- This topic has 13 replies, 4 voices, and was last updated 19 years, 5 months ago by
Bruce R. Schaefer.
Bruce R. Schaefer.-
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Bruce R. Schaefer
Yep, it’s me again. 🙂 The ebay on my L3 project has a typical ebay, housed in a 12″ fiberglass coupler that is terminated with two 1/8″ G10 fiberglass bulk plates at each end (one fits inside the coupler, the other flush with the coupler). There will be a center 4/20 All-thread holding the ends together, as well as another three for added support. I don’t want to trust just one. The parachute harness attachment is a 3/8″ U-bolt. Because the diameter is only 5″ and a number of holes will be drilled into the bulk plates for the All-threads, this threatens, IMO, the integrity of the bulk plates. Granted, G10 is strong, and the two on each end are epoxied together, but each time a hole is drilled, even a clean cut, it weakens it. More ways for the G10 to break. Under the stress and weight of the rocket (30-40 lbs.), the 3/8″ U-bolt could snap right out. What I want to do is add two, one at each end, 1/16″ aluminum plates on top of the G10. This will distribute and take any stress imparted on the U-bolt and ebay itself. Because this is where the chute is attached, this small area will take the most stress, and I want this bird to be strong enough to be SAFE and last a while. Does anyone know where I can buy, or have made, any plates like these? Only need (2) 4 15/16″ circles with a hole in the center to take a 4/20 All-thread. I’ll drill the rest of the holes myself. Jon Scuba, how about your company; can you do metal? Don’t make me have to buy an aluminum sheet and cut ’em out by hand with a carbon steel hacksaw blade… Help!!!!!
Ken Plattner
Bruce, try Aspen Machining in Lafayette. They machined for me an adapter for my scope out of aluminum stock, so I would think having a couple of plates made as you describe would be a piece of cake.
KenP
Bruce R. Schaefer
Thanks, Ken. I MapQuested them, and it’s close enough to get to on the way home from work. I’ll stop buy with a bulk plate and see if they can make what I need.
Checked in with them, Ken, and they passed me on to a sheet metal shop. I checked where I work in our machine shop, and they weren’t much help, but I might be able to get some stock aluminum from them, and I can cut it myself. Not my first choice, but, hey, worth it in the long run.
Ken Plattner
Sorry that didn’t work out. My neighbor owns Boulder Sheet Metal. All HVAC stuff but he may have something that will work for you. I’ll touch base with him this evening.
KenP.
Will the aluminum plates fin inside the airframe or on top of the plywood bulk heads? Just wondering what level of tolerance you need in the dimensions.
Just re-read your post. If all you need is 1/16″, I’m pretty sure my neighbor has some. I was looking for the same stuff a few months ago for a different project and he did have some. I’ll let you know later this evening.
Bruce R. Schaefer
Inside the airframe on the bulk plates that are 4 15/16″. The only tolerance issues would be that it can’t be large than that up to a quarter inch shorter, that’d be okay. Thanks, Ken. I really appreciate this.
Warren B. Musselman
My only comment Bruce is that I’d go with bigger than 1/4″-20 all thread for the central threaded rod. I’d go up to 5/16″, maybe even 3/8″, all-thread. That’s what I’m doing with my Competitor 5. By the way, I’m also changing the fins out for composite fins I’m building up myself on a core of 3/16″ carbon/nomex honeycomb using a clipped delta planform with a couple inches of tip chord. However, don’t look for this baby to fly until 07…
Warren
Ken Plattner
This is wierd. Thought I posted a reply. My neighbor does have (he thinks) the aluminum sheet. Says’ he’ll bring me some this weekend. I will have to cut it because he doesn’t the tool to cut it round. I can do that though.
KenP.
Bruce R. Schaefer
Ken, are you sure you want to do this? That’s an awful lot of work, unless you have the right tools. Just make sure, and let me know what I’d owe you in a PM. Thank you, and is there anything I can do in return? [posted in your rocket design review thread] You know, the more I think about this, this is really too much to ask of another rocket guy, besides this will be my L3, and I really should do all the work. If you can get 1/16″ aluminum that would be more than enough. I got some 1/16″ metal at work, and while it’s a bit heavier than aluminum, it’ll work. Just let me know.
Bruce R. Schaefer
Warren, that’s a great suggestion. But I don’t think, since my aft end is going to be a lot heavier than yours, that that may be the best route. Heavier especially since you’re going with a lighter and stronger fin. That’s impressive. I need the aluminum plates, and–while I haven’t committed myself yet, I still may use 4 all-threads at 1/4″/20 instead of one at 3/8″. I’ll also admit that just unscrewing one would be a lot easier than unscrewing four… hmmm… still want the plates, but I may rethink this. Haven’t drilled any holes yet. Thanks, Warren. You know, this site is such a great vehicle you’ve created. No wonder it’s grown so much. Great work! Now get back on vacation; the river is waiting!
Ken Plattner
Bruce the plates are finished.
Bruce R. Schaefer
Ken Plattner
Warren B. Musselman- You must be logged in to reply to this topic.