• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Giant Rocket Glider (or how I demonstrate my total lack of common sense)

FAI-F1D

Free Flight Indoorist
#1
I built this cute rocket glider a while back, and it flew nicely...

Then I decided to be a stupid idiot and make a bigger one.
IMG_20181113_181657709.jpg

Ok, to be a little more serious, here are some details:
Root chord is 10.4", with a 3/8" thick sheet balsa wing for 3.5% airfoil thickness (probably a little on the thin side).
I'm using a fiberglass 29mm motor mount which can fit E-F Estes motors and F-G Aerotech composite motors. Still yet to arrive is a fiberglass nosecone (can't use plastic as the captive nose mount would cause the nose cone to melt from the ejection charge).
Tailboom will be a 1/4" carbon arrow shaft.
Wing area is about 500 sq in. Oh yeah.
Trying to keep the weight under 16 oz. I'm a little worried about that bit. Estes F motors only put out about 5 lb of mean thrust, so the model needs to be kept to about 1 lb for a safe launch. We shall see...

Plan view of this madness:
2018-11-09 13_19_31-Switchblade Super_rev2.skp - SketchUp Make 2016.png
 

FAI-F1D

Free Flight Indoorist
#2
I finally started cutting parts last night. Got all the plywood bits finished, but I'll need to go back and re-do a few because the 3/32" ply is just flat out overkill for some of this, and I need to keep the tail relatively light.

IMG_20181114_215147913.jpg

Another size comparison. This thing is huge!
IMG_20181114_205522821.jpg
 

FAI-F1D

Free Flight Indoorist
#7
Thanks guys. :)

I made a lot of progress over the past few days. I cut new ply parts for it from thinner ply since the 3/32 was gross overkill.

Got the wings planked out and got an idea of how massive this thing is going to be. WOW!
IMG_20181117_230452817.jpg

Next, added the trailing edges and cut them to shape. I'll trim the rest of the outlines later.
IMG_20181118_141315052.jpg

The wings are hinged to provide dihedral after deployment. I cleaned out a cabinet to weigh them down while the epoxy cured to bond the kevlar hinges in place. Had a slight delam on one that was fixed easily by wicking in some CA. The motor tube was bonded on using epoxy as well.
IMG_20181118_153201713.jpg

Now I just need to shape them and what not, but this gave me an excellent opportunity to test the wing deployment with a mildly too weak rubber band. Shock loads were minimal, so I can use more tension and not worry about damaging anything. That's excellent news as I was really concerned about the possibility of needing foam rubber in there.
 

FAI-F1D

Free Flight Indoorist
#9
Got some more work done last night. Wing outlines are cut to shape, tail sanded and installed, and wing dihedral bevels cut.
IMG_20181119_214502050.jpg

IMG_20181119_214555726.jpg

Hopefully I'll finish it off tomorrow and be ready for a test flight. My launch railing came in yesterday, so I have something to stabilize it up to speed.

Now is where it gets scary. This model is 21 oz as it stands here. It's probably going to lose weight when I airfoil the wings, even taking into account adding the nosecone and release mechanism, so it's the heaviest now that it could possibly be. The problem is there's no way this thing is dropping under 1 lb, and I still haven't balanced it. If it doesn't require any ballast, there's a chance for a takeoff weight of 21 oz (F15-4 weighs 2 oz loaded), but it could go over, and that's really marginal. I think I can get away with just rigging a piston launcher to accelerate the model faster, but another alternative is to tape a C6-0 to the motor pod and cluster it. It would stay well within the 80 N-s limit even then. Another alternative is to see if someone at next weekend's launch has a F20 or F22 on hand. Time will tell. Weather permitting I'm going to maiden it at our house in a few days, and that leaves me firmly stuck with the F15 platform. This could get interesting. o_O
 

JTarmstr

Well-known member
#10
Got some more work done last night. Wing outlines are cut to shape, tail sanded and installed, and wing dihedral bevels cut.
View attachment 118919

View attachment 118920

Hopefully I'll finish it off tomorrow and be ready for a test flight. My launch railing came in yesterday, so I have something to stabilize it up to speed.

Now is where it gets scary. This model is 21 oz as it stands here. It's probably going to lose weight when I airfoil the wings, even taking into account adding the nosecone and release mechanism, so it's the heaviest now that it could possibly be. The problem is there's no way this thing is dropping under 1 lb, and I still haven't balanced it. If it doesn't require any ballast, there's a chance for a takeoff weight of 21 oz (F15-4 weighs 2 oz loaded), but it could go over, and that's really marginal. I think I can get away with just rigging a piston launcher to accelerate the model faster, but another alternative is to tape a C6-0 to the motor pod and cluster it. It would stay well within the 80 N-s limit even then. Another alternative is to see if someone at next weekend's launch has a F20 or F22 on hand. Time will tell. Weather permitting I'm going to maiden it at our house in a few days, and that leaves me firmly stuck with the F15 platform. This could get interesting. o_O
Wow, one thing about the composites is they react far more violently then black powder. i hope you have a bunker or something to hide in when you launch that.
 

FAI-F1D

Free Flight Indoorist
#11
Wow, one thing about the composites is they react far more violently then black powder. i hope you have a bunker or something to hide in when you launch that.
Not planning to fly composites at the house for now, although most of the ones we run for gliders are long, slow burns. I'm planning to launch a few gliders on Aerotech E6 reloads at FFO next year, and those are really calm motors.

Saturday we'll be flying from a traditional NAR flightline, so it shouldn't be an issue anyway.

Moving on...I got both wings planed out last night, and the right one completely finished. There's 1.6 oz of shavings, all from a single wing, in this photo:
IMG_20181120_203617762.jpg

And here is the finished right wing atop the as yet sanded left wing, showing the dihedral tensioner:
IMG_20181120_224755596.jpg

Looking really nice at this point, and now nearly 4 oz lighter than before:
IMG_20181120_224748207.jpg

I should have it finished up tonight, since all I need to do is sand that left wing, install the locking mechanism/nose, and add rail buttons. Oh, and make a piston so it actually clears the rail at a safe speed.
 

d8veh

Well-known member
#13
Don't forget to get the pussy cat clear before you press the button. I've jost lost mine, so I'm heart-broken. You wouldn't want to suffer the same.
 

FAI-F1D

Free Flight Indoorist
#18
I posted this excited photo on Facebook on Saturday, right before the adrenaline drained out of me and I found myself absolutely exhausted...
IMG_20181124_134441290.jpg
None of that exhaustion mattered...

At GRITS 2018 on 24 November 2018, Fliplock F left the pad on its first public flight, powered by an Estes F15-4. It performed flawlessly in every way, milking every second out of the damp air for a total flight time of 75 seconds, which establishes a new NAR record in F Rocket Glider.
2018-11-26 10_01_39-We built a giant rocket glider! - YouTube.png

2018-11-26 10_02_37-We built a giant rocket glider! - YouTube.png

2018-11-26 10_03_12-We built a giant rocket glider! - YouTube.png

2018-11-26 10_03_38-We built a giant rocket glider! - YouTube.png

Here is a complete video roundup of the project, including the record setting flight:

So where to from here? Well, this model will be mothballed for a few months while I concentrate on other projects which have been delayed because of it. When I get a feel for dates for the next nearby NAR launch at a sufficiently big field, I'll work on fiberglass shielding of key areas of the airframe as well as investigating ways to reinforce it for more powerful motors. Options include testing to see if an Apogee F10-4 will be strong enough to lift it (lighter than an F15, and 60% more total impulse for a massive 8.5 second total burn) or exploring the necessary reinforcing to withstand an Aerotech F25 (same 60% impulse increase, but only a 3 second burn, so extremely energetic and rather dangerous to the airframe).

The G record is going to be much harder. The G12 would work, but I'll have to use altimeter-activated deployment since those are plugged motors. Altitude would be absolutely spectacular, that's for sure. G38s are almost out of the question. That's 3 seconds of power spent mostly at >5:1 thrust to weight ratio. Gonna be hard to survive that. Alternatively, I could cheat my way into G impulse by launching on an F10 clustered with an Estes C6-0. Time will tell which one wins...
 

JTarmstr

Well-known member
#19
I posted this excited photo on Facebook on Saturday, right before the adrenaline drained out of me and I found myself absolutely exhausted...
View attachment 119224
None of that exhaustion mattered...

At GRITS 2018 on 24 November 2018, Fliplock F left the pad on its first public flight, powered by an Estes F15-4. It performed flawlessly in every way, milking every second out of the damp air for a total flight time of 75 seconds, which establishes a new NAR record in F Rocket Glider.
View attachment 119225

View attachment 119226

View attachment 119227

View attachment 119228

Here is a complete video roundup of the project, including the record setting flight:

So where to from here? Well, this model will be mothballed for a few months while I concentrate on other projects which have been delayed because of it. When I get a feel for dates for the next nearby NAR launch at a sufficiently big field, I'll work on fiberglass shielding of key areas of the airframe as well as investigating ways to reinforce it for more powerful motors. Options include testing to see if an Apogee F10-4 will be strong enough to lift it (lighter than an F15, and 60% more total impulse for a massive 8.5 second total burn) or exploring the necessary reinforcing to withstand an Aerotech F25 (same 60% impulse increase, but only a 3 second burn, so extremely energetic and rather dangerous to the airframe).

The G record is going to be much harder. The G12 would work, but I'll have to use altimeter-activated deployment since those are plugged motors. Altitude would be absolutely spectacular, that's for sure. G38s are almost out of the question. That's 3 seconds of power spent mostly at >5:1 thrust to weight ratio. Gonna be hard to survive that. Alternatively, I could cheat my way into G impulse by launching on an F10 clustered with an Estes C6-0. Time will tell which one wins...
Congrats on the record! That must have looked awesome from the ground.
 

FAI-F1D

Free Flight Indoorist
#20
I've ordered some Apogee F10-4 motors for this rascal. Comparing the F10 thrust profile to that of the F15, I find that the F10 actually stays above 15 N longer than the F15, and follows that up with a heck of a long burn, remaining around 9 N for the remainder, which is enough to keep it pointing up for the remainder. The impulse being 74.3 N-s, I'm going to slap a B6-0 on the side for some extra oomph on takeoff.

This sets the stage of course for my next hat trick which is that as soon as that flight is over, I'm going to load back up and put a C6-0 in that side pod to push it into G class and go after that record while I'm at it. Given the long burn and lower percentage of total time before deploy spent nose down waiting for the ejection charge, I'd be willing to bet it does close to 3 minutes in both configurations. More if there's any lift. And if it's windy, well, we're not flying, even though I've launched this thing in 15 mph winds without it weathercocking on the F15.