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Hi-Performance and Sailplanes RC hotliners, electric pylon racers, F5B, F5D, sailplanes and gliders

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Old 07-26-2009, 02:31 PM   #1
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Default Apex Models Wiffler glider

Many years ago ,I think probably near 20 I built a balsa model glider kit made by Apex Models in Scotland UK.It was never flown and stored away .I have recently recovered it from its storage place and got it ready for its first flight.I have one problem and that concerns the ballance position .I have made marks under the wings when I built it but these are around 40% of the chord.Nearly all my other planes are ballanced about 25-35% so it got me a bit baffled as to why I would put the ballance point so far back.I cannot find the original plan so as to check it so this is why I am making this posting to see if any of your members have built a wiffler or maybe have an old plan they could scan and let me have.I don,t know if this model made it across the pond or any other place outside the UK but I thought I would ask.


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Old 07-26-2009, 07:39 PM   #2
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Hi John, Welcome.
Don't know the wiffler, but that could have been the balance if the tail was expected to be built slightly heavy with no ability to move the wing fore or aft. First flight set-up for gliders is covered in the stickies at the start of the sail plane section. Thoughts, into a nice soft grassed area, once you have the balance where you think it should be, give it a gentle hand launch and see what it does. If it dives down into the ground move the CG aft. If it porpoises move the CG aft. If totally unpredictable move the CG forward.
Once you have the CG nearly right you should have a steady gentle decent. Then you can set up your trim on your rudder and elevator.
Then you will be ready for a launch into the wild blue yonder with your chosen method of launch. (also covered in stickies)
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Old 07-26-2009, 09:16 PM   #3
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Default Glider C.G.

Hello John, Welcome to Wattflyer!
I agree with Terry, a 40% C.G. sounds like trouble. Unless the model has a very large lifting stabilizer and it's intended to fly as a Free Flight, that rearward a C.G. will make the model very twitchy on the elevator and difficult (or impossible) to fly.
I'd recommend doing as Terry suggested, try a few gentle hand tosses over tall grass. Bring along some modelling clay and be prepared to slap a lump on the nose if it shows signs of being tail-heavy at all.
When you've got it balanced and trimmed for a nice, shallow flat glide, mark the new C.G. and put an equivilent amount of ballast inside the nose to make it permanent. If you can do this by shifting the battery forward, all the better. Once the battery is all the way forward, you're stuck with adding extra weight, however.
The golden rule of trimming a model is;
A nose-heavy model may fly poorly
But a tail-heavy model only flys once!
Good Luck!
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Old 07-27-2009, 08:19 PM   #4
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Terry,Ron thanks for your advise.I will have to pop into the farmers field as the grass on the site I fly from is always kept short.Got a field full of rapeseed oil plants just behind the flying field.Hate the idea of adding weight but the 3 cell lipo is already right up in the nose so it looks like I will have to.

Thank you both

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