SZD45 Ogar

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ian davis
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Joined: 18 Mar 2015, 12:33
Location: Bishopstoke UK

SZD45 Ogar

Post by ian davis » 07 Aug 2017, 08:25

Hi All

I need help with my SZD45, in particular the C of G position. If set up as Robbe recommended life becomes difficult. If the guy from Portugal gets to read this I would be very pleased to hear from him

Ian ;)

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B Sharp
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Location: Perthshire

Re: SZD45 Ogar

Post by B Sharp » 07 Aug 2017, 15:21

In what way Ian?
Brian.

Jilles
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Re: SZD45 Ogar

Post by Jilles » 07 Aug 2017, 23:43

Try the website from the link below
type in some numbers and you get your answer
I find this calculator very good to use as initial setup for a model


http://rcplanes.000webhostapp.com/cg_calc.htm

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ian davis
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Joined: 18 Mar 2015, 12:33
Location: Bishopstoke UK

Re: SZD45 Ogar

Post by ian davis » 08 Aug 2017, 07:44

Brian & Jilles

The model is about four years old and has flown with success many times, my avatar proves that. This year I've flown it twice. The first time it was aertowed at MW. The flight was a struggle,the model flying very fast and not directionally stable. I managed to get it down in one piece.

Last weekend I tried again, this time taking off from the runway at MW. Three high speed runs and no attempt to fly. Particularly embarrassing as the local foamy flying club members who don't come to the Aerotows were expecting great things. I eventually hauled it off and it exhibited the same flight charecteristics.

It seems reasonable to assume that because of its lack of inclination to fly and when it did it was very fast that the C of G is way too far forward.Hence my question to the gentleman in Portugal who has the only other flying example. I have the original robbe drawing which show CG at 4". I have checked both the CG and decalage and both are more or less correct according to the drawings. I have to keep reminding myself that the model has flown before with these settings.

Like me I know that Brian uses the calc that Jilles referred to. Now it gets really scary because putting the numbers in to it delivers 5.23" @ 15%.

Two other calcs cgCalc & Amman Valley Radio control club give 4.32 and 4.33 respectively using the same input data.

I intend to move the C of G back to the latter numbers and see what happens ignoring the 5.23 number.

Incidently, I had a conversation with Adamone about the differences between his calc and the others I use. His response was that there are additional terms in his formulea that are not visible. Not too useful when you can't check out the numbers.

Thanks for your interest in my connundrum.

Watch this space
Ian ;)

Paul_Williams
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Joined: 18 Mar 2015, 17:53

Re: SZD45 Ogar

Post by Paul_Williams » 08 Aug 2017, 11:41

Ian,
just a long shot.
I had a similar experience with a massive trim change from one flying session to another and then a strange spin incident with a different model.
A couple of weeks later when switching on my TX (Hitec Aurora 9) I realised the screen was illuminated but blank. After about 40 on/offs, I found it was failing around 8-10 times, so off to the repairers it went.

What shocked me was that the switch failure was merely caused by oxidisation of the ribbon plug but I was advised that the transmit module was sending garbage and needed replacing !

I hadn't detected any other issues and consider that I had a very lucky escape - might just be worth trying your model with a different TX/RX if to eliminate that as a problem
Paul.

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chris williams
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Location: Blandford Dorset

Re: SZD45 Ogar

Post by chris williams » 08 Aug 2017, 11:58

Don't forget that the CG is only part of the equation...Have you checked the decalage?

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ian davis
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Joined: 18 Mar 2015, 12:33
Location: Bishopstoke UK

Re: SZD45 Ogar

Post by ian davis » 08 Aug 2017, 12:45

Hi Chris

I agree. As mentioned in my post both were signed off as correct to the drawing from Robbe.

Glad you turned up. I would really like to contact the man from Portugal. I know that you once corrosponded with him. Any clues?

Best regards

;) Ian

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chris williams
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Location: Blandford Dorset

Re: SZD45 Ogar

Post by chris williams » 08 Aug 2017, 13:30

So, what is the decalage? No prob with the guy from Portugal, just tell me his name? :D :D :D :D :D :D :D :D :D :D :D :D

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Noël Rumers
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Location: Hoboken Antwerp

Re: SZD45 Ogar

Post by Noël Rumers » 09 Aug 2017, 22:13

I know the guy in Portugal and will contact him.
I will post the result or he will.

Noël

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