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

Off Grid Gecko

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Big Fins to up the drag a lot. The little school rockets I'm designing are an odd philosophy. Good performace for size while keeping them low. BT-5 tube with a 13mm and light enough to recover on a streamer. 1/4A for small fields but that little guy rips on a 1/2A and surprisingly fun rocket with that motor. Haven't tried it on a full A yet. Doing more 1/4A testing at my house and next time I get to the flying field I might push it to A power if it isn't too windy. Should be fun, haha.

BT-60 Mosquito type rocket would be interesting approach.
 

techrat

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You want low and slow for a small rocket? That's easy. Put streamers on the OUTSIDE. Make big fins with holes in them. Make right angle (AKA "T" Shaped) fins that are SQUARE.
 

BigMacDaddy

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Lots of good advice.

One thing to comment on is something in your original post about the cost of the engines. You are absolutely right that mini engines are cheaper than 18mm or 24mm engines -- but by how much? No so much really... $1.89 / engine for minis (Using AC Supply price for 4-pack) and $2.23 / engine for 18mm (using Blast-off Flight Pack - $2.94 if you look at 3-packs of C-engines). Anyway, don't stress too much about cost going up to 18mm. Cost per engine jumps up to $4.50 for D's and $6 for E's.

One secret to low and slow is definitely going up to larger body tubes -- longer or wider -- which equates to more drag and weight. Longer rockets are quite stable and bigger body tubes add a surprising amount of drag. Look for BT-60 models -- like the Big Bertha but BT-55 models like the Nike-X can fly great with smaller engines. If you are going to scratch-build you can also go up to BT-80 but those tend to want 24mm engines unless they are short and light.

Mini Mean Machine is a great / impressive rocket for mini engines (and even better with 18mm engines).



Some rockets can also be designed and launched with a pair of Mini Engines... Here is a Pogo with 2x A10 engines.



The 3" Der Big Red Max flies great on an E12-4 and is extremely impressive in a baseball or football field.



Space Monkey V-2 is one of my favorites if you adapt it to launch on a D-12.



You can also do what I do and build odd-ball rockets that are not particularly stable and load up the nose weight. however, as others have highlighted, you need a bigger parachute and it is not always easy to make that formula work.
 

mh9162013

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You are absolutely right that mini engines are cheaper than 18mm or 24mm engines -- but by how much? No so much really... $1.89 / engine for minis (Using AC Supply price for 4-pack) and $2.23 / engine for 18mm (using Blast-off Flight Pack - $2.94 if you look at 3-packs of C-engines). Anyway, don't stress too much about cost going up to 18mm. Cost per engine jumps up to $4.50 for D's and $6 for E's.
Great points.

I don't mind going from 13 to 18mm for the reasons you mentioned. But all else being equal, I try to fly minis. And I have a soft sport for 18mm engines, given how those are what I used exclusively when I started out in model rockets.

But yeah, once you get into 24mm, all bets are off when it comes to flying on a budget. So I really, REALLY want to avoid a rocket that needs 24mm engines. However, I also want a rocket "design" that allows for 24mm if I want to move in that direction in the future. I really think the BT-60 size fits that bill perfectly.
 

PSLimo

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Hey Guy's,

Might not be what your looking for but when the wind kicks up I always have a saucer with me.

They're cheap with lots of free plans around and you get a low and loud flight for smaller fields.

 

David_Stack

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What about using the Transition tool on PayloadBay.com to print out a paper template for a transition where the Tube 1 diameter matches your body tube, the Tube 2 diameter is 2x the body tube centerline to fin tip measurement, and the transition length is the amount of 'sweep' from the root of the fin leading edge to the tip?

That would produce a cone that you could slip down over the body tube until it rested against the leading edge of the fins. Lots of drag, minimal weight. Make them out of clear mylar to minimize the visual impact. You could secure it with a few pieces of tape, that way it you could remove it when you are not trying to keep the rocket low and slow...

You'll just need to clearance it to allow the launch rod to pass through/under it.

Quick mock-up using an Alpha III and typing paper:

IMG_1408.jpg
 

mh9162013

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What about using the Transition tool on PayloadBay.com to print out a paper template for a transition where the Tube 1 diameter matches your body tube, the Tube 2 diameter is 2x the body tube centerline to fin tip measurement, and the transition length is the amount of 'sweep' from the root of the fin leading edge to the tip?

That would produce a cone that you could slip down over the body tube until it rested against the leading edge of the fins. Lots of drag, minimal weight. Make them out of clear mylar to minimize the visual impact. You could secure it with a few pieces of tape, that way it you could remove it when you are not trying to keep the rocket low and slow...

You'll just need to clearance it to allow the launch rod to pass through/under it.

Quick mock-up using an Alpha III and typing paper:

View attachment 539666
Intriguing...
 

waltr

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Look at the Quest A3 and B6 motors. High enough initial thrust that slowly decreases for a slower climb to burn-out.


 

David_Stack

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What about using the Transition tool on PayloadBay.com to print out a paper template for a transition where the Tube 1 diameter matches your body tube, the Tube 2 diameter is 2x the body tube centerline to fin tip measurement, and the transition length is the amount of 'sweep' from the root of the fin leading edge to the tip?

That would produce a cone that you could slip down over the body tube until it rested against the leading edge of the fins. Lots of drag, minimal weight. Make them out of clear mylar to minimize the visual impact. You could secure it with a few pieces of tape, that way it you could remove it when you are not trying to keep the rocket low and slow...

You'll just need to clearance it to allow the launch rod to pass through/under it.
I'm having second thoughts...

Not sure making the cone so large at the aft end that it completely blankets the fins is the way to go, there may be a significant loss of stability/guidance. Perhaps make it more of a 'mini skirt' so that at least 1/2 of the fin span is still out in the airflow.

I don't have the latest/greatest version of Open Rocket, but I may try and sim something along these lines to see what the results are.
 

bjphoenix

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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 if a rocket weathercocks right off the rod it can travel a significant horizontal distance and leave your field. Higher altitude flights that go straight up have a better chance of landing in the field.

I went through some of this recently when I found a batch of C6-3 in my gear. It takes a narrow set of characteristics for a rocket to fly well on a C6-3 but reach apogee before the 3 sec delay is over. I had a Baby Berthat kit and some extra BT60 so I put 3 of them around the BB as side pods. This worked reasonably well to add drag, but BT55 would have worked better.

My local club flies occasionally on a small field and a stock Baby Bertha works pretty well for that, as do my Estes Patriot Missile or Estes ESAM on B6-4 motors. Several people fly spool rockets and saucers and they always come back pretty close to the pad.
 

gdjsky01

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First off - low and slow is FINE!!! This is something I have never ever understood. Why is the size of you rocket matter? Why does how high it goes matter? I have never ever understood. I love launching ROCKETS. I get a KICK out of seeing my Flis Dead Ringer or Mudwasp hit 75' and deploy a streamer! Just like I get a kick out of seeing my Sublime on a K550! It's launching rockets that are fun.

Two stage A10-0 to 1/4A3-3T
Edmonds Deltie on 1/2A3
Rose-A-Roc on an A8-3
Big BT70 based rocket on a C11-3 or D12-3


Are 100s of rockets, 1000s, you can launch, have fun, and stay under 500'. The JL altimeters I think fit in a BT50 or bigger. No?

Don't worry
 

gdjsky01

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I love A10-0s! A10-0 to a 1/4A3-3T is cheap decent flight.
As said already
Heli Rocs
Boost Gliders
Rocket Gliders
Odd rockets like Qbits

Fun comes in all sizes!
 

jmasterj

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Thanks!

Pair of mini engines packs quite a punch!!! Max lift 160-170g

I think clustering is cool, but if
once you get into 24mm, all bets are off when it comes to flying on a budget.

then I think clustering is out. I guess 2x A10 is the still the cheapest way to get a 25N spike and keeps the impulse low, though.


As others have said, the key to flying low effectively and safely is drag, drag, and more drag. Gives lots of design space!
 

BigMacDaddy

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Also -- don't fly when it is windy!!! Weather.com has hour-by-hour wind speed estimations (look at hourly forecast and put in the zip code where you are flying).

It is not always consistent with what I experience on the ground or in the sky but good to look for those sub 5mph times.
 

mh9162013

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Also -- don't fly when it is windy!!! Weather.com has hour-by-hour wind speed estimations (look at hourly forecast and put in the zip code where you are flying).

It is not always consistent with what I experience on the ground or in the sky but good to look for those sub 5mph times.
Done and done.

When I decide to launch, I'll try to plan a 2-3 day window around my work and other responsibilities b/c I know launching is very weather dependent.
 

smstachwick

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Great points.

I don't mind going from 13 to 18mm for the reasons you mentioned. But all else being equal, I try to fly minis. And I have a soft sport for 18mm engines, given how those are what I used exclusively when I started out in model rockets.

But yeah, once you get into 24mm, all bets are off when it comes to flying on a budget. So I really, REALLY want to avoid a rocket that needs 24mm engines. However, I also want a rocket "design" that allows for 24mm if I want to move in that direction in the future. I really think the BT-60 size fits that bill perfectly.
BT-60 is what I call the “sweet spot” tube. Short models like the Baby Bertha fly well enough on A motors and are easier to pack than their BT-5 thru BT-55 brethren. Large ones like the Star Orbiter are affordable platforms for practicing advanced techniques.
 

BABAR

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This was BASED on a 20 mm tube and flew on a C5-3 which is a nice motor for big draggy LPR rockets. No atimeter but I don’t think much over 200 feet, check the video.




D7165019-CBA8-4552-934C-F2346FC16EC2.jpeg

another might be a bit higher on the D12-3 but probably would be easily doable on a small field on a C11-3
]

E083122E-6C85-47B9-A749-629E5A7CC1B1.jpeg
 
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BABAR

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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...
Box and ring fins aren’t extremely efficient, which means they are draggy for their size. The box fins in particular have a somewhat unique character for low power rockets, they are pretty easy to put on straight and the rockets tend to have almost no roll, it’s like they are on a rail.

box, ring, and tube fins also have a lesser tendency to weathercock, I believe because while they offer lots of surface area relative to the direction of flight, they sort of block each other from LATERAL wind. It’s a bad trade off for ALTITUDE junkies who want higher and faster, but exactly what you want for low and slow.

because of the minimal roll, they make nice mini video camera platforms.
 

ThirstyBarbarian

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Box and ring fins aren’t extremely efficient, which means they are draggy for their size. The box fins in particular have a somewhat unique character for low power rockets, they are pretty easy to put on straight and the rockets tend to have almost no roll, it’s like they are on a rail.

box, ring, and tube fins also have a lesser tendency to weathercock, I believe because while they offer lots of surface area relative to the direction of flight, they sort of block each other from LATERAL wind. It’s a bad trade off for ALTITUDE junkies who want higher and faster, but exactly what you want for low and slow.

because of the minimal roll, they make nice mini video camera platforms.

Tube fins are pretty easy to make too.
 

mh9162013

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This was BASED on a 20 mm tube and flew on a C5-3 which is a nice motor for big draggy LPR rockets. No atimeter but I don’t think much over 200 feet, check the video.




View attachment 539810

another might be a bit higher on the D12-3 but probably would be easily doable on a small field on a C11-3
]

View attachment 539811

Love that Da Bomb launch!
 
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