Kevin Colvill water rocket class D record submission

:WRA2: WRA2 members only. Submit your videos and altimeter data to qualify for the WRA2 Unreinforced Bottle world record.
Unreinforced Bottle Water Rocket World Record Competition Rules
User avatar
retrotec29
WRA2 Member
WRA2 Member
Posts: 62
Joined: Sat Jul 22, 2017 7:46 pm

Kevin Colvill water rocket class D record submission

Post by retrotec29 »

For your consideration the Valkyrie3. Lauched on September 3 2017. Built from three 1.25L Crystal Geyser bottles. One bottle for the pressure chamber and two forming the nose cone and recovery bay. Fins are made from .5mm carbon plate. Complete dry weight ready to fly is 155 grams. Altimeter is a PerfectFlight Firefly using a field display for reading the data. Here is the altimeter link http://www.perfectflite.com/Firefly.html . Launch site was the Quigley Farms outside Hailey ID. Approximate altitude for launch sit is 5500 feet. Special thanks to Dave Hennessy owner of Quigley Farms for providing access to the launch site. First flight achieved an altitude of 419 feet. Second flight achieved an altitude of 415 feet. Average was 417 feet. Video was taken by my super 10 year old daughter. Video is a little chunky but she did a great job tromping around with dad. Time stamp on the on board video is off. I have tried for years to set the text file in many different ways but is always messed up. Sorry about that.
IMG_0626.jpg
IMG_0626.jpg (5.01 MiB) Viewed 197 times
Launch 1
Time: 6:46pm
Pressure: 100 psi
Water: 0.42L
Altitude: 419 ft

Ground video:



Onboard video:



Launch 2
Time: 7:01pm
Pressure: 100 psi
Water: .42L
Altitude: 415 ft

Ground video:



Onboard video:



Original Bottle with label.
IMG_0071.jpg
IMG_0071.jpg (670.65 KiB) Viewed 197 times
Pictures of final build.
IMG_0586.jpg
IMG_0586.jpg (1.99 MiB) Viewed 197 times
IMG_0587.jpg
IMG_0587.jpg (1.99 MiB) Viewed 197 times
IMG_0588.jpg
IMG_0588.jpg (1.73 MiB) Viewed 197 times
Thanks for your consideration.
No matter where you go, there you are. Buckaroo Banzai
User avatar
WRA2
Site Admin
Site Admin
Posts: 1083
Joined: Sat Dec 30, 2006 11:30 pm

Re: Kevin Colvill water rocket class D record submission

Post by WRA2 »

There is a problem with your videos. Please check to see that they are viewable by the public..
Lisa Walker,
:WRA2: Forum Administrator. :WRA2:
:WRA2:The Water Rocket Achievement World Record Association :WRA2:
User avatar
retrotec29
WRA2 Member
WRA2 Member
Posts: 62
Joined: Sat Jul 22, 2017 7:46 pm

Re: Kevin Colvill water rocket class D record submission

Post by retrotec29 »

My bad. First time using Utube this way. Should work now.
No matter where you go, there you are. Buckaroo Banzai
User avatar
anachronist
WRA2 Member
WRA2 Member
Posts: 231
Joined: Sun May 07, 2017 2:18 pm

Re: Kevin Colvill water rocket class D record submission

Post by anachronist »

Congratulations! You beat me to it. I was considering using those 1.25L Crystal Geyser bottles also due to their nice conical taper, but I'm still proving out my designs using 2 liter bottles.

I'm curious about your weather conditions. I've written a fairly comprehensive simulator that takes into account ambient temperature, barometric pressure, and humidity. Those three things affect the air density, and it can make a difference of as much as 15 meters (a cool dry day versus a hot humid day). If you can tell me your weather conditions, I can plug them into my simulator and back out your drag coefficient for you. I'd need your launch tube length also. You're at a high elevation, which would help a great deal in making the air less dense.

Assuming a 200mm launch tube and a 90 F day at 29.8" barometric pressure and 50% relative humidity, I get a drag coefficient of 0.067 to reach 417 feet. It's certainly possible to have a drag coefficient that low, but that seems unrealistically low. I'm glad to see you aren' t using your pump's built-in pressure gauge (those are notoriously inaccurate) but is your gauge calibrated?

Of course, it's also possible that my simulator is off -- hard to tell by comparison with others because others don't account for all the physics I'm accounting for.

That record will stand for a LONG time, I'll bet! You beat the previous one by 40 meters. I have a 2-liter rocket that beats it by 20 meters, but now I won't need to bother putting together an official record submission. Again, congratulations!

-Alex
User avatar
anachronist
WRA2 Member
WRA2 Member
Posts: 231
Joined: Sun May 07, 2017 2:18 pm

Re: Kevin Colvill water rocket class D record submission

Post by anachronist »

Also, I'd love to know more details about your deployment system. You seem to have it all internalized, rubber bands and all, and I found that frustrating to set up at the launch site. Right now I'm experimenting with my servo pulling in two rods that stick out about 1/4" - when they pull in, they release a couple of external hooks, each on a rubber band connected to the nose cone to hold it down, and a plastic spring pushes the nose off. Like yours, my nose cone also overlaps the payload bay a bit.
User avatar
retrotec29
WRA2 Member
WRA2 Member
Posts: 62
Joined: Sat Jul 22, 2017 7:46 pm

Re: Kevin Colvill water rocket class D record submission

Post by retrotec29 »

We are basically high desert here. Humidity is below 30 percent during the day and the tempature was 90 degrees at the time of the launch. You can hear how dry the field is in the video. We waited until the tempature and pressure hit the "sweet spot". That is when winds will go to a dead calm in the evening as the ridge and valley tempature balance. I made the trip to that field every night for a week waiting for it. Only lasts an hour or two. You are correct in your assumption that my recovery deployment is a real pain to set up in the field. The recovery pod must be removed to arm the timer and electronics. A real feat in a cut field but worth it. I wanted the air frame to be totally smooth. Every choice made during the build had efficiency in mined. So many of us think subsonic fast is pointy and swept. The best shapes for bottle rockets are blunt and tapered. The spherically blunted cone is more efficient than a standard cone. All the joints use the bottle casted shoulders. Fins are super thin but rounded on the front and tapered in the rear. The fin fillets are smooth as glass. Even the fin shape is very deliberate. A lot of time invested there in Open Rocket. I used a logging altimeter in Val 1 and 2 to gather data for a thrust curve model to add to the sim as well. All that coupled with the altitude I was expecting a drag coefficient around 0.1 to 0.2. But data coming off Val 2 came back below 0.1. Val 3 had some real improvements so 0.06 to 0.07 is not a big reach. I have six complete sims on this one rocket, 30+ years building and designing Mach+ rockets for NAR competitions and there is still a big part of what's going on I do not understand. I have a friend that is a retired rocket designer for the US military and he admits more than one design was based an educated guess.
No matter where you go, there you are. Buckaroo Banzai
User avatar
retrotec29
WRA2 Member
WRA2 Member
Posts: 62
Joined: Sat Jul 22, 2017 7:46 pm

Re: Kevin Colvill water rocket class D record submission

Post by retrotec29 »

Here is a video of the prototype recovery pod for Val1. Super simple but the G switch takes a lot of tail and error. Slotted pieces help reinforce the structure as well. I have noted some nose cone buckling on high G launches with other designs I have attempted. This may account for some designs underperforming.

No matter where you go, there you are. Buckaroo Banzai
User avatar
U.S. Water Rockets
WRA2 Member
WRA2 Member
Posts: 400
Joined: Tue Jan 30, 2007 8:16 pm

Re: Kevin Colvill water rocket class D record submission

Post by U.S. Water Rockets »

retrotec29 wrote:We are basically high desert here. Humidity is below 30 percent during the day and the tempature was 90 degrees at the time of the launch. You can hear how dry the field is in the video. We waited until the tempature and pressure hit the "sweet spot". That is when winds will go to a dead calm in the evening as the ridge and valley tempature balance. I made the trip to that field every night for a week waiting for it. Only lasts an hour or two. You are correct in your assumption that my recovery deployment is a real pain to set up in the field. The recovery pod must be removed to arm the timer and electronics. A real feat in a cut field but worth it. I wanted the air frame to be totally smooth. Every choice made during the build had efficiency in mined. So many of us think subsonic fast is pointy and swept. The best shapes for bottle rockets are blunt and tapered. The spherically blunted cone is more efficient than a standard cone. All the joints use the bottle casted shoulders. Fins are super thin but rounded on the front and tapered in the rear. The fin fillets are smooth as glass. Even the fin shape is very deliberate. A lot of time invested there in Open Rocket. I used a logging altimeter in Val 1 and 2 to gather data for a thrust curve model to add to the sim as well. All that coupled with the altitude I was expecting a drag coefficient around 0.1 to 0.2. But data coming off Val 2 came back below 0.1. Val 3 had some real improvements so 0.06 to 0.07 is not a big reach. I have six complete sims on this one rocket, 30+ years building and designing Mach+ rockets for NAR competitions and there is still a big part of what's going on I do not understand. I have a friend that is a retired rocket designer for the US military and he admits more than one design was based an educated guess.
Thanks for sharing the technical details. Congrats on the successful flights!
User avatar
anachronist
WRA2 Member
WRA2 Member
Posts: 231
Joined: Sun May 07, 2017 2:18 pm

Re: Kevin Colvill water rocket class D record submission

Post by anachronist »

retrotec29 wrote:We are basically high desert here. Humidity is below 30 percent during the day and the tempature was 90 degrees at the time of the launch.
Yup, you got perfect conditions, high desert, thin air, high temperature. Higher humidity would help even more, but a mile high at 90 degrees is pretty thin. So maybe my initial assessment of your drag coefficient being 0.6-0.7 was about right. An amazing accomplishment, and well-deserved record.

Your fins... a thin plate, even with a rounded leading edge, will still force air into turbulent separation along the surface. I had designed similar elliptical fins to yours, but using a NACA0007 airfoil instead of a flat fin. The NACA symmetrical airfoil uses a formula optimized to minimize turbulent separation at subsonic speeds. An elliptical wing shape is also efficient. My fin is made from two airfoils, the main elliptical one, and a fat heavily-tapered NACA airfoil for the fairing, molded to fit perfectly on the cone of a Crystal Geyser bottle. I designed it for 3D printing:
rocketfin.jpg
rocketfin.jpg (100.75 KiB) Viewed 154 times
Printed as a shell instead of a solid, it would probably be maybe a gram or two heavier than one of your fins, but may have even lower drag. I have printed other experimental fins, but have yet to print that one though.

You made a comment earlier about a round nose having lower drag than a pointy one. Even though most of the drag on a rocket comes from the tail end, the nose contributes a bit of air resistance. I'm curious about that comment about the nose. Everything I know about subsonic flow suggests that a pointy end (for a rocket, an ogive shape specifically) has less drag. So I created one with a base that matches the slope of the cone of a Crystal Geyser bottle:
ogive.jpg
ogive.jpg (20.29 KiB) Viewed 154 times
That's also for 3D printing as a thin shell. I'm happy to share the STL files, or the models if you use Tinkercad (which I highly recommend for designing simple parts like this, it's a 3D CAD software that works in your browser; see http://tinkercad.com for details).

-Alex
User avatar
retrotec29
WRA2 Member
WRA2 Member
Posts: 62
Joined: Sat Jul 22, 2017 7:46 pm

Re: Kevin Colvill water rocket class D record submission

Post by retrotec29 »

Pointy or blunt? Many discussions in model rocket designs over this. I guess I am a " blunt" guy. Blunt theory is that the airframe shape helps determine the nose cone shape. As you increase taper in the air frame you add more hemisphere in the nose cone. The taper creates additional suction across the nose cone. At subsonic speeds the air has time to get out of the way. The shaped flow preceding the rocket extends further as the rocket slows during the coast. This shaped flow requires no point of attack because no pile up or pressure wave is created. A smoothe blunted initial point of contact creates a more stable and even air flow. It could be argued the point is nessisary during the boost. But we are dealing with speeds below 200 mph which is very slow in determining values of nose cone design. That asymmetrical shaped airflow is also applied to fins as well. Transition points betweeen fins and airframe are super messy. I try to keep them as smooth and small as possible. Fairings or deliberately shaped transitions introduce another variable in a already super complex airflow. Nose cone shapes can also create non axial air flows which induce spin when impacting on the fins. Moving the air around the rocket as " gently " as possible is the best bet. A blunt to tapered fin I believe would create more stability and lower the drag but shaping it to out preform a .5mm plate would be very hard. So there is a bucket load of opinions I hope this helps explain some of my choices.
No matter where you go, there you are. Buckaroo Banzai
User avatar
retrotec29
WRA2 Member
WRA2 Member
Posts: 62
Joined: Sat Jul 22, 2017 7:46 pm

Re: Kevin Colvill water rocket class D record submission

Post by retrotec29 »

I had a question earlier about the gauge on my fill manifold being calibrated accurately. I think that is a fair question. So I finally got a chance to check it against a extremely accurate gauge. The EVT is touted as the most accurate air inflation device period. Accuracy is garanteed to be within .25 lbs across the mid portion of the range.
IMG_0635.JPG
IMG_0635.JPG (1.91 MiB) Viewed 141 times
Looks like my gauge may read just a hair low compared to the EVT. A read of 100 psi should be within .5 lbs of dead on.
No matter where you go, there you are. Buckaroo Banzai
User avatar
anachronist
WRA2 Member
WRA2 Member
Posts: 231
Joined: Sun May 07, 2017 2:18 pm

Re: Kevin Colvill water rocket class D record submission

Post by anachronist »

retrotec29 wrote:I had a question earlier about the gauge on my fill manifold being calibrated accurately.
That was me, because at the time I wasn't believing the drag coefficient of 0.06 so I thought an inaccurate pressure gauge may be the cause. I also bought a pressure gauge with a 1% accuracy rating (pictured here), because the gauges on both my tire pumps were way off (in opposite directions). Some weeks ago I also proposed requiring a pressure gauge with a published accuracy rating as a modification to the class D rules, so if that change is accepted, your record would still be valid.
-Alex