Crescendo Build

Jazzenjohn

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I've designed, built, and flown 4 different ultralight gyros. Amassing parts for a 2 place now.
Total Flight Time
400+
That looks like a diaphragm type vacuum pump to me Brian, but It also seems like exactly what you want. Definitely post pics of your work. I know I'm interested in trying to make composite parts myself. My current tube and fabric tail, while light and functional, is also pretty ugly.
 

Brian Jackson

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GyroBee Variant - Under Construction
That looks like a diaphragm type vacuum pump to me Brian, but It also seems like exactly what you want. Definitely post pics of your work. I know I'm interested in trying to make composite parts myself. My current tube and fabric tail, while light and functional, is also pretty ugly.

Here is the link to the pump on Aircraft Spruce. It says dry piston type, though I claim ignorance of being able to differentiate. Still on the easy slope of the learning curve. I will be sure to post photos of the steps involved, including the inevitable mistakes. I get the feeling it's a bit of a black art from the plethora of YouTube how-tos. The "bagged infusion" method of vacuum drawing resin through the material is interesting.

For your tail, what would the configuration be? I'm still looking into how to make the molds without going full CNC.
 

Jazzenjohn

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Milan Mich.
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I've designed, built, and flown 4 different ultralight gyros. Amassing parts for a 2 place now.
Total Flight Time
400+
I remember the rendering of your tail Brian, and it a was very complex 3d sculpting compared to the utilitarian stuff I do. I want to try some simple D tube bends to begin with. I want a "tall" tail but I don't want a top support so I'll have to do some thinking on how to make that work, if it is possible. A fairly center mounted semi cruciform tail can be done if the tail boom is lifted.
 

Brian Jackson

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I remember the rendering of your tail Brian, and it a was very complex 3d sculpting compared to the utilitarian stuff I do. I want to try some simple D tube bends to begin with. I want a "tall" tail but I don't want a top support so I'll have to do some thinking on how to make that work, if it is possible. A fairly center mounted semi cruciform tail can be done if the tail boom is lifted.
You're kind of describing what I'm doing. The tail you may be referring to was an old design from ages ago (wow, has it been that long?) Like the one you're contemplating, mine will also be a tall-ish design with no Yard Arm, to borrow Ernie's vernacular. That was part of the reasoning behind doing the outrigger cones and tension struts midway down the tailboom; To minimize twisting of the tube under load from the empennage. It was the simpler, lighter solution to the tail support problem that tied right into the diagonal bracing, which was itself done to reinforce the tailboom per some practical observations by Doug Riley. My hope is that these 2 systems working together in opposition (tension and compression) create enough rigidity in the tailboom to allow a larger tail than would be allowed on an un-braced tube. Knowing those limits is a gray area though.

Design-wise, complex but not overly. Similar internal cross-sparring to a tall-tail but in a 2/3 height format. Apogee of airfoil curve lands on spar in all 4 directions from spar intersection, but scaled longitudinally to form independent LE/TE sweeps. Separate vertical stab and hinged rudders by the way. I wouldn't attempt an all-flying tall(ish)-tail with only a single pivot point, cantilevered support. Fortunately the GyroBee configuration capitalizes on the added leverage of a longer tailboom, requiring less empennage volume than a close-coupled tall-tail. This provides a good bit of distance along the tailboom to anchor a vertical fin rigidly all the way up to a safe distance behind the prop. HS height is approx. 2/3 the prop radius (1/3 lower than prop thrust line) where it can take advantage of maximum high-speed airflow... I imagine the area behind the prop hub isn't doing much for thrust, so centering the HS there is essentially removing some of it's mid-span width from being effective as a down-force element. The HS and VS have opposite sweep directions, with the VS sweeping forward which I'll explain.

The only real deviation into complexity is the rudders. I pluralize them because the hinge angles change at the HS. The hinge below the HS leans forward about 20 degrees while the one above leans back about 30 degrees. They are connected with a U-joint to operate synchronously. The reasoning here is, in a vertical descent, the rudder under the HS has more authority than a vertically hinged one. (The rudder above is blocked by the HS in a vertical descent.) But if both rudders were forward tilted on the same axis you'd have an airframe pitching moment introduced in normal flight because of the downward vectored deflection. So I chose an equal-and-opposite approach that isn't as efficient in normal flight, but more effective in an emergency situation. And I do hope someone on the Forum will chime in if there is a glaring error in my understanding.

Perhaps the two of us will go down this road together. As I was writing this rather long-winded reply, the rest of the order from Aircraft Spruce just arrived. I hope that through some trial-and-error documentation you might get the bug too. Comparing notes and sharing tips would be all too welcome.

Brian
 

All_In

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Crap, I wish I had seen this before you bought a vacuum pump. We just use old refrigerator compressors.

I did not watch this only picked a video that should show anyone much faster than I could describe the simple process.
 

All_In

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Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
But you will look much more professional than in our shop.
 

Brian Jackson

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Thank you, John. David McCutchen also mentioned using refrigeration pumps in another thread. Seems like a great idea. Ultimately I decided to purchase one purpose-built for this. Whether that was the wisest choice I do not know, but was hesitant to introduce any further unknowns into an already complex process. Saving some dough would have been nice though.

20200131_203802.jpg
Today's shipment came in two packages, and everything was well wrapped. Aircraft Spruce's online order form gives you the option of folding or rolling the materials and plys. I can't imagine a scenario where folding would be preferable. I also chose the 206 hardener for its longer pot life. (Insert Gyro Jake joke here. I miss him)

20200131_224055.jpg
I was surprised how shiny carbon fiber material is. I also purchased two different types of film, one of which is claimed to be more elastic around tight inside corners. Though these films and fabrics are only for testing and learning, I'm keeping them fingerprint free.

20200131_204655.jpg
The pump seems to be pulling the correct pressure. With the filter and gauge attached it is remarkably quiet. You wouldn't sleep in the same room with it, but in the next room with the door shut shouldn't bother anyone. Especially since this will be operating on 24 hour duty cycles.

Tomorrow I will start with the first bagging experiments and share a few more photos. Maybe it won't be as intimidating as I'm imagining. Let's find out :cool:
 

All_In

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Watch a few videos it's easy if you have no leaks it uses tons of air pressure to make a perfectly smooth surface. Mix correctly, notice the temperature, and no folds or wrinkles!

I expect you will do well. As you do with everthing else.
 

Brian Jackson

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Watch a few videos it's easy if you have no leaks it uses tons of air pressure to make a perfectly smooth surface. Mix correctly, notice the temperature, and no folds or wrinkles!

I expect you will do well. As you do with everthing else.
I appreciate that vote of confidence, John. Thank you. Yes, making good use of YouTube and forums. It seems there are as many methods and variations thereof as there are fabricators. Some involve vacuum bagging, others do not. Gel coats are another thing I lust learned about. Much to digest, but I will heed your advise and pay special attention to the things you mentioned. When you said "notice the temperature", were you referring to the ambient room temp or that of the epoxy reaction? I assume the latter. Either way, how does heat affect the process besides cure time?
 

All_In

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That's it cure time changes with some much faster than you can remove wrinkles.
If you can paint you can do gel coat. I love vacuum bagging and have had to gel-coat boats I helped build when I was practiced at painting cars, boats, planes, etc for myself and friends. It much thicker and like to run.
Not sure if the new gel coat today it was much harder for me to get an even coat. So more thin coats for me without runs... not like a pro gel coater.
 

All_In

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I would have to practice all the curves and corners A LOT before I would do it today unless they have much better materials more like for students and not pros.
 

Brian Jackson

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Tangible progress today. First epoxy trial scheduled for tomorrow. Plumbing complete but sharing a few things learned along the way for other noobs like me to this.

1 teflon-tape.jpg
There were two different directions to go with plumbing: flex hose with plastic valve, or copper pipe with brass valve. I opted for the latter because the suction port of the pump is threaded for 1/4" NPT. It's also prettier and mechanically predictable. Teflon tape isn't sticky in the Scotch Tape sense. It's self-adhering but requires a minute to understand the rules it abides.

2 tape-wrapping.jpg
To minimize leakage and possible pregnancy, Teflon tape is wrapped around the male end.

3 tape-trimming.jpg
A pair of scissors did an adequate job of trimming off the overhang, but I may be on kosher meats for a while.

4 wrapped layout.jpg
All parts teflon wrapped and ready for assembly. I may add the gauge to this later but keeping it simple for now. When looking at this image it would appear everything is A-OK and ready to go. You would be wrong. Turns out the direction the teflon tape is wrapped makes all the difference in whether it stays on the part. If wrapped counter-clockwise it will roll up and delaminate. So Murphy's Law prevailed here. On the plus side, this gave me twice the experience and I got kinda good at it.

5 plumbing-assembled.jpg
The finished riser.

6 plumbing-hose.jpg
Reflecting back, I recall a greater sense of intimidation about tackling composite construction. Suddenly this doesn't seem so insurmountable. It's about systemically dismantling the magic. I'm going to give some thought into demonstrating why all I'm really doing is making a really big clamp.
 
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Brian Jackson

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Hello All.

Making use of the quarantine time. Sorry the build postings have been scarce recently. Have some composite tests from earlier postings to share here later but first I wanted to take a big sigh of relief after 2 parts got completed today. They are the vertical strut couplings that mount to the shocks. A bit of a convoluted operation that involved cobbling together a sturdy offset jig for holding the part rigidly without scratching it on the milling machine.

lgcb-1.jpg
Plexiglass has proven to be a wonderful separator that grips surprisingly well without leaving marks on the part.

lgcb-2.jpg
Side view of jig. Lower angle has hole that holds tenon of part in place. The cutter is a boring head that uses a screw-driven dovetail slider to offset the bit to the desired bore radius. Took some practice on scrap material, and a bit finicky with chatter at certain speeds and pressures. You kinda get a feel for it though.

lgcb-3.jpg
The lower clevis of the shock was removed to expose the threaded interior. The part to the right (coupling) has 3 stair-stepped counterbores that didn't show up well in this photo. They mate perfectly over the shock. The flat end of the shock connector is going to be milled down a couple thousandths to ensure planar seating on a Mil spec steel washer which will sit at the bottom of the deeper counterbore. This is the point that will take all the compression load. There is a 1" long threaded plug that gets inserted into the open shock end, and held from rotating by a set screw in shear. The plug has a hole through its center that accepts a 5/16' dia. socket head cap screw (not shown). The screw is inserted from the tenon end of the coupling with a long allen driver. The threads that go through the plug are formed by a non-cutting tap of the type used with rolled threads. The central bolt is the sole connector that unitizes and tightens the assembly.

lgcb-4.jpg
One of a matched pair. This took entirely too long but it's done now and I never have to think about it again. Check that off the never-ending list.
 

All_In

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Wow, you do excellent work, my friend!
 

Brian Jackson

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Wow, you do excellent work, my friend!
Thank you, John. Was hoping the tone of my last sentence didn't reek of frustration, but it sorta did. Many of the parts so easily drawn can be so difficult to make. This build has been about perseverance. Some days the finish line just seems so far away.
 

Resasi

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Thats a lovely piece of art Brian, possessing both form and function.

It is inevitable that frustration, and sometimes a degree of despair, seems part and parcel of a build. Life never does run smooth and there will always be hiccups, sometimes coughs and sneezes...and worse... to get in the way. It does however make that final accomplishment all the sweeter when it is done.
 
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Manchego

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Jul 8, 2016
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Congratulatios for your new project, Bryan.

Can I ask you what technique do you use to finish/remove the scratches on the plane cut? In other words, how to pass from pic1 to pic2.

I have been trying several techniques, however, I always end up deforming the saw cut -when I put a square to check the result I see the backlight leakeage in some points-.

I know it is just a cosmetic think, but it drives me mad.

Thank you. Keep it up!
 

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