A question to FTC builders

[Azriel]

Have any of you guys ever considered building slender rockets out of reinforced pvc? I know it's not an ideal material out here in the dessert (30+C temp is bad for the integrity of pvc after all) but I was curious if the superior pressure rating of pvc, not to mention low relative cost, ever came into play for rocket design. I've so far only built rockets out of 2 and 3 liter bottles, and while I do like their general performance, I'd like to eventually build either a FTC or PVC rocket to be placed in a large scale booster rocket system I've started designing. While it more than likely won't conform to the competition standards, (pvc is a bit heavy since it is so thick, and the rocket boosters are excessively large) I'd love to launch a water rocket to at least a mile in height.

Just hoping for some input.

[Nick B]

a: waaay to heavy
b: will go thur a car or home roof lika bunker buster in the afgan mountains, if something goes wrong.




Somebody here tried it tho.

It's in the forum threads somewhere.

[WRA2]

Have any of you guys ever considered building slender rockets out of reinforced pvc? I know it's not an ideal material out here in the dessert (30+C temp is bad for the integrity of pvc after all) but I was curious if the superior pressure rating of pvc, not to mention low relative cost, ever came into play for rocket design. I've so far only built rockets out of 2 and 3 liter bottles, and while I do like their general performance, I'd like to eventually build either a FTC or PVC rocket to be placed in a large scale booster rocket system I've started designing. While it more than likely won't conform to the competition standards, (pvc is a bit heavy since it is so thick, and the rocket boosters are excessively large) I'd love to launch a water rocket to at least a mile in height.

Just hoping for some input.

I believe that this has been tried many times over the years. What you will find is that the PVC will be too heavy at the pressures that it can hold without adding reinforcement (which adds even more weight). That is probably why you don't see too many people building their rockets out of it. The price makes it very tempting though. Another issue you might face is that the PVC plastic is soft and flexible (especially so in long lengths).

[Azriel]

hehe, wasn't considering the going through a car aspect.

[quote="WRA2"][/quote]
In terms of holding pressure, you may be surprised. an approx 1.3" OD 1" ID length of PVC can hold pressures upwards of 1k psi without bursting. That of course isn't always the case, and adding heat drastically reduces that, but in 20C temp weather the pipe is guaranteed to hold at least 400 PSI by the manufacturer, and with even just strapping tape the holding pressure can easily be 600+ PSI for a launch. Not to sound gaudy, but there is a reason homemade pipe bombs are often made of pvc and not soda bottles ;)

But weight and rigidity can certainly be serious safety issues I hadn't thought about. I'll have to rethink my plan a bit, for safeties sake

[Brian]

Another issue which has been discussed was that sunlight, age or hard landing make it brittle. Because of this it can shatter when pressurized and PVC dosen't come up on X-Rays.

[WRA2]

I'd like to eventually build either a FTC or PVC rocket to be placed in a large scale booster rocket system I've started designing. While it more than likely won't conform to the competition standards, (pvc is a bit heavy since it is so thick, and the rocket boosters are excessively large) I'd love to launch a water rocket to at least a mile in height.

Just hoping for some input.

The weight limit is not just for competition purposes. If you launch a rocket over that limit you will need to get certified for "high power" and launch at a pyro launch site where they have airspace clearance to launch those large rockets.

[Azriel]

I'd like to eventually build either a FTC or PVC rocket to be placed in a large scale booster rocket system I've started designing. While it more than likely won't conform to the competition standards, (pvc is a bit heavy since it is so thick, and the rocket boosters are excessively large) I'd love to launch a water rocket to at least a mile in height.

Just hoping for some input.

The weight limit is not just for competition purposes. If you launch a rocket over that limit you will need to get certified for "high power" and launch at a pyro launch site where they have airspace clearance to launch those large rockets.

You need a certification just for the larger weight? I thought model rocketry certifications were for just the power output of larger motors?

[WRA2]

I'd like to eventually build either a FTC or PVC rocket to be placed in a large scale booster rocket system I've started designing. While it more than likely won't conform to the competition standards, (pvc is a bit heavy since it is so thick, and the rocket boosters are excessively large) I'd love to launch a water rocket to at least a mile in height.

Just hoping for some input.

The weight limit is not just for competition purposes. If you launch a rocket over that limit you will need to get certified for "high power" and launch at a pyro launch site where they have airspace clearance to launch those large rockets.

You need a certification just for the larger weight? I thought model rocketry certifications were for just the power output of larger motors?

Yes you do. A heavier rocket is considered a danger to aircraft. I believe the laws were written to cover pyro rockets where larger and heavier rockets usually carried larger and more powerful engines. Any rocket that weighs more than 1500 grams is no longer considered a "hobby rocket" and that is where certification and air clearances are needed. You probably could get away with flying it if you found a large deserted area to fly it in but should something happen, I wouldn't want to be you.

[WRA2]

Weight limits and laws aside, the weight of the PVC will make it not go as high as you hope...even at the pressures you mention in the post above. I suggest using one of the available simulators to see that the weight of the PVC makes it not practical. A reinforced lightweight rocket will be able to hold as much or more pressure than the PVC can at a fraction of the weight.

[Nick B]

I'd like to eventually build either a FTC or PVC rocket to be placed in a large scale booster rocket system I've started designing. While it more than likely won't conform to the competition standards, (pvc is a bit heavy since it is so thick, and the rocket boosters are excessively large) I'd love to launch a water rocket to at least a mile in height.

Just hoping for some input.

The weight limit is not just for competition purposes. If you launch a rocket over that limit you will need to get certified for "high power" and launch at a pyro launch site where they have airspace clearance to launch those large rockets.

Ditto on this.
You need to get certified for legal launches at approved sites.

Do some research at the powder rocket sites. You will be launching something that will hammer thru cinder blocks if the chute fails. If HSA get wiff, they will lock you up and put a probe in your pooper.

[Nick B]

but there is a reason homemade pipe bombs are often made of pvc and not soda bottles ;)

Orly?


Do tell......

[Azriel]

Well, I do have 100 miles of desert in every direction from the outskirts of my city to any other town

I suppose a majorly reinforced PET Booster/FTC sustainer would be a better choice anyway. I'm thinking 3 stage rocket, with 2 booster stages and then a FTC sustainer, each stage having a gradually decreasing nozzle bore size. Going from 3-liter bottle (around 1-1/2 inch bore, roughly 36mm) to a slightly smaller than standard 2 liter bottle nozzle (18mm bore or so) to about a gardena nozzle bore size (9 mm). I'll run a simulater later to tweak each bore size as necessary, but I figure going from faster burn/higher impulse to slow burn/lower impulse would work out pretty well for getting a relatively high altitude for a multiple stage rocket.

[Nick B]

Well, I do have 100 miles of desert in every direction from the outskirts of my city to any other town .

Boo...
Not fair....




I hate you guyz
always launchin 12 foot 120000 altitude rockets.



Must be nice.

Me no like spiders n scorpions tho...

[Azriel]

Well, I do have 100 miles of desert in every direction from the outskirts of my city to any other town .

Boo...
Not fair....




I hate you guyz
always launchin 12 foot 120000 altitude rockets.



Must be nice.

Me no like spiders n scorpions tho...

yeah, the scorpions are a bit of a pain getting used too... I hate how they can get through any crack in your house...

And hey, so far the highest I've been was 35000 ft, not 120000

[Nick B]

And hey, so far the highest I've been was 35000 ft, not 120000

120000 was the 2011 Qu8ke hight . Not a record, but def a balla rank shot.


Petty cash......