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Folding prop blade strength

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Jolly Roger
Posts: 441
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Folding prop blade strength

Post by Jolly Roger »

For 20 years I’ve happily used both Graupner and Aeronaut folding blades, typically 16” to 18” size to deliver up to 900W. The Aeronaut blades are described as “Carbon” but look more like plastic reinforced with cf.

However I need 1800W+ for my current project and have heard that these blades are not strong enough and that full carbon blades are necessary. I remember there were stories of the standard Aeronaut blades supplied with early Staufenbiel Stratons failing under high power.

Has anyone used Aeronaut folding blades with anything near 2kW?

What folding blade types are others using in larger models?

Thanks,
Rog

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B Sharp
Posts: 815
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: Folding prop blade strength

Post by B Sharp »

Hi again Rog. I use aeronaugt 19 x 12 blades on my 5 metre Alpina 5001 electro driven by an Axi outrunner delivering an the region of 2 kw and a 6s lipo.
It all seems to have held together for the last 8 or so years!
Brian :)

Chris Bowles
Posts: 95
Joined: 18 Mar 2015, 16:12
Location: South Devon

Re: Folding prop blade strength

Post by Chris Bowles »

Hi Roger, I use a GM carbon 18 x10 prop on my 5mtr Thermik, Hacker, 6s 1800+ watt, also with GM props they fold in closer to the fuz than Aeronaut
Chris

Phill Tadman
Posts: 409
Joined: 18 Aug 2015, 20:38
Location: South Cambs

Re: Folding prop blade strength

Post by Phill Tadman »

Torcman offer some beefed up ones with higher rpm ratings here

https://shop.torcman.de/index.php?k=22&lang=eng

Phill

Jolly Roger
Posts: 441
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Folding prop blade strength

Post by Jolly Roger »

Phil - this is a really great link for FES equipment. Huge thanks.

Elliot Howells
Posts: 272
Joined: 18 Mar 2015, 08:18
Location: West Wales
Contact:

Re: Folding prop blade strength

Post by Elliot Howells »

Rog, I've used Graupner 14x10 at around 2.5kw, they hold fine unless I catch a crab self launching... I've bought some RFM blades just to be safe.

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terry white
Posts: 602
Joined: 18 Mar 2015, 21:08
Location: wareham,dorset.england

Re: Folding prop blade strength

Post by terry white »

Hi guys just to add my two penneth. Although Rick (My eldest son and flying buddy) and I have used the Aeronaut and Graupner blades for some time. Now that we are flying more powerful motors we have moved to a proper carbon hand layed up set of blades. What has made us decide on this was an accident on the slope last year. It was a combination of things that gave rise to an accident that should not have happened but it did and although bad enough could have been much worse. The model, my Alpina 4001 had been scraping the slope for some time waiting for the lift to return, when we decided to bring it home on the motor. We had previously been flying her for about an Hour or so giving each other turns on the sticks. We had been using the motor to regain height whenever the lift depicted. Now we fired up the motor only to find that their was just enough power to get us home. Between the landing area and the aircraft was a line of small gorse bushes. defiantly not good to land in! The Alpina made it over these and safely landed on the slope. a little further down then we would have liked, and because of the lack of power surprise earlier the motor was still running on touch down.(WRONG smacked hand and all that)
It was some time later after a cuppa, a new battery and a discussion on how the plane was flying etc. that I picked up the plane ready to give it a launch in the usual way. Rick was on the sticks and we walked to the launch area. Rick standing alongside me checking the aileron trim etc. flicked the motor on to check all was well That is when it happened. One of the blades which must have been cracked on the less than perfect landing, now flew off, traveled the two meters or so and imbedded itself in Ricks upper arm around the bicep. It was in very deep and Rick was taken to hospital to have it pulled out and his arm dressed. Now that this has happened and as always is the case other stories have come to light which together with our mishap has made us change our thoughts to our propeller choice.
The German hand layed-up propellers are not cheap, around £75-85 or more a go but they are much much stronger at that very vulnerable point around the hub. I carry Ricks broken prop blade around with me now just as a talking point and to show just how thin this area is. The Aeronaut and Graupner props are NOT made with carbon tows but just carbon dust put in with the mix. They do the job well most of the time but can let you down. Just please be careful. :roll:

Analyzing the situation later what we should have :-

1) Always land perfectly :roll: without the motor running. :x
2) Always stand behind the prop if you are going to run the motor. :?
3) never go above the manufacture's recommendations regarding motor power
4) make frequent visual checks to the prop during the flying day.

But we all know that don't we :roll: :roll:

P.S. Rick had 4 stitches in his arm. :(

Elliot Howells
Posts: 272
Joined: 18 Mar 2015, 08:18
Location: West Wales
Contact:

Re: Folding prop blade strength

Post by Elliot Howells »

Terry, really sorry to hear about Rick, it's my pet hate, running props with anyone fore or to the side, you regularly see people run up Moki 250's etc whilst stood in front - madness. I start my gassers from behind when possible.

RFM props are hand made carbon tow, and cost around half what you're paying, although Brexshit, the gift that keeps on giving will probably add a good overhead to that come January.

Anyway, happy new year and stay safe, Ell :)

Jolly Roger
Posts: 441
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Folding prop blade strength

Post by Jolly Roger »

Thanks folks for these really informative replies. Hearing first hand stories brings home the risks we take with high revving objects. Hope Ricky is ok.

Those RFM props look like a fair cost/quality balance. I see Bernie stocks some sizes...and some of the are painted white too :D https://www.esoaringgadgets.co.uk/index ... cts_id=918

Elliot Howells
Posts: 272
Joined: 18 Mar 2015, 08:18
Location: West Wales
Contact:

Re: Folding prop blade strength

Post by Elliot Howells »

I get mine from Bernie, he's a good egg.

Get white ones Rog, spraying them is a PITA.

Ellx

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