Loc Precision 3.9" V2 - how much ballast to use?

I'm newish to the world beyond Estes, and will be using G-size engines with the 29mm motor adapter. Should I use the entire bag of ballast with this model?

Thanks in advance!

Yes. The V2 has had some stability problems (stubby with small fins) so a little extra NC weight cant hurt. Also, I would fly this with harder-hitting G motors such as a G80T or a G79W. I wouldnt fly it on a long burn.
Have fun and post pics.

Alex

YES.

I built it as well. Here are some pics of mine...

https://www.rocketryforum.com/showthread.php?34885-Sirius-Saturn-V-Build-Thread&p=340475#post340475

I added an extra 1 ounce.

It flies great.

A word of advice,... anchor the lead to the nose cone. It wont stick if you just pour in epoxy / lead shot. I drilled 3 sets of holes and ran small wood dowels transverse across the tip of the nose cone. this provided a firm anchor point. easy to sand and fill to get a perfect finish afterwards.

Will do, thanks.

Thanks for the reminder to order some motors for this fantastic rocket. FWIW,... I second the harder hitting G recommendation. G78's give it a nice ride!

Quaranta said:

YES.

I built it as well. Here are some pics of mine...

https://www.rocketryforum.com/showthread.php?34885-Sirius-Saturn-V-Build-Thread&p=340475#post340475

I added an extra 1 ounce.

It flies great.

A word of advice,... anchor the lead to the nose cone. It wont stick if you just pour in epoxy / lead shot. I drilled 3 sets of holes and ran small wood dowels transverse across the tip of the nose cone. this provided a firm anchor point. easy to sand and fill to get a perfect finish afterwards.

Click to expand...

+1 to anchoring the nose weight.

The nose cone of this rocket has been tough on me. I added some weight in addition to what was supplied. I am at work now, so I can't check exactly how much, but I was nervous about the CG after looking at it with some of the bigger motors in it. I didn't anchor it, and it flew well, nice and straight on a CTI H143. When it landed, the nose weight shook loose. My plan is to glue the weight back in, and foam the empty space in the nose to hold it in place. If that doesn't work, I'm starting over with a new nose cone.

The other issue with the NC was paint: I used Rusto "plastic primer" before finishing with Rusto enamels. I did some masking, since we did the B/W checkerboard paint scheme. When I removed the tape (used the blue "low adhesive" 3m kind) the paint peeled off in a sheet.

So right now I have a flaky nose cone with a loose weight inside. I'm more interested in flight integrity than cosmetics, but either way it needs some work. I'm going to try once each to fix the paint and the weight, then will have to have a "do-over" if it doesn't work.

Gorilla Glue Polyurathane will work very nicely.Add ballast ,a few drops of water (helps the adhesive cure better) and pour in the glue ,let stand for a good 8-12 hours and once foamed up and cured ,that ballast ain`t going any where !

Works on all nosecones ,Styrene ,Polyprope. and fiberglass ,although epoxy IMO is better suited for FG.

Paul T

OK, I've finished the rocket! My wife was a little alarmed to see swastikas on the fins, despite my reassurance this this is the way they really looked, so perhaps I shouldn't post a picture? In any event, I'm a little confused about how to use the 29mm adapter that I made for it. I assume that the long end of the motor mount tube goes up into the rocket. The part that confuses me is how to keep the adapter structure from going up into the rocket on ignition (not too hard to figure out) or blasting out the bottom on ejection.

The instructions indicate to put masking tape around the coupler adapter to make it the same size as the original rocket's motor tube. But of course the coupler is already this size. Is the idea to simply make the fit as snug as possible, and hope for the best? Or is the coupler adapter actually supposed to stick 3/4" out of the bottom of the rocket? It's already kind of snug, though not snug enough.

Then it says to "use masking tape to friction fit adapter inside the main motor tube to keep the adapter in place during recovery activation". I don't really know how this is different than step one. Is there a sure-fire way to keep the adapter and motor from shifting around, now that it's already built? A simple picture would have been very useful in these instructions.

I wouldn't worry about them too much, but I'm not sure you're right about swastikas on the fins. I don't know which scheme you have, but I haven't seen any contemporary photographs with them, neither the black and white nor any of the camo schemes.

Ha, you're actually right, I used a great deal of license when I painted it.

From a show on the Military Channel I remember seeing a V2 with swastikas on the fins. It's been awhile, not positive but I think they were on a late war all green painted one. Other than that never seen them.

OK, regarding the motor mount question, Loc Precision really came through for me with the following:

Pretzelcuatl said:

OK, regarding the motor mount question, Loc Precision really came through for me with the following:
View attachment 99305View attachment 99306View attachment 99307

Click to expand...

FWIW,... and it may be too late... I use AeroPack MRS (Motor Retention System) on all my MPR / HPR Rockets. I fly my V2 using their 38:29mm adapter. Ridiculously easy.

I have a 3.9 scratch built, very comparable. I have 450gr in the nosecone (!) and my altimeter just behind. Flies like hell...hybrid or Aerotech 38mm.

I just ordered an assortment of motors from WildMan. For the V2 I'm getting:

G80 Skids
G88 Smokeys
G106 Skids
G126 White Thunder (I love these!)
G131 Smokeys

(all 29mm CTI)

I just picked up this kit and have a question related to this thread. I got a hold of a reasonable OR file for the 3.9" LOC V2 and found that I would need to add at least 24 oz of ballast (maybe 30) instead of the 4.5 oz included in the kit to get a cal of about 1 with a large motor in it. Does this match your experience?

ClusterNut said:

I just picked up this kit and have a question related to this thread. I got a hold of a reasonable OR file for the 3.9" LOC V2 and found that I would need to add at least 24 oz of ballast (maybe 30) instead of the 4.5 oz included in the kit to get a cal of about 1 with a large motor in it. Does this match your experience?

Click to expand...

How big of a motor are you talking?

I've been playing around with Cessaroni H and I motors. I used an I as an upper limit, "worst case", scenario. I will fly it on G and H most of the time.

ClusterNut said:

I've been playing around with Cessaroni H and I motors. I used an I as an upper limit, "worst case", scenario. I will fly it on G and H most of the time.

Click to expand...

I'll test mine with a 38mm CTI 3 Gr "I" tonight and let you know how much extra I'd have to add to get it to balance. I'll post tonight.

edit: it'll be tomorrow am...

Looks great I have the same kit I'm working on it right now.

For the ballast I plan to drill 2 holes in the cone and put a threaded piece of tubing about 1-2 inches. I'll drill holes in the tubing to line up w/ the holes in the cone put a wood rod through it then dump some good epoxy/glue in the tip of the cone. From there I'm going a long eye bolt and just put washers on it I can then adjust the ballast as I desire/need.

Quaranta said:

I'll test mine with a 38mm CTI 3 Gr "I" ...

Click to expand...

I balance tested with a CTI 3 Gr I-345 White Thunder.

I added 1 ounce extra lead during my build. To keep stability margin at 1.0 for the I-345, I only need 1 additional ounce (more than currently in).

Motivation...

Keeping the weight in the nose is fairly easy to do. All you have to do is sand the inside of the cone the best you can. Drill a couple of sets of holes all the way through the nose cone and insert some dowels. Epoxy your weight in, and once dry cut and sand the dowels flush with the cone. Never had a weight come loose doing it this way.

Here's a pic of my V2 nose cone:

Quaranta said:

I balance tested with a CTI 3 Gr I-345 White Thunder.

I added 1 ounce extra lead during my build. To keep stability margin at 1.0 for the I-345, I only need 1 additional ounce (more than currently in).

Click to expand...

Thanks. The sim is off for some reason, at least with the CG. The CP is likely fine. I think I will put the 4.5 oz of ballast included with the kit plus the extra ounce in the nose cone during the build. I can then do some balance testing and adjust as needed. I'll think about adjustable weighting, maybe like the mechanism described in the previous post by Dork_Vader.

Also, cut the base of the nose cone off and add a bulkhead. You need the weight up front anyway, plus this gives you a great attachment point for the shock cord. Don't trust the molded plastic lug on the nose cone for an attachment point, I've seen to many break.

Boosterdude said:

Also, cut the base of the nose cone off and add a bulkhead. You need the weight up front anyway, plus this gives you a great attachment point for the shock cord. Don't trust the molded plastic lug on the nose cone for an attachment point, I've seen to many break.

Click to expand...

That's basically what I plan to do on my kit. Then I can adjust the ballast with washers.

ClusterNut said:

Thanks. The sim is off for some reason, at least with the CG. The CP is likely fine. I think I will put the 4.5 oz of ballast included with the kit plus the extra ounce in the nose cone during the build. I can then do some balance testing and adjust as needed. I'll think about adjustable weighting, maybe like the mechanism described in the previous post by Dork_Vader.

Click to expand...

I got a copy of the RocSim file from LOC. (Thanks, Barry from LOC!) I adjusted the masses for a couple of components to match the actual weights. I balanced the partially built rocket to get a CG without chute, shock cord or nose weight and it was dead on with the OpenRocket data with those components removed from the design. If I add the chute, shock cord and motor back into the sim, I need to add 28 oz to the nose to get the CG at 1 cal. I am assuming that since the sim for the partially built rocket matches reality, then the projected needs for stability are correct. I did check the CP as well and it matches the sim within 1/2". I gather from previous replies that something like 7 oz should be sufficient. Am I missing something????

By the way, I am not discounting Quaranta's information and am using that estimate as I build plus actual balance tests. Thanks again for the help. My primary concern is in being able to get the sim programs to reflect enough reality so that I can use them to estimate altitude and drift. We have relatively small fields here and not all of the neighbors are comfortable with us. We once had a rocket returned in a police cruiser! The officer was very friendly but we obviously don't want to make it a regular thing. Anyway, it is important for us to try to keep on the field as best we can. I have been successful with sims of all of my other large rockets but this one is really off.

Just want to make sure there is no confusion... when I say I added 1 extra ounce... I mean one ounce more than provided with the kit. To balance with the CTI I-345... I'd have to add another ounce.

Quaranta said:

Just want to make sure there is no confusion... when I say I added 1 extra ounce... I mean one ounce more than provided with the kit. To balance with the CTI I-345... I'd have to add another ounce.

Click to expand...

For stability considerations, I am doing what you did...balance the actual rocket. To simulate flights, I guess I will have to fool the software by overriding weights of individual components, etc. Barry from LOC, who sent me the RocSim file, did say that the programs have problems with short, stubby rockets. I'm obviously more comfortable with your actual experience than with the iffy projections from the software in this case.