Lo 100 build and fly information

[Martin Dee]

With winter a'commin-in, I am considering having a go at a 25% Lo 100 build, probably using the the plan available on this site as a
guide.

I am hoping it will be fully aerobatic model, but still flyable/thermalable on lighter airs (say from 8-10 Kts). I was wondering if anyone that has a Lo100 could comment on its general flyability, AU flying weight or wing loading, nasty habits etc, I would be grateful.

My main fear is to end up with a too heavily loaded aircraft that will only fly in 40 Knt winds. Would prefer to build light and use a ballast tube in the wing for lively days if needed.

Also looking at the site plan, it appears to indicate zero incidence on the wing, whereas on most of the three views available on the web, the incidence looks to be anywhere from 3 to 5 degrees. I would have thought about 2 to 3 degrees would be OK (for Clark Y, maybe different for SD6060).

Probably prefer to use a Clark Y wing although SD6060 looks appealing for cleaner manoeuvers and inverted, however I think the reduced cL compared to Clark may restrict the model to high wind days.

Thinking that a 15mm round CF wing joiner on the spar, or 10mm + 6mm (front and rear spar) would be sufficient to handle plenty of G.

All advice and hints etc, gratefully received.

[RobbieB]

Martin, there is an SSUK member who has done a LO100 (and the extended 150) so I'll bring your post to his attention.

One thing, if you really want it to have a good aerobatic performance Clark Y is not really a good choice to say the least.

[Peter Balcombe]

Martin,
I maybe wrong here, but I think you may be confusing wing incidence with decalage (the latter being angle between wing & tailplane).
The wing angle to fuselage longitudinal datum defines the ‘sit’ of the fuselage when the wing is at its normal flying angle of attack, usually set to minimise fuselage drag.
The angle between wing & tailplane gets efficient flight & is often in the range 2-3 degrees ‘ish’.
If this is all rubbish then others will soon chip in

[Martin Dee]

Thanks to all,
Peter, I was actually thinking of the sit of the wing to the imaginary datum through the mid point of the fus - in most of the 3 views and pics I have seen, there appears to be a marked wing angle to this datum, but I could be wrong. The horizontal stab always appears as parallel to such an imaginary datum, which would be logical, as this would be close to a suitable flight decalage, as you say.

Very difficult to tell from the selection of grainy pictures and 3 views from the web, so was hoping someone would know.

Robbie, If I thought I could build it to an AUW of 6 lbs or so I would use SD6040, recognising that Clark is far from ideal for slope and aerobatics (although we are not talking about competition here!).

I don't need to fly inverted all the time, so there may be a compromise using Ritz-3 or S3021, which both have a much flatter and more stable moment coefficient/AoA and are better suited to slope flying than Clark. I use a 2.0m non scale with S3021 and that has an acceptable aerobatic performance for my purposes (and a very flat glide), but the loading is only 12oz/ft - my fear is a scale 100 built by me may end up at twice that.

As you say, building 2 wings may be a solution, but I think I can only manage 1 per winter!

[SP250]

Martin

I have a 1/4 scale Lo100 from the Charlesworth plan, it has the Clarke Y aerofoil as far as I can tell and it is lousy at inverted flying without 90% of the down elevator in and a fus angle of about 20% nose up (inverted nose up). However if you use the flaps when inverted to a fixed position reflexed (ie. down now its inverted) it does fly better, but loses altitude at a rapid rate so it is very draggy. You do need a good blow for the flying to be any good and that means it stays on the ground in less than 10 mph. It's very nice having said all that and will loop and roll with the best of them, but mine is fairly light (you will need lots of noseweight so I use double 5 cell NiMh 3700mAh batteries and it will only thermal in strong ones, it is not a light day type of model even with the 150 wings John Slater built, they have the same wing area as the chord is narrower and his is not as efficient as something like a skylark or minimoa if my memory serves etc.

Its a nice model to have in the hangar, but only comes out on suitable days. Don't let that put you off as I really like mine.

John M

[Martin Dee]

John,
Thanks for that - useful info. 'Tis as I feared - the inevitable high-ish wing load means performance in light to moderate conditions is expecting too much, when added to that bulbous, porky, uber draggy fuselage. I imagine they come out at 8 to 9 lbs.

If Clarke cant provide enough power in modest conditions, then there is not much else available. I will then focus on the aerobatic qualities, use an aerobatic profile and be resigned to flying in grim conditions.

I wonder if you could confirm if the wing is set at an angle or is level to a datum defined by the main horizontal stringer on the Charlesworth model? Only asking because the free plan shows the wing and Horizontal stab as both horizontal, which surely cant be right.

In any case, I expect that if I do use SD6060 it will need to be set at a min of 3 degrees, otherwise in level flying trim the fus is likely to be nose up and look rather odd.

[Peter Balcombe]

Martin,
If its any consolation, the Lo100 3 view in Sailplanes 1945-1965 by Martin Simons, shows the tailplane set at, or very close to, 0 degrees with reference to the fuselage longitudinal datum line, whilst the wing is set at a small positive angle to this datum.
This will give the expected +ve angle between wing & tailplane (decalage), whilst probably causing the fuselage to be at a small nose down angle in flight.
Peter

[SP250]

Martin

Just to satisfy my own curiosity, I weighed my Lo100 and the auw is 4.372kg or 9.635lbs. Most of that is in the fuselage and as noseweight, so I will be impressed if someone can build one very much lighter (I did not build this one - picked it up S/H ).
The flat bottom of the wing is at zero* and parallel to the fuselage datum (by eyeball) so the Clarke Y incidence through the LE radius will be about 3* and the tailplane seat looks to be at zreo as well. Decalage about 3* therefore.
HTH.

John M

[john slater]

Morning Martin,
As people have said, I built the Cliff Charlsworth LO100, which is a bit heavy, because thats the way I build but it will do every manoeuvre I can manage, it does have the section Robbie mentions.
Because I wanted a more sedate model I then decided to build wings to match the same fuselage for the LO150 version, and it is more of a floater, it has the same wing area as the 100 but obviously 50% more span.
I will be honest I have not flown either very much, because I do have a few other models and plus with this KOVID thing I have not been out a lot.
Lots to contemplate for you and the best of luck, its a nice size model and very enjoyable.
John

[Martin Dee]

Thanks to all and John M, in my excitement completely forgot that it is the chord line that defines the AoA, Doh!

But 4.4Kg AUW Eeek! that is 20oz ft2. Beginning to wonder if this is a good idea after all!

Still, the 100 version is a relatively small / simple model so there might be some chance of completing it in 6 months.

Clearly there is beneficial reduction of drag on a wing with the same area but higher aspect ratio. However, I think if I was ever tempted to build the 150 wing, I might take a 'judgement' as to what constituted a 'scale' cord in order to deliver a satisfactory flying experience!