L3 Project Construction Tips

[Ken PlattnerParticipant]

I am a climber. Although I haven’t done much since the boy’s were born. I will say this though, a figure 8 has saved my life on several occasions (really BIG wingers) and I will use it on all of my birds. A re-woven figure 8 is one of the best knots I know of for attaching a rope or cord to a fixed anchor (eg. eye hook, climbing harness, etc.). The knot is self tightening and will never slip. Plus, it’s very easy to untie if needed.

I wouldn’t be here if that knot had failed…

[Bruce R. Schaefer]

Glad that knot was there, Ken. Listen, everyone’s opinion has been very helpful. Diversity of opinion is good. If this were easy, then it wouldn’t be a challenge. Thanks. Now, another question. Tim Lehr sent me some nice extreme rail buttons, the 10-32 screw is recessed into the top of the button. There isn’t a brand name on the package, probably Blacksky. Don’t know. Conway sent me some great railbutton.com 1500’s that have the screws sticking out above, BUT they are 1/4-20 screws. And those are more heavy-duty. I noticed Joe Hinton filing down some screws in the buttons of Jon Scuba’s really nice, BIG Endeavor at the June launch. Is there any chance that the railbutton.com buttons will bottom out in the rail? Opinions wanted… which would you use? Again, thanks, Conway. You went above and beyond paying forward. Thanks, guys.

[Conway StevensParticipant]

I cant see there being an issue Bruce as long as you use the correct rail. I know many people that use the railbuttons.com buttons without a hitch. Never one time have I ever heard of anyone having to file down the screw.. But thats just me..Maybe someone else has a different experince..

[Ken PlattnerParticipant]

Here’s a thought. On one of my rockets, I used 5/16 buttons that had 3/16 or so roundhead screws (don’t know exactly). What you might be able to do is use the larger buttons, counter sink the hole slightly on one side and use a flathead machine screw, or use botton head screws which are low profile.

M2CW

[Doug GerrardParticipant]

I have used both kinds from Tim Lehr and from Railbuttons.com. Both work on the larger rail (1515 series from 8020 inc). Its your choice which you use, some like the countersink screw and built in standoff. I’m going to the Railbuttons.com on this latest project. I believe the Wildman ones have a “tighter” fit on the rail but don’t hold me to that.

Doug

[Bruce R. Schaefer]

Okay, my L3 can fly in three configurations: with a payload section, without the payload section, and using the payload section for dual deployment.

While I wanted to let the main come out from the section above the booster on two occasions, I just can’t go that way. It may not zipper or split the tube on the first attempt. May get lucky. But at this level, it’s irresponsible to rely on luck. So… I’ll go with the zipperless design pulling the chute out of the bottom of the section above the booster, even when it’s flown without the payload section. Even in the DD mode, the chute will be pulled out of the payload section from the bottom so the stress is put on the U-bolt on the base of the payload bay and not the U-bolt buried three foot up in a tube. Then again, if I use pistons, I can pop the chute out of the top and put the stress on the piston/harness–the tubes aren’t stressed; the only stress is dispursed. Okay, Schaefer, step away from the rocket. Put the drill down, hey, don’t touch those nut-serts! There’s no hurry to get this done. You have until MHM ’07 for the L maiden flight. 🙂

I have used both kinds from Tim Lehr and from Railbuttons.com. Both work on the larger rail (1515 series from 8020 inc). Its your choice which you use, some like the countersink screw and built in standoff. I’m going to the Railbuttons.com on this latest project. I believe the Wildman ones have a “tighter” fit on the rail but don’t hold me to that.

Doug

I like the standoff that Lehr’s buttons have, too. But because of the larger screws, I’m going with railcuttons.com version. I may wait until the September launch, providing there is one, to run both buttons up and down a rail. I can always add the buttons, even after it’s finished. Thanks for all the help!

[Anonymous]

JW,
Not to get personal but how’d you lose your nose cone at Balls? Where did it break?
John

John-

At BALLS the Ellis Mountain motor chuffed and just like at MHM, my bird went off on a less-than-vertical boost. This culminated in the dreaded parabolic flight pattern, meaning my apogee-deployed chute came out at high speed. The top of the airframe cut the shock cord cleanly.

The airframe tumbled from 23K+. Incredibly, I still had a beeping altimeter. The shock cord was still tied off to the ebay, but was cut on the lip of the airframe.

Incidentally, this is precisely why I flew the rocket dual deploy at MHM. It took some re-engineerning, but I’m glad I did it this way. I got the same arc on my ascent, but since there was no chute to slow things down at apogee, it all worked out. I’m a firm believer in using no drogue streamer or chute unless the bird is really heavy. In this case, it all held together. This was my first/only clean recovery over 20K (though I’ve gotten parts up there several times)…

[Bruce R. Schaefer]

Okay, maybe irresponsible was too harsh. I’m still thinking about doing my L3 the way it was originally designed, with the chute popping out of the section (30″) above the booster, and in DD, the chute popping the nosecone off the payload section (30″) and coming out from there. I agree with Denverdoc’s admonition about having a long enough harnesss (taught to me by Bill Heath after I did my first and only zipper… so far). With John Wilkes tale above, I KNOW there’s a way to protect the harness and tube lip… right now I’m thinking about leather covered in Kevlar (suggested by a friend and member, who can add to this, if he wishes) in a “bumper” configuration. With Doug’s words and experience ringing in my ears, I’m still “stepped away” from the rocket, in case anyone has a strong enough “NO, you idiot!”. 🙂

[Warren B. MusselmanModerator]

As a climber with near 30 years of experience with webbing, I will stand on the fact that a PROPERLY sewn loop exceeds the strength of the webbing every time and that knots reduce the strength of the webbing by as much as 60% depending on the knot. Poorly sewn loops are a waste and unfortunately, after buying several GLR kevlar webbing pieces, I would say they are not sewn properly. Proper sewing involves bar tacks – multiple bar tacks to say the least. I can show anyone who want to see a bunch of examples of well-sewn webbing. My mate has sewn all my kevlar shock cords and not one stitch has broken.

Warren Musselman

[Conway StevensParticipant]

Good point Warren. But as you have so well pointed out where in this hobby of ours that anyone sells products of the sewn loop kind do they do it correctly? That has been the big problem. And also they have to make sure they use the proper thread. Like Kevlar thread I beilve when they do sew it. The gasses from an ejection charge could damage the threads and possibly cause a failure I belive. I would be interested in seeing properly sewn loops.

[Author]

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