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When your glider won't glide...


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Third outing with my new own-design slope soarer (the Mediator), still experimenting with the c/g so expected some variation in behavior but I wasn't expecting this...


Got to my local slope. Wind's always a bit gusty on Dartmoor. 6-13 mph south westerly face-on to a big but not steep slope. Should be fine. First launch, up to about 40 feet quite quickly, 10 mins, landed, moved the battery further forward. Second launch, 40 feet again, handling better, 15 mins landed fine. Third launch, 10 feet then down down down. What's going on? Tried again - same again. Kept trying. What's going on? Has the wind dropped? No. Changed direction? No. Controls all working? Yes. Trims okay? Yes.

 

If there is such a thing as 'the magic of flight' it was like someone had turned it off. The model was the same, the wind was the same. I was completely baffled.

 

Tried again, and again and then, as she flew past me, loosing the tiny bit of height she had, I heard a very faint low pitched buzzing. Too early in the year for insects. To early in the day for a Nightjar. Then I twigged it.

 

Close inspection of the wing revealed the problem. From tip to tip all the way along the wing the covering had come unstuck on the leading edge. White Hobbyking over pink Solarfilm. Game over. Got home and ironed it down again. Seems to have stuck perfectly but can I trust it?

 

20210309_214259.thumb.jpg.9db34ae092c7cf63c5c97b13cc2132cc.jpg

 

Before you ask, the slope was well within my "local exercise area" and I was alone.

Edited by David Ramsden
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Hi David,

 

I use HK all the time and as others have said the iron has to be hotter, with a sock on my iron is almost at maximum. Once the film is shrunk I remove the sock and seal the edges/joins with it, the plastic almost melts and removes the ridge. I know when the iron is hot enough and has been moved slowly enough over the join because a white line of glue is left behind as the film shrinks slightly and I can feel the melted glue sticking to the iron. Too hot or too long the white line becomes wider.

 

I have a temperature controlled heat gun. For initial tack and shrink I set it at 100 C I then increase this in 10 C increments to remove the stubborn wrinkles above 130 C has little effect on shrinkage but does increase the stretchiness. 160 C is in the melting zone.

 

I also have a soldering workstation which I use for the final really stubborn wing tip wrinkles, those right on the edge, I set it at minimum 200 C and hover it over the wrinkles and watch them disappear, be careful but with practice there is no problem.

 

HK white glue can be removed with cellulose thinners I am led to believe but have never tried it myself.

 

High temperatures and seal the joins is the key.

 

Cheers

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Hi all,

 

I'm far from a covering expert, but by covering the central white film OVER the pink LE, you create a possibility of coming loose by creating a 'pocket' for the airflow. Even a very small gap at the beginning could rapidly become the whole LE once the airflow has found its way 'under' it.

 

I think the white film should be applied first and then overlapped by the pink LE one, hence avoiding to create a 'ridge' for the airflow...

 

Just my 2 eurocent...

 

Cheers & stay safe

Chris

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I've been using HK film for years and I can't remember what temperatures I'd used previously with other brands, but I have found that some colours are different to others in how easily the backing comes off. I've just covered a glider fus in solid white and the built up wings and tail in transparent red. The backing came off very easily indeed on both, but I have used other colours in the past where I have struggled for minutes to remove it.

 

Temperature wise I tack it at 120°C & shrink at 130°C and use a heat gun just to remove any annoying little wrinkles. 

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On 20/03/2021 at 07:03, Wookman said:

...If you absolutely must change colour right on the leading edge, seal the edge with "diamond" tape or a strip of clear covering film.

 

That was exactly my thought when reading the top of this thread.  Tape would also help save the LE from rougher stalk-strikes on landing and keep your join-line intact.

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On 19/03/2021 at 01:08, leccyflyer said:

Agreed -it's excellent stuff, but it does need a hotter iron than Solarfilm and I find the backing is even more difficult to remove. I usually have a very fine T pin that I use to separate the backing -even then it sometimes doesn't come off in one piece.

If you think removing the backing from HK film is tricky you should try getting it off BangGood film. Its well nigh impossible to do without mutilating the colour layer and even then the electro-static attraction such that you can't put the backing film down. It sticks to your fingers like glue!   

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I haven't ever bought from Bangood, so haven't tried the film from the site. The HK film is the first that I've seen where the bond of the backing film was so strong that the backing would sometime tear, rather than come away cleanly. I know exactly what you mean about not being able to throw the backing away. ?

 

Btw - David's model is a thing of beauty and beautifully covered. Love it. ?

Edited by leccyflyer
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I too use the HK film regularly and agree with the observations made. I’ve often wondered whether the Banggood offering is the same product but have yet to find a definitive answer. Some sort of colour equivalents chart would be great too - e.g. which HK colours do you choose to get close to Oracover’s Ferrari red or Silver?

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