New to rocketry, jumping right in - have many questions

[Nytrunner]

Yeah, I found this place yesterday while looking for some local motors. Are they reputable? They look to carry some high-end stuff, but the website and the "by appointment" thing deterred me.

OffweGo and it's proprietor Gary are totally reliable. I'm guessing the "by appointment" is just because he doesn't man a full time storefront and wants a chance to make proper arrangements.

 

[PoweredBySoy]

Epoxy preferences will set off a small war, as everyone has their favorites.

You really weren't kidding. I've been reading about epoxy all morning and I feel like my head is about to explode.

 

[jlabrasca]

I would likewise guess that a D12-7 would be out of bounds. Better a D12-5 or maybe even a D12-3. That's just from eyeballing it, though, haven't downloaded the sim.

OpenRocket gives it a green check mark, although the Velocity at Deployment is listed as N/A <smile>.

FWIW, OR has the optimum delay on a D12 at 2.3s. It is a really heavy little rocket.

 

[samb]

You really weren't kidding. I've been reading about epoxy all morning and I feel like my head is about to explode.

I think you’ll find a great variety here but very little consensus. Many posts assume some level of prior knowledge on the given topic of discussion. IMHO, YMMV, and “This worked for me.” are common caveats in many postings (or should be IMO ). I came here about the same time that I began cultivating mentors at the local club which really helped my learning curve. That is why I suggest it to other newbies. Hope this helps.

 

[DAllen]

You really weren't kidding. I've been reading about epoxy all morning and I feel like my head is about to explode.

Oh yeah glue threads are pretty ridiculous here - or anywhere on the internet really. I just settled on RocketPoxy because the local vendors have it in stock usually and the fella that runs the company is our club prez. Almost all glues (when applied correctly) that are commonly used in rocketry are just fine to use and are stronger than the parts they are bonding. Sometimes its just a matter of preference.

 

[PoweredBySoy]

What are your thoughts on doing inner fin fillets?

In this video for building the Level 2, Tim doesn't do any interior fillets. This is also the procedure that the instructions call for with the Mini Squat I ordered.


I would expect this with a LPR like the Mini Squat, but thought maybe for a L2 rocket you'd want that reinforcment.

In the book I'm reading, Make: High-Power Rockets, the author has a different method, where you epoxy only the forward centering ring while sliding in the motor tube. The rear centering ring is inserted only for positioning. Then after the forward epoxy dries you pull out the rear centering ring (via string) so you have access to the fins.

Then once all the fillets are done you epoxy in the rear centering ring.

Thoughts? Is Tim's method 'good enough'? Do these internal fillets add a lot of unnecessary weight?

 

[OverTheTop]

IMHO probably overkill. The distance between the tubes resists the force well with the fin tab, reducing stress on the fillets. In this situation I think just small fillets is good, just around the corner of the wood.

 

[Rex R]

the fin tabs will transfer thrust loads to the airframe and reduce them on the centering rings. when possible I like to put filets on the tab/motor tube joint and t least one set on the fin/airframe joint.
Rex

 

[boatgeek]

I use the approach in the Make book for my HPR rockets. It makes a bomb-proof fin can, though a little heavier. For LPR/MPR, external fillets only is almost certainly OK.

 

[Andrew_ASC]

I ran external fillets on a Wildman Rb-05A sport for L-1. Fiberglass rocket with rocketpoxy and cotronics. Did dip the fin tabs into the epoxy though but all is well after five HPR flights.

I think you should go to a local launch, find a mentor, and jump head over heels into L-1 since that’s what interest you. Of course I started with minimum diameter multistage L-1 in a college competition which well was one heck of a journey. The learning curve is expensive if you don’t take the advice of others.

 

[tomsteve]

What are your thoughts on doing inner fin fillets?

and you thought epoxy brings up controversy.
i do inner fillets- at the mmt and at the bt. then i dont have to go too crazy with external fillets. also fill fin can with expanding foam. on larger dia rockets i'll drill some holes in the fins in the area between mmt and bt so the foam flows through and locks them in. yup- its overkill, but i havent ever had a fin pop. a fin break-yes, but outside of the bt.
it adds weight but im ok with that.

 

[gldknght]

I use internal fillets on all my hpr builds. West systems epoxy and carbon fiber. If done properly, these internal fillets won't add a lot of extra weight. I'm working on (meaning I looked at the project twice this year) my level three rocket, and with 6 fins and 24 internal fillets, the epoxy only added a few ounces, which is more than offset by the "brains" in the av-bay. If that extra weight means my rocket only goes to 9500 feet instead of 10000 feet, well that's fewer steps to take to recover the rocket.

But. Having said all that, when ever you add weight to the tail end of a rocket, make sure, and I mean MAKE SURE!!!!! you have a proper center of balance/center of pressure relationship on your rocket, whether its Lpr, Mpr or Hpr.

 

[PoweredBySoy]

edit: Neil got it!

 

[neil_w]

I normally stick my motors out 1/4". Kits might sometimes do a bit more.

The D is (obviously) shorter than the E. Estes provides orange spacer tubes that you put in above the D to fill the remaining space. You could do the same with a piece cut from a spent motor casing... after you burn a motor that is.

There are many ways to retain motors other than the hook and the motor block. For BP I like the hook and the block. You'll just need the spacer for the D motors.

 

[PoweredBySoy]

I normally stick my motors out 1/4". Kits might sometimes do a bit more.

The D is (obviously) shorter than the E. Estes provides orange spacer tubes that you put in above the D to fill the remaining space. You could do the same with a piece cut from a spent motor casing... after you burn a motor that is.

There are many ways to retain motors other than the hook and the motor block. For BP I like the hook and the block. You'll just need the spacer for the D motors.

OOOOOOOOOOH, that's what that small piece of tube is for. I was wondering. Right, so when I position the thrust ring where it should go, and then slide this tube spacer in first, the D motor lines up with the hook perfectly. Thanks!!

 

[JohnCoker]

You may like some of on intro to HPR articles:
jcrocket.com/kitbuilding.shtml
jcrocket.com/certify-level-1.shtml

 

[PoweredBySoy]

Day 1 done.

 

[BDB]

Looks good!

 

[OverTheTop]

Great idea for the fin guide! I could say it is "out of the box" thinking but that would be too punny

 

[PoweredBySoy]

How easily should the nose cone separate from the body tube??

This nose cone is plastic, and while pulling it from the tube there are definitely a couple spots where it 'sticks' a bit. I would not say it separates from the tube smoothly. I'm just not sure how strong the ejection charge is going to be, or if I should be sanding the cone plug down a bit.

 

[smugglervt]

It should not detach while holding the rocket by the nose cone but should come loose with an easy shake.

 

[jlabrasca]

It should not detach while holding the rocket by the nose cone but should come loose with an easy shake.

To calibrate "easy" for this rocket -- think in terms of the arm strength of an 11 y.o. girl.



edited: to make it slightly less creepy

 

[PoweredBySoy]

Thanks, gentlemen! I should have guessed there would be an Apogee video for it.

I'll definitely need to sand it a bit.

 

[PoweredBySoy]

My first fillets ever. Layed them down with a small craft stick, then after 30 minutes went over them with a wet gloved pinky finger. Down at eye level you can see some minor 'hills' and 'valleys', but overall I think they look a'ight. I'll lay the next pair tomorrow morning.

 

[neil_w]

Those look pretty good for first (or even not first) fillets. In the future you might consider masking them, to get nice clean edges. Totally optional though.

I am curious about the weight of those fillets on such a small rocket. Might be interesting to weigh before and after one set. Eventually you'll know the total weight and CG of the rocket, so it's not actually necessary to know it now.

 

[beeblebrox]

I recently got the bug to try rocketry. I've spent the past week reading articles and watching videos, and I think I have a general gameplan to get started. Although there is still a fair amount that confuses me.

LPR doesn't interest me. I want to go loud and fast, and for multiple reasons I've decided to go with the Madcow ARCAS for my first rocket. Mostly, I think it's a beautiful looking rocket and I love the history behind it.

Right now the plan is to build the rocket, do a few flights on "low power" G motors, and then go for my L1 cert on an H. For this I'm leaning towards the Cesaroni brand, since for whatever reason their motor systems seem to make the most sense to me. What I'd like to do is to try and 'future proof' the rocket by building it with a 38mm 3-grain case, and then use spacers for the time being. Initial flights will be on 1-grain, cert and following flights on 2-grain, and then if I'm feeling saucy I can up to 3-grain motors.
I'm still trying to learn the specifics of motors and what I'd need, but that's the general plan at least.

Do I need an altimiter? I assume I'll be using the ejection charge from the motor for chute deployment - but I'd still love to have some telemetry numbers from the flight that I could load to a computer. Would an altimiter give that to me?

I'm also very intrigued with getting on-board video of flights - although I'm not finding much info about it. Would that even be possible with the ARCAS? I'm not sure if the ARCAS has an e-bay or not.

I know it says the ARCAS is dual-deploy capable, but I doubt I'd be wanting to take that on for my first build.

I've started reaching out to my local NAR group, and plan on attending their next launch party in a couple weeks.


Anyways, let me know if you have an comments or thoughts... or if I'm completely off base.
Thanks!

I would recommend going with 29mm motors to start with hpr capable paper tube kit. I recommend AeroTech, kits, LOC Presision Kits and AeroTech disposable motors for your first flights. Try an AeroTech Sumo or G-Force 4" Diameter so wont go to high with G-Motors to do test flights with altimeters etc. but capable of handleing larger motors, definatelt perfect for a level 1 flight, go with Tripoli, https://www.tripolimn.org/ too they may also have launches you can get to.Remember the KISS rule: keep it simple stupid, Mr. Murphy will bite you with his law if you let him...lol

 

[PoweredBySoy]

Interesting. After a couple of hours most of those 'hills' and 'valleys' corrected themselves. It's not perfect, but it looks a little smoother.

Those look pretty good for first (or even not first) fillets. In the future you might consider masking them, to get nice clean edges. Totally optional though.

I am curious about the weight of those fillets on such a small rocket. Might be interesting to weigh before and after one set. Eventually you'll know the total weight and CG of the rocket, so it's not actually necessary to know it now.

Honestly, I was going to tape but I forget. Oh well.

I don't think there's as much epoxy material there as the picture makes it look. The actual fillets look pretty small to me. I plan on sanding on Friday, so maybe I can produce some better pics then.

I ordered a table scale! I'm too curious not to know the weight of this thing.

 

[PoweredBySoy]

I would recommend going with 29mm motors to start with hpr capable paper tube kit. I recommend AeroTech, kits, LOC Presision Kits and AeroTech disposable motors for your first flights. Try an AeroTech Sumo or G-Force 4" Diameter so wont go to high with G-Motors to do test flights with altimeters etc. but capable of handleing larger motors, definatelt perfect for a level 1 flight, go with Tripoli, https://www.tripolimn.org/ too they may also have launches you can get to.Remember the KISS rule: keep it simple stupid, Mr. Murphy will bite you with his law if you let him...lol

Yeah, I'm hearing it's best to get a fat rocket that won't go so high on G's and H's for L1 cert. So I'll probably get something in that realm. But also, I have to like the rocket too - and be excited to build it. I'm eager to get to something bigger though. I feel like working on such a small rocket brings about it's own unique set of challenges for me. I generally have 'fat fingers'.

There is an active HPR Tripoli club near me as well. Although I think they've just done their last launch for the season.

 

[neil_w]

Yeah, I'm hearing it's best to get a fat rocket that won't go so high on G's and H's for L1 cert. So I'll probably get something in that realm. But also, I have to like the rocket too - and be excited to build it.

Check out Fusion Rockets if you haven't already done so.

 

[snrkl]

Yeah, I'm hearing it's best to get a fat rocket that won't go so high on G's and H's for L1 cert. So I'll probably get something in that realm. But also, I have to like the rocket too - and be excited to build it. I'm eager to get to something bigger though. I feel like working on such a small rocket brings about it's own unique set of challenges for me. I generally have 'fat fingers'.

There is an active HPR Tripoli club near me as well. Although I think they've just done their last launch for the season.

I remember wondering what all the fuss was about - how much difference could there be between building an F motor rocket and an H motor one?! But, I read lots here and soaked it in and followed advice not to rush it.

So glad I did. I’ve developed what I think are some great construction skills, and folks here certainly like the work I do... it’s been a year from start to L1 and hopefully I’ll be L2ing next weekend (final shake down flight of my L2 on a I236 resulted in a damaged fin, thanks to a parked car on the public launch day, so I had to scratch my L2 attempt...)

Now that I am more aware of the leaps in force applied with each motor jump, I’m MUCH happier to take it slow...