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Hospitalised, my own fault - but ?


Colin Leighfield
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A few years ago I had prepared my WOT4 Foam-E and was just about to go out to the patch. Another club member had just started to walk out so I decided to wait and placed my model at the side of one of the set up tables, the port wing was poking under the table however I did not unplug the battery!. The tx was standing on the table and I leaned onto the table with my bum. The table tilted and the tx fell forward pushing the throttle stick open. The model leapt forward and pivoting around the table leg attacked my foot. As I was wearing sandals I got two hefty cuts across the top of my foot. Fortunately with the assistance of other club members the blood was staunched and I took my self off to A&E where I received three stitches in one gash and four in the other. Fortunately there was no nerve damage but the top of my foot still goes a bit numb sometimes.

My own stupid fault but easy to do!

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I recall the OP last year but didn't get as far as the kevlar sleeves which do make a lot of sense. There is a small fleet of Raven foam wings with rear props at NLMFC but they launch pretty well,almost vertically with one hand (left for most of us) on the left wingtip, angled away from the pits.

I witnessed an incident similar to Brian's above in the pits a couple of years ago and it was startling, for how fast it occurred and how long it seemed to take before intervention stopped the motor. No serious damage done, but ...

We should really leave electrics disconnected from their batteries until on the strip and we should all have throttle kills with audible alarms. I'm about to modify my habitual kill switch to a lift-to-move type. Plugging in bottom-hatch batteries on the strip is impractical. However, with two F3A electrics due to be rolled out when our strip is fit, both running 6S, I'm either going to plug in on strip, both top hatch luckily, or fit the electric fleet with external isolators, a la George Worley/BMFA mag.

Which prompts two practical points; George's harness introduces a lot of asymmetry in the lead lengths; I recall there's a propensity for side effects; what's a sensible limit to the difference in length thus created? Is it worse with higher voltage? And secondly, aren't XT 90s a bu**er to get apart? Tried a little graphite; do I abrade the male slightly to reduce the friction, or use a smear of vaseline? Drill holes and fit loops? Advice welcome, these are my first 6S models.

BTC

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  • 4 months later...

MK2 dolly with seperate rx for steering for Rapier twin.

20200606_203720.jpg

20200606_202206.jpg

MK1 used balsa blocks that located into the handgrip in the center assuming it would lift away before the back prop reached it. Wrong. It flew but the rear prop was broken (thankfully the engine stopped too). The balsa block was destroyed. This one has a camera to get a close up of the carnage as viewed from underneath!!

What could possibly go wrong?

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Dave, having been through the launch options with the Vulcan, (over weight and under powered) and various experiments with my funfighter I hopefully can add some useful information.

Bungee - pain in the bum setting it up and nailing it to the runway, prevents others using the strip. Advantage is it can impart massive acceleration in a very short distance and time (the Vulcan is 0 to flying in about 10 yards from a 60lbs bungee!). I don't think you need that sort of assistance. There is consideration of where you put the hook and if the airframe can take the forces applied. Getting the bungee to drop away without becoming entangled in the rear prop is an issue. Nothing worse than seeing it climb out only to realise that its still tethered and following an arc that will not end well.

A ramp will be more faff to store, assemble, nail to the flying field and the model has to be well above flying speed at the end of the ramp to avoid prop strikes.

 

Dolly tests with the funfighter that has more than enough power to self launch displayed very aggressive swing to the left and uncontrollable unless a steering wheel was used. I tried 2 wheels at the front and one at the back as it stopped the "Reliant Robin" roll over effect. I also ended up with the aircraft as low as possible on the dolly to lower the over all C of G and resist it rolling over. Once the model is up to speed and accelerating then it lifts off promptly..

IMHO you have plenty of power and should not have too many issues with the left swing/roll problems so a dolly is the way to go. Bungies and lunch ramps just add faff and complexity with the ultimate issue of non release being the end of a very nice looking model.

Good luck and please keep us posted on progress.

PS - Good launches and not so successfully ones, but overall its been worth rebuilding it 4 times to be able to launch it in a reliable way. smiley

cal_0191.jpg _njt2130.jpg

PPS - I ended up with a peg between model and dolly with the Vulcan as the funfighters have a tendency to lift one wing and then induce massive yaw as one wing has the drag of the dolly and the other doesn't.

Edited By Chris Walby on 05/07/2020 07:36:52

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Thanks for the replies. That smashed Vulcan must have been painful to watch. I have considered the bungee/ramps approach but having a spinney thing front and back sounds like a problem (particularly the front engine).

The mk1 version:-

appeared to work well except for the rear prop eating the balsa blocks plane support on the dolly. Without this issue and the immense power to weight i think the mk2 should work. Went to try it yesterday and found i had the wrong transmitter for the plane Doh!!! The rapier is still on 35mhz 1024PCM being a "now and again" plane rather than a regular hack.

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