#1 Reason Things Should Change

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Woody's Workshop

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If all Nose Cones were balsa, the Shoulder should be turned down to fit inside a Tube Coupler.
The reason I say this is simple, Help Stop Zippering.
Plastic nose cones can not be done to fit inside the BT coupler.
Balsa can be. And should come that way and each kit should have a High Density Coupler for anti zipper effect.
Over the 45 years I've launched LP rockets I've had numberous zippers.
Some with this method would have not happened.
Others, nothing short of a steel ring would stop the zipper.
But, I think it is well advised that ALL manufacturers relate to this problem and do what they can to solve it.
No flight is perfect, well, I could be wrong on that...With that said, I've fallen inches of catching the chute on the end of the launch rod several times.
But my Super Big Bertha, which I fabed to a 2 stage;
It launched great, got about 200 feet off the ground, Shot the D12-0 right at the launch pad, leaned over in a delay of the sustainer...
And ended up with a horizontal trogectory arching into the woods. As the chutes opened into the tree tops, ZIP.
If a tube coupler was in place, and a balsa nose cone instead of a plastic one, I would have less than and inch of zip instead of 8" of zip.
And it would have been saved.
But I should have known better to launch it in 30 mph winds, but as the old school ass I am, nothing will stop me.
Maybe I should make this a Poll?
 
What are you using for a shock cord? I can't imagine it is the elastic type found in Estes kits... if that is the case, it seems a bit daft to complain about something needing to change in kit design when the zipper issue you have is due to a change that you yourself made to the design of the kit.
 
I don't know if you are joking or not, but launching in any winds above 20 mph is a violation of the safety code.

You will never get a big company like Estes to change their designs, but you can always purchase your own mods from places like Balsa Machining. Maybe Dr. Zooch and Fliskits would be open to a discussion.
 
I've only used the rubber band shock cords in a few first builds.
I substituted that for sewing elastic after the rubber band baked and become brittle.
Later on I used sewing thread, and today I use Kevlar Thread.
Just saying...
It would be nice for extra comfort, as it's a stress point.
 
If your using balsa nosecones then it's easy to hand turn down the shoulder to fit. I bought a bunch of SEMROC Centuri-sized nosecones when they were about to sell to eRockets. The cones are just slightly too big. I wrap a piece of 120 grit sandpaper around the shoulder and twist until it fits the tube. Turning a cone is a way for your cone to fit a coupler tube reinforcement.

You can soak in some CA around the end of the tube to toughen it up, epoxy will do the same thing. Then sand it smooth. I do this to all my rockets to both ends of the rocket. The motor mount tube benefits from this also.
 
You didn't help your cause launching in high winds. Rockets will always obey the laws of physics no matter how good your intentions are. Launching in 30 mph winds is asking for your rocket to weather cock. Remember, even NASA has limits where they scrub missions. The > 20 mph launch restriction is codified per NFPA 1122 (2008) § 4.17.1 and in NAR Model Rocket Code Safety § 9.

That said, there are a number of fabrication techniques that you can use to mitigate the risk of zippers. Some are not that hard to implement.

Greg
 
Try using flat sewing elastic and make it longer than the factory size.
For the Super BB I would go with 3/8 or 1/2 inch wide by 10 feet long.
For BT-55 to BT-60 use 1/4 inch wide at about 6 to 8 feet.
For BT-50 or smaller use 1/8 or 3/16 inch wide at about 4 to 6 feet.
I hope this helps.
 
I've launched countless LPR rockets and I've never once had a zipper... (knock on wood)... This may sound stupidly obvious, but make sure you're using a motor with a recommended delay.
 
Hi Woody,
It's an interesting idea, but in smaller tubes (BT-5, 20 and 50) the inside coupler edge might impede ejection of the parachute.
I've never had a zipper flying LPR models. My Kevlar lines don't go beyond the upper body tube edge.
I also use flat elastic for shock cords. LONG flat elastic to help prevent snap back dents.
Flat elastic shouldn't cut through a body tube edge at ejection.

I doubt Estes would want to change their design practice.
People have been hinting for Estes to use Kevlar shock cords and to phase out tri-fold mounts.
But that shouldn't stop you from incorporating the coupler idea in your models.
On BT-55 and larger models it might be a great idea.
 
I've only used the rubber band shock cords in a few first builds.
I substituted that for sewing elastic after the rubber band baked and become brittle.
Later on I used sewing thread, and today I use Kevlar Thread.
Just saying...
It would be nice for extra comfort, as it's a stress point.

Hi Woody, I think it's a good idea. I had the same idea but approached the problem in another way.

I cut off the shoulder from a plastic nose cone and smoothed off all the edges. The top several inches of the body tube where saturated with thin CA. Any card board burrs sticking up after the CA dried were knocked down with course sand paper until the nose cone shoulder (now a plastic ring) slid in with a nice friction fit. It was then JB Weld'd into the top of the body tube. Later, when I get around to it, the bottom of the ring and the adjacent body tube wall will be filled in with JB Weld to provide a smooth transition from one diameter to the other diameter.

The new bulkhead needed for the nose cone was made from birch ply wood left over from another project. A coupler was modified so would fit inside and slide out of the plastic ring. The coupler was saturated with thin CA, sanded smooth and then attached to the nose cones bulkhead with JB Weld. The slit in the coupler left over from the cut can be covered with the scrap piece of coupler left from cutting the coupler. It will be glued on the inside of the coupler of course.

This modification slides in and out slicker then snot! This rockets future is zipperless even with the entire shock cord made of kevlar!!!

IMG_1542.jpg

IMG_1541.jpg

IMG_1543.jpg

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IMG_1515.jpg
 
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Hi Woody, I think it's a good idea. I had the same idea but approached the problem in another way.

I cut off the shoulder from a plastic nose cone and smoothed off all the edges. The top several inches of the body tube where saturated with thin CA. Any card board burrs sticking up after the CA dried were knocked down with course sand paper until the nose cone shoulder (now a plastic ring) slid in with a nice friction fit. It was then JB Weld'd into the top of the body tube. Later, when I get around to it, the bottom of the ring and the adjacent body tube wall will be filled in with JB Weld to provide a smooth transition from one diameter to the other diameter.

A new bulkhead needed for the nose cone was made from lite ply wood. A coupler was modified so would fit inside and slide out of the plastic ring. The coupler was saturated with thin CA, sanded smooth and then attached to the nose cones bulkhead with JB Weld.
Awesome!!! Woody was thinking outside the box, but this is where thinking INSIDE the box fits best.
 
La
ter on I used sewing thread, and today I use Kevlar Thread.


That's why you'll never see Kevlar shock cords in Estes kits, if I have anything to say about it.


John Boren
Head of Estes R&D
 
Hi Woody, I think it's a good idea. I had the same idea but approached the problem in another way.

I cut off the shoulder from a plastic nose cone and smoothed off all the edges. The top several inches of the body tube where saturated with thin CA. Any card board burrs sticking up after the CA dried were knocked down with course sand paper until the nose cone shoulder (now a plastic ring) slid in with a nice friction fit. It was then JB Weld'd into the top of the body tube. Later, when I get around to it, the bottom of the ring and the adjacent body tube wall will be filled in with JB Weld to provide a smooth transition from one diameter to the other diameter.

The new bulkhead needed for the nose cone was made from birch ply wood left over from another project. A coupler was modified so would fit inside and slide out of the plastic ring. The coupler was saturated with thin CA, sanded smooth and then attached to the nose cones bulkhead with JB Weld. The slit in the coupler left over from the cut can be covered with the scrap piece of coupler left from cutting the coupler. It will be glued on the inside of the coupler of course.

This modification slides in and out slicker then snot! This rockets future is zipperless even with the entire shock cord made of kevlar!!!

As usual, count on Bradycros for a clean execution of a good idea. I wish I could get my glue lines to look so neat.

For those new forum members, pay special attention to Brady's pictures. I learn something from them all the time. In particular, the picture of the close up of the nose cone showing the screw eye looked a bit odd to me. I zoomed in all the way by clicking on it a few times, and on maximum resolution it appears to me that he has used JB weld on part of the screw eye to smooth over the part where the rounded part of the screw eye meets the straight part. Presumably to make sure there are no snags of cord, or if it is a bent screw eye, to ensure it stays closed.

Bradycros, would you care to comment on this? Have I misinterpreted the picture, or is this indeed some epoxy on the screw eye? Enquiring minds want to know...

Marc
 
As usual, count on Bradycros for a clean execution of a good idea. I wish I could get my glue lines to look so neat.

For those new forum members, pay special attention to Brady's pictures. I learn something from them all the time. In particular, the picture of the close up of the nose cone showing the screw eye looked a bit odd to me. I zoomed in all the way by clicking on it a few times, and on maximum resolution it appears to me that he has used JB weld on part of the screw eye to smooth over the part where the rounded part of the screw eye meets the straight part. Presumably to make sure there are no snags of cord, or if it is a bent screw eye, to ensure it stays closed.

Bradycros, would you care to comment on this? Have I misinterpreted the picture, or is this indeed some epoxy on the screw eye? Enquiring minds want to know...

Marc


Good eye Marc. The space in the eye bolt is indeed filled with JB Weld to prevent the shock cord from snagging and wearing out prematurely, being cut or working itself loose.

Any speculation on why the hole in the center of the bulk head has slots worked into it?
 
I use either a fishing leader line or fine Kevlar thread to go up to within about an inch from the top of the body tube. I usually anchor it thru the top centering ring of the motor mount. On larger tubes the fishing leader is my preferred anchor since its snap swivel can be reached. Smaller tubes are better served by the Kevlar, with a loop at the top. The loop or snap swivel is the attachment point for flat elastic. The Kevlar or stainless steel leader won't cause any zippering, since it does not exit the body tube. When the elastic gets old or scorched accidentally, it is easily replaced.

Fishing leaders in 6", 12", and 18" lengths can be found in the sporting goods department at Walmart.
 
That's why you'll never see Kevlar shock cords in Estes kits, if I have anything to say about it...

Mr. Boren:
I initially disagreed with your insistence on rubber shock cords, having become quite the fan of elastic and Kevlar, but I have to admit that recently I've come around to see your point. I inherited a bunch of rockets that were pre-built with their rubber shock cords. These were poorly built rockets and I've been flying them a lot just to use them up. While rubber cords will degrade over time and eventually disintegrate, I have found that they do a really good job of holding up to numerous launches in the short term, maybe even better than elastic. The most surprising difference however, is that it is SO MUCH EASIER to feed a rubber cord into the body tube than an elastic one. The rubber drops right down the tube while the elastic/Kevlar has to be wadded up and forced in like putting a cat in a pet carrier. This has made me rethink my building philosophy.

Otherwise, I still prefer using an all-Kevlar cord on BT-5 rockets like the Gnome because nothing else can survive multiple ejection charges burning through that tiny tube diameter. And no, I have had no problem with zippering at that size.
 
Mr. Boren:
I initially disagreed with your insistence on rubber shock cords, having become quite the fan of elastic and Kevlar, but I have to admit that recently I've come around to see your point. I inherited a bunch of rockets that were pre-built with their rubber shock cords. These were poorly built rockets and I've been flying them a lot just to use them up. While rubber cords will degrade over time and eventually disintegrate, I have found that they do a really good job of holding up to numerous launches in the short term, maybe even better than elastic. The most surprising difference however, is that it is SO MUCH EASIER to feed a rubber cord into the body tube than an elastic one. The rubber drops right down the tube while the elastic/Kevlar has to be wadded up and forced in like putting a cat in a pet carrier. This has made me rethink my building philosophy.

Otherwise, I still prefer using an all-Kevlar cord on BT-5 rockets like the Gnome because nothing else can survive multiple ejection charges burning through that tiny tube diameter. And no, I have had no problem with zippering at that size.
The rubber/polyester is a little stiffer and sits in the middle of the tube, but the rubber falls straight down into the furnace.
 
Good eye Marc. The space in the eye bolt is indeed filled with JB Weld to prevent the shock cord from snagging and wearing out prematurely, being cut or working itself loose.

Any speculation on why the hole in the center of the bulk head has slots worked into it?

Presumably to allow positive positioning of something that slips through in there? Small electronics? To hold a twist-lock component? You've got me interested.
 
Fine Job Brady, that really looks keen!
I don't launch in winds, my launch area is too small.
I've never had a zip on BT-20's or smaller, there just too light.
Super BB is (was) an upscale of BB, known for weather cocking.
When a rubber shock cord needs replaced, it's not easy to removed the folded mount.
My BT-60 and larger builds gets a loop of kevlar through centering ring ans wound around engine tube.
At the end of the loop, just below the top of the BT, I use a 3-way swivel, 2 elastic shock cords.
1 to the chute(s) the other to nose cone or payload section.
I'd guess around 80% of my zippers were on rubber shock cords in the BT-50 to 80 range.
The other 20% were my first use of kevlar where it extended pasted the air frame, until I learned better.
Hope this clears things up, if not, feel free to ask any questions.
 
Presumably to allow positive positioning of something that slips through in there? Small electronics? To hold a twist-lock component? You've got me interested.

Twist lock cap for adjustable nose weight?

You both have the knack of seeing things others don't.

The small tube can be packed with just the right amount of nose weight for what ever motor is used.

There is a smaller bulk head with a hole in it further up the nose cone to keep the weighted tube centered. The inside tip of the cone has foam rubber adhered to it which pushes back on the tube while it is twisted and locked into place.

The tabs on the end of the tube give the fingers something to hold on to while the pushing and twisting is going on. Any void left inside the tube after the weight is in place is filled with crushed paper and the end of the tube is taped off

IMG_1546.jpg

IMG_1547.jpg
 
If all Nose Cones were balsa, the Shoulder should be turned down to fit inside a Tube Coupler.
The reason I say this is simple, Help Stop Zippering.
Plastic nose cones can not be done to fit inside the BT coupler.
Balsa can be. And should come that way and each kit should have a High Density Coupler for anti zipper effect.
Over the 45 years I've launched LP rockets I've had numberous zippers...
I like the basic idea - smaller shoulders and reinforcement of the top of the body tube. As others have pointed out, one can turn down one's own balsa shoulders. (One used to be able to order custom machined cones as well, back when Balsa Machining Service was worthy of the name, but the last time I checked they were no longer taking custom orders. Is there someone else? I know I can get custom centering rings from PML, but I don't know about nose cones. But I digress.)

On the other hand, if one could convince manufacturers to supply nose cones like this standard (not likely) then there's no basic reason that it couldn't be done with plastic cones as well. Sure, you can't just turn down a plastic cone's shoulder as you can with balsa, but there's no reason they couldn't be made that way.

Mind you, there are reasons they won't be made that way, but no reason they couldn't.
 
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