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oipigface

How to unplug sticky wings?

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oipigface
12 hours ago, Kyri said:

 Can you get an inspection tool camera that you can put inside one of the servo hatches to have a look?

 

Got one on the shelf in my shed. I’ve neededto look inside things before!

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oipigface
12 hours ago, Kyri said:

 

Here are some pics. Unfortunately I didn't take too many pics of this, but I have a few if its of any help (and assuming he used the same construction for both models)

 

That looks like the subspar, which doesn’t (as far as I know) carry much of the flight load. I can (but haven’t yet) look at it by deflecting the ailerons and  flaps. From what I can see of the main spar, it is encased in something and epoxy, but whether this keeps damp out I don’t know. All I can say is that wing feels OK when I try to flex it - but I’m not as strong as a force 6 on Lundy’s Old Lighthouse slope.

I’ve emailed Milan.

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satinet

what's the spar on the tails? I had an idea it was a carbon rod. Or was the carbon rod/tube removable?? Memory fails me.  But I recall skorpions and early extremes had a hollow tube as the joiner coming out of the bottom of the tail, which were sh*** as it snapped on decent landings.

As I recall the spar main wing spar was fully wrapped in carbon fibre, rather than just having a spar cap. Although I can't remember if it had a spar cap as well.  I suspect the spar is probably vertical balsa shear webs like most models. The only model I've seen with a non balsa shear web is the avatar which uses vertical carbon strips with foam as a sandwhich. Although thankfully I haven't seen inside every model I've owned, so I'm sure there are others.

Great design anyway, possibly the nicest all round model I've flown.  Well maybe the fs3, but the Extreme is less bum clinchingly expensive.  I shouldn't have sold my last one. 

 

 

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oipigface

So, Tom, are you suggesting that if it is wrapped in carbon and epoxy, the wood might still be OK? 

I agree with everything you say about the Extreme including remembering the easily broken tubular tail joiners. This one is the same design, but the tubes have a rod inside them. I watched a video on the RTG site yesterday of Pierre Rondel flying one, and it struck me again how elegant the plane is. 

Some time ago I came across a video of a large scale glider having its airworthiness tests. One of the tests involved hanging sandbags from the wings. I could easily do that if I knew what weight to hang off them. Anyone know?

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Witch_1

I have heard it said that tests showed F3B models were pulling 30kg+ on the line.  This would equate to around 7-8g in the turn for a ballasted model, which seems about right as a flying load.  May be worth adding a 25-50% safety factor.

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satinet

I don't know tbh. But i clearly remember the spar being "carbon" in appearance. Maybe the spar is made outside the mould and put in after. You can see the spar from the servo well any way.

My last extreme had solid tail rods which were ok. 

Really the model's only two bad points were the lack of wing ballast and i wasn't a particular lover of pull for up tails due to the short servo arm you need. But i made a lead slug for the joiner.

They even go nice up the winch line tbh. 

Can you see the spar? 

I agree to test the strength. 

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satinet
2 minutes ago, Witch_1 said:

I have heard it said that tests showed F3B models were pulling 30kg+ on the line.  This would equate to around 7-8g in the turn for a ballasted model, which seems about right as a flying load.  May be worth adding a 25-50% safety factor.

I would say it's more - if you try and stop a winch it's a lot of force, never mind the line stretch, Hard to say though.

both f3b models that i've "blown up" actually failed at the bottom of the "bucket" and not on the line. The is the upwards rotation after the dive, after the release.  I've seen other models fail at this point too. 

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oipigface
31 minutes ago, Witch_1 said:

7-8g

This surely has the decimal point in the wrong place? So I should hang maybe 5kg  from each wing?

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Scram

I suspect that's 7-8g acceleration John and oh dear!  McLaren was a bad example clearly. TVR  or Lotus may have been better but you concern about the state of any wood is clearly the relevant point.

Want any MKS DS6125 mini servos?

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isoaritfirst

If you hang 30kg from each tip that should be enough to ensure you don’t break it in flight. 

 

 

 

😂

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oipigface
4 hours ago, Scram said:

I suspect that's 7-8g acceleration John and oh dear!  McLaren was a bad example clearly. TVR  or Lotus may have been better but you concern about the state of any wood is clearly the relevant point.

Want any MKS DS6125 mini servos?

I think you are right, Jerry. I was flying this afternoon, and I'd just lost sight of my bright yellow model against a rather dull grey sky, when I thought: Oh! Maybe he meant 'G'!

Thanks for the offer, but I think the Futabas fitted with new gears will be fine for sporting purposes. I've found two DS 6125e's for the rudder and elevator.

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oipigface
1 hour ago, isoaritfirst said:

If you hang 30kg from each tip that should be enough to ensure you don’t break it in flight. 

 

 

 

😂

Sorry, Mike. I'm not sure if this intended as a joke or not. My object is not to test it to destruction!

Anyone got any sandbags I can borrow?

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oipigface
6 hours ago, satinet said:

Can you see the spar? 

Yes. I had a look at where it passes the servo wells. All I can see is carbon cloth, well soaked in epoxy or something. (I would have taken a picture for you, but didn't have a camera with me.)

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Witch_1

Hopefully if you read "g" as acceleration my earlier post then made sense.  If you have carbon in the shear web then it's not similar to the Crossfire or Shinto plain balsa web.  It's probably fine.

We could try the 30+30kg test on Mike's Shinto to establish a baseline......

  • Haha 1

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