Estes Pro Series II Doorknob Build

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Nytrunner

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A smaller diameter motor of the same impulse as a larger diameter motor will often have a longer core which can often translate to more thrust (abd shorter burn) than the larger diam motor
 

Spitfire222

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Thank you for the information, I'm still learning the intricacies of motor selection, as all of my experience so far is A-D motors, where it's relatively easy to choose an option that will work fine.

Just to double check, can anyone confirm that 1.35 cal is sufficient, and that I don't necessarily need to add any weight in the nosecone? Thanks for all of the help so far!
 

Spitfire222

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The last item to button up was to epoxy in the nosecone bulkhead, and then attach the shock cord to the eyebolt. With that completed, the rocket is officially finished! I've gone ahead and ordered some E30s and F44s based on the advice of others in this thread and from the Open Rocket simulations. Hopefully they work well! I'll keep this thread updated with flight reports when the motors arrive and I'm able to get out and launch this one. Thanks everyone for your interest and replies, hope you enjoyed the build! :)
 

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lowga

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Best build thread posted on TRF in a long time! Nicely done sir. But you're not finished yet. We need to see pictures or even better, video of this gem in flight.
 

Spitfire222

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I will definitely post photos and videos when this model flies for the first time! Awaiting for the motors and 29mm to 24mm adapter to arrive still. Until then, if anyone knows of upcoming club launches in Virginia, please let me know!
 

Theory

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VERY NICE!!!!

if i may ask, what was your final weight (recovery and all) w/o motor?
 

Spitfire222

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VERY NICE!!!!

if i may ask, what was your final weight (recovery and all) w/o motor?
Thank you! The final weight without motor is 358 g, or 12.6 oz. I have some composite motors on order for it which should work well based on Open Rocket simulations. You very well may see this rocket launch in person, as I've been looking for nearby club launches! Please let me know when you guys launch next, the drive shouldn't be too bad.
 

Scott_650

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After overriding the weight and CG in OR, the estimated stability is 1.35 cal, which sounds just right, and means that I will not add the weight in the nosecone. Further, I ran the simulations using multiple different sized motors, from a D to an F. I was getting somewhat low velocities off rod, so I edited the simulations to a 48” rod, which improved the VOR. Still, it looks like my plan to have first flight on Estes BP E16s or F15s might not be feasible, and that it looks like I’ll have to pick up some Aerotech F20s and F23s. If anyone has a minute, I would appreciate any insight into my Open Rocket results, and thoughts on my conclusions for nose weight and motor selection. Thank you!
Even though you’re pushing the total weight limits for the Estes BP 29mm E motor as long as you stick with 48” rail/rod length and low to no wind an E16-4 should work fine for a first flight. Yes it’s coming off the rod/rail a bit slow just keep in mind you’re going to need calm conditions and it’ll fly fine. I’ve flown my Estes PSII Mammoth on adapted 24mm BP motors many times off a 48” rod in calm conditions - straight as an arrow flights with no wobbles even though it sims very similar to your BP E16 results. Great build thread - the clear steps on the nose cone mod are greatly appreciated! Good luck on your first flight.
 

Theory

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Thank you! The final weight without motor is 358 g, or 12.6 oz. I have some composite motors on order for it which should work well based on Open Rocket simulations. You very well may see this rocket launch in person, as I've been looking for nearby club launches! Please let me know when you guys launch next, the drive shouldn't be too bad.
that wold be awesome!

not sure when i am going to make it back out to NOVAAR. with all this virus stuff things have been a little different lately. hopefully by fall i get back in the sky!
 

BSNW

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LORDY, you did a fine job on that rocket! Well done.

I got one to build too and I am looking to use the RMS F24W. Wow, I hope mine comes out at least half as good as yours. Nice job man, I hope you get many fun flights out of it!!

Andrew K.
 

BSNW

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I also think the RMS F40W would be a great motor for this rocket.
Andrew
 

o1d_dude

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F50 for the win.

I fly everything I can on F50 or F67 at our LPR/MPR launches. Most of my rockets will stay under the 1500' ceiling while still giving a nice boost with plenty of fire and smoke. Then again, I have overbuilding tendencies because I only want to build them ONCE.

What's the all up weight of your Doorknob (airframe, recovery...no motor) If you posted it, I missed it. Sorry.

Asking because I have a Doorknob kit and the upgrade from @Big_Red_Daddy.

EDIT: NVM. Spotted it. 12.6oz. That's light by my standards. Please feel free to ignore my F50/67 suggestions.
 

Spitfire222

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Thank you for the comments! I received the package I ordered with a pair of E30-7s and F44-8s, along with a pack of Estes 29mm to 24mm adapters. I test fit everything, and it all works fine. However, after looking at the performance specifications of the F44s, I'm concerned that I purchased the wrong delay. The specs say that the maximum recommended weight for the 8 second delay is 284 g, which is significantly lower than the 358 g my rocket actually weights (ready to launch, without motor). The minimum weight for the 4 second delay is much higher, at 453 g. I chose the delays based on the Open Rocket simulations I performed using these engines, and it seemed like the longer delay was the way to go, but now I have my doubts. I don't want this rocket to lawn dart due to a long ejection delay. I may just use the F44s in my Big Daddy, and the E30s in the Doorknob. This all seems a little counterintuitive, especially as I'm just beginning to learn the voodoo magic of motor/ejection delay selection. Any thoughts/reassurances from those with more experience with these motors is appreciated.
 

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Spitfire222

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On another note, I added another finishing touch to the rocket. I figured out how to use my wife's CriCut machine, so I cut out some CG and CP decals using vinyl. I simply cut out the black parts, then placed them on white vinyl circles of the same diameter so that they have a white background and can be placed on any color rocket. They are pretty small at 0.3" in diameter; any smaller and I think the CriCut would have trouble cutting them out properly. I cut out five of each, so I have some spares. One set will go on my Big Daddy, and then I'll have three pairs for future rockets. If I need more, it will only take a few minutes to make additional ones. I'll spray another quick coat of clear over the vinyl to help them stay adhered properly.

For anyone interested, CG and CP are located approximately 17" and 21" as measured from the tip of the nosecone, respectively.
 

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PhlAsh

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SEVRA has scrubbed tomorrow's launch at the Isle of Wight fairground. Keep an eye on sevra.org for the next launch. We're flying LP/MP currently and, if the waiver goes through, we'll be good for HP to 3,000'. We launch on the 1st & 3rd Sat of each month and hope to have Performance Hobbies in attendance on the former.
 

neil_w

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Thank you for the comments! I received the package I ordered with a pair of E30-7s and F44-8s, along with a pack of Estes 29mm to 24mm adapters. I test fit everything, and it all works fine. However, after looking at the performance specifications of the F44s, I'm concerned that I purchased the wrong delay. The specs say that the maximum recommended weight for the 8 second delay is 284 g, which is significantly lower than the 358 g my rocket actually weights (ready to launch, without motor). The minimum weight for the 4 second delay is much higher, at 453 g. I chose the delays based on the Open Rocket simulations I performed using these engines, and it seemed like the longer delay was the way to go, but now I have my doubts. I don't want this rocket to lawn dart due to a long ejection delay. I may just use the F44s in my Big Daddy, and the E30s in the Doorknob. This all seems a little counterintuitive, especially as I'm just beginning to learn the voodoo magic of motor/ejection delay selection. Any thoughts/reassurances from those with more experience with these motors is appreciated.
I would tend to agree that 8 seconds is too long for the F44. I'm always annoyed that they don't have anything between 4 and 8. Even 7 seconds for the E30 is very long. What does OR say?
 

Spitfire222

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SEVRA has scrubbed tomorrow's launch at the Isle of Wight fairground. Keep an eye on sevra.org for the next launch. We're flying LP/MP currently and, if the waiver goes through, we'll be good for HP to 3,000'. We launch on the 1st & 3rd Sat of each month and hope to have Performance Hobbies in attendance on the former.
Thanks for the info! I had found SEVRA in my nearby club searches, but I thought I had seen that the launches occurred someplace south of the border in NC, so I discounted that. But the Isle of Wight fairground is a much more reasonable drive from me, so I will definitely keep an eye out for the next launch. I've gone ahead and requested to join the Facebook group to stay informed.

I would tend to agree that 8 seconds is too long for the F44. I'm always annoyed that they don't have anything between 4 and 8. Even 7 seconds for the E30 is very long. What does OR say?
Here are the results for the E30s and F44s with their respective delays, originally posted in Post #135 above. The optimum delay appears to be right in the middle of the available delay options for the motors, so I looked at velocity at deployment next. For both of the motors, the longer delay options had lower velocities at deployment, so I went with those. So I'm not exactly sure what to think. The manufacturers weight recommendations in a way contradict the motor choice found through the OR simulations. How accurate do the OR simulations tend to be? (Keeping in mind that these simulations are using the actual, measured rocket weight from my completed model). Should I follow these results, or the manufacturer guidelines?

1596215334861.png
 

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neil_w

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Here are the results for the E30s and F44s with their respective delays, originally posted in Post #135 above. The optimum delay appears to be right in the middle of the available delay options for the motors, so I looked at velocity at deployment next. For both of the motors, the longer delay options had lower velocities at deployment, so I went with those. So I'm not exactly sure what to think. The manufacturers weight recommendations in a way contradict the motor choice found through the OR simulations. How accurate do the OR simulations tend to be? (Keeping in mind that these simulations are using the actual, measured rocket weight from my completed model). Should I follow these results, or the manufacturer guidelines?

View attachment 426483
Whoops sorry I didn't catch that on the earlier post. E30-7 looks OK; F44-8 is borderline but frankly looks OK to me if you're adequately protected against zippering. Sure would be nice to have a -6. :)
 
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Spitfire222

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Whoops sorry I didn't catch that on the earlier post. E30-7 looks OK; F44-8 is borderling but frankly looks OK to me if you're adequately protected against zippering. Sure would be nice to have a -6. :)
I think zippering should be ok with the rubber tubing I placed on the Kevlar shock cord, plus a decently long elastic shock cord on top of that. I probably have time to order some 4 second delay versions of the same motor before a good launch opportunity shows up. In the meantime, I'll keep running sims of other motor options!
 

PhlAsh

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Thanks for the info! I had found SEVRA in my nearby club searches, but I thought I had seen that the launches occurred someplace south of the border in NC, so I discounted that. But the Isle of Wight fairground is a much more reasonable drive from me, so I will definitely keep an eye out for the next launch. I've gone ahead and requested to join the Facebook group to stay informed.
The NC field is our primary, but it's a working field, so we can't launch until crops are up. The fairground field is new - we've only had one launch there so far. As I said, the waiver is in the works. Depending on how things go, this may become our primary.
 

Spitfire222

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The NC field is our primary, but it's a working field, so we can't launch until crops are up. The fairground field is new - we've only had one launch there so far. As I said, the waiver is in the works. Depending on how things go, this may become our primary.
Ok, good to know. The NC field would be quite a bit further from me than the Fairground field, so it's good to hear that the Fairgrounds are a promising option. Hope to see you at a launch soon!
 

artgsc

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Launch lug installation. I measured the half-way point between the fins, and made a mark. Using a length of aluminum angle stock, I drew a centerline for the lugs. Following the instructions, I marked up 0.5” and 10” from the bottom of the body. For a more secure bond, I used a file to carefully scrape away the primer and glassine on the body, and lightly sanded the lugs. To keep them aligned, I slid them onto a wooden dowel, applied some Titebond Quick & Thick, and placed the lugs on the body. Two small clamps on each end secured the lugs in place in a perfect line while the glue dried. I'll add fillets to the lugs a bit later.

*I recently noticed that the instructions have you mount the lugs 0.5” from one of the fins, instead of the midway point. Not sure if this matters, but I doubt it does. Oh well*
Your excellent build thread here prompted me to get going on an Estes Doorknob myself. I do see in the instructions where they have the launch lugs positioned at 1/2 in from the fin slot rather than at the midway point between the fins which I believe is 1 1/8 in. Never have run in to this before and have always positioned lugs at the midway point in all my other builds. Anyone know why Estes has instructed the lug positioning line to be drawn at 1/2 in from fin slot?
 

Spitfire222

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Your excellent build thread here prompted me to get going on an Estes Doorknob myself. I do see in the instructions where they have the launch lugs positioned at 1/2 in from the fin slot rather than at the midway point between the fins which I believe is 1 1/8 in. Never have run in to this before and have always positioned lugs at the midway point in all my other builds. Anyone know why Estes has instructed the lug positioning line to be drawn at 1/2 in from fin slot?
Maybe someone with more experience can provide a more concrete reason, but my best guess is that if you use the scale paint scheme, the lugs will end up on the edge of one of the orange sections, making the masking for this a bit trickier than if the lugs are offset. I came to this thought when I was painting my rocket, and I remembered the instructions, but it wasn't a problem to mask around them. Not sure if that's the actual reason, but it's the best I could come up with!
 

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artgsc

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Thanks for the info! Not going to try and paint to scale as any ambition in that direction usually outweighs my talent. So, at the midway point my lugs will go!
 
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