Parachute Question.

[loopy]

Two questions, kind of a round about way of asking them...

First off and foremost, I built an Estes Prowler, Estes Phoenix, and Executioner to take 24mm composite and Estes E motors (LOC 24mm motor tube, replaced recovery system with kevlar from motor tube through the top, replace all fins on Prowler and Phoenix with basswood, Estes E length motor hooks, Nomex heat shields). My question is, what would be the best 'chute to put in these birds? They don't weigh that much more than stock, but I'm not about to put a plastic parachute in the first modifications I've ever built. I also built a Mustang - would that parachute be a good choice?

Also, I just finished my Orbital Transport, and am not about to trust the plastic parachute that came with that kit either. Any suggestions on a replacement? With the narrow diameter of the body tube, I don't think a nylon 'chute will fit. Would mylar be a good choice?

Mark

 

[Micromeister]

Mark:
very good question, As you mentioned your modifications don't sound like they added much to the EWt: of the models. It will be fine to fly your new models with the stock size chute. Actually the Basswood change helps your chances of surviving landings undamaged.
Chute size is dependent on the burnout weight and desired sink rate. I've seen a chart somewhere that will give you the decent rate in ft/sec but I don't have a link to where i saw it, I'll look it up and post the link or scan the Doc. this weekend. Possibly someone here will have it at hand. I believe RockSim will also give a decent rate based on what size chute you select, or is that in RocketCad, Old age is really a bummer, makes you suffer from CRS disease
I'm sure someone will have the exact formulas, soon for ya, but I can easy our eggbag a little, I have an orbitai transport clone, with all the mods you mentioned and more. recovers fine on the specified 18" plastic chute, my modified Phoenix flys with a Stock 24" plastic chute, I did increase the shockcord lengths to 36". I alway use adhesive mylar "tape"dics and burnish them with a rounded dowel to improve adhesion of the disc to the plastic sheet. If you really feel it necessary to use a rip-stop nylon chute pick the lightest weight fabric you can find and sew the shrould lines to the canopy. I'm lucky I have a better 2/3rds that sews my nylon hemi chutes for me, all I had to do was lay out the gores
Relax and fly your birds, keep in mind to large a chute will likely cause a loss of your work as she flys away.

 

[rbeckey]

Estes puts oversized chutes with their kits. I almost never use the stock chutes anymore. I bought a roll of mylar foil gift wrap at Christmas time. It is over a yard wide and 12 feet long, if I recall. Mylar is lightweight, doesn't hold a crease very well, and extremely hard to tear. It also seems to withstand ejection gas blow by a little better than stock plastic. The kind I bought is metallic silver with irridescent flecks all over both sides. Extreme visibility.
I cut it into a hexagon of the desired size with a hobby knife and punch holes in the corners with a standard hole punch. I reinforce the holes with reinforcements made for notebook paper on front and back. I use kite string for shrouds, but I have considered buying kevlar thread in quantinty for this. Also, I think I'll start running the shroud lines over the top of the canopy and securing them in place in the middle. (Instead of making the line long enough to run from one corner to another, add the size of the canopy and run it all the way across and tie it at the bottom.)
I use a fishing line swivel to attach it to the model and I store them seperately form the rockets, hanging from a "clothes line" in the basement, so they don't take a set from being folded inside the body tube.
A guy is selling them on Ebay if you'd like to try one. I started using them a couple of years ago after "recycling" mylar Christmas wrap but never though anybody would buy one!

 

[MarkABrown]

Originally posted by rbeckey
A guy is selling them on Ebay if you'd like to try one.

The guy is flying_silverad, one of our TRF members. If you're interested in mylar chutes, give him a try. There is another guy selling the same thing on EBay. Check out the following link before purchasing.

https://www.rocketryforum.com/showthread.php?s=&threadid=1923

 

[jetra2]

I believe that EMRR has a descent rate calculator. You just enter the weight of the rocket, and the desired sink rate, 9-14 fps is nominal, i think, and it'll give the 'chute size.

www.rocketreviews.com

Jason

 

[sandman]

I got some of the chutes from flying_silverad.

I like 'em!

They fold nice, very high visabilaty, lightweight, kevlar shroud lines and pretty much heat resistant.

Try 'em.

sandman

 

[loopy]

Thanks for the info guys! I'll definitly look into the mylar option.

Mark

 

[kgholloway]

Loopy,

Here's an ExCel '97 spreadsheet that calculates the correct sizes of flat parachutes, both round and x-form. It's designed to give you a descent rate of about 15 ft/s. To use it just enter the rocket's weight after motor burnout in the appropriate box and read the diameter or arm dimension of the parachute.

Ken Holloway