First high power build questions

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RobertC

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Hello, this is my first proper post in here, I’ve been reading in here for quite a while, and usually can find the answers I’m looking for just by browsing around and I probably could have found the answers I’m looking for by browsing a bit more, but I figured I’d just ask for some help instead of browsing for hours. I am starting my first high power build, it’s a 4” LOC Phoenix. I decided to open it up and start working on filling the tube spirals earlier today, and before I started filling, I noticed some imperfections in the tube. These imperfections are raised, like oblong bubbles about 2” long, and they are in between the tube spirals in the paper. I started with filling the tube spirals with wood filler, and sanded the filler smooth, and while I was at it I tried sanding down the “bubbles” a bit. That seemed to work to some extent, so I moved on to spraying the tube with filler primer. This seems to have brought back or accentuated these bubbles. I feel like I could just sand these bubbles out all the way and it will look fine, but not knowing what caused these bubbles has me a little bit concerned about the integrity of the tube at these points. Before I even started, I considered fiberglassing the tube just to add a little strength to ensure a successful L1 certification, and also thought that it might make it easier to smooth out the final finish. I’m a bit of a perfectionist and I’ve been building scale plastic models for many years. I would like the final result on my rockets to be as close to scale looking as possible, and with my smaller stuff I think I’ve been pretty successful so far. With all that being said, I have a few questions for those who have some more experience than me.

Has anyone experienced these “bubbles” before, and should I be concerned about the tube integrity in these places?

Would there be any benefit to ‘glassing the tube? and if so, what weight cloth should I use? I have .75oz and 3oz cloth that I've used for other projects just sitting here waiting for me to find a use for it. My main concern is the weight/strength trade off.

Also, if I ‘glass the tube, should I ‘glass the fins as well? With this, my main concern is adding extra weight to the tail of a design that’s already relatively tail heavy.
 
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RobertC

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I am sure LOC would replace the tube. They have top notch customer service.
Thanks for your quick reply! I thought about that, and I have read very good things about their customer service, but if I decided to ‘glass the tube, I’m not too sure the “bubbles” would really be hurting anything. That being said, I’m kind of wondering if ‘glassing the tube will add too much weight and/or affect the CG too much if I were to ‘glass the fins too though.
 

Wayco

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I have the "perfectionist" disease also, so I would take crossfires advice and contact LOC. They are great about replacing parts that aren't up to spec. Not that I think that bubbles would have structural implications, but if you're like me, when I know something isn't perfect, I will remember it forever.
Glassing a LOC tube is overkill for an L1 attempt, there are plenty of motors that won't stress your rocket in the H, I and possibly J category.
 

hotwings

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I contacted LOC, and they replied in minutes that they would send out a replacement tube ASAP. That is some very impressive customer service.
Great to here. Late to the party, but I think you'll find in general, all of the major manufacturers on HPR have superb customer service and stand by their products. All of them, after all, started these companies out of a passion for rocketry.

LOC was my first mid, and high powered rocket ages ago. Excellent kits, and a company that goes back to the early days of LDRS. Enjoy the rest of your build.
 

RobertC

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Great to here. Late to the party, but I think you'll find in general, all of the major manufacturers on HPR have superb customer service and stand by their products. All of them, after all, started these companies out of a passion for rocketry.

LOC was my first mid, and high powered rocket ages ago. Excellent kits, and a company that goes back to the early days of LDRS. Enjoy the rest of your build.
Customer Service does seem to be really impressive with HPR companies going by what I have read about various companies on the forum here, and by this one experience for me. I still find it kind of refreshing to find this kind of customer service anywhere in this day and age though. I’m really looking forward to the build, and hopefully many more! Thanks!
 

jd2cylman

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If you’re going to glass the tube, for best results, you need to peel off the outer white layer for maximum resin absorption.
 
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Rocks&Rockets

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+1 on LOC Customer service!
I bought their 3in IRIS last spring. The kit came with warped plywood fins. Plywood maybe not completely cured? So it got warped after laser cutting. Replaced promptly. Finally, after fire ban was lifted, got to fly it last month on the G80. Great flight! Great recovery! Awesome service!
 

Nytrunner

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Can you post pictures of the offending bubbles? I don't think I'm properly visualizing the issue. (maybe some outer layer delamination)
 

RobertC

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Can you post pictures of the offending bubbles? I don't think I'm properly visualizing the issue. (maybe some outer layer delamination)
I probably should have posted pictures in the beginning. I’ll try to do that tomorrow. The tube is down in my workshop at the moment. It doesn’t seem to really be delamination to me as I would expect it to look, they actually look like long teardrop shaped bubbles, raised maybe 1/16th of an inch or less at the high point.
 

dr wogz

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I've noticed, after a layer of primer & a good sanding, that larger / HPR tubes tend to not be a flat / smooth as we see in Estes tubes. That they have have lots of little raised areas & valleys. They are very slight, ands can really only be seen under a good light. But the sanding, a 2-tone finish, really shows them off..

As for "peeling off the outer layer": I never quite understood this. I get why you are doing it, but you are essentially removing a layer of the structure, and the outer binding layer that kinda holds it all together tightly. I would think a really aggressive & rough sanding should suffice (enough to raise a few fibers, scratch & roughen up the outer layer) Same with motor tubes.
 

jd2cylman

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As for "peeling off the outer layer": I never quite understood this. I get why you are doing it, but you are essentially removing a layer of the structure, and the outer binding layer that kinda holds it all together tightly. I would think a really aggressive & rough sanding should suffice (enough to raise a few fibers, scratch & roughen up the outer layer) Same with motor tubes.
The white layer is pretty thin and waxy(ish). Peeling it off doesn’t effect the structural integrity of the tube and allows for maximum epoxy absorption.
As always YMMV.
 

RobertC

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I've noticed, after a layer of primer & a good sanding, that larger / HPR tubes tend to not be a flat / smooth as we see in Estes tubes. That they have have lots of little raised areas & valleys. They are very slight, ands can really only be seen under a good light. But the sanding, a 2-tone finish, really shows them off..

As for "peeling off the outer layer": I never quite understood this. I get why you are doing it, but you are essentially removing a layer of the structure, and the outer binding layer that kinda holds it all together tightly. I would think a really aggressive & rough sanding should suffice (enough to raise a few fibers, scratch & roughen up the outer layer) Same with motor tubes.
I have also noticed plain paper tubes having more imperfections than the tubes with the shiny coating on them, especially after priming. The imperfections I experienced were there straight out of the box, and were more obvious than that. I will try to upload some pics when I get back to the shop later.
 

RobertC

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Here’s a couple of pictures, they don’t show what the “bubbles” looked like originally, because I worked at it with sandpaper for a while before I posted on here and then contacted LOC, but the pictures do show where the bubbles were, and how they were oriented. Wish I would have thought to take pictures before I started working on them, but these might at least explain a little bit.
1EEDF950-0499-430A-9887-EB018CEE2CBB.jpeg
593929C4-47DA-48EC-9930-1D2D7F06D563.jpeg
 

RobertC

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Almost impossible to get good pics of them.
Yes! That looks very similar to how mine were originally, only these were significantly larger, and ran almost perpendicular to the body tube spirals, the perpendicular orientation to the tube spirals struck me as being pretty odd. They seemed to be a good bit softer than the surrounding tube as well. It was really easy to sand them down flat, and then they popped back up a bit with primer. Now I have them sanded down as you see in the picture. I feel like I couldn’t even find them anymore if I were to spray another coat of primer (assuming they don’t pop back up again). If it wasn’t for their weird behavior, and their odd orientation (I would expect the defects to follow the tube spirals), I’d almost want to just keep on building with this BT instead of having LOC send out the new one and waiting. The softness there seemed to be on sanding them is what has me concerned more than anything else.
 

RocketRev

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David,

In my opinion, these are very good pics of LOC or at least LOC type tubing with pretty typical bubbles.

Structurally, these imperfections are pretty much meaningless. My L-1 was a 4" LOC parts scratch built. Rear ejection and all. Worked great and flew flawlessly for dozens of flights till I over-tested the limits of 7-ply aircraft grade 1/8" plywood without any fiberglass. It too had a few bubbles. I was told to ignore them or sand and prime till they no longer showed.

The 4" LOC tube remained in excellent condition even after the flight. Unfortunately, the fins fluttered so wildly that at least two of them quite literally delaminated. I picked up a bunch of thin layers of fin off of the ground. My mistake was trying a K-550 or maybe it was a K-1100 in an AT 54-1706 casing. All that to say that the 4" LOC tubing was fine even going Mach+. It was the fins that couldn't take the stress.

I know that lots of folks love fiberglass tubing. It is great, but it weighs a whole lot more and is harder to work with in general. Ye Old LOC tubing was and still is great stuff. I would definitely NOT bother fiber-glassing LOC tubing unless you're planning on using fiberglass fins instead of plywood. If somebody can find a picture of one, the old LOC kit called "K-Load" was a 5.38" diameter LOC kit with fiberglass fins and a 54mm mmt. A great kit. I flew mine for years and I never bothered to fiberglass the body tube.

Fiber-glassing LOC tubing is just way too much work for the results. Been there tried that and won't ever bother again. The larger the diameter airframe that you want, the more likely that you'll need fiberglass tubing to start with, if you want to get a bird that meets your visual perfection requirements.

Brad
 

David Schwantz

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Hi Brad, my tubing is for a stuffer tube inside an airframe. So it will only be seen after the fact. I was just posting what the bubbles look like. This is actually the first LOC tube that has had them for me. Jason is great and I know he would replace mine, but it was not needed. I love LOC stuff, use it for scratch builds all the time. But I really like fiberglass, and it is not so hard to work with. Dave.
 

RobertC

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When I wrote LOC about the tube, he mentioned that their supplier sent them a bad run of tube and that they had to sort out all the bad ones. Sounds like it was just one bad run from the tube manufacturer
 

RobertC

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I have a question about aerodynamics. I’m not too sure how these forums work, this is the first one I’ve really posted on. I started this thread a while back, before I had really gotten started on this project, and as this is still the same project, and I have more questions, I figured I should just post in here again. I hope this post pops up and is still seen by y’all. So, as I said in the original post, this is a 4” LOC AIM-54 Phoenix. and I have all the basic assembly done for the most part. I have noticed that none of the AIM-54 kits seem to come with fairings for the front fins like the fairings found on the actual missile. I grew up building scale models, and I am also a perfectionist that seems to be incapable of not making too much work for myself, so I decided to add custom made fairings that resemble those found on the real missile. It occurred to me a while back that they could adversely affect the aerodynamics, but I was already past the point of no return as they were already milled and epoxied on. I just got a coat of filler primer on yesterday, and am actually pretty pleased with how they came out, but now I’m even more curious about how they will affect the aerodynamics. So now that it’s far too late to do anything about it, I figure I’ll attach some pictures and ask those of you with a better understanding of aerodynamics and how aerodynamics scale down what you think. Will these fairings have a detrimental effect on the aerodynamics? Any answers will be greatly appreciated!
 

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Nytrunner

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Negligible affect on the aerodynamics. If anything the added weight affecting the CG will have more of an impact (and thats easy to take care of)

I did the same thing when I buolt a Phoenix, and it flew fine on a longburn J
 

RobertC

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Negligible affect on the aerodynamics. If anything the added weight affecting the CG will have more of an impact (and thats easy to take care of)

I did the same thing when I buolt a Phoenix, and it flew fine on a longburn J
Awesome! Thanks! I appreciate the quick reply!
 

Nytrunner

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You got it.

Whenever you post to a thread, it goes to the top of the list of its forum section.

Also, for those who've posted in a thread, the forum sends a notice the next time someone posts in that thread too, to help them follow the discussion. You can "unwatch" any thread yoive lost interest if you dont want those notices
 

RobertC

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You got it.

Whenever you post to a thread, it goes to the top of the list of its forum section.

Also, for those who've posted in a thread, the forum sends a notice the next time someone posts in that thread too, to help them follow the discussion. You can "unwatch" any thread yoive lost interest if you dont want those notices
That’s kind of what I guessed would happen, but didn’t know for sure. Thanks again!
 

mtnmanak

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Nice looking build and great job on the fairings.

Nytrunner is correct, they should not affect the "aerodynamics" of the rocket in a negative way. I played around with Rocksim to see how easy it would be to add fairings like that to a rocket sim. It was a bit tedious, but you can do it by adding some custom fin sets. It was the only way I could find to make the sim calculate the changes in CG and CP. It looks to me like those will move both the CG and CP rearwards slightly, so you should be fine.

A more interesting question is whether it will affect "performance" in the sense of how high and fast it will fly. It looks to me like they will add a bit of drag, so you may want to calculate that in when determining safe launch speeds and the altitude you are hoping for. Probably overkill, but maybe factor in a 5-10% margin to be safe.

On the other hand, they should assist you in getting a nice "low and slow" cert flight :)

Good luck!
 

RobertC

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Nice looking build and great job on the fairings.

Nytrunner is correct, they should not affect the "aerodynamics" of the rocket in a negative way. I played around with Rocksim to see how easy it would be to add fairings like that to a rocket sim. It was a bit tedious, but you can do it by adding some custom fin sets. It was the only way I could find to make the sim calculate the changes in CG and CP. It looks to me like those will move both the CG and CP rearwards slightly, so you should be fine.

A more interesting question is whether it will affect "performance" in the sense of how high and fast it will fly. It looks to me like they will add a bit of drag, so you may want to calculate that in when determining safe launch speeds and the altitude you are hoping for. Probably overkill, but maybe factor in a 5-10% margin to be safe.

On the other hand, they should assist you in getting a nice "low and slow" cert flight :)

Good luck!
Thank you very much for this response! I was planning on trying to Sim it before I fly it, and probably will still try, but I was already thinking about how the fairings will probably be tough to add in. I'm just assuming that based on my tiny bit of tinkering with autocad back in high school, I have never even tried a Sim and I suppose it's definitely time to start if I'm going to go any further into this hobby. I am only 35 years old, but as far as computer skills, you would think I was 90. I'm definitely not a techie. I really appreciate you taking a look into it because when I do try to Sim it and can't figure it out, that information in your anwer will be tremendously helpful. Thank you!
 

mtnmanak

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For HPR, you really do need to learn to use a sim or, better yet, a couple of the sims. OpenRocket is free (https://openrocket.info/), so no reason not to download it. Rocksim (https://www.apogeerockets.com/index...t_software_info&cPath=13_206&products_id=2636) is not free and is expensive, but the recent upgrades added a lot of functionality that have been missing for years, so, if you can afford it, it is a good tool. I use both.

I start every build by simming the rocket before you start and all the parts are easy to access and measure. Once you build the rocket, it is much more difficult to sim. And you should do that for every rocket - downloading other people's sim files or the generic ones from a vendor will only get you close. You need to do your sim files from scratch for each build to get accurate results.

As you move up in HPR, this becomes more vital. You really need to know things like the speed off the rail (for various lengths of rail too), thrust-to-weight ratios and the expected altitude. Nothing gets people at a launch perturbed like an unstable rocket off the rail or busting their ceiling!

For a down and dirty "sim", at least got to John Coker's Thrustcurve site and use his "Match a Rocket" tool (https://www.thrustcurve.org/motors/guide.html) to enter your rocket's basic info and get some ballpark info on expected flight performance. This is not a true sim and you should still use OpenRocket or Rocksim before you put a bird on the pad, but Thrustcurve is great for generating an initial motor list and ruling out a bunch of motors that won't work.

People on TRF are pretty good about answering OpenRocket questions, Apogee does a decent job of monitoring the forums for Rocksim questions and does provide support directly, and John monitors an open thread (https://www.rocketryforum.com/threads/thrustcurve-open-thread.164391/) for Thrustcurve questions.
 

RobertC

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For HPR, you really do need to learn to use a sim or, better yet, a couple of the sims. OpenRocket is free (https://openrocket.info/), so no reason not to download it. Rocksim (https://www.apogeerockets.com/index...t_software_info&cPath=13_206&products_id=2636) is not free and is expensive, but the recent upgrades added a lot of functionality that have been missing for years, so, if you can afford it, it is a good tool. I use both.

I start every build by simming the rocket before you start and all the parts are easy to access and measure. Once you build the rocket, it is much more difficult to sim. And you should do that for every rocket - downloading other people's sim files or the generic ones from a vendor will only get you close. You need to do your sim files from scratch for each build to get accurate results.

As you move up in HPR, this becomes more vital. You really need to know things like the speed off the rail (for various lengths of rail too), thrust-to-weight ratios and the expected altitude. Nothing gets people at a launch perturbed like an unstable rocket off the rail or busting their ceiling!

For a down and dirty "sim", at least got to John Coker's Thrustcurve site and use his "Match a Rocket" tool (https://www.thrustcurve.org/motors/guide.html) to enter your rocket's basic info and get some ballpark info on expected flight performance. This is not a true sim and you should still use OpenRocket or Rocksim before you put a bird on the pad, but Thrustcurve is great for generating an initial motor list and ruling out a bunch of motors that won't work.

People on TRF are pretty good about answering OpenRocket questions, Apogee does a decent job of monitoring the forums for Rocksim questions and does provide support directly, and John monitors an open thread (https://www.rocketryforum.com/threads/thrustcurve-open-thread.164391/) for Thrustcurve questions.
I have read quite a bit about hpr, so I knew that speed off the rail was important. Also, basically every high power thread I've read mentions a Sim, so I knew that I better figure it out. I've been contemplating whether I should buy rocksim or not. I think I'll give open rocket a shot first and see how I do with that. Thanks for your help!
 

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