Vulcan: L1 cert glider

I glue balsa trailing edges to the foam and sand them to shape. I cover the trailing edges and foam with fiberglass strapping tape.

I laser-cut flames out of red gift-wrap paper and use an exacto knife to cut 4 3/4" squares out if black gift wrap. This paper is very thin, conforms easily to the single-curve wire-cut shape and is--I'm discovering--a pleasure to work with.

The flames on top are only a mockup--I need to put in the leading edge stripe first. The black squares are on for real.

Ari.

The patterns look gorgeous. Can you say anything more about the epilog device shown in the pictures?

Thank you for your compliment Aerostadt. The device is an Epilog Helix 45W laser. There are some specs here: https://www.epiloglaser.com/legend_helix.htm . It lives at Sawdust Shop in Sunnyvale, Calif., where I pay $80 a month to use all of their tools including some really fancy saws, the laser and a ShopBot CNC router. https://sawdustshop.com/

Ari.

Looking good so far! Will this be making its way to a LUNAR launch any time in the near future?

I really want to fly it this Saturday.

Ari.

Darn, I'm missing this Saturday's launch. (Bithday parties and other commitments...)

Hope you get it done in time and have a good flight!

Well, what I really want to do with it is my L1 cert. I think you and I are aiming for the same date for these. Assuming Vulcan survives Moffett this Saturday, October Skies looks promising.

Ari.

I might be able to get my KK done in time for the Cub Scout Rocket Jamboree event, but I think I'm going to hold off on the cert flight until the next Snow Ranch Launch.

I hope the Vulcan survives. I am planning on coming to October Skies and I'd love to see it in person there! I've been inspired enough by the thread to clear off my workbench and start building my Gamma Star kit.

Mike

I have word that the LUNAR launch this Saturday is off. I might launch at SCCMAS instead. If anybody is around this Saturday or Sunday, I can use some moral support! Also, someone to take pictures.

The Gamma Star is a beautiful ship! I would very much like to see yours fly. More RCRGs means I feel less extravagant at a launch.

I'm complete on covering the wing. This is the first time for me using the "New Stuff" laminating film. People say it doesn't shrink at all. It shrinks some, but a lot less than regular iron-on films like Monotote. I find that I need to make numerous "de-pleating" cuts, such as on this end-plate. The good news is that since the wing is wire-cut, the only compound curves are on the seams between panels and on panel ends. The panels themselves are probably easier to cover with this low-shrinking film.

The material does have some very interesting properties. It comes from the roll frosty and clears up with heat. This gives a clear indication of areas that are on already and ones that still need work. Third photo shows me just starting on a panel--the middle is clear while the rest is still frosty. It's a lot thicker than Monocote (5 mils I think) and adds a tremendous amount of rigidity to the wing. Between the fiberglass tape and the film, it feels as strong as glassing.

The wing is now complete. I still need to hinge ailerons and flaps, servo linkages, radio gear and nose with nose weight (looks like I need about a pound of it)

Completion is in sight.

Ari.

All four control surfaces are now in place. Slotting ailerons for CA hinges is like slotting airframe tubes for TTW fins, and about as much fun. 4 surfaces, 3 hinges per surface, 2 sides per hinge... 24 slots. But they are all complete now.

The outboard ailerons (I think they are going to be elevons) are complete with servo linkages and horns. The inboards are waiting for me to buy another piece 2-56 allthread that I use as pushrod. The inboards are going to be either straight flaps or flaperons, I'm still working that out. It may be hard to see in the photos, but inboards are wider than outboards: 1 5/16" vs. 1": this accounts for wing taper. As a fraction of the cord, outboards are still larger than inboards.

I trim servo wires to length and crimp female Molex pins on them. 3 wires x 4 servos... I'm out of plastic housings, which makes it difficult to plug these wires into a receiver without shorting something. On my shopping list for tomorrow. I label the cables for (I)nboard/(O)utboard and (L)eft/(R)ight to simplify configuration once I can plug them in.

Ari.

I look at my elevons now that they're on the wing, and worry about having enough elevator authority. Their area works out to about 4% of the wing.

Ari.

If you need nose weight, make the control surfaces bigger.

What kind of foam are you using? Great looking project.

Eric

Have you tryed comparing the weight of fiberglass and resin vs the paper, glue, and laminating film?

@clipper: I have made no such comparison. My emphasis is on ease of application more than on ultimate weight. Now ease is a subjective thing. I know people who say that fiberglass and vacuum bagging is easy to do for a nice even layer. I have no experience with vacuum bagging but plenty with paper and covering irons and have a laser handy.

Ari.

iter said:

@clipper: I have made no such comparison. My emphasis is on ease of application more than on ultimate weight. Now ease is a subjective thing. I know people who say that fiberglass and vacuum bagging is easy to do for a nice even layer. I have no experience with vacuum bagging but plenty with paper and covering irons and have a laser handy.

Ari.

Click to expand...

The rocket gliders I've build have been smaller and as simple as possible- eps foam flyingwings. So far, I have never found the need for bagging. I pre wet the glass on paper and when I lift it off, the excess epoxy is left behind.

Eric

Thank you for sharing your process Eric.

Ari.

Controls surface setup is complete.

[video=youtube;5tE1j5M6fHM]https://www.youtube.com/watch?v=5tE1j5M6fHM[/video]

The left stick operates inboard flaps and takes care of transition from boost to glide, as well as trimming for best glide speed. It also controls my remote ignition system (on a separate receiver). This setup guaranties that I can only ever ignite the motor when the flaps are in the take-off, zero-lift position. I mix a small amount of aileron into the flaps. The outboards are elevons and are the primary control surfaces during glide.

Ari.

Are those surfaces relatively the same proportion as your smaller version? They look small to me, but my stuff usually is very light and large and flies slow so I have to push a lot of air....Just curious. The original had full span I think and were sized about 1/6 of the chord this looks much smaller, depending on CG, if nose heavy I worry about being able to keep it nose up.

Frank

Yes, I worry about that, too, as a previous post says. Now as far as your observations: Vulcan has full-span surfaces, they are just on on different channels. The outboards are elevons. I might mix a little flap into the outboards as well, to reflex them slightly for glide. The previous iteration of the glider is way too squirly. I have the rates down to 30% with a lot of expo and it's still hard to control. That little glider has way too much control surface. My intention is to keep the CG where it belongs, rather than making the glider nose-heavy and countering with a bunch of up elevator. These gliders are heavier, have real airfoils and go a lot faster than flat depron foamies.

Now with all these observations, I still worry about the control surface area. My difficulty is that I'm using CA hinges. Once they go on, I don't know how to undo them to replace the surface.

Ari.

iter said:

My difficulty is that I'm using CA hinges. Once they go on, I don't know how to undo them to replace the surface.

Click to expand...

You could try soaking them with debonder and tugging them out. Or you cut them and then make new slots.

kj

Roll isn't probably an issue, I was more worried about pitch, you may want to run a slight bit nose heavy to tame out the squirreliness if it was in pitch and use upsized surfaces till you get it all sorted out.

Frank

iter said:

Yes, I worry about that, too, as a previous post says. Now as far as your observations: Vulcan has full-span surfaces, they are just on on different channels. The outboards are elevons. I might mix a little flap into the outboards as well, to reflex them slightly for glide. The previous iteration of the glider is way too squirly. I have the rates down to 30% with a lot of expo and it's still hard to control. That little glider has way too much control surface. My intention is to keep the CG where it belongs, rather than making the glider nose-heavy and countering with a bunch of up elevator. These gliders are heavier, have real airfoils and go a lot faster than flat depron foamies.

Now with all these observations, I still worry about the control surface area. My difficulty is that I'm using CA hinges. Once they go on, I don't know how to undo them to replace the surface.

Ari.

Click to expand...

Hi Ari,

Has Bob Parks looked at them? I would say do a glide test and if you have pitch control your roll should be OK. Seems like roll is never a problem in deltas.

But I will say by eyeball they don't look big enough.

Don't try to pull the hinges out, you could either scab something onto the existing surfaces to increase their chord (not elegant) or cut the surfaces off and re-hinge them, just put the new hinges next to the old ones.

Here's Bob's response, just in over email:

They look a bit small. You can compensate for small by having a bit more angular throw, but anything past 30 deg each way does not add much authority.

You do have the inner flaps available as extra pitch trim surfaces, which is good.

If you really want more area, can you just splice on some more wood to the TE of the existing surfaces to increase the chord of the surfaces? (maybe trim the existing TE back if its really thin right now)

The issue here is that you might run out of pitch authority, particularly if the CG is forward (and it will be a bit for glide). I would not want to go to less than 5% of MAC stability margin. (CG at 20% MAC). That would be aft most location for boost. If the CG shifts to much more forward than 17% or so, I would be very concerned about the small surfaces.

Personally, I would do mixing so that all 4 surfaces move as elevator.

Bob

Click to expand...

That confirms what I was thinking as well. You could laminate some thin ply or styrene on top of your current surfaces till you get it working well, again, too much response is difficult to fly, but not enough response is impossible....

iter said:

Here's Bob's response, just in over email:

Click to expand...

Yes, I would kust scab something over them, maybe increase the surface width 30% or so.

I would worry about enough pitch authority to flare, I found deltas a real compromise, but they have their advantages (strong, easy to build, simple)

While I'm figuring out control surface area, I'm also working on the weight and balance.

If I plug a nosecone directly into the wing, I need a pound of nose weight. I can plug an extra foot of BT between wing and nose cone, then i only need half a pound, but it looks ridiculous. That, and higher chance of breakage on landing. It's tempting to put a full-flying canard on the BT extension, that way I can solve balance and control issues simultaneously--would look kinda like XB-70. But I'm too lazy to design a whole linkage system.

Ari.

I'm giving the canard a more serious thought. The yellow bit is a stabilizer from a random defunct airplane in my collection, and is only a rough idea of the size. Yellow is out of place, too. And I'm unclear on how to mount it--where it's sitting now it interferes with the launch rod; if I put it under the BT, I'm likely to shave it off on landing, and too lazy for TTW construction with servos and linkages.

Ari.

Could you mount the canard on top of the tube as shown, then mount the launch lug on a small stand off? Lazy or not (I understand your pain, I'm the laziest guy on the planet) you may be stuck with a TTW mounting of the canard mid tube, much like the canard on the XB70....

Launch lug is 3 feet long, integral with the wing and 1/16" off the main BT. There's no moving it now :=) You can see it in post #41 if you scroll up. It comes out the other side under the base of the fin.

Ari.