Help with designing a low-power glider?

[Rocketbuilder]

I am considering designing a glider to add to my fleet, and I would like to scratch build it to save $$, as I already have rocket building materials. Can anyone give me some general info on designing gliders? Links would be good too, as I have never done a glider before and I expect there is a lot for me to learn!
I would like to keep it pretty simple; either a glider that pops off a rocket at apogee (like a nose cone, but with no shock cord) which is what I would prefer, or if that is difficult/impractical, a glider with a MMT that just pops out the back with a streamer.
I will use BT-55 and fly it on a C6-something.
Thanks!

 

[WillMarchant]

Stine has rules of thumb for a flatcat style boost glider in The Handbook of Model Rocketry.

 

[hornet driver]

BG's are funny critters. They cover a wide range of shapes and sizes based on what your trying to do.Big wings fly nice and slow--little wings are fast- delta's fall somewhere in between. Nose mounting one is difficult at best--but doable. Piggybacks make a lot of sense from a lot of points of view and boom toobs are fun and take advantage of the rocket design but tend to be heavy. Thing is, weight is your enemy--so don't go to great lengths painting and finishing the glider..We had a discussion here on TRF not long ago about building a glider and turning it into a rocket or building a rocket and turning it into a glider.in the end it was pretty much a draw-- A glider, glides better--a rocket flys higher.BG's really push the--- give and take --end of our sport and sometimes result in some unique ,out of the box ideas. Personally I like boomtoobs, they give me the rocket look and near performance but I get a glider out of the deal---but maybe a little fast. Like I said--give and take

 

[AstronMike]

I am considering designing a glider to add to my fleet, and I would like to scratch build it to save $$, as I already have rocket building materials. Can anyone give me some general info on designing gliders? Links would be good too, as I have never done a glider before and I expect there is a lot for me to learn!
I would like to keep it pretty simple; either a glider that pops off a rocket at apogee (like a nose cone, but with no shock cord) which is what I would prefer, or if that is difficult/impractical, a glider with a MMT that just pops out the back with a streamer.
I will use BT-55 and fly it on a C6-something.
Thanks!

This is EASY!! I've got an updated version of "The AstronMike Challenge" for you at the next TTRA launch!

Back in '97, I met some guys online and travelled to Orlando to fly with them at the old Red Bug site (guys and site LONG GONE, alas). I also kitted up some of my venerable Marauder gliders, which are basically foolproof, and thus the challenge I made to them was thus:

Take the bag of Marauder parts, and using the 'Astron Instructions', build the thing ONSITE using ONLY the TAPE in the bag, and fly on the included C6-3 motor!

Turned out the female in the group, a teacher no less, had hers do very well, even outgliding mine that day! The other two guys also worked as well.

The 'updated' version of this will be the use of a BT55 cardstock tube and Depron surfaces instead of the standard tubing and Artcor back then. Since you are already a pretty experienced builder, you only get to use my current Marauder as your instructions, with minimal help from myself. May allow for use of quick dry epoxy instead of double stick tape too.

Try it, you WILL like it and want MOAR MOAR MOAR!!

 

[kjohnson]

You've set yourself up with a difficult task with your design requirements for a first boost glider- C power, rear engine, either nose blow or power pod ejection.

What comes to mind first off is some sort of SST looking rocket like the old estes Sky Dart. https://www.spacemodeling.org/JimZ/k-57.htm
It uses a simple wing, a power pod that ejects out the rear, and flip up elevator.

If you change your mind and want to fly a front engine pop pod design, here is one you can start with that's pretty good: https://www.rocketryforum.com/showthread.php?t=29469

kj

 

[Rocketbuilder]

This is EASY!! I've got an updated version of "The AstronMike Challenge" for you at the next TTRA launch!

Back in '97, I met some guys online and travelled to Orlando to fly with them at the old Red Bug site (guys and site LONG GONE, alas). I also kitted up some of my venerable Marauder gliders, which are basically foolproof, and thus the challenge I made to them was thus:

Take the bag of Marauder parts, and using the 'Astron Instructions', build the thing ONSITE using ONLY the TAPE in the bag, and fly on the included C6-3 motor!

Turned out the female in the group, a teacher no less, had hers do very well, even outgliding mine that day! The other two guys also worked as well.

The 'updated' version of this will be the use of a BT55 cardstock tube and Depron surfaces instead of the standard tubing and Artcor back then. Since you are already a pretty experienced builder, you only get to use my current Marauder as your instructions, with minimal help from myself. May allow for use of quick dry epoxy instead of double stick tape too.

Try it, you WILL like it and want MOAR MOAR MOAR!!

Nice! That's pretty funny!

I just had an idea for a much more complicated glider that would really be more similar in construction to a balsa and tissue paper ornithopter, which a have built a few of a couple years ago. It would use balsa wing spars, with 1/32" balsa as the actual wing material, or maybe some very thin closed-cell foam. The glider fuselage would be made of 2 layers of 1/32" balsa with a slot between them. The wings and tail would fold scissor-like into the slot between the layers, and there would be a mechanism on the booster to hold them folded in until separation. I probably am not making much sense, so I'll post some drawings of it this afternoon.

 

[shreadvector]

I am considering designing a glider to add to my fleet, and I would like to scratch build it to save $$, as I already have rocket building materials. Can anyone give me some general info on designing gliders? Links would be good too, as I have never done a glider before and I expect there is a lot for me to learn!
I would like to keep it pretty simple; either a glider that pops off a rocket at apogee (like a nose cone, but with no shock cord) which is what I would prefer, or if that is difficult/impractical, a glider with a MMT that just pops out the back with a streamer.
I will use BT-55 and fly it on a C6-something.
Thanks!

Centuri Design Manual had a nice parametric glider design:

View attachment cmrdm22.pdf

View attachment cmrdm23.pdf

 

[Sooner Boomer]

I *highly* recommend the MPC "Flat Cat".
https://www.spacemodeling.org/JimZ/mpcr216.htm
It's easy to build, and can be readily scaled up or down for your flying field. The only change I would make is to build the booster pod longer. I built one and flew it last year in light wind. It boosted straight up, separated, turned into the wind, and just kind of "sat there". It was a beautiful flight. Except that everyone was so intent on watching the glider (me included), that I lost the booster pod, even with a 6' streamer.

There are LOTS more plans on JimZ's web site, you just have to dig them out and download them. You'll get hooked!

 

[Rocketbuilder]

Thanks everyone! I learned a couple of things from reading those design manuals, and those pod-thingy gliders are starting to grow on me.
But I just had a really cool idea! I don't know if it's been doe before, but I had the idea of a glider that, as a rocket, flies up backwards, ejects the MMT out of what becomes the nose of the glider, then glides back down. (It would be shaped like a traditional balsa glider, not delta-wing style.) This way, the wings of the glider act as large fins, helping to stabilize the rocket, and the tail of the glider is a few forward fins. Another essential part of the design is that there is a slot in the body tube of the glider, between the two wings. A third fin, almost as large as one of the wings, is attached to the MMT that is ejected. When the MMT is inserted into the glider nose, the third fin slides up into that slot, giving you a three-finned (and stable) rocket. I figure this way it's also less likely to stall, so it will enter a stable glide more quickly.
I'll post the .ork file when I've got the design fully nailed down. So far, it seems to be working in OR.

 

[BABAR]

I don't know if your backward flying glider has been built. I have considered the idea, but came up with two obstacles I could not solve. Main one is adjust the CG. In rocket/boost configuration, you want this relatively far forward. In glide configuration you need to move this centrally, to just forward (relative to the direction on glider flight) of the center of lift. Pop pod gliders such as FlatCat solve this by simply disengaging an intact glider from the boost device. Engine eject models such as Semroc hawk (https://www.rocketreviews.com/semro...-hawk--by-hans-quotchrisquot-michielssen.html) do it by kicking out the forward mounted engine. Problem I had with a rear eject glider flying opposite rocket nose direction is ejecting the motor (tail weight) tend to shift the CG further rocket noseward. (making GLIDER even more tail heavy.). You MAY be able to get around this with a central ejection pod with LOTS of weight attached to the front of the ejection pod. This will come out of the glider at ejection.

Second problem I had was being able to put enough canard fin forward to act as an effective "tail horizontal stabilizer" without DEstabilizing the rocket on boost. Edmonds Ecee has a neat front canard with a moveable tab that shifts at ejection from "neutral" to "lift" configuration. But that still a forward flying glider.

I'd love to see how you make this work. Looking forward to more posts.

 

[AstronMike]

Hey Rocketbuilder,

Instead of trying to work with single ply cardstock with Depron on your first glider build, how about something much more conventional, using a BT55 and 'unconventional' nose cone?

I'll make up a 'quik kit' of my easy cheesy SkyDart LV design, which is basically a very simplified version of a BT55 scaled SkyDart. Mine flies quite nicely on C6-3s, even the Quest ones! Also, due to the use of the standard BT's for the pod and main glider tube, there's no 'funny parts' like a current Marauder would use.

I've posted about this design for sure on Ye Olde Rocketry Forum, you may search for it there, and maybe here as well.

If you have any 5 minute epoxy, you can build this onsite in less than 20 minutes and be flying! For reference I'll guide you through and you get to see mine firsthand. Couldn't be any easier.

Also, if you'd like to get your grubby mitts on something conventional, ala wings/tail 'regular airplane' type, I can help with that as well. The Flat Cat was mentioned, but I've something MUCH better, the Sky Condor. Chris can tell you about this as he's even built one. It uses plastic where plastic NEEDS to go and tung (not tongue) for the flats. I ordered two of these on my last order to UMRS, and will give you the second one. Shoot, you could probably build *THAT* onsite too!

You're going to have gobs of fun at the next TTRA launch, that's for sure!! :clap:

 

[fyrwrxz]

Mike- haven't seen you much over here lately- maybe you would be so kind as to post a few pics of your birds as inspiration/reminders of the AWESOME birds you build! Thanks in advance.

 

[Rocketbuilder]

I don't know if your backward flying glider has been built. I have considered the idea, but came up with two obstacles I could not solve. Main one is adjust the CG. In rocket/boost configuration, you want this relatively far forward. In glide configuration you need to move this centrally, to just forward (relative to the direction on glider flight) of the center of lift. Pop pod gliders such as FlatCat solve this by simply disengaging an intact glider from the boost device. Engine eject models such as Semroc hawk (https://www.rocketreviews.com/semro...-hawk--by-hans-quotchrisquot-michielssen.html) do it by kicking out the forward mounted engine. Problem I had with a rear eject glider flying opposite rocket nose direction is ejecting the motor (tail weight) tend to shift the CG further rocket noseward. (making GLIDER even more tail heavy.). You MAY be able to get around this with a central ejection pod with LOTS of weight attached to the front of the ejection pod. This will come out of the glider at ejection.

Second problem I had was being able to put enough canard fin forward to act as an effective "tail horizontal stabilizer" without DEstabilizing the rocket on boost. Edmonds Ecee has a neat front canard with a moveable tab that shifts at ejection from "neutral" to "lift" configuration. But that still a forward flying glider.

I'd love to see how you make this work. Looking forward to more posts.

Hmmm... I know how to build a rocket alright, but I have no idea what I'm doing when it comes to aircraft. Could someone give me a lesson on CP/CG of gliders? How large does the tail need to be?
The key to the design is the one or more extra fins that are ejected along with the engine mount. As for the CG shift, maybe a weight with a couple of small magnets could be attached to an internal tube attached to the engine mount, using something only just sticky enough to keep it on the tube. When the engine mount is ejected, the tube slides out, pulling the weight toward the nose of the glider, until it attached to other magnets on the inside of the tube pulling it off the tube being ejected. Let me know that didn't make any sense.

AstronMike: Thanks! That sound cool!

I'm thinking for a first glider, I should maybe stick with something easier, but I will try and make this idea work.

 

[BABAR]

Hmmm... I know how to build a rocket alright, but I have no idea what I'm doing when it comes to aircraft. Could someone give me a lesson on CP/CG of gliders? How large does the tail need to be?
The key to the design is the one or more extra fins that are ejected along with the engine mount. As for the CG shift, maybe a weight with a couple of small magnets could be attached to an internal tube attached to the engine mount, using something only just sticky enough to keep it on the tube. When the engine mount is ejected, the tube slides out, pulling the weight toward the nose of the glider, until it attached to other magnets on the inside of the tube pulling it off the tube being ejected. Let me know that didn't make any sense.

AstronMike: Thanks! That sound cool!

I'm thinking for a first glider, I should maybe stick with something easier, but I will try and make this idea work.

As my Japanese instructor, Maj. Fujita kept telling me,

"KISS* Markel-San, KISS"

*KISS- Keep It Simple Stupid

Kits are a great way to start, and if your time is worth more than 3 bucks an hour probably worth the cost compared to the time it will take you to figure it out yourself for your first one or two. Try a pop pod, an engine eject, and a rear eject either with a kit or from some online plans. Once you get a feel for these, THEN kick your imagination and your building skills into high gear. Also Stine's book and Van Milligan's book are both great reads and will save YOU a lot of time in your designing.

Remember, smart people learn from their mistakes. REALLY SMART PEOPLE learn from OTHER PEOPLE'S mistakes.

 

[JStarStar]

The Semroc Space Plane is adapted from the design of the first boost glider successfully flown in 1960.

It features motor ejection (although it is not hard to tape a streamer to the motor casing to make the whole deal NAR contest legal and avoid free-falling motor casings) to actuate elevon surfaces which are pulled up by elastic cords after the motor pops out.

When the elevons flex upwards, the rocket fins become wings which then produce lift and the rocket glides to the ground.

Space Plane-style gliders do not perform well compared to more common front-engine pop-pod style gliders, but they are good for learning about the progression of the hobby. And a well built and trimmed Space Plane style glider can turn in nice flights.


https://www.semroc.com/Store/scripts/RocketKits.asp?SKU=XES-K3

 

[hornet driver]

Hmmm... I know how to build a rocket alright, but I have no idea what I'm doing when it comes to aircraft. Could someone give me a lesson on CP/CG of gliders? How large does the tail need to be?
The key to the design is the one or more extra fins that are ejected along with the engine mount. As for the CG shift, maybe a weight with a couple of small magnets could be attached to an internal tube attached to the engine mount, using something only just sticky enough to keep it on the tube. When the engine mount is ejected, the tube slides out, pulling the weight toward the nose of the glider, until it attached to other magnets on the inside of the tube pulling it off the tube being ejected. Let me know that didn't make any sense.

AstronMike: Thanks! That sound cool!

I'm thinking for a first glider, I should maybe stick with something easier, but I will try and make this idea work.

RB, I'm going to oversimplify a bit so bear with me. As far as the CP/CG of the GLIDER is concerned---worry about the CG. It should be about midwing or a bit forward of that point. As far as tail size is concerned--the closer the distance to the main wing--the bigger the tail---all things being equal this includes the vert and horz. It's a matter of your leverage moment. But the profile you choose dictates any ballast you may need for the nose to get the CG correct. To get a simple glider dynamically stable - it's best to be a "tick" nose heavy . Let airspeed and the tail do the rest.The KISS rule is the best route when learning this stuff. Make some simple gliders and tinker with them. Once you have the basics down--try and incorporate them into a rocket glider. ----First write down what you want the glider to do---lots of time, up a bit but not too long, re-entry----Design a glider that suites what you want and test it with a smaller , simple balsa or foam model. Once you have the design you like, you have to move to the dark side and figure out how to get it in the air. So with your rocket tools in hand--do you Piggy back, boomtube,motor eject and how do you have to compromise your glider to do one of them.You see where I'm going with this--it becomes give and take . Honestly, Most of mine are boomtube type gliders because I pretty much end up backdesigning a glider out of a rocket and the design lends itself to that technique. Not high performance, but they glide in for recovery. Pictured below are Timberwolf and Boxster. Timberwolf glides like a rock, but it glides and I new it would be fast--sorta like a shuttle---Boxster is a bit more docile and trimmed out performs better than I expected---but not a long time glider. Have fun with this stuff, it really opens up a lot of opportunities for going outside the box in our hobby.

 

[hornet driver]

Sorry --here's TW

 

[Rocketbuilder]

Sorry, I missed this thread for a couple of days.
Those are really NICE looking birds there Hornet! I agree with everything you said!

 

[Massrokit]

Try the Flat Cat a good basic glider design:
https://www.ninfinger.org/rockets/ModelRocketry/Model_Rocketry_v01n10_08-69.pdf