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Old Dec 31, 2008, 08:52 AM
Two left thumbs
Muncie, IN
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I've not said much either, but am very much enjoying this build! I'm wondering about the landing gear mount: I see no vertical support for it. Is it intended to come off in a hard landing, or are you good enough at flying that you will not have to worry about that?

Geoff
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Old Dec 31, 2008, 10:30 AM
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Thanks KP,

I am accustomed to working under primitive conditions I used to produce my own glue to use on FF contest models and I still use it sometimes - something like Ambroid. That is knowledge left from decades ago, when we had no alternatives.

Now I use the homemade glue to attach paper templates on the balsa; when the job is finished acetone softens the glue and the paper is removed. Some glue remains inevitably, however. Sometimes I transfer the patterns to the balsa by applying dope thinner on the back of the laser output. For the cases when there are two identical parts to be cut, laser ink goes to the first one, paper template to the second; because the solvent transfer works one time only.

I also have a Sherline CNC mill which is hardly primitive, but I could not get it running yet. Stepper motor controllers were homemade.

I wish I had more time so the construction could go faster.. There is lots of detailed work waiting ahead..

Bulent
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Old Dec 31, 2008, 10:38 AM
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Geoff,

The 2 mm LG legs are in the shape of a horizontal U's where they go in the fuselage, with 2 mm plywood filling in between, they slide in from the sides. There is also a 1mm thick strut holder plate placed right over the leg, so the total thickness is 3mm, the slot thickness on the box. After inserting these from the sides, four screws fix them in place. They are removable for repairs or modifications. Probably they could be removed for transport as well, if the tail was made removable. Now the tail is wider than the LG and strut support, so there is not much logic in that.

I am trying to put in a sketch of the LG.

Edit: I have just understood your point after rereading your post in detail, so the above explanation may be unnecessary I beleive that setup is strong enough for a 600 gr. model. The strips on the fuselage sides it is glued between have supports above them. Other than that, one of the formers (the one on the front of the door) sits directly on this box. Maybe the rear end of the box may a bit stressed, you might have a point there.. I may think of putting in triangular supports there. Thanks for bringing up the issue..

Bulent
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Old Dec 31, 2008, 11:09 AM
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Bulent,

Well, no doubt, you do have talent working under primitive conditions. I may be wrong when I say this(I doubt it), but I don't think that many people make their own glue. When I mention this...it's a comment. You are also right when you say that the Sherline CNC mill isn't the least bit primitive. Man, that thing must be handy...well, only if it's running, of course. I haven't done any laminations for pieces yet, but I see it in my very near future.

KP
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Old Dec 31, 2008, 12:09 PM
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Thanks KP,

Although it may seem complicated, producing cellulosic glue is quite easy - if you can find the nitrocellulose, that is. It is getting as scarce as hens teeth. Older combs, eyeglass frames, etc. were made of that stuff; now it is hard to find. That is the kind of plastic that burns fast and clean, with no smoke and little residue. The best example is ping pong (table tennis) balls. Now that is the only source I can find; and that would make a very white glue, seeing its condition during glue production would be difficult, and it would not (does not) look good on the balsa. I have some older plastic and some ready made glue from older years. I apply it using a disposable syringe, the type with no rubber on the plunger.

To prepare the glue, you just chop the plastic up and put it in a clear glass bottle with pure acetone. On the first few days it is jelly like, but after some shaking, mixing, changing position of the bottle, etc. it starts getting more fluidic. Consistency is adjusted by adding acetone, so it can be made very thin and light. I use no other additive.

The Sherline can be operated manually now in HHC mode (Human Hand Control), but I should start using it as a CNC tool because this model has lots of parts to be cut from FR4 PCB sheet. Most probably the model will not get finished by the end of May and I will be dismissed from the contest so I might as well try that now - I was reluctant to spend time on that.

Bulent
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Old Dec 31, 2008, 03:23 PM
Two left thumbs
Muncie, IN
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Thanks for the fine explanations, Bulent. As for sources of nitrocellulose, how about old movie film or old canon powder? Of course, if you use the latter, let the authorities know ahead of time so you don't get arrested, then you would NOT get done on time!

Geoff
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Old Dec 31, 2008, 04:09 PM
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Bulent,

Yes, thank you for the explanations. I'm all ears to learn. So, the more the better.

The way that you make glue is something else. If their was nitrocellulose around to more people easier than it currently is, I'm sure that more people would take the opportunity. I know that I would. I think that being able to save a little extra money (for other RC stuff, of course) and controlling your end result would appeal to many.

KP
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Old Dec 31, 2008, 04:41 PM
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kp, you don't want to be messing around with nitrocellulose (also known as gun cotton) unless you really know what you're doing. It is/was a key ingredient in high explosives. That's probably the reason that it is no longer readily available.

Tony
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Old Dec 31, 2008, 09:09 PM
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Tpfing,

Don't worry. I didn't plan to because it can't be found really. Post #81 got me thinkin' what you are, too. I think that for now I'll stick with Titebond and Elmers Wood Glue.

KP
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Old Jan 02, 2009, 05:10 AM
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Hey,

It is wise to be careful, but nitrocelluse by itself is only as dangerous as ping pong balls - that is almost 100% nitrocellulose. Of course it burns dangerously; that must be why movie films were modified, running along high power lamps or arc lamps in old movie projectors - must be a deadly combination.

I used to experiment on solid rocket propellant mixtures at home when I was young; even burned down my mother's kitchen curtain - that was a good lesson. My rocket(s) flew only once , and broke down some other house's window - another bad lesson which ended all experimentation

Let's stop dangerous conversations. Here are some developments from yesterday. The cabin floor , door sills, and a fuselage reinforcement have been installed, as photos show. The reinforcement is just there to hold the fuselage sides fixed, there is no other function - well, one end is useful for holding a bulkhead in place.. I am gluing the plywood wing root support in one photo.

I have started working on the curved wing and tail tips, or rather their jigs. I need to get the vertical tail ready to get the fuselage finished.

Despite all those holes, the fuselage at this stage - without the front and the rear end still untouched - is around 75 grams, not as light as I would like it to be. I guess only the stringers will add around 30-40 grams.

Bulent
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Old Jan 02, 2009, 05:20 AM
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Geoff,

In further reponse to your post #76, related with the LG setup, I remembered that the load on the landing gear is transferred directly to the fuselage sides, so the fixing of the LG box fixture is not so important, as long as it stays in one piece. I have applied fiberglass cloth on the vertical edges - front and rear - to make sure it is strong.

The following picture may prove the above, although it is not very clear. the fuselage side strips are white, wing strut holder is red, LG wires green. You can see that the wing strut holder is directly between the LG and the fuselage sides, so it will transfer the load - so there should be no problem due to hard landings, if the fuselage is in one piece

Bulent
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Old Jan 02, 2009, 08:46 AM
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Bulent, I am truly fascinated with your work. I had forgotten so much about building with stick structures that I am starting to relearn. I am currently building Pat Tritle's Aeronca Champ. I am finding that old eyes can make it really difficult to accurately line up parts for glueing. However, for the last five days, I have been working more or less continuously, with breaks for glue to set and watch a little TV, and they have been extremely relaxing and enjoyable. The Fairchild is on my 'to build' list for 'someday'. My personal preference though is the round engine version rather than the Ranger. You're doing beautiful work.

Tony
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Old Jan 02, 2009, 12:22 PM
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Thanks Tony,

I am sure you will have a good time with the Tritle Aeronca. I had scratch built a Tritle design before this model, the 48" Stinson Voyager. Maybe some of his techniques have been incorporated into my system The Stinson flies perfectly, real slow and also fast enough when forced. If it had ailerons it could do all maneuvers in the book. Even with the rudder I can work out some of those. Of course rolls are quite barrelly, so roll maneuvers leave much to be desired - well that means most them, huh ?

My eyesight is failing also, I use those magnifier fluorescent lamps on all tables and do critical work under those.

Five days continuous work periods can be quite fruitful. I had that chance a few weeks ago, and most of what is seen on the Fairchild was a result of that. Maybe I can have more time by the summer, because I may get retired by then. I can have a few months free time before taking a new job - which has to be done in this country, as the retirement wage is funny, 20% of my present wage at most..

The Karlstrom 3 view shows the radial one as well, maybe you can modify my plan - the radial nose should be much easier than the inline.. You could need a dummy engine, though, and that could limit the scale of the model unless you would be willing to do the engine from scratch.

Bulent
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Old Jan 05, 2009, 07:01 AM
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I could not work much on the model, because I can not stay at home; and when I do I can not work efficiently. The reason is that I have run out of natural gas for the heater, and it can not be bought due to long cues. We buy gas using a chip card that has to be taken to a point of sale. Work being interrupted for such a foolish reason can be an issue only in this funny country, I guess.

I managed to get the plywood wing root support glued on the fuselage, and I have cut the ribs for the vertical tail - that is all, except for cutting of the rudder lamination jig and some Autocad editing to get the model more scale like. Autocad work time on this file has reached 400 hours or so.. Actually it is more, because I have been working on two files since a few weeks - one that is printable (single layer and two pages) and one that is more legible due to use of different layers. I transfer changes from one to the other immediately, not to lose track of them.

Bulent
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Old Jan 06, 2009, 05:15 AM
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I could not do much yesterday, but the house is heating up - natural gas was finally bought. Temperature rose up to 15 C, starting from 8C. I was getting used to going around the house in winter clothing

I am attaching a photo showing the plywood wing root reinforcements. Two of these added around 5 grams, so maybe I should have used 0.8 mm plywood instead of 1 mm. If one is not careful at every step, the result can be seriously overweight.

Wing joiners will be carbon tube, with 4mm outer 2 mm inner dia. (3 mm inner diameter - if I can get some), they will ride in 5 mm K&S aluminum tubing. The smaller hole in the middle will be enlarged for a wing fixing screw - probably a thumbscrew will be used here, tightened from inside the cabin.

Bulent
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