building thread

[jraice]

Here, I have got my plans down a little better, I am using giantleap 7.5" tubing, two 48" sections, this gives me an easy build then 3 30" tubes and there is more space above the alt bay for the main chute. I think I am going to have the TAC-1 take the alt bay and fincan down and the nose/upper body tube will come down on a seperate chute, it will still be dual deploy. I may go with one large parachute in the future but for now this is what I will probably be doing, this winter I will get some extra cash and buy a large hemispherical chute for it, or borrow one at the launch. I think I am going to stick with the 1/4" wood but I think I might glass the entire piece of wood then cut out the rings and everything, just a little more added strength. I will probably go with a phenolic coupler with a LOC stiffer coupler inisde of the phenolic coupler, for added alt bay strength and for an edge for the bulkplates. I may go with 3/8" wood but only on the alt bay, I think the nose cone plate and centering rings and the fins will be fine with glassed 1/4". If you didnt read before the update, this will have a 54mm/25" motor tube for a CTI L730 and should beat 4K if the winds are alright. I am trusting the rocksim method, which says about 1.5 calibers (old design, mabye a little different after the update) and barrowman says about .7. Fins will probably be beveled or edged in some way (whatever my father's routers can do) and a sweet paintjob is the goal for this bad boy. One question though, what should I launch it from? Is a standard 6' rail enough? Could I use a standard rail but a longer one? I could get some 1" lugs and use the away pad.

 

[lalligood]

Originally posted by jraice
Here is a building thread for my 7.5" beast, if the mods will let me I would delete all of the other questions concerning this rocket.

FYI: The person who starts a thread can delete it by simply clicking on the "edit" button for the first post of the thread, checking the "delete" box on the next screen, & clicking on Save Changes button. Gone. Buh-bye. No more.

It would also be helpful (as discussed recently in other threads) if you had a more descriptive subject for your thread. Again, edit the first post & change the Subject line...

HTH,

 

[jraice]

I was deleting my post and putting the info in the first one, the rocksim file is being updated for the phenolic tubing, I will have it up later today. Also, is phenolic really lighter then cardboard? Rocksim seems to think it is... The only variable in the file is the weight of the tubing, I am still waiting for a reply from Ed with the tube weight, so for now I am using the PML phenolic weight.

 

[jraice]

Here is the updated rocksim file, the main chute is an estimate of 1.5 pounds, because I dont know if I am going with two chutes (connected or one takes the upper half alone) or I may possibly get one large chute.

 

[jraice]

I may be able to borrow/try out a 120" spherachute for this thing's main chute. Also, would 9/16" climbing spec TN be alright for a 20 pound bird? I dont want to hassle with the expense and thickness of 1" and I dont know why the 9/16" wouldnt work. Would it stretch/weakon over time? It is rated at 11.6 kilonewtons, not sure what that is...? Edit: the cords are rated at a little over 2500#'s.

 

[cjl]

I would guess that they would be fine. Also, shouldn't you be comfortable with Newtons, you use them all the time

 

[jraice]

Yeah, well at first I thought a newton was 4.45 times more then a pount, it is the other way around, that is what messed me up. Then I thought about it and a newton is smaller then a pound, haha, I do use them often though, but in a different sense. I am still checking to see if I can get some 1" but I might go with the 9/16".

 

[jraice]

So, I have decided to use phenolic tubing so I have no worries about the tube shreding, right? I am probably going to use a covert CR12 parachute, should give it a nice slow 14-16FPS descent, that is pretty good for fresno, if I take this thing to any hard dessert launch sites I will get a larger chute. Also, I will probably be upgrading all fins/rings/bulkhead's to 3/8" baltic birch instead of glassing them. 1" TN will probably be used as well. I am thinking two 30' sections, one for the drogue and one for the main.

 

[agrippo]

would 9/16" climbing spec TN be alright for a 20 pound bird? I dont want to hassle with the expense and thickness of 1" and I dont know why the 9/16" wouldnt work.

Check out www.shockcords.com I picked up two 30' x 1" shock cords with loops already sewn into them for $18.00 each and they are load rated for 2000 pounds.

Even better, my wife said the orange color looks "Pretty"!!!

I haven't flown a rocket with these shock cords yet so I can't vouch for their performance but I like the idea of spreading the recovery force over more area then a 9/16" shock cord does.

Another option to consider: Giant Leap sells the Fireball which is designed to cushion the force of the shock cord against the airframe during deployment.

Good Luck with the build.

Andrew Grippo

 

[jraice]

To add strength I have decided to build the motor mount/centering ring assembly, then attach all 3 fins, then slide the lower airframe over the assembly. What is the best way to get the fins straight inbetween the rings

 

[MarkM]

The way I do it:

First, slot the tube according to your fin positions and test fit (no glue) the centering rings and motor mount so that the assembly will slide in/out of the lower body tube easily. Remove the assembly. Then....

1) Glue at least one centering ring onto the motor tube at the desired position - not including the AFT ring - & let completely cure

2) Slide (no glue) the assembly into lower body tube as far as you want it

3) Fit (without glue) the aft centering onto the motor tube and into it's correct position.

4) Now, you can use the cut fin slots to line up and epoxy your fins on as usual. Let completely cure. Make sure no epoxy comes into contact between the fin and edge of fin slot or gets on the aft centering ring. If it does, after the epoxy cures, carefully use an Xacto knife to cut the bond.

5) Remove the aft centering and slide the fin can out. If there was no excess epoxy bonding that accidentally bonded the fins to the body tube, the assembly should slide out easily. Alternatively, you can *push* it out from the opposite end.

Voila! Fins epoxied to motor mount, straight and in the right positions.

6) Now, reinforce the fin-motor tube joints, glue on any remaining centering rings - except the aft ring, and attach your shock cord to the motor mount (if this is how you do it. I use a U-bolt attached to upper centering ring to anchor my shock cord, or build the fin can in a zipperless configuration.

7) Now. run beads of epoxy at the approximate locations of your centering rings - make sure they are more aft of the actual location that way the ring slides into the epoxy pushing it forward and forming a nice ridge of epoxy on the front side of the ring which will secure it nicely.

8) Carefully fit (no epoxy) the aft ring in place to assure a straight motor tube alignment. Be sure you can remove the aft ring after the epoxy sets. I fit it just part way into the lower body tube so I can grab onto it and remove it later

9) After the epoxy sets,remove the aft ring, reinforce/fillet the inside body tube-fin joints and any centering to body tube joints you can reach.

10) Now, you can finally epoxy on the aft centering ring

That's it! Now, add fillets to outside body tube-fin joints.

You're done!

This is how I've built several of my HPR rockets including my scratch built Level 2 that I'm working on now. It makes for nice, strong joints.

 

[jraice]

It is a 24 pound bird, 1" TN isn't 100% needed, but is a good added insurance. I was considering gluing the aft and mid ring onto the mount, (with lines drawn on for fin alighnment) then I would tack them on using CA glue, test fit, fillet to motor tube and rings and then slide the assembly in. I dont usually put internal bodytube to fin joints but I will consider it.

 

[jraice]

I am ordering some stuff tommarrow night (leaving for two weeks) and I want it to be here when I get back. How much shockcord should I use, and where should I place the parachute on the cord. I was thinking maybe, 35' of cord with the parachute 10-15 feet down from the upper section, for both the main and drogue? Not overkill but more then the minimum. Also that keeps the parts nice and far apart. I have also been considering adding some cluster's or airstarts to this bird. I dont think I can fund an airstart for this project, but I could add two of the new F23 (I believe they are F23) black max motor's and cluster them, that way you have the large roar and flame from the L730, but then you get some nice black smoke. I would probably use quickburst ignitor's and secure them to the rear ring, so if the L730 lights first it wont pull them out of the F23's. I will be doing it for visual effects, not performance.

 

[karatekicker271]

I can almost garuntee you that the F-23's will be the first to light... that L is a big motor and will take longer to come up to pressure

Also, why use those? You could use the (i believe it is) G-79blackjack or even and H blackjack? Those F's will be close to burn out by the time it gets completely off the pad, and will be a waste really of motor. I suggest 2 larger blackjacks... or even WL motors

 

[jraice]

Would you be worried about the F23's taking the rocket up first? It is CTI so it has a quickstart feature. I was also considering borrowing a 29/240 casing (I have one) and we could throw two H210R's in instead of the F23's. But I would be worried that they (or the F's) could lift it underpowered before the L lights. The H210's would be lit with a quickburst, while the L730 has a pryogen quick start pellet. This is an expensive rocket, wouldnt want to ruin it because the H210R's light early.

 

[jraice]

besides the fact of will it work, you guy's would go with the redlines, right? The H180 would be cool but I already have a motor with white smoke and a white flame, why not throw some red in there, the H220's would not be good, not much visual effects at all and these motors only add 400' so it is mostly visual.

 

[karatekicker271]

Originally posted by jraice
Would you be worried about the F23's taking the rocket up first? It is CTI so it has a quickstart feature. I was also considering borrowing a 29/240 casing (I have one) and we could throw two H210R's in instead of the F23's. But I would be worried that they (or the F's) could lift it underpowered before the L lights. The H210's would be lit with a quickburst, while the L730 has a pryogen quick start pellet. This is an expensive rocket, wouldnt want to ruin it because the H210R's light early.

I forgot about the CTI quickstart feature... it still will take longer to come up to pressure

NO, i would NOT be worried but the F-23's getting it off the pad first, 2 F's cant lift a 24 pound rocket. I suggest agaisnt using the H redlines because I did a cluster with two H redines, 2 G's, and a J and it wasnt pretty.

 

[marvSRG]

jraice,

Refer to my response to your post in the midpower forum called "clustering Econojets" (or something like that) for my comments on your cluster idea. Now, with reading that this is a 20 lb bird, no, those F23's won't do anything if they happen to come up first. If you go for H outboards, Redline or WL, that Cesaroni L will probably come up first, even with good, hot, igniters on the H's. At the most, they will tie with ignition time. If worse comes to worse, and the outboards do kick first, the rocket would most likely go nowhere with F23's, and if you go with H180's or 210's, they will probably get it moving well enought for the L to kick, which won't be long after they light (that is, if they do light first).

Originally posted by karatekicker271
I forgot about the CTI quickstart feature... it still will take longer to come up to pressure

NO, i would NOT be worried but the F-23's getting it off the pad first, 2 F's cant lift a 24 pound rocket. I suggest agaisnt using the H redlines because I did a cluster with two H redines, 2 G's, and a J and it wasnt pretty.

Eeeeh....that L still might come up first. They're pretty quick...I would think no quicker than an F23 with a good igniter.

Slightly off topic question for Connor: Why would you suggest against using H Redlines? If it's the flight I'm thinking of, they weren't the problem, I thought. Wasn't it your main motor not coming up to pressure in time while getting kicked out of the rocket you're problem? I don't mean that in a bad way. Just wondering

 

[karatekicker271]

It was the 2 H's that popped it off the bad before any (including the G's) of the other motors lit. which is why everything went downhill like it did.

 

[jraice]

How about using an xevion cluster thing, I saw it on his site a while back, it will fire its output at liftoff or burnout, burnout would be pretty cool with two H210R's lighting. Might have our first airstart now... EDIT: Xavien has one chip that will light the motor's at liftoff, one that will do a timer after liftoff and burnout ($40), or I could just get a $25 perfectflight timer... what would be best for an airstart (considering what they cost..)

 

[jraice]

Will it hold up? It is giantleap flexible phenolic, should go around 500MPH with 500FPS squared for the acceleration. Also, I plan on lighting the H210R's about a second after the L730 burn's out. The L730 will be supported by 3/8" rings, same goes for the H210R's. Fins are 3/8" as well. I am mostly worried about centering rings breaking, causing a shred.

 

[quickburst]

Originally posted by jraice
I may be able to borrow/try out a 120" spherachute for this thing's main chute. Also, would 9/16" climbing spec TN be alright for a 20 pound bird? I dont want to hassle with the expense and thickness of 1" and I dont know why the 9/16" wouldnt work. Would it stretch/weakon over time? It is rated at 11.6 kilonewtons, not sure what that is...? Edit: the cords are rated at a little over 2500#'s.

Your recovery system should be designed at 50X the rockets weight. This is a rule of thumb. Not cast in concrete, by any means. If your bird weighs 20lbs, then a 1000 lb recovery system would be good enough.

The 2500lb cord is more than sufficient.

Of course, your mileage may vary.

 

[cjl]

I would guess that the F23's would come up to pressure FAR before the L. Last time I launched an F23, it came up to pressure instantly, with no noticeable delay (and that was with a copperhead). IMO, Black Max is even faster at lighting than BT, so there is almost no chance of the L lighting first. As for will it hold up - I wouldn't be woried until at least .85M or 1000+f/s^2.

 

[jraice]

Well I may switch to I218R's instead of the H210R's, I have the casing and also then I could use the 38mm motor tube I have. And it is a lot more power and flame for an extra $5 a motor, or so. It should get to about 550MPH, it is flexible phenolic tubing, no glass. Also, will 3/8" rings be enough to hold the L730 and two I motor's? And will 3/8" fins be plenty?

 

[jraice]

With the I218R's it actually goes slower and has less acceleration. About 450MPH, but about a thousand more feet altitude then just an L730 alone. Should reach atleast 5K, maybe break a mile. That is with the I's lit at 4.5 seconds. I will time them to light at 4 seconds (about a 1/4 of a second after the L burn's out) and they should be up to pressure by 4.5 seconds. Acceleration also drops to 450FPS squared but it still should be up to stable speed by 40"s, and I plan on using a 10' rail if I can borrow one.

 

[cjl]

Sounds like it should be an impressive flight. I wish I could see it. As for the motor choice - sounds good, should be a nice combo. The redlines for the upper motors is a good choice (because they come up to pressure quickly). I saw a 2 staged project with a Blackjack motor for the top stage - it took so long to come up to pressure that the rocket was already arcing over - they pushed it sideways at about 200mph. The parachute saved it just in time, but he had a bit of a walk to get it back

 

[jraice]

So what sort of timing should I use for the outboards, should I go with 4 seconds, maybe 3.5? I think the L730 burns out at like 3.7 seconds. Well I am really amazed with what we are doing. First off this is a huge rocket, first L motor for use, even if it is a baby L. And our first airstart. I may build it with 1/2" rings so in the future J350's or J420R's could be used (probably the J420 redline, I600 would be fast but burn time is to fast, cant see the flame of the airstart for as long). Also, I could get a 2 or 3 grain Pro38 casing in the future, and use the smokey sam propellant for a nice visual. I am going to use a pull wire for the arming of the timer, I am still looking into getting a timer with a G switch because I would be a little worried that someone could bump the cable and the motors would light, causing an underpowered, dangerous and destructive flight. But I probably could set it up so it is very safe to use, I may even go with the idea of using the main motor to burn the wire and set off the motor, seems like the safest. I plan on having two pieces of threaded rod sticking out the side of the rocket about a 1/4", I could either attach aligator clips and do a setup were they get pulled off, or attach some thin wire to them and have the L730 burn it, that idea sounds like the safest and most reliable.

 

[jraice]

I love how I start with a single dual deploy L rocket, then airstart F motor's, then H's, now two I's, I think this will be the limit, and the final plan for this rocket. Also, BTW, I plan on mounting the timer in the main alt bay and just running wires for motor ignition and timer triggering through the drogue bay section and to the bottom of the rocket through hollow brass tubing.

 

[cjl]

Yep, sounds like you're moving away from your sig line a little there

 

[jraice]

Well, every now and then you need to ignore the sig line and well, do the oppisite ... even a small rocket (3" one I was planning) cost's double this (electronics, lots of them).