Vellum/Mylar tubes???

[GL-P]

I'm interested in making a few vellum or mylar tubes for competition. I understand the basics but I'm interested in anyone with experience can give me the pros and cons of vellum or mylar and how hard it would be to get a vellum or mylar tube to go mach.

Thanks!!!

 

[powderburner]

The purpose of using vellum or mylar is to achieve a feather-weight airframe tube for duration and altitude contests. The rocket configurations that use these materials are all subsonic designs (and I mean waaaay subsonic).

To get going faster than Mach 1 with a vellum or mylar BT, you would probably have to layer it so thick that you might as well skip this material and start off with a more suitable tube.

 

[GL-P]

That's what i thought. I have a 9-10 oz maxiumum weight where I need to fit an altimeter so I'm very weight hindered.

 

[Stymye]

https://yellowjacketsystems.com/alway/tomaschrandd.htm

 

[GL-P]

I've already read that report. I know now for sure that vellumor mylar tube won't solve my problem

 

[Stymye]

.....sorry , you asked for info.....

 

[powderburner]

Originally posted by GL-P
That's what i thought. I have a 9-10 oz maxiumum weight where I need to fit an altimeter so I'm very weight hindered.

You have imposed a 9-10 oz max wt on your design? Or you need to squeeze in a 9-10 oz altimeter (the mother of all altimeters?), maybe inside a limited diameter that in turn requires a thin-shelled BT? Sorry if I am a little dense here, but I don't quite get what your question means.

 

[GL-P]

Sorry, my total weight limit is 9-10 oz. The motor subtracts 4oz so I'm left with 6oz. I can go above 10 oz total weight but I lose out on altitude fast. Any ideas for ultra lightweight rocket???

 

[powderburner]

1. get or build a tower launcher ---- sink some old conduit into a pail of cement and space them to contain your rocket ---- do NOT use launch lugs, or buttons, or any other protruberances

2. fiberglassed equivalent BT (I think there is a website somewhere that shows how to do this)

3. make or buy a conical NC with a nice length/diam ratio (maybe 4, 5, 6?) ---- protect the tip to keep it as pointy as possible and do not round it off

4. G10 fins, as small as possible, as thin as possible, as smooth as possible, as sharp as possible ---- this is one flight where you are going to have to take a risk on getting some landing damage--- to minimize drag, the fins need to be knife-edge sharp front & rear

5. go find the world's smallest altimeter (I saw some very light electronics recently on R.O.L.) and match it up to the lightest possible wiring, on-board power supply, smallest possible ejection charge, smallest streamer, etc.

6. prime, sand, polish, and paint very lightly to end up with a smooooth exterior surface ---- concentrate on the front half of the rocket and the front half of the fins

 

[GL-P]

1. Yep. I got one.

2. A friend told me how to make phenolic tube with isopropyl alcohol and epoxy

3. Have a lathe and will make a balsa conical around 6:1

4.1/16 inch G10???

5.I might be able to use a recording altimeter for testing. It's the size of a Bon Nova one.

6.Will look further into it

Any ideas on good planform shape? I plan on using a 30-60-90 shape but is there any you know of that are better???

 

[powderburner]

the 30-60-90 fin planform is probably as good as any other for what you are trying to do
more important than planform, you really need to get a good sharp leading edge and trailing edge on each fin
if you are making delta fins (taper to zero chord at the tip) remember to taper the thickness as well

 

[DynaSoar]

Originally posted by GL-P
Sorry, my total weight limit is 9-10 oz. The motor subtracts 4oz so I'm left with 6oz. I can go above 10 oz total weight but I lose out on altitude fast. Any ideas for ultra lightweight rocket???

From your signature line: "If only carbon cloth was cheaper!"

A yard of 2" carbon fiber Aerosleeve is $13.75. A 34 inch 24mm/BT50 coupler stock tube, to use as a mandrel, from BMS is $4.00. Cut the sleeve in half and stretched over the coupler tube, you can make a double layer 24mm tube about 20" long. The sleeve will weigh 1.3 ounces. Add the weight of the Aeropoxy or other curing resin plus finish coat, and it'll come in between 2 and 2.5 ounces, can contain your altimeter, shock cord and chute (all attached to the nose), can hold an AT G55 motor, and will definitely handle Mach.

 

[GL-P]

Awesome, I'll look into it! I've always wanted to try to make carbon fibre tubes.
I can use the stuff for fins too!!! Unfortuneatly I have a RF locator so the carbon cloth will affect the signal. I guess I could do a carbon fibre lower end with the electronics bay out of fibreglass.

Thanks!!!