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Building Tips and technical articles. => 1/2 A building. => Topic started by: Mark Mc on November 04, 2016, 12:05:08 AM

Title: TD-4
Post by: Mark Mc on November 04, 2016, 12:05:08 AM
I had a build thread for this one over on the Cox Engines forum, but I figure someone over here might like to see what I made.  I have a Cox TD-4 I got two years ago.  I didn't want to fly it, since it was made between 1956 and 1959, so I decided to make myself a replica of it.  Here are the finished photos of the completed replica along with the original Cox model.  I have since replaced the landing gear with an original set of black wheels.

(https://s5.postimg.org/44kmz58t3/DSCN4922.jpg) (https://postimage.org) (https://postimage.org/)
(https://s5.postimg.org/7cp4c6v2v/DSCN4925.jpg) (https://postimage.org) (https://postimage.org/)
(https://s5.postimg.org/q6ax96tav/DSCN4928.jpg) (https://postimage.org) (https://postimage.org/)
(https://s5.postimg.org/6cytghfx3/DSCN4930.jpg) (https://postimage.org) (https://postimage.org/)
(https://s5.postimg.org/dhl839ck7/DSCN4934.jpg) (https://postimage.org) (https://postimage.org/)



Mark
Title: Re: TD-4
Post by: Andre Ming on November 04, 2016, 05:31:16 PM
NICE!

I understand completely about not wanting to risk the original.

Title: Re: TD-4
Post by: john e. holliday on November 04, 2016, 06:30:52 PM
They both look great.  Now which one is the original? ???
Title: Re: TD-4
Post by: Dane Martin on November 04, 2016, 07:50:54 PM
They both look great.  Now which one is the original? ???

The yellow and blue one......   ;D

They both are fantastic mark!
Title: Re: TD-4
Post by: Mark Mc on November 06, 2016, 11:37:16 PM
Thanks for the compliments.  I rather like how it turned out.  The original is the yellow fuse model.

Mark
Title: Re: TD-4
Post by: Dan McEntee on November 07, 2016, 04:27:01 PM
   I have a TD-4 hanging in my building room, and your replica looks very good. How did you make the wing? is it foam, have an airfoil, or is it  under cambered like the original?
   Type at you later,
    Dan McEntee
Title: Re: TD-4
Post by: Tim Wescott on November 07, 2016, 04:39:38 PM
Isn't it awfully nose heavy?
Title: Re: TD-4
Post by: Mark Mc on November 11, 2016, 01:02:16 AM
Tim,

It’s not too nose heavy.  Without any tail weight, it balances out at about the 10% chord line.  I added about 9 grams of weight to bring the balance back to around 17%.


Dan,

I thought long and hard on the wing.  I went through about three iterations of an undercambered wing, but wasn’t too happy with any of them.  So I just wussed out and made a built up sheet wing with solid tip blocks.  Still lighter than the original.


(https://s5.postimg.org/xpb0r4mvr/DSCN4882.jpg) (https://postimage.org) (https://postimage.org/)
(https://s5.postimg.org/srxg60kwn/DSCN4883.jpg) (https://postimage.org) (https://postimage.org/)
(https://s5.postimg.org/6c5twdgbb/DSCN4897.jpg) (https://postimage.org) (https://postimage.org/)
(https://s5.postimg.org/99758sjpz/DSCN4909.jpg) (https://postimage.org) (https://postimage.org/)


If you’re interested, the build thread for it is here: http://www.coxengineforum.com/t6595-giving-new-life-to-a-classic


Mark
Title: Re: TD-4
Post by: RknRusty on November 11, 2016, 09:50:32 PM
It is well worth clicking the link in Mark's post above. It's a really interesting build thread starting with pencil and paper all the way to the finished product. Pretty amazing job. I'm hoping there'll be a flight report and video coming soon.
Thanks, Mark. Well done.
Rusty
Title: Re: TD-4
Post by: Mark Mc on November 12, 2016, 08:36:22 PM
It is well worth clicking the link in Mark's post above. It's a really interesting build thread starting with pencil and paper all the way to the finished product. Pretty amazing job. I'm hoping there'll be a flight report and video coming soon.
Thanks, Mark. Well done.
Rusty

Hmmm... Maybe like this?


https://www.youtube.com/watch?v=B0SSYaRasM4&feature=youtu.be
Title: Re: TD-4
Post by: Chancey Chorney on November 12, 2016, 09:02:41 PM
Good video. Looks like it is a nice, fun little flier.
Title: Re: TD-4
Post by: john e. holliday on November 14, 2016, 10:13:53 AM
Looks like you are having too much fun.   Yes a Golden Bee tank will give longer runs but will also change your CG/control response.   Your 4th attempt in which you state the push rod came loose reminded me while I was laughing about a NATS Mouse Race in which John Ballard was a pilot.  They had made a pit stop and John was having control problems.  Seems the push rod was gone when he landed for another pit stop.  It was never found.

Your loops are looking good.  Now the loops the other way.   As the plane goes over the top and starting to go down, give down elevator control.   Don't change your mind once you start the outside loop.  As you get more confidence you can start stretching out the inverted flight .   Also you will be on your way to lazy 8's as some call them.   By the way little plane sure looks like fun.
Title: Re: TD-4
Post by: Mark Mc on November 16, 2016, 07:52:02 PM
While I was looking at my TD-4 replica flying in circles, I had an idea for another version. I spent a lot of time building the model I have since I wanted it to be scale. But I thought that it could be done in a much shorter span of time and built in a much easier fashion if you just wanted to do it as a semi-scale plane. From a distance it would still look and fly identical to the scale plane in stunt mode, just simpler and quicker to build. I could draw up a rough set of plans (i.e. pencil and paper) if there was interest in this.

Mark
Title: Re: TD-4
Post by: Greg Rodney on January 20, 2017, 06:12:53 PM
Beautiful, Beautiful workmanship!

Greg