TD-3 balsa replica build

duaneh Sat Aug 19, 2023 6:24 pm

Bob's recent threads on the Cox TD-1 and TD-3 got me interested in building one or both of them in balsa. I don't have access to a TD-1, but my LHS has a TD-3 in the case. I was able to borrow it to get the needed measurements for a replica.
No beauty queen, it's been "rode hard and put away wet". No matter, it is good for what I need. My first impressions were that it is smaller than expected, and very light weight.

I was surprised by how light it is. I don't think I will be able to equal 5.2 oz., let alone beat it.

Since I retired from my retirement job this year, I no longer have access to a CAD system. Pencil & paper still works, but is tedious by comparison.

Wing area works out to only 64 sq. in., so it really needs to be light.

Here's the pieces I have so far. Yes, it's going to be a 'hollow log'. The fuse shape doesn't lend itself to sheet construction, and I didn't want to loft formers or plank them. I'm not going to replicate the corrugations in the wing, but I did set the rib spacing to match their locations.

rsv1cox Sat Aug 19, 2023 7:02 pm

Wow, great project and I'm eager to see how it turns out. Just anchor that bell crank well. Smile

Got pictures of the top and bottom wing showing the pivot point?

And my scratch built P-38 was all hollow log, engine booms and pilots module.

Bob

GallopingGhostler Sat Aug 19, 2023 8:04 pm

Thanks for the measurements, @duaneh and your construction in balsa as a duplicate is spot on. Thumbs Up

By the time you are done, I can see where your cloning will perform very much like the original TD-3 did, but with better maintainability. 64 square inch wing area is a little bit smaller than I would think, but with such a thick wing section should be a good performer under reed power.

Your methodology is a good one for having the same feel without possibly crashing and permanently ruining a historic specimen. Beer Cheers

rdw777 Sun Aug 20, 2023 4:07 pm

Always first class work from duaneh….Will be watching this one…. TD-3 has some cool lines…. Thumbs Up

duaneh Sun Aug 20, 2023 11:22 pm

Made a little progress today. First, separated and hollowed the log.
Fun facts: The basic log was 2 x 2-7/8 x 13-1/4" and weighed 140 grams. After band sawing the profile and plan views, 62 grams. After contouring the outside to shape, 51 grams. After hollowing, just 19 grams. Rather a wasteful process, as 86% of the material ended up in the bin. It's easy to understand why the manufacturers moved away from this technique.

With that done, it was time to install the controls and glue the wing & stab to the fuse top half. Got to make sure the pushrod & control horn are right at this point, because once we glue on the fuse bottom, they are never to be seen again.

getback Mon Aug 21, 2023 6:04 am

Wow Duaneh It looking really Good , I missed this thread but glad I found it . I admire your skills all your cuts are so precise and fit is perfect ! What was your former job U mention the CAD . That is alot of waste in the hollow logging Popcorn

rsv1cox Mon Aug 21, 2023 6:40 pm

Beautiful start and great work. Control line with leadouts contained within the wing exiting under the wing like the original. Nice! Planked probably or monokote type. Early Space Bug Jr. or later Babe Bee............yeah, too many questions......... Smile

Do you have a paint scheme in mind? Factory or your own design? I haven't seen your local Hobby Shops white, only red/white checkerboard and my involved colorful design.

I see you will have red worked in there somewhere.

Bob

**944_Jim** Mon Aug 21, 2023 9:41 pm

D-D-D-Damn, Duanne...

Hubba-Hubba-Hubba!

duaneh Mon Aug 21, 2023 10:24 pm

Getting closer, the basic construction is done. Got the fuse closed up, and glued on the rudder. Also made the gear. Cox was really going for low cost on this one, even the gear is undersize. Made from .051 dia. wire, instead of the usual .062. I found a piece of .055, close enough for me.

I don't have a SB Jr., and have never bought a Babe Bee on purpose. But was pretty sure I had a few around that came with other deals. Well, when I dumped out the Cox box, there were NINE BB's. Do they breed or something? By swapping parts around, I put together one with "Thimble Drome" on the tank, a narrow neck case, thin wall cyl., and large knob needle valve. I think this is representative of the ones that came on late TD-3's.

Covering is next. The scheme I picked out is like Bob's, but with the red & yellow reversed. Here is a pic grabbed from the net.

rdw777 Tue Aug 22, 2023 1:06 pm

Excellent work, Not only scratch built but hand drafted from an original…. Talents!!! Very Happy

GallopingGhostler Tue Aug 22, 2023 1:10 pm

I have to agree with you, Robert. Duane has done an outstanding job in recreating the TD-3 in balsa. Once covered, it will be definitely recognized as a TD-3. I also surmise that it will fly as well as or even better than the TD-3.

rsv1cox Tue Aug 22, 2023 2:21 pm

It will be interesting Duane to see how close your balsa model compares to this with the Babe Bee rather than the SB Jr. which I believe is lighter. Note to me....weigh both the SB Jr and the BB.

Mike1484 Wed Aug 23, 2023 7:10 am

Nice build Duaneh ! Good to see somebody still cutting wood and building. The Tee Dee 3 was my first Cox plastic flying model. It was my graduation present from my mom for passing 4th grade. Now I'm going on 75 and I never thought that somebody would actually build one from balsa. Your building skills are outstanding.

Mike1484

duaneh Wed Aug 23, 2023 7:46 pm

Finished the covering today. With all the compound curves, it was surprisingly hard to cover. In person, there are flaws, but the camera is my friend.

I enlarged the tailskid, and added a hole for my pin stooge.

A question for Bob, rsv1cox. Is the registration number repeated on the bottom? I couldn't find any photos showing the bottom.

The good news is the weight, even with a Babe Bee, slightly beat the factory.

The bad news is it is very nose heavy, and will need 1/2 oz. in the tail to balance at the same point as the original.

GallopingGhostler Wed Aug 23, 2023 10:34 pm

Looks very good, Duane, I definitely see a TD-3 there. Just curious, but did Cox shorten the nose on the TD-3's that used a Cox Babe Bee to balance it better? Or, did they continue to sell as-is? Or, weight the tail to balance?

I guess the other option would be to install a Space-Bug Jr. on it.

Mark Boesen Wed Aug 23, 2023 10:46 pm

Wow, very impressive, it looks great! At this point, in for a penny, in for a pound. I agree, I'd find a red Space Bug Jr. to help with the CG.

I don't think there were any CG corrections when they made 'em with the Babe Bee.

**944_Jim** Wed Aug 23, 2023 10:54 pm

*Is it live, or is it Memorex?"

Practically indistinguishable from the original. Unbelievable!

GallopingGhostler Thu Aug 24, 2023 12:11 am

Mark Boesen wrote:Wow, very impressive, it looks great! At this point, in for a penny, in for a pound. I agree, I'd find a red Space Bug Jr. to help with the CG.

Even a yellow or blue S-B Jr. would still accent it nicely, because of the other colors Duane has decorated it with.

Mark Boesen wrote:I don't think there were any CG corrections when they made 'em with the Babe Bee.

Thanks for clarifying, Mark. Even though a little nose heavy, they probably still were nice sport flyers.

getback Thu Aug 24, 2023 6:35 am

WOW Looks GRRREAT ! The covering/paint brings out the curves nicely . I would think they where made nose heavy to make them not so jumpy in air ? Maybe Bob can clarify on this Very Happy

rsv1cox Thu Aug 24, 2023 7:06 am

No kidding, you knocked out that beautiful thing this quick!!!!!!!!!!!!!!!!! Takes a lot to impress this old geezer but I'm blown away. Beautiful job!

Yes, nose heavy. Mine balances right at the leading edge of the wing. Go even a quarter inch back and it's a lawn dart even with the SB Jr.

Am I misreading something? 4.65 oz vs. 5.0 oz

duaneh Thu Aug 24, 2023 7:37 am

Thanks for the picture, Bob! I cut 2 sets of letters, but didn't put them on the bottom because I wasn't sure. Can do that now. My comment on the weight was in reference to the sample I have on hand. It weighs 5.2 oz.

Yours is very light at 4.65 oz.

I'm hesitant to put a Space Bug Jr. on this one. It is going to get flown. The airframe can be easily repaired or replaced, but they aren't making Space Bugs any more.

rsv1cox Thu Aug 24, 2023 8:06 am

Must be all that epoxy in the nose. Smile

Good excuse to build another one. The bolt patten is the same but you would have to drill a hole in the firewall. I do love that plane. What is the covering? Were I fifty years younger with steady hands I would be hitting you up for plans.

duaneh Thu Aug 24, 2023 8:35 am

The base yellow & red is Econokote. A budget low-temp film that Top Flite used to sell. It goes around compound curves easier than Monokote, which was helpful on this one. The trim colors are Monokote.

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