Hair Brained idea for Level 1 cert?

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R.E.Forrest

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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 have been eyeball shopping various suggested kits, and while they are undoubtedly great suggestions, the creative part of my makeup just feels unsatisfied with assembling a collection of pre-fabricated parts. Soooo...

...this is my idea. As a teenager 40+ years ago, my very favorite model rocket was the Estes Astron Sprint. A very clean and sweet looking little design that would really 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.

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 am not seeking altitude records or ultimate performance but I do want a bit more of a challenge than most Level 1-type kits seem to offer. Am I being reasonable, or do I need my hand slapped? Thoughts both pro and con are welcome and expected 🙂
 

David Schwantz

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There is no reason why you cannot do this. But a J motor is L2. Good luck. Lets see picks of you r bows. I built 2 in high school, recurves, and still shoot them today.
 

R.E.Forrest

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There is no reason why you cannot do this. But a J motor is L2. Good luck. Lets see picks of you r bows. I built 2 in high school, recurves, and still shoot them today.
Yes, a J is Level 2. I have noticed some recommended L1 kits that can accommodate J and even K motors. Those, of course, will wait until I have the appropriate cert 😀

I need to dig up some bow pics, will try tonight or tomorrow.
 

Scott_650

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Nothing unusual about using a scratch build for certification attempt - let’s face it, a 3/4FNC rocket is a 3/4FNC rocket - regardless of whether it’s a commercial kit or a home built. The Sprint is a classic design and a 4” diameter upsize would be awesome, fabricating the nose and tail cones would be the biggest challenge but it looks like it’s within your skill set. As far as recovery goes I used a Jolly Logic Chute Release which worked great and took a lot of the uncertainty out of my attempt - depends on what your field is like, our club field is on a working farm so keeping rockets out of the corn and bean fields is critical. But if there’s enough open recovery area where your doing the cert flight motor recovery should be ok. The good thing about building a big, 4” rocket for your L1 would be how straightforward modding it for DD would be, plenty of room to add an avionics bay for an L2 flight. Good luck and post pix as you go!
 

Tim51

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As others have said, this isn't hare brained at all - looks like a very reasonable plan of action. But having asked a question you're now required to do a full build thread with lots of pictures. Them's the rulez 😉
Good luck - will be following with interest.
 

R.E.Forrest

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As others have said, this isn't hare brained at all - looks like a very reasonable plan of action. But having asked a question you're now required to do a full build thread with lots of pictures. Them's the rulez 😉
Good luck - will be following with interest.
It'll be a bit before the project starts.
 

R.E.Forrest

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Nothing unusual about using a scratch build for certification attempt - let’s face it, a 3/4FNC rocket is a 3/4FNC rocket - regardless of whether it’s a commercial kit or a home built. The Sprint is a classic design and a 4” diameter upsize would be awesome, fabricating the nose and tail cones would be the biggest challenge but it looks like it’s within your skill set. As far as recovery goes I used a Jolly Logic Chute Release which worked great and took a lot of the uncertainty out of my attempt - depends on what your field is like, our club field is on a working farm so keeping rockets out of the corn and bean fields is critical. But if there’s enough open recovery area where your doing the cert flight motor recovery should be ok. The good thing about building a big, 4” rocket for your L1 would be how straightforward modding it for DD would be, plenty of room to add an avionics bay for an L2 flight. Good luck and post pix as you go!

I have access to some large open areas in the Sacramento Valley within an hour's drive from me. If could build light enough to fly on G's I could do tune up flights before cert. I will likely attend one of the launches at BR this coming summer for cert flight. It's close enough to do weekend trips without a problem.

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. The boat tail should be simple enough. I need to study up on motor retention and a system that works well with the tail end.
 

jimzcatz

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This is a very well thought out plan, good luck with the project. Makes much more sense than the Idiot wanting to Cert L3 with a minimum diameter O3400!!! Yes, I said it.
 

tsmith1315

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I have been eyeball shopping various suggested kits, and while they are undoubtedly great suggestions, the creative part of my makeup just feels unsatisfied with assembling a collection of pre-fabricated parts.
It's great to hear of a L1 cert flight on a scratch built rocket! 4" dia is great, but you may regret limiting yourself to 38mm down the road.

If NC must be custom and I had a lathe, I'd be turning one. It could always be used for a plug, if that seemed better afterwards. Have you searched the forum? I'm sure there's been some Sprint upscales posted before.

Looking forward to some pics!
 

Rob Campbell

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Not hair brained at all. I certified on a scratch built Astron Constellation, complete with the fin tip pods. I have a sketch for a 4 inch Sprint as well. I planned to make the tail cone from poster board cardboard and reinforce it with fiberglass.
 

R.E.Forrest

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It's great to hear of a L1 cert flight on a scratch built rocket! 4" dia is great, but you may regret limiting yourself to 38mm down the road.

If NC must be custom and I had a lathe, I'd be turning one. It could always be used for a plug, if that seemed better afterwards. Have you searched the forum? I'm sure there's been some Sprint upscales posted before.

Looking forward to some pics!
Would you consider a 54 mount to be more versatile? Now that I think on it, 4" down to a bit over 2" would be more proportionally correct for scale.

I have looked through the forum, have not found anything specific regarding the NC for scaled up Sprints. I have access to a large high end lathe, what wood is typically used for a turned NC? I'm thinking basswood might be suitable. I like the idea of making a plug too, thanks!
 

R.E.Forrest

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This is a very well thought out plan, good luck with the project. Makes much more sense than the Idiot wanting to Cert L3 with a minimum diameter O3400!!! Yes, I said it.
It's like the guy who has never made a bow before wanting to begin by building a Turkish horn composite. Sorry kid, there's some chops ya gotsta earn before you try that, LOL
 

R.E.Forrest

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Not hair brained at all. I certified on a scratch built Astron Constellation, complete with the fin tip pods. I have a sketch for a 4 inch Sprint as well. I planned to make the tail cone from poster board cardboard and reinforce it with fiberglass.
I would be interested in your sketch if you might be willing to share.
 

tsmith1315

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Would you consider a 54 mount to be more versatile? Now that I think on it, 4" down to a bit over 2" would be more proportionally correct for scale.

I have looked through the forum, have not found anything specific regarding the NC for scaled up Sprints. I have access to a large high end lathe, what wood is typically used for a turned NC? I'm thinking basswood might be suitable. I like the idea of making a plug too, thanks!
You don't see many wooden nosecones for HPR. Probably a combination of cost, usable internal space, weight, etc. I have a basswood cone for my 1/3 scale Aerobee 300 eternal project, turned by BMC before they quit doing custom work. That's what Bill recommended, so I went with it. Lately, I've been thinking of using it as a plug to make one out of glass, but that decision is down the road a bit. You have the tools, it wouldn't hurt much to turn one and then think it over.

As for the MMT, going with a 54 will allow you several other choices in J-motors that are shorter than the AT 38/720-1380 motors. It's annoying to have a rocket that could fly on something larger, but your choice of MMT won't allow it. There are some interesting 54mm I's, too. You can always adapt down. But that is a personal decision. Some folks don't like to use adapters, and it may be more of a hassle with your choice of motor retention.

I should state that I'm speaking strictly in terms of Aerotech motors because of hardware I'm familiar with. Other vendors may have more options.
 

bobbyg23

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Would you consider a 54 mount to be more versatile? Now that I think on it, 4" down to a bit over 2" would be more proportionally correct for scale.

I have looked through the forum, have not found anything specific regarding the NC for scaled up Sprints. I have access to a large high end lathe, what wood is typically used for a turned NC? I'm thinking basswood might be suitable. I like the idea of making a plug too, thanks!
No need for a 54mm mount on this rocket. Use it for your L1 and have fun with it. This also gives you an excuse to build another one in the future with a larger mount for your L2. ;)
 

bobbyg23

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I got my L2 with a scratch built rocket. Very satisfying cutting all of your own parts and making it happen.
20200820_164851.jpg
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R.E.Forrest

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No need for a 54mm mount on this rocket. Use it for your L1 and have fun with it. This also gives you an excuse to build another one in the future with a larger mount for your L2. ;)
that's my thinking. I don't intend to use one rocket for both certs. Time comes, I'll build specifically for L2 cert. Who knows, maybe it will be Sprintzilla 😜
 

Kelly

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Sure, a scratchbuild like this for L1 is easily doable for someone with your skills.
I would read some HPR build threads here on TRF, and/or get a book on HPR, so you're more familiar with the specific techniques/materials/construction used for HPR - you don't want to overbuild, nor underbuild.
I'd also suggest obtaining, and learning to use, a simulator such as RocketSim (from Apogee), or OpenRocket (Freeware). Both are good, and will enable you to determine Cp, and get an estimate of Cg, build weight, rocket performance, best motors, etc. before starting.
As to your nosecone: Wood is generally a bit heavy, unless you can find a balsa block that size. 3D printed, with or without either a foam fill or glassing, is probably a better bet. Glass over turned foam will work fine too; there's some threads here about that.
Have fun!
 

R.E.Forrest

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Finding a quality balsa block that size could be a problem. I like the idea of glass over foam, that sounds like perhaps the simplest solution.
 

gerbs4me

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No need for a 54mm mount on this rocket. Use it for your L1 and have fun with it. This also gives you an excuse to build another one in the future with a larger mount for your L2. ;)
I like your mindset on that.
 

R.E.Forrest

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As far as recovery goes I used a Jolly Logic Chute Release which worked great and took a lot of the uncertainty out of my attempt
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?
 

DeeRoc29

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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
 
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