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Old Dec 28, 2012, 04:32 PM
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eye4wings's Avatar
Ware, herts. U.K.
Joined Sep 2008
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Off topic??
I thought we were just pooling our experiences following your suggestion (#157) for Ken to use 2, A123 cells (at $49.95 + postage across the pond) for his on-board radio.
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Old Dec 29, 2012, 01:22 AM
Failure is not an option
casor's Avatar
Boyertown, Pa
Joined Mar 2007
825 Posts
We're all a bunch of hijackers....

Thanks for your patience Ken! I have read but not responded to all the posts which have been very helpful. Still trying to understand much of it and yes, I would like to use 123's. Let me keep this short and keep thinking on this....
Thanks again guys.
Rob
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Old Dec 29, 2012, 11:48 AM
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Liverpool, England
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Hi guys you carry on the discussion I am on holiday in Rome celebrating my wifes 50th birthday, wonderful place although no hobby stores found up to now Cheers Ken
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Old Dec 29, 2012, 04:19 PM
...design-build-fly-publish...
eye4wings's Avatar
Ware, herts. U.K.
Joined Sep 2008
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In Rome celebrating wife's big birthday and he's looking for model shops??.. That's called 'sailing close to the wind ' isn't it?

You enjoy the holiday Ken - we'll keep the thread warm for you!

I'm interested to see how that mirror catch works when you get back....
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Old Dec 29, 2012, 06:21 PM
Failure is not an option
casor's Avatar
Boyertown, Pa
Joined Mar 2007
825 Posts
Quote:
Originally Posted by eye4wings View Post
In Rome celebrating wife's big birthday and he's looking for model shops??.. That's called 'sailing close to the wind ' isn't it?

You enjoy the holiday Ken - we'll keep the thread warm for you!

I'm interested to see how that mirror catch works when you get back....
Robin - LOL so what's your point? You never know what you might find in a non domestic hobby shop, auto dealer or parts store. I thought I was the only one that did this stuff....!
Rob
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Old Jan 04, 2013, 07:56 AM
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Liverpool, England
Joined Jan 2005
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Happy New Year everyone!!

No didnt mangage to find a model shop but what a fantastic place, New Years celebrations were something else

Back to it, cut frames and dry fit one of the wings, next is to make the jig to assemble.

With everything on board, batteries, cannon assembly, motors and props she has grown to 7.1Kg which is perhaps a little dissapointing but the cannon has added a lot of weight over my inital target, I guess I am heading for over 8.5kg finished weight.

CG is currently at 140mm, with pilot and cockpit on board I dont think I will need to add any weight up front

I happened across some JXF 18x8 beechwood propellors that I like a lot more than the Biela props, I acknowledge that the Biela props are better made and will probably deliver more power but the hub issue bothers me, I cant see how I can get a scale spinner on and from a cooling point of view the whole motor is blocked.

I will paint the props black, I would have to paint the Biela props anyway as they are too shiny.

Figures for the 18x8 props using 45C 6S - 764W at 34.8A, perhaps a little low, Ecalc suggests that 18x10 is too much for these motors but there is no sign of any strain with 18x8 so might try later on, with over 1500W perhaps they wont be needed, I am not aiming to fly fast anyway, any opinions?

18" is scale prop size so they look nice to me, certainly scary when running at full throttle
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Old Jan 04, 2013, 08:52 AM
Failure is not an option
casor's Avatar
Boyertown, Pa
Joined Mar 2007
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Motor cooling

Ken - I have in the past drilled holes in the spinner backplate and blocked off the rest of the front opening. With the back of the cowl open near the cowl flaps, the air is pulled through the spinner backplate (through the prop holes) since you have created a vacuum as the open aft area is greater than the sum total of the area of the backplate holes.
Rob
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Old Jan 04, 2013, 10:10 AM
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Canada, ON, Owen Sound
Joined Oct 2008
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I have never found Ecalc to be all that accurate. I now look more at the pitch speed and total WOT amps.
I don't see 18/10's bringing the amps above 50, esp on 5s with your 300kv motors. That is certainly safe on your motors. On all my WW2 builds I strive for around 125watts per pound. If this plane can achieve 60-65 mph WOT, it would fly very scale down around the 50% throttle region and still have the balls for emergency manuveurs. 1500 watts should be enough to fly the plane, my concern is the low airspeed,around 48-50mph (my guess). Maybe the huge prop discs will compensate somewhat. Amazing build, I'll look forward to watching the Henschal come together! m2c fwiw Doug B
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Old Jan 04, 2013, 11:55 AM
Now in TN!
J Morgan's Avatar
Chapel Hill, TN USA
Joined Apr 2001
24,702 Posts
Good to see you back on it Ken.
If I may compare, my AC-119K came out at a whopping 30 lbs. Running two Turnigy 5055-400KV on APC 16x12 two bladed props with 6s-5000s gave it 55A and 1250 watts each side. So it was flying at about 85 watts/lb. I've found that twins, or mutli-engined for that matter, don't need the normally spoken "law" of 100 watts or more/lb. She jumps off the runway and cruises at just under 1/2 throttle.
So you're expected AUW of 8.5 kg( or 19 lbs) gives ( if correct) about 80 watts/ lb.
Of course a lot depends on airfoil too but you are getting close. Would be nice to have just a tad more for insurance maybe. Just my 2 cents.
It's a beautiful looking build.

J
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Old Jan 04, 2013, 12:59 PM
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Thanks everyone, Ecalc was out on the 18x8 setup quoting over 900w so I think 18x10 will be better and give me that extra margin of power, the plane does have a large thick wing so I am hoping slow speed flying wont be a problem.

Made the jig for the first wing and just finished the intial glue up, the same jig can be used for the other wing. Will sheet the top surface tomorrow before removing from the jig
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Old Jan 04, 2013, 03:25 PM
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eye4wings's Avatar
Ware, herts. U.K.
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So long as you have 2 or 3 degrees of washout on the outer wing panels slow flying should be fine.
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Old Jan 05, 2013, 02:00 PM
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Started sheeting the wing today and rough sanded the LE, fit on the fuse is great

Yes I have some washout built in to the wing design, I always thought that washout was to improve stall characteristics eye4wings are you saying that it also helps slow flying?
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Old Jan 06, 2013, 03:16 AM
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Ware, herts. U.K.
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Yes, it helps slow flying because a stall usually starts from the tip due to the turbulence spreading inboard. Reducing the load carried by the tip reduces that tendency and although it makes the rest of the wing work harder as it flies at greater incidence it does mean you can fly a little slower before the stall.

It's effectively like having a couple of degrees of flap down through the flight.
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Old Jan 06, 2013, 12:34 PM
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Liverpool, England
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Took the model to the field today to try some cannon test firing and motor run up

Still some fettling to do with the cannon the first shell didnt eject properly but I reckon with the vibration of flight this wont happen

Anyway you get the idea, second shot is a good one

Motors feel really powerful, only 1/4 throttle needed to start the plane moving

RC Henschel HS129 B3 - Cannon Test Firing (1 min 28 sec)
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Old Jan 06, 2013, 01:28 PM
Flying electric since 1986
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USA, IN, Brownsburg
Joined Oct 2000
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Your camera man is right, that is f---ing brilliant!
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