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Old Jan 02, 2013, 07:20 AM
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Britplan build-off 2013: Contra-Gyro


Hello all, George in particular as the "boss" of this enterprise. I'd like to enter the build-off with an autogiro called Contra-Gyro. It came from Canada originally but was published in Aeromodeller in December 1956 so I presume that makes it legal. It's a completely new undertaking for me as I've never attempted anything like it before and my knowledge of these machines is very limited (read zilch!). I'm utterly dependent on what I can glean from the net and the few plans I've seen! It's going to electric T/R/E and seems a bit small so I've enlarged the plan (in Gimp) by 8%. Rotor diameter comes out a tad over 29". I'll be modifying the rotor head design a little to make it dismantle-able, if there is such a word .
I don't have the original article in readable form but post this garbled one for the picture to show what I'm attempting.
As for voting in Britkit I'm at a loss. Everyone deserves a medal ! I'm tempted to abstain altogether as this is the most difficult decision of all. What merits a vote?? (rhetorical question), size, complexity, speed of build, novelty, ingenuity, daring, attempting new techniques, successful flying and so on? For me it's enough just to take part and see the other projects take on life. I will vote but with my arm up my back.
Last edited by Raf_Bob; Jan 02, 2013 at 07:22 AM. Reason: Forgot pictures
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Old Jan 02, 2013, 09:39 AM
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I'll look forward to seeing this finished, an interesting project. Good luck
Old Jan 02, 2013, 09:43 AM
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Hi Bob, I'll list your entry and use this thread as your build log. That is quite a brave undertaking and I wish you luck with it. I had a Ro-Dart autogiro which eventually flew OK (F/F of course), but the trimming process was - er - "interesting". The contra-gyro should be a bit easier as it should eliminate torque effects, having some control should help too. I'll be watching with interest!

You don't HAVE to vote in the Britkit poll, it's just a bit of fun and purely a matter of personal preference as the models cover such a wide range, the pay-back for everyone who took part isn't in the final voting, it's in enjoying the building and reading all the build logs and ending up with a nice aeroplane for your fleet - that makes us all winners.
Old Jan 02, 2013, 09:58 AM
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Originally Posted by Sundancer View Post
Hi Bob, I'll list your entry and use this thread as your build log. That is quite a brave undertaking and I wish you luck with it. I had a Ro-Dart autogiro which eventually flew OK (F/F of course), but the trimming process was - er - "interesting". The contra-gyro should be a bit easier as it should eliminate torque effects, having some control should help too. I'll be watching with interest!

Yes, having two rotors should make it easier. I wouldn't attempt a single rotor job. A start has been made with the mast fittings and I'll post photos in time.
I understand that these models need more power than conventional planes of similar size so I'm leaving motor selection 'til later when the weight becomes apparent. The squared off nose should make this fairly simple as a last part of the build. Will it fly?? That's the question!

You don't HAVE to vote in the Britkit poll, it's just a bit of fun and purely a matter of personal preference as the models cover such a wide range, the pay-back for everyone who took part isn't in the final voting, it's in enjoying the building and reading all the build logs and ending up with a nice aeroplane for your fleet - that makes us all winners.
Sure, and my comment was not intended to be too serious. Actually, I have voted now but the real pleasure was taking part as you say. Many thanks for running the show. Thanks also to all who entered and posted such interesting and often inspiring accounts of their builds.
Old Jan 02, 2013, 10:35 AM
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Such an interesting challenge I thought I would post a slightly clearer scan for everyone to read about it. Good luck Bob.

Ray
Old Jan 02, 2013, 11:37 AM
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Such an interesting challenge I thought I would post a slightly clearer scan for everyone to read about it. Good luck Bob.

Ray
Many thanks indeed RFJ. This will be a great help in filling in my scant knowledge of this design in particular and a/g's in general.
Old Jan 02, 2013, 11:54 AM
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Watching with much interest, Bob. I built that model when it was first published (I was 12 years old at the time) and remember it well.

I don't think I ever did get it to fly, but not many of my modeling efforts from that era (KK "flying" scale, etc) did. I'm sure you'll do much better.
Old Jan 02, 2013, 01:15 PM
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Watching with much interest, Bob. I built that model when it was first published (I was 12 years old at the time) and remember it well.

I don't think I ever did get it to fly, but not many of my modeling efforts from that era (KK "flying" scale, etc) did. I'm sure you'll do much better.
Interesting to hear from you, Harry, as someone who built it at the time. As to getting it to fly, I hope to but don't hold your breath!
Old Jan 02, 2013, 01:32 PM
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What a great subject to have a go at.
Have you flown autogyros before?

Gordon
Last edited by GeeW; Jan 02, 2013 at 02:15 PM.
Old Jan 02, 2013, 01:38 PM
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Subscribed and watching with interest.
I was at a full size flying field last week and was amazed to see half a dozen or so full size autogyro's being flown, a wonderful sight.
sparks
Old Jan 02, 2013, 03:02 PM
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Intriguing build. I found a .pdf of the plan on the Outerzone site -- here: http://www.outerzone.co.uk/plan_file...ontra-Gyro.pdf

Pete G.
Old Jan 02, 2013, 03:32 PM
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Certainly is an interesting subject but does an autogyro rotor create any torque ? I wouldn't have thought so.
Old Jan 02, 2013, 03:57 PM
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Originally Posted by GeeW View Post
What a great subject to have a go at.
Have you flown autogyros before?

Gordon
No. This is totally new ground for me. Building (including appropriate mods for radio etc), flying and learning about them will be a "learning curve" of unpredictable steepness.
Old Jan 02, 2013, 04:06 PM
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Certainly is an interesting subject but does an autogyro rotor create any torque ? I wouldn't have thought so.
Yes Patmcc they do cause a torque reaction, hence the twin contra-rotating rotors. Some a/g's have had rotors on outriggers to counter torque effects but Laurie Ellis decided to try them on the same mast. He designed a number of interesting unconventional models in the 1950's such as a tailless flying boat, deltas and so on. This model was free flight originally so trimming would have been easier without the luxury (interference??) of radio! Add twin fins to the recipe and this is going to be a challenging build.
I've made a start on the rotor mast. Having a small lathe is a big help.
Old Jan 02, 2013, 05:30 PM
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A/Gs do create a very small amount of torque (bearing drag) it really only becomes apparent when flying slowly.
Contra rotors will not fully cancel the torque out as one set of rotors is always flying in the wash of the other so is markedly less efficient.
Normally A/Gs have the rotor direction set to counter the engine torque which helps in slow speed flight.


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