Greetings! New member buying LOC IV with lots of questions!

[Curtis Enlow]

Thanks, Boatgeek,

From Seattle, Tri-Cities is just as much driving time as Mansfield. I'm not sure how that balances for Arlington since you're a bit closer to Highway 2.

Google says 4 hours to Richland via 405/90 (add an hour for WA-2) so that's not too bad, only 15 mins longer than Mansfield. It looks like an awesome place to fly (if the wind doesn't get too crazy) and even if it does it looks like you can see for miles. Do they allow camping at fly-ins?

I'm thinking hard about 29mm reloadables w/adapter. Seems like the way to go in mid-power configuration, and 38/400 case with RAS for L1/L2.

Another nice thing about 60 Acres is that when it's not soccer season (November-late May/early June), you can come down and fly any time with your own launch gear. I'm there most every Sunday morning with the TARC team I'm mentoring. Also, if you're flying F motors or smaller, the south side of the field is a lot less swampy than the north side in the rainy season.

I was wondering about flying 'rogue' at 60 Acres... I don't currently have launch gear, but am good at electronics so a controller and pad should be an easy build. I assume that if you are a Tripoli or NAR member insurance covers you at a site that allows rockets, like 60 Acres?

Thanks so much for the information and advice!

C

 

[boatgeek]

Thanks, Boatgeek,



Google says 4 hours to Richland via 405/90 (add an hour for WA-2) so that's not too bad, only 15 mins longer than Mansfield. It looks like an awesome place to fly (if the wind doesn't get too crazy) and even if it does it looks like you can see for miles. Do they allow camping at fly-ins?

I'm thinking hard about 29mm reloadables w/adapter. Seems like the way to go in mid-power configuration, and 38/400 case with RAS for L1/L2.


I was wondering about flying 'rogue' at 60 Acres... I don't currently have launch gear, but am good at electronics so a controller and pad should be an easy build. I assume that if you are a Tripoli or NAR member insurance covers you at a site that allows rockets, like 60 Acres?

Thanks so much for the information and advice!

C

WAC allows camping, and I believe TCR does as well. You could check with Rich Harshberger though. At 60 Acres, look at the online calendar to see if there's anyone else you'd really be interfering with and go launch. As long as you clean up your trash, nobody cares too much. I like to go talk to people launching or flying RC in the near area and let them know I'll be launching rockets, just as a matter of courtesy.

 

[rharshberger]

TCR does allow dry camping and we usually have the porta potty serviced just before launches.

 

[Ted Cochran]

FWIW, LOC-IV was my level 1 rocket. I built it mostly stock (anti-zipper design was the only mod) using yellow glue, no epoxy, and have flown it a zillion times, all over the country, mostly on H180s. I second the suggestions above to keep it simple, but don’t let that deter you from embarking on whatever you want to learn more about.

 

[scott johnson]

I just completed a LOC-IV for my level I coming up in April. That was a lot of filling spirals and sanding! I'm eyeballing a LOC VII now.

 

[Curtis Enlow]

I just completed a LOC-IV for my level I coming up in April. That was a lot of filling spirals and sanding! I'm eyeballing a LOC VII now.

Ugh, I'm disappointed to hear there are open spirals in the tubes. I was hoping they were tubes that didn't have them. Were they bad enough you had to use a filler, of did a couple coats of high-build primer do the trick?

Any other issues, tips or tricks?

C

 

[Nytrunner]

Unfortunately spirals will be present on the cardboard and bluetube airframes all the way to the big sizes (see 5.5" tube below....).
For smooth you'll need G12, Quantum tube, or manufactured carbon fiber tubes

For LOC tubes, Filler/sandable primer from the auto section will help the spirals, but I prefer to do a line of bondo spot putty to try and even things out.

 

[Curtis Enlow]

For LOC tubes, Filler/sandable primer from the auto section will help the spirals, but I prefer to do a line of bondo spot putty to try and even things out.

I've been working with micro-balloons/epoxy as lightweight filler on my sailboat and am really impressed with it. It's light like styrofoam but hard like very hard plaster and easily sandable. Sounds like I'll be using it for more than just fillets

 

[tOD]

Hi Curtis,
I'm relatively new to Rocketry and the Forum myself and have gone from B motor Estes kits to planning for an L2 soon.
I've been using Aerotech motors and have the RAS for both sizes. My suggestion would be to check out a couple of vendors and consider a starter kit in either (or both) sizes. The 29 kit gets you the 180 and 360 cases, an aft closure, and the RAS for a "bundle" price. The 38 kit gets you the 380 and 720 cases and the closures and spacers. This would cover motors from some 29mm G's up to 38mm J's. with reduced cost for hardware. I've found that assembling a motor with the RAS to be a little more difficult than assembling a motor with a propellant kit that is an exact fit.
I've abandoned the idea of a "does-all" rocket, they're too much fun for just one. Ever see a golfer try to play the course with only one club in his bag?

 

[Curtis Enlow]

Hey Tod, thanks for the response!

Well, tomorrow afternoon I should have an LOC I sitting on my porch, so right now I need to do with what I've got I still think the IV will be a good top-end mid and entry L1 ship if I build it right, but I would be looking REALLY hard at a new kit for anything bigger than 'H's because...I want to fly video. Maybe even a VR camera. That's still in Dreamland right now, though.

Yeah, I am still letting the propulsion system stew in its own juices in the back of my head. I am pretty much sold on the advantages of using 29mm for mid-power stuff, at least. I'm concerned about weight (as we all should, right?) but the Aeropack 29-38mm adapter - while pricey - is only like 3.6g, which is a fraction of the bulkier, traditional MMT adapters. At the local field i am happy to keep the flights under one thousand feet (especially with apogee main release) and there are a couple 29mm 'G's that will do that just fine, and since the IV has a 38mm MMT I will need a retainer regardless, but TWO RAS...man...that gets pricey, too. So many decisions...

But I am looking at the reloadable Aerotech's for small field mid-power. Loadables, too, but they are bit more, BUT no RAS and the weight that entails along with the adapter. It looks like reloads can be had for about $17 ea. with no HAZ (If I've got that right...?). BUT Then you can get a 38mm G61W-14A for $16, but there's HAZ. Soooo, I guess it depends on whether I can get in on any bulk buys with other club folks and stock up.

Looks like a 7 Iron for now

 

[boatgeek]

I've been working with micro-balloons/epoxy as lightweight filler on my sailboat and am really impressed with it. It's light like styrofoam but hard like very hard plaster and easily sandable. Sounds like I'll be using it for more than just fillets

The only difficulty with epoxy/microballoons is that the cardboard is still softer than the filler, so you have to be careful you are only sanding the filler. For fillets, I like to do an undercoat of epoxy with something more structural (usually wood flour), which I then rough sand and coat with a thin layer of microballoons for a smooth surface. It's also much easier to fill spirals before you put the fins on.

 

[Curtis Enlow]

The only difficulty with epoxy/microballoons is that the cardboard is still softer than the filler, so you have to be careful you are only sanding the filler. For fillets, I like to do an undercoat of epoxy with something more structural (usually wood flour), which I then rough sand and coat with a thin layer of microballoons for a smooth surface. It's also much easier to fill spirals before you put the fins on.

Agreed. I was thinking of a multi-step process as well - a thin brushed coat to penetrate the fibers, then a (very) small structural fillet with chopped glass and an overcoat of lightweight filler, but at any rate I will endeavor to get the fillets as close as possible to the final shape to reduce the material hardness difference issue as much as possible. I think I am going to vacuum-bag a fine weave on the IV fins; they are 'landing gear' and seem to be the weak link in the IV, from all that I have read. I found an art supply dealer that carries triangular plastic rod in the width of the IV's fin material, so I think I will put that on the LE & TE of the fins - looks nice and toughens them up just a notch more.

I'm always amazed at build videos where people dam the ends of the fin stock and pour in a thick fillet...wow. Someone (better at math than I) should make a chart of how much Newtons of thrust is wasted boosting each gram of unneeded material up...

Do you find that wood flour sands easier than microballoons? I think the microballoons are lighter by a bit, but if the wood flour is easier to sand it might be a sensible trade-off.

Thanks!

 

[boatgeek]

...

I'm always amazed at build videos where people dam the ends of the fin stock and pour in a thick fillet...wow. Someone (better at math than I) should make a chart of how much Newtons of thrust is wasted boosting each gram of unneeded material up...

Do you find that wood flour sands easier than microballoons? I think the microballoons are lighter by a bit, but if the wood flour is easier to sand it might be a sensible trade-off.

Thanks!

On the other hand, we probably waste a fair number of N-s on suboptimal fin airfoiling and shapes. I'm not in it for altitude records, so I tend to build them stout while trying not to be totally unreasonable. Of course, everyone has different goals and what they think is fun.

Wood flour/microfibers are definitely harder to sand than than microballons, but they're also stronger. I just do a rough cleanup on the wood flour fillets with a coarse rat-tail file and then 110-grit sandpaper, then do all of the finish work with a thin coat of microballons and finer sandpaper. I'm also headed for a 3-6 foot paint job, not a beautifully polished masterpiece like other people here do. As above, YMMV and you may find other techniques you like.

 

[Curtis Enlow]

On the other hand, we probably waste a fair number of N-s on suboptimal fin airfoiling and shapes. I'm not in it for altitude records, so I tend to build them stout while trying not to be totally unreasonable. Of course, everyone has different goals and what they think is fun.

Ha! Yes, exactly. I know that even a simple airfoil shape is more effective at countering asymmetric relative wind so I have been spending a lot of time recently (probably more than any normal, healthy person should ) considering how to accurately machine (inaccurate hand-sanding/forming is possibly less effective than a slab-sided airfoil surface as far as enhanced stability goes) a simple airfoil shape, if even just consisting of tapers fore & aft. There are a lot of options for larger fins, but at the smaller rocket level that gets mind-numbingly difficult and well-aligned slab-side fins with a reasonably accurate LE/TE shape of some sort are probably all that one really needs, though, ironically, the slower rockets need them the most.

But it is fun geeking out on this stuff, and it gives my brain something to do

 

[Nytrunner]

I lay balsa fins on a wedge shaped vinyl applicator to keep a constant angle while sanding the trailing edge.
Plywood fins get the taper's "shoulder line" taped and a belt sander treatment.

Leading edge roundover has been done by hand, but I'm getting a couple sizes of 3d printed sandpaper holders to perfect the curve on balsa fins (North coast is also working on a product like this for sale)
Plywood fins get the router roundover bit treatment.

With a steady hand and eye, hand foiling isn't that bad. just be sure to alternate sides with the same number of strokes.

 

[Curtis Enlow]

I lay balsa fins on a wedge shaped vinyl applicator to keep a constant angle while sanding the trailing edge.

John Coker has a good YT video on tapering and vac-bagging tapered airfoils.

I remember making a leading edge sanding tool for an R/C Cub I built once. It was two rectangular die-cut pieces with the LE shape cut into them and supported with some ply planks. If I remember correctly you cut a piece of card stock and CA'ed it to the cut outs to form backing for the sandpaper and it had a guide that slid along the bottom of the wing. It worked very well, and was simple to make. I imagine something like that could be easily made to create repeatable, accurate shapes & tapers on fins. Hmmm...

 

[Curtis Enlow]

I'm also headed for a 3-6 foot paint job, not a beautifully polished masterpiece like other people here do

Just to share some information for those who are working on high-altitude screamers, I know that on aircraft there is an 'aerodynamically critical' area (the first third of a wings camber, for example) where absolute smoothness is necessary at high sub-Mach and supersonic speeds on aerodynamic bodies. The parasite drag of just a couple thousandths of an inch exponentially increases to a surprising amount as you near the speed of sound, so much so that even surface roughness can affect it and it can prevent an adequately powered aircraft from going supersonic.

Myself, I like big, slow and low, but I still like shiny. (That probably explains the tiny bit of tin foil and shiny objects I have squirreled away in a special hiding place...

 

[grouch]

Boat building techniques may not be your best interest if weight is a concern. Filling spirals is not hard providing you use the correct tools for the job. Epoxy with an additive is not that tool. Sanding is harder than it needs to be. Get the Elmers wood filler at the local box store. I like the pink color that dries tan. Mix a little water into it to bring it to a slightly thinner than toothpaste thickness. Use a gloved fined to smear it into the groves about 12" at a time and smooth it out with an old credit card. If done correctly, there is little sanding required. It will shrink a bit and some go as far as repeating the step but I just use high fill primer instead.

 

[Curtis Enlow]

Epoxy with an additive is not that tool. Sanding is harder than it needs to be.

I was actually just thinking about this - a suitable filler but in a matrix lighter than epoxy. I knew that Elmers with balsa sanding dust has been used in Free Flight and R/C airplanes forever. I will look into the filler, Jarrett, thanks!

 

[Steve Shannon]

I was actually just thinking about this - a suitable filler but in a matrix lighter than epoxy. I knew that Elmers with balsa sanding dust has been used in Free Flight and R/C airplanes forever. I will look into the filler, Jarrett, thanks!

Microballoons added to epoxy makes for a very lightweight fairing compound that is easily sanded. Either phenolic or Glass microballoons work. Use a respirator when sanding.
SuperFil is a very good commercial lightweight filler used for composite aircraft construction.
If I’m glassing paper or phenolic tubes I don’t fill the spiral groove at all.

 

[Curtis Enlow]

For LOC tubes, Filler/sandable primer from the auto section will help the spirals, but I prefer to do a line of bondo spot putty to try and even things out.

LOC has evidently stepped up their body tube game: The IV arrived today and the spirals are so tight I can't even catch a fingernail on them. Very nice. The 4" extension tube from Discount Rocketry is equally tight & smooth.

Also, I'm glad to see that they have gotten rid of the silly elastic shock cord as it came with a nice length of 7/16" nylon (I believe) flat belt. The fins are a little...flexible. I have pretty much made up my mind to add tapered pieces and vacuum bag them with a light glass cloth & epoxy, as I want a little better strength (and added performance if/when I stretch it into a HP IV-B). It also came with a nice 36" chute, though I will probably go with a step up in size for the stretched version.

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Okay, what's the best way to include photos on this forum...?

 

[Curtis Enlow]

Now, a question is: Should I do a bulkhead mod on the nosecone, or is the blown-in ring strong enough? (Do they ever actually fail in normal ops?).

 

[rharshberger]

Now, a question is: Should I do a bulkhead mod on the nosecone, or is the blown-in ring strong enough? (Do they ever actually fail in normal ops?).

The nosecone bulkhead mod really isnt a must do (but its a do it if you want too), instead drill two .5" holes one on opposite sides of the plastic nosecone base and thread your recovery harness through and tie it to itself creating a loop. Yes the factory loops fail eventually.

 

[bjphoenix]

I built a rocket similar size of the LOC IV many years ago for level 1. I designed my own fin shape and bought the parts I needed. I built it with a 38mm mount and used normal epoxy fin fillets, nothing fancy like carbon fiber or filling the spirals. I bought an AT 38x240 and an extra 480 sleeve so I could launch with full H or full I motors. The rocket flies well with an I, but seems a bit low with an H. I wouldn't try a rocket of this size with a G. I have another 4" rocket I built with spare parts that is only about half as long as the LOC IV and being much lighter it flies well with a 29mm G64. Using H and I motors I just use motor ejection. If a person wanted to eventually use J motors then dual deploy would be essential, maybe even carbon fiber on the fins. You can certainly build smaller rockets for level 1 such as 54mm or 2.6" diameter, but those will go much higher with an H or I and would need a larger field for recovery. I wanted to be sure to get my L1 rocket back.

 

[scott johnson]

I used the Elmer's "Carpenter's Wood Filler" thinned slightly to fill spirals......the pink stuff. I filled and sanded then applied two coats of sandable primer. Had to go back and fill in a few spots as even though the spirals are tight, they showed through the primer. I spent about 6 hours filling sanding, priming, sanding, filling, sanding, priming etc. etc. and ended up with a fairly nice finish. Looks real good from 3 feet away. I really didn't want to go overboard with a C/L stunt plane type finish, but I wanted it to look good, too! If I build a second one I'll put more effort into it like airfoiled fins and a "Concours d'elegance" finish.

 

[Curtis Enlow]

If I build a second one I'll put more effort into it like airfoiled fins and a "Concours d'elegance" finish.

I am going to add a little form to the IV's fins (simple tapered airfoil) and cold bag them per John Coker's excellent video. Both for efficiency & strength. Evidently, an airfoil vs. slab-side fin does move the CP aft and improves the fins effectiveness against asymmetric relative wind, but also adds a slight amount of drag - sounds like a reasonable trade-off.

 

[Nytrunner]

Evidently, an airfoil........... does move the CP aft

This is news to me. Where is this stated?

 

[Curtis Enlow]

New Stupid Newbie Question:

I re-built the LOC IV in Open Rocket last night (the models I found online were wildly off in parts and masses) and began running simulations with different motors. I was surprised how quickly the base model became under-stable with the addition of anything but the smallest compatible 'G' motors. This is confusing to me, as in previous discussions other builders/owners have discussed having flown the IV with a pretty wide range of motors in base configuration without having mentioned the need to add nose weight, etc., to keep the rocket in reasonable a stability range.

So, my S.N.Q. of the Day is: Is the CG (for stability purposes) determined with or without the motor installed? It sounds basic, but surprisingly, I haven't found a video yet that defines whether the motor is in or out while determining this(!) I realize the CG will change as propellant is burned off and that, essentially, increases the caliber stability, but how much of a factor is that?

 

[Curtis Enlow]

This is news to me. Where is this stated?

I was looking up information on how an airfoil vs. slab-side fin affects CP and found this:

https://www.apogeerockets.com/education/downloads/Newsletter79.pdf (the subject is a little further down the news letter).

I knew that an airfoil is more effective in reacting to asymmetric relative wind than a slab-side fin, but wasn't certain about the effect on CP. Most sims don't account for this because of the equations that they use, but it seems to be the case.

 

[Nytrunner]

So, my S.N.Q. of the Day is: Is the CG (for stability purposes) determined with or without the motor installed? It sounds basic, but surprisingly, I haven't found a video yet that defines whether the motor is in or out while determining this(!) I realize the CG will change as propellant is burned off and that, essentially, increases the caliber stability, but how much of a factor is that?

Absolutely with the motor installed. Unloaded CG is useless for flight stability because you can't fly an unloaded rocket.

Openrocket used the basic Barrowman equations, which operate with a strict set of assumptions and usually give a more conservative estimate of stability (ie, CP further forward). Rocksim developers broke down the Barrowman equation assumptions and the the Rocsim method gives a slightly more accurate, less conservative value (CP further aft). Example, I fly my L1 rocket with pretty low stability according to Openrocket