Keeping It Low: What Approach Do You Prefer for Flying in Small Fields?

mh9162013

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Most of my flying takes place in smaller-sized locations, such as sports fields and parks. As a result, when I build rockets, I need it to be capable of flying reliably and safely to anywhere from 75 to 200 feet. Any higher than that and I risk losing the rocket to trees or it otherwise being unrecoverable.

Of course, having the ability to fly higher is nice. For example, my current "approach" is to focus on BT-20 rockets where I use 1/2A and A engines. But pop in a C or D and reaching 1,000 feet should be easily done. Recovering the rocket on the other hand...

But now I have a decision to make. My Jolly Logic AltimeterTwo doesn't like to work unless it has its case. This means it will no longer fit in my BT-20 rockets. Buying a Micropeak altimeter is what I'm thinking about doing (No FS Mini for the foreseeable future, right?), but then I thought, how about building bigger, BT-60 rockets, like the Big Bertha, Patriot or Citation Patriot?

One drawback is that they're bigger and heavier which means launching with cheap 13mm engines is out of the question. But would they produce more enjoyable launches? And by enjoyable, I mean easier to watch and see.

For example, if an Estes Yankee with an A engine gets to 185 feet (I build my rockets heavy, with extra paint, thicker Kevlar, payload bay, baffle, at least two snap swivels, etc.) and an Estes Patriot gets to 175 feet with a B engine, won't the latter have a slightly slower lift off and be more easily viewed during its flight? And if I get the "fly high or go home" itch, BT-60 rockets I mentioned above are just begging for 24mm or 29mm engines...

Do any of you have thoughts on which sized rockets you would prefer to build in you had similar limitations as me? If so, why would you choose one design/size over another? Just curious; no right or wrong answers.
 
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LithosphereRocketry

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I really like the big-and-slow strategy- one of my favorite small-field rockets is a 3" diameter Saturn 1B on 24mm E motors. The minimum viable altitude does go up a bit as you get to bigger rockets, but not a whole lot; especially with fast-burning motors, you can get away with some pretty low altitudes.
 

ThirstyBarbarian

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For low flights, my favorite strategy is large-diameter rockets and fast-burning motors.

Large diameter means the rocket slows down due to drag as soon as the motor burns out. And fast-burning motors burn out quickly, so the rocket starts slowing down quickly, keeping the altitude low. Just be sure the motor has enough initial thrust to get it off the pad with enough speed to be safe. And be sure the delay is short enough to eject the chute before the rocket starts coming down too quickly.

For example, an Estes Big Daddy is a 3” diameter rocket. That’s a pretty fat draggy rocket for its weight. That means the weight is low enough to allow it to fly safely off the pad with relatively low thrust compared to longer, heavier 3” diameter rockets. I had one I could fly on a D12-3 to less than 200’. I also flew it on C11-3s, and the thrust was adequate, but the delay was unnervingly short, and it used to deploy well after apogee. I think it only got to about 90’.

Anyway, that’s the idea. If you are sticking with Estes, look for BT60 and BT80 rockets for drag. And then look for motors with enough thrust that burn out quickly. Those will be fun flights, with plenty of flame, smoke, and roar, and a low deployment that will allow you to clearly see the chute pop out, and few recovery hassles.

I’m mostly into high power now, so I’m kind of out of touch with Estes kits and the choices in low power motors, so I don’t have specific advice on exact kits or motors, but those are the basic principles I follow for fun “low and slow” flights. Drag, high thrust, short burn, low total impulse.
 

ThirstyBarbarian

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To add to what I said earlier, I have an old 4” diameter NCR Big Brute rocket that was given to me. It’s got an odd sized motor mount, so the modern 29mm F, G, H motors that you might normally pick won’t fit. So instead I adapt it down to 24mm, and the only single-use motor I can readily use is an F44-4. It has enough thrust to fly it, but burns out really fast. I’m sure it barely makes 200’, if that. It is really low. That’s kind of a fun one to watch.

If you put that same F44 in a long, skinny 1.5” rocket of the same weight, it would probably go 3x as high if not higher. Drag makes a lot of difference.
 

Sandy H.

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I think BT-60 is a pretty nice sweet spot for low flights with a B motor or higher flights with a composite 18mm D motor. Maybe check the JimZ site for something like a Blue Bird Zero or similar size rockets. In all fairness, that one might not fly well on a B, but similar rockets in the BT-60 range (Big Bertha, Baby Bertha etc.) would likely be good.

Sandy.
 

BEC

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There's also the approach of putting a MicroMaxx motor mount and a small streamer in a Mosquito, and building some of Semroc's MMX downscales.... Great schoolyard type flyers.

Or....use the Estes 13/18mm adapters to use 1/2As and As in Alpha-sized models (or ones that are just a little lighter). I've also flown a Big Bertha on B6-2s in a schoolyard setting. And of course there are sorts of small spools, saucers and such. But they don't do the full model rocket flight sequence, really.
 
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smstachwick

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Most of my flying takes place in smaller-sized locations, such as sports fields and parks. As a result, when I build rockets, I need it to be capable of flying reliably and safely to anywhere from 75 to 200 feet. Any higher than that and I risk losing the rocket to trees or it otherwise being unrecoverable.

Of course, having the ability to fly higher is nice. For example, my current "approach" is to focus on BT-20 rockets where I use 1/2A and A engines. But pop in a C or D and reaching 1,000 feet should be easily done. Recovering the rocket on the other hand...

But now I have a decision to make. My Jolly Logic AltimeterTwo doesn't like to work unless it has its case. This means it will no longer fit in my BT-20 rockets. Buying a Micropeak altimeter is what I'm thinking about doing (No FS Mini for the foreseeable future, right?), but then I thought, how about building bigger, BT-60 rockets, like the Big Bertha, Patriot or Citation Patriot?

One drawback is that they're bigger and heavier which means launching with cheap 13mm engines is out of the question. But would they produce more enjoyable launches? And by enjoyable, I mean easier to watch and see.

For example, if an Estes Yankee with an A engine gets to 185 feet (I build my rockets heavy, with extra paint, thicker Kevlar, payload bay, baffle, at least two snap swivels, etc.) and an Estes Patriot gets to 175 feet with a B engine, won't the latter have a slightly slower lift off and be more easily viewed during its flight? And if I get the "fly high or go home" itch, BT-60 rockets I mentioned above are just begging for 24mm or 29mm engines...

Do any of you have thoughts on which sized rockets you would prefer to build in you had similar limitations as me? If so, why would you choose one design/size over another? Just curious; no right or wrong answers.
Whatever it is, if I’m going low, I just underpower it. Big rocket, little rocket, it doesn’t matter to me. Perhaps the most fun though was taking the Wanderer 2.0 fiberglass-body traveling rocket to 181 ft on a C11-3.

Then there were the guys who sent a full-scale V-2 to 964ft on a Cesaroni O25000 Vmax motor.
 

BABAR

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Thinking outside the box, switch to streamer recovery. Build bigger rockets, but use a forward delta (forward sweep) of the trail edge of the fin so the rocket comes down on the casing, not the fin. rockets on streamers come down harder than parachutes. Streamers are more forgiving than chute for early or late ejections.

may also want to consider saucers or monocopters.
 

techrat

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For very light rockets like the Alpha III, I don't even bother with a chute. Popping the nose-cone is enough drag to bring the rocket down sideways and since it's a grass landing where we fly, generally no damage done (with the A III, most I get is a slightly bent plastic fin tip -- that'll buff out!). We generally get a pretty good breeze in the afternoon, so I also tend to undersize my chutes -- I might fly a heavier D or E motor'd rocket on a 15" or even a 12" chute, and have it come down pretty quick, which is important because otherwise the wind will carry it across the street. Risking a broken fin is better than a completely destroyed or lost rocket, and I haven't yet broken a fin.
 

DigBaddy

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Not going to rehash some great tips already given. I like fat and draggier stuff for small fields, but adding in a JLCR makes for more altitude easily without worrying about drift too much. BT60 and up will be needed though (although I've heard people have gotten them in BT-55 rockets successfully). Also, sticking to rockets you know will go straight up helps as well.

Picking the right time of day and wind direction matters. We will hit our local park in the mornings before wind picks up. It's not a huge field, and has a nice group of trees on the south/middle part of it. But, things like the old Alien Space Probe on an E12-6 with JLCR works just fine or Big Daddy on some composite Es are doable. We routinely use the JLCR on this field and then use guidelines suggested above to enjoy quite the range of rockets.
 

mh9162013

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Or....use the Estes 13/18mm adapters to use 1/2As and As in Alpha-sized models (or ones that are just a little lighter).
I sometimes do that (I used to have an Alpha III with a 13mm motor mount inside), but the more I build BT-50 rockets, the more they kind of "annoy" me.

They're not quite small enough to take full advantage of 1/4A though A 13mm engines, but they're not big enough to really have the "growth potential" of a BT-60 rocket in terms of larger engines or payload capacity.
 

milehigh

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I often fly rockets in small parks. My primary strategy is to pick a day when wind is negligible.

As a rule if thumb in such conditions, I have successfully flown BT-5 sized models on 1/2A motors. BT-20 birds on A motors, A or B motors on BT-50, B and sometimes C motors on anything larger (BT-55/60)
On calm days, all of these flights go fairly high (300-600 foot range), but usually land fairly close to the launch pad using parachute recovery.

I am a strong practitioner of the "Fly the field, fly the wind conditions" philosophy.
 

Back_at_it

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If I'm flying locally I'm limited to about 300ft and honestly I'm getting tired of chasing rockets across fields so I tend to fly them low. If I'm building smaller BT20 and BT50 rockets I can easily adapt down and fly on 13mm A3 and A10 motors. I really don't see the point in building most BT20 rockets with anything larger than a 13mm mount. I have a number Wizards, Vikings, Ninjas etc. that were built this way. I have an upcoming Laser build that will have a 13mm mount and estimated altitudes of 99ft on a 1/4A3 and 189ft on a 1/2A but still good for over 500ft with an A10 so being that small it will be well out of my eyesight.

There are a ton of current BT50 rockets that fly great on the 13mm motors. The Crossfire, Alpha III, Generic, Illusion, Phantom Blue, Cadet etc etc. are all good choices for low flights with the cheaper 13mm motors.

If you want to go larger then I'd suggest a Baby Bertha. Mine flies to 183ft on an A8-3. The Big Bertha is also a slow and low flier on a B4-2.

Larger still is the Big Daddy. If you build it stock you can fly it on a C11-3 for around 125ft apogee. Nice thing about this one is you can stick an E30 in it later and really send it. Again it it needs to be built light for the C11 to work.

If you want to get a serious rocket then the Micro Magg by LOC is a great choice. https://locprecision.com/collections/rockets-4-00-diameter/products/micro-magg This is a great small park flier on an F44-4. All the noise of a composite and a recorded altitude of 276ft.

How about building yourself an upscale BT60 Luna Bug from a Baby Bertha kit. With the big fins and landing pads you're only looking a 170ft on a C5-3 or C11-3.
 

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BABAR

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Now that @Dotini is routinely doing Horizontal Spin Recovery and @Rktman and I are doing BackSliders, this is a now a pretty rare but spectacular recovery technique (there was at least ONE Estes production version) that works great for small fields and zero to light winds, and could probably be upsized to maybe an E.




haven’t flown them at a club launch, I suspect they would be popular.
 

smstachwick

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Now that @Dotini is routinely doing Horizontal Spin Recovery and @Rktman and I are doing BackSliders, this is a now a pretty rare but spectacular recovery technique (there was at least ONE Estes production version) that works great for small fields and zero to light winds, and could probably be upsized to maybe an E.




haven’t flown them at a club launch, I suspect they would be popular.
I understand that the Mean Machine is pretty close to the profile of a typical backslider. Perhaps a few modifications could yield an E, F, even a G-powered backslider.
 

BABAR

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I understand that the Mean Machine is pretty close to the profile of a typical backslider. Perhaps a few modifications could yield an E, F, even a G-powered backslider.
Great thought. One modification, due to the large volume of the rocket, I might put a bulkhead say 6 inches forward of the forward end of the motor casing, sealing off the tail end chamber of the rocket, and put the side port at the TAIL of the rocket off this chamber. It is less effective (normally) than at the nose as closer to CG, but I think the huge rocket volume might make a forward port inadequate as the internal volume may not sufficiently pressurize. You could used a stuffer tube or chimney, but I am afraid that would make the rocket both too heavy and more importantly will pull CG too far forward, Rocket more likely to go ballistic Post ejection.
 

teepot

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Take a look at the BMS School Rocket. It's a 3" BT and has a 24mm mmt. If you want it taller and heavier get the optional payload section. Go to ThrustCurve.com and experiment with different diameters and weights and it will give you a selection of motors and tell you the altitude it should make. Click on the "i" next to the altitude and it will give a lot more info. I just call the rocket experimental and plug in what size BT size I'm going to use, what mmt and the target weight I think the rocket will be. Then I can decide if the rocket will do what I want.
 

jflis

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Fliskits has a number of choices perfect for small fields. The entire micromaxx line for starters.

for 18mm the Frick-n-Frack is a great small field 2 stage choice. Then for big and fun there’s the 24mm Decaffeinator on C11 motors…
 

Kabulrocks

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Back in the day (1974ish) in elementary school I had an Estes SPEV that was low and slow. I don’t recall what motors were used, but it was a class favorite since it was easy to see. I want another one....
 

Arnie

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I could never understand the fascination of watching a model rocket disappear in the blink of and then watching in rapt interest as the model descends on whatever the chosen recovery method is. Give me low and slow, so I can watch the entire flight from launch to touchdown.
 

mh9162013

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Give me low and slow, so I can watch the entire flight from launch to touchdown.
How do you go about doing that with a BT-20 rocket? Make it super draggy and/or give it some ballast in the nose?

I'd love to see an Estes Yankee, Viking, Wizard or similar sized/designed rocket lift off like a Big Bertha...
 

Back_at_it

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How do you go about doing that with a BT-20 rocket? Make it super draggy and/or give it some ballast in the nose?

I'd love to see an Estes Yankee, Viking, Wizard or similar sized/designed rocket lift off like a Big Bertha...

Nose weight, lots of primer / filler for weight and a 1/2A6-2 will keep it in sight and slow the lift off a bit. I know someone that use to add 1oz of nose weight to all of his small rockets to help keep the altitude down.

I don't know of a motor that will give you a "slow" Bertha like lift off with that small of a rocket.
 

mh9162013

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Nose weight, lots of primer / filler for weight and a 1/2A6-2 will keep it in sight and slow the lift off a bit. I know someone that use to add 1oz of nose weight to all of his small rockets to help keep the altitude down.

I don't know of a motor that will give you a "slow" Bertha like lift off with that small of a rocket.
I've been thinking about those engines, but felt 1/2A3-2T 13mm engines might be more economical. However, looking at the thrust curves, I see the 1/2A6-2 18mm engine has a much more gradual rise in thrust, which could help facilitate a slower liftoff (in addition to being almost double the weight, too).
 

ThirstyBarbarian

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Mostly, adding weight is not the solution. Drag is the solution.

A rocket needs a minimum speed off the launch guide to fly straight. The slower you go, the more likely it is your rocket will weathercock and crash. So you can slow it down a bit by adding some weight, but don’t go below the safe launch speed. If your rocket is going to crash, the last thing you want is added weight.

And also be aware that adding weight adds momentum to the rocket, so in some cases, a heavier rocket actually does go higher than a lighter one. It’s counterintuitive, but true in some cases. The added momentum of the added weight helps the rocket overcome drag. Think in terms of throwing a wiffle ball versus a baseball.

The holy grail we are searching for is the slow, graceful launch where the rocket lifts off slowly, the motor keeps burning, and the rocket slowly accelerates, never getting very fast. We are conditioned by watching space launches that look like that. But boosters for satellites and spacecraft have active guidance, and they don’t rely on fins to keep them going straight. Ours use fins, and they need a minimum speed for those fins to work.

So the easiest solution for low flights for ALL types of rockets is to pick motors that get them off the launch guide at a minimum safe speed and then burn out as soon as possible after that. They go off like a mortar round and start coasting immediately. That strategy works for skinny or fat rockets.

But if you want the longer burn motors, and you want to stay low, which is something I personally love, then the best thing is to keep the rocket light, but very draggy. Light weight allows the motor to push the rocket up to safe launch speed quickly. But drag is proportional to speed, so the faster the rocket goes, the more the motor has to fight drag. That limits the top speed and helps keep the rocket lower in altitude.

Do a “mind sim” (or an actual sim!) of two rockets that have exactly the same weight. One is minimum diameter, long, skinny, with nose weight. The other is 3x the diameter, shorter, and no heavier than it has to be. Launch them on exactly the same motor. They both clear the launch guide at the same speed due to their identical mass. What happens after that? Which goes higher? Which stays lower?
 

mh9162013

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Mostly, adding weight is not the solution. Drag is the solution.

A rocket needs a minimum speed off the launch guide to fly straight. The slower you go, the more likely it is your rocket will weathercock and crash. So you can slow it down a bit by adding some weight, but don’t go below the safe launch speed. If your rocket is going to crash, the last thing you want is added weight.

And also be aware that adding weight adds momentum to the rocket, so in some cases, a heavier rocket actually does go higher than a lighter one. It’s counterintuitive, but true in some cases. The added momentum of the added weight helps the rocket overcome drag. Think in terms of throwing a wiffle ball versus a baseball.

The holy grail we are searching for is the slow, graceful launch where the rocket lifts off slowly, the motor keeps burning, and the rocket slowly accelerates, never getting very fast. We are conditioned by watching space launches that look like that. But boosters for satellites and spacecraft have active guidance, and they don’t rely on fins to keep them going straight. Ours use fins, and they need a minimum speed for those fins to work.

So the easiest solution for low flights for ALL types of rockets is to pick motors that get them off the launch guide at a minimum safe speed and then burn out as soon as possible after that. They go off like a mortar round and start coasting immediately. That strategy works for skinny or fat rockets.

But if you want the longer burn motors, and you want to stay low, which is something I personally love, then the best thing is to keep the rocket light, but very draggy. Light weight allows the motor to push the rocket up to safe launch speed quickly. But drag is proportional to speed, so the faster the rocket goes, the more the motor has to fight drag. That limits the top speed and helps keep the rocket lower in altitude.

Do a “mind sim” (or an actual sim!) of two rockets that have exactly the same weight. One is minimum diameter, long, skinny, with nose weight. The other is 3x the diameter, shorter, and no heavier than it has to be. Launch them on exactly the same motor. They both clear the launch guide at the same speed due to their identical mass. What happens after that? Which goes higher? Which stays lower?
You've got me thinking about ways to make things more draggy w/o affecting the desired appearance too much.

Well, I already don't airfoil my fins. But maybe I could make them thicker. Imagine an Estes Viking with all 5 fins, but each fin is made out of 1/8" balsa that's also papered...
 
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