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Old Jan 08, 2012, 10:45 PM
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1978 Kraft/Kyosho Chipmunk ARF: let's build and update a vintage foamie!

How about a vintage foamie build/modern update thread? Lots of the guys in this forum were likely quite young or not yet born in 1978 and might not be aware of the state of the foam ARF art 34 years ago....

In the late 1970s, Kraft (of Kraft radio systems fame) released a couple of interesting foam electric ARFs. A 40" span DHC Chipmunk and a 44 inch span Cessna Cardinal. Pretty daring at the time, as there were almost no electric foam ARFs on the market back then.

They were expertly tooled, molded and produced for Kraft by Kyosho, who set a very high bar in their small molded foam ARFs of that period. Beautifully molded, very fine grain foam in the fuselage, great paint finishes, thin lightweight injection molded cowls (yes, injection molded, NOT vac form!) As many of you know, Kyosho, in addition to these models and their own ARFs, also produced the VERY nice Cox foam ARF 1/2A and early electric models...the RF-5 Sportavia, the Cessna 210, the Cessna 182, etc. All were beautiful examples of foam and plastic injection molding art. The models were NOT cheap in the late 1970s. As I recall, the Chipmunk, with motor, prop and no battery or radio was around a hundred bucks.

My very good friend Richard Ng scored a couple of these Kraft Chipmunks over the years at R/C swap meets. He decided to let me convert one (the less virgin one) to modern electric power for us both to enjoy and to bring to SMALL 2012, where we hope to be able to fly with Paul Willenborg's companion kit of the Kraft Cessna Cardinal, which he built in 1978 and is still in nice flying condition today. I will also have my 34 year old Cox Sportavia electric conversion there.

While the airframe is very nicely done and is frankly better than most foam ARFs of today, the electric flight system designed for the Chipmunk is not quite as advanced....

The model came equipped with a state of the 1978 art 05 can brushed motor, direct drive, with an 8" prop. The model was powered, if you can call it that, with a full six cells of 600 mAh nicad power. The kit calls for a Kraft two channel radio, for rudder and elevator control only. I can hear you asking the obvious question...what about throttle control??

There was none. A common practice in electric flight in the 1970's was to simply power up the model with an external power switch. No ESC, no servo activated micro switch, no nothing. The modeler flipped the switch and launched the model. It would fly around until the nicads gave up their last watts, when it would land deadstick, or nearly so. In case the model crashed early, the power system had a fuse to protect the motor and batteries since you could not shut off the motor by radio control. Some guys did rig up micro switches for the power system controled by an extra servo, but that was pretty daring....

I always thought the Kraft Chipmunk was a nice looking little model and thought it woudl be great fun to convert one to a modern outrunner, controlled by a modern ESC, using a modern lipo, and controlled by a modern 2.4 radio system with modern micro servos.

Here are some pictures of a 34 year old foamie kit, nearly new in box. The previous owner did install the decals, poorly in places. Other than that, nothing was done assembly wise. The only things missing are the 34 year old rubber bands and the original foam radio equipment tray that was used to hold the 2 channel Kraft radio system with two mightly Kraft KPS-14 servos and yet another set of batteries, four dry cells for the radio RX and servos. No wonder this poor little 40" ARF weighed in at 30 oz ready to fly! (So they claim...I would bet reality was worse than 30 oz....:..)

At some point over the next few weeks I will detail the updating of this very old but nearly virgin foamie. Plan is to use a 1000 Kv outrunner, an 8x6 prop, a suitable brushless ESC, HXT900 servos and a Spektrum RX. Ailerons simply must be added....what use is a Chipmunk without ailerons??? Will also get rid of the rubbe baded on wing and make the wing bolt on.

More to come.
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Old Jan 09, 2012, 01:21 AM
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Very interesting project, thanks for sharing.

Back in about 1990 I had a chance to buy a full scale Chippie when the Royal Navy sold off their trainers for £15,000 each. Needless to say, a long queue of people formed up almost immediately and I lost out.

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Old Jan 10, 2012, 01:07 AM
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A real Chipmunk for around 25K US back in 1990 would have been a real steal.

I like the blown canopy versions the best...the ones with a birdcage style canopy are just not quite as attractive in my book.

Hope to start the conversion by this weekend...even with the aileron mod, ough to be done in 2-3 nights.
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Old Feb 11, 2012, 02:13 PM
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I, too, am working on a Kyosho/Cox restoration project. Mine is a Cox Skylane 182 that was manufactured by Kyosho in the 1980s. I flew it a few times back in the day with a Black Widow (the original QRC .049 got removed by the original owner for some other project) and had one just like it in 1987....I flew the wings off that one, ended up giving it away. This one was part of a trade, I traded the guy an old Aristocraft 2-ch surface radio and an airboat. Not sure what motor I am going to use, would appreciate any help! I read somewhere that a Komodo 2204-11 will fly it, I have no clue!
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Old Feb 11, 2012, 11:39 PM
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Quote:
Originally Posted by circletree View Post
I, too, am working on a Kyosho/Cox restoration project. Mine is a Cox Skylane 182 that was manufactured by Kyosho in the 1980s. I flew it a few times back in the day with a Black Widow (the original QRC .049 got removed by the original owner for some other project) and had one just like it in 1987....I flew the wings off that one, ended up giving it away. This one was part of a trade, I traded the guy an old Aristocraft 2-ch surface radio and an airboat. Not sure what motor I am going to use, would appreciate any help! I read somewhere that a Komodo 2204-11 will fly it, I have no clue!
I need to post some pictures...the Kraft/Kyosho Chipmunk is almost ready to go.

I have a Cox 182 as well...complete, except for the engine cowl...sigh. Going to convert it fairly soon, even if I have to vac form my own cowl.

I have converted two Cox Sportavias and I have a motor choice that I think works great as an .049 "simulator". Pictures attached.

In my opinion Cox aircraft simply look more realistic and original if they sport a 6" prop. I have been using the BP hobbies A2212-6, which is a fairly high speed prop jet type of motor. With a 6x4 prop, it will make the Sportavia climb at about 80 degrees, out of sight. I use a 30 amp ESC and a 3 cell 1300-1800 mAh battery. Any other outrunner like this will work as well, like the Grayson Hobbies Park Jet series.

This motor gives you the option to manage the throttle and get .049 performance, or you can throttle up and have much better than .049 performance.

Another workable option would be any 1000 Kv "400" class outrunner, with a 7x6 prop, if you don't mind the prop looking a little large.

Kyosho really set the standard in the 1970s for the small foam R/C arf...the Cox Cessna 210 Centurion, the slightly later Cox 182, the Cox Sportavia, the Kraft Chipmunk and Cessna Cardinal really compare very favorably to the best of todays small ARFs.
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Old Feb 12, 2012, 10:17 AM
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Never had the sportavia, but a local fellow had one, sure did soar well. He also had the single channel sailplane, I remember it was a bit cheesy but seemed to fly well as long as the wind didn't kick up. I loved my old EZ-Bee, I'll get me another one day. You could make some beautiful landings with the Bee if you knew what you were doing.
I also owned a Cox "Canario" which was another early electric. real similar to the easy star, pylon pusher that had a six cell NiCd battery pack...I'm pretty sure it was a Kyosho rebrand as well. thanks for the motor info, I would rather have a smaller prop than a giant "rubber" looking behemoth that you see on slowflyer/parkflyers.
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Old Feb 13, 2012, 05:03 AM
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A real Chipmunk for around 25K US back in 1990 would have been a real steal.
A steal is exactly what it was, with the Fleet Air Arm flogging them off cheap....to themselves personally. Not a good deal for the taxpayer.
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Old Feb 16, 2012, 10:17 PM
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conversion is done, got the 2212/6 outrunner from BP today and installed. haven't flown it yet but wow! I'm going to have to fool around with different props....got a 7x4 APC electric on it and I do believe that it will climb straight up. probably going to end up with a 6x3 and lots of throttle management. haven't checked amp draw yet but I am sure it is pulling 30 amps at WOT.....ESC heats up quickly! oh boy, is this going to be fun!
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Old Feb 16, 2012, 10:21 PM
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speaking of Chipmunks.....somewhere I have pictures of Art Scholl performing in the Pennzoil Super Chipmunk at Rockingham Dragway in Rockingham, NC prior to the start of the spring nationals NHRA drag race in 1971......when I find them I'll scan and post them. He performed the "lomchevak" and my father talked about that until the day he died!
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Old Feb 17, 2012, 10:39 AM
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maiden on the Skylane this am...heh heh, I'm going to have fun with this one! 1/4 throttle is equivalent to the old Black Widow .049, it will stay airborne with three clicks of throttle, and WOT pulls it vertical while producing a crazy torque roll! fun fun fun!
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Old Feb 17, 2012, 10:55 AM
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Hi Tom

I picked up one of those airplanes (the Chipmunk) when Tower was blowing them out at around $30 IIRC. It put me off electrics for a loooonnggg time.

The first time I tried a hand toss with no power on- the airplane went over on its back and busted the fin. I glued it back together and decided to just let it rip. The airplane did ROG- and I remember it flying around OK- not much fun, but you could fly it- for about a minute and 20 seconds. At that point, the batteries began giving up the ghost- and you were in trouble. You didn't have enough power to stay airborne- and you had too much to land. The smart guys added a servo and an on/off switch- I just threw the airplane away after it rolled into a ball.

My brother had the Cardinal- that was a better airplane with the stock gear installed. In hindsight- I'll bet another problem was the !@#$%!$% Tamiya connectors.

That these airplanes only flew for a little over a minute got me pissed off at Tower since their ads said the airplane would fly for 4 minutes. Well, bench testing showed maybe a minute and 30 seconds worth of power, that not surprisingly, didn't really change much in the air. Tower basically said tough noogies- and I didn't buy anything from them for decades.

I've since gotten over my aversion to electrics- but I'm still not fond of foam- or Tower Hobbies.

In terms of the airframe though- yeah, it was nicer than most other foamies. Didn't Kyosho do the MRC FF foamies back in the 90s? They were some of the first electric airplanes I had that would really fly- better duration than a rubber ship and easy enough to trim so that they'd survive for quite a while.

Sam
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Old Feb 17, 2012, 05:47 PM
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wow....MRC. Haven't thought about that in a long long time. Model Rectifier Corp was associated with Kyosho so it is possible that Kyosho did in fact produce those FF planes. I had a rubber powered Cessna 180 from MRC that had a geared-up drive......never did get it to fly worth a spit!

this dadblame Cessna Skylane is a blast with the BL outrunner. snap roll on a vertical climb? no problem! it is so sweet to have throttle on this plane and is pretty exciting for a R/E plane.
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Old Feb 18, 2012, 07:13 PM
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glad you liked that motor option....it is fun to throttle back and cruise like it used to with the .049 and it is also fun to power up and enjoy the excess performance as well....

With that same motor and a 3S 1300 pack, I get about 6-7 out of sight 80 degree climbs with the Cox Sportavia....near warmliner performance.

Speaking of the little MRC/Kyosho foam FF scale models...I am also presently converting the MRC Ryan STA....using the little AR6400 brick, two of the long throw sub micro linear servos and a 10 gram outrunner on 2S batteries. Ought to be a great flyer.
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Old Feb 18, 2012, 09:54 PM
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excess performance is right.....never could do a snap roll on a vertical line and keep climbing! I had forgotten how well this plane will snap...yank full elevator and input full left rudder and it pitches it's nose skyward and almost flat spins in a horizontal plane, ending up with the nose pointing down and in a wild "sorta" tumbling stall. If the weather is nice tomorrow I'll get some video of it. Mine has the most beautiful glide, seems to go on forever. power on landings are a beautiful sight and must be set up from way out. oh, I had to reglue the firewall.....I was running a 7x4 prop and it tore loose!
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Old Feb 19, 2012, 02:38 PM
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A 7x4 is a pretty good load on that parkjet type motor...it makes my 3s 1300 packs run pretty hot. I think the 6x4 or even the 6x3 is a better choice. I am using the 6x4 on my Sportavia.
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