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Author Topic: VMC Sopwith Camel General-Purpose Cook-Up In/Outdoor Wa'ever Thread  (Read 6818 times)
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abl
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Andy Blackburn



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« Reply #200 on: October 10, 2017, 07:59:14 AM »

> Even if you just seal it on the bottom surface it will be a big improvement, but to gain the full benefit I'd do
> both surfaces, using the old stand-by of greetings-card cellophane (or whatever it actually is)

I have it on good authority that it's to be found in the packaging of Tunnock Teacakes; a pack of 6 will cost you £1.00 from Tesco.

Andy
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Jack Plane
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« Reply #201 on: October 10, 2017, 09:11:42 AM »

Yummy yummy, Tunnocks in my tummy!  Grin

S'excellent photo, Pete.  From where do you keep conjuring 'em?

I think I'll leave the opening open for now and see how she flies; it'll be easy enough to plant thin acetate on both surfaces afterwards.

Cheers by the way for the positive impressions of my impressionistic level of finishing and minimalist attitude to detail.  There's much to be said for lowering one's workload (never mind one's expectations of oneself!) and settling for a "that's just enough of a casual hint" approach to these things.  Just right for Kit Scale... I hope!   Cheesy
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TheLurker
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« Reply #202 on: October 10, 2017, 01:58:22 PM »

Is it safe to come back in yet?  What with having unintentionally started a small religious war about drills vs KP & other winders. Smiley

That's a very nice looking Camel JP.

Sorry to hear that you had issues with wing warping as well; although it does make me feel slightly less ham-handed about my build.  FWIW I sorted the warped wing (more banana than twist) on mine by repeated steaming / setting cycles over a couple of days and letting it settle between each session. Got there in the end.

Glad you're going to experiment with an unglazed wing opening.  I wondered about doing so but wasn't brave enough to try.
« Last Edit: October 10, 2017, 02:12:44 PM by TheLurker » Logged
Jack Plane
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« Reply #203 on: October 10, 2017, 03:10:45 PM »

Cheers Lurk

I pinned the one-and-a-half awkward wings down earlier and subjected the whole building board to a sustained torturing over the kettle.  It's well dry now and being given a chance to repent overnight, but I shall torture the ensemble again tomorrow morning just to make sure!  Freedom will eventually be granted, but only the day after.  If warp is still there, then on to plan B...

In the meantime, been playing with adding a bit of colour.  I know chalking is the approved method, but I still haven't got on very well with this... probably because my can of spray fixative is about ten years old!  So I've gone back to what worked on the Pink Spit - i.e. acrylic on the underside of coloured tissue seems to give the requisite opacity without too much intensity, and acrylic varnish seems to hold the home-brew in place (cellulose thinners will make the acrylic run).
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FFmodeller
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Russ Lister



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« Reply #204 on: October 10, 2017, 05:10:01 PM »

Looking great Jon .... reminds me that I have my triplane tucked away still 'in disgrace'!  Roll Eyes
I love CO2 ... when it goes well!
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Work In Progress
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« Reply #205 on: October 11, 2017, 05:48:58 AM »

Glad you're going to experiment with an unglazed wing opening.  I wondered about doing so but wasn't brave enough to try.

I guess it's easy enough to add afterwards so the experiment is well worth it. It would be interesting to compare trimmability and flight times with and without. Easy enough to arrange a temporay cover for the panel held on provisionally with the use of a dab of spraymount or similar
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Hepcat
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« Reply #206 on: October 11, 2017, 07:52:59 AM »

Jack Plane,
I have no impressive equation to back me up but I would suggest that you do not worry too much about a hole in the centre section.  I sometimes think old Mother Nature thumbs here nose at our feeble attempts to improve on her way of doing things. Lots of photographs have been taken in recent years of fast aeroplanes flying through (I think) damp air where the low pressure lifting area above the wing is clearly seen as a half ellipse from wing tip to wing tip.  Scarcely a dip or a bump where we are sure a bulky fuselage must upset things.  I think the main mass of air entrains what would be lesser streams to all join the two massive vortices centred on the wingtips.
John.
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Jack Plane
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« Reply #207 on: October 11, 2017, 02:29:15 PM »

No equations needed, John, and I can picture and appreciate your description very clearly.

Here's a question though.  Your scenario describes a modern streamlined full-size aircraft with I assume a fast aerofoil section, whereas would anything like this clean semi-ellipse be happening with my draggy little model of a WW1 biplane proceeding at bicycle-pace?  Might not the local effects of obstructions around (or holes in) the wing play a greater role here?

Questions of messing up wing-efficiency and increasing drag aside, what might be a worry is the possible effect of any extra turbulence on the fin/rudder.  The rudder, I've discovered, is key in keeping the model in a fairly tight circle indoors, and needs to remain fully effective when the power tails off, yet the inner wing down-tab is still working (in the absence of torque to counteract it) to roll it the opposite way!  That would be interesting to observe with the centre-section hole both covered and open.
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ZK-AUD
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« Reply #208 on: October 11, 2017, 04:44:16 PM »

The way I conceptualise the Reynolds number thing for myself and in a very embarrassing unscientific manner, is that a bucket of water behaves the same but differently to a drop of water,  if you think about what they both do in similar situations.  How air behaves is just fluid dynamics and I think our little babies are very much at the drop of water end of things.  I don't think the C/S arperture make a jot of difference in this model to be honest.  My one certainly flies really well without any form of covering on it.
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Jack Plane
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« Reply #209 on: October 12, 2017, 06:51:52 AM »

Cheers for that ZK.  First thing I've got to do of course is get my model to actually fly in the first place!

Markings today, assembly and rigging tomorrow.  Then there's a local indoor session this Saturday (too windy now for any outdoor tests), so I'll just have to go for it!  Shocked

In the meantime, Neville is looking jaded, suitably sullied with castor-oil and smoke, but strapped in and good to go.

PS Markings all done, penultimate weight of everything (except any balancing lead?) a shade over 40g  Smiley
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« Last Edit: October 12, 2017, 08:36:51 AM by Jack Plane » Logged
rgroener
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« Reply #210 on: October 12, 2017, 08:47:09 AM »

Looking good, He should wash his face from time to time Grin

Maybe I just missed it... but is the pilot made of wood, or what was the material you used for it?


Roman
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Jack Plane
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« Reply #211 on: October 12, 2017, 09:08:27 AM »

Roman, Neville was carved and sanded from a lamination of two bits of 6mm balsa (goggles originally cut from paper), sealed then painted with acrylics, selectively shaded in with a bit of Fineliner black ink, grimeyfied with pencil lead, then given a coat of acrylic lacquer.  Total weight about 0.5g.

He's a Captain, face got a bit messed up in a Pup accident in 1916, but he's skilled at night-flying and increasingly dangerous to the Hun.
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USch
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« Reply #212 on: October 12, 2017, 02:16:37 PM »

About the "hole in the wing" argument.
Years ago I was very active in Indoor Hand Launch Gliders, low ceiling. These IHLG are a very susceptible instruments to judge improvements. During a session you get very close results if you launch consistently, results within a few 0,1 seconds.

Now these models do have variable wing section, having very thin flaps which will bend up during launch and bend back to a highly cambered section during glide. During climb the section is near to a flat plate with almost 0 camber and about 3% thickness, during glide about 4-5% camber. The flap is about 50% of the wing chord. On the centreline the flaps are divided and offer a big slot as in the picture.

Of course one try's to close this gap in some way, also because during glide the CL must be quite high so surely the air is spilling over from the underside to the top worsening the efficiency. So one day, after having done some consistent launches' I added on the underside a thin mylar strip to one flap  to bridge the gap and seal the "hole" in the wing.

Surprise, surprise, sealing the gap did not have ANY effect on the times or trim, over about 10 launches not even a hint of difference. Dont' ask me why  Huh
Some pic's to show the section in climb and glide and the gap in the center of the wing.

Urs
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piecost
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« Reply #213 on: October 12, 2017, 05:23:07 PM »

For those interested; I have attached a comtemporary report quantifying the effect on aerodynamic efficiency of the wing. It does not cover impact on the empenage or stability. Note that the Camel featured plywood fences either side of the cutout to reduce the effect somewhat.

Frank Tallman, a famous Hollywood movie pilot restored a Camel and had this to say

"In military shows I have ground­strafed, and as soon as the airspeed reaches 130 or 140 mph the nose be­gins to hunt up and down, and the elevator becomes extremely sensitive. I feel that this action is due largely to the square windshield between the two Vickers guns, causing a substantial burble over the tail surfaces. "

He attributes sensitivity due to the windscreen (an effective spoiler), not the cutout.

Taken from Flying the Old Planes
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Hepcat
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« Reply #214 on: October 12, 2017, 06:23:58 PM »

Thank you Urs and Piecost for those interesting replies.  Piecost, you must have a lot of 'pull' with the Air Ministry to get those test reports so quickly just for the benefit of VMC. I guess they are what we would expect; some loss of maximum efficiency but not enough to cause a vertical dive into the nearest cow pasture.
Urs, your beautiful glider causes a bit of head scratching.  All I can think is that there is high pressure air on the bottom of the wing and low pressure on the top. Can the narrow gap between he wing panel roots act as an orifice?  The high pressure air below the orifice would try to squeeze through the orifice to the low pressure area above but passing through the orifice it would speed up and therefore lose pressure, apparently just supplying more low pressure to the top surface! I will deal with perpetual motion next week.
John
   
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« Reply #215 on: October 12, 2017, 07:38:26 PM »

Interesting report PC. I guess it's a case of practicality winning over a slight loss in performance. In any case at the low Re no's of this model I couldn't see it having any more effect than that due to the slight loss in area.

The effect that Tallman noticed and attributed to the windshield, is more likely to cause a problem and experience hasn't shown this to be the case.

Your experience URS was a little bit surprising - I would have expected a bit of loss with flaps down - when the gap is maximum, and I'm sure John(Hepcat)'s explanation is close with the flap's up.

I'm waiting for your enlightening article on perpetual motion John Smiley

Well anyway have fun with it Jack.

John
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Jack Plane
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« Reply #216 on: October 14, 2017, 04:35:59 AM »

Done.  Smiley

AUW 44g (motor+prop 11.3g, airframe 30g, nose-lead 2.7g).  Could be lighter (Esaki instead of domestic, less heavy-handed with the paint, more radical with weight-saving, especially at the tail, etc), but it's true to the kit which was the main thing.  Loading comes in at 0.53g/sq in, which isn't that bad really...?

Rigging was fiddly but really lifts the look!  I used bait-elastic (very fine with huge amounts of give) unwound into lengths and stained with metal-grey acrylic before sewing and CA'ing it in place.

Adjusted the G-63 to give about 25-30secs of medium thrust before decaying.  Its a bit breezy out, but I'll nip over to my local rec ground for a few chucks before heading on to Newbury for some brave indoor action later this morning.
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« Reply #217 on: October 14, 2017, 04:41:12 AM »

Super-smart job. The rigging looks terrific.
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TheLurker
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« Reply #218 on: October 14, 2017, 04:56:51 AM »

Rigging!  Now that is dedication to a cause and it looks the business too.  We demand a tutorial.
Good luck for the first flights.
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Pete Fardell
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« Reply #219 on: October 14, 2017, 05:20:01 AM »

A really super job, Jon! I think this will be 'one of those models' we remember. Tons of character (if that still counts in KS then you're well in!)
The rigging looks great. When you say 'sewn' do you mean you just used a needle and pushed it through? If so, did you go through the wing, or into the strut itself?
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RalphS
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« Reply #220 on: October 14, 2017, 06:00:29 AM »

Nice one Jon.  More smoothing plane than jack plane.
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FFmodeller
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« Reply #221 on: October 14, 2017, 06:19:10 AM »

That looks really great Jon  Smiley

44g sounds ok for the gm63 ... look forward to seeing how it goes.
My Sopwith Triplane was of comparable size but a bit heavier as I remember .... it needed all the power I could squeeze out of the 63.
This gave me problems .... just at the wrong time! (The Nats)
I don't think you will have the same trouble .... the 63 is a lovely motor and mine would purr around for a minute on those good days!
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Andrew Darby
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« Reply #222 on: October 14, 2017, 07:06:06 AM »

Looks super!  Like Pete says bags of character...

Andrew
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abl
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« Reply #223 on: October 14, 2017, 11:55:26 AM »

I had a good look at Jon's Camel at Newbury today and I have to say it does look really, really good.

Andy
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« Reply #224 on: October 14, 2017, 12:22:54 PM »

Excellent work, Jon.  It really looks the part. Well done!

Skyraider
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