Mad-Mac Catapult launched glider

[stupid]

Captains Log Stardate MMXXIV.XXVII.IV

   Greetings from  The New Frontier. In our last episode, Mad Max Parabolic dihedral glider wing was finally assembled and in its last trip through the oven. The next morning I was pleasantly surprised to find that the parabolic wing was still attached to the form. I did have a little separation of the balsa wood on the starboard trailing edge of the wing, but it was easily repaired.

  To shape the airfoil leading edge. I used a small Spokeshave made by  Zona Tools to rough in the shape the compound curve. Then finished the airfoil shape with a airfoil sanding tool using the base of the Jig, sweeping the sanding tool span wise along the wing. I removed the wing with dental floss from the jig and finished up the airfoil with some hand sanding. It all turned out amazingly well. I'm not easily the type to be prone to whimsy, but it might be safe to say that I'm quite thoroughly stoked.

   To protect the leading edge. I put a puddle of thin cyanoacrylate on a piece of wax paper and drug the leading edge of the wing through it. I do have quite a bit of experience using this method with stabilizers and fins and it turned out better than I expected, after a little smoothing out with a nail file.

   The wing was then sanded super smooth, all right fairly smooth, okay okay. I just knocked off the lumps with some 220 grit sandpaper prior to a coat of sanding sealer. Then a final sanding with 320 grit sandpaper. The weight gain was only .4 g. from the sanding sealer. Total weight of the wing  11.4 g.

   For some mysterious reason, and not anything that I had planned. There was some Phillips entry that crept into the bottom of the wing. A lucky happenstance.

  The last thumbnail photo is the wing, held up to the light to expose the geodesic rib pattern. Don't pay any attention to the thumb. I shouldn't have said that, you probably wouldn't have noticed. The wing is quite stiff and it did hold its parabolic shape. Every silver lining has a dark cloud.

   Specs: projected wing span of 18" by 3 1/2",    HP .207, 28%,    4" from center .20,    7" - 160,    wing tips .064,   trailing edge .040, Dihedral 2 1/2" each wingtip.
   
   Soon will be the fuselage, if you were here at HPA before the content disappeared. You'll know what my favorite fuselage is. If you are new, your in for another stunner. But will be crossing that bridge after we burn it. Or, will be burning that bridge while we're crossing it.   You decide.
                      a.k.a./stupid

[stupid]

Captains Log Stardate MMXXIV.XXVII.IV

   This is my go to fuselage after discovering Pampas Grass stems for the tail booms. Pampas Grass is used for landscaping decoration, and it's best to harvest around the New Year. The straightest stems are selected that are approximately 3/16 inch diameter for this size of glider and let them dry for at least three months.
 
   The 3/16 inch diameter Pampas grass stems calculate out to be 11 lb/ft³, but are very much stiffer than a comparable balsa wood diameter dowell would be because of the hard material around the  pithy center of the stem.

   Shape the concave slot for the stem in the fuselage by spiral wrapping sandpaper around a wire rod in a jig & sand away on both sides of your fuselage stock .

   I've been cutting my fuselages to size on a small bandsaw, of course, you could use any method you prefer. The Pampas Grass has a slick coating and needs to be ruffed up with sandpaper before gluing to the balsa wood with PLIOBOND adhesive.

 The front 3 inches of the fuselage is 3/16 inch diameter  wooden dowel so that the .047 wire launching hook will not pullout.
                  a.k.a./stupid

[stupid]

Captains Log Stardate MMXXIV.XXVII.IV

  The Launching Finger Grip is made from 1/32 aircraft plywood using the smaller hole saw to cut the disc that is shaped into the finger grip. The larger nesting hole saw was used to cut the plywood disk that was used on a mandrel to notch the fuselage for the finger grip.

  The stabilizer and fin were made using polycarbonate plastic templates on some gorgeous 5.2 lb/ft³, pre-tapered 1/16 leading edge 1/32 trailing edge C grain balsa wood wedges. With the leading edges just rounded over. The swept back leading edge of the stabilizer gives a taper to the tips.

 With all the parts made now it's time to assemble everything together in the final episodes of Mad Max Parabolic dihedral glider. Will it fly? Stay tuned for the next  thrilling cliffhanger of a episode.
               a.k.a./stupid

[Rekitus]

am late to this party...

I like the looks of that airplane.
Right now I am thinking of ways to make one.

I am gunna go harvest some pampas grass cause I have some.
do you clear out the pith?

victor

[stupid]

victor,

  The short answer is no. The pith is a integral part of the hoop strength of the stem because it keeps the outer shell from collapsing when flexed.

   Another benefit  of using Pampas grass stems instead of say, tapered carbon fiber tubes, is if the glider gets run over in the street, you're not out a lot of money.

  I've been experimenting with other uses of Pampas grass stems. On scale rubber model airplanes the fuselage formers as they are in most drawings, are too heavy, to week on the inside. Some scale rubber model airplane builders used cyanoacrylate adhesive on the inside of the formers to keep the formers from splitting, mostly from rough handling. But that led to the rubber motor being abraded as the motor wound down, causing the the motor to break prematurely. My solution was decrease the width of the former by enlarging the hole and gluing a narrow band of Pampas grass stem to the inside of the former, strengthening  the former and eliminating the abrasion to the rubber motor at the same time. Just how far you can reduce the wall of the former, I haven't discovered yet.
                          Bob   a.k.a./stupid

[OZPAF]

Very, very neat looking wing Bob! You will need to change your HPA nickname to Captain impossible!

I also like the idea of using a ring of the pampas grass to reinforce the inside of the rubber model formers.

John

[stupid]

John,

Here is a quote attributed to Henry Ford.

"If you always do what you've always done, you'll always get what you've always got."

I was hoping my comments were not falling on deaf ears, hard of hearing, BUT NOT DEAF… YET.
   Actually, I'm happy you're following along. In the next episode. There will be some stunning photos of Mad Max in the buff. Coming soon, I promise this time.
                      Bob     a.k.a./stupid

[OZPAF]

I'm always open to new ideas Bob.

Actually that method of reinforcing formers reminds of the shallow formers of many full size aircraft which had a return flange on the inside to increase their stiffness.

The idea was also used in early space frame racing cars of the 70-80's.

Keen to see how your glider looks assembled and how it flies.

John

[stupid]

Captains Log Stardate MMXXIV.XXX.IV

STARGATE--Activating Porthole,  from the 4th dimension to the 5th dimension in the space-time continuum.

  It doesn't take an advanced degree in physical therapy to figure out that each side of your glider, that is port or starboard, should be symmetrical. Being that there is no dihedral break in the center of the wing to locate the wing on the fuselage, I used a cloth measuring tape to find the center of the wing on the back. And standing the wing on its trailing edge on a flat surface with a 90° triangle making sure it was straight up. I  marked at the leading edge and trailing edge 3/32 each side of the centerline to locate the fuselage on the center of the wing. My polycarbonate template for the stabilizer has a center line so marking out 3/32 each site for the tail boom was easier.

   To shift the center of gravity for balance at 50%, a 5/32 whole is center drilled on top of the wood dowel 5/8 of an inch deep into the end of the nose for the 5/32 diameter lead weight.

The assembled Mad Max glider.    I'm going to go out on a limb here and called this passable.

  Here are the the weights for the parts.
    Wing   11.4 grams.
    Fuselage, 20” long   7 (lb/ft³)   3.6 g.
    Tail feathers   5.2 (lb/ft³ ) C-grain   .8 g.
    Grip & Hook, .5 g,
    5/32" diameter lead to balance at 50% CG. 1.9 g,
    Total  Mad Max weight  18.2 g.

   I think all these figures are correct, I did get a gymnastes scholarship at Wossamotta U. (Although, most of what I remember is the women, beer & the hangovers).

  In the next futuristic episode of the Mad Max Parabolic dihedral glider. I will be Comparing the glider wings of Stray Cat X & U.S. Kid to the Mad Max wing. It could be challenging, but I'll try to hang on to my will to live.
                       Bob    a.k.a./stupid

[Rekitus]

OOoooooO!

nice looking.

I have to ask, 
can you tell if you have wash-out near the tips?
... hmmm  does it need that...

habits from old 4 panel gliders.

victor

[OZPAF]

Very graceful glider Bob. Keep away from the thermals!

John

[stupid]

Captains Log Stardate MMXXIV.III.V

   Finally, the Final Frontier, where we have reached the outer boundaries of the ever-expanding Universe.

   I thought it might be challenging and a little fun to compare the three glider wings to each other, little did I know what I was getting myself into. Not easy to compare the different thicknesses of the wings and the wing planforms. I did calculate the amount of balsawood in each wing design by dividing the wood in lb/ft³ by the balsa wood density figure 3.81, and then multiplied that figure times the weight of the wing in grams to get how many cubic inches of balsa wood in the final wing. Something I've never seen anybody calculate out, cubic inches of balsa wood in wing.

  I would have put all the figures in the text, but there is no way to have columns in the post. So the comparison charts are in the thumbnail photos.

 Actually, I'm delighted with Mad Max Parabolic dihedral glider, although I was a little surprised with multiple layers, the weight of the glue really adds up. 2.1 g glue, about 1/3 of a teaspoon. Nevertheless, considering the wing being hollow on the trailing 2/3ed, I was expecting the final weight of the wing to be less than it turned out to be.

   In the next installment Mad Max will be dressed up in his Flashy new duds, not just lipstick on a pig.
                                   Bob a.k.a./stupid

[stupid]

Captains Log Stardate MMXXIV.IIII.V

    The weather Friday morning was absolutely terrific. I’m in the model work shop first thing, rattling the spray paint cans, stepping outside to spray the color on  Mad Max.  Black checker pattern on the bottom of the wing, yellow and red wingtips with Hot florescent Red. I rub the roughness of the spray paint out with wax paper and stage a few photos of Mad Max subtle but flashy new look. I really like the checkerboard pattern on the bottom of the wing, the extra black of the pattern helps to see it when it's high in the sky and enables some color on the bottom of the wing tips.  The pattern is created by using rubber shelf or drawer liner as a stencil. Looking at the bottom view of Mad Max, reminds me of a rebel wearing a Zoot suit.

Flying

    Arriving at the park, the sun rays were sparkling through the newly emerging leaves of the trees just like pixie dust dancing around the limbs.  Could this be an indication of a magical morning of glider flying.

    Setting up the glider with 0.050 thick paper punch out lead weight glued on the left wing tip to tighten the glide circle. Wash in wedge, 1/2 inch wide tapered to .055 thick, 7/8 inch long, for this size of glider should be right. I do a few straightahead low powered test glides and add on some additional nose weight to correct a slight stall. As always I'm a little jittery for a gliders first flight, now just a little more because I've spent more time and effort building this glider than any other glider. It's now or never.

  Walking out into the park with Mad Max at the ready, standing there for what seemed like ages, which was only maybe five minutes. The thermals started rising all around me like Hallelujah arms, and the fluffes, swirling as if eagle shadows on the clouds. I was apprehensive, I didn't want to lose her, but launched Mad Max straight up with a full stretch of the rubber.  Fumbling to locate the glider on the flatscreen, I gave up and resigned to enjoy watching  Mad Max circling in the thermal, going higher and higher and getting smaller. A sense of dread waved over me, and did a palm plant on my forehead, then to my relief, the glider circling, drifted over the pond in the park and the thermal dissipated, Robbing Hung of his booty. I'm calming down now, and I managed to get one photo before Mad Max slowly settled onto the grass a little over 2 minutes, achieving a Max on its first flight.

   Many who fly gliders are driven by a deep, almost desperate need. So much of the world is bullshit. But learning to build and fly gliders in thermals is one of the most exhilarating things that you can learn to do, makes the rest of the world seem unreal. It's something you can do where you don't necessarily need to follow any rules.

   Back in the model shop, I remeasured Mad Max.  Flying weight, 19.5 g. CG 46%.
wing area 61.71 in.²,   for a wing loading of .315 g/in.²
  
 Thanks for having stuck around.      And being a good sport.
                           Bob    a.k.a./stupid

[iflyhlg]

Very nicely done, Bob. Enjoyed reading about the whole project. I might revisit my elliptical design after seeing yours. I would prefer that you had a DT on such a nice model. I hate losing them after trimming them out.

[Rekitus]

oh what a beauty!

If you add a DT please share that?

victor

[stupid]

Bruce & Victor,

   I'm delighted that you enjoyed the build article. It was my goal to write something a little more unusual than the --- strictly, what I did, or procedure method. After I started writing, it became more fun as I added more levity to the article, embellishing the sentences with more descriptive words,  Then it morphed in to being a little more outrageous. Although everything I wrote actually happened, as you can see from the photos. I did censor myself some.  I am considering including parts that I thought were inappropriate in a addendum.

   Dethermalizer--- I haven't been using dethermalizer's for quite some time, because most of the gliders haven't taken me very long to build, except Mad Max. I have just as much fun flying the quicker building gliders and not concerned if they fly away. The U.S. Kid glider did have a dethermalizer, it was quite heavy. Made from 1/32 inch aircraft plywood and covered the depth of the fuselage. I found that pop rivet & 1/64 aircraft plywood was sufficient and just cover the joint .7g.  for less than half the weight. The problem is those big viscous timer dethermalizer's out in the windstream causing's drag.
            Bob    a.k.a./stupid

[Rekitus]

Hi I-Must-Call-You-Bob,

part of why I asked about a DT is because I have no idea what one to use
and I figured I'd try what ever you used.

for your mad-max to get into a thermal is a mind blowing thought to me
It is small, I once thought thermals didn't start until 50 60 feet.
above trees for a visual, I've not tossed one that far yet...

that plane looks like it will float.

victor

[stupid]

[quote

part of why I asked about a DT is because I have no idea what one to use

[/quote]
victor,

   There is a Builders Plan Gallery link, you'll find at the top of the HPA page.  Bruce's Hoosier Kitty 2. A good diagram on how to build a Pop up Forward Wing.
http://www.hippocketaeronautics.com/hpa_plans/search.php

and silly putty timers
http://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=12683

for smaller catapult launch gliders look at The Straight up. For a pop out tab DT's
http://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=12752

I hope this will help on your journey.
               Bob

[OZPAF]

Well you couldn't ask for much more than that Bob. Max on the maiden flight and it ended safely.

Put it in a display cabinet 

Thanks for all the info during this interesting build.

John

[stupid]

John,

  It's not often you can get a catapult launched glider in a thermal the first flight. It's only happened for me one time before, with a modified Stinger 2 by Tom Norell,  enlarged to 12 inch wingspan. I had six of them, where I gained a lot of proficiency in trimming gliders using Stan Buddenbohm's method of test gliding with low powered tests straightahead.

   After Mad Max first flight. I didn't want to risk losing it before I had reweighed and found the center of gravity. It's been sitting in a box sense. I wouldn't mind watching Mad Mac Fly out of sight in a thermal if there was someone to witness. Out of 3 1/2 million people along the northern front Range of Colorado. I only know one other fellow who flies catapult launch gliders, the rest of the club members live near Colorado Springs. I believe the lack of free flight enthusiast is because the world has been taken over by The Blob. The evil substance is some kind of synthetic polymer.

https://www.youtube.com/watch?v=vq0our4mceQ

[OZPAF]

The Blob

  Wasn't that the film that introduced Steve McQueen to the screen?

It's pretty much the same here. I think it requires too much thinking for many people.

Nice description of trimming - the emphasis on observation is spot on. Thermals here (near the coast) are rarer in frequency and generally not as strong - i have still lost a few CLG's when they have drifted with a weak thermal and disappeared behind buildings etc , without actually going all that high - a couple of hundred feet or so.

Happy flying.

John

[stupid]

Steve McQueen -- the man who endured a profession to make money to follow his dreams. Racing cars and motorcycles.  The most exhilarating thing you can do, risk your life.

  Maybe it's just the new generation raised on Game Boy's and Atari's, they're more interested in what they can do with their thumbs. :-). On a more seriouser note, I've found articles written in the Frank Zaic book, 1957/58 about the problem of trying to get more youngsters involved in free flight.
  It might not be a problem at all. Could it be the Evolution of the Species, from using opposing thumbs and fingers to just using your thumbs alone?

  I'm flying in an urban area in a redevelopment of Lowry Air Force Base. The City let there be one very large open space called The Great Lawn Park, (Superfund cleanup site) the surrounding area mostly unfenced. My longest flights are when the breeze is out of the North and East, and the skies are clear  The thermals are generated on the hotspots of asphalt (red circles). If the glider's obtain sufficient height, they will be sucked into the really big hotspots over the building roofs surrounded by asphalt parking (purple circles) where they go OOS straight up above the buildings. I never know where they go once they leave my view, they could be circling up there still, above the Metropolitan Asphalt Jungle. I did have one modified Stinger 2 glider found by a small boy in the lower branches of a pine tree 6 miles away. He called the phone number on the glider and I think he was hoping for a reward. He was surprised when I gave him the glider and a launching stick and explained to him how to fly it.

[OZPAF]

That article just shows how old the problem is!

I think it is quite an involved subject and I don't think a successful solution has ever been discovered.

Happy flying.

John