding (abbreviated): In the beginning was wood, made from trees. Then someone in the sixties said "Hey man, glass fibre, wow, made from glass and fibre and stuff..", so they stopped using trees to make gliders and used glass fibre instead. Sometime after this, someone else discovered a much more expensive form of glass fibre made of Carbon. This became know as 'Carbon Fibre', though there is no recorded history as to how the name came about. Now everything that is good is made from CF and everything else is pants.
Carbon Fibre has a number of major benefits in the modern gliding world;
They make Formula 1 racing cars and expensive motorbike accessories out of it, so it must be good.
CF is stronger and lighter than glass fibre or wood, which means you need less of it per wing, which means you can have much more space to put water ballast in. Water is neither light nor strong, so why bother? In competitions, pilots never take off in CF gliders without adding loads of extra watery weight, and then, when conditions get weak, they dump it and get out-climbed by the wooden ships.....so just what is the benefit of CF then?
Despite needing less of the stuff, it is so expensive that gliders with CF spars cost much more money. This is good news as it keeps poor people in their place. Because water is nearly free, adding water to a CF glider reduces the cost per pound of all-up weight dramatically, yet still does not make CF gliders any cheaper.
Paradoxically, pound for pound CF weighs exactly the same as both glass fibre and wood, yet still costs more. Gliders made from CF, such as the DG500 series are still really heavy to rig even though they use CF extensively.
A 100k FAI triangle in the latest CF glider is still the same distance and shape as it is in any other glider.
Remember, contrary to popular belief, Carbon Fibre in NOT magic.
All gliders have wing tips. They can be found by following your wing from where it plugs into the fuselage until you run out of something to follow. That boundary between wing and no-wing is called the wing tip. If you add more wing onto where previously you ran out of wing (ideally to both wings in equal amounts), you end up with more wing than you had before, and unless your design is particularly poor, more 'performance'. The trouble is that if you had a 15 metre standard class glider and just added more wing, some jobsworth would point out that your glider was no longer 15m and disqualify you from the competition you were in. Then some bright spark worked out that if rather than adding wing 'out' you added it 'up', you would still only have 15m of horizontal wing, so that would be alright then. No one seemed to argue with this logic and so the 'tipped' glider was born.
Two questions spring to mind at this point;
What is the benefit of adding a upward sticking lump of glass fibre that clearly adds more drag than no upward sticking lump?
Why not have say a really long upward tip, say 25 metres on each tip, and then fly at 90 degrees to the horizontal, in effect creating an ASH 25 bi-plane that qualifies as a standard glass glider??
The answer to the 'benefit' question is that in theory at least, having a boring wing/no-wing boundary causes an inefficient airflow (the air is happily flowing over the smooth white surface of the wing, then slips off the end and tumbles around madly in an unorganised manner shouting 'aaarrrggghhh') which in turn creates drag. Drag is bad, we don't like drag, oh no. The upward lump of glassfibre creates a sort of playground for air particles, where they all queue up neatly and slide off the end in an organised manner going 'wwwweeeeeeeeeeeeee' instead. This creates either less drag (better performance) or at least more predictable air particles (better low speed handling). Manufactures claim performance, pilots claim handling and cynics claim cost. Still they do look nice.
The question of when is a 'tip' actually more 'span' is an interesting one. As you know, wings bend up in flight, so a 15m span (horizontal distance between the two wing/no-wing boundaries) reduces under flight loads. The acid test of this is, can the glider, under no flight loads and in normal configuration, be pushed through two poles exactly 15m apart (for a check a 15m glider)? The fact that in flight the wings bend to give say 14.9m in effect, is tough luck. But what if you could create wing tip that worked the other way, that under flight loads the tip moved out, to either maintain the 15m horizontal span or even increase it? The ASW 28 has two 0.5 metre tips...that's a 16m glider if you could get the tips change their orientation...no wonder it is set to be the new standard in the, er, standard class.
Finally a detailed analysis of the actions you should take if you are thinking of retro-fitting tips onto a glider that has been flying perfectly well for 30 years without them. Don't. Save your money and spend it on a decent vario and some more launches instead!
Ahhh, the joy of winching! The ability to quickly and cheaply launch gliders to nearly 2000 feet without the need for expensive tug planes, no noise, no bills, wonderful. I would be the number one fan of winching if any of that last sentence were true, but of course, in the main, it is not. So where does theory break down and reality begin? The simple truth is that a winch launch is a wonderful thing, however the ratio between winch launching and winch launches is a poor one.
The ten thing that go wrong the 'winch launching is wonderful' theory:
The winch master; Organisational theory says you need someone in charge, and winching is no different. The role of the winch master (WM) is simply to brow beat as many people as possible into becoming a winch driver. Most WM's are engineers by trade (If you are looking for rational debate and logical argument, you are in the wrong site!) and most engineers know that the way to approach the problem of something that is stuck is to hit it harder than the first time, and so on until it becomes unstuck. This lack of 'people finesse' results over time in the mandatory "all pilots must learn to drive the winch before going solo" poster in the clubroom. Naturally the first time any such message goes up, it gets ignored (the same for runway repairs, mending the club house roof, helping getting the accounts straight), cue doing it again but harder. All pre-solo pilots will have a go at some point, but soon realise that sitting in a 4 foot square box at the wrong end of the runway when your mates are flying is just not fun, or flying, or anything really. So they either ignore the clubhouse poster (pause for larger poster to be put up) or leave to find a club that aerotows...or try a sport that involves flying such as paragliding or hang gliding.
The 'willing' driver; The lack of drivers, as discussed above, leads to the over use of the few 'willing' drivers there are, or worse the use of the 'you got passed out last year, we need you to do half an hour in the winch' conscript. This approach has the triple benefits of (1) freeing up the previous driver so he can moan with his friends about how tough getting relief drivers is and how little flying they get these days; (2) Of turning the perfectly 'happy with gliding' conscript into wishing he was at home with the kids and of course the ultimate benefit (3) the launch from hell. Note that the use of the word 'he' in this discussion is not sexist, it is simply that no woman in her right mind would be daft enough to get involved with winching in the first place.
The launch from hell; You've been there, instant acceleration to 75 knots followed by a slow decrease to 38 knots as the driver sees paint flaking from your wings. You pull off at 45 knots, 500 feet and land well down the runway. The driver reads this as not having given you enough speed to start with so the next launch gets the full 80 knot treatment. This launch gets to 1100 feet in eight seconds before the weak-link breaks spiraling a mile of piano wire all over the runway, the fence and the adjacent farmers field. In both cases the winch driver will blame the pilot if questioned.
The cable brake; Three major goodies arise from a cable brake. Firstly the glider, finding itself at the wrong angle and height has to pull (push?) -3G and use side-slip to land before groundlooping in the long grass at the end of the runway. Secondly no more than one glider can now land as the runway is taken up with the first glider, the coiled piano wire and the 13 helpers who have ignored these first two blockages and are heading to the winch to refine their 'you need to weld a piece in there to stop that happening again' skills. Finally of course, it will be a good hour and a half before there is any chance of another launch. And don't give me that "but if you use stranded cable" argument.....you still get over running cables and weaklinks breaking and cables in fields!
Cable brake practice; Not content with actual cablebreak delays, the principle of safe flight (which is pretty difficult to argue against) demands that every weekend you need to pull the bung on at least 3 unsuspecting pilots. This gives you most of the problems associated with point 4 above but without the 13 pilots moving from their seats, which is a shame because 'surprisingly' the sudden release has caused the cable to spill out and wind itself around the drum. Still only another two practices to go.
Changing ends; An event that delays launching for at least two hours. The first half hour is spent launching gliders to 700 feet because you have been trying to ignore the fact the runway you are on is now downwind. The next hour is spent moving the winch, relaying the cables, moving the cars, gliders, launch point vehicles, people and animals the full length of the runway and reassembling them at the far end. The last half an hour is then spent trying to find someone that now can be bothered to fly as all the good weather has gone and it will be dark in 30 minutes. Anyway the wind as switched back again.
The home built winch; Not content with all the problems above, someone at your club is right now looking at an advert for a really cheap bus and has a sketch on an old envelope as to what they will do with it. Had that person been allowed to fly a few years ago rather than being voted in as the winch master, he (not sexist again) would be installing a new GPS bracket or something useful instead. Home built winches cost a lot less than professionally built winches because they are pants. They will spend all their days being fettled (read mended) and multiply any problem above by at least a factor of two. People don't build their own lorries or trailers (d'oh - they do don't they) so what makes the idea of cutting a bus in half look feasible? Don't do it, please.
The lottery funded winch; Sounds great, raise some money, get some funding, new winch arrives. So as long as you have some spare money or can raise it, great. Once it arrives there will be winch training weekend where the few winch drivers you still have get whittled down further, as clearly the new winch cannot just be driven by anyone. For the first season launches will vary wildly between 'Apollo' and 'paper bag in breeze' as myths such as 'never go beyond the second notch' or 'the K21 needs full power in all wind speeds' abound. Then the committee will step in and say that the club needs to recoup some of the money is spent on the winch, so the launch fee is going up, which always has the sole effect of reducing the number of launches and hence income. The good news is that over time, the winch will start to look as tatty as the old one, drivers will revert back to the 'one power setting suits all' approach and the committee will be trying to get the club house roof mended instead....happy days again.
The 'good idea'; At anytime some member will have a 'good idea'. It will involve angles of cables or electronic gadgets or welding bits of extra metal on or any combination of the three. The purpose of this is to overcome the now universally accepted problem with the clubs winch, whatever that may be. If this idea ever gets implemented, and I use the word loosely, it will be ignored by at least 50% of the drivers who don't agree with it, mis-used by 25% who don't understand it and broken by the rest in their enthusiasm for it. Once broken no one will mend it as they are all being co-opted by the committee to the roof repairs. Everyone will still agree that the winch still has the same problem as before however.
Hamish; The good news, there is a way to make winching work, it is the only way and I refuse to believe in any other way. Get a full time winch driver. At Port Moak (club in Scotland) they had a full time driver called Hamish. Every launch was 100%, not too fast, not too slow. Everyone liked winching because they did not have to do it, Hamish liked winching because he got paid for it. Because he did it every day he knew when and how to launch all sorts of types of gliders, so safety was improved. The extra 10% (or whatever) the launch cost to pay for him was willingly paid because you got a launch rather than an experience. Hamish sadly passed away a few years ago, but his replacement does a fine job and the point is still valid. The ONLY way to make winching an enjoyable experience, IMHO, is to get a full time driver. Do it!
Gosh I feel better for that, nothing against good winch launches, just the messing around that comes with the package, a bit like my PC, really good when it is working!
Topics coming this way soon include weather forecasts, high performance cross country trainers, lift-top trailers and the history of final glide computers. E-mail me if you have any topics you want explained!