Lowballing an Estes PS2 Prowler

Hi Everyone,

I have an Estes Prowler, my first 29mm kit. I've flown it a few times, and wow! does it move. It flies to 900 feet on even an E16-6 BP, and I've flown it on both Aerotech F20s and F27R's. In the latter two cases, it it well over 1600 feet, and I'm sure I could put it a lot higher with a G motor.

The trouble is, if I am going to fly it in my nearby park, I actually want to keep the altitude down. Under 800 feet if I can. I flew it once in the park on an F27-8R, and I had calculated that it might go about 1000ft... I was off. Way off. It went 1600 ft, and on a perfectly still day landed on the lawn of a nursing home to the north of us:

[video=youtube;ykrs90n3zxQ]https://www.youtube.com/watch?v=ykrs90n3zxQ[/video]

My challenge for this rocket is to use a motor that will keep it under 800 feet for these local launches.

The constructed rocket is heavier than its list weight (10oz, rather than 9.1), is 2" in diameter, and it's drag coefficient is pretty low. 0.3 seems to match the altitudes I am getting with it.

I am thinking of getting an adapter for using some 24mm motors on it, but I am not sure what I should be looking for.

Any suggestions?

ThrustCurve.org shows a CTI 24mm E75 taking it to about 692 feet. That's a 1-grain VMAX. Unfortunately, you'd want a 6s delay, but the drilling tool will only get you down to 8s.

Estes makes plastic adaptors for using 24mm in 24mm. You can get em pretty cheap in a two pack. Aerotech has a single use E20W that Sims to around 600 in my partizon, haven't launched yet though and its a bigger rocket. I haven't simmed it, but I would guess 800 foot or so for your Prowler. Thrustcurve says that engine fails because liftoff speed is too slow at 44 ft/second, I have several rockets that sim at 41 or 42 ft/s off the rod and they fly just fine. Check out other Aerotech single use 24mm too. If you have 24mm hardware, then look to reload too.

Mike

10 ounce weight you could probably get away with a 24mm E12 black powder. Or even D12-3, as my DRT has flown on that and it weighs 10 ounces.

An alternative to smaller motors would be : you could add a thin metal plate to the back end, and a matching weight on the front end.

Not sure how useful that might be, but it's an option.

dhbarr said:

An alternative to smaller motors would be : you could add a thin metal plate to the back end, and a matching weight on the front end.

Not sure how useful that might be, but it's an option.

Click to expand...

Well, you can't just add weight and go launch. You have to be concerned about having enough thrust. The unfortunate reality for many rockets is that the motors that have enough thrust to get them going also have enough impulse to get them up high.

an E28, or E30 would probably do the trick(high thrust, short duration).
Rex

Bat-mite said:

Well, you can't just add weight and go launch. You have to be concerned about having enough thrust. The unfortunate reality for many rockets is that the motors that have enough thrust to get them going also have enough impulse to get them up high.

Click to expand...

Definitely ; I'm suggesting balanced drag within available TtW ratio margin.

If it was only 9 oz. it would be almost the same as an Estes D-Region Tomahawk, made for the 24 mm BP motors. At 10 oz., you'd need a 6' rod for the E9-4 (done it) but the E12 no problem (the peak thrust is higher than the F15). E20 would probably go higher than E16 and F32 (24mm) higher than F15.

10oz.!!! Holy cow! That's lighter than some of my birds that safely reach 350 ft. on a D12-3!

A 24mm E20-4 should safely fly it and keep it in the park easily. Just use an adapter.

My 2.6" TLP Martel weighs 14.3oz. with an E20-4 in the tube, and is likely a bit draggy-er than your prowler, but jumps up to about 500ft. without any hesitation.
My park where I fly is smallish, so this is as far as I push it with a rocket that uses a chute' for recovery.

[video=youtube;FHFeGZLoORE]https://www.youtube.com/watch?v=FHFeGZLoORE[/video]

Thanks for the input so far. I guess my main concern is the thrust-to-weight ratio. I also have a Maxi-Alpha 3 that's been enhanced with a few parts including a Nomex parachute guard and a swivel, same as the Prowler. It comes in closer to 8.5oz. I've launched it on a D12-3, which puts it at a lower but a reasonable height. In this case, I have the stock launch rods that came with the MA3 kit, and the Prowler kit. They are 3/16" and 1/4" rods respectively, but I think they're too short for the job. The 3/16" rod is 3.5' while the 1/4" is only 4'. I think I had better be looking to a local metal supplier to get a longer rod.

Of course, I really should bite the bullet and order a rail and some rail buttons...

I am surprised no one has suggested a Chute Release. Use the E16-6 and let it fall to a low altitude before chute deploys.

https://www.jollylogic.com/products/chuterelease/

dhkaiser said:

I am surprised no one has suggested a Chute Release. Use the E16-6 and let it fall to a low altitude before chute deploys.

https://www.jollylogic.com/products/chuterelease/

Click to expand...

Not saying they are not worth every penny and more, they likely are, but that's an expensive solution.
I know I certainly would love to get one, but not on my budget anytime soon.

If he can afford one then yeah, that's a great solution, but if he can just buy some different motors and make an adapter...

Flyfalcons said:

10 ounce weight you could probably get away with a 24mm E12 black powder. Or even D12-3, as my DRT has flown on that and it weighs 10 ounces.

Click to expand...

As an experiment/test I flew an Estes PSII Ascender on an D12-3 motor.

I won't do that again!

The model was flown off a six foot launch rod but it just sort of 'lobbed' into the air.
It recovered fine.

I do not recommend it.

Initiator001 said:

As an experiment/test I flew an Estes PSII Ascender on an D12-3 motor.

I won't do that again!

The model was flown off a six foot launch rod but it just sort of 'lobbed' into the air.
It recovered fine.

I do not recommend it.

Click to expand...

Here is 11.75oz. fully loaded D12-3 goodness. https://www.rocketryforum.com/showt...Mixer-24mm-Scratch-Build&highlight=Meow+Mixer

[video=youtube;aV2wJpxYD2c]https://www.youtube.com/watch?v=aV2wJpxYD2c[/video]

Girl in the background was riding by on her Horse, and thought I was launching fireworks, and that they would "Spook" the dumb Horse.

TopRamen said:

Here is 11.75oz. fully loaded D12-3 goodness.

Click to expand...

My Ascender with D12-3 and adapter had a launch mass close to 14 oz.

Initiator001 said:

My Ascender with D12-3 and adapter had a launch mass close to 14 oz.

Click to expand...

Yeah, that's even beyond my weight threshold, so I imagine it was not pretty.
11.75 is as heavy as I'll go at that motor.
It works out ok on a smallish airframe.

Life is easy on my rockets.
I only expect them to go straight up and not twist, then deploy their recovery gear as near to moment of apogee as possible.
I can do all this in my mind, but having simulators makes it exciting.
The two rocket flights I've posted in this thread were ones I did not do computer stuff on.
Thus, no "Build Threads".
Just, "Don't tell me it won't work, because it ALREADY did."
Things get hairy when you start second guessing yourself, and you get hooked on the Sims.

D12-3 in a 7oz. rocket.:

[video=youtube;4maIkJfQ2tQ]https://www.youtube.com/watch?v=4maIkJfQ2tQ[/video]

Can't comment on the indignant horse rider, but those videos are helpful. At the moment, I think if I get 6' rods in both 3/16" and 1/4", I should be okay in putting the smaller motors in, including the D12-3. That being said, I should also look at getting a 6' launch rail...

If you gonna be ordering a rail, you may as well grab an 8 footer. Amazon has the rails in 8 foot lengths by Fastek and 80/20 for around the same price, once shipping is figured in. When I ordered I checked McMaster and a few other places and the all came out within a couple bucks of each other. That's probably not much more than a 6 footer. Mine is 4 foot but if it was 8 I would have more engine options for, as you say, lowballing.

FWIW I have Fastek brand T slot "rail" and Fastek brand T nuts, and the T nuts didn't fit their own T slots. I had to grind em down. But on the other hand, I have about 50 T nuts ground down and I only used 2. So if you need any...

Mike

TopRamen said:

Here is 11.75oz. fully loaded D12-3 goodness. https://www.rocketryforum.com/showt...Mixer-24mm-Scratch-Build&highlight=Meow+Mixer

Girl in the background was riding by on her Horse, and thought I was launching fireworks, and that they would "Spook" the dumb Horse.

Click to expand...

No natural enemies and scared of their own shadow. You sneeze and they go ape*$%!.

MikeyDSlagle said:

No natural enemies and scared of their own shadow. You sneeze and they go ape*$%!.

Click to expand...

We have horses. It's my wife's deal. They are bat-sh crazy. One of them was spooking at our dog the other day. Smh

I picked up the Prowler kit a couple of years ago for my daughter.. she likes pink. We've only launched it a few times so far with BP F15-6's. It went very high. However, I noticed it seemed a little unstable going up with a little spiral for a moment. I noticed on your two videos with the F20 and F27 that your prowler appears to be a bit squirly, but on the E16 video it looks rock solid. I have it my mind that the extra motor weight is bringing down the stability margin. So, I made and open rocket model of the one I built and, as I suspected, it appears that the stock build is only marginally stable... well less than 1 cal at just 0.411 cal with the F15-6 loaded.


I tried to upload my .ork file too.. but for some reason, that file is 272kb...and over the upload limit.

Your ork is full of sim. Save a copy, drop the motors, double check that your sims are washed away

^^-- good call, except just go save as, right side check "only primary figures".

dhbarr said:

Your ork is full of sim. Save a copy, drop the motors, double check that your sims are washed away

Click to expand...

bill_s said:

^^-- good call, except just go save as, right side check "only primary figures".

Click to expand...

Thanks for the tips.

Here's the Open Rocket File:
View attachment Estes Pro Series II Prowler kk stock build CA & Epoxy Primary Figures Only.ork

And a screen capture of the Prowler on and F15-6 including the stability margin:

This was really helpful. Thank you! At this point, I don't have and have never flown my prowler on an F15-6. Just the E16-6, and the Aerotech F20-7W and F27-8R. Looking at this, the F23-7FJ would put it at 1650.

Mind you, according to this, a D12-3 has a faster speed off the rod than an E16-6. Something to pay attention to...