F impulse altitude record

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n27sb

N27SB
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A few months ago I decided to go after the F impulse altitude record at NEFRAM in Bunnell, Florida. I scratch built a 24mm airframe with carbon fiber. Wall thickness was .018".
This build was going to have to be light and clean but due to the altitude I opted for dual deploy and RF tracker. Since no body builds a long nose cone I would have to build that as well. The fins are .015" CF. The existing record is 2655' and it has to be beat by a minimum of 5%.
I will post pictures of the build and the results.
 
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2655 should be easy to beat. I held the TRA F record a long time ago using a cardboard tube and plastic nose cone, was 4000 something . There is no TRA record for F now due to the rules being changed but the old record was set using a rocket similar to yours at 6785'.

M
 
I've been dabbling with the F record for years now. I have always found that this particular flight is more difficult than people might think. Looking forward to your build and results.

Jim
 
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A few months ago I decided to go after the F impulse altitude record at NEFRAM in Bunnell, Florida. I scratch built a 24mm airframe with carbon fiber. Wall thickness was .018".
This build was going to have to be light and clean but due to the altitude I opted for dual deploy and RF tracker. Since no body builds a long nose cone I would have to build that as well. The fins are .015" CF. The existing record is 2655' and it has to be beat by a minimum of 5%.
I will post pictures of the build and the results.
I'm not sure where you got you record information but it is incorrect.

The existing NAR F Alt record with an altimeter is 1701 meters = 5581' set on 8/19/13 by Darrell Smith with a F10-8 Apogee using a Perfect-Flight/Pnut as the altimeter. Ref. https://www.nar.org/contest-flying/records/

The old NAR F Alt record using theodolites is 1741 meters = 5712' set on 9/27/81 by Doug Frost

Bob
 
This is a record at a local club in Florida. NEFAR The problem that arises is that you have to recover the rocket. So setting a record in a desert is somewhat easier than in an area with limited recovery area.
I easily flew to over 3000' at a field in Tampa but they do not have club records.
Thanks for the interest.
Steve
 
I've seen a few of the sub-G impulse record attempts at Tripoli Colorado over the years. Starting at 8800' is almost an unfair advantage.

Edward
 
I've seen a few of the sub-G impulse record attempts at Tripoli Colorado over the years. Starting at 8800' is almost an unfair advantage.

Edward
The theodolite NAR G Alt model rocket record is 2641 meters = 8664' set on 3/15/08 by Jonathan Dunbar at an unspecified location.

https://www.nar.org/contest-flying/records/

The Tripoli Single Motor G altitude record is 8796' = 2681 meters set on 10/20/2013 by Chris Franco using a CTI G150BS at October Skies, Fresno, California.

https://www.tripoli.org/Membership/CompetitionsandRecords/GSingleMotorRecord/tabid/342/Default.aspx

The apogee of these flights did not even reach the Tripoli Colorado 8800' base altitude so it is an unfair comparison if your home field is at or near sea level because the drag at 8800' is only 76.7% that of sea level.....

https://www.aerospaceweb.org/design/scripts/atmosphere/

The OOP stock built Rocket Vision Mach Buster, Spit Fire and Check-Six 24 mm model rockets would apogee with a Rocket Vision F72 from nearly 5000' with the Mach Buster to over 4000' with the Check-Six. The problem was finding them after a flight.......

I launch at sea level and that's how I lost mine......

https://www.rocketreviews.com/reviews-1089.html

Bob
 
Thanks Bob, That gives me something to shoot for. You are right, finding them is the challenge. I have room for a tracker but everything adds weight.
This is the booster section at 1.3 oz

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photo 1-2.jpg
 
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2655 should be easy to do with a F10 from Apogee
That'd be my choice, and it was the current NAR record holder's choice (according to Bob above) but it is not Steve's. In the OP he stated he's going 24mm, but the F10 is a 29mm engine.

Should't this thread be in the mid power forum?
 
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The tracker is more important than the rail guides.


Agreed. Serious altitude rockets do not use rail guides or launch lugs, they are launched from towers. Guides and lugs make it so you might as well not try they add so much drag. You'd think the air would just slip and go through a lug but it doesn't. Something like a pressure wave develops and it's like you stuck a flat object into the airstream.

Run sims, too. It might be possible to build too light and not have the mass to attain max altitude. This is easier to do when working with Hi Power rockets, not so much in the lower powers ranges but can still be a factor. Light weight is a ultimate speed thing, then lighter is better.
 
Not necessarily. The Tripoli F-impulse record was obtained with a high power F motor.

Another point to mention is that when you are going for an altitude record, there is an optimum lift-off weight to obtain maximum apogee altitude.

If the rocket weight is too low, the rocket goes too fast so you have excessive drag losses and not enough retained momentum to coast to the highest possible apogee. Conversely if the rocket weight is too high, the rocket will not achieve the optimum speed to take advantage of the retained momentum created by the greater weight.

The optimum weight is also thrust dependent so make sure you do your sims for the motor you plan to use in the record attempt.

Regardless of rocket weight, you must minimize drag. The most significant drag contributor for minimum diameter rockets is the launch lug or rail buttons. Any serious altitude record attempt must be launched from a tower and might possibly employ a piston launcher as well.

Bob
 
You could also consider fly-away rail guides.


Since you'll have to make your own, the method described in the last link would probably be best, assuming you can get access to a laser cutter and any help you might need using it. If you don't have access, Tim's first method can be improved on by the simple addition of short pieces of very small diameter tubing along the portion of the piano wire that rides along the rail. That way, the guide rolls up the rail instead of sliding. A little powdered graphite inside the little tube rollers wouldn't hurt either.
 
Not necessarily. The Tripoli F-impulse record was obtained with a high power F motor.

Another point to mention is that when you are going for an altitude record, there is an optimum lift-off weight to obtain maximum apogee altitude.

If the rocket weight is too low, the rocket goes too fast so you have excessive drag losses and not enough retained momentum to coast to the highest possible apogee. Conversely if the rocket weight is too high, the rocket will not achieve the optimum speed to take advantage of the retained momentum created by the greater weight.

The optimum weight is also thrust dependent so make sure you do your sims for the motor you plan to use in the record attempt.

Regardless of rocket weight, you must minimize drag. The most significant drag contributor for minimum diameter rockets is the launch lug or rail buttons. Any serious altitude record attempt must be launched from a tower and might possibly employ a piston launcher as well.

Bob

I used to own the rocket in the pic. It was right at the optimum weight, even with a tracker and altimeter. I could never get it to fly straight up. One time, it even did loops - it was just too sensitive to the wind when flown on an F10. I lost it before I got a good flight.

Not long ago, I flew a prior version of the rocket (since I still owned the rocket and had leftover F10's). It didn't have swept fins and was just a bit over the optimum weight. I got one decent flight from it, which was to 5,825 feet from a launch site not far above sea level, but then I lost that rocket too.

Anyone need a leftover F10?

Jim

Straight Arrow.jpg
 
Not necessarily. The Tripoli F-impulse record was obtained with a high power F motor.

Another point to mention is that when you are going for an altitude record, there is an optimum lift-off weight to obtain maximum apogee altitude.

If the rocket weight is too low, the rocket goes too fast so you have excessive drag losses and not enough retained momentum to coast to the highest possible apogee. Conversely if the rocket weight is too high, the rocket will not achieve the optimum speed to take advantage of the retained momentum created by the greater weight.

The optimum weight is also thrust dependent so make sure you do your sims for the motor you plan to use in the record attempt.

Regardless of rocket weight, you must minimize drag. The most significant drag contributor for minimum diameter rockets is the launch lug or rail buttons. Any serious altitude record attempt must be launched from a tower and might possibly employ a piston launcher as well.

Bob
Ok, so here's the deal, I originally built this rocket to use up a box of f32-t motors and see if I could build a 24mm dual deploy. I decided to go ahead and break a few local records. After getting some feedback from all of you I have started to get the bug to get serious. So I think I will start over with a 29mm frame and run some sims on the f10.
 
I used to own the rocket in the pic. It was right at the optimum weight, even with a tracker and altimeter. I could never get it to fly straight up. One time, it even did loops - it was just too sensitive to the wind when flown on an F10. I lost it before I got a good flight.


Jim

Beautiful rocket Jim, nice CF work!
 
Ok, so here's the deal, I originally built this rocket to use up a box of f32-t motors and see if I could build a 24mm dual deploy. I decided to go ahead and break a few local records. After getting some feedback from all of you I have started to get the bug to get serious. So I think I will start over with a 29mm frame and run some sims on the f10.
No. Please stick with the 24 mm there are many more options especially with CTI 24 mm motors, and read Jim's comment on the F10. The available ejection delays are not optimal (too short) for a really high flight, and the F10 has very low thrust and will not fly straight in wind which I think you have a lot of in FL.

The OOP Vaughn Brothers Extreme 24 would be a very good starting design to use. It has enough room for a tracker and dual deployment or a very long streamer. It is cheap to build as it used a 24 mm motor tube as the airframe IIRC and used thin FG (I would use CF) fins. The following attachment from TRF shows the VB Extreme family of Rockets.

https://www.rocketryforum.com/attachment.php?attachmentid=157016&d=1387503933

I think you will be a lot happier.

Bob
 
No. Please stick with the 24 mm there are many more options especially with CTI 24 mm motors, and read Jim's comment on the F10. The available ejection delays are not optimal (too short) for a really high flight, and the F10 has very low thrust and will not fly straight in wind which I think you have a lot of in FL.

https://www.rocketryforum.com/attachment.php?attachmentid=157016&d=1387503933

I think you will be a lot happier.

Bob
Good advice, I think I will listen to you guys for a few days before I stir some epoxy.
 
Out of curiosity, is there an optimum stability margin to shoot for? I realize that too great a margin means excessive fin drag and too little means you don't go straight enough to go high but where is the sweet spot? Also it seems that most of the high runners have some sort of clipped delta fin design which makes sense by is there an optimum sweep angle?
 
Out of curiosity, is there an optimum stability margin to shoot for? I realize that too great a margin means excessive fin drag...
Not necessarily. A rocket can have excessive stability margin with small fins if it is quite tall and/or nose heavy. The reaason it's a bad thing is that it leads to excessive weather cocking.

A decent rule of thumb, and not a perfect optimum, is that anything from 1.25 to 2.00 calibers is probably OK. I doubt there is a perfect optimum, since static margin is just one measure or really complex dynamics; with all the variables to consider you really can't say that tbere is any perfect value for any single one of them.
Ok, so here's the deal, I originally built this rocket to use up a box of f32-t motors and see if I could build a 24mm dual deploy. I decided to go ahead and break a few local records. After getting some feedback from all of you I have started to get the bug to get serious. So I think I will start over with a 29mm frame and run some sims on the f10.
No. Please stick with the 24 mm there are many more options especially with CTI 24 mm motors, and read Jim's comment on the F10. The available ejection delays are not optimal (too short) for a really high flight, and the F10 has very low thrust and will not fly straight in wind which I think you have a lot of in FL...
I used to own the rocket in the pic. It was right at the optimum weight, even with a tracker and altimeter. I could never get it to fly straight up. One time, it even did loops - it was just too sensitive to the wind when flown on an F10. I lost it before I got a good flight.
Good advice, I think I will listen to you guys for a few days before I stir some epoxy.
It's tempting to say "Make up your mind," but actually my message is "Don't make you mind. Not yet." Do up the design in OR (or RockSim; I think you mentioned OR previously) and do sims, sims, and more sims. Then make up your mind. For runs on the F10, pay attention to the speed at the end of the launch guide.

Anyone need a leftover F10?
If you're serious, PM me. But of course, you do't need to be serious; it's your motor.
 
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Thanks for all for the great information. I ran a bunch of sims on Rocksim last night and found some interesting trends. This will be old news to those that have tread this path before.
24mm designs on a long burn CTI (F30) outperform 29mm designs on a Apogee (F10).
The lighter I went the better. Actually I went lighter than I can build.
Both version had more than adequate velocity at launch. (More than 70 f/sec @60")
The shorter I went the better. I went shorter than I can fit everything in.
Neither motor combination had enough time delay to maximize altitude. 13 seconds. Electronic deploy is required. (The added weight still exceeds short factory delay)
A CTI F51 classic with 12 sec. factory delay could be used but an altimeter is about the same weight as an altimeter/deploy combo.
Thank you Jim for the tips on length, weight and fin style.
On Rocksim I always dirty up the fins and nose to make it yield realistic results.
At sea level on a good straight flight it could exceed 6000'.
Any comments are welcome.

One last note "You have to find the rocket"
 
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Telemini v1.0 is your best bet for altimeter/deployment/tracking in a small package. The downfall is its overall length due to the antenna, but you seem like a creative guy!
 
The Telemini is an option. In the past I have used an Easymini with a Falcon tracker. The tracker gives location right down to a foot away but lacks range. The Telemini has range but how close can it get you in heavy brush? If I make the nose cone long enough I might be able to use both tele mini and tracker. Signal interference may be an issue. Probably put the tele mini antenna in the nose and tracker whip out the bottom.
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If you don't get the rocket back it don't count!
 
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Thanks Bill, you were already on my list but I noticed that you don't make 24mm.
Just layed up the BT for this little guy and after trim out it will be under a 1/2 oz. OD is about .970
I would be happy to pay you for a set or make you some CF BT or nose cone.
Nose cone halves glassed and bagged. I love days off.



photo 1-3.jpgphoto 2-3.jpg
 
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