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Petrel with a twist

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John Vella
Posts: 223
Joined: 20 Mar 2017, 22:09
Location: UK

Petrel with a twist

Post by John Vella »

Yesterday me and a friend went sloping with a recently bought European "professionally " built Petrel to 3.5 scale of 5m span. I was offered a fly and on first view it looked well built and finished. However it was flying with quite abit of right aileron trim. So I started to explore the flight envelope. The dive test and stick free stability were fine. The control harmony was good. Then stalling and tight turns showed a fairly marked right wing drop followed by a full departure and spin. We then did a rigging alignment check and discovered that the right wing incidence was a couple of degrees or so more than the left ( at the wing root).
To solve the problem would require extensive surgery around the large fuselage root fairing, having moved the incidence pin and reblending the fairing from leading to trailing edge. This seems alot of work with refinishing and painting the fuselage. The question is why doesn't this model glider manufacturer take the trouble to rig check his build before finishing the fuselage and wing root fairing ? The error was very easy to see if you took the trouble to view from 10m behind the glider. This does not see to be a "professionally " built job to me. Regards John.

Tom Pack
Posts: 80
Joined: 18 Mar 2015, 23:33
Location: USA

Re: Petrel with a twist

Post by Tom Pack »

Exactly.....without a name it’s just a “story”!

John Vella
Posts: 223
Joined: 20 Mar 2017, 22:09
Location: UK

Re: Petrel with a twist

Post by John Vella »

Patience Gentlemen, there is some serious negotiations going on here ! For those who can't work it out it will be revealed in the fullness of time.

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chris williams
Posts: 1085
Joined: 10 Mar 2015, 10:50
Location: Blandford Dorset

Re: Petrel with a twist

Post by chris williams »

I suspect that top end 3D CAD drawing, coupled with laser cut parts, might lead to the conclusion that everything should be a perfect fit. In my old-fashioned 2D world, I spend an inordinate amount of time matching one wing's incidence to the other. To do this, I always rely on the MK1 eyeball... ;)

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RobbieB
Posts: 548
Joined: 07 Mar 2015, 22:22
Location: North West

Re: Petrel with a twist

Post by RobbieB »

The MK1 eyeball................when you've finished with the techy incidence tools the final ultra hi-tech eyeball check is foolproof.

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chris williams
Posts: 1085
Joined: 10 Mar 2015, 10:50
Location: Blandford Dorset

Re: Petrel with a twist

Post by chris williams »

If it is the one I think it is, it is not laser cut! CNC'd with router. Is there any difference in the end result?

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Barry_Cole
Posts: 1331
Joined: 10 Mar 2015, 09:30
Location: Hampshire UK

Re: Petrel with a twist

Post by Barry_Cole »

Less smoke????

8-) 8-) 8-) 8-)

BC

NeilTarver
Posts: 14
Joined: 19 Jun 2015, 06:02
Location: Shropshire

Re: Petrel with a twist

Post by NeilTarver »

Cliff

The model in question is mine and you are correct, cut with a CNC router. This is the second ARF I have acquired from this north central European manufacturer of sailplanes that can be purchased in kit, ARC or ARF form. The first also had rigging issues but to a lesser extent which I corrected as best as possible without surgery and sold the model on.

But getting back to the Petrel. In addition to the wing incidence I had to correct the tail alignment and fine cracks are developing beneath the Oratex covering on the fuz around the nose and tail which I think is filler cracking. It is a real shame. The construction of the individual airframe components is good in terms of accuracy and craftmanship and the finishing not bad at all (yes there were the usual cosmetics to sort out including paint runs). But the rigging is dreadful.

As I'm still in full time employment and travel extensively for work building a vintage glider is not feasible for a few more years so I generally fly modern glass gliders. And while I would like another larger vintage glider in addition to the Petrel ARF options are limited. I will certain not go with another product from this particular company (the Petrel supplier).

Perhaps I should have searched for CW Petrel that someone would have been prepared to sell.

Regards

Neil

John Vella
Posts: 223
Joined: 20 Mar 2017, 22:09
Location: UK

Re: Petrel with a twist

Post by John Vella »

Okay, I am sure most people would have worked out the manufacturer of this Petrel. I am incredulous that Old Gliders of Poland would send this glider out without even a basic rig check. Regards John.

SP250
Posts: 130
Joined: 18 Mar 2015, 06:19
Location: North Shropshire

Re: Petrel with a twist

Post by SP250 »

Good job the PWS 101 I aquired was one built from a kit of parts then.
Thanks for the heads up, as it is my winter project to cover and paint.
I will put a rigging angles check as the first job, while it is still relatively easy to fix any problems.

John M

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