Propeller safety

[Jon H]

I am member of two clubs at the moment and both have suffered hand in prop incidents in the last few days.

One (which i saw) was an electric pusher prop catching someone out on a hand launch and putting some hefty slices in said hand. luckily nothing a few stitches wont sort out but enough bleeding to satisfy any hollywood movie.

The other involved a 60 2 stroke running at high power and while the NHS are doing their best i believe we are looking at lost digits.

It only takes one moment of distraction or slip of concentration for this to happen. I know we all know this already, but its always shocking when a propeller takes a chunk out of someone so its worth taking a pause to perhaps reflect on your own procedures, double check club first aid kits and procedures etc.

As i deal with engines and props every day i really have to try as it so easy to get sloppy.

Look after yourselves

[Trevor]

Never nice to hear of injuries but, as you say Jon, we all need these reminders to keep complacency at bay.

Incidentally, on the subject of launching pushers, surely one of the advantages of electric is that there’s absolutely no need to start the motor before the model is launched.

[Chris Walby]

Jon, Thanks for the reminder and as you say safety first.

Trevor,

When hand launching my electric funfighter there was a delay on the motor spooling up to speed + it seemed easier to flick the throttle hold off at 3/4 throttle …. wait and then wait some more (4 seconds) to ensure the motor had stopped accelerating and the launch the model. This seemed to reduce the amount of torque roll as it could get inverted before you had any control...

I now have a Funracer and I do the same but full throttle on medium rates with the (mode 2) right stick in the bottom left corner until its up to a flyable speed.

My delta is a pusher, but its best launched from the wing tip with little effort (the more you try of lob it, the more yaw you induce - no rudders so bad news).

The Can Doo deserves respect as you would expect

[Former Member]

[This posting has been removed]

[Jon H]

The rear pusher incident was an mpx funjet. caught the back of his hand/finger as he let it go

[leccyflyer]

For launching the Zagi type flying wings you also have the pizza toss method, where you have the nose of the model in your throwing hand above your head and bowl it like you would throw a ball with a flick of the fingers, only firing up the motor once the model is away. For pushers, with a decent chuck, preferably by someone other than the pilot, there's no need to have the motor running on launch.

[Trevor Crook]

Those sound nasty incidents, hope both victims recover ok. A timely warning, Jon, easy to get complacent with either power system.

I was a bit surprised by the Funjet incident though, as several of us in my club operated them a few years ago with no incidents, also the similar HK Radjet. I always felt my hand was down and clear as the prop came past it, but maybe each launch was a close shave.

[Chris Walby]

Leccyflyer, I can't see how I can hold my Yeti by the nose (soft battery bay cover on the top and tapered slippery covering on the underside. There's nothing to get hold of unless you hold the motor mount (not putting my fingers there with it on throttle hold or not). I can't hold it by the TE as its entire length is control surfaces. Can you post a photo cheers.

Previously mentioned light Frisby style throw without inducing yaw as I hold the wing LE near the wingtip my hand is never close to the prop.

[Scott Edwards 2]

Whenever I'm starting an IC engine I mentally slow everything down, and consciously make very wide, slow exaggerated movements. It makes you very aware of where your hands are. I know I look like a knob, but I've never even had a tickle in 30 years.

[Jonathan M]

My old woodwork teacher once pointed to the heavy machinery in his workshop - table-saw, planer, etc - and asked:

"What colour are they?" When I replied grey-metal, he said "No, they are red, and they're extremely patient, they'll wait decades to get you." I've been lucky so far, only two minor mishaps - a chunk taken out of my middle-finger pad when it contacted the anti-acoustic cutout on side of a spinning 12" saw-blade, and later on I left several thin salami-slices off the pads of two other fingers on the infeed-table when brushing dust off near the mouth of the planer. Both incidents happened either when I was working under commercial pressure an/or it was late in the day and I was tired.

I suggest we adopt a similar mantra: "Those engines are all RED and they're extremely PATIENT, they'll wait years to GET YOU..."

[Mowerman]

After getting caught a couple of times when launching my Wildwing (speed 400 Gunther prop) I fitted a hook and used a catapult l;aunch, just let the model get clear of the bungee line with a bit of height before starting the motor..

[Cuban8]

Posted by Scott Edwards 2 on 19/07/2020 08:49:32:

 

Whenever I'm starting an IC engine I mentally slow everything down, and consciously make very wide, slow exaggerated movements. It makes you very aware of where your hands are. I know I look like a knob, but I've never even had a tickle in 30 years.

 

 

I thought it was just me.....I perform the same type of action pulling my hands outwards from the prop in an arc. I trained myself to never draw my hands directly towards my body without the outwards motion first, it's now second nature and I never have to conciously think to do it. Makes me shudder to see modellers pulling their hands directly towards themselves and only just (usually) missing the rotating prop tips after releasing their grip on an IC model when using a starter.

Obviously, disconnecting glow clips and tuning are carried out only after one is safely behind the prop.

Edited By Cuban8 on 19/07/2020 09:49:33

[Peter Miller]

Many years ago there was a story and photos in RCM&E of a chap who launched a pusher powered model with an Irvine 40.

Took at least two fingers off but I believe they managed to sew them back on.

For this reason I refuse to even touch a model with the prop not right at the front.

There is another thread on this subject on this forum

[Former Member]

[This posting has been removed]

[leccyflyer]

Posted by Chris Walby on 19/07/2020 07:49:04:

Leccyflyer, I can't see how I can hold my Yeti by the nose (soft battery bay cover on the top and tapered slippery covering on the underside. There's nothing to get hold of unless you hold the motor mount (not putting my fingers there with it on throttle hold or not). I can't hold it by the TE as its entire length is control surfaces. Can you post a photo cheers.

Previously mentioned light Frisby style throw without inducing yaw as I hold the wing LE near the wingtip my hand is never close to the prop.

It's just a standard Zagi "Pizza toss" - you can either have the nose of the model on your upturned palm, fingers underneath the nose as if you were a waiter carrying a pizza above your head, with your thumb over the nose, or, less conventionally , you put your thumb under the nose and your fingers on top. The former option lets you flick the model with your fingers, as if you were a girl throwing a ball, or Dick Emery saying "Ooooh you are awful but I like you!" That way you never put your launching hand anywhere near the prop and the follow through, as if you were bowling a ball makes sure that you hand is a long way from the prop as the model is launched.

Back in the day my mate Kev preferred to have his fingers wrapped round the trailing edge, within the prop arc, with the prop resting on his fingers as he could get a monstrous launch that way - never fancied it myself.

[Jon H]

Pusher hand launch models scare the pants off me. I always refuse to hand launch them if asked as they seem like an accident waiting to happen. The only time i will do it is if the model is launched with no power and then the motor cranked up just after launch.

As for all those questioning how close their launches are we need a high speed camera to check that. In the case of this recent incident, the chap had launched this model loads of times but this time he said it just slipped very slightly as the wind caught it and clearly that was enough to make the difference.

As for i/c i really have to try hard to stay on the ball as i start engines with such regularity at work that its so easy for it to become routine and concentration to be lost. Its for this reason i try to test run engines in batches of no more than about 5.

[Nigel Grant 1]

I launch my Can Do with a left handed under-arm lob hoping that my hand flips up out of the way of the prop. My right thumb is on the elevator/aileron stick for control. Its a bit nerve wracking both for concern about my launch hand and also controlling the plane as it accelerates up to a comfortable height. Without plenty of power on, the model just flops to the ground before you could flick on the throttle, just as Steve J describes for his Fun Jet. I have the gauntlet from a glove slid over my wrist for protection. The Can Do is fun to fly but next time it needs repairing I think I'll retire it as I am losing my nerve and as Peter says, the prop is much safer at the front of the craft.

[MattyB]

Zagi wings are fine to launch (well, apart from the noise...) - you can always chuck them motor off - but the highly loaded Funjets and Radjets are nasty things. When I had one I always used the club bungee launcher, but setting that up was a faff so I now just choose tractor models if I want a hand launched speed plane. Maybe you could extend the fins below the model and DLG it instead?

Edited By MattyB on 20/07/2020 16:41:21

[Trevor]

I’ve always thought there’s a gap in the market for someone to invent a variation on that plastic flexible stick thing that dog walkers use to throw the pooch’s ball. It would help in launch8ng marginally powered EDF models too -potentially much less hassle (and safer) than a bungee.

[Mike T]

Grip is key and I don't (or wont) launch anything I can't get a proper grip on. I damaged my Radjet when my fingers slipped in its finger holds, leading to a bit of a girly launch. I cyano'd in some sandpaper patches and can now give it a proper manly heave!

[John Tee]

I was a casualty only last Wednesday. Had my Dactyl down the field to be noise tested as we have a fairly strict noise code after a complaint last Year. Powered by an HB61 PDP ( a quite powerful motor) with an 11* 7 3 blader pusher prop. Got the engine running and bent down to pick up the model to take to the test area (it doesn't fit on my Great Mate model stand ) and just put my hand into the prop arc. ""luckily"" it was just the tip of the prop that bit me and chewed up the tip of my little finger and took off half the nail, a third of the nail of the next finger and distorted the nail on the middle finger. Cleaning up at home and taking off the bandages I found I had also sliced the little finger for 2 1/4 inches from tip to nearly bottom. Spent 1 3/4 hours at the Minor Injuries at the local hospital. Had photos taken in case a skin graft was needed - not as it happened and an xray then back to the nurse for proper dressing. Another visit to my own surgery for redressing Friday and another redressing next Thursday.

There was nothing to sew back on as the blade hit vertically so to speak and sliced the finger tip to shreds.

I have been moving this model around my workshop and garden for months while working on it holding it by the trailing edge and nose (no engine running) and it was an automatic careless move to do the same with the engine running(first time).

I have now fitted a rather crude carrying handle in front of the engine to keep away from the prop in future. If anyone remembers the \Dactyl there are wing tip plates to be added. Being a 3 blader I got an extra slice per rev. Luckily I will survive and was lucky to get away with such light injuries. BE VERY CAREFUL AND THINK ABOUT WHAT YOU ARE ABOUGHT TO DO.

John

Edited By John Tee on 20/07/2020 17:45:44

[Tim Flyer]

Given these pusher prop set ups are potentially so dangerous.. would it be a good idea to think about using a ducted fan unit on the rear instead to shield the user from the propeller arc??

I certainly second Jon’s comments above that we all need to constantly evaluate our engine handling procedures. When these accidents happen it is so fast with a moment’s loss of concentration. Nothing can be totally safe but good procedure can certainly reduce chances of mishap. 

Edited By Tim Flyer on 20/07/2020 18:49:43

Edited By Tim Flyer on 20/07/2020 18:51:28

[Stephen Smith 14]

I always launch pushers by holding the wing tip of the right wing with my right hand and the transmitter in my left. I hold the plane out in front of me open the throttle and toss it with my right hand, never lost any body parts and never had a failed launch. Simples

[John Tee]

Don't think that would work with a Dactyl Stephen, big wing tip plates nothing to hold and too heavy.

John

[J D 8]

Remote needle valve may be good as that way around the prop will pull an errant digit in where as in tractor a touch from behind gets knocked away.