Yet another Question; Recovery?

Hey,
Well, now I have a parts list for this monster of mine. Eleven feet tall, eight inches in diameter, and hopefully around 10lbs, no more than 15lbs...1/2 Scale (semi) Patriot. Two 48" airframes and one 3 foot NC. Best of all, all the parts, including parachute(s), is under $100 or right around there, pretty cheap, eh! I'm still not sure of how to get some really good CR's but if I have to, my dad and I can do it with our Sabersaw and a lot of sanding. Now I'm trying to figure out the recovery mode (no electronics, this flight will be less than 1500 ft). I could do one parachute attached as close to the fin can as possible with the payload and NC hanging below. I could do one chute with the payload and NC hanging from the chute above the fin can. I could do two separate pieces with chutes attached to three or four foot lengths of 1" tubular nylon attached to the U-bolts. Or I could do this plus attach the two pieces with a tether. The tether could be 20 ft. of 3/8" tubular nylon or something similar. What should I do? The cost of all four are almost the same. One other thing, I am going to attach a 2" width of nylon to the u-bolt(s) in the fin can to minimize a zipper and extend that 2 feet above the upper edge of the fin can and then attach that to the tubular nylon with a quick link. So how should I attach the 2" nylon to the fin can: one u-bolt, two u-bolts and one 2" nylon piece, two u-bolts and two 2" pieces of nylon running up to the quick link? I would like to hear everyone's opinion.

Dave

Oh wow... you have some questions. My thought would be at 15 lbs, that would be one heck of a parachute.

PML has a Weight vs. Parachute Size thing you can find here: https://secure.consumersinterest.com/pml/home/images/pmlchute.pdf

PML also has good CRs that may be able to help you out.

I can't really make a suggestion cause it sounds to me that you should let preference be your guide. Sounds like either configuration will give you safe recovery. I can suggest that you run the simulations through Rocksim to see what gives you the better performance. Let us know what you decide to do and make sure you make lots of pics. Mesa love pics.

Phil is right on the money...any one of the methods you described will work fine...you just have to see what you have available in parachutes and what you want to buy. That the beauty of this hobby; diversity in methods of building, launching and recovery...just have fun!

Carl

I'm sure you know that you can certainly make your own parachute. I've made several myself and make them regularly now. They don't have to be multi-panel, complex designs. I've found several useful designs that are pretty basic and require nothing more than some rip-stop nylon and basic sewing skills. If you'd like I can certainly point you to some sources.

In the meantime, here is a link to one of many parachute sizing charts. You can probably extrapolate what you need from this. There are many others on the internet. A simple search of "parachute size" will yield several results.

https://64.177.74.25/sizer.html

Best of luck!

Marc Lee

Alright, I've chosen my design for parachute recovery. Two parachutes; one on each section of airframe; connected by a 20-50' length of 1/4 or 9/16 tubular nylon. I'll have two 1" tubular nylon extensions from the attachment point on the payload coupler and on the quicklink that attaches to the 2" band of nylon on the fin section. I am going to use one u-bolt on the payload and two u-bolts on the fincan with a harness to turn two lengths of 2" nylon into just one that will connect to the quicklink that the 1" tubular nylon will attach to. I will probably use a 54" parachute on the fin can and a 36" or 44" parachute on the payload; depends on finshed weight.
My nosecone will be 30-36" long, 8" in dimeter at the base, and have a 4-8" long shoulder. It will consist of 30-36 one inch pieces of contractors foam cut out and glued together on a 54mm MMT to save weight. Unfortunately, I have a slight problem. I'm not sure whats the best way to connect this "large" nosecone to the payload tube; any ideas? I thought of bolts and threaded inserts in some plywood attached to the shoulder...but how to attach it?
Second problem-fiberglassing. Although not really a problem I would like to hear what some of you may have done. I am going to fiberglass this styrofoam nosecone when I'm done. I've never done any 'glassing before but yeah, you gotta start sometime. I would like to know what kind of fiberglass cloth to use (remeber I want to keep it light)? What kind of resin to use (remember it can not "melt" the styrofoam)? What is the best method to apply the 'glass (easiest)? So, guys, how bout these questions, eh.

David Kneble

hmmm, fiberglassing? You should check out the techniques section. There is a great thread in there by Carl Tulanko on how to do fiberglassing. As far as which epoxy to use, most people swear by West Systems epoxy. I've not used it myself but, if I do a much bigger project like you, I would. As far as its reaction to the foam, you'll just have to test it before you commit to any one type of foam or epoxy.