OK, so the name is a bit lame, and if it doesn't fly right, then it's laughable to call it a master of anything...

Anyway, this is an internal-pod style of BG, and I think the CG points for both boost mode and glide mode are in their correct places. YMMV. Always trim the model for glide first, and then for boost. If anyone happens to try this before I do, let me know!

Specs:

Length: 24.232" (Glider alone) , 25.732" (With boost pod)
Diameter: 1.04" (ST-10)
Wing Span: 12.54" , 10-degrees dihedral
Weight: 1.28 oz (Glider alone) , 5.18 oz (With pod, loaded with D10-5)


D10-5......1000' Average......Dv 26 FPS Average......36" x 1/8" rod


Don't try this with a lesser engine. A C6 needed 100" of launch guide to reach safe flight velocity. It's heavy, but it also has a high drag with all of that wing area extending into the breeze. The margin with a power pod and D10-5 is 1.10, which should be sufficient.

Study first, then Enjoy!

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Sky Master BG.rkt (65.1 KB, 64 views)

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SAM 0044
AMA 352635

That looks alot like some of the 'profilish' sorts of gliders I have done over many years. Seems that you have designed this around an 18mm pod inside a BT-50ish tube. Also, if I am reading your RockSim stats correctly its showing this overall weight at over 5z? Yikes! Is this why you only show a D10 as the sole motor here?

What I would do, and probably might just for the heck of it (see also Marpe and his 'E9 gliding BT80 Bomarc and make it glide over a minute deal) and see whats really doable here.

Off the bat, I would replace the BT50 main tube with a 55, and make it use a 24mm pod so a D12 is best. How many people even have/use D10s?? Also, Id consider making this a bit larger overall (perhaps 35% so) if possible. Heck, this would then be good for using good old ReadiBoard for a quickl and easy build.

I would also kludge the tail to have a single horizontal stab atop the main tube, so you can have one elevator right up there, ala SkyDart or Bomarc, and easily work this with a bent paper clip taped to the pod tube. Easy stuff, and reliable.

If I have the tubing to spare, I will make one of these, likely at a 35 to 50% overall upscaling, so it can end up at both a good size and weight for a D12 and E9.

Like I need any more ideas for larger glider building......

AM, the design is ST-7 for the pod, and ST-10 for the main body. It's a tube that I'm becoming quite fond of. I just like the feel of ST-10 better than BT-50...

The 5 oz weight was loaded with motor, but another part of this was a mass of almost 2 oz at the front of the pod to achieve the boost margin. It will drop out with the pod at deployment.

I thought about a stabilizer on the vertical fin, but I was trying to keep the glider simple and without any moving surfaces. Common toss-gliders have no moving parts, and still fly great, so I figured this one ought to fly the same. Getting the balance right on the glider was more critical than on the pod, and may still take some positioning of the wing before a 'final' version is ready.

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SAM 0044
AMA 352635

Yes, I noticed you using Centuri tube sizing, but these are still correlative to a Bt20 pod in a 50 main tube.

Also, I knew that the high overall weight had to consider a goodly chunk of pod mass up front, and I know all about how much this can be, as my largest glider of all time needed 5lbs to properly hit the boost CG. However, on something this small, its hard to get two ounces of anything in the end of a BT20 and keep it from crimping the tube upon recovery. Its much easier to just go with a 50/55 setup (or your Centuri equivalents here).

So, you want to do this with no moving parts? That is probably somewhat doable, since this does have a 'convieish' aircraft wing/horizontal stab configuration. However, you will require some incidence in said horstab, and in turn, need an even more forward boost CG. What you are showing on your RockSim model is NOT likely to work.

'One caliber stability' as modeled is fine for 3FNC rockets, but never for gliders such as this, especially when you have both the CP and CG only an inch apart on the main wing surface! I think you would have to have your boost CG at the wings LE or darn close, and this means more pod mass, totally eliminating any good boost from an 18mm BP motor.

Also, you can add some decalage by just bending in the horstab tips diagonally, such as done on an Astron Nighthawk or such, winding up with close to half the area on each stab so affected a tad. Just enough to be able to trim out a glide, and to recover from any dive at transition, but not enough to cause a pitching arc in boost. Real forward CG tends to help here.

Now that youve mentioned this is intended as 'no moving parts' I may try to do my larger version as such. I see a lot of lead in my future......

I think I understand a parallel to what you're saying. I actually had a K-19 clone that flew well, only because I introduced downthrust in the engine pod. The thing would back-flip into a power-prang every time without it. The downthrust keeps the nose pointed in the right direction, opposing the lift of the wing while the model is under power.



Just like a "Zero-Length" launcher back in the '50s for the Air Force...



I think I can work this aspect into the design easily enough. As for the balancing act, I know that most aircraft fly with their CG at about 25% MAC, and even aerobatic aircraft don't usually go beyond about 30-33%. I tried to get the CG at about the 25% mark on the glider first, meaning the glide aspect should be close to that of a trainer airplane. This was a simple adjustment of the wing location. It was interesting that the CG and CP were almost perfectly lined up on the glider.

The power pod is going to be the bugger in this design, no question. I'm not happy with the length of the pod, as I worry more about the pod hanging in the fuselage than I do about the mass required to balance. Nothing is yet etched in stone, and I'm still learning my way around BGs. I was hoping someone would chime in and give me some pointers. Thanks!

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SAM 0044
AMA 352635

Thanks to AstronMike for his input on BG operations!

So, here's an updated version using a pop-pod at the top-front of the glider. It requires no ballast, and a B4-4 provides adequate lifting power to get the model off a 36" x 1/8" rod. I'm not familiar enough with the construction of the pod attachment to show it on the plan. I do show an angle in the top edge of the pylon, which needs to be set at about 2-3 degrees pitch.

The rudder (on this plan) may be in the flame path, so I'm thinking about revising it again with smaller twin rudders. I'm open to comments on that...

Specs:

Length: 22.5"
Diameter: 1.04" (ST-10)
Wing Span: 12.54" (10-degrees dihedral)
Weight: 2.12 oz (loaded with B4-4)


B4-4......358'......Dv 17 FPS......36" x 1/8" rod
B6-4......359'......Dv 14 FPS......36" x 1/8" rod
C6-5Q.....688'......Dv 30 FPS......36" x 1/8" rod


Study and enjoy!

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Sky Master BG MkII.rkt (53.9 KB, 63 views)

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SAM 0044
AMA 352635

Well, that front podded version now looks funny, and of course necessitates a pylon to stand it off from the wing. Even then, you may end up getting some real cooking on the aft parts of the planform.

I still think that doing this with good old rear ejection is the way to go, unless you get a flat bodied profile version front podded instead. Sounds like this is an entirely different animal, and a bit unsatisfying, as you do need a BT on the glider to make it look 'real' enough.

Another idea, although this results in a less attractive during glide model but is inherently LOTS easier to do is to make it eject a *forward* section and nose cone like I do with some of my designs. BrianC on here has seen me do this with some larger stuff, and he himself has gotten one of my kit prototypes to do well enough (see NEFAR videos and Astron Triple Eagle).

The way this works is you just glue in the motor mount in the rear of the glider as if were a stinkin' 3FNC rocket. YOu then make a long enough forward section, with a weighted NC as far forward as you can get, and have this simply eject on its own chute/streamer. YEs, this makes for an open tubed vehicle gliding back, but this in no way makes for a poor performer. My own designs have done very well using this method, and ironically, this was used on the last two J powered gliders I flew back in 96 and 97.

Mechanincally speaking this is far easier than any other method, and since you are ejecting the forward section, you can make it long enough or add wt enough till you have a dead solid boost CG. Now......as far as glide trim goes......remember, you now have the MMT and a burnt casing in the rear, so you must glide toss with those included. This may necessitate some forward mass on the glider itself, or make its BT a bit longer if you can. Once again, this method works better as you scale up, and the only real 18mm design that likes this way is my old version 'Astronized' Invaders. Yes, it was also a 52" disc, with like 4lbs of steel in the forward ejected section to ballast this for boost on a J350. Worked fine, too bad that 'model' got lost along with many others back in the '04 hurricane season here.

So, it appears we now have three or four different ways to approach this. What I may do is to make the upscaled wing planform and add this to either a BT55 or 60 but not glue in the MMT yet, just sort of 'put' it in there and check the CG without a NC. IF this shows a good close glide CG, then I will 'invaderize' it from that point. If not, probably do it as rear ejection.

Now, if we use 6" sonotube.......