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Lo 100 build and fly information

Anything to do with gliders & gliding.
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RobbieB
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Re: Lo 100 build and fly information

Post by RobbieB »

Just to be clear here, I plotted the aerofoils in Compufoil for John's LO100 and the main section is a Quabeck - HQ3014 only transitioning to a Clark Y (modified) from the start of the eliptical section out to the tip. Just looked at the file again to be sure.

.............and 16 - 20oz/ft², is not a bad loading for an aerobatic scalie.
Martin Dee
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Re: Lo 100 build and fly information

Post by Martin Dee »

'.......HQ3014 only transitioning to a Clark Y (modified) from the start of the eliptical....'

Interesting Robbie...What was the thinking behind the thickened centre section? Structural considerations or some aerodynamic reason?

I am leaning to S3021 root to tip and setting it out in Dev-Wing shows it will be fairly slim, but I can just get a pair of 12 tapering to 9mm x 4mm spruce strips in for the main spar which should be sufficient with the webbing and sheeting etc. If necessary for aesthetics the first few ribs can always be thickened up.
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RobbieB
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Re: Lo 100 build and fly information

Post by RobbieB »

Martin Dee wrote: 09 Sep 2020, 09:46 '.......HQ3014 only transitioning to a Clark Y (modified) from the start of the eliptical....'

Interesting Robbie...What was the thinking behind the thickened centre section? Structural considerations or some aerodynamic reason?........
Well both to some degree.

I seem to remember (it was a while ago now) John wanted a more up to date section than the Clark Y that would be a compromise (isn't most flying machine considerations) between a reasonable aerobatic and soaring performance - although the LO 100 would be pretty far down the list as an efficient soarer.

The Quabeck HQ series has a great pedigree for use in large scale sailplanes and is now generally used full span without washout to great success - just thinned a little at the tip.

At the time I was still old school whereby in keeping with the common full size practice of increasing the camber of the tip section but washing it out by the difference in the zero lift angle of the two aerofoils. Doing it this way the tip stall is very effectively controlled and both root and tip reach their respective stall angles at the same time and there is no negative load on the tips at speed, Clark Y being a very good tip section for this.

The Quabeck used is only a little thicker than the Clark Y and the same camber but like most modern aerofoils has a higher entry point at the nose; and thickness is not the ultimate arbiter of maximum top speed, camber plays a much bigger part in that. It's also important to understand you have to compare like with like - it's not as simple as just comparing camber and thickness between different aerofoils. It makes a significant difference where the maximum value of both of those parameters lie on the aerofoil. Modern model sections tend to have them further back on the aerofoil than older ones.

I'm a fan of thick aerofoils (within reason), they are much more forgiving, have a wider speed range and also a wider low drag range.

Hope all of this hasn't confused you even more...............
Martin Dee
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Re: Lo 100 build and fly information

Post by Martin Dee »

That makes sense..

Have made a start on the easy bit as per pic below. when I get to a point where I have some bits to glue together, I will post a build log as there doesn't seem to be one for Lo100.

I don't have a building jig, so will use the crutch method of construction with formers split vertically. The main challenge for me is to find my Mach3 license code, I hope they have kept a record of my license purchase made a few years ago now!
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Peter Balcombe
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Re: Lo 100 build and fly information

Post by Peter Balcombe »

Martin & Robbie,
I am currently looking at updating the original Charlesworth wing plan design for Cliff & have come across this oldish thread.
My initial look at the original Charlesworth plan shows a fairly flat bottomed wing section throughout the wing & with little or no apparent washout. (The inverted wing build seems to be intended to result in a flat upper wing surface with no twist).
I had thought of using an HQ section & would be interested to hear whether the HQ/modified Clark Y choice as Robbie mentioned is a good one.
Also of interest was the ‘hard’ wing mounting & retention methods, which seem to be either intended to fail in the event of an ‘arrival’ (protecting the wing) or is likely to result in significant damage if not.

Martin, did you ever build the LO100 & if so then what sections did you use & how did she fly?

Peter
Martin Dee
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Re: Lo 100 build and fly information

Post by Martin Dee »

Peter,
Never did progress the Lo100 in the end. Prevaricated due to its barge like girth and general lack of aerodynamic pretensions, then hit by the balsa drought, then the doubling of balsa prices made it prohibitively expensive to build. Had to content myself with a Teakle Dart, now grinding to its conclusion 6 months behind schedule. Even the balsa for that was an eyewatering cost, I mean £2.50 for a sheet of 16th! - how do these people sleep at night. Not convinced it is going to be a good flier either, except possibly as a high wind pylon racer.

Now only considering scale projects that are feasible using only light ply, B&Q spruce (almost as light as balsa!), foam, brown paper and 50 gsm tent fabric!
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Cliff Evans
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Re: Lo 100 build and fly information

Post by Cliff Evans »

The Pat Teakle Dart is a very good model, and flies very well.

The Price of balsa is beyond the control of the suppliers her in the UK. China purchased most of the balsa stock available throughout the world to make wind turbine blades, which caused a worldwide shortage. Now we have the cost of living crisis on top!
https://lasercutsailplanes.co.uk
https://patteaklegliders.co.uk
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Peter Balcombe
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Re: Lo 100 build and fly information

Post by Peter Balcombe »

Martin,
If you built the built-up wing version (sounds as if you did from comments about balsa costs) plus use a built-up tail & rudder then it comes out pretty light & with the HQ section flies very well.
I built the prototype to prove the new built up plan & I think Brian Sharp also built one.
There should be a build thread for my build somewhere in the scale build threads section.

The wings (with 1/4x1/8” spruce spars) are fine for normal scale flying, but I think Brian found that the wings flexed a bit when flown a lot more enthusiastically.
Peter
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Cliff Evans
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Re: Lo 100 build and fly information

Post by Cliff Evans »

Brians build of the Dart can be found here: viewtopic.php?t=2664
https://lasercutsailplanes.co.uk
https://patteaklegliders.co.uk
Martin Dee
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Re: Lo 100 build and fly information

Post by Martin Dee »

Ta,
I'm sure the Dart will be great, just mid-build defeatism!

It seems I am afflicted by a sort of inverse Midas touch when building flying models - they gradually seem to have turned to lead by the end of the build process. I try, really really try not to let it happen, but somehow it just does!

Opting to fully sheet the wing added to the general weight gain, but given more likely than not it will be landed in a gorse bush, on sharply gnashing rocks, on the horns of a cow etc, a robust solution was called for, for which I will pay a price (probably in the form of a non scale wing eventually).

While thinking about the sheeting problem and how difficult it is to find a good substitute for balsa, I experimented with a craft paper/20 gsm glass cloth PVA bonded sandwich. Not completely successful. Doesn't have the anisotropic stiffness of balsa, but is quite strong. Might be ok for non critical areas of fuselage skinning. The material resists tearing in one direction very well but is weak 90 degrees to the strong axis. Perhaps with 2 layers of glass cloth biased and squeezed together at very high pressure it might be better and a possible substitute for 64th ply, but would be twice the weight of balsa. It is also a pita to make!
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