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

[DaveW6DPS]

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.

A big part of the misunderstanding among rocketeers of how aerodynamic stability actually works is the common use of approximations and "rules of thumb" in general discussion and in both Open Rocket and RockSim software.

The assumptions we put into simulation software need to be corrected to the actual numbers once the rocket is finished. This is most easily done by adding a mass object to correct the estimated weight and balance of the simulated rocket match the real rocket.

Remember the basic issue with calculations and simulations: Garbage In=Garbage Out​

What stability ratios are you getting with Open Rocket?
Have you weighed your rocket and measured actual CG (always) with the motor you intend to use and compared the simulation to relaity?

 

[Curtis Enlow]

Have you weighed your rocket and measured actual CG (always) with the motor you intend to use and compared the simulation to relaity?

Thanks, Dave. No, I haven't; I guess you can say it was all theoretical inquiries at this point. I realize that things like building techniques, quantity of adhesives, etc., can make a substantial difference.

Partially, I was looking into the numbers as I am still trying to decide whether or not to invest in both a 29mm and a 38mm RAS, as I can see the advantages, flexibility and cost savings avoiding HAZ (at least for many of the 29mm reloads) and using them in a variety of builds in the long run. I was also playing with numbers of using aluminum instead of steel fittings, but mostly I am just kinda potty-trained-at-gunpoint about reassuring myself that I am making the right decisions with the information I have at hand. I actually admire the build-it-throw-a-motor-in-it-and-fly-it folks; it mostly seems to work for them, but I can't do that

I understand that the sims are mostly good for design and CP calculations, and - at least from reviews and other threads and comments - I should wait until i have a flight-ready build in hand before putting too much stock in their numbers.

 

[The Geoff]

Curtis, all very good recommendations have been made. Since you mentioned boat building, are you familiar with West System? Especially their Colloidal Silica filler. You could give the fins a skim coat for added strength. Unfortunately with your weight limitations you are going to have a hard time. I would go with a 29mm motor for weight or look into the aerotech DMS one time motors. The LOC IV is my favorite first kit but weight was never an issue, I am now on my second with dual deploy. My first fell victim to ejection charge failure and an extended trip into some dense tall woodlands. LOC just came out with a kit called the Deployer which is 9 ounces lighter with dual deploy but its also a 3" as opposed to 4". It will give you greater mid power flexibility. I would suggest calling LOC and ask Jason or Dave for suggestions, you can't go wrong with LOC and they are great guys.

As for spirals on LOC tubing, a couple of passes with Filler Primer and you will never notice them

I got back into the sport after a 30 year hiatus after someone gave my grandson an Estes kit. LOC was my first choice with the LOC IV and now about 8 others and countless fiberglass kits and my wallet has never been the same. Wait til you get into fiberglass kits.

Welcome back!

 

[Curtis Enlow]

Hey Geoff,

Thanks!

I am familiar with West products and would probably be using them but I have an awesome composites supply shop within reasonable driving distance so I use a lot of their products, and I have the added benefit of picking their brains when I visit I am familiar with the silica, chopped fibers, micro-balloons, etc., and plan on using them where appropriate for weight and/or strength. I'm a little excited, honestly, to see how it all works out compared to other existing builds.

As far as my fins go, I just completed the finish trim/sand on my fins and I am pretty happy with the results. I added a simple tapered airfoil with shaped balsa skins on both sides and styrene leading & trailing edges (for added car-rash toughness and because they are cosmetically better than anything I could achieve by hand-sanding). I covered it all with 2 oz cloth and epoxy. They are considerably stiffer & stronger than the stock fins (which seem to the be IV's weak ink and do not make good landing gear). The slab-side 1/8" ply stock fins could be bent easily with three fingers and I cannot flex these at all. The airfoil adds an edge on stability as opposed to a slab-side fin at lower airspeeds and actually moves the CP aft a bit. The stock fin was 31g and these weigh in at 51g so I think the 20g difference per fin is an acceptable price to pay for the added benefits, and - certainly compared to some build videos I have seen online - I feel I can make up for it in other areas - micro-balloons in aerodynamic fillets, etc.. Also, looking to the near future, I am going to build a dual-deploy HP version of the IV with a e-bay coupler and extended body tube, and I think the more effective fins will be a benefit for the stretched IV-B.

I will look into the Deployer, as we have a 1500g limit at the local field (HP fields are all a four-hour drive away for me) and given the size of the field I would like dual deploy on a smaller, lighter rocket. But, honestly, I am really enjoying the design aspects (I loved designing Dollar Tree foam R/C planes, as well). So I might consider designing/building my own.

I agree on the 29mm motor approach - I already have the AT 29-38mm adapter and am looking at 29mm & 38mm Aerotech RAS systems (speaking of wallet shock...yikes...) but I can see the advantages and flexibility of having them available for the IV & IV-B as well as future builds and HAZ cost reduction.

Thanks for the welcome!

C

 

[boatgeek]

Those fins look great!

After you get a few flights under your belt, you might want to look into the Jolly Logic Chute Release for a simpler version of dual deployment. There are some tricks to using it (watch their videos carefully), but they work really nicely for mid power and smaller high power rockets.

 

[Curtis Enlow]

Those fins look great!

After you get a few flights under your belt, you might want to look into the Jolly Logic Chute Release for a simpler version of dual deployment. There are some tricks to using it (watch their videos carefully), but they work really nicely for mid power and smaller high power rockets.

Thanks

I was looking at the JLCR but had an opportunity to buy two brand new, unflown MissileWorks RRC2-Minis for the price of less than one - an offer I could not refuse! I tested both in a Foodsaver vacuum canister and a 60mL horse syringe and they work perfectly.

 

[DavidMcCann]

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

Man this place is filling up with sailors

Just move to FG rockets. makes life easier and you can steal stuff from one to work on the other.

My advice? DO NOT fill cardboard or blue tube with epoxy and balloons. bondo spot putty, elmers wood filler, or many many layers of primer filler.

56K warning...

 

[Curtis Enlow]

My advice? DO NOT fill cardboard or blue tube with epoxy and balloons. bondo spot putty, elmers wood filler, or many many layers of primer filler.

Ha! Oh, trust me, turning (A) into (B) took about 10 separate sessions of sanding the entire boat of, first, wood, then Bondo filler, then sealer, then weave fill, then micro-balloon filler, then more sealer, than primer, then more primer, then more primer and finally between coats of finish paint, all done with a (non-pneumatic) automotive long board sander by hand.

The very thought of sanding epoxy ever again fills me with dread...

No, I am all about epoxy minimalism now.

Luckily, the current IV tubes are so tight I can't even catch a spiral groove with a fingernail. I think primer will do it

C

 

[DavidMcCann]

I’m soon to be grinding down my keel. There will be no hand tools involved. No, I have no idea who did this abomination of a job.

And it looks like you’ve got a handle on finishing

 

[Curtis Enlow]

I’m soon to be grinding down my keel. There will be no hand tools involved. No, I have no idea who did this abomination of a job.

And it looks like you’ve got a handle on finishing

Yikes... You have my sympathies. Who knows what lies under that...?

I had to replace the keelson and still have to replace the centerboard case I ripped out. The original builder over-torqued the bolts and cracked all the wood. I figure it leaked from day one. He (or others) just growled on Bondi to try and stop the leak...

I've learned more than just finishing, and all of it the hard way

 

[boatgeek]

Yikes... You have my sympathies. Who knows what lies under that...?

I had to replace the keelson and still have to replace the centerboard case I ripped out. The original builder over-torqued the bolts and cracked all the wood. I figure it leaked from day one. He (or others) just growled on Bondi to try and stop the leak...

I've learned more than just finishing, and all of it the hard way

Oh, I think we know that something awful lies under that. It's just a question of what grade of awful. At least rockets don't get blisters!

I briefly considered getting into a rebuild of a beautiful lapstrake dinghy. Fortunately for my sanity and marriage, I realized it was beyond my skills, tools, space, and time availability.

 

[DavidMcCann]

Oh, I think we know that something awful lies under that. It's just a question of what grade of awful. At least rockets don't get blisters!

 

[Curtis Enlow]

Yup.

My 'little summer project' has turned into a three-year long restoration.

But, ya know? It's been fun

 

[DavidMcCann]

Yup.

My 'little summer project' has turned into a three-year long restoration.

But, ya know? It's been fun

If it was easy it wouldn't be as satisfying.

 

[Curtis Enlow]

Joined Washington Aerospace Club today.

Guess I'm committed now!

 

[Rex R]

commited eh, next stop the 'I love me jacket'.
Rex

 

[Curtis Enlow]

If I told people what I've been spending they'd probably try to have me fitted

 

[Raindog]

Hey Curtis! I'm following your footsteps, a couple months behind. I was a rocketry nut in the early/mid 70s (born in 1961.) I got away from it when I joined the military but thought about the sport a lot. Now that I am retired from two jobs and never plan to work again, I decided to start over. Like you, I ordered a Loc IV and the very night that I ordered it I read here about the SBR Fusion. I ended up ordering it tonight as it has all the options that I would want to add. I'm not sure which that I will build first. But while I'm waiting, I decided to build an Estes der Red Max, just to get my hobby feet back under me.

Good luck with your endeavors.

 

[cbrarick]

if it's not too late, build the motor tube as big as you can and adapt down. Some day you will get to a bigger field and will want to fly on a bigger motor. You can never adapt up!

 

[boatgeek]

Joined Washington Aerospace Club today.

Guess I'm committed now!

Stop by at FITS. I'll be camping out near the road on the left as you look at the pads, with a white minivan and half a gazillion high school students.

 

[Curtis Enlow]

Hey Curtis! I'm following your footsteps, a couple months behind. I was a rocketry nut in the early/mid 70s (born in 1961.) I got away from it when I joined the military but thought about the sport a lot. Now that I am retired from two jobs and never plan to work again, I decided to start over. Like you, I ordered a Loc IV and the very night that I ordered it I read here about the SBR Fusion. I ended up ordering it tonight as it has all the options that I would want to add. I'm not sure which that I will build first. But while I'm waiting, I decided to build an Estes der Red Max, just to get my hobby feet back under me.

Good luck with your endeavors.

Hey, Raindog, it's a pleasure to meet you. Yes, a few parallel lines there, except I was born a couple years earlier, early enough to remember watching John Glenn's lift-off on a B&W TV with rounded corners From there I was hooked and was a 60's 'Space Kid' (later, a 70' Space Cadet, but that's a different story ).

Wow, the Fusion looks like the Full-Meal-Deal. I'm kinda glad I didn't see that first, but I am not certain that I would have been able to keep it under 1500g. for the local field (I was looking at the Super DX3 at first, but wouldn't have any place to fly it over here unless I went rogue and flew it in some farmer's field), but it looks like an awesome rocket! I like the Level flexibility, and I am trying to build that into my IV. I have a build thread on my IV that might help in some ways, as I am a couple steps ahead I can serve as a warning of what not to do! LOL! I look forward to seeing more of your posts on your progress! Are you in the PNW? https://www.rocketryforum.com/threads/my-loc-iv-build-thread.152141/

I am SO tempted to get some other kits, but I hope to fly (and hopefully get my L1) at one of the upcoming fly-in's out on the desert. I always loved the Trident back in the day, and while Estes doesn't make it anymore I believe there are other manufacturers out there. i would love to upscale it as a project. I always thought it was the most beautiful rocket...

Stop by at FITS. I'll be camping out near the road on the left as you look at the pads, with a white minivan and half a gazillion high school students.

Hey Boat, I am really hoping to make it to FITS. If i do I will definitely look you up! Do you go to any of the Tri-City fly-in's? I might have to shoot for a bit later in the season. I am finishing the fillets on the fins now, and have started the coupler/E-bay, so, depending on my work load, I might be able to shoot for my L1 at FITS, otherwise it might be a bit later in the season. Are you East-of-the-Mountains, or in WestWa?

if it's not too late, build the motor tube as big as you can and adapt down. Some day you will get to a bigger field and will want to fly on a bigger motor. You can never adapt up!

Hey, CBarick, yes, I have kept the stock 38mm, and have also obtained a 29mm adapter and RMS systems for both sizes, so I am pretty flexible for the IV and future rockets.

 

[boatgeek]

Hey Boat, I am really hoping to make it to FITS. If i do I will definitely look you up! Do you go to any of the Tri-City fly-in's? I might have to shoot for a bit later in the season. I am finishing the fillets on the fins now, and have started the coupler/E-bay, so, depending on my work load, I might be able to shoot for my L1 at FITS, otherwise it might be a bit later in the season. Are you East-of-the-Mountains, or in WestWa?

I'm on the rainy side. I haven't made it over to the Tri-Cities launches yet, but will make an effort in future years. This summer is likely too full already. I just looked over your build thread--you're in plenty of time to be ready to fly at FITS, especially if you're willing to fly in primer instead of full paint and with single deploy instead of electronics. You could probably get it done enough to fly in a day or two. Of course, you should fly what and how you want to fly.

 

[Raindog]

Hey, Raindog, it's a pleasure to meet you. ... Are you in the PNW?

Nice to meet you too. Not in PNW (Pacific Northwest?) I'm a Southern guy. I live in Alabama but don't hold that against me. I was raised in North Carolina and Florida. I went to high school in Titusville, right across the river from the Vehicle Assembly Building on the Cape. I used to watch launches from my backyard.

 

[Curtis Enlow]

Nice to meet you too. Not in PNW (Pacific Northwest?) I'm a Southern guy. I live in Alabama but don't hold that against me. I was raised in North Carolina and Florida. I went to high school in Titusville, right across the river from the Vehicle Assembly Building on the Cape. I used to watch launches from my backyard.

You grew up next door to the Holy Land?? You should call yourself 'Luckydog' not Raindog! LOL! My best friend lives in Birmingham (she sends me bottles of John's Famous Angel Hair Slaw Sauce - it's all good )

 

[Curtis Enlow]

I'm on the rainy side. I haven't made it over to the Tri-Cities launches yet, but will make an effort in future years.

According to Google Tri-C is only :15 mins further than Mansfield (less 'windey' and more 'freeway') as I am in Arlington. I could do a standard deploy at Mansfield, but I hear there are swamps and trees where rockets go to die...? Whereas Tri-C looks like wide-open prairie. I don't mind walking

 

[rharshberger]

According to Google Tri-C is only :15 mins further than Mansfield (less 'windey' and more 'freeway') as I am in Arlington. I could do a standard deploy at Mansfield, but I hear there are swamps and trees where rockets go to die...? Whereas Tri-C looks like wide-open prairie. I don't mind walking

Not quite "wide open" but pretty much, we have a bit of low rolling terrain, no swamps, little burnable vegetation (we rarely restrict sparkies), barefoot recovery (as long as you keep it on the sod), winds tend between 10-15 mph (generally calmer in the morning and windier in the afternoons. SodBlaster (Labor Day)is our equivalent to FITS, June Swoosh is our 3 day event in June, and our next event is the first weekend in May. We have lots of folks who like to fly "pop at the top" flight profiles and most recover their rockets. This year at least one of our rocket eating cornfields is planted in peas, so no 6-8' corn to deal with (it happens to be the largest culprit for eating rockets). We have camping on site, and Pasco is only 10-12 miles away, with hotels like 15-18 miles from the launch site (Pasco Red Lion is the nearest nice hotel). Wind is our usual enemy most of the time, but we do occasionally cancel for rain/snow.
For personal referencesxabout our club, Ryan Winslow, Kris Hull, Jim Pommert, Bernard Cawley, Gordon Hom, and a few other western WA fliers are pretty regular at our events.

 

[jmuck78]

if it's not too late, build the motor tube as big as you can and adapt down. Some day you will get to a bigger field and will want to fly on a bigger motor. You can never adapt up!

I would (mildly) counter the idea of building with a bigger motor mount. My build technique has improved considerably since I built my first High Power kit, and I don't know that I would trust my earlier rocket builds with larger motors knowing what I know now. If you feel comfortable enlarging the motor mount, that's up to you, but leaving the motor mount as the stock size is probably just fine, too.

 

[Curtis Enlow]

I would (mildly) counter the idea of building with a bigger motor mount. My build technique has improved considerably since I built my first High Power kit, and I don't know that I would trust my earlier rocket builds with larger motors knowing what I know now. If you feel comfortable enlarging the motor mount, that's up to you, but leaving the motor mount as the stock size is probably just fine, too.

I agree. If the kit isn't engineered for it something is likely to fail.

 

[boatgeek]

According to Google Tri-C is only :15 mins further than Mansfield (less 'windey' and more 'freeway') as I am in Arlington. I could do a standard deploy at Mansfield, but I hear there are swamps and trees where rockets go to die...? Whereas Tri-C looks like wide-open prairie. I don't mind walking

The only trees in the recovery area in Mansfield are in the swamp, so if you avoid one, you avoid the other. Seriously, the swamp is only 50 feet wide by a couple of hundred feet long depending on the rainfall and is generally pretty easy to avoid. In our group of 5-10 flyers in 6 years, I only know of one rocket loss that was chalked up to the swamp.

Recovery barefoot does sound nice, though. Mansfield is all sagebrush desert, with bonus tumbleweeds and fox burrows. No rattlers that I've seen, though.

 

[cbrarick]

/stir pot/

I agree. If the kit isn't engineered for it something is likely to fail.

nahhh...we've pushed paper thru waay more energy then you're gonna do. Used to be that all L3 kits were paper. I've done lots of bad things to paper and haven't shred one yet...and I've tried with Warp9 and Vmax...

/stir pot off/

however, build what you feel comfortable with. The cool thing about the hobby is that there's many different things we can do. I fly hard and heavy (final iteration of my 98 mm hammerhead blue will fly in June) and I have a good friend, grouch, who's a AMAZING modeler. my nicest rocket doesn't hold a candle to the finish he puts on his. And then does mostly G's....Another flys rockets made out of Home Depot foam (AKA Foamy, Foamy 2.0...) Others fly looong and slow, reaching altitudes we can't even dream of here in the NE.

Bottom line, do what you want, have fun! keep building.

btw, nice aerotech porn.