Big Daddy Lawn Darts... Show of Hands Please.

[rharshberger]

I was considering this mod. Who makes the appropriately sized coupler tube?

Balsa Machining Service C300-4, The T300 is the same as Estes 3" and the C300-4 is a 4" long coupler of the proper diameter.

 

[Back_at_it]

I was considering this mod. Who makes the appropriately sized coupler tube?

You can buy 3 inch tubes and couplers direct from Estes or Balsa machine

 

[gldknght]

I accidentally did this exact same thing a couple of weeks back. I have a old "D" BigDaddy and the new "E" model. Not thinking, i grabbed the newer "E" model and stuck a D12-3 in it and prepped it for launch. The flight went perfect with no issues. I didn't notice my mistake until I tried to remove the motor and it was stuck well up into the motor tube.... Oh well. No harm done but lesson learned.

My son and I did this with his Estes V2. Had no problem with the flight. I don't think the wrong spacer would cause the BD to lawn dart.

 

[gldknght]

I think you are on to the right track here, but maybe not for the reason you think.

I fool around with swaging bullets which involves a hydraulic press pushing lead and copper together in a hardened steel die. Even though the die is big, and the steel is strong, you can crack them if you don't know what you are doing.

The ejection charge in a rocket is not dissimilar from a hydraulic press system, main difference is the hydraulics in a rocket is powered by an explosion and the compression of air instead of an electric pump and hydraulic oil.

There is a formula that is used to describe this relationship. It is P=F/A, where P is the pressure inside the die, F is the force behind the tight fitting punch and A is the area of the punch. In our rocket case, the P, which is in pounds per square inch is the ejection charge pressure in the tube before the nose cone comes off, F is the force against the base of the nose cone and A is the area of the base of the nose cone. Since the ejection charge is set, say at 15 psi (or whatever reasonable number you want to use), we rearrange the formula to be F= P*A

Solving for the Big Daddy, the force on the nose cone would be 15(Pi*1.5^2) = 106 pounds

Solving for a rocket that is half that size, a 1.6" body tube would be 15(Pi*.8^2)= 30 pounds
.

The problem is, this formula does not take into consideration the VOLUME of the rocket body. If you have a body tube with an internal volume of 100 cubic inches, and one with an internal volume of 200 cubic inches, it takes a lot more BP in the ejection charge to pressurize the bigger tube to the same 15 psi. It's been noted the ejection charge in composite motors is easy to adjust. Not so much with what may be questionable amounts in Bp motors.

How many times has anyone seen or heard of the ejection charge of a BP motor being modified?

 

[Back_at_it]

My son and I did this with his Estes V2. Had no problem with the flight. I don't think the wrong spacer would cause the BD to lawn dart.

If the motor fits even close to snug in the mount then it will make no difference

 

[CaptHaywire]

For my next Big Daddy build I am going to lengthen the shock cord and then put 1/2 gram of BP in a tissue and drop on top of the motor. I have done this for a cluster rocket with a long air frame that flies on 4x D12 motors.

 

[Back_at_it]

For my next Big Daddy build I am going to lengthen the shock cord and then put 1/2 gram of BP in a tissue and drop on top of the motor. I have done this for a cluster rocket with a long air frame that flies on 4x D12 motors.

I have often wanted to test adding additional powder to Estes motors but I’ve never wanted to risk a rocket.

I feel like it would need to be under the clay cap to be compressed and actually explode

 

[CaptHaywire]

I have often wanted to test adding additional powder to Estes motors but I’ve never wanted to risk a rocket.

I feel like it would need to be under the clay cap to be compressed and actually explode

Try this, put a 1/2 a gram on a brick and light it with a torch. That small burst adds to the gas pressure.

 

[Back_at_it]

Try this, put a 1/2 a gram on a brick and light it with a torch. That small burst adds to the gas pressure.

I will give it a shot. I’ve had a few light ejections in larger rockets over the years and have always wanted a little more pop.

Flying my mean machine for example

 

[Steve Shannon]

Try this, put a 1/2 a gram on a brick and light it with a torch. That small burst adds to the gas pressure.

Just make a pouch using masking tape or paper and put a little black powder and an Estes igniter in it. Seal it up tight. Set it on your driveway or other non-flammable surface. Hook it to a launch controller and back up. Push the button to see what happens.

 

[Hifin Sword]

If you add a ply disc on the base of the nose cone, I see no reason to cut the slant and cover it other than for cosmetic reasons. The disc will contain the gases until the disc clears the open top of the tube. In my mod it doesn't matter because I extended the blast tube all the way up into the nose cone after enlarging the hole in the bottom. The other mod was to add an extension tube with a coupler to make it taller.
Don
P.S. EDIT: The extension of the blast tube obviates the need for the dog barf, etc. to protect the chute. The nose cone slides over the extended blast tube so the initial blast should take the NC away and once it clears the main body tube the gases will go into the atmosphere, not into the body tube.

 

[Rex R]

Bear in mind that Estes can't take all the credit for the nc design, north coast had a hand in it too. Big daddy uses the NC Patriot nose. Best mod I've seen was a ply bulkhead attached to the end of the nose

 

[cwbullet]

I have never flown one lawn dart, but I have pushed the button on a bunch that did it.

 

[Trident]

Bear in mind that Estes can't take all the credit for the nc design, north coast had a hand in it too. Big daddy uses the NC Patriot nose. Best mod I've seen was a ply bulkhead attached to the end of the nose

I have not flown it yet, but decided to do a bulkhead disc on bottom of the nose cone, attached with JB Weld. I extended the motor tube to within ~1/16” of the disc, to allow recovery gear to be packed easily, and with no wadding.

 

[cwbullet]

I have not flown it yet, but decided to do a bulkhead disc on bottom of the nose cone, attached with JB Weld. I extended the motor tube to within ~1/16” of the disc, to allow recovery gear to be packed easily, and with no wadding.

Now sure that I understand how that makes you not need wadding.

 

[Hifin Sword]

I have not flown it yet, but decided to do a bulkhead disc on bottom of the nose cone, attached with JB Weld. I extended the motor tube to within ~1/16” of the disc, to allow recovery gear to be packed easily, and with no wadding.

The extension of the blast tube into the NC of my rocket eliminates the need for the dog barf, etc. to protect the chute. The nose cone slides over the extended blast tube so the initial blast should take the NC away. And once it clears the main body tube the gases will go into the atmosphere, not into the body tube. It did require I enlarge the hole in the NC some. In your setup the hot gases will hit the bottom of your disc.

I do wonder how much of a suction inside the main body tube is created as the NC leaves the main body. But the fit of my disc is not exact and will allow some gases to bypass the disc as it travels up lessening the suction effect of an expanding volume with a set amount of gas. In my 1 launch it seemed to work as planned, although my choice of the C11 size rocket was not sufficient to carry it high enough for the chute to fully deploy. The next will be with the E12-6 motor.

I don't know if your setup will over time burn a hole into the disc or not. I'm interested in how it turns out for you though. Good luck and let us know please.
Don

 

[Hobie1dog]

after 195 replies, no big daddy for me

 

[SolarYellow]

The extension of the blast tube into the NC of my rocket eliminates the need for the dog barf, etc. to protect the chute. The nose cone slides over the extended blast tube so the initial blast should take the NC away. And once it clears the main body tube the gases will go into the atmosphere, not into the body tube. It did require I enlarge the hole in the NC some. In your setup the hot gases will hit the bottom of your disc.

I do wonder how much of a suction inside the main body tube is created as the NC leaves the main body. But the fit of my disc is not exact and will allow some gases to bypass the disc as it travels up lessening the suction effect of an expanding volume with a set amount of gas. In my 1 launch it seemed to work as planned, although my choice of the C11 size rocket was not sufficient to carry it high enough for the chute to fully deploy. The next will be with the E12-6 motor.

I don't know if your setup will over time burn a hole into the disc or not. I'm interested in how it turns out for you though. Good luck and let us know please.
Don

If you assume that you have something approximating a seal between the interior of the nose cone and the main body tube, then you have reduced the effective area the gases can work against to the OD cross section of the stuffer tube. So that's a first approximation.

In reality, you don't have much of a seal between the interior of the nose cone and the main body tube, so you're just using the labyrinth between the interior of the nose cone and the main body tube as a kind of baffle. The pressure inside the nose cone is pushing against the OD cross section of the stuffer tube, and the gas that escapes is pushing against the donut between the ID of the BT and the diameter of the hole you cut in the bottom of the nose cone. Once the nose cone moves far enough to open up the wedge, it basically uncorks the BT at that point and all you have left is the reduced and rapidly bleeding down pressure inside the nose cone pushing against the OD cross section of the stuffer tube

I don't believe that will provide nearly as positive an ejection as simply making the shoulder of the nose cone full diameter all the way until it ends, so it has a "seal" as good as its friction fit in the BT all the way until it uncorks, and then it is separated.

 

[Back_at_it]

after 195 replies, no big daddy for me

It really is a great rocket. I have several as they use to be dirt cheap at HL. Chop the slant off the cone, insert a bulk head and fly it. Since making this mod I’ve never had an issue.

Those that leave theirs stock thinking this is all in our heads are the ones still having the issue. Learn from our misfortune

 

[bad_idea]

Learn from our misfortune

I have, and I thank those of you who have faced it for sharing your wisdom.

 

[Hifin Sword]

If you assume that you have something approximating a seal between the interior of the nose cone and the main body tube, then you have reduced the effective area the gases can work against to the OD cross section of the stuffer tube. So that's a first approximation.

In reality, you don't have much of a seal between the interior of the nose cone and the main body tube, so you're just using the labyrinth between the interior of the nose cone and the main body tube as a kind of baffle. The pressure inside the nose cone is pushing against the OD cross section of the stuffer tube, and the gas that escapes is pushing against the donut between the ID of the BT and the diameter of the hole you cut in the bottom of the nose cone. Once the nose cone moves far enough to open up the wedge, it basically uncorks the BT at that point and all you have left is the reduced and rapidly bleeding down pressure inside the nose cone pushing against the OD cross section of the stuffer tube

I don't believe that will provide nearly as positive an ejection as simply making the shoulder of the nose cone full diameter all the way until it ends, so it has a "seal" as good as its friction fit in the BT all the way until it uncorks, and then it is separated.

Your statement about how effective the ejection blast will be is based on the cross section AREA of the ejection tube. But the cross sectional surface area is not the main factor that will move the NC off the main tube. It is the PRESSURE contained in the rocket before the NC separates from the Body Tube. And that pressure is not reduced by not having a solid seal between the NC hole and the ejection tube.

If any gases are ejected back thru the hole in the bottom of the NC, the gases go back into the main tube below the plywood disc. I believe the great majority of the ejection blast will be contained into the NC. Any that isn't contained ends up where it would have been without an extended ejection tube, in the main Body Tube. The plywood disc should contain any gases escaping the NC in the Body Tube, until the NC is completely above the main rocket.

The alternative is to use the traditional method of containing the gases in the Body Tube and using blankets, DB, etc. to protect the chute.
Don

 

[bjphoenix]

It really is a great rocket.

I like mine- always a great flight on a D12.

 

[Trident]

Now sure that I understand how that makes you not need wadding.

The recovery gear is down between motor tube and body tube, it never feels the direct effect of the blast. I’ve done this on another squat rocket, which had “typical“ full base on shoulder. Just leaves some soot on the nose cone base.

 

[Hifin Sword]

I like mine- always a great flight on a D12.

I hope to test mine again with an E12-6 soon. I modded mine so that it is now a 40" rocket, a Bigger Daddy. A C11-3 motor didn't get it high enough so maybe the E size will do better. If it's too strong I'll try a D size.
Don

 

[bjphoenix]

I hope to test mine again with an E12-6 soon. I modded mine so that it is now a 40" rocket, a Bigger Daddy. A C11-3 motor didn't get it high enough so maybe the E size will do better. If it's too strong I'll try a D size.
Don

Have you done a sim for it? I wonder if 6 sec delay might be too long. I use D12-3 with mine but I've seen them launched with D12-5 so maybe 6 sec is ok. I think it will fly OK but might need a long rail or rod for launch.

 

[Hifin Sword]

Have you done a sim for it? I wonder if 6 sec delay might be too long. I use D12-3 with mine but I've seen them launched with D12-5 so maybe 6 sec is ok. I think it will fly OK but might need a long rail or rod for launch.

I did an OPEN ROCKET sim and posted on the thread I started here. I was my first attempt at OR. I'm sure I did not do it correctly but I think it came out looking like my Bigger Daddy.

I launched it on 14 Feb with the E12-6. Yes, 6 secs is too long a delay. Almost hit the dirt, but popped a chute at the VERY LAST SECOND!.

Here's my ORK file below. The screen capture picture I attached apparently doesn't display well but here that is also.
Don
P.S. I could not get the OR sim to allow me to add a rocket motor so I could see how the CG was affected with a few more ounces at the tail. As is, I think it's tail heavy and will probably add an altimeter for more weight up front.

 

[PDawg]

No Kit should require any mods to fly safely, that defeats the main benefit of buying a kit.

 

[Hifin Sword]

No Kit should require any mods to fly safely, that defeats the main benefit of buying a kit.

Not sure if you were responding to my last post or someone else. My Bigger Daddy used to be a Big Daddy kit. But after it took it on the nose so to speak, I cut off the damaged section and made it 40" long into my BIGGER Daddy.

I'm new to rocketry so my mods are my attempt to find the right motor and balance for the modded rocket. From my 1st attempt at Open Rocket, it seems I do need some extra weight forward so it won't arc over into the wind.

I'm open to any suggestions. I will be trying a D12-4 on my next launch but it won't be probably until later in March.
Don

 

[Hifin Sword]

I like mine- always a great flight on a D12.

As you can see in the posts above, the E12 was too powerful so a D12-4 may be the ticket on my next launch.
Don

 

[K'Tesh]

Can we shift this back on track?
Before we do though... Don, you should download my sim of the BD, and alter it to match your needs... Guessing which motor to use is a fast way to damage or lose a rocket (or worse).