Hair Brained idea for Level 1 cert?

[Scott_650]

Am I correct in that the Jolly Logic system is stand alone and does not require an AV bay/electronics and utilizes motor delay/ejection?

Yup - roll your chute in a bundle, wrap the rubber band lanyard around it, insert the locking pin, set your release altitude. It senses launch and apogee then the servo releases the locking pin at your AGL setting and the chute unfurls. As long as it gets out of the rocket it works. Not as elegant and precise as true avionics controlled dual deploy but great for keeping higher flying rockets from sailing away! Only real limitation is the body tube diameter - there are folks who claim reliable function in a BT60 sized tube but I don’t know how they get it to work. My lower limit is 1.8”.

 

[SDramstad]

I scratch built all of my cert rockets through level 3 including rolling my own fiberglass body tubes. Go for it!! In fact, I have never built a high power kit yet.

 

[R.E.Forrest]

Hey Rick, glad to see you on TRF and that you're thinking ahead to L1 and beyond. I agree that a 29 or 38mm MMT rocket is best. You'll likely build another rocket with a bigger motor soon thereafter...and another Take it slow and enjoy the process. Hope to see you at a launch soon.

Derek

Thanks Derek, good to see you around here as well. Still doing archery?

 

[R.E.Forrest]

I scratch built all of my cert rockets through level 3 including rolling my own fiberglass body tubes. Go for it!! In fact, I have never built a high power kit yet.

My kind of man. I am a confirmed roll yer own guy

 

[DeeRoc29]

Thanks Derek, good to see you around here as well. Still doing archery?

All my free time is currently consumed by rockets, but every once in a while I pull a yew or lemonwood stave off the wall and whittle a bit.

 

[bobbyg23]

Am I correct in that the Jolly Logic system is stand alone and does not require an AV bay/electronics and utilizes motor delay/ejection?

Correct. I used it on my L2 rocket with motor eject.

 

[R.E.Forrest]

All my free time is currently consumed by rockets, but every once in a while I pull a yew or lemonwood stave off the wall and whittle a bit.

I'm doing way more shooting than building lately. I have been focused on Asiatic/ thumb ring shooting for the last couple of years. Also doing a couple of scratch built muzzleloaders.

 

[DeeRoc29]

I'm doing way more shooting than building lately. I have been focused on Asiatic/ thumb ring shooting for the last couple of years. Also doing a couple of scratch built muzzleloaders.

Cool. I miss shooting, especially at Chamberlin. I'll get back to it someday.

So are you in the ball-mill-your-own camp, too?

 

[R.E.Forrest]

Cool. I miss shooting, especially at Chamberlin. I'll get back to it someday.

So are you in the ball-mill-your-own camp, too?

Milled some BP for chits and grins just to prove I could make a relatively decent and shootable powder. But good Swiss powder is far better than anything I'll ever make and I do take my shooting seriously

 

[JP Johnston]

I guess I am going to have to follow you now. The Estes Astron Spint is one of those rockets that fit into the visual type of appeal. I am going to have to eventually design and build a 54mm minimum diameter in the very near future. SolidWorks/Inventor, here I come!!!

Good Luck!!!

JP

 

[boatgeek]

I'm *very* confident of my crafting abilities. I am an experienced builder of wooden boats, traditional skin on frame kayaks, traditional and primitive archery tackle and have a pretty broad base of experience with epoxy and other adhesives.

I built scratch for L1. I used a kit for L2, though that was more a matter of what I had with me than the skills. The L2 was flown on a JLCR. One caution--definitely use a few shakedown flights on the JLCR to get used to flying it before your L1. It takes a little practice to get the chute to release properly. Lots of videos out there to help you with this.

I'm going to plant a seed here. I would absolutely love to see a rocket built with traditional skin on frame techniques. Building something a little simpler is probably better for your L1, but just let that marinate for a while...

 

[beeblebrox]

My two cents... For cert flights it is generally best to use a simple kit. Everything is there for you to build it. Remember it is a cert flight, you must have a total success including returning the rocket for examination by the person watching your flight to sign off on it. Remember the KISS rule... Keep It Simple Stupid... Use a big rocket with the smallest H-Motor with high thrust. AeroTech H180 Redline is a perfect one, for example. 4" rocket 6' tall with big fins is great for L1. 5.56" dia. 6-8' tall for L2. I have seen unstable scaleups of Sprints before. The CP is not as far aft as you may think, check CP/CG relation on openrocket or similar first. Dual deploy or other electronics is also a great idea, use motor ejection too if you want for drogue. The new Eggtimer Apogee is a great altimeter, only $15 + battery if you build it yourself. (This one is easy to build, only one SMD component and it's not super tiny.) A LOC 4" Black Brant X for example would be a great L1 kit.

 

[jqavins]

When I read the thread title I thought "Oh good god no. Don't go all harebrained on a cert attempt. Keep it simple and do the harebrained stuff later." Then I read:

I am in the opening stages of pursuing my Level 1 certification. One of the first steps is deciding what rocket to build and fly... I would like to draw up and build an upscaled 4", 38mm motor mount version suitable for H/I/J class motors. Very rough scaling puts it at approximately 54". It's a simple rocket design and would use a simple recovery system with motor based ejection.

And then my reaction was "What's he talking about? That's not harebrained at all!"

The nose cone I think will be the biggest obstacle to overcome. I don't know if there is a commercially available 4" cone of suitable shape. Thoughts are 3d printing, turning from wood on a lathe or perhaps glass over foam. Any thoughts on this would be welcome.

In your OP you stated that you build skin over frame kayaks. You could use a skin over frame nose cone.

Would you consider a 54 mount to be more versatile?

Indisputably so. Because:

You can always adapt down.

But that doesn't mean it's a better choice, just a more versatile one.

If you use the Aeropak retainer system, they make adapters that go right in. Other retainer systems may well also have their own dedicated adapters; Aeropack is the one I'm familiar with.

 

[R.E.Forrest]

I built scratch for L1. I used a kit for L2, though that was more a matter of what I had with me than the skills. The L2 was flown on a JLCR. One caution--definitely use a few shakedown flights on the JLCR to get used to flying it before your L1. It takes a little practice to get the chute to release properly. Lots of videos out there to help you with this.

I'm going to plant a seed here. I would absolutely love to see a rocket built with traditional skin on frame techniques. Building something a little simpler is probably better for your L1, but just let that marinate for a while...

Unlike modern glass or carbon kayaks, traditional skin on frame boats are intended to be flexible. It's a major component of their strength and one of the reasons they are a true delight to paddle when compared to synthetic boats. A flexible rocket fuselage might be a wee bit problematic, and building one to be stiff enough would be prohibitively costly as far as weight. There's a reason that rockets are made from the things they are made of, and I'm not going to try to reinvent the wheel

 

[kbocket]

I used a 4" Sprint for level II. IT worked great

 

[boatgeek]

Unlike modern glass or carbon kayaks, traditional skin on frame boats are intended to be flexible. It's a major component of their strength and one of the reasons they are a true delight to paddle when compared to synthetic boats. A flexible rocket fuselage might be a wee bit problematic, and building one to be stiff enough would be prohibitively costly as far as weight. There's a reason that rockets are made from the things they are made of, and I'm not going to try to reinvent the wheel

Fair, but I've also done my fair share of abominations against the normal order. It would be really interesting to see how much flex is too much. There's a few people out there building one-fin rockets that fly straight on average. In theory, one could do the same as long as the structural wiggles didn't get in phase with the path-traveled wiggles. Maybe someday I'll try it...

 

[R.E.Forrest]

I used a 4" Sprint for level II. IT worked great
View attachment 487286

Would you be willing to share dimensional details? Looks like a dandy! Also, what motor did you fly and how was the performance?

 

[R.E.Forrest]

My two cents... For cert flights it is generally best to use a simple kit. Everything is there for you to build it. Remember it is a cert flight, you must have a total success including returning the rocket for examination by the person watching your flight to sign off on it. Remember the KISS rule... Keep It Simple Stupid... Use a big rocket with the smallest H-Motor with high thrust. AeroTech H180 Redline is a perfect one, for example. 4" rocket 6' tall with big fins is great for L1. 5.56" dia. 6-8' tall for L2. I have seen unstable scaleups of Sprints before. The CP is not as far aft as you may think, check CP/CG relation on openrocket or similar first. Dual deploy or other electronics is also a great idea, use motor ejection too if you want for drogue. The new Eggtimer Apogee is a great altimeter, only $15 + battery if you build it yourself. (This one is easy to build, only one SMD component and it's not super tiny.) A LOC 4" Black Brant X for example would be a great L1 kit.

I am listening to your words, and understand what you are saying. But I do feel that I am following the KISS principle, only difference is that I'm making my own simple kit. As for stability, if I am not confident that it isn't right and safe, it won't get to the launch pad

 

[OKTurbo]

I would encourage you to scratch build a simple rocket for your level 1. Create a simple design, model the c.p. and find a good motor for it. Watch my video to see the scratch Mighty Mick I used for my level 1, plus I show a few ways to do close proximity recovery. One way I show is how to use the chute release.

 

[jqavins]

Fair, but I've also done my fair share of abominations against the normal order.

That's putting it mildly.

I used skin-on-frame for my elliptical rocket, because I couldn't think of another practical way. The frame was laser cut balsa ribs and ⅛" square balsa stringers (and they were a bear to work with; I should have used basswood) and the skin was paper, hardened after wrapping with generous application of thin CA (but I should have used heavier paper). In suggesting a skin on frame nose cone, I left out the word "traditional", mainly because I don't know what exactly that means as compared to a basswood frame and card stock or FG skin. I can tell you that what I built was not flexible at all.

"Basswood and card stock?! But this is HPR!" I hear you cry. Don't overthink or overbuild (unless you want to). There are plenty of paper tube, balsa or basswood fin, and wood glue rockets that fly just fine on H motors. An L2 rocket will probably require bigger, tougher stuff, but L1 stuff is MPR +1, not a sudden jump into a mysterious world where everything is different, and everything is big fiberglass structures. Your 38 mm motor mount and projected dimensions are fine, and yes I joined the chorus of advice that going with a 54 mm mount with the option to adapt down might be a good idea. Yet the opposite view is also valid; you can certify with nothing more than a heavy wall 1.6" body tube at maybe 30" tall, a 29 mm motor mount, a plastic nose cone, basswood fins and centering rings, and Tightbond. TTW fin attachment is probably a good idea, but really not necessary. Likewise stepping up from basswood to plywood: probably a good idea but not necessary (and balsa might very well do fine).

 

[beeblebrox]

I would encourage you to scratch build a simple rocket for your level 1. Create a simple design, model the c.p. and find a good motor for it. Watch my video to see the scratch Mighty Mick I used for my level 1, plus I show a few ways to do close proximity recovery. One way I show is how to use the chute release.

...Like the Bomarc!!!

 

[beeblebrox]

I am listening to your words, and understand what you are saying. But I do feel that I am following the KISS principle, only difference is that I'm making my own simple kit. As for stability, if I am not confident that it isn't right and safe, it won't get to the launch pad

Addendum...

I have seen many failed cert flights where the modeler tried a minimum diameter or barely bigger, then lost it. Now had to re-cert... Last week someone had something where they overlooked a few things, and it was recommended to fix the issues rather than going for broke.

Conclusion, make it work, then play hard!

Someone needs to figure out how to make Rocket Smileys!!!

 

[kbocket]

Sorry I don't always check in daily.

My Sprint was mostly built with PML components and a LOC nosecone. It was what was available at the time. The first attempt used 1/4 plywood fins and was fairly light ( just under 4 lbs if I remember correctly) The fins fluttered of a J350, it was not pretty. I rebuilt the rocket with 1/4 plywood fins that had 1/4 inch balsa of each side. After they were airfoiled I covered them with a layer of fiberglass. The boattail has a 1/4" plywood on either end, it was covered with light cardboard and a layer of fiberglass. It has held up pretty well with probably 20 flights of it using I and J motors. I loved flying it on I-154s lots of nice black smoke. (great photos) If I were to built today, I would think hard of using the fiberglass Goblin nose cone available from Performance Hobbies. I have attached the sim files I currently have on my computer. Now to keep from building a 6" version.

 

[R.E.Forrest]

Sorry I don't always check in daily.

My Sprint was mostly built with PML components and a LOC nosecone. It was what was available at the time. The first attempt used 1/4 plywood fins and was fairly light ( just under 4 lbs if I remember correctly) The fins fluttered of a J350, it was not pretty. I rebuilt the rocket with 1/4 plywood fins that had 1/4 inch balsa of each side. After they were airfoiled I covered them with a layer of fiberglass. The boattail has a 1/4" plywood on either end, it was covered with light cardboard and a layer of fiberglass. It has held up pretty well with probably 20 flights of it using I and J motors. I loved flying it on I-154s lots of nice black smoke. (great photos) If I were to built today, I would think hard of using the fiberglass Goblin nose cone available from Performance Hobbies. I have attached the sim files I currently have on my computer. Now to keep from building a 6" version.

Thanks for the files. What format are they? At the moment, all I have is my iPhone. I might be able to find a utility to open them.

The Goblin NC looks like a slightly pointer facsimile of the Sprint parabolic cone. If I can find an affordable and effective way to get one closer to scale, that's my preference. The Goblin is a bit short as well.

 

[tsmith1315]

What format are they? At the moment, all I have is my iPhone.

.ork files work in a free simulator called Open Rocket. Official site is here: https://openrocket.info/

Main forum thread here: https://www.rocketryforum.com/threa...d-mac-to-solve-all-your-java-problems.143540/

AFAIK, the simulator is for PC and Mac, plus an Android version for viewing. I don't think there's a version for iOS.


.rkt files are for Rocksim from Apogee: https://www.apogeerockets.com/index...t_software_info&cPath=13_206&products_id=2636
Again, I think PC and Mac are the only versions.

 

[jqavins]

If you have a PC or MAC, or access to one, I can't advise strongly enough getting OpenRocket or RockSim. They are rocket design and simulation software aimed at the hobby market (i.e. us). As 3D CAD goes, they're nothing. What they do is the basic rocket stability calculations, simulations with dynamic performance, and enough CAD-like stuff to be useful. Since OpenRocket is free, you really can't beat the price, as long as you have access to a platform to run it on.

 

[neil_w]

Upscale Sprite builders might be interested in this: https://richsrockets.wordpress.com/2018/02/07/building-the-scratch-mega-sprite-part-1/

 

[R.E.Forrest]

If you have a PC or MAC, or access to one, I can't advise strongly enough getting OpenRocket or RockSim. They are rocket design and simulation software aimed at the hobby market (i.e. us). As 3D CAD goes, they're nothing. What they do is the basic rocket stability calculations, simulations with dynamic performance, and enough CAD-like stuff to be useful. Since OpenRocket is free, you really can't beat the price, as long as you have access to a platform to run it on.

At the moment I have a Linux laptop. I thin Open Rocket will work withe that.

 

[jqavins]

Yes, I think you're right.

 

[OzHybrid]

At the moment I have a Linux laptop. I thin Open Rocket will work withe that.

If you go through the Linux releases for open rocket, you'll come across the appimage that already has all the dependencies included. That's the one to use. I've had failures with the other linux installs.(possibly me... )

Search OpenRocket-15.03.AppImage can be found here https://github.com/openrocket/openrocket/releases once downloaded change the file preferences to make it executable.

If I do a sudo apt install....... Looks like it installed but on trying to run get