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The prop is a 17 x 8 and it was climbing (15sec after launch) when it happened and (on 3S) it was well under 6000rpm. The rev limit is meant to be 8000rpm and it was a “never used” prop. One of the new ones. This was an early test on low power 550W (?)

Now on 4S it is on a GM full carbon prop and pulls far more.

** Note I have all the bits from the explosion, including the broken off piece (Don't know where the attached bit is at the moment) and it was an explosion. I would not call it root either.

AeroN.JPG

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Here is the graph from the fatefull flight. It took 1 minute to fall from 100m.

I used the timing and height to calculate where all the bits were.

GraLast.jpg

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PeteMitchell
1 hour ago, AnthonyB said:

was a “never used” prop. One of the new ones. This was an early test on low power 550W (?)

Very scary! Were you using an offset hub or normal straight one?

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whenever I see someone using an aeronaut prop I try to advise them to bin it .Unfortunately I have witnessed to many expensive models wrecked by a cheap prop.

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2 hours ago, wixy said:

whenever I see someone using an aeronaut prop I try to advise them to bin it .Unfortunately I have witnessed to many expensive models wrecked by a cheap prop.

I agree, well they're ok for most foam gliders and some smaller lightweight stuff but if you spend decent money on a nice glider at least get a set of good quality carbon props for it. 

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I was using an offset hub. They make the prop lay down better. It would seem that they do put more stress on the prop.

 

For 4m gliders I would never go over 400W and a lot less with some.

For 2m only a little over 100W. So you just use whatever works for you and Aeronaut props had wlays worked great for me.

However, I also flew F5B and then it was always "real" carbon props. The unfortunate part is that they are all over square. Like 14 x 14 up to 16 x 16 and even to 20 x 13. These are all RFM with the matching cranked and twisted centres. This is NOT an F5B model, but more a F5J-Type R.

So now it will only get carbon props and straight centre.... GM 14.5 x 10. I can't find a 15 x 10 but I will guess I will want more power soon and will end up on a 16 x 10.

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There are some new props becoming available,  designed by  Julian Benz and manufactured by servorahmen.

far as I,m aware they are injection moulded glass carbon .

Dont know how strong /reliable /efficient they are but knowing the guys behind the manufactur would presume they have been well tested.

I have stopped using cranked spinners and changed to GM spinners and Props .expensive change but worth paying for the quality of the components and fit.

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My new model finished this week just before Christmas 2020:

A bit of history first:

Hello to the few of you out there who still remember me from the earliest days, from the first year of BARCS’s Thermal Soaring Group in fact!

I have long since given up Competitive T/S but was tempted get back into it & to take up this new fangled Electric Launch discipline.

This also was some time ago and in fact the first competitive year of electric launch T/S so I purchased an Ava from Hyperflight intending to compete in the second competitive season.

However after I had attempted to ‘move heaven’ in the impossible task of reliably setting the maximum possible watts per kilo weight of the model to an acceptable level there transpired an unholy ‘discussion’ on line & in the relevant circles regarding new rules for electric launch, the result being a split with at least two sets of rules immerging. The result for me was that I despaired with it all & gave up the idea altogether!

Fast forward to the second 2020 lockdown, thinking of what I shall next build, or more like it these days, what shall I buy & assemble, it was then I happened upon this silly named ‘Introduction to F5J’ model from Grüner in Deutschland.

Erm it seemed to be a modern but proper model kit, made of wood, sinue & a bit of this carbon stuff which is quite good & the whole thing might take more than a few covid free hours to stick together? So I Googled it to find no other than Hyperflight (I’d heard of them) have stock.

Being the impetuous buyer that I am the next day it arrived but by then I had completed more Googleing & discovered that I had ordered the original kit & there was an updated design called ‘Inside’ with a 6 servo wing available, I want that one!

The supplier was not disposed to change the kit for the new version (don’t go there) so I seriously explored & considered the possibility of my converting the basic flap/spoiler wing to the full six flapping bits version. I decided it was certainly feasible & have since discovered that there might even have been enough wood in the kit left over to do it, other than for the necessary solid wood bits for the extra four aileron/flap surfaces.

Long term gliding mate Ian Nicholls persuaded me with logic to build the kit ‘as is’ (You are still not going to use it competitively, are you? You’ll be doing deckchair sit down & going to sleep floating about!) yep he was right of course, so that’s what we have here.

The six servo wing only kit is available at least from Germany but not for what I consider to be reasonable cost & you would not want or need both wings anyway, if you fancy that then better to buy the full ‘Inside’ kit in the first place!

I must say Mr Grüner certainly knows his stuff, the kit is a quite magnificent example of the relatively new art of laser cutting technology.

I have built British laser cut semi kits of old timer designs which in terms of parts fitting together do not begin to approach the quality of this kit.

To be fair this was my first example of a kit specifically designed for laser technology production, come to think of it it is also the very first modern built up kit design I have built which has a multi coloured Autocad plan!

As a retired engineer the multicolored plan is really good, so much easier to read at least for old tired eyes.

Every single part fitted absolutely perfectly even down to the geodetic 3mmx3mm point ended/differing angles tailplane braces, not a single part needed a helping hand to fit exactly!

As for those 3x3 braces the afore mentioned British kit would have at best given you a piece of 3mm square & expected you to fashion them yourself!

The balsa was clearly perfectly selected for the task intended & suitably marked on individual parts themselves therefore not lost on the sheet once released.

The parts are retained in the sheets from which they are cut by the usual two or three tabs of uncut material, I released the parts by the use of the point of a No11 scalpel blade which was about double the width of the laser cut!     

During construction of the wing I did consider it rather light & fragile, not a D box type but 1.5mm balsa ribs & riblets on a tubular carbon spar, 2mm dia solid carbon LE, slotted hard balsa TE in the case of the flap area & 1mm ply TE for the outer panels.

It is necessary to take care when handling, I am light of hand but managed to damage a couple of ribs during handling & sanding etc.

However once the covering is applied, I used transparent Orocover & also a Banggood variety, the wing is firm and feels as firm & solid as any built up D box model wing structure.          

The kit contained all parts required to complete the airframe including hardware, wing joiners, unique style dihedral braces, wing retainers, wing servo boxes, GRP horns, wire, snakes, nuts, bolts, quik-links, even magnets for the canopy cover etc, etc but not covering.   

Not flown it yet & it will be another couple of weeks at least before I will be able due to the latest Covid Tier 4 lockdown in our area but I’m certain it will perform excellently.  

 

Regards and as Happy a Christmas as you can manage to all!

Rob Cavell

BARCS 78

Intro F5J 002a.jpg

Intro F5J 001a.jpg

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PeteMitchell
On 19/12/2020 at 15:32, wixy said:

There are some new props becoming available,  designed by  Julian Benz and manufactured by servorahmen.

They do need a cranked hub to enable them to fold flat , at least they do on my Prestige fus. Julian designed them around Explorer/Xplorer fus that he uses so they may fit them without the cranked hub.

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thermaldoctor
32 minutes ago, PeteMitchell said:

They do need a cranked hub to enable them to fold flat , at least they do on my Prestige fus. Julian designed them around Explorer/Xplorer fus that he uses so they may fit them without the cranked hub.

Got a load coming in and will be testing. Only thing I am unsure of is same prop size for 3s and 4s? I will test on both. Dont think same size for both  is optimal. We will see. Plus will do structural integrity tests shame ground is so soft. 

Regards

Neil

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7 hours ago, Rob Cavell said:

Rob Cavell

BARCS 78

Intro F5J 002a.jpg

Intro F5J 001a.jpg

Nice work Bob.    I've recently finished my Inside F5J and look forward to better (and warmer) weather to fly it again. 

As you have found, I thought that the kit quality was very good...    

 

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Oops.... my apologies to Rob,     In my message above, I called him Bob.         I must read things more carefully these days....

 

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  • 2 weeks later...
EssexBOF
On 21/12/2020 at 13:06, Rob Cavell said:

My new model finished this week just before Christmas 2020:

A bit of history first:

Hello to the few of you out there who still remember me from the earliest days, from the first year of BARCS’s Thermal Soaring Group in fact!

I have long since given up Competitive T/S but was tempted get back into it & to take up this new fangled Electric Launch discipline.

This also was some time ago and in fact the first competitive year of electric launch T/S so I purchased an Ava from Hyperflight intending to compete in the second competitive season.

However after I had attempted to ‘move heaven’ in the impossible task of reliably setting the maximum possible watts per kilo weight of the model to an acceptable level there transpired an unholy ‘discussion’ on line & in the relevant circles regarding new rules for electric launch, the result being a split with at least two sets of rules immerging. The result for me was that I despaired with it all & gave up the idea altogether!

Fast forward to the second 2020 lockdown, thinking of what I shall next build, or more like it these days, what shall I buy & assemble, it was then I happened upon this silly named ‘Introduction to F5J’ model from Grüner in Deutschland.

Erm it seemed to be a modern but proper model kit, made of wood, sinue & a bit of this carbon stuff which is quite good & the whole thing might take more than a few covid free hours to stick together? So I Googled it to find no other than Hyperflight (I’d heard of them) have stock.

Being the impetuous buyer that I am the next day it arrived but by then I had completed more Googleing & discovered that I had ordered the original kit & there was an updated design called ‘Inside’ with a 6 servo wing available, I want that one!

The supplier was not disposed to change the kit for the new version (don’t go there) so I seriously explored & considered the possibility of my converting the basic flap/spoiler wing to the full six flapping bits version. I decided it was certainly feasible & have since discovered that there might even have been enough wood in the kit left over to do it, other than for the necessary solid wood bits for the extra four aileron/flap surfaces.

Long term gliding mate Ian Nicholls persuaded me with logic to build the kit ‘as is’ (You are still not going to use it competitively, are you? You’ll be doing deckchair sit down & going to sleep floating about!) yep he was right of course, so that’s what we have here.

The six servo wing only kit is available at least from Germany but not for what I consider to be reasonable cost & you would not want or need both wings anyway, if you fancy that then better to buy the full ‘Inside’ kit in the first place!

I must say Mr Grüner certainly knows his stuff, the kit is a quite magnificent example of the relatively new art of laser cutting technology.

I have built British laser cut semi kits of old timer designs which in terms of parts fitting together do not begin to approach the quality of this kit.

To be fair this was my first example of a kit specifically designed for laser technology production, come to think of it it is also the very first modern built up kit design I have built which has a multi coloured Autocad plan!

As a retired engineer the multicolored plan is really good, so much easier to read at least for old tired eyes.

Every single part fitted absolutely perfectly even down to the geodetic 3mmx3mm point ended/differing angles tailplane braces, not a single part needed a helping hand to fit exactly!

As for those 3x3 braces the afore mentioned British kit would have at best given you a piece of 3mm square & expected you to fashion them yourself!

The balsa was clearly perfectly selected for the task intended & suitably marked on individual parts themselves therefore not lost on the sheet once released.

The parts are retained in the sheets from which they are cut by the usual two or three tabs of uncut material, I released the parts by the use of the point of a No11 scalpel blade which was about double the width of the laser cut!     

During construction of the wing I did consider it rather light & fragile, not a D box type but 1.5mm balsa ribs & riblets on a tubular carbon spar, 2mm dia solid carbon LE, slotted hard balsa TE in the case of the flap area & 1mm ply TE for the outer panels.

It is necessary to take care when handling, I am light of hand but managed to damage a couple of ribs during handling & sanding etc.

However once the covering is applied, I used transparent Orocover & also a Banggood variety, the wing is firm and feels as firm & solid as any built up D box model wing structure.          

The kit contained all parts required to complete the airframe including hardware, wing joiners, unique style dihedral braces, wing retainers, wing servo boxes, GRP horns, wire, snakes, nuts, bolts, quik-links, even magnets for the canopy cover etc, etc but not covering.   

Not flown it yet & it will be another couple of weeks at least before I will be able due to the latest Covid Tier 4 lockdown in our area but I’m certain it will perform excellently.  

 

Regards and as Happy a Christmas as you can manage to all!

Rob Cavell

BARCS 78

Intro F5J 002a.jpg

Intro F5J 001a.jpg

However once the covering is applied, I used transparent Orocover & also a Banggood variety, the wing is firm and feels as firm & solid as any built up D box model wing structure.

After you have dozed off in your chair whilst flying, this model, you may need to fly it back on the fast side and I don't share your view on the wing being firm enough to with stand flexing when flown fast. Even fully sheeted wings, that have modern thin sections, can and do flutter when flown fast, which can occur under the power phase.

That said good to hear you are back in the fold, playing with some toys😉😉

Best regards

Brian

BARCS 230

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  • 2 weeks later...
Martin Church

Have to agree that Grunher CNC are indeed fabulous at what they do. I’ve assembled a laser cut kit if the Slite V2 an f3res design & everything fits together like a glove very happy with what I managed to put together over the Xmas holiday of it.

Expensive & over engineered? yes

Worth every penny? Definitely 

334F9996-E5AD-4293-8508-D2A53186D21F.jpeg

B935992A-107F-4C81-B48C-FC65FF690CE2.jpeg

D84194D8-041F-431C-B59F-4FBFB01F22FF.jpeg

Edited by Martin Church
Few photos for interest
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