How be on?

This forum is for new members to introduce themselves and tell us how they got started in water rocketry.
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wormster
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How be on?

Post by wormster »

Hello all,

Wormster checking in for fun, flying and hopefully a bit of advice!

(I'm not a forum n00b, as I post on various other forums connected with my main obsession that is mine and cave exploration!)

I'm based in the UK, somewhere in deepest Somerset, home base is a little place called Cheddarmund, and I fly with a mate of mine on top of the Mendip hills at Cape Priddy!

So far I've had good results flying 2 different versions of 4liter rockets, one is a "standard" configuration, 2x 2liter cheapo cider bottles with tri tailfins and nosecone, the second is a radical (inadvertently made) 2x 2liter cheapo cider bottles with a mid mounted compound boxfin that happens to backslide!! - both get good flights at about 80psi.

Now to my GRRR at the moment - I'm making a launcher - its a barstardised version of a single tube "T" launcher, the problem that I'm having is creating an effective seal between the bottle and tube (21.5mm Osma overflow pipe) - I've tried cutting a small groove around the tube and fitting an O ring, that is supposed to seal the bottle (held captive by the usual Clarke Cable tie release mech) - I can only get about 20psi before air begins to escape - this is obviously not good!

can anyone out there in cyberland suggest a decent seal to use?
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bugwubber
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Re: How be on?

Post by bugwubber »

wormster wrote:Hello all,

Wormster checking in for fun, flying and hopefully a bit of advice!

(I'm not a forum n00b, as I post on various other forums connected with my main obsession that is mine and cave exploration!)

I'm based in the UK, somewhere in deepest Somerset, home base is a little place called Cheddarmund, and I fly with a mate of mine on top of the Mendip hills at Cape Priddy!

So far I've had good results flying 2 different versions of 4liter rockets, one is a "standard" configuration, 2x 2liter cheapo cider bottles with tri tailfins and nosecone, the second is a radical (inadvertently made) 2x 2liter cheapo cider bottles with a mid mounted compound boxfin that happens to backslide!! - both get good flights at about 80psi.

Now to my GRRR at the moment - I'm making a launcher - its a barstardised version of a single tube "T" launcher, the problem that I'm having is creating an effective seal between the bottle and tube (21.5mm Osma overflow pipe) - I've tried cutting a small groove around the tube and fitting an O ring, that is supposed to seal the bottle (held captive by the usual Clarke Cable tie release mech) - I can only get about 20psi before air begins to escape - this is obviously not good!

can anyone out there in cyberland suggest a decent seal to use?
I haven't used OSMA. If it is a drain pipe, it may not be rated for pressure- something to check on.

I have had great success with the ASTM -208 o-rings (DN 70 not 90) Nitrile or Buna-N. The o-ring thickness needed depends on the diameter of your groove but the outer diameter should be the same as the -208. My groove is 5/8" diameter. My launch tubes were made by nesting 1/2"cpvc inside two pieces of 1/2" pvc with an 1/8" gap between them for the groove.

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Re: How be on?

Post by U.S. Water Rockets1 »

bugwubber wrote:
wormster wrote:Hello all,

Wormster checking in for fun, flying and hopefully a bit of advice!

(I'm not a forum n00b, as I post on various other forums connected with my main obsession that is mine and cave exploration!)

I'm based in the UK, somewhere in deepest Somerset, home base is a little place called Cheddarmund, and I fly with a mate of mine on top of the Mendip hills at Cape Priddy!

So far I've had good results flying 2 different versions of 4liter rockets, one is a "standard" configuration, 2x 2liter cheapo cider bottles with tri tailfins and nosecone, the second is a radical (inadvertently made) 2x 2liter cheapo cider bottles with a mid mounted compound boxfin that happens to backslide!! - both get good flights at about 80psi.

Now to my GRRR at the moment - I'm making a launcher - its a barstardised version of a single tube "T" launcher, the problem that I'm having is creating an effective seal between the bottle and tube (21.5mm Osma overflow pipe) - I've tried cutting a small groove around the tube and fitting an O ring, that is supposed to seal the bottle (held captive by the usual Clarke Cable tie release mech) - I can only get about 20psi before air begins to escape - this is obviously not good!

can anyone out there in cyberland suggest a decent seal to use?
I haven't used OSMA. If it is a drain pipe, it may not be rated for pressure- something to check on.

I have had great success with the ASTM -208 o-rings (DN 70 not 90) Nitrile or Buna-N. The o-ring thickness needed depends on the diameter of your groove but the outer diameter should be the same as the -208. My groove is 5/8" diameter. My launch tubes were made by nesting 1/2"cpvc inside two pieces of 1/2" pvc with an 1/8" gap between them for the groove.

Bugwubber
Are you using an o-ring the exact same OD as the launch tube pipe? If the o-ring does not protrude a bit, it won't make a good seal.
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Re: How be on?

Post by bugwubber »

U.S. Water Rockets1 wrote:
bugwubber wrote:
wormster wrote:Hello all,

Wormster checking in for fun, flying and hopefully a bit of advice!

(I'm not a forum n00b, as I post on various other forums connected with my main obsession that is mine and cave exploration!)

I'm based in the UK, somewhere in deepest Somerset, home base is a little place called Cheddarmund, and I fly with a mate of mine on top of the Mendip hills at Cape Priddy!

So far I've had good results flying 2 different versions of 4liter rockets, one is a "standard" configuration, 2x 2liter cheapo cider bottles with tri tailfins and nosecone, the second is a radical (inadvertently made) 2x 2liter cheapo cider bottles with a mid mounted compound boxfin that happens to backslide!! - both get good flights at about 80psi.

Now to my GRRR at the moment - I'm making a launcher - its a barstardised version of a single tube "T" launcher, the problem that I'm having is creating an effective seal between the bottle and tube (21.5mm Osma overflow pipe) - I've tried cutting a small groove around the tube and fitting an O ring, that is supposed to seal the bottle (held captive by the usual Clarke Cable tie release mech) - I can only get about 20psi before air begins to escape - this is obviously not good!

can anyone out there in cyberland suggest a decent seal to use?
I haven't used OSMA. If it is a drain pipe, it may not be rated for pressure- something to check on.

I have had great success with the ASTM -208 o-rings (DN 70 not 90) Nitrile or Buna-N. The o-ring thickness needed depends on the diameter of your groove but the outer diameter should be the same as the -208. My groove is 5/8" diameter. My launch tubes were made by nesting 1/2"cpvc inside two pieces of 1/2" pvc with an 1/8" gap between them for the groove.

Bugwubber
Are you using an o-ring the exact same OD as the launch tube pipe? If the o-ring does not protrude a bit, it won't make a good seal.
That's probably what the problem is here. The -208 has an OD of 7/8 which is just slightly larger than the ID of the soda bottle's neck (and also the PVC OD). I usually shave a bevel on the rocket nozzle for easier loading. Pepsi brand bottles are now especially tough to get over the -208 o-rings without adding a bit of a bevel.

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wormster
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Re: How be on?

Post by wormster »

Problem solved, it just took a LOT of fettling to get the O ring seat right. Now all I have to do is make a base for the launcher and I'll be ready to fly!
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Re: How be on?

Post by wormster »

Concept proven, the launcher WORKS!!

Smubbly look out you have competition!
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Re: How be on?

Post by bugwubber »

wormster wrote:Concept proven, the launcher WORKS!!

Smubbly look out you have competition!
Good to hear. Have fun!
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Re: How be on?

Post by wormster »

Oh yeah youbetcha, wating for next weekend, when my mate will will be at Cape Priddy!
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Re: How be on?

Post by U.S. Water Rockets1 »

wormster wrote:Concept proven, the launcher WORKS!!

Smubbly look out you have competition!
Someone seems to be throwing down the gauntlet...

This thread is going to need a popcorn eating emoticon!
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Re: How be on?

Post by wormster »

Oh Smubbly and I get on fine no gauntlet is needed! .................He was developing his launcher for a while, I helped him build it, and have flown my rockets off it.
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Re: How be on?

Post by wormster »

Grrrrr, had to to a complete rebuild of the top end of the launcher today!!

I'd been having very good results so far, about a couple of hundred feet at 60psi, when I changed the addative mix* (was using washing up liquid and red food dye), one of my collegues told me salt was another good addative to my "Diesel" (it lowers the density of water, adding a bit more bang for your buck), the net result was that on the second flight of "Frosty Jack's One, the salt crystals (I was using an oversaturated solution) managed to act as a binding agent in between the nozzle of the bottle and the pufte tubing, either that or I got a pressure lock causing the bind up! - net result one failed launch and a knackerd launch tube!

Well anyway I had a spare section of thin walled plastic coated tube (probably an old broom or mop handle), once the plastic coating was removed (lots of burning, scraping, polishing with steel wool and sandpaper) the tube seems to be servicable its a very snug fit in the nozzle, a quick swap out session of the clarke system later I'm back to the same problem I started with - creating an effective seal that will stand over 40psi.

Its just a case of fettlement I'm sure, the Mendip Space Race will continue!!

(*My collegue (a doctor of chemistry) did say that by adding washing up liquid (to improve lubrication of the launch tube) Isopropanol alcohol (to lower the viscosity of the lube) and common salt (to lower the density of the water) - (the red food dye is just to make it look good!). Has anybody else tried such a mix or am I being led up the garden path on this one?? I can *sort* of see where he's coming from!)
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Re: How be on?

Post by bugwubber »

I'd recommend against adding particulates that can fit between the launch tube and the bottle. You can have a lot of fun without all the additives. Soap and color can be fun but keep in mind
The record holders used straight water. FWIW
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Re: How be on?

Post by bugwubber »

My experience btw, was when someone accidentally added sand to their water rocket. When i launched it, it jammed tight. Had to cut the rocket bottle open and slice it off. A bit of sanding and the launch tube was restored to flight operations.
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