Which comes first?

[MrGneissGuy]

While I have built a couple of boost glider kits (Semroc Swift and Hawk), I am thinking about trying to build one of my own design, but I'm not sure where to begin.

With the scratch built StegoSoarus rocket working better than I'd hoped, and being fairly popular at our most recent club launch, I've been thinking about how to do another dinosaur themed rocket. With the Semroc Hawk being my most recent build putting me in a boost glider mood, I'm thinking I'd like to give a PteroSoar a shot.

So if I'm going to design a boost glider, is it better to design and build a prototype for gliding first, then make adjustments to the design to make sure it has a stable boost? Or do folks design these for a stable boost, then make modifications so that it glides well? I've gotten pretty familiar with Open Rocket, and I think I can build a glider in there such that I can simulate boost, but don't know of how to simulate glide.

My initial thought is to build something out of scrap materials (making changes as needed) to get a prototype that glides, then build it in Open Rocket and see what I can do to give it a stable boost. Is that the most efficient way to go?


Or has a Pterodactyl boost glider already been done?

 

[JAL3]

I have a really bad record with most gliders although I have had some recent success (even won 1st in a NAR C rocket glider contest!). My first "successful" build was the Semroc Swift BG. I painted mine and made it way too heavy and it still performed well. I have no experience with the other you mentioned.

Before trying to do somethign from scratch (and I am NOT qualified the answer the question you posed) I would suggest trying the Swift and other proven designs to "get the hang of it."

There is no reason why you could not finish it with a dino theme. In fact, I would think the Swift would lend itself to the rough outline of several pterosaurs.

 

[kjohnson]

For something like this, I'd build the glider and get it sorted and then try and boost it. You don't want to forget while designing the glider that you'll need to have a pop pod attached, so while you are tweaking the design make sure you include that.

You could be slick, and make the horn at the back of the head part of the pod hook. Warning, really bad sketch attached.

kj

 

[JAL3]

Congrats!

It looks like you have had a glider guy with real experience chime in

KJ: your "really bad sketch" far exceeds the upper limits of my artistic talents.

It looks like a cool project.

 

[MrGneissGuy]

JAL, actually the Swift was the first (successful...we don't talk about the TransWing much any more) one I have built and flown. I too painted mine and it's still given me great glides. The Hawk is a smaller glider with swept back wings. I only flew it once, Memorial Day weekend, but it also boosted and flew really well, especially considering the breeze we had (almost didn't launch it at all).

KJ, I agree with JAL, that's not a bad sketch at all. And using the head/horn as the pod hook (or just making it a motor mount like on the Hawk, just letting the motor pop out on ejection) was exactly what I was thinking. The hook will look better. That and having the "feet" angle downward to act as combination tail fins/stabilizers.

 

[kjohnson]

That and having the "feet" angle downward to act as combination tail fins/stabilizers.

Yeah that's a good idea. You could make sort of an inverted V tail with the legs and feet and the flaps of skin that attach them. Here's another ugly sketch.

kj

 

[hornet driver]

While I have built a couple of boost glider kits (Semroc Swift and Hawk), I am thinking about trying to build one of my own design, but I'm not sure where to begin.

With the scratch built StegoSoarus rocket working better than I'd hoped, and being fairly popular at our most recent club launch, I've been thinking about how to do another dinosaur themed rocket. With the Semroc Hawk being my most recent build putting me in a boost glider mood, I'm thinking I'd like to give a PteroSoar a shot.

So if I'm going to design a boost glider, is it better to design and build a prototype for gliding first, then make adjustments to the design to make sure it has a stable boost? Or do folks design these for a stable boost, then make modifications so that it glides well? I've gotten pretty familiar with Open Rocket, and I think I can build a glider in there such that I can simulate boost, but don't know of how to simulate glide.

My initial thought is to build something out of scrap materials (making changes as needed) to get a prototype that glides, then build it in Open Rocket and see what I can do to give it a stable boost. Is that the most efficient way to go?


Or has a Pterodactyl boost glider already been done?

I like the idea of a pterosaur. I'm on board with the other guys to tweek the glider first and the adapt it to boost. Really unless you had a pure delta design its difficult to back design a rocket into a glider without paying a weight penalty. If the boost profile is CP-CG OK the the glide profile is probably a bit nose heavy-- you add ballast to take care of that problem but that affects your boost stability--and back and forth -- real easy to get into a coffin corner. Next if you add weight to the glider not only do you carry it up but carry it down too. Not a great idea. At least with a pop tube you eject all that weight. Even piggybacking works and is sometimes simpler. I'm going through these challenge myself with the Interceptor glider i'm building but i knew going into it I was going to have those tradeoffs. Anyway you look at it boost gliders are cool and help us get out of the box a bit.

 

[kjohnson]

Found this image when searching for some HLG plans, maybe it will help in your design.

kj

 

[MarkII]

https://www.ninfinger.org/rockets/catalogs/enerjet72/72ejet12.html

 

[JPVegh]

Here is a general starting point.

Wing span S
wing chord C = 1/7 S

Stabilizer span SS = (0.4) X S
stab chord CS = (0.85) X C

Tail moment arm M = (0.5) S

Fin height FH = (0.4) SS
fin chord CF = CS

Nose length NL = (0.46) M

Body length BL= (7/8) S

Wing Camber CA = (1/12)C

Wing tip rise R= (1/12)S

 

[MrGneissGuy]

Wow, lot's of helpful suggestions and information. I guess I really need to go forward with this project so as not to let all that go to waste. Next on the agenda is an Underdog rocket, which is going to be tricky. Then I'll start working on the Pterosoar. I've been making mental notes of ideas here and there in the mean time. I'm going to have to start writing those down and making sketches.

 

[The Amazing Criswell]

glider, then boost

 

[geof]

I like the idea of a pterosaur. I'm on board with the other guys to tweek the glider first and the adapt it to boost. Really unless you had a pure delta design its difficult to back design a rocket into a glider without paying a weight penalty. If the boost profile is CP-CG OK the the glide profile is probably a bit nose heavy-- you add ballast to take care of that problem but that affects your boost stability--and back and forth -- real easy to get into a coffin corner. Next if you add weight to the glider not only do you carry it up but carry it down too. Not a great idea. At least with a pop tube you eject all that weight. Even piggybacking works and is sometimes simpler. I'm going through these challenge myself with the Interceptor glider i'm building but i knew going into it I was going to have those tradeoffs. Anyway you look at it boost gliders are cool and help us get out of the box a bit.

I've built many scratch gliders, mostly large, ranging from very successful:
https://archive.rocketreviews.com/reviews/all/scratch_groovy_katt.shtml
https://www.rocketreviews.com/scratch-manta-3-by-geof-givens.html
to, uh, less so:
https://www.rocketreviews.com/scratch-the-albatross-by-geof-givens.html

I totally agree with the general consensus here that you build to glide first and worry about boost second. However, I want to emphasize something that was mentioned above. In my opinion, the easiest way to have a scratch success is with a piggybacking approach. That way, the glider is totally self-contained. You just need to make a glider that flies. Hang it off the back of the booster far enough, and/or make the booster stable/long enough, and the up part is really "easy" because the glider serves as huge fins on the way up. The down part is also "easy" because you built the glider all by itself. You wouldn't be tackling this project if you couldn't make a standalone glider that flies.

That leaves only two tricky parts. First, separation at apogee, including getting the timing right. If the hook is too loose, the glider comes off during boost, potentially fatally. I've never had the glider get stuck on the hook permanently because of the forces created as the unit plummets toward earth, but I suppose that could be bad. Failing to release until after apogee (sometimes sickeningly so) is not unusual for me. Use a very short delay.

The second tricky part is wind. The up part is not quite so easy as I claimed because in wind the rocket will weathercock terribly. This can lead to an arcing boost where the glider is released at high speed and low altitude horizontally or worse. Gliders make good lawn darts. However, if you can get it up in a stiff breeze, the actual gliding phase isn't affected too much.

So that's my advice. There's a guy on here AstronMike, who has a ton of experience with big gliders.

By the way, I highly recommend the Edmonds Aerospace Twin Thunder kit. It's a twin set of belly-mating gliders that split at apogee. With an exciting boost and separation, if you can get a good trimming job for long flights the rocket is a real crowd-pleaser.

Geof

 

[MarkII]

GG,

I am always blown away when I see a BG that someone has built that actually boosts AND glides. Someday I hope to get that deal figured out myself. So I am totally in awe of anyone who will even attempt to design one of these flying paradoxes from scratch and actually get it to work. Good luck! I'm very interested in seeing what you come up with.

 

[MrGneissGuy]

GG,

I am always blown away when I see a BG that someone has built that actually boosts AND glides. Someday I hope to get that deal figured out myself. So I am totally in awe of anyone who will even attempt to design one of these flying paradoxes from scratch and actually get it to work. Good luck! I'm very interested in seeing what you come up with.

Well, obviously given the dates in this thread, I haven't made a lot of progress in this. While I've scratch built several rockets, including some fairly odd/unorthodox ones, I don't have much experience with the gliders. My daughter built one (Estes TransWing) that met an untimely death, and I've built two from kits that have done quite well.

It seems it has been extra windy this year, so much so that I've been hesitant to launch certain rockets in my fleet, much less gliders. And as such I've not really done much in advancing this particular project other than some brainstorming and sketching. The plan now is to make this one of my winter builds.

Since I would really just be winging it if I attempted this as a scratch, I've decided it would be better to take a kit and make some modifications to it to get the look I want. I think I'm going to base it on the Semroc Hawk, which is actually one of the two gliders I have. The plan is to take the kit's wings and modify their shape, and make them polyhedral. I'll also be making modifications to the tail section to make it look more like feet and a tail. With the change in shape for the wings, I'm guessing their position on the body will need to change, and I'm hopeful I can temporarily mount them with masking tape or something for a few test glides to find the best position. I'm also planning to make templates of the kit pieces, so I can use balsa sheets and make changes if something doesn't work, and still have the same starting point.

I have not given up on this idea.

 

[geof]

Have you built the Hawk? I had one and it was total junk no matter how I trimmed it.

 

[MrGneissGuy]

Yes, the Hawk was my third and most recent glider build (the first was an ill fated Estes Transwing, the second a Semroc Swift). It flies quite nicely. The first flight scared me, as it initially just started gliding off straight as an arrow. But it ended up making one large circle and I didn't have to walk too far to recover it. I now add a paper clip to the left wing so it circles better. It still makes pretty wide circles, so I don't launch it when there's much wind, but it's been a good flier in the right conditions.

Here's a video of the first launch.

[YOUTUBE]m_A83R4zLu4[/YOUTUBE]

 

[MarkII]

In the best flight that I have gotten so far with my Astron Falcon clone, it boosted straight up, ejected the motor and transitioned into a level glide, and then a second or two into the glide it pointed its nose down and plunged straight back down into the (soft, tall grass-covered) ground. I have had better flights with my Wombat - at least it comes down at an angle.