Rocket Powered Balsa Glider

[JohnNGA]

I tried to use a Jetex 50 on the bottom of a glider long time ago...it caught fire, wish I still had that Jetex.

 

[EeebeeE]

We'll see what happens with this one tomorrow. OUr club is launching and I made a second, less finished one that I can use as a prototype. Spent most of the day installing a timer in my Mad Cow Fiberglass Arcas. Flying it on a J600 dual deploy and I normally leave the motor ejection charge in for redundancy, but this rocket will coast upward well past the delay of the rocket. Instead I will use the timer to deploy the drogue 1-1.5 seconds after apogee if the altimeter doesn't do it. Going for Mach 1.

 

[EeebeeE]

Launched the prototype into the wind today. We had a 15mph wind. I waited until the end of the day. It was a hoot. It looped 180 degrees and and then the wings ripped off. It "flew" another 100 yards at about 100' off the ground and then came down. No one was hurt. A bunch of people laughed.

 

[Mike TG]

I agree completely, people here need to lighten up a little. Sure there is a safety risk when trying new things, but you can also break your ankle falling out of bed. I made a rocket glider back in elementary school. It was an F4 Phantom comprised of foam wings and a foam/wood sandwich for the fuselage. All flat pieces like yours, but 3-d when assembled. My dad took me to a hobby shop that sold them in various imitations of popular planes- The Thunderbirds, Blue Angels, Etc. Anyway, I stuck a motor mount tube under the fuselage where the wings meet, and just balanced it by hand. Under power, guess what happened? It looped! Then the motor ejected (without a streamer-what a crime) and it glided perfectly to it's final resting stop atop the Miami Lakes Barn, Thanks Graham! No one got hurt, and everyone laughed and was impressed. Only problem, The barn roof. Would have launched it 100 times, if it were still here. I say go for it again to get your video, just beef it up so's it survives thrust! Oh yeah, maybe cant the motor to counter the loop. No Biggie. I say, so what if it hits someone. If they are at the launch, they should be looking, and if it hits them, it most likely won't hurt anyway.

 

[FastCargo]

I agree completely, people here need to lighten up a little. Sure there is a safety risk when trying new things, but you can also break your ankle falling out of bed.

Yes.

I say, so what if it hits someone. If they are at the launch, they should be looking, and if it hits them, it most likely won't hurt anyway.

No.

As a responsible person, you should take reasonable precautions to prevent such an occurrence. If you suspect a model is going to have stability issues, best idea (if you can't determine its stability beforehand) is to do a solo launch. Otherwise, you're setting up for someone to get hurt, or at least have a bad opinion of you or the hobby.

FC

 

[EeebeeE]

Whenever possible, risk should be minimized and we did so here. The reality is that the vast majority of people who post here are safety conscious, and you can generally tell the few who aren't as well as the trolls who want to stir up trouble. We all want to be safe and have fun. You CAN have fun with off the wall designs and still be safe about it.

Rather than "calling 911" when you see a safety issue, just politely ask. Chances are, the person who made the post has considered the safety issue. In the oft chance they haven't they will appreciate the suggestion.

 

[Gus]

Evan,

I'm sure you're a nice, fun guy, but this thread is a prime example of why so many really experienced rocketeers no longer post here. You had an interesting idea and posted a question, "think it will work?" You got some rock-solid advice from people with a ton of experience and ignored all of it. Then those who tried to help you were criticized as "naysayers", people who just need to "lighten up".

Nobody here thought you were likely to kill someone with your little rocket. But there were a few here who understood very clearly your glider was no more likely to fly successfully than if one just glued a launch lug to a motor. It wasn't "experimental", or "pushing the envelope", it was just doing something very basic rocket science has taught us won't work, ever.

Just because you were using a "little" motor doesn't mean you "minimized risk" or had "considered the safety issue." Launching a rocket that is absolutely going to crash is never safe.

I can understand why Fred got frustrated in responding to you. If you have no interest in anything anyone tells you, why bother to ask the question in the first place?

 

[EeebeeE]

Actually Gus, I did take a lot of what was said into consideration. The rocket was launched at the end of the day when most everyone was gone except for a very few experienced people, and about 150' away from the nearest person. The wings were reinforced with tape as was suggested. We planned for the loop that we expected as a result of information from this thread. I did it at a club launch without taking a video so we could get a gauge for what it would do when we took one and I had less-experienced people present.

For the record, it did not have a "MASSIVE" crash. The wings shredded off, as was expected when the rocket was about 100' in the air. It was still under power and flew laterally for about 100'. After the motor ejected, the rocket came down nose first at about the same speed a Quark does after it ejects its motor.

The basic design had to remain, though because of the project for which it was intended.

I heard everyone, I really did.

We all just have to learn that 90% of all human communication is nonverbal and does not include words. It is best not to try to put your emotion into words without having someone see the rest of the communication your body is giving. Had Fred and I discussed this face-to-face it probably would have been a lot less confrontational. Sorry Fred if I upset you. I really did take what you said into consideration...just in a different way.

 

[shreadvector]

You did not upset me at all.

You did misquote me and change what I said. I said (and I quote): "Read the simple advice I already provided. If you put the motor under the wing you will have MASSIVE pitch up and a looping crash. "

I never said a "MASSIVE crash" as the rocket is not massive enough to have a massive crash. I emphasized the pitch up since you seemed to be ignoring that simple advice and also (in some later post) seemed to think that the position of the motor fore or aft could affect the pitch up moment caused by the motor thrust. This is simply incorrect and simple physics will tell you that a force times a distance will give you a moment. the force is the motor thrust and the distance is the normal distance between the motor thrust line and the center of gravity of the rocket or aircraft.

The wings generate lift (up) and to balance that most people put the motor on top to create a downward force.

It is a violation of the NAR Model Rocket Safety Code to intentionally launch a Modle Rocket that you know will crash. The NAR insurance folks would not be amused if there was any fire or injury caused by the debris hitting the ground or a spectator. You attempted to minimize the spectator risk, but you still launched something that was going to crash.

Actually Gus, I did take a lot of what was said into consideration. The rocket was launched at the end of the day when most everyone was gone except for a very few experienced people, and about 150' away from the nearest person. The wings were reinforced with tape as was suggested. We planned for the loop that we expected as a result of information from this thread. I did it at a club launch without taking a video so we could get a gauge for what it would do when we took one and I had less-experienced people present.

For the record, it did not have a "MASSIVE" crash. The wings shredded off, as was expected when the rocket was about 100' in the air. It was still under power and flew laterally for about 100'. After the motor ejected, the rocket came down nose first at about the same speed a Quark does after it ejects its motor.

The basic design had to remain, though because of the project for which it was intended.

I heard everyone, I really did.

We all just have to learn that 90% of all human communication is nonverbal and does not include words. It is best not to try to put your emotion into words without having someone see the rest of the communication your body is giving. Had Fred and I discussed this face-to-face it probably would have been a lot less confrontational. Sorry Fred if I upset you. I really did take what you said into consideration...just in a different way.

 

[EeebeeE]

It was not launched with the intention of crashing it.

I knew with a 1/2 A motor that there was a strong likelihood that the wings would most likely shred off, but at that point the rocket's stability would improve. The OR sim, showed the CP to be 1.25" aft of the CG with wings and about 3" aft without. With wings, it was a glider...without, it was essentially a bottle rocket except that it had fins because of the stabilizers.

So it can be argued, that though unconventional, shredding off of the wings and a tumble recovery would be an alternative to glide recovery. The flight proved that to be the case. Although there was no instrumentation to prove the landing speed, it did not come back to earth at a velocity that would have hurt anyone. You could have caught it in your bare hands.

If the wings did not shred off, it would have completed a 360 loop and glided to recovery. As indicated by someone else on this thread, that was possible as well.

Consider the Estes Quark, which has no recovery system other than to eject the motor. It comes back to earth nose cone first, hypothetically at its own terminal velocity. Are you therefore crashing it, or is the mass of the rocket so small that it can be considered recovery? That is the case with this glider.

I wish I could pull up the Estes kit I bought when I was a teen that had the motor configured the same way as this. It completed a 360, then leveled out at about 200', ejected the motor, and glided well. I configured this to be similar to the way that rocket was set up.That rocket did loop and I expected this one too both because of points you made and because of my experience in 1974-75.

I did not expect the glider to dive back into the ground because I felt it would come out of the loop the same way hand-thrown gliders to when thrown hard. The motor is positioned so that the thrust came from the same area where your hands would be if you threw it. To ensure safety of bystanders, it was launched so that the loop would be parallel to the flightline. I incorporated suggestions to using tape to reinforce leading edges. Had a 1/4 A motor been available I would have launched with it. One was not, so I used a 1/2A.

I do think that if packing tape us used on both sides of the wing and it is launched with the wind instead of against it that even though it will nose up hard at launch, it will perform adequately.

 

[JPVegh]

I wish I could pull up the Estes kit I bought when I was a teen that had the motor configured the same way as this. It completed a 360, then leveled out at about 200', ejected the motor, and glided well. I configured this to be similar to the way that rocket was set up.That rocket did loop and I expected this one too both because of points you made and because of my experience in 1974-75.

I don't remember such an Estes glider kit but if there was one you should be able to find it in the Estes catalogs at ninfinger.

 

[fulldec]

I'll take a crack at this. From what you have written:

You test launched a design where you knew with a 1/2 A motor that there was a strong likelihood that the wings would most likely shred off.

You expected this one to loop under boost like the one you recalled from the past.

You had no idea whether this one would loop and hit the ground or loop and clear the ground.

You had no idea at what point in the expected loop, the likely shred of the wings and expected conversion to a stable configuration would occur.

You had no idea what direction the model would be pointing when it became a stable flying object - up, down, sideways.

There was an option to use a smaller engine for the first test flight but expediency ruled.

Was there a great danger to those present? Maybe not.

Was this an unsafe practice? I'd say so, though I don't expect you to agree.

 

[EeebeeE]

Let me answer 1-by-1


You test launched a design where you knew with a 1/2 A motor that there was a strong likelihood that the wings would most likely shred off. - Yes, but the alternative configuration was more stable. We're not talking fins, here, we are talking rockets. Ultimately if the fins shredded off, the glider became a stable rocket.

You expected this one to loop under boost like the one you recalled from the past. - Yes

You had no idea whether this one would loop and hit the ground or loop and clear the ground. - Based on past experience the loop would clear the ground.

You had no idea at what point in the expected loop, the likely shred of the wings and expected conversion to a stable configuration would occur. - The shred would have occurred somewhere between launch and peak acceleration which for a 1/2 A2-3T would have been at approx. 50' off the ground based on the sims. The rocket would still have been pointing upward at that time. (I do like to dabble in physics).

You had no idea what direction the model would be pointing when it became a stable flying object - up, down, sideways. - The model would have been a stable flying object pointing up per the answer above.

There was an option to use a smaller engine for the first test flight but expediency ruled. - Choice was between 0.625 N and 1.25 N. 1 newton = 0.228 PSI. So the choice was between a thrust of 2.248 ounces per square inch or 4.496 ounces per square inch. The glider with motor weighed 1 ounce. Hypothetically, if you want a 4-1 thrust-weight ratio at launch for a rocket weighing an ounce, the 1/2 A motor was safer.

Was there a great danger to those present? Maybe not. - No they were at least 150' away and all were experienced fliers looking at the rocket.

Was this an unsafe practice? I'd say so, though I don't expect you to agree. - Considering we had evaluated all contingencies, and the most likely possible outcomes, that the momentum generated by this rocket was a fraction of that generated from a baseball thrown by a little leaguer, that no children were present, and that everyone wore facemasks and body armour (just kidding), this was safe.

Can the defense cross-examine the witness now?

 

[fulldec]

Yeah, I thought as much.

 

[EeebeeE]

I don't remember such an Estes glider kit but if there was one you should be able to find it in the Estes catalogs at ninfinger.

I remember buying it a a department store...not a hobby shop. It was billed as a quick build kit with preprinted parts. We had it in the air 45 minutes after we got home. From memory, below is a rough diagram. We flew it on motors up to C6-5's. Must have flown it 30-40 times without incident. Last time it flew it landed in our pond and disintegrated.

 

[WillMarchant]

I was thinking the K19 Invader https://www.spacemodeling.org/jimz/k-19.htm but I don't know if that was ever sold as a kit...

 

[EeebeeE]

Yeah, I thought as much.

Is that the best comeback you have? If so then I won the debate.

 

[billspad]

Are you thinking of this:



I never could get one to fly properly but that's the case with most of my gliders.

 

[EeebeeE]

I was thinking the K19 Invader https://www.spacemodeling.org/jimz/k-19.htm but I don't know if that was ever sold as a kit...

A friend of mine owned and invader. Cool rocket, but this wasn't it.

 

[fulldec]

Is that the best comeback you have? If so then I won the debate.

There was no debate. If you think you have won a debate on the internet, you are deluding yourself.

I was only trying to illuminate. I can see it was not worth the effort, sorry to waste the bandwidth.

Carson out.

 

[billspad]

Did you launch your glider straight up or at an angle?

A former NAR president was trying to explain the art of gliders to me and I believe he said that if you have a glider that pitches up a lot on boost you should launch it on an angle so that it will pitch up to vertical. Yours may loop too much for that to work but it may also get you high enough that the bottom of the loop doesn't intersect the ground. However, taking any glider advice from me is usually a bad idea.

 

[EeebeeE]

Did you launch your glider straight up or at an angle?

A former NAR president was trying to explain the art of gliders to me and I believe he said that if you have a glider that pitches up a lot on boost you should launch it on an angle so that it will pitch up to vertical. Yours may loop too much for that to work but it may also get you high enough that the bottom of the loop doesn't intersect the ground. However, taking any glider advice from me is usually a bad idea.

Launched it at 20 degrees...maximum allowable by NAR. It pitched straight up. It really did not do a power loop as most have suggested probably because it lost the wings.

 

[BEAR]

I had one of the Estes Space Invader gliders. It looped a lot on take off. This was during the time of the TV show The Man from UNCLE. I made a modified version with a clipped trailing edge. I called it the THRUSH Bird. It glided really well, but it would not fly worth beans as a rocket. Looped and crashed under power using an A8-3. I agree with billspad on the tilting of the launch rod. Of course we all realize the diagram depicted in your most recent post is not the same.

Gliders tend to have un-intended results. Private launches are the best for first flights. Safety is one reason, saving your pride is another. I have successfully found many ways on how not to build and launch a rocket glider. Almost 45 years worth of experience. When they do go right, it is so cool.

 

[gpoehlein]

Ok - I'm coming to this party late, but I thought I'd throw in my 2 cents anyway.

I decided to try this early in my "re-BAR-dom". I put a motor pod on the dime store glider. One thing I did different and would have made a lot of difference in yours was turning the wing upside down. You can offset a lot of the powered loop tendency by putting the motor "inside" the dihedral rather than opposite it. That might have helped the flight some. Oh, and I turned the wing upside down so the tail wouldn't be in the motor exhaust.

But the real issue is that the thin balsa used for these guys is REALLY soft. If I remember correctly, it held up to a 1/4A motor, but shredded under boost from a 1/2A. To fly with a 1/2A, tissuing the wing might help it survive boost.

 

[EeebeeE]

There was no debate. If you think you have won a debate on the internet, you are deluding yourself.

I was only trying to illuminate. I can see it was not worth the effort, sorry to waste the bandwidth.

Carson out.

You asked me eight questions. I answered each one in detail. And your response was "Yeah, I thought as much." I just think that is a lame and judgemental response. I took the time to answer you point by point and you chose not to hear me even though you were the one who asked the questions, and you just blew them off. Yet I was accused here of not wanting to hear what others had to say.

I have been flying rockets since 6th grade in 1970 and have made well over 1,000 flights. I have worked with Cub Scouts, boy scouts, and other organizations and have stressed safety at all times. There is a current post on the HPR forum and I have made comments regarding safety issues there as well. For instance, all my DD flights have some sort of redundancy to dramatically reduce the risk of coming in ballistic.

My last flight wen to 8,300+' over mach 1. Knowing the motor delay was not long enough, I installed a timer as my redundant apogee deployment to make sure that the rocket would have at least come down separated. When motor delays are long enough to leave them in,

I would not have attempted this unless I felt absolutely sure that no one would get hurt. I would not attempt it again unless I felt the same way. You weren't there. You have no idea what else I did to make sure this would be a fun safe experience. I was confident the rocket would go up safely and I was confident that it would come down safely. I did not willingly put anyone in danger.

And you know, even Estes feels the same way. You buy an Estes Quark, Mini Mosquito, or Swift and they all deploy the same way. "Tumble recovery." That's actually a misnomer because the original tumble recovery was a motor weight shift so that they would literally tumble. The airframe had a hole in it that once the motor passed, would vent out the ejection gasses and leave the motor aft, putting the CG at the fins which made the rocket unstable, slowing its descent. The three rockets I mentioned above eject the motor and come in nose down at their own terminal velocities. In effect, they come in ballistic. It is just that they are so small, their terminal velocities are slow.

Those who upsize the Quark 10x use different recovery techniques because for larger rockets, "ballistic recovery" which is the more operative description is dangerous and could cause serious damage. Even if you developed a recovery system for your motor, a 5' tall quark coming to earth nose down like the original could cause some serious damage.

You do have to factor in size for safety considerations, and that is an acceptable form of testing a new design according to the NAR. If you have a design that you are not sure of, one of the options is make a scaled down version and test fly it before you fly full-sized. It is in fact a question on the L2 exam. I chose the smallest glider I could find, used the smallest rocket parts I could find, and took all the safety precautions I could.

Just because people occasionally try something different doesn't mean they are unsafe. I was confident in my ability to do this safely. If you feel that you could not do it safely, I respect that, and would respect your desire not to make a launch. If I came to one of your club launches and your RSO would not let me fly it, I would respect that as well.

 

[EeebeeE]

Adding tissue or paper to the wing is something I am considering if I do this again. The other could be packing tape although that could increase weight too much.

 

[BEAR]

Evan,
Monokote trim sheets might work for covering the flying surfaces. I think the film of the Monokote is even lighter than Scotch tape, in regards to weight. It loses the original desire to take an off the shelf glider and keep it looking like that. You might also take a piece of card stock and glue it to the top of the wing, going back to where you think the CG might be. This would stiffen the wind and add a bit more airfoil shape to it. I do not have any idea what this would do to the weight, and again, it would be detracting from the original idea. Just thinking almost out loud. BEAR

 

[EeebeeE]

Not a bad idea, Bear. I had also thought of using bond paper and applying it to the underside of the wing, using a glue-water mixture, then compressing the wing under weight while it dries to prevent warping. This is a common practice for mach+ mid-power rockets that have balsa fins.

 

[billspad]

Launched it at 20 degrees...maximum allowable by NAR. It pitched straight up. It really did not do a power loop as most have suggested probably because it lost the wings.

I doubt the extra 10 degrees would have helped but it's 30 degrees from vertical.

 

[BEAR]

Sorry, Evan, my fins for mach midpower, up to a G54 or G118 are either laminated 1/64" plywood or laminated fins from .003" aluminum shim, building up to a .030" thickness. More time, but I can then get a very thin and very strong laminar fin. Takes longer, but I like the results. Of course, these are contest altitude birds. I bet I could make laminar aluminum fins, .030 thick for a glider though. BEAR (p.s., I once got a North Pacific nickel glider (1970 time frame) to get to second base during and Astros/Pirates game in the Houston Astrodome. It took the un-asemble wings from two gliders to make one glider that had double the wing span to make it to the base. They were not happy. We dropped our sacks full of gliders and got to the other side of the dome. Some young kids (I was 17) saw our gliders and started playing with them. Security promptly ejected them from the dome. We watched it from the other side.)