Got a question

[Meteor Mike]

My previous experience with model rockets was with some of the easier Estes kits (nothing beyond skill level 2) for a brief period, around 1979-80. I didn't go too far with it so I'm not up to snuff on the history of these models. But I've seen some references recently to Estes K-kits. Can someone tell me what a K-kit is?

 

[troj]

My previous experience with model rockets was with some of the easier Estes kits (nothing beyond skill level 2) for a brief period, around 1979-80. I didn't go too far with it so I'm not up to snuff on the history of these models. But I've seen some references recently to Estes K-kits. Can someone tell me what a K-kit is?

Early on in their kit production, Estes identified their kits with K-series numbers. K-1, K-2, etc.

You can find a list of those here

-Kevin

 

[sandman]

The early Estes kits are listed at the top of this page'

https://www.spacemodeling.org/JimZ/estes.htm

K-1 Scout through K-59 SPEV.

Ask more questions, we really don't mind.

 

[Meteor Mike]

Ask more questions, we really don't mind.

Okay, here's another: Why do people replace the tube-mounted shock cord with a longer one attached to the upper ring of an engine mount tube? Doesn't that make repairs more difficult when the shock cord breaks? How do you get down in there to replace it?

 

[JAL3]

Okay, here's another: Why do people replace the tube-mounted shock cord with a longer one attached to the upper ring of an engine mount tube? Doesn't that make repairs more difficult when the shock cord breaks? How do you get down in there to replace it?

Typically, a different material is used for the replaced shock cord. Estes uses rubber bands that are too short and universally reviled. Many people, at the very lease, substitute sewing elastic.

When fastening to the motor mount, a length of Kevlar is generally included between the motor mount and the elastic. It does not strech and is flame resistant. Tying a new piece of elastic in should not be a problem.

While almost everyone hates teh Estes rubber bands, some people actually like the Estes style trifold mount. I do not. things slide out of the BT much easier without it. I use a piece of Kevlar tied to sewing elastic. The Kevlar extends almost to the top of the tube. I would like to use longer (there are ways) but anything longer tends to "zipper" the tube. For elastic, I use 3x the length of the rocket. I like the long recovery train and longer period pendulum.

 

[sandman]

Okay, here's another: Why do people replace the tube-mounted shock cord with a longer one attached to the upper ring of an engine mount tube? Doesn't that make repairs more difficult when the shock cord breaks? How do you get down in there to replace it?

The short shock cord seem to, sometimes...or most of the time...lead to the nose cone "bouncing" back and hitting the body tube.

A longer shock cord is supposed to reduce this.

As for the the attachment to the motor mount, some seem to think it's a stronger mounting point than the three fold paper mount on the inside of the tube.

I think its a matter of opinion. Open for argument.

Yes, it does make repairs difficult.

The usual repair is to...you guessed it...use a three fold paper shock cord mount.:eyeroll:

 

[hornet driver]

HMMM, The thought process is something like this---Replace rubber band with kevlar/or/and/elastic--possibly in combination---lasts longer and is more durable---given the life expectancy of the avaerage rocket--tends to be short---It's a good trade off and gives you the option of up motoring and expands your fudge factior a bit. The mmt tends to be the strongest part of the average rocket so it makes sense to put the shock cord in that area anyway. The mount and cord should outlast the life of the rocket.

 

[Meteor Mike]

Where do you get kevlar cord?

 

[DizWolf]

I buy it here for small ( A-D) rockets:
https://www.rocketarium.com/kevlarshockcord.html

I tie it around the motor tube, under the top centering ring and run it between the motor tube and centering ring. If you need to replace the shock cord, you can pull the kevlar out the back of the motor tube to tie in a new piece.

 

[n3tjm]

IMO the tube attach shock cord is the better way to go. I had way to many crashed rockets where something got caught in the kevlar/elastic cord knot. Use "Yellow" wood glue and the tube shock cord mounts usually outlast the rocket

 

[JAL3]

Where do you get kevlar cord?

You can find it from most rocketry sources: Fliskits, Semroc, Apogee, etc.

 

[powderburner]

You can also find Kevlar on ebay, on amazon, and other sources.

You might try running a few searches on old TRF posts for specific sources (don't forget to check the archives)

 

[jflis]

FlisKits carries Kevlar in several different sizes from 8 lbs (fine thread) to 150 lbs (fairly heavy duty, for model rocketry)

 

[goldlizard]

Back on March 24th 2013, in the Beginners & Educational Programs section, there is a thread called "What other options besides the tri-fold shock cord mount?". There are shown several ways to mount shock cords, using Kevlar and stainless steel fishing leaders. The latter is a method I have adopted, for around $6-7 I make my own leaders then attach the Kevlar and/or elastic to the leader.
Check it out and see if that thread will help you out.

Happy flying
James

 

[hcmbanjo]

Okay, here's another: Why do people replace the tube-mounted shock cord with a longer one attached to the upper ring of an engine mount tube? Doesn't that make repairs more difficult when the shock cord breaks? How do you get down in there to replace it?

I did an article on Replaceable Kevlar in a recent issue of the Apogee Peak of Flight Newsletter.
Check it out at:
https://www.apogeerockets.com/education/downloads/Newsletter338.pdf

It's simple, cheap and works!
You can replace the Kevlar loop and even check it's condition between flights.

 

[sodmeister]

Where do you get kevlar cord?

Me !

I have plenty I could give you FREE for all your Estes needs :wink:

If you need ,send me a PM (private message)

Cheers

Paul T

 

[Meteor Mike]

Thanks for all the info.

 

[luke strawwalker]

There's nothing particularly wrong with an Estes "tri-fold" or "teabag" shock cord mount... I use them frequently, though most of the time the Dr. Zooch rockets I mostly build have kevlar that ends up with a loop around the motor mount going through a notch I sand at the OUTER EDGE of the centering ring (near the tube wall-- I recommend routing the shock cord this way rather than sanding a notch for it on the INNER EDGE of the centering ring near the motor tube, which tends to expose the kevlar cord to a LOT more heat and abrasion from the motor ejection than having out near the body tube wall). To keep the cord in the notch while gluing the motor mount in the body tube, just drop the kevlar cord down through the motor tube itself and keep it pulled taut as you insert the motor mount in the rocket body tube... works like a champ!)

For Tri-fold mounts, I DO HIGHLY recommend jettisoning the stupid rubber band crap Estes puts in their kits, and instead use sewing elastic readily available in various widths cheap from WalMart... works great. When assembling the tri-fold, don't put the elastic straight up and down so it folds over itself-- put it at a slight angle so that it forms a "V" when the tri-fold is glued up. Use white or yellow wood glue, and then clamp the tri-fold up securely with clamps-- I use hemostat clamps which have had the serrated jaws sanded off so they're smooth-jawed, but any suitable assembly clamp should work. This will make a strong and very thin tri-fold mount. Let it dry overnight before gluing it into the rocket...

Before gluing it in, gently curve the tri-fold to the same curvature as the inside wall of the rocket body tube. Curving it between the thumb and two fingers will create a very flush, form-fitting tri-fold that will lay very flat against the tube wall. I always install it as far down the tube as I can reasonably get it. If the tube is too small to get your finger down into very far, use a good piece of dowel or other stick to insert the mount further down the tube.

Works for me! Good luck! OL JR

 

[Davidtmp]

I did an article on Replaceable Kevlar in a recent issue of the Apogee Peak of Flight Newsletter.

That's awesome!

 

[soxfan121]

I did an article on Replaceable Kevlar in a recent issue of the Apogee Peak of Flight Newsletter.
Check it out at:
https://www.apogeerockets.com/education/downloads/Newsletter338.pdf

It's simple, cheap and works!
You can replace the Kevlar loop and even check it's condition between flights.

View attachment 130774

o.o so many ideas that are fairly simple when you see them and think "why the heck couldn't i have thought of that..." Great idea!

 

[Rocketbuilder]

I did an article on Replaceable Kevlar in a recent issue of the Apogee Peak of Flight Newsletter.
Check it out at:
https://www.apogeerockets.com/education/downloads/Newsletter338.pdf

It's simple, cheap and works!
You can replace the Kevlar loop and even check it's condition between flights.

View attachment 130774

That is a good idea! I suppose it could be adapted to function as a backup motor-retention system as well-- I may try that, given the tendency of my motor cases to Houdini their way out of the motor mount.

 

[Meteor Mike]

How do you determine the strength (pounds) of the kevlar cord you should use?

 

[Zonie]

:headbang:

I did an article on Replaceable Kevlar in a recent issue of the Apogee Peak of Flight Newsletter.
Check it out at:
https://www.apogeerockets.com/education/downloads/Newsletter338.pdf

It's simple, cheap and works!
You can replace the Kevlar loop and even check it's condition between flights.

View attachment 130774

 

[powderburner]

Not trying to pick a fight, just want to present an alternate viewpoint--

There's nothing particularly wrong with an Estes "tri-fold" or "teabag" shock cord mount... I use them.....

The folded wad of material that the Estes-style system forms is not my idea of a good thing to have in the front end of a BT5, 20, or even 50 tube. After experiencing your own recovery system failure to deploy, due to a tightly packed chute or streamer snagging against that trifold wad, your opinion might change too. Even in a bigger BT size, these trifold anchors can cause problems. IMHO, it is just as easy to use a kevlar tether attached to the MMT which presents only a tiny obstruction in the deployment path.

I look for every reasonable way to improve the chances of getting a reliable flight and a safe recovery.

Even better, a recovery system tether can be run out the front of the rocket, against the nose cone shoulder, and back along the rocket's exterior to an anchor point near the c.g. of the remaining lower portion of the rocket. (This is the lower BT with expended motor but not including wadding, recovery items, or nose cone.) This way, the lower body of the rocket hangs sideways during descent and can also contribute to a reduced sink rate.

I always install it as far down the tube as I can reasonably get it. If the tube is too small to get your finger down into very far, use a good piece of dowel or other stick to insert the mount further down the tube.

Agreed. And if you're gonna do this, why not just use an anchor at the MMT? (as in, around a centering ring, or around the engine block).

As I said, just my two cents---

 

[luke strawwalker]

Not trying to pick a fight, just want to present an alternate viewpoint--



The folded wad of material that the Estes-style system forms is not my idea of a good thing to have in the front end of a BT5, 20, or even 50 tube. After experiencing your own recovery system failure to deploy, due to a tightly packed chute or streamer snagging against that trifold wad, your opinion might change too. Even in a bigger BT size, these trifold anchors can cause problems. IMHO, it is just as easy to use a kevlar tether attached to the MMT which presents only a tiny obstruction in the deployment path.

I look for every reasonable way to improve the chances of getting a reliable flight and a safe recovery.

Even better, a recovery system tether can be run out the front of the rocket, against the nose cone shoulder, and back along the rocket's exterior to an anchor point near the c.g. of the remaining lower portion of the rocket. (This is the lower BT with expended motor but not including wadding, recovery items, or nose cone.) This way, the lower body of the rocket hangs sideways during descent and can also contribute to a reduced sink rate.



Agreed. And if you're gonna do this, why not just use an anchor at the MMT? (as in, around a centering ring, or around the engine block).

As I said, just my two cents---

Well, you certainly CAN do either one... the results depend on doing it RIGHT...

If you make a "wad" out of the Estes tri-fold and slobber it all up against the wall near the nosecone shoulder so it sticks out like a wart, I'm sure you WILL have lots of problems...

IF, on the other hand, you use the method I described to make them thin and form-fitting to the tube wall, and place them BELOW where the chute/streamer will be sitting (note I said "as far down the tube as possible", BUT putting them TOO far down the tube, TOO close to the motor mount, also exposes the shock cord to a lot of heat and potential damage from ejection debris and heat, which is not a good thing... best to have it BELOW where the chute needs to be, but not much farther than that... guess I should have clarified). If it's form-fitting and smooth, and your chute/streamer is wrapped tight enough to fit the tube easily (which is necessary for reliable ejection from the tube anyway) then a tri-fold will work and work reliably.

Basically it comes down to whatever you want to use. I know some folks loathe tri-folds and seem to demonize them at every turn. Personally I've never had a problem with them, but maybe I make them neater than folks who hate them-- I dunno. Personally I'm not a HUGE fan of kevlar to the motor mount, either... I've done it and it works, its okay, BUT two things to remember are that kevlar is NOT heat, abrasion or flamePROOF-- it's heat, abrasion, and flame RESISTANT... given enough time and exposure, it WILL break down. I don't like the fact that kevlar doesn't like to take and hold a knot, and that its abrasive and cuts tubing easily. When a loop round the motor mount kevlar shock cord eventually wears through, breaks, or frays beyond reliability from motor ejection blasts, repair is difficult or impossible (except to revert to an "Estes Teabag"...) The best way to ensure the longest lifetime from the kevlar is to notch the OUTER edge of the centering ring that will be glued next to the tube wall, and run the kevlar through that notch and down through the center motor tube while the motor mount is being glued into the rocket-- keep the kevlar as far from the ejection charge tube end and all that blast particulates and heat as possible...

Not trying to pick a fight with you either, but honestly I hear people talk about kevlar loops round the motor tube as some sort of miracle method, and while it's a good method, it's not perfect... it has its share of problems...

Probably the best idea is to leave it up to the individual builder and their choice... and not demonize EITHER method, because clearly they BOTH work... in fact, given history, I'd bet 10X the number of rockets have flown and recovered just fine using the tri-fold method versus the kevlar loop over the motor tube method, simply because the tri-fold has been around SO much longer!

IOW they both work, both have good points, and both have drawbacks...

Let the reader decide for themselves...

Later! OL JR