L3 Build

SilicdyneTRF
Onebadhawk
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AHansom said:
High quality eye bolt in the top of the motor!!! Easy to inspect, install and change the shock cord. Interesting idea, Using shorter motors;)
Click to expand...

Yeah, I am not too fond of an entire new bulkhead, but I am also not a fan of just having it attached to the top of the motor. The rotation might loosen the bolt, I could put a swivel on it but it could jam. I think I will just wrap some 1/2" tubular kevlar around the motor mount and epoxy it to create a Y harness, and hook that into the motor as a backup. I am feeling very indecisive about this attachment for some reason. This is by far the heaviest rocket I will have built, the previous was a Mac Performance VTS-6 which came in at 13.5 pounds, so I am second guessing. The 4" Frenzy I built will be about the same weight and I didn't feel the same way about it.
 
On the 'eyebolt in the top of the motor' front, it can be done successfully. I used loctite, a lock washer, and a swivel for my L3, and it worked great, though I will caution that once you go that route, that forward closure is basically permanently attached to the eyebolt.
 
Just a FWIW: my original Wildman was built in 2004, has 112flights on it. 2 Catoes and the Y-harness is still intact. That's 15 years of very abusive flying.

My L-3 rocket 6in diameter also has Y-harness glued to MM tube weighs 52-68lbs with big M-N's in it. no issues. 1in flat Kevlar

my 4in uses 3/8 tubular K. You have L-3 jitters and are way overthinking this.
 
blackjack2564 said:
Just a FWIW: my original Wildman was built in 2004, has 112flights on it. 2 Catoes and the Y-harness is still intact. That's 15 years of very abusive flying.

My L-3 rocket 6in diameter also has Y-harness glued to MM tube weighs 52-68lbs with big M-N's in it. no issues. 1in flat Kevlar

my 4in uses 3/8 tubular K. You have L-3 jitters and are way overthinking this.
Click to expand...

Your right, these L3 jitters are getting to me man!
 
Okay, I went for 2 clove hitches on either end of my 1" kevlar strap and then epoxied that to me the motor mount. I can attach a quick link to the loop it creates. 20190723_090356.jpg
20190723_090400.jpg

This is not coming off any time soon. I will still attach an eyebolt to the motor bulkhead and have a backup that way as it only takes the cost of the eyebolt to do so.
 
Um, I, uh, hope it's just the angle in the picture. From where I'm sitting it looks like the strap-over-strap buildup just under the notch in the ring in the second picture sticks out proud of the ring's OD. Which would be a problem.
 
jqavins said:
Um, I, uh, hope it's just the angle in the picture. From where I'm sitting it looks like the strap-over-strap buildup just under the notch in the ring in the second picture sticks out proud of the ring's OD. Which would be a problem.
Click to expand...
He's got enough stress as i tis...Let Him build and figure it out...
 
jqavins said:
Um, I, uh, hope it's just the angle in the picture. From where I'm sitting it looks like the strap-over-strap buildup just under the notch in the ring in the second picture sticks out proud of the ring's OD. Which would be a problem.
Click to expand...
Just the angle. It definitely fits, I have tested it.
 
jjwb22101 said:
On the 'eyebolt in the top of the motor' front, it can be done successfully. I used loctite, a lock washer, and a swivel for my L3, and it worked great, though I will caution that once you go that route, that forward closure is basically permanently attached to the eyebolt.
Click to expand...
How does it make it permanent? I just loosen the jam nut and back the eye bolt from the bulkhead. I suppose if you used some form of permanent thread locker or JB weld it would be hard to remove.
 
AHansom said:
How does it make it permanent? I just loosen the jam nut and back the eye bolt from the bulkhead. I suppose if you used some form of permanent thread locker or JB weld it would be hard to remove.
Click to expand...
Combination of two things - I did use red loctite, plus I messed up and didn't put a washer between the lock washer and the forward closure, so the lock washer is digging into the aluminum of the closure.
 
I fly with an eyebolt in my forward closure all the time. I use a jam nut to lock the eyebolt in place. I’ve never used loctite or a lock washer but I have nothing against either.
I do know of a guy who lost a rocket when his eyebolt unscrewed from the forward closure. I don’t know if he used a jam nut.
 
So, 3 months until launch, and I have tons of time, so an update on this build is due.

I had to put this project on hold because of college, but I am back at home and can work on the rocket.

I got the rail button mounts installed with some plywood and weld nuts epoxied to the wall of the tube:
Weld nut.jpg
Rail button mount.jpg

Fins are all tacked on and drilled for injecting fillets:
Fins 1.jpg

Fins 2.jpg
Fins 3.jpg


Lower RB.jpg
Low RB mount.jpg

Upper RB.jpg
Top RB mount.jpg

I check all the fins and they are within my standard tolerance of +-1/2 degree perpendicular to the tube.

The next steps are as follows:
Inject fillets
exterior fillets
Foam the fin can and attach the aft centering ring.

I want to see how much it weighs after foaming. It will probably be heavy enough to be slowed down enough to handle the thrust these motors throw at it. I am planning on launching on a M3464 , or M3000 after I cert on the M2550. At maximum I am expecting mach 1.9 from this rocket more likely 1.7, which the fiberglass alone can handle easily. The cert flight is only expecting mach 1.45, again a very easy to withstand velocity for the fiberglass. I have talked to other rocketeers who have gone this velocity with this size of fiberglass rocket.
 
Just a small thought. Your pic shows your rail button mounting screw sticking out from the blind nut on the inside of the tube. Also your shock cord is very close. Do not want it to snag the screw. I size mine so that they will not protrude. Good luck on your flight. Mine was going to be April 25th but looks as if it will be later this summer now.
 
David Schwantz said:
Just a small thought. Your pic shows your rail button mounting screw sticking out from the blind nut on the inside of the tube. Also your shock cord is very close. Do not want it to snag the screw. I size mine so that they will not protrude. Good luck on your flight. Mine was going to be April 25th but looks as if it will be later this summer now.
Click to expand...

Awe, that sucks. I am planning for the first weekend of June launch here, if it isn't canceled as well.
 
Ez2cDave said:
You only have a 50/50 chance of June . . . I predict this Coronavirus situation may linger on, through the Summer.

Dave F.
Click to expand...

That is possible, and good to be prepared for that eventuality. No reason not to build the rocket though :)
 
Big Update to do here. The rocket is pretty much finished as I write this, I just have to test the ejection charges and it is ready to fly. I am aiming for the launch at NCR on June 5th-6th, weather permitting.
So, here is the update.

First, injected fillets with Rocketpoxy:
Injected fillet.jpgInjected fillet 4.jpgInjected fillet 2.jpgInjected fillet 3 .jpgInjected filled 5.jpg
After this was done the fillets were next.
The fiberglass was cleaned, sanded, then cleaned again then the masking was done.Mask for fillets.jpg

Freshly made fillets that are not cured:
Fresh fillets.png

Rinse and repeat for all sides.
All fillets done. I did the fillets on the sub fins with my finder because they do not need big fillets.
Some gap filling on the end of the sub fins with Rocketpoxy:
Filling gap 2.jpg

I used an orbital sander to help with the bulk of the work, all outside. Fiberglass dust is pernicious and you do not want it inside. Then I sanded it by hand to get it smoothed down the rest of the way.
Fillets all sanded:

Fillet sanding.jpg

I do not have pictures of this, but I did fill the area around the motor tube with 2 part expanding foam, and while that was still expanding slid on the rear centering ring and held it in place while it was curing. Once that was cured I made a small Rocketpoxy fillet on the outer diameter of the rear centering ring. Then to finish up the back end I used JB weld on to attach the motor retainer. I found here I made a small error in the design of the rocket. I hadn't left enough of the motor tube out back for the retainer to fully seat on, it still has a good 1/2" out of the 3/4" on the retainer though. I am not worried about it because I will have the motor attached with an eyebolt and swivel to the shock cord, and the 1/2" on there is probably plenty strong for motor retention anyway.
Motor Retainer inside.jpg
 
I moved up the the Av-Bay now. I used LumaDyne 4-40 hardware to hold the payload section to the Av-Bay. I love using this hardware because it works very well. I never like the idea of holding a rocket together with plastic rivets, so this hardware makes it very easy to use steel screws instead. The metal on the hardware is treated to make epoxy stick to it.

Lumadyne hardware inside.jpgLuma dyne hardware coupler.jpgLuma dyne hardare outside.jpgLuma dyne hardware.jpg

Bulkplates with charge cups:
Upper BP.jpgLower BP.jpg

I moved on the priming and painting from here, putting off the electronics until later.
This photo is after 2 coats of primer using Finish 1 FP410 primer with FH411 hardener. I am spraying with an Iwata RG3-L. I like to used this primer because it does not re-activate with solvent use and it is a high build primer, so it fills flaws nicely. After each coat it gets wet sanded with 400 grit sandpaper. After the first coat revealed some imperfections in the fillets, I used some CA glue to fill them, then sanded it down. The second coat I went heavy on the fillet area and that allowed me to smooth out the fillets nicely.

Primed.jpgPrimed fin transition.jpg
They aren't absolutely perfect, but they are pretty dang close, and after the rest of the paint is on it you can't really see them anyway.
Ready for painting the first color.
Primed Booster.jpgPrimed Payload.jpg
 
I am using Dimension Overall Refinish products for painting. I used the DH 656 hardener and DR733 reducer.
Green booster.jpgGreen paint payload.jpg

This is let to cure for 24 hours to be safe, then I mask them both off.
Unfortunately I did not get a picture of the payload section masked before painting the second color.
I was painting the other rocket in the background the same color which is why it is there.
Masked for blue.jpg
Blue painted booster.jpg


Paint colors.jpg

I learned an important lesson with this paint here. When I pulled this masking tape off, the edges were ragged and the new paint pulled up. There was large section where it pulled up so I decided to fix it. I waited about 12 hours, then re-masked it all. I sanded the ragged edges and removed the ridges from the paint pulling up. Then I resprayed the blue, and pulled the tape off while the paint was wet right after spraying. This fixed the edges.

Another 24 hours later I got the decals on the rocket and then clear coated it with FC720 and FH612. I did all this so close together because once you get the first coat of paint on you have about 7 days for re-coating. After that you need to sand the surface for the paint to stick.

Painting finished.jpg
Next I put together the Av-bay sled.

Av bay sled.jpg
 

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