He-219 Twin 3696 with Build Link

You got a cool electric WWII combat rig? This is the place to show it off!

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Ed Kettler
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He-219 Twin 3696 with Build Link

Post by Ed Kettler »

Here's the latest from Kettler Flugzeugwerks: a 45" He-219 "Uhu"

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A build article can be found at: http://www.rcgroups.com/forums/showthread.php?t=777842

Scott Stockwell cut the wings and nacelles for me. We got two flights in today, with Scott serving as launch officer (catapult) and Cash as test pilot. I was combat camerman/videographer, but did manage to pry the transmitter out of Cash's hands for a bit of flying. Overall, I am much happier with the Uhu than the Beaufighter. I am running it off a single 2000mah CommonsenseRC 8C 3S Lipo. We could only get about 8200 out of the 2409-18s today, so may retrofit some 2409-12s from the Beau to see if we can get her up to (k, which will help quite a bit.

There's a video in the build article, and more pictures there.

Thanks Scott for foam cutting. This would be very difficult to do without CNC.

PS: Cash did not bring the Buffalo, so the Uhu was safe during flight test[:D]
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Ed Kettler
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Post by Ed Kettler »

Reprogrammed the speed controllers to "hard" timing and now the two 2409-18s are putting out 9000/8800 on the same props, drawing a combined 14.5 amps on the APC gas 7x6 props. Speed improved, as did the climb. One of the guys at the field today had a radar gun, and the average speed was about 43-44 mph, compared to the Hamp at 47/48. I have three 3S 2250 25C cells coming in from United Hobbies, so we'll see if that makes much of a difference in performance.

I will be ordering some 2409-12s shortly to see if they can swing a 8x6 at 9K or run the revs up to 10K on the 7x6 to see if the performance can get closer to the singles. Speed is off a bit, but what really is noticable is the rate of climb and sustained turning. Not looking for 100% equality (the extra wingspan needs to be considered), but something that would be fun and competitive.

Today was just about perfect ... 63F, 3-6 mph breeze, cloudless.[:D] The only reason it wasn't perfect is that the field was very busy and I had to wait to fly [:(] December in North Texas, gotta love it!
Alex Treneff
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Post by Alex Treneff »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Ed Kettler</i>
<br />One of the guys at the field today had a radar gun, and the average speed was about 43-44 mph, compared to the Hamp at 47/48.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Nice airplane Ed. The speed comment is something I have noticed with my 3696 F4F, and also the 3696 combat demo we did at the NATs.

Isn't 45-48 mph fast? When I first heard of 3696 I was thinking they'd maybe go 35-40 mph. Couldn't an RPM change keep them closer to 40 or under? Part of the advance of SSC was higher speeds than in the beginning. If 3696 is already just under 50 mph on a 36" plane, I don't see how the class will end up very survivable.

Today at our field we had 5 guys in the air, and while waiting for the sixth guy to get airborne, we throttled back to save gas. The SSC planes still flew great around 40 mph, and some impromptu simulated combat chasing was more fun - more pursuit involved. Just my two cents, as the saying goes.
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Ed Kettler
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Post by Ed Kettler »

Thanks for the kind words. It is a very distinctive airplane at the field.

From our testing, most of the planes, including Cash's Macchi, end up under 50 mph, which is slower than the SSC birds, who we have radared at 55-60. The planes we have built to date use the same materials and build techniques that we use for other combat birds, but on a significantly lighter airframe. The potential destructive force of the plane can be measured by its kinetic energy Ke=1/2mv^2, resulting in the joules of energy. So a single engine 3696 plane at 45-50 mph has about 160-200 joules of energy, and a typical 40 ounce SSC bird at 55-60 has more than double the energy at 343 - 408.

In summary, you have the same strength of materials needing to deal with 1/2 the usual kinetic energy (assuming you don't get prop hits), and I've had enough interactions with Cash and his flying battering ram (aka Brewster Buffalo) to have a lot of confidence in the basic survivability of the airframes. Most of my planes that have been damaged have had the tails knocked loose, some stripped servos, and other minor but repairable damage, nothing fatal.

I think the speeds are Ok at this point ... they have to look like fighters flying, and they should not stagger about the sky being underpowered. Time will tell.

Happy New Year!


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crash_out
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Post by crash_out »

I agree with that Alex. I typically fly planes that size on 10x7 props turning about 7500rpm. Part of the efficency of electrics come from turning large props at a slower rpm. Trying to emulate glow engines practically elminates that.

On a side note, I've done some testing, and I can get a stock Graupner sp300 geared about 5:1 to turn a 7x6 at over 9k at about 7 amps with 3 lithium cells. No need for a brushless setup(except for longevity, and my planes never outlast the power system anyway). Anyone that's been into electric for a while has a collection of GWS geardrives. The B or C gear could do close to the same figures. Hm. mybe those plans I have for the P-38 might come in handy...
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Post by crash_out »

Oh yeah-are the MAS "electric props" legal? The rules say glow prop. I don't own glow planes anymore, I don't like the idea of buying non electric props for my electric planes....
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Ed Kettler
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Post by Ed Kettler »

Nick,

True statement on the power systems. If I buy the 2409-18 with speed controller and a prop from United Hobbies, I can get the set for $19.95, $40 for the full setup, compared to about the same price for a 2908 and 25A speed controller.

If you went with a brushed/geared setup you could do it fairly inexpensively. The gear noise does sound like a turbocharger [:D]
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Post by Alex Treneff »

Ed, That is a good point about the KE. I guess my thinking was that since the velocity is sqaured, if you reduce the speed by 1/4 (60 to 45 in SSC, for example) you almost halve the energy without reducing armor. That would be great for SSC. A lot of the hits that <i>do</i> manage to mangle a plane wouldn't be so bad at 45 mph.

I don't know exactly how far would be too slow for 3696 so I'll take your word for it, but I can say that my F4F does have plenty of power at 9,000! [:)]

A P-51 at an airshow may be doing 395 at the bottom of the loop - I'm curious what he's doing at the top? Actually I did mean to finish my 3696 P-51 over the break, but Santa gave me an electic biplane to finish and theres too much else to get done! Well, I'm off to the next project! Happy New Year! [8D]
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Post by Alex Treneff »

Out of curiosity, is that clear packing tape, then entirely spray painted? Looks nice!
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Ed Kettler
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Post by Ed Kettler »

Nick, we are still experimenting, so I am trying several different props to see what works best. Nothing is set in Jello yet, so try stuff and please report back your findings.
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Ed Kettler
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Post by Ed Kettler »

The plane was taped with a mix of clear, white and black (underside of one wing) tape, scuffed with steel wool, wiped down with denatured alcohol, then sprayed with Krylon plastic primer. I let it sit 24 hours to allow all of the solvents in the primer to out gas, then airbrushed the color coats with Polly Scale acrylic model paints (RLM 75 and 76). Seems to be holding up pretty well.

It is very important to get rid of the "shine" on the tape, otherwise the paint won't stick. If you look at pictures of my Hamp, you can start to see the paint flecking off. I used Tamiya spray primer and paints on it, but I did not think it was necessary to do a good job with the prep because the primer was supposed to "bite" into the surface ... wrong[:(] Between the scuffing, alcohol and primer coat, this seems to work. Time (and abuse) will tell.

If I do another one, I will make it a sport plane and use light fiberglass to do the covering ... another skill to learn. It will also have retracts, maybe grow to 60 or 80". Electric twins are much easier to deal with than glow ... plug in, check controls, fly.

I'll check with the P-51 pilots at the museum to see if I can get some speeds for maneuvers. Most of what you see at airshows may be limited by FAA regulations (250 knots unless otherwise approved)
crash_out
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Post by crash_out »

Cool. APC doesn't make an E prop in 9x6 that I'm aware of, but I have several of the "Electric Only" MAS props, and really like them. They seem as tough as glow props of the same size. I don't have a tach to check, but I run my Hacker A20-22L with the MAS E-9x6 on 3s-draws 17 amps static and hauls an 18 oz GWS me-109 around like nobodies business. Kv is about 1100, so I would assume it's turning lsightly more than 9K. Love the Hackers, but I wouldn't risk one in combat unless I get a higher paying job in the near future....
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o1moregil
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Post by o1moregil »

Nice plane Ed
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