Lakeroadster's 2 Stage Alpha Variant

[Daddyisabar]

Put a black stripe up the side to finish the old school look.

 

[lakeroadster]

Put a black stripe up the side to finish the old school look.

 

[Daddyisabar]

The Astron era was really back in the day.

 

[lakeroadster]

The Astron era was really back in the day.

Nortsa Ahpla

 

[jqavins]

I get it, for the reverse swept fins. But what about bring-back clones of other, OOP Astron era kits? It could be a whole Norsta line, because they're retro.

 

[lakeroadster]

I get it, for the reverse swept fins. But what about bring-back clones of other, OOP Astron era kits? It could be a whole Norsta line, because they're retro.

Great idea..

 

[lakeroadster]

Clear Coat

 

[lakeroadster]

T minus soon for the Ahpla launch... Updated the Open Rocket simulations to As Built and created decal sheet.

 

[lakeroadster]

Getting Ahpla ready for launch. Installed the Kevlar and elastic shock chords, friction fit the motor to the sustainer and prepped the booster and booster motor for tape retention by installing shipping tape to both of them where the masking tape will be installed.

 

[jqavins]

[P]repped the booster and booster motor for tape retention by installing shipping tape to both of them where the masking tape will be installed.

View attachment 529338

Would you explain that a bit? I've never heard of using two type of tape for that (as opposed to just adding enough masking tape to the engine to make it tight).

 

[lakeroadster]

Would you explain that a bit? I've never heard of using two type of tape for that (as opposed to just adding enough masking tape to the engine to make it tight).

This is applicable to the tape that is installed on the outside of the motor tube, not the tape used to friction fit a motor.

I wrap clear shipping tape around the end of the motor mount tube and leave it for the life of the rocket. Since it's clear, you really can't see it. Then when you use masking tape for securing the motor you don't have to worry about the tape damaging the paint when the masking tape is removed.​

​

When you go to tape the motor to the body tube (I use BT-50H, the heavier 24mm motor tube) the body tube is of course bigger in diameter than the motor casing, so the masking tape kind of gets wrinkled up on the motor, not ideal contact. So, I wrap shipping tape around the motor tube to build the diameter up, so it is nearly the same as the body tube. Then when you tape the motor to the motor tube, you get a nice smooth wrap of masking tape to secure the motor.​

Again, my oddrocs have heavier than usual nose cones due to a lot of ballast (for stability). So it stands to reason that the ejection force on the motor, and its retention tape, is higher.

 

[BABAR]

Looking great, like the retro AHPLA.

I probably missed it, but what motors are you using and does the sustainer recover on a streamer?


What is mass of full stack with motors and Recovery?

 

[lakeroadster]

Launch Report

We launched Ahpla! today. The rocket flew stable and was recovered undamaged.

A D12-0 booster motor & a D12-5 sustainer motor was used. Winds were from the south, maybe 5 mph.

Recovery was planned to have the booster as a tumble recovery, and the fuselage and nose cone come down together via an 18" nylon parachute. But The Rocket Gods decided to intervene. For reasons I still can't contemplate, other than user error, the Kevlar shock chord that I had routed down and out the bottom of the rocket, and then looped around the sustainer motor extension, just came loose?

And with two D motors and some weathercocking, the rocket was over 1,000 feet from the launch pad when this occurred.

When the booster motor stopped, and the sustainer motor lit... ole Ahpla was haulin' the mail.

The rocket did weathercock, quite a bit.

Sustainer:

Due to the sun being behind me I could see the fuselage falling and the white fins would flash as the sun hit them. I followed it visually until it ground hit and made a mental note of 2 close trees and a fence post that were in line with the fuselage.​

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I then looked skyward for the parachute that had the nose cone attached. I spotted the 9-foot long red crepe paper streamer I used as wadding floating in the air and looked just west of that and spotted the purple 18" chute. I followed it visually until it ground hit and made a mental note of a large cluster of bushes and a fence post that were in line with the parachute.​

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It took a little while to reach the sustainer components, hazards included waste high weeds and jack rabbit burrows. We jumped up a jack rabbit, but he wasn't helping with the search.​

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The sustainer components were about 1,056 feet south from the launch pad​

Booster

The booster landed about 90 feet northwest from the launch pad. It appeared to be spinning... I would have liked to have got a good close up photo but was preoccupied with not losing sight of the sustainer.​

The Money Shot....

 

[jqavins]

We jumped up a jack rabbit, but he wasn't helping with the search.

Lazy, inconsiderate rodent!

 

[BABAR]

Congrats!

Suggestions for future launches.

D12-0 is a great workhorse for getting full stack off the pad with authority. Given the altitude you got before staging however, you may get my with a C11-0 IF stack weight is under 170 (but I doubt this, you build strong.)

What you almost certainly CAN do it downsize the SUSTAINER to an 18 mm motor, either with a store bought adapter (the Estes ones are well designed) or given your skills you can whip one out of a BT-20 and tape in five minutes. I really like 18mm A8-3 or A8-5 for sustainers, they have a big bore and therefore stage easily. I like small motors in sustainers for many reasons, one of which is the weather cocking. Once the stack gets off vertical, when sustainer fires it means a long walk, unless you fire into the wind and get lucky (I don’t recommend it, my experience with multistage is that firing into wind makes MORE weathercocking.)

The smaller motors weigh less, so they also increase stability.

Given your forward swept fins on the sustainer, you can also swap out for a streamer. It’s what I like about forward swept fins, they impact motor casing first, so they can handle a faster descent rate.

 

[lakeroadster]

D12-0 is a great workhorse for getting full stack off the pad with authority. Given the altitude you got before staging however, you may get my with a C11-0 IF stack weight is under 170 (but I doubt this, you build strong.)

Total weight with D12's is 14.1 ounces. Total Weight with a D12 Booster and a C6-5 is 13.4 ounces.​

​

I had to add a lot of nose ballast to make the rocket stable with the ring finned booster in place.​

What you almost certainly CAN do it downsize the SUSTAINER to an 18 mm motor, either with a store bought adapter (the Estes ones are well designed) or given your skills you can whip one out of a BT-20 and tape in five minutes. I really like 18mm A8-3 or A8-5 for sustainers, they have a big bore and therefore stage easily. I like small motors in sustainers for many reasons, one of which is the weather cocking. Once the stack gets off vertical, when sustainer fires it means a long walk, unless you fire into the wind and get lucky (I don’t recommend it, my experience with multistage is that firing into wind makes MORE weathercocking.)

The smaller motors weigh less, so they also increase stability.

Agreed. I had originally planned to use a C6-5 for the 1st flight to get an apogee of about 600 feet. But I threw caution to the wind (literally) and went for the 1,000 foot mark!​

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You're comment about tilting the rocket into the wind, and an increase in weathercocking is interesting.​

Given your forward swept fins on the sustainer, you can also swap out for a streamer. It’s what I like about forward swept fins, they impact motor casing first, so they can handle a faster descent rate.

You know, I think The Rocket Gods may have been listening to me.​

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I have written before that for a rocket with a heavy nose cone will benefit from a parachute for the nose cone, and a separate recovery device for the fuselage. And that's the way this first flight panned out.​

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Tumble recovery works fine on this design, It's a double wall body tube, the fins are swept forward, the motor sticks way out the back, and it's a TTW design with 3 ply basswood fins.​

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But a streamer would add to the cool factor and make finding the fuselage easier.​

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Thanks for the suggestions.... they are sincerely appreciated.

 

[lakeroadster]

Designing A Ring Fin Using Open Rocket, a post flight review....

Spurred on by this discussion, I created Open Rocket "as built" configurations of the AHPLA with the following Ring Fin designs:

A Ring Fin made out of a:

• Inner Tube
• Body Tube
• Ring Fin
• Regular fins as outlined per Bruce Levison's article in Issue 27 of the Apogee Newsletter

The summary of the above Open Rocket Simulations is shown below:

Keep in mind this is for a rocket that swing tested as very stable, flew stable and didn't weathercock.

Looking at the data and comparing it with the flight, I think the Bruce Levison Ring Fin Hack provides the most accurate results.

​

 

[neil_w]

As posted on the other thread, the inner tube version is not intended to produce an accurate sim on its own. It must be supplemented by additional fins.

 

[jqavins]

Designing A Ring Fin Using Open Rocket, a post flight review....

Spurred on by this discussion, I created Open Rocket "as built" configurations of the AHPLA with the following Ring Fin designs:

A Ring Fin made out of a:

• Inner Tube
• Body Tube
• Ring Fin
• Regular fins as outlined per Bruce Levison's article in Issue 27 of the Apogee Newsletter

The summary of the above Open Rocket Simulations is shown below:

Keep in mind this is for a rocket that swing tested as very stable, flew stable and didn't weathercock.

Looking at the data and comparing it with the flight, I think the Bruce Levison Ring Fin Hack provides the most accurate results.

View attachment 537870​

View attachment 537873View attachment 537872View attachment 537871View attachment 537874

If you post the design file, I'll see if I can coax my dying computer to stay up long enough to try RockSim's ring tail as a point of comparison. (Not that it's perfect, of course, but it's bound to be better than any of the three cosmetic options in OR, and I wonder how it compares to the Levinson method.)

 

[lakeroadster]

If you post the design file, I'll see if I can coax my dying computer to stay up long enough to try RockSim's ring tail as a point of comparison. (Not that it's perfect, of course, but it's bound to be better than any of the three cosmetic options in OR, and I wonder how it compares to the Levinson method.)

Rocksim has a ring fin option?

 

[jqavins]

Yup.

When I picked up the hobby in about 2000, it was because a close friend turned me on to the RockSim free demo. At that time the program cost $99 if I remember right. When the trial period ended I tried out OP, and it didn't seem mature, so I spent the money. Since then, I've paid once, not much, for one of the major version updates, and I certainly do feel that I've got my money's worth.

That said, OR seems to have come a long way since then, and if I were starting now I would not buy RS. But then, I also wouldn't have ringtails.

 

[lakeroadster]

Ho, Ho, Hold On There?

 

[lakeroadster]

I am not The most scientific on my design and construction. I have RockSim and OpenRocket and have never really used them. I can claim a partial excuse because most of my designs are square or triangular cross sections or have other weirdnesses that don’t lend themselves to sims (the rest is pure laziness on my part.)

that said, I probably have more experience with scratch built gap stages than most.

tenets I subscribe to are as follows

at least two vents, equally spaced, so there is no net lateral force from the staging gas that might throw the rocket off kilter. I have no evidence it makes any difference, I just do it.

I DO believe the position of the holes relative to the sustainer IS critical, the holes should be just below the nozzle of the sustainer. Depending on how you “mate” the sections, the holes can be in the sustainer, the booster, or both. If you are not going minimum diameter, I DO believe it helps to extend the internal motor mount to “duct” or route the hot gases so they illuminate the nozzle on their way out. My sustainer ignition rate is pretty much 100%, my major failure has been when I tried to extend the gap from 53 to 72 inches. 53 worked in flight multiple times, 72 worked on a test stand but failed in flight, not sure why. I was using a D12-0 on the booster, I now have some F15-0s and hope soon to try a build with a 72” gap.

as for the size of my holes, I just use a regular Note paper size hole punch, not for any scientific reason, just because it’s convenient.

If you have enough room, you could vent through the centering rings out the back of the booster if you don’t want to put visible holes on the outer body tube. Then you might want the booster to have a longer motor central tube that gets closer to the sustainer nozzle.

depending on how close they are, you might not need a vent, but it does help, this 24mm stager does not appear to be vented and it has a short gap between the motors, for example:
https://www.apogeerockets.com/Rocket-Kits/Skill-Level-3-Model-Rocket-Kits/Rip-Roar

I was re-reading this thread today and wanted to point out that I did not drill any vent holes for staging. CHAD says no worries.

 

[lakeroadster]

Decals... I contacted Tango Papa and he was gracious enough to change the scale of the standard Estes Alpha decal sheet so it would fit a BT-55.

​

 

[lakeroadster]

Clear Coat

 

[Daddyisabar]

At the build and fly yesterday a little girl at the table was trying to put her Alpha three plastic fin can on backwards. Who was I reminded of????

 

[lakeroadster]

At the build and fly yesterday a little girl at the table was trying to put her Alpha three plastic fin can on backwards. Who was I reminded of????

Awesome. Wise little gal. Prevent those thin little fins from breaking on ground contact.