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Apr 21, 2011, 08:57 AM
Terry Dunn
mopar_man's Avatar
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WACO CG-4A for aerotow

I've been flying a 73" span Venom C-47 for a couple months now and like it a lot. I decided to build a WACO CG-4A to the same scale for a little historic aerotowing fun. The 65" span WACO is stressed foam (no internal formers) using 1/2" blue foam sheet. The wing is wire cut from blue foam as well. Cellfoam 88 was used for the tailfeathers and nose sheeting. All markings are brushed on acrylic paint.

The glider is just about ready to fly. I just need to tidy up the wing struts, fab some fake vertical struts for the landing gear and finalize the CG. I'm thinking it will be right under 30 oz. RTF. If it flies well enough, I'll finish up the CAD plans and it'll be a build article in Fly RC.

Here are a few teaser photos. Of course there are numerous scale concessions for the sake of simplicity, but I think the overall effect will give me what I'm after. I'll post more pix when it's complete and let you know if it flies worth a hoot. I'm not expecting true glider performance, just a docile plane that behaves well during tow and takes its time coming back down. I guess we'll see how it goes.

Last edited by mopar_man; Apr 21, 2011 at 02:12 PM.
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Apr 21, 2011, 09:59 AM
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Very cool! I am building a CG-4A too, have the sheeted foam wings complete, starting on the fuselage design. Will be watching this with great interest. How are you planning to do the mods to the C-47 for the aerotow?

I have flown the full scale "C8" at the Cavanaugh Flight Museum

Apr 21, 2011, 10:44 AM
Terry Dunn
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I've made a couple of mods to the C-47, but an emergency tow release is the only provision for aerotowing. I guess you could count the BEC as well, since the tow release servo took the total servo count to 7, which I was uncomfortable with on the no-spec BECs of the stock ESCs. FWIW, I also added differential throttle control, which I hope will aid taxiiing on windy days...haven't tried it yet.

The tow release is mounted in the top of the fuselage, above the wing. While not historically accurate (neither is the WACO's rig), it's consistent with what I use on my sport aerotow tugs.
Apr 21, 2011, 01:49 PM
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69SuperBee's Avatar
Hey, that's pretty cool!

Apr 21, 2011, 11:52 PM
Terry Dunn
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I had some time to work on the WACO after getting the kiddos in bed. She is now complete and ready for maiden as soon as the weather cooperates. The forecast is calling for double-digit winds all weekend long, so it looks like I'm going to have to wait a little while...torture.

RTF weight is 29.0 oz, which puts the wing loading at 8.3 oz/sqft. Not too awful me thinks. I put the 2S-A123 2300mAh battery in the nose (5.5 oz) and still had to add several oz of weight. I may give S/N 2 a longer nose so I can cut back a little on the lead...and maybe move the rudder and elevator servos forward. Or maybe I wont dork with the dimensions at all.

At this point, I'm really happy with how things are turning out. We'll see if I feel the same after the maiden flight.

Last edited by mopar_man; Apr 22, 2011 at 12:03 AM.
Apr 22, 2011, 08:36 AM
Wishing I was at Torrey Pines
dee-grose's Avatar
Looks great, Terry! Can't wait to see how it looks in the air.

You did remember to set it up on a different transmitter than your C-47, right?

Apr 22, 2011, 09:47 AM
Terry Dunn
mopar_man's Avatar
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"You did remember to set it up on a different transmitter than your C-47, right?" need. I've got one of those fancy transmitters with TWO control sticks!
Apr 22, 2011, 12:42 PM
Registered User
Terror Flieger's Avatar
Very Cool.
Apr 26, 2011, 02:26 PM
RC 4 Life
sparks's Avatar
Very cool use of foam!
Really looking forward to seeing the shots too.
I did the tow thing before and it's a bunch of fun.
My models had release gear on both planes so both pilots had the choice to "punch out"
Maybe just paranoid redundancy but we both felt better when we went to the field.

Hope you don't mind the suggestion but you can get away with thinner fuselage skin material aft if the CG . .. .. .. might help the nose weight thing.
On the other hand, there is nothing wrong with good wind penetration on a glider with such a blunt nose.

Have you tried tossing it to see how it does?
Apr 26, 2011, 05:24 PM
Terry Dunn
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Thread OP
Thanks Sparky.
I do have releases on both planes...a first for me, but like you said, it's a nice warm fuzzy. I even added fuel tubing over the release switches on both transmitters so neither pilot will have to fumble around looking for the right one if a crisis hits.

Agreed on wall thickness aft of the wing. I considered cutting some pockets there before assembly, but wanted to see how it panned out with minimal effort. I guess that's what prototypes are for. I'm still pretty happy with the overall weight and wing loading.

No test tosses. Wind has been crazy here for quite a while. I'm on the fence about whether to do the maiden as a hand tow or just go for broke and hook it to the Skytrain. We'll see how I feel when the wind finally breaks.

May 05, 2011, 10:11 PM
Terry Dunn
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Thread OP
I just got back from an eclectic, yet successful maiden outing. It's late, so I'll save the story about how we (me and Fitz) were kicked out of two separate AMA-sanctioned flying fields (that's not as bad as it sounds).

It was pretty windy, but the Waco handled it well. We got in 4 flights, including two with emergency releases. The sun was low and the wind was strong so we got in bad attitudes twice and bailed out. In fact, on the last flight, we both cut the tow rope in panic and then couldn't find where it landed. The rope is a small price to pay for two undamaged airplanes.

Since we were the only two guys at the field, the tow pilot had to land quickly and snap a couple shots of the Waco as it glided. So I have very few flight shots and no in-tow pix. That'll happen next time and maybe some onboard video as well.

For now, I'm happy to report that the CG-4A project is a success. More flight testing to come.
May 05, 2011, 10:28 PM
Lee / RC Enthusiast
YarSmythe's Avatar
Nice job! Glad it went well and everything came home in one piece. Can't wait to see it for myself.
Latest blog entry: For your viewing pleasure
May 06, 2011, 07:59 AM
RC 4 Life
sparks's Avatar
Looks like you are trying to keep from smiling.
Must have been allot of fun or somebody was telling you " OK now you guys are out of here".
Seems strange that any RC group, would not like to see this happen at their field.
May 06, 2011, 03:37 PM
Fitz Walker's Avatar
Nah, Sparky, he always looks like that. It was taken before the flight.

First flight was also the first tow. If anything was way out of trim, it would have been very exciting.

There is much less to the "kicked out" than you would think. I'll let Terry elaborate. However, if he doesn't, then we can establish ourselves as the Bad Boys of RC.
May 06, 2011, 04:10 PM
RC 4 Life
sparks's Avatar
Guess I should have waited to post or at least notice that bug red string still attached.
So It may be a nervous smile then or just happy to have the chance to test it.
I love test flights too!

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