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Old Mar 30, 2008, 08:25 PM
Editor - Flying Models
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Here is a technique I have been using for years to hold ribs for assembly of EZ-Bs and Mini-Sticks.

http://www.gryffinaero.com/models/ff...ribholder.html

Thayer
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Old Mar 31, 2008, 02:33 PM
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erich's Avatar
Holden , Massachusettes
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Thayer, clever idea, the rib holder. You got a real good web page, lotsa good stuff there. Looks like you mostly do scale stuff. Working on this semi-scale cabin gives me a little bit of an inkling what it takes to just build em, let alone make em fly. Nice work making that fleet.

And again back to the salt mine.

With the wing covering going on so well, just kept going and covered fin and stab too. The fin being flat was the easiest. Just needed to be careful and not get to much glue on either one. They're built pretty light, and don't need much glue, plus, it's probably a good idea to keep the weight down, towards the back of the plane. With the covering on, fin and stab together weigh .2 gr, seems pretty light to me. However, the wing weighs 1.2 gr, which makes up for the tail surfaces by being little on the heavy side. One of those good news / bad news deals.

erich
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Old Mar 31, 2008, 04:11 PM
Editor - Flying Models
United States, CT
Joined Aug 2003
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Erich,

Thanks for the kind words. That little block of wood really works well. I have several of them that I use to hold ribs while I work along. If you are working ona board you can pin to, you can pin down the block to really hold the rib while the glue dries.

I tend to like airplanes that look like real airplanes. It feeds the fantasy of getting in and going somewhere. Of course if you want absolute duration though, you need to give up that urge. I don't put much effort into detailing though. just enough to give a reasonable impression of the prototype when flying.

Thayer
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Old Apr 01, 2008, 01:09 AM
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Spent most of the evening making indoor tools. In an effort to bring my building out of the stone age. Hopefully these tools will, at least, take me into the bronze era. Got the idea for 2 of them from a John Barker article on PP building. And the one we've all seen a few frames back, by Thayer. Plus the most ingenious of all from Ray Harlan.

From the John Barker article: Made a jig to align the wing tubes onto motor stick. Have already used it, the thing works like a charm. Also made 2 wing stands with adjustable arms, to help when gluing wing posts to wing. Been using books for this. Got tired of lugging 4 volumes of "War and Peace" back and forth from the library.

The little gizzmo idea from Thayer: to hold ribs in place. Just finished making one of these and haven't tried it yet.

Ray Harlan's wing post maker was a little more complex: Ray has a description of this thing on his web site. Followed the directions pretty much, except for the springs. Not sure how heavy of a spring is needed. Will add those later. Have already made 6-8 round dowels out of square stock with it. They came out like they was store bought.

Also, from A2Z, got an applicator bottle and needle, to dispense glue mixed with solvent (ambroid and acetone in my case). Have been (heaven forgive me) using ambroid full strength, straight out of the tube. Not only does this add weight and make small messess. I end up wasting at least half of the tube of glue. Not sure of the mix of acetone to ambroid, but am starting with a 50/50 mix.

Should be able to crank out the planes, like an assembly line, now.

erich
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Last edited by erich; Apr 01, 2008 at 01:17 AM.
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Old Apr 01, 2008, 09:52 PM
more balsa please!
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Princeton, In
Joined Jul 2007
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erich,

I confess I was using my ambriod straigt also. But I did use the bottle from A2Z to limit how much. After reading your post I went to the hardware store tonight and picked up some Acetone. I was going to get finger nail polish remover from Walmart then read that it include a lot of other ingrediants. So I bought it at hardware store. I'm thinking 32oz of aceton should last through the build of the mini sticks at least.

Work has'nt been cooperating with the building. I did mix some ambroid and acetone using your 50/50 mix. I glued together a couple of "test" ribs that I cut for the mini. Seems to be strong enough. I looked for a few minutes on correct mixing amounts, but did'nt see anything. I'm sure it will help with keeping things light.

I was thinking, like everyone else when they start building "rubber band powered airplanes, nice simple, easy. Wow, was I wrong, lots to learn. But, I"m loving it. Just wish I had more time. Hopefully within the next few days I'll get this wing done.

Darvin
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Old Apr 01, 2008, 10:24 PM
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Darvin

We seem to be going through the same learning stages. Have a 32 oz can of acetone, that's lasted me, about 5 years now. The stuff seems to go a long way, even though, I use it 4-5 times a day. Mostly for clean up. Yea something always seems to get in the way of important stuff (building). With me it's money (lack of). Been only working part time, so have to be real stingy when getting stuff, for indoor. Anywho good to see the progress you ARE making. Have used some of the tools I just made, they really make life a little easier. Still haven't had a chance to use glue gun (syringe). Glad to hear, a 50/50 mix seems strong enough. That mixture is just a guess on my part. Well got some wheels to build, so I better get to it.

erich
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Old Apr 02, 2008, 03:10 AM
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Before tackling the job of putting together the fuselage sides, decided to torture myself some, and make the spoked wheels described in the Book. Used 1/32" soft, stick for the rims. Soaked em in hot water then wound a few times around a 1" dia. aluminum tube. Baked for 20 min at 250 deg (or till golden brown). On taking them out of the oven, discovered the wood was stuck onto the tube, but good. Yep the aluminum tube was painted (hey it was the only thing I could find, that size). So tried again, this time wrapping some wax paper around tube and then wrapping a few turns of wood. Came out much better. Did this a number of times to try and eliminate the kinks, but no luck. Finally decided the curve is to abrupt, to keep the wood from kinking. So used the rims as is, kinks and all. Made the hub from some 1/8" rd stock I had made. Pinned that to board with .015 wire. Propped up the rim so's it would be in middle of hub. That sounds easy, but with stuff this small that's not. Now for the hard part getting the spokes glued to rim. The kinks actually helped here, found the spokes stayed in place better if added em, right at a kink. Anyway my first attempt looked a little lop sided. Made 2 more wheels, this time using a 120 deg paper template to set the spacing. Had figured I could eyeball this on the first wheel, NOPE. Am more satisfied with my second and third attempt, although they still could be a little better. Wish I coulda made em without kinking the rims.

erich
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Last edited by erich; Apr 02, 2008 at 11:52 AM.
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Old Apr 02, 2008, 04:31 AM
Torn 'twixt buildin' and flyin
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When I was building indoor models, I always hated "sliced" ribs. On some of the more sharply curved rib leading edges, I would sometimes run into the problem of having the rib split along the grain and shearing if the leading edge hit something (like a basketball backboard). I started "forming" rib sheets for indoor models. I soak a piece of whatever thickness wood is required, and tape it down to a block carved to the rib curvature I wanted. This way the grain runs straight through the entire length of the rib. When you have the pre-formed "bent rib blank" ready, you can sand the proper angle into the leading and trailing edges of the sheet for a better joint. I use a Master Airscrew stripper, cutting against the inside of the "curve", rocking it to keep the part being cut flat as the stripper passes it. (I hope that's clear.) For extra lightness, if you have made them longer than you will need, which you should always do, you can glue the leading and trailing edges to a stick with all the "sliced" ribs turned on their sides and sand even thinner.

Since most indoor models only require a few ribs on a wing, a 1/2-inch to 1-inch wide block is usually more than wide enough to form a blank to cut enough ribs for more than one model.
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Old Apr 02, 2008, 04:52 AM
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Thanks for posting, Nightowl. I actually understood most everything you wrote. Even the part about rocking the the curved sheet to keep it against board. Just have one question. What would be the point of sanding the proper angle to LE and TE (to mate well, with LE and TE spars am assuming) of curved blank. IF: one should always make them longer, aren't the pre-sanded LE and TE angles going to get cut away, when trimming for proper length? Even more so if you glue em to a stick to thin them out. Am I missing something there?


erich
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Old Apr 02, 2008, 08:16 AM
slow but inefficient
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Riverhead NY USA
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Wheels: Laminate out of 1/64th - no kinks.
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Old Apr 02, 2008, 11:56 AM
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"1/64"! Say your kidding. Made a mistake, used 1/32" sq. stick, not 1/16. So what do I gotta do, sand down a 1/32 pieces to 1/64? If so isn't that going to weaken it to much? Or can that size be bought?

erich
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Old Apr 02, 2008, 12:09 PM
Torn 'twixt buildin' and flyin
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Quote:
Originally Posted by erich
Thanks for posting, Nightowl. I actually understood most everything you wrote. Even the part about rocking the the curved sheet to keep it against board. Just have one question. What would be the point of sanding the proper angle to LE and TE (to mate well, with LE and TE spars am assuming) of curved blank. IF: one should always make them longer, aren't the pre-sanded LE and TE angles going to get cut away, when trimming for proper length? Even more so if you glue em to a stick to thin them out. Am I missing something there?


erich
Yeah, that does sound kind of like wasted effort the way I said it, didn't it? I was kind of mixing methods in my earlier post.

If you cut them overlong (which actually is the best thing to do), the leading edge of the blank can be sanded at the proper angle so that you have the best fit against the LE spar. Then you lay each rib on it's side on the plan at the proper station, and cut with a VERY SHARP thin blade along the line of the TE spar. I use blades from disposable razors for this.

Then, too, if you are one who doesn't like that little step of trimming to fit, you can cut them to exactly the length you want in the end so the sanded angles get the best fits against the LE and TE.

Sometimes, with say Mini-Sticks or EZBs or F1D, it can be easier to strip them a wee bit thicker than you want in the end. Cutting them too thin with the stripper can cause them to be uneven if the blade wanders in the grain a little. If you want to sand them thinner, and you have sanded in the angle on the front and rear edges, then you can lay them on their sides and make a "sheet" of ribs from them. You glue a stick along each edge, and you can sand the whole thing (carefully!) a little thinner. You can do this sanding carefully even across the grain, IF the front and rear ends are glued against the sticks tightly and you use very fine paper, without them fanning and/or breaking several ribs. This takes practice. Then you use a straight edge and cut away the bracing sticks and you're left with the proper angles still for good joints. You can use this method to even make the ribs tapered in thickness from front to rear.

When you're building 1.2-gram F1Ds, or sub-gram EZBs or Mini-Sticks, tapering everywhere you can use a little less weight as the stress goes down is the norm. The motor stick is tapered from the CG to the ends, leading and trailing edges and spars are tapered, and trailing edges are thinner than leading edges on wings, stabs, and rudders. The guys who are winning in these events aren't whipping a model out in an evening.
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Old Apr 02, 2008, 12:41 PM
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Have been doing what you state in paragraph 2. Don't mind the trimming of TE. Does this proccess of using a molded rib blank, save weight? Or is it mostly to make a stronger rib? When you sand the ribs to make em thinner, or tapered, do you afterwards soak them in water (to firm them up some)? Appreciate you taking the time, a lot of the stuff you have to say, seems....very useful.

Was kidding about cranking em out on an assembly line. At heart ....I'm a clown. Have built about 6 (ezbs and PP) most, have taken about a week. Did, make a mini, in a day awhile back, but certainly not to compete. Thanks again.

erich
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Old Apr 02, 2008, 03:00 PM
Torn 'twixt buildin' and flyin
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I haven't build indoor models in some years now, due to a change in my location and no indoor flying sites close to me anymore. My most successful models were Mini-Sticks, where I did use the above methods. I think my first 7-minute EZB weighed 1.3 grams, if I remember correctly. (I no longer have my flight logs.)

The formed rib method rather than slicing partly "across" the grain (by the way, clean, clear, light A-grain sheet should be used for this method) doesn't save any weight over a rib cut to the same dimensions from similar-weight wood. Same wood volume equals same weight. But it is possible to cut smaller ribs since they are stronger, thus resulting in weight savings. For instance, the "tail" of the blank can be sanded thinner in thickness while it is whole, whiich is much, much easier than trying to taper over-thick ribs once the wing is framed. It can even be sanded asymmetrically so you can select ribs accordingly, thicker-ended ones for the center rib, moving out to thinner ones toward the tips. However, remember, we are talking about ribs that may be .032 in depth by .020 in thickness at the leading edge center to .020 in depth by .015 in thickness at the traliing edge tip for an EZB rib, against a leading edge that will taper from .032 at the center to .020 at the tip, and a trailing edge tapering from .020 at the center to .015 at the tip. Shaving milligrams of weight off is how you get from 0.9 grams to 0.7 grams.

It was my own experience that taught me that learning the techniques to save very, very minimal amounts of weight everywhere I can from the beginning allowed me to learn the right techniques while working with wood that was heavy enough for my first ham-handed attempts. Building with 7# balsa at first while learning the techniques lets you refine that, and then you know HOW to handle that 3.8# 1/50 x 1 x 12 sheet you buy later from a specialty indoor supplier. Then you only have to teach yourself to work with the lighter wood, rather than learning to work with lighter wood in a different way at the same time.
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Old Apr 02, 2008, 04:39 PM
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Nightowl

Can understand the need for a place to fly. Had nothing around here till I started to really look into it. Got lucky there's a College AND an indoor club which have flying sites. So have at least 2 indoor sites one 50 mi and the other 30. How lucky can one get, even know of an indoor electric bunch that fly in a big high school gym, not more than 15 mi from my place. Kinda neat flying real slow amongst all the heli's and pattern planes. Looks like I'll be flying 3 times a month, if I go to all the meets. Compared to rc/gliders, which I could fly anytime, it's not a lot. But by indoor standards it's probably, not bad at all. Thanks again for all the great info. Probably won't use most of it for awhile, but as I get better, will be able to use some, if not all, of it.


green air
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