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Author Topic: HLG Wing Shaping  (Read 9477 times)
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High Point
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« on: April 10, 2008, 11:19:47 PM »

I know that shaping a glider wing to the proper airfoil a plan calls for is important, but I need some direction please.

After reviewing some plans I have, most all call for a taper from the center break or the tip break out to the tip. Then the airfoil is shaped with the high point as a reference. My question is, how is this properly done; do you make a jig or is most done by sight?

Thanks for any help at all.

Curtis
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Dan G.
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« Reply #1 on: April 11, 2008, 02:00:38 AM »

Hi Curtis (fine aeronautical name),

I have always had difficulty in shaping hlg wings because of the change in several planes at the dihedral break, until I was introduced to "Supersweep" -- a derivative of Sweepette -- but I believe this applies as well to the Sweepette.

The taper of their wings is such that all of the rear camber, from tip to tip, is one constant angle -- a unique quality that doesn't apply to any other design I know of. It has to do with the taper (elliptical, I think) and that all of the taper is with the leading edge, the sweep of the max camber is elliptical, but the trailing edge is straight (except for the extreme tips). This means that with the trailing edge backed up to the edge of your sanding table (I use 1/4" glass), the sanding block is kept in one exact angular position while sliding (sanding) from tip to tip. This also means that if your layout is perfect, things will work out automatically. The max camber will work out to the right position all along the span, as will all the thickness from max camber aft. With very little checking, with only a small straight edge and a few different light sources (one overhead for working, one obliquely to check the surface, and one for back lighting to check thickness) you should be able to check the thicknesses anywhere from max camber aft with a micrometer and find everything within a couple of thousands of an inch to ideal.

Should you build a couple of these, you will discover the sort of serendipitous relationships of shapes which is comforting and expeditious -- it speeds things up because you quickly know if you're accurate or not and you can keep a constant check without having to measure. The serendipity isn't mysterious in this case -- it's the mathematics in the wonderful shape of that wing.

I don't measure thickness any more -- I don't have to -- I just build by hand and eye and it stays accurate.

Forgive me, if you were not looking for a one-design salesman, but I have the impression that these design qualities are not well enough known.

Dan G.

I seem to have taken something for granted -- all this description applies only if the airfoil has a sharp max camber and is flat to the T.E.. I did find this airfoil to be superior (casual testing only -- not rigorous) to the fully rounded ones.
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pedr01
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« Reply #2 on: April 11, 2008, 12:04:34 PM »

Loads and loads of Duck Tape. Don't know where I read it but it works a treat.

Mask off bit/tip you don't want to sand and line up against edge of board. Distance from edge determines end thickness. Keep on sanding until no more comes off, perfect.

If you don't want to sand the edge of your board, mask that off as well.

So for a wing that tapers from the centre line, you have to;

Mask one half, sand the other. Remove tape, mask the other half, sand. Mask airfoil front from high point, sand down to trailing edge, etc, etc, you get the point.

Dead easy, and very, very quick. Needless to say I like designs that have lots of straight lines.

 Grin Grin
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Dan G.
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« Reply #3 on: April 11, 2008, 08:28:07 PM »

Thanks pedr01 ... for pointing out the masking-off. I got so carried away about that curved wing, I completely neglected everything else, other than the rear camber. I wouldn't be able to produce a sharp max camber without masking. I've only used masking tape, and since it frayes easily, I'll be glad to try duck tape if it isn't too thick.

I'm a little embarrassed to say that I hadn't thought of taping-off at the dihedral joints of straight, multi-tapered wings -- which obviously would work. Actually, I haven't tried to build a straight-paneled winged hlg since I've been using tape and a sharp max camber. In fact, you could say that I've been locked-in to the same design for the past thirty-six years. Maybe I'm missing something. Is there anything you'd like to say, for instance, about straight-winged gliders that might tempt me?


Hi High Point ... are you looking for a description of a full process on shaping a wing?

Dan G.
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High Point
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« Reply #4 on: April 11, 2008, 09:59:24 PM »

Thanks gentlemen for the tips, great info. Yes, if you could give me a step by step process of shaping the wing, that would be great. Where can I get the plan for the "Super Sweep 22" that's mentioned in this forum? It does look like a nice glider.

Thank you,
Curtis
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Dan G.
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« Reply #5 on: April 12, 2008, 02:30:32 AM »

Hi Curtis ... happy to oblige ....

I imagine a full, illustrated tutorial would be best, and I have to admit, there is a stirring within me (moderators take note), but for now, I'll try a condensed version. I'll find out how best to submit a plan and do so.

Understand please, that this is an indoor design (Supersweep) and will not win the most outdoor contests -- its roll recovery is spotty because of the lack of dihedral and it will not thermal with the best of them. However, the construction procedures will be much the same with this design as with any other, given the differences which have already been outlined.

I build two at a time. I find that the procedures for hlg are so specialized and intensive, that much time and effort is spent renewing the methods on the first one, and it is quick and easy doing the second -- so I make two of everything.

I have a straight and flat sanding block, about two inches wide, high enough for a solid grip (maybe one inch), and the length of a standard sanding paper sheet. I'll use four or five grit sizes ranging from 80 to 400; all but the coarsest will be wet-or-dry which seems to last the longest. The paper is carefully, tightly folded and wrapped around three sides of the block, and the block and folded edges are rolled a bit on the table to ensure nothing will protrude into the balsa surface.

I use an E-xacto with a fresh #11 blade (where have I heard that name before), a few straight edges or steel rules (at least a six inch and a twelve inch), an extruded alum piece of right-angle at least as long as the sandpaper sheet and one to two inches wide, a piece of 1/4" plate glass with at least the front, long edge finished, at least two spans wide and one span deep which I'll constantly blow, scrape with the steel rules, as well as with a razor blade, to keep clean always (always, always), masking tape 1/8" and 1/2" or 3/4" wide, and a razor plane (mine uses disposable, double edged razor blades).

I use only five-minute e-poxy, but longer would be better -- I just don't have the patience -- for the assembly, and thin ca for strategic soaking and reinforcing.

I'll just post this now ... and continue some more, below ...

Dan G.
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Dan G.
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« Reply #6 on: April 12, 2008, 03:49:59 AM »

continuing from above ....

Every time I'm in a hobby shop, I scour the 1/4" balsa sheets for straight, light, quarter-sawn, hopefully 4" wide, but I've had to use 3" lots. To finish with a 26 or 27 gram plane (what I consider to be ideal), only the very lightest wing will do (6 lb/cu.ft or 10 grams per inch width on a 36" length) and it must be quarter-grained. I use almost the lightest, quarter-cut 1/16" for the tail parts, and 1/8" clear, straight, spruce for the fuselage, 3/4" wide, but you could probably squeak by with 5/8", a small bit of 1/16"ply for the finger, grip, and a strip of 1/8" sq. spruce for the leading edge. Any of these pieces could be made of smaller ones, spliced or butt-joined together, if need be, except for the fuselage -- it could have longitudinal joins but not cross-sectional.

I have a bunch of steel and alum blocks, about 4" square and 1/2" and 1" thick, which I use for weights and props (for propping up).

I'll presume that you can join any smaller pieces together successfully, but if you'd like a few words on that, I can do that.

I'll examine the balsa planks for the most advantageous place for the wing. Sometimes a curved grain can fit the curve of the wing, or damage on the edges, or damaged surfaces, and warps and twists, a heavier side, or C-grain fading to B-grain -- all can play a role in deciding from where exactly to take the wing. I'll put the plan-form outline on the plank, cut and sand the outline, leaving a fairly smooth, perpendicular edge.

The extruded alum right angle is faced on one side with about 120 grit paper. and some masking tape on the other side, near each end. This angular sanding rig is slid on the glass, on its masking taped bottom, and the perpendicular, sandpaper face is reciprocated against the wing's edge. The wing sits on a shim -- usually a balsa sheet, or sheets to vary the height for more even wear on the sandpaper, and to raise it above any part of the alum piece's, bottom, corner edge.

The 1/8" sq. spruce will be glued to the bottom, front edge of the wing, in order to better form and keep a sharp leading edge. I'll taper the ends of the spruce (width but not height), which will more easily allow it to be glued against the sharper curve, toward the tips. Then, with three long, straight=pins firmly anchoring the wing, over a piece of waxed paper, onto a wooden or fibre-board flat surface, the spruce is glued along the bottom of the leading edge, and pinned to hold it there.

I have to go now ... more tomorrow ...

Dan G.
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GrahamC
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« Reply #7 on: April 12, 2008, 08:03:44 AM »

Good day all,

Dan G. is giving a pretty description of this technique so I won't try to add anything to it. As I know of and use this same technique to shape wings I understand Dan's description.

I picked up on this technique only a few years ago and have used it since. I discovered it in an article in a British model magazine "Model Flyer" (now Radio control model flyer) in an article by well know British free flighter Phil Ball (CLG Catapulticus Nay 2002 and more recently Son of Catapulticus). It was one of those light bulb moments - as soon as I read the process and took a moment to reflect on what I just read it made perfect sense.

And not trying to steal Dan's thunder; another good reference are some articles published by Mark Drela on his RC glider designs and well worth a read (first one is particularily good if you have any interest in TLG or DLG types even if Mark's design is RC)

http://www.charlesriverrc.org/articles/apogeehlg/markdrela_apogeehlg.htm

http://www.charlesriverrc.org/articles/construction/markdrela_airfoilshaping.pdf

http://www.charlesriverrc.org/articles_construction.htm

http://www.charlesriverrc.org/articles/construction/markdrela_improvingsandingaccuracy.htm

cheers, Graham in Ottawa
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High Point
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« Reply #8 on: April 12, 2008, 03:12:58 PM »

Thanks so much for taking the time to respond to my wing shaping question; I've printed out the above info to take out to my workshop.

I've always had a interest in gliders ever since I got the old Comet Goldwing glider kit back in the 60's. I remember building it, but don't remember any notable flights (guess I didn't understand the importance of weight and balance or trim). Anyway there is a certain beauty in watching "the perfect flight" (I'm sure you know what I mean).

Curtis
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Dan G.
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« Reply #9 on: April 12, 2008, 03:37:09 PM »

Hi Graham,

Thanks for those references. The drawings are very helpful, especially as I wasn't going to provide any with this topic. Boy ... ya gotta wonder about that airfoil ... eh? Sounds like the greatest thing since sliced bread. I wish I had a the polars for a bunch of other similar-use airfoils for comparison. He is operating at higher Re. numbers than we are (faster speed and wider chord), so I don't know how translatable those airfoil performance data are to our application. The only testing I did, was to make two identical planes but with different airfoils -- one traditionally rounded, and one "triangulated" one with sharp L.E., sharp max camber, and flat rear camber. I threw them over and over, and felt confident in my assessment that the triangulated airfoil went up higher and had a lower sink rate. That sort of casual testing could easily be eclipsed by someone else's experience, so probably, everyone should convince themselves of the validity of their choice with their own tests.

I would be a little surprised to hear that a fully rounded airfoil would perform better than the sharp-edged alternative in our application, but not astounded. I would have to conclude that my tests were not rigorous enough to be valuable. We work with so little empirical data that we should be prepared to be surprised at any time. Who really knows what's going on with these airfoils on our hlg? We work in the dark with fuzzy theories and even fuzzier imaginings. My own idea is that the sharp edges on the triangulated airfoils provide essential turbulence (no attempt to keep things laminar) at the right places at the right times.

I'm sorry, Graham, but I tried to home-in on what was your light-bulb moment, and I can't seem to get it. Would you care to clue me in?

Dan G.

I'll get back to construction details later in the day ... I have to go now.
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GrahamC
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« Reply #10 on: April 12, 2008, 08:00:52 PM »

Hey Dan and all,

Marks designs and airfoils are well regarded by the RC glider guys. He has done much work on the aerodynamics of these types and yes, bigger and faster and in a different realm. Mark was (maybe still is) a free flighter as well. Had a few designs for peanuts published in Model Builder magazine many years ago.

My "light bulb" moment came when I was reading how Phil Ball described how he carved/sanded out the wings for these HLG/CLG's and showed some drawings. At first it didn't make sense just carving the back end of the wing to the same angle and getting a tapered root to tip shape as well. But then I mentally followed along and then cut the curved leading edge back and voila - tapered from root to tip just as described. Dead simple once you grasp what is happening and I have made CLG/HLG wings that way since. No muss no fuss and no measuring.

Airfoil shape is another topic for good discussion. I also belive the straight top (from peak to trailing edge) shape is the better choice although I tend to think so because it removes a lot of dead wood that otherwise isn't doing much. Also, a nice shinny smooth bottom wing and a somewhat rough curved leading edge bit for some turbulence.

cheers, graham
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Dan G.
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« Reply #11 on: April 12, 2008, 10:47:43 PM »

Hi Graham,

Yah ... I also like the wood (and weight) removal to make a flat rear camber.

I haven't roughened the leading edge however; I was prepared to accept the notion that the sharp leading edge would provide all the turbulence needed and when most needed, i.e., increases with angle of attack.

Dan G.
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Dan G.
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« Reply #12 on: April 13, 2008, 12:29:03 AM »

continuing from reply #6 ...

Always keep a check on the lateral balance of the wing. I will make sure that the wing blank started as being heavy on the inside (i.e., port side), and constant checks make sure that is maintained.

The next step is to prepare the bottom surface. The surface is examined and made flat if needed, then sanded as smooth as possible. From this point on, the bottom surface is guarded, and not to be touched again, if possible, except for the leading edge, The wing is not to be placed again on the glass without the glass being swept clean with a steel edge.

A thin line is marked along the leading edge, about 3/64" high at the centre, and reducing in height toward the tip to retain approximate proportions to the rest of the chord locally, and the bottom nose camber is sanded in. The bottom surface is now complete. All efforts are made to keep it clean and blemish-free.

The next step is to taper the top surface toward the tips. I try to taper flat, with razor plane and sanding block, maintaining equal thickness fore and aft, just as in the sketch you printed from Graham's link. The idea is to maintain constant proportions of the airfoil, regardless of the size of the chord or wing section. Since the plan form-taper is approximately elliptical, so will be the taper. The thin razor blades won't plane the spruce, so I use coarse sandpaper to cut the spruce.

Dan G.

I'll post this now and come back later...
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Dan G.
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« Reply #13 on: April 13, 2008, 02:58:02 AM »

continuing from above...

I've been trying, unsuccessfully, to get a scanned image posted, but I'm having trouble. This design, with a very good construction article and plans, is in the September 1974 issue of American Aircraft Modeler. The model had just scored an indoor, single flight time of 90.0 sec..

The next task is to mark the max camber or high point. Believe it or not, I still poke holes through a paper template. That actual high point should not be touched with sandpaper again, but only those areas adjacent.

I shape the rear camber first, so with the 1/8" wide masking tape, I run the tape forward of and edging the max camber along the span of the wing. With the razor plane and varying grades of sandpaper, always (always) wrapped tightly on the sanding block, I'll remove all the wood to form a straight line from the tape to the T.E.. Coarse paper must be stroked parallel to the grain to avoid scoring the wood, Restrict the circular or orbital sanding patterns to the finer grits. Keep the paper clean and watch that little pieces of frayed masking tape don't get caught and rolled under the sanding block. I like thin trailing edges so I make them as thin as I dare. The procedure is to place the wing on the glass working surface, with the T.E. aligned along the glass edge. If you go back to pedr01's reply #2 earlier on, he describes that varying the actual distance the T.E. is from the edge of the glass will result in thicker or thinner trailing edges.

Only the purest C-grain can provide a thin trailing edge; anything else should be left a little thicker. While working on really thin areas, be gentle with the sanding block, don't use much pressure, and keep a really sharp eye that the edge doesn't start to buckle and wave. If it does -- you've gone too far and not much can be done. When you have to be gentle, consider using a grade coarser paper -- a few fine scratches, especially that far back, is preferable to a wavy T.E..
 
I keep a sharp eye at he max camber, to make sure the apex is never touched and the edge of the transition from either side of the high point is maintained as fine and sharp as possible. The rear camber is then planed down and sanded flat and smooth, and to be not touched again. The tape is removed by pulling it forward, away from the max camber, and a new strip is placed rear of and edging the mean camber line. The forward part of the top camber is then shaped (planed and sanded), keeping the max camber edge sharp and the leading edge sharp, and watching that the softer balsa isn't eroded away adjacent to the harder spruce. Keeping the sandpaper tight against the block will help.

I play with the light sources constantly, always checking, always checking. That sharp max camber line is the real concern -- it is so easily damaged or reduced with one inadvertent touch of the sandpaper. I usually have a few pin holes, from the large pins used to anchor the wing during the L.E. spruce attachment,
which can be closed with a drop of water, and touch-sanded when dry. Any blemishes can be so treated. The water softens and swells the wood. Obviously, pressure indentations will swell-out better than scratches and troughs, which have had wood removed and not just pressed in.

That's the story for my shaping a wing, Curtis. If you'd like a continuation of the construction process, say the dihedral joints, I can do that too, if I had a sense that it were required.

Dan G.
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« Reply #14 on: April 13, 2008, 04:53:24 AM »

Dan

Don't want to contradict, just reading above makes me realise that your little pinkie has forgotten more than I ever knew in the first place, but ...

Why would you want to ensure that the inside (port) side is heavy. Surely, if you placed the slightly heavier piece on the outside it would counteract the fact that the port side travels slightly slower and provides less lift.

As I understood, that was/is the prime reason why we a) washin the port side, or b) offset the port side so that it is slightly larger ... ie to keep the wings level and prevent spiral dive ...

pedr0  Huh
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« Reply #15 on: April 13, 2008, 04:22:49 PM »

Dan,

You've put a lot of thought, effort, and time in your wing shaping instructions, I really appreciate it. This is a wealth of information you've put out. I will print it and study it carefully. Do you have any simple drawings, diagrams, or pictures that could be posted to go with your instructions?

Thank you,
Curtis
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Dan G.
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« Reply #16 on: April 14, 2008, 12:07:27 AM »

Hi pedr01,

Deflected flying surfaces have different effects at different flying speeds, rudder perhaps being the most extreme in its differing effects. At high speeds, it will overcome almost everything if it is just a little too deflected; at low speeds, it has little effect until at stall (or just prior to), it has virtually none.

Lateral CG is constant (in level flight), but is easily overcome with any speed as the flying surfaces all increase their effect and sort of lock the ship tighter in its flight pattern. The faster the speed, the less effect the CG has as proportion of the overall controlling effects. At low speed flight however, as the rudder loses its effect, the heavy inside wing will serve to keep the flight pattern constant. Finally, just prior to stall, dropping the inside wing early will ensure that the plane does not do a straight-ahead stall. I'm not talking about a big CG shift or a very heavy inside wing -- you can easily overdo it.
The plane shouldn't circle as if it were on rails or in a groove. It should show a little dutch role, or waffle once in a while during flight at minimum speeds. A really heavy inside wing wouldn't permit this, so I'm talking only as heavy as to ensure that all other things equal, it will fall to the inside.

Having a slightly larger inside wing would have a determining effect (all other things being equal) only at the very lowest speeds. All other control deflections would overcome the effect of its larger size at any higher speeds, say during cruise. Its effect is about the same as lateral CG -- almost none except just prior to stall. Consequently, as a counter-effect to spiraling (a high speed event) it offers little to none.

Wash-in is more complicated because both of its effects -- lift and drag -- vary hugely with varying flight speeds. The lift component is easier to visualize, and the faster the speed, the higher the lift and banking effect. The drag however, has a skewing effect toward our turn (remember that we are turning against the down-aileron, or wash-in), and with full-sized flying, it is referred to as adverse yaw. Rudder must be applied to counter this adverse yaw to effect a balanced turn. Without the rudder, you would end up yawed to one side while banked to the other, and slipping and sliding across the sky without really turning. I'm sort of guessing here, with full-sized aircraft or controllable aircraft -- Sundance might sometime describe what could or could not happen due to adverse yaw.

The important point in our case is that at high speeds, it is strong enough to counter some rudder -- and the two are played against each other to establish the high speed turn. A tiny bit of wash will easily overcome the effects of any differences in area or lateral CG location. But, in free flight, our favourite speeds are at minimum sink. In that flight realm, the aileron effect has been so reduced and the adverse yaw (drag) just keeps increasing right through the stall. Prior to the stall, the turning effect from the wash exchanges the overall effect from one of positive (banking the wing) to negative (holding the wing back) and the wash actually produces a turn toward the wash.

Finally, at the point of stall, the washed-in wing stalls early (increased angle of attack) and the ship falls toward the inside. If you can get this to happen early enough (but not too early), a complete stall may be averted as the plane drops the wing a bit and swivels. Picture this happening when everything has slowed down, equilibrium is weak, forces are marginal but subject to large fluctuation (stall of a tip, or even stab if it's too heavily loaded or too small), and a little timely pirouette could mean the difference between thermal coring and dropping twenty feet into a full-blown, straight-ahead stall. Note that a too-heavy inside wing would ruin this whole stall-prevention, or stall moderation event.I think you can probably put your mind at rest about the differing tip speeds in a turn having any appreciable effect. It might be a concern with very large spanned ships in very tight turns, but otherwise, the resulting difference in lift is easily overcome by a number of control inputs -- namely, sufficient wash-in or opposite aileron and of course, sufficient longitudinal dihedral, or decalage, or what ever we're not supposed to call the difference in incidence between wing and stab (up elevator -- to the controllable types). Maybe Kev, if he's reading this, might offer some insight into circular air flow and if he's ever noticed anything with his sailplanes.

Spiralling problems have been reduced with a reduction in fin size -- just take a look at competition planes of today, and those from before WWII. I can think of ways that a large fin would turn an incipient stall into a spiral.

Dan G.

I'll have to make another posting to finish.
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« Reply #17 on: April 14, 2008, 12:19:30 AM »

continued from above ...

So, all of these trimming devices (and more) are used to trim a good flying glider. It may sound complicated now, and it is, but with a little experience, you probably will be able to just give a plane's flight a glance and see what's coming into effect and when. There should be no mysteries as to why a plane flies the way it does. If it won't cooperate, keep examining it -- often a wing has a slight warp or the section has reflexed a bit -- subtle to the eye but it will wreck your flying pattern. Learn to look at the plane from the front and from the rear, and with varying light direction.

If you want more, do ask ... or if I've contradicted myself, or if confusion still reigns.

Dan G.

By the way ... you can insert only 5500 characters in one posting.
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« Reply #18 on: April 14, 2008, 01:31:32 AM »

Hi Curtis,

I don't have much in the way of pictures. What I will do, once I've figured how to move my scans and pictures around in my computer, and resize them, is scan pages or photos from the original American Aircraft Modeler mag. These may give you enough of a basis with which to work. I will try again tomorrow.

Dan G.
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« Reply #19 on: April 14, 2008, 03:30:14 AM »

Thanks loads Dan,

I'm with High Point, this is a print out and keeper. I've learned so much already just in the HLH, CLH threads.

Pedr0
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« Reply #20 on: April 15, 2008, 12:22:54 AM »

Hi Curtis,

I'm afraid the scans from the magazine pictures, which were pretty poor to start with, aren't worth trying to post. The most I can provide right now is a scan of a drawing of my plane -- almost identical to the Supersweep.

The airfoil I've been using for a few years, now, is the bottom one with the slightly raised nose. Not marked on the plan is that both tip dihedral joints are skewed and parallel. That four degrees skew isn't quite enough. I end up putting more wash-in and wash-out in the field.

Try looking at those drawings in the website which Graham posted a while back in this thread -- shaping without a template, if I recall. Some of those techniques apply here.

Do let me know if you reach a stage where you're prepared to do the dihedral-joint thing. If I haven't posting anything on the subject before, I'll tackle it then.

Dan G.

I'm still having difficulty with my scans, so I'll post them in the next posting. I've already lost some text this evening and I'm afraid to lose more.
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« Reply #21 on: April 15, 2008, 01:49:06 AM »

Okay ... trying to post a scan.

Dan G.
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« Reply #22 on: April 15, 2008, 01:18:49 PM »

Thanks Dan, I can use the drawing you posted for sure; looks like a fine design. I do have experience with dihedral-joints (basic).
I'm still a little confused about the airfoil process (no jigs?). Do you taper the wing blank first? Then by masking the high point, start sanding back to the TE, re-mask and sand the fwd section toward the LE. I don't think my light bulb has turned on yet. I might be making this too hard?

Curtis
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« Reply #23 on: April 15, 2008, 03:41:41 PM »

Hi Curtis,

No, I don't think you are making it more complicated than it is, and it appears that you have the correct sequence of shaping steps. It is fairly complicated and without jigs, it is exacting work -- the risk of removing too much material is always there. And, that max camber line in soft balsa is so delicate, that one inadvertent stroke, or even touch, and it disappears. I have described the process -- go back to reply #6, half way down, I start the actual wing shaping by cutting out the plan form and gluing the spruce L.E.. The wing shaping is then continued in reply #12, and in the last paragraph there, I start the wing taper. At this point, look at the drawing, at that website Graham linked, about shaping without templates, which shows how this taper is effected.

My plan shows a fairly bulbous shape to the nose. The shape of the nose is inconsequential. You could run a straight line from nose to wing, make the whole fuselage 1/2" or 5/8" deep only, and not affect the plane -- it might even be a tad lighter. That nose shape is for personal aesthetics only. Maybe there's a nose shape that appeals to you. If you wish to change the nose length, there is a trade-off -- longer noses mean lighter to balance but increased moment of inertia and a slight decrease in stall recovery and prevention; shorter noses mean heavier planes but a snappier pitch recovery.

Dan G.
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« Reply #24 on: April 16, 2008, 12:06:22 AM »

I've finally scanned and retrieved a few pics. They don't really show a lot that's of any value, but, if you examine the picture with two gliders, the uppermost one , on the starboard tip panel, you can see a reflection showing where I lost that sharp max camber line, for about an inch just outboard of the dihedral joint. I don't remember how it performed, but the effect of that difference would probably be swamped by almost any other quirk.

These were not the finest examples of beautiful hand launched gliders. The wood grain appears marginal and I was making-do with three inch stock. That joining glue line, no matter how fine, is always a pain, and needs special attention when sanding. Note that the wing is glued off-centre on the fuselage, so that the fuz just needed to be slightly beveled for the wing saddle, instead of having to cut a v-notch.

I keep the top line of my fuselages straight and glue both wings atop that, for alignment. Since I've been using an airfoil with a slightly raised nose, I've had to put a little positive angle in the stab -- this is important or you can find yourself warping in a lot of undercamber into the stab and it will over-pitch during the launch.

I don't understand why the original designer glued his stab to the bottom of the fuselage -- you then have to carefully aligne the wings, and carve a fancy, cambered saddle for the stab. Much easier (and easier to be accurate) to glue the stab on the top and carve the fancy saddle out of the fin's base. I also off-set my fins by as much as 1/8". The final position of that fin will be critical. Although that little, low-aspect-ratioed fin requires a lot of deflection for the turn, a hair more than required will spiral your ship in.

Oh yah ... that little dip in the fuselage just after the wing, featured in so many hlg designs, including the original Supersweep, is anathema to good engineering practice. Everybody should cut that out. Why artificially create a stress point?

Dan G.
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