UStik

It's here! All is fine, the sender did an outstanding job. It has been exactly two weeks now. Delivered Nov. 20, international dispatch from Chicago Nov. 27. The day before yesterday it arrived at the local customs office, yesterday I had a notification in my mailbox, and today I picked it up. Had to pay import sales tax but no customs duty since it's below a certain limit. Not too bad!!!

For those who don't know/remember: This is a follow-up to the threads started by maxpower1954 where he described how he built and test-flew his Babcock Aeronca.
[link=http://www.rcuniverse.com/forum/m_9024665/tm.htm]ARF 1958 style - the Babcock Aeronca[/link]
[link=http://www.rcuniverse.com/forum/m_9086018/tm.htm]Babcock Aeronca ready for maiden[/link]
There were some issues in the flight behavior we all together were not able to explain. That's why I acquired my own copy of this vintage ARF to experiment myself.

Pictures will come when I have better daylight for photos.

UStik

Well, can't wait. Not much daylight today, rainy dark weather here, now "sunset", but enough for an overview.

Huge corrugated box, much paper and plastic padding, and such a tiny box inside. Obviously, it travelled like in Abraham's bosom. No damage to the box except what was there before, but not at all bad. Down side is that the 1:5 Husky is now on the backburner again. That "buy today, fly tomorrow" just isn't true, at least not in this case.

UStik

The box, top and around.

UStik

Opening the box is always the most exciting part of the build.

Looks pretty good, except there's a small dent in the left wing blank and a crack in the right wing blank, but looks repairable. Seems all parts are there, bud didn't really check yet, especially the small plastic bag. The wheel hubs are inside but no rubber tires. No big deal, maxpower said they were too heavy, anyway. Modern light wheels will do fine.

UStik

The plan. Finished for today...

By the way, Russ, did you use contact cement? It's praised on the leaflet in the box (showing the Tri Pacer) as the crucial invention making this kind of construction possible. Do you - or anybody else - actually know what kind of plastic the Aeronca is made of? Would be really nice to know.

ggeezer

I used to sell these kits many years ago and if memory serves me, I'm pretty sure that the plastic is High Impact Polystyrene. Do this test on a piece of scrap, put a drop of lacquer thinner or nail polish remover on the plastic, if after a short time, it has started to dissolve the plastic, then it is Polystyrene. If this is the case, then toughened CA is a good glue. If the solvent test doesn't effect the plastic, then contact cement is the best glue. Regular CA is probably too brittle whereas the contact cement is shock-proof.

maxpower1954

Hi UStik, glad you got the Aeronca in good shape.

I tried every glue I could think of on scrap from the kit. Regular plastic model liquid cement didn't touch it. MEK and acetone was too much. The problem with contact cement is you basically get one shot to get it right, and it's messy as well. I got the best results from using a high quality medium CA (and believe me, I'm not a fan of CA) but it worked out very well and has held the Aeronca together during my unplanned "arrival" testing.

I'll try to post some photos I took and some building experiences I had this weekend. Russ Farris

UStik

That's comprehensive information, many thanks to both of you!

Here's my arsenal of various cements. Today I visited the LHS and met a fellow modeler who knows a lot about glues. He and the owner recommended the green tube as a super glue. Turns out to be sort of CA but paste-like and with 10 minutes conditioning time. Maybe that's toughened CA? But they said I should try regular medium CA (the small bottle) as well since it won't get brittle if activator (the spray can) is used, either before applying the CA or after.

The two bigger tubes is what I always have. The yellow one is our famous UHU universal glue which bonds nearly everything but stays rather soft and elastic. The red-white-yellow one is the contact cement of another popular brand. I agree that it's messy and only one shot is too hard. And I'm not a fan of CA either, in fact I'm already sensitized (allergic). Still one of these glues may be the best one in this case and they will be tested tomorrow.

I didn't do the dissolving test, but I just tried Revell plastic model cement. Believe it or not, it works! It doesn't seem to dissolve the plastic but on the other hand the two glued scrap pieces don't get apart. All I can do is cut through the bonding with a knife, but it's like cutting through the plastic. I well believe that it's polystyrene, a bit harder than that used for plastic models, more like that used for blister packaging. (Is that High Impact Polystyrene?) Maybe that's what inspired Babcock to design these models.

Anyway, the Revell cement is my hot candidate for now, even if I'll also test the CA glues and might even try 5-minute epoxi. The warnings on the CA tube are quite daunting, but I'm allergic to epoxi and the Revell cement as well. But white wood glue is not applicable here... []

UStik

Today I inspected the small-parts bag. Some parts are missing, but no problem. One hub half is missing and both tires. Some bolts and bushings seem to be missing as well, but I can get some at any time. The tiny bushings and pins just look so cute. I don't need the C/L lever, and I won't use the small piece of fabric to cut hinge strips. It's just so neat.

Maybe I will use the tail wheel and the enclosed wire for the tail landing gear. For the main landing gear I bought two very nice 1-3/4" Kavan light wheels. Russ, is that a suitable size or should the wheels be bigger?

While I was at it, I bought two servos HS-45HB with carbonite gear. Cheaper ones would have been enough but they weren't expensive either and I like them. I ordered the 2.4GHz conversion kit for my Multiplex transmitter and their smallest 2.4GHz receiver since the Aeronca shall be my first 2.4 model. Again not the cheapest solution, but it's a hobby after all and for fun.

maxpower1954

1.75 wheels should be fine - I used some from some Chinese ARF, almost 2.0 diameter. My kit was complete, but the wheels had ossified into a substance unknown to modern science and the hubs would not fit into the tire. Too heavy, anyway. The tires do have the Babcock name embrossed on them, which is kind of cool.

One concern with this model was the age of the plastic. I added birch dowels to the molded wing and landing gear pegs and balsa stock for the hinge mounting on the rudder and elevator. Finally,
I used medium balsa to fill the center part of the hat section main spar about eight inches out from the centerline. In practice, I haven't detected any real brittleness (UV does accelrate the process) and probably wouldn't bother with the spar and dowels on the next one (Tri-pacer, anyone?) Some pictures below to show the equipment placement I settled on. Russ Farris

Doc.316

Wow this is getting interesting...looking at the photos of the aeronca half it looks like there is some upthrust in the wing and tail...(basically putting down thrust in the engine without the plane looking funny). This is how the little jetco super cruiser that I just finished is set up also....It seems like a simple model...kinda cute actually. I am looking forward to your flight testing activities.

Steve

UStik

Yeah Doc, I think that's the usual way the models were set up back then. My parkflyer is the same. I even expect that the Aeronca should fly with positive stab incidence, again like my parkflyer. But to compare to the fuselage deck angle look at the attached picture. I did my best to align the rudder hinge line perpendicular to the brown seam in the floor using a notepad. Now the stab seems to have zero incidence ( sorry for the shadows, light comes from top and I can't turn the floor) and the "centerline" is just above the engine cowl. The lower edge of the cabin windows seems horizontal. Whatever that means. Please don't expect flight testing any soon, I intend to savor building, calculating, simulating, ...

Again very helpful, Russ. I think I'll exchange the wheels for slightly bigger ones. The original ones look bigger and the 1-3/4" wheels weigh only 0.2 oz each. The pictures answered all my questions about drive and radio installation as well as linkages. One question remains: Do you use only the right elevator half, as intended in the design, or have you both halves moving? That would require an additional elevator spar, made from balsa.

I had the same idea using dowels inside the pegs but didn't think of a spar reinforcement - good idea! But now you say it's not really needed I'll leave it out, the more so as I, too, can't detect any plastic brittleness. Today I checked the test bonding again after it had one day for hardening. Cutting further into the bonding revealed a small "bubble" but otherwise nothing but - well, plastic. The Revell cement seems to dissolve the material only a bit, but just enough to let both surfaces melt into each other. When cutting, the material felt rather ductile than brittle. (The engineers will know what I mean.)

So the Revell cement seems to be the way to go, fortunately not only to avoid using the unhealthy CA but also because it's adequate and works really well. Epoxi may be used to glue control horns and such.

UStik

Here we go. I did all what is recommended in the assembly instructions, especially familiarize myself with the relation of all parts to one another. I despised the recommendation to not use plastic cement, though. And I should have listened to the advice avoiding excessive amounts of cement. Boy, that stuff gets soft! But still my first "hot" test seems successful.

In opposition to the instructions, I started with the wing. The two spars were trimmed and glue-joined. The amount of dihedral was checked, and it is not equal on both sides. One of the spars just has the wrong dihedral angle formed in. I decided to prefer a gapless joint over the correct dihedral since stability is most important and equal amount of dihedral may be gotten by shimming.

Upper and lower center section were trimmed but not glued yet. The spar joint needs some time to harden. Maybe contact cement would be better yet. Well, at least I can't use the Revell cement for the other parts, or at least only very carefully. At a close look, the thin plastic is softened by the cement and really ripples. The test piece yesterday was thicker, no problem there.

UStik

It's tedious. Nevertheless the Babcock model is an early ARF. My ARF parkflyer just required glueing the wings and empennage and several wooden parts into the fuselage. Installation of drive and R/C is the same, anyway. It was not less work than here.

This blister construction requires meticulous trimming of all parts and precise alignment when glueing. The Babcock people did a great design and manufacturing job. All parts are well formed and fit perfectly, maybe surprising with this simple production technology. The parts are or at least become somewhat floppy when cut out of the vacuum formed blanks.

That makes them hard to handle and requires keen attention to proper alignment. Now I had an idea how to glue the wing center top to the spar. The center top was clamped to the building board to make its bottom straight flat. Problem was to straddle the spar sides so they touch the wing center cutout and are glued on there (as far as possible). I used two EPP packing chips inside the spar. That did the trick and even made the dihedral nearly equal on both sides.

I used the Revell plastic cement once again but applied sparingly. By the way, I found another glue in my plastic model building inventory. It's named Contacta but is nevertheless a polystyrene cement, just paste-like and in a tube. The further bondings have to be done with CA, but only at daylight and outdoors for health reasons.

I'm quite sure now that the material is polysterene since that was (and maybe still is) the most produced plastic and was already common in the 1950s, according to Wikipedia. There's nearly no information about the history of blister packing, only that it became common in the 1960s, but I believe it was known earlier.

maxpower1954

UStick, I did cut out both elevator halves and joined them with 1/16 music wire. I used thin CA type hinges as well. I engineered a steerable tail wheel; a flatted brass tube serves as the control arm for both rudder and tailwheel, soldered to the 1/16 wire joiner. It is a fiddly beast to put togehther... Russ Farris

UStik

Yes it is, well put! Now I'm pondering how I should build it. Right now I'm thinking I should build it stock, with a fixed tail wheel and only one elevator half. I could even try to use the pins through the provided salients as hinges. Since you have both halves moving we could compare the effect in flight. If I follow the strong advice in the assembly instructions not to glue in the stab but only snap it in, I could even later cut out the second elevator half and make it moving. Have to sleep on it...

maxpower1954

I went with the steerable tail wheel mainly because it kept the rudder linkage under the stab. Otherwise it has to go at an odd angle over the top, or somehow use the old torque rod arrangement, which I didn't want to do. I used both elevator sides as personal preference - I sure one side would work fine. Finally, the stab really does snap into place securely, but I added a short length of Scotch tape underneath on both sides anyway. Russ Farris

UStik

Weather was nice today and permitted glueing the wing center bottom outdoors on the roof-deck, trying the "super glue" CA. It's really good and foams so it will bridge any gaps. Still I applied some micro-balloon under the buckled spar center. 10 minutes conditioning time is no understatement and it was more than half an hour till the parts were no longer moveable. It takes forever (at least over night) to harden. All under current athmospheric conditions (temperature). Problem with this glue is not adjusting the parts but adjusting them long enough without attending the hardening process. Think I'll try contact cement next.

The wing blanks are trimmed now and waiting to be glued. Both wings had cracks at root and tip, but all but one are trimmed away, anyway. The spar and the center edge have to be glued to the flat bottom, then the wing top has to be bent over and glued to the bottom at the trailing edge and tip. Since contact cement is not fix as long as not pressed firmly, a bit adjustment should be possible. And it seems better to have the parts fixed instantly after adjusting.

UStik

That seems especially true for the stab/elevator since the parts are quite floppy but may be adjusted bit by bit, I mean fixed at a starting point and then adjusted and fixed bit by bit till the whole spar is glued.

I used my smallest drill bit to pre-drill the hinge pin holes. I really decided to build stock in the first place, only the right elevator half moving, using the salients and small pins as hinges. I'll even use the provided elevator control horn. All that may be changed later.

UStik

Just had a good chuckle when I disposed of the corrugated shipping box. Only now I noticed a small sticker which might explain something...

Doc.316

Looks like that airplane has more air miles that most models will ever have....and it isn't even built yet!
Steve

maxpower1954

It's almost a given it has more air miles than any Babcock Aeronca in history! Russ Farris

maxpower1954

UStik, when you bend the wing, tail ect over 180 degree during assembly, you might want to warm the plastic a little to make it easier and to preclude cracking. I used my trusty Monokote heat gun - CAREFULLY - keeping it moving and using an infared thermonter, worked out very well. Just a thought! Russ Farris

UStik

Again a very helpful thought, thanks! I was even already pondering about the bending problem, but without a result so far. I have a heat gun but one for removing old stain and I'm afraid it would be too coarse for this task. And I have no IR thermometer to check. I have a tiny "heat gun" (actually a gas-fired soldering iron with a heat-shrink bit) but if I'm done with one wing the place where I started would be cold again. My latest idea was to apply a bit of the liquid Revell cement to soften the material, and the groove giving the leading edge would be suited.

Anyway, I checked the wing center glued with the super glue, and as they promised it foamed and bridged gaps, and it hardened but didn't get brittle. A small part glued with medium CA and activator is not brittle as well. To try also contact cement, I bought another tube, a type which is nearly clear so excess glue will be hardly visible. I tried the elevator and it turned out quite well. It was by far not as messy as I thought and you may simply peel off excess glue. As promised in the instructions, the glue stays elastic while the shell construction makes the parts strong and rigid when put together. The elevator turned out not quite straight due to distortions in the parts. I overlooked a small bend when pressing the elevator halves, but I could have made it straight if I had paid attention. On the other hand, with the CA it needs a rig to fix the whole elevator until the glue has set.

Later:
I come to appreciate the contact cement. The elevator is completely clean now and I even managed to straighten out the small bend in the trailing edge. It works like heating a wing covered with film and bending it, just without heating. Now I'm curious if the glue will set any more or stay that elastic.

UStik

I does both, it sets more so the elevator will not distort unintended, but it's still a bit elastic what is good in case of an accident (impact). The elevator trailing edge is now straight while the hinge spar is a bit aslant what is due to the blank's form and internal stress (which seems to be quite substantial due to the ther****rming). It's slanted towards more up than down elevator and that's OK, though.

Now the elevator turned out so well I prepared the stab by glueing the main spar and the nose tip reinforcement with the contact cement. Will let it set before completing the stab by glueing the other half of the "shell".

Trimmed the elevator edges using my handy, 45 years old balsa plane. It's quite easy, no problem with the elastic glue. A bit sanding at the round edges and it's completely smooth.