How many here fly gliders too?

[Guest Nobody]

I have spend some time looking at a design for a self launch from two seat single and options. I have now decided on a single seat 18-22m 4 piece wing all glass and with no moulds, one cannot get away from carbon for spars with such high bending moments with a 80mm thick wing. a self launch 28hp motor L/D 45+ . Still refining things, its not like designing a power aircraft and will probably take another 12 months. cost of the build under 20k.

80mm thick wing seems awufully skinny... How was that arrived at?

 

 

[Garry Morgan]

Look at any modern glider 75mm for a Ventus C, a 2 seat Duo is 150mm wing, thickness are 8-10% at the root and 12% approx at the tip that is bacause they dont use washout fort the last 20 years.

 

 

[facthunter]

I guess you have to be very flexible in your approach to these things. Nev

 

 

[Guest Nobody]

Look at any modern glider 75mm for a Ventus C, a 2 seat Duo is 150mm wing, thickness are 8-10% at the root and 12% approx at the tip that is bacause they dont use washout fort the last 20 years.

I don't have the ventus C data here but this references indicates that the Ventus B is over 100mm at the root at 14% thickness.

 

http://web.archive.org/web/20050206183811/http://www.ssa.org/Johnson/38-1981-12.pdf

 

And the Ventus 2 is about the same

 

http://web.archive.org/web/20050206183811/http://www.ssa.org/Johnson/79-1996-04.pdf

 

Even the JS-1 known for having a thin wing has a 12.7% thick airfoil which would put it about 100mm thick.

 

http://www.jonkersailplanes.co.za/aerofoildesign.htm

 

80mm sounds a little too good to be true.

 

 

[Garry Morgan]

Yes 12.7% thick is the maxium ,and it is at the tip, the root is 3-4% - a 800 mm cord will be 72mm and the centre of the moment for the spar cape will about 63mm a 900mm cord will 91mm thick .Airfoil data will give a MAXIUM thickness which is not what the aircraft will be, and it changes along the wing. it is not the same from root to tip now days, it was 20 years ago but some have discovered how to improved handling with out losing performance.

 

 

[Guest Nobody]

Yes 12.7% thick is the maxium ,and it is at the tip, the root is 3-4% - a 800 mm cord will be 72mm and the centre of the moment for the spar cape will about 63mm a 900mm cord will 91mm thick .Airfoil data will give a MAXIUM thickness which is not what the aircraft will be, and it changes along the wing. it is not the same from root to tip now days, it was 20 years ago but some have discovered how to improved handling with out losing performance.

I don't want to be seen as being negative and I hope you prove me wrong but I think many of your numbers are too good to be true.

 

I have just done some very rough spar bending moment numbers and to get 81mm to work(9% of 900mm chord) I need a spar cap 114mm wide by 10mm thick if using UD carbon fibre. I don't think that this is plausiable.

 

I am sure that most modern gliders have spar depth of 100mm or a little over. Go and measure a few.

 

http://www.jonkersailplanes.co.za/structure.htm

 

 

[Garry Morgan]

Well to work out a bending moment you need to know a weight and span and a G loading. I think you have taken the total aircraft weight ( not the carrying load) as your spar caps are much to big. I have measured some spars ,but it isnt hard to work out a thickness. Your cal. need some looking into they are not correct,or your experience.

 

 

[Guest Nobody]

I have used a few guesses but here are my calculations. Sorry for the formatting. I wrote them out by hand and havent worked out how to upload a scanned pdf.

 

Loading

 

Engine +Prop 30kg

 

Fuselage Structure 120kg(including the tailplane)

 

Pilot 100kg

 

Total 250kg

 

design G factor 6g

 

Load supported by 1 wing= 250*9.81*6/2=7360N

 

=7.36 kN

 

Assuming 18m span and uniform lift out to 6m from the centre line then diminishing to zero load at the at the tip, this gives a Moment at the centre line of:

 

M= 6*0.981*6/2+(6+3/3)*1/2*3*.981=27.96kNm

 

(This above is a guess but is reasonable as it puts the centre of 1 wings lift about 3.8m from the centreline)

 

In an 81mm deep spar the centres of the caps will be 71mm apart if the caps are 10mm thick.

 

Therefore the cap force is:

 

27.96/0.071=394kN

 

Assuming UD carbon with Compressive strength of 600MPa and using 1.75 as the design material factor then:

 

Area of spar cap= 394*1000/(600/1.75)=1148mm2

 

Therefore spar cap of 114 by 10….

 

 

[Garry Morgan]

You have just showed that you have no idea how to cal a bending moment there is lot more to it.

 

 

[Soleair]

Back to the OP. . .

 

I started flying hangliders in 1975. Went on to microlights in 1979. I got my PPL in 1984 (flew mostly in an ARV Super2), then took up paragliding briefly. I got to solo standard in an AS K13 a few years ago - stayed up 1hr 20mins on my 2nd solo and only landed because it was getting dark

 

Gliding certainly taught me how to use a stick and rudder, and was excellent for honing landing skills (no go-around option!). I really enjoyed it, despite the ratio of hanging around/assisting to actual flying. Highly recommended to any jaded powered pilot, or indeed anyone looking to broaden their aeronautical skills & experience.

 

Bruce

 

 

[robinsm]

Fun to ridge soar in the Xair, motor to idle and back and forward for height gain, cool fun on a good day...thanks gliding time.

 

 

[Garry Morgan]

I was at a club meeting last month and looking around the people at the club, in 10 years time 90% of them will be in nursing homes. What we will be left with is to small a club with not enough flying to pay for the tug and maintenance, peoples time cannot spend all day at the airfield, and only get 2 landings in. It is the same in most of the world..people want more for there time.

 

The future gliding club may only have one aircraft one instructor ( no tugs) but a motor glider for training. Ring up and make a booking, turn up and you can do 8-10 landings or you 1 hour flying and go home. Just like power aircraft, when you mention this to a gliding person they laugh, but the hard facts are if gliding doesn't change it wont esist soon.

 

One gliding club in Syd. has already was going broke because of the tug cost, another club brought a motor glider and very soon the club sold its tug ,and got a motor glider, and now makes more money than any club in Australia. Like our GA clubs that don't adopt RAA aircraft, most are not doing very well ,but those that do had been going ahead at a great rate of knots. Its a time of change in the world, and we have to change with it .

 

 

[Dafydd Llewellyn]

I can only agree with you. And do you know how this could be achieved? By sensible application of the RPL. We HAVE to get rid of the "separate turf" situation that divides recreational aviation up into uneconomic specialised sectors. Think about it.

 

 

[Bruce Tuncks]

I sure would like RAAus and GFA to amalgamate. it would save me having to be in 2 organisations.

 

Here's how I got into RAAus: I was going to take over a Ventus 2 order, but it was going to cost over $150,000. This would have incurred 26% sales tax at the time. ($39,000) Well the Jabiru plus a hanger ( both in kit form) totalled the same as the SALES TAX on the Ventus. ( $35,000 for the Jabiru kit plus $4,000 for the hangar kit)

 

So now I have the Jabiru plus a Libelle. The Libelle was $3000 as an insurance write-off. It cost about $5000 to fix.

 

I would like to put a small jet engine on the Libelle to help avoid the danger of outlandings, but our so-called safety authority will make this very hard to do legally, with thousands of dollars needed to satisfy bureaucratic obstacles.

 

...Bruce

 

 

[Dafydd Llewellyn]

Well, unfortunately RAA and GFA are chalk and cheese; the difference between them are fundamental. About the only way to get rid of the boundaries between the various recreational aviation activities is to put them on a common basis. The "CASR Part 103" proposal sought to do that - but when one examined it closely, it was in fact a straight-jacket that appeared acceptable at that time, because it was two sizes larger than what was then needed. It had no elasticity built into it. The FAA approach is to pull all these activities (apart from the American equivalent of CAO 95.10) into FAR Part 91. I don't know whether that is an improvement over what we have now; but it essentially gets rid of all the separate controlling bodies. I believe the question needs study, because I don't think it can continue much longer the way it currently is. The RPL should be a major part of moving towards a more rationalised system - if it were used correctly.

 

 

[WayneL]

Did my gliding in the early eighties. Loved flying them...but the down side for me was the long waits for club aircraft, needing a team to get you flying (tow pilot & ground crew Etc). Had a chance to buy a half share in a open class glider or spend less on an ultralight. I chose the ultralight because I could take it out any time I wanted without the ground support team!

 

 

[Old Koreelah]

Did my gliding in the early eighties. Loved flying them...but the down side for me was the long waits for club aircraft, needing a team to get you flying (tow pilot & ground crew Etc). Had a chance to buy a half share in a open class glider or spend less on an ultralight. I chose the ultralight because I could take it out any time I wanted without the ground support team!

Similar story Wayne. In the 70s gliding was the flying I could afford, but I had similar frustrations with long days, no fly.

AUF gave me, and lots like me, a unique opportunity to get into the air.

 

Strangely, powered rec. aircraft seem to be cheaper to buy than decent sailplanes.

 

A self-launched sailplane is still my ideal.

 

 

[Dafydd Llewellyn]

It's taken GFA a long time to come around to it, but it does have an "Independent Motor-Glider Operator" rating nowadays.

 

 

[WayneL]

A self-launched sailplane is still my ideal.

I think electric powered self launch sailplane may have a big future due to the fact the motor runs will be short.....enough to climb to chosen height.

 

 

[Soleair]

Yes, could be an excellent way into aviation for electric power. I'd definitely be right at the front of the queue for an electric self launch glider. Especially one with clever folding wings and one of those trailer-cum-hangars.

 

That'd be me sorted.

 

Bruce

 

 

[nomadpete]

Gliding - I hadn't had a gliding fix for aver three months. So I went out to Jondaryan last Friday. Friday flying is good because there is no waiting list to get a glider. It was a nice warm day with a little breeze to get the thermals to kick off. After a check flight I was set free. At first it was a bit scratchy but the thermals were working pretty well once I got some initial height. Then it was a lovely couple of hours chasing the good air. Didn't go far - didn't need to. had Airspace clearance to 8500 so kept a safe margin below that. Nice and cool up there, so I doodled out to Dalby and back. Gliding is a great adjunct to noisy little aeroplanes. There should be more people doing multiple disciplines as it helps one to learn so much more about the habits of the air we all fly in.

 

 

[Bruce Tuncks]

Good post nomadpete, and I like your motto too. I just had a great flight in the Libelle, went 80k to try and work some wave clouds east of Eudunda, but only got to 9,300ft while the wave clouds were much higher. I tried every trick i know but nothing worked. Still it was a good flight.

 

I reckon you are right and that power pilots should fly in a glider and vice-versa.

 

 

[cooperplace]

decades ago I visited a well known gliding club with a view to taking it up, and I was really put off by the attitude of the people there. They said that I would have to hang around all day, possibly helping with menial tasks, and if I was lucky and a good boy I might get a short flight at the end of the day. And that if I persevered with that, I'd eventually get in more flight time.

 

I didn't take them up on the offer.

 

Now that I'm into jabirus, I can make a booking at 11am and I know just when I'll fly. I've been up in gliders and I love it, but gliding back then certainly needed to change. I don't know if it's still like that. Motor gliders might be the answer.

 

 

[facthunter]

Motor gliders might be the answer. Well certainly weight doesn't seem to be a problem. It gives a higher sink rate for a higher cruise speed. You might as well carry a tucked away motor as water ballast. Nev

 

 

[Bruce Tuncks]

No its not like that now Cooper. There is a shortage of students these days. But its rude to not help to get the gliders out at the start or put them away at the end of the day. You dont have to do both.

 

You can ring and book a glider flight at Gawler these days, come and visit.