Quantcast

Estes Big Daddy and its Parachute

The Rocketry Forum

Help Support The Rocketry Forum:

Sartori42

Member
Joined
Mar 22, 2009
Messages
20
Reaction score
0
I now have 4 or 5 launches of my Big Daddy behind me now, and I have a question about the best way to insert and protect its parachute.

The space between the bottom of the NC and the top of the upper centering ring is just under 3". Advice on this forum is to pack dog barf equal to the diameter of the BT. Obviously, that doesn't leave much space for a parachute. To compound that problem, the parachute is a big 24" chute. Obviously, the chute has to lay sideways on top of the wadding (now less than the BT diameter). To get it small enough to fit sideways, I've been folding it into quarters before I wrap the lines around it. I haven't had any problems with this yet, but wondered if anyone had a better way to prep the chute?

Thanks.

Steven
 

Daddyisabar

Oddrocs Rule!
TRF Supporter
Joined
Jan 23, 2009
Messages
4,591
Reaction score
198
Location
Littleton Colorado
I’m sure one of the more experienced rocketeers will be able to explain this better but on my Big D I place the shroud lines about half way up the folded in chute and then fold the chute lengthwise in half. The remaining shroud line then wraps around two to three times. Pack a sheet of wadding in the little remaining engine tube above the E motor, then a good layer of dog barf around the entire diameter and shock cord, then a few more sheets below and around your chute. Use plenty of talc to keep the chute from sticking together. There isn’t much space but gently pack it down a little bit with the nose cone. If you get a little too much dog barf and have a slight gap on the nosecone fitting all the way down you are ok as long as the nosecone is not loose – it has a big shoulder. If you built it with the stock shock cord like I did on my first Big D you will get about 9-10 flights before it breaks at the motor mount – even with packing dog barf around it. Soft rubber and black powder ejection charges don’t mix. Always check the cord and when it is nice and black – as it is after 5 launches, just get a yard of underwear elastic with a high polyester content, make a nice big trifold mount, clean the tube, glue it in, pack it down and your ready for another 30+ flights. The Big D is a strong LPR rocket. Mine went to 28 launches until I experienced my first motor where the ejection charge failed. It core sampled half way up the nose cone. I pulled it out, reinforced the crimped spirals in the tube with some CA and flew it again. With a beautiful sharpie marker coating over the chipped paint it has now flown 35 times. The scotch tape is building up on the numerous small pinhole burns on the plastic chute, the shroud lines have all been replaced.
 
Last edited:

powderburner

Well-Known Member
Joined
Jan 18, 2009
Messages
7,401
Reaction score
4
I posted this back in the "olden days" of TRF1, but thought you might be able to use the info now instead of waiting for the old threads to be made available again.

I made this mod on a Fat Boy to get around the same problem. As shown in the attachment, I cut off the tapered part of the NC base and converted the NC itself to become the parachute compartment. I closed off this new 'chute bay with a full-diameter solid disc across the bottom of the NC, near the front end of the BT. This keeps the ejection gases completely away from the recovery gear and does not use any wadding, barf, or protective bags. Click on the tabs from left to right to see how to build this feature. The example in the EXCEL spreadsheet was adapted to PNC60 (like the Baby Bertha) but I think you will get the idea how to work this on larger NCs.

You will have to use something flame-resistant (like Kevlar) for the anchor system, as those parts are still exposed to the hot ejection gases.

I hope this info is useful to you.

View attachment NCmods.xls
 
Last edited:

Sartori42

Member
Joined
Mar 22, 2009
Messages
20
Reaction score
0
powderburner,

Man, that has me thinking! Great suggestion! I think I'll try cutting a circle in the bottom of the NC to fit a body tube up into the NC. It only has to be big enough to fit the parachute up into the NC. Hmmmm...

:)

Thanks.

Steven
 

hardinlw

Well-Known Member
Joined
Jan 19, 2009
Messages
372
Reaction score
1
Another option would be to use a Nomex chute protector and eliminate the dog barf. What I've started doing lately is to mount some 1/8" diameter tubular kevlar to the motor mount tube and tie a loop in it several inches above the edge of the airframe. 1/8" is way bigger than you need to carry the shock loads. I went that big so it would not cut (zipper) the body tube in the event of a late ejection. I thread that through the hole in the chute protector and then tie the rest of the recovery system (shock cord, chute, etc.) to the loop. That way, your shock cord is also protected. It doesn't matter how well you protect the parachute if the shock cord gets burned in two.
 

Sartori42

Member
Joined
Mar 22, 2009
Messages
20
Reaction score
0
Larry,

Thanks for the response. I played around with the rocket last night and decided against cutting into the nose cone to create a parachute compartment. I have a few nomex parachute protectors, but I'm hesitant to use them. I tried last night and was able to make a nice cup with the nomex protector at the top of the open BT. Then, rather than folding the parachute, I rolled it and wrapped the shroud lines around it. I like that configuration better. Now, I'm going to put the parachute into the cup of the nomex protector and push it down into the BT. I'm concerned that there's only one layer of nomex between the deployment charge and the plastic parachute, so I think I'm going to stuff a single sheet of Estes wadding up the engine tube before I insert the engine. I hope that will make everything safe. Now, I just have to hope for good weather this weekend....

Also, I had constructed the 3 rockets in my "fleet" before I learned about modifying the stock designs. Since the CINC-House doesn't see a need for more rockets, I'm thinking one of my rockets may need to CAT-O (accidentally, of course) so I can get a new one and modify it better.... :)

Cheers.

Steven
 
Last edited:

judo

Well-Known Member
Joined
Jan 18, 2009
Messages
2,347
Reaction score
4
I used Powderburner's idea on all of my Fat Boys. I'm trying to engineer something along the same lines for a 4" scratch stubby.
 

Larry Curcio

Well-Known Member
Joined
Mar 5, 2009
Messages
538
Reaction score
0
Off-topic, here, but is Estes catering to BARs with a name like Big Daddy? That's slang from... like... the Beat Generation. It's actually pre-hippy!

Unless they're going for the Tennessee Williams set - which is from pretty much the same time, though it's still around.


Dig Ya Later, Cats,
-Larry Mangiacavallo
 

m85476585

Well-Known Member
Joined
Jan 18, 2009
Messages
2,664
Reaction score
1
I posted this back in the "olden days" of TRF1, but thought you might be able to use the info now instead of waiting for the old threads to be made available again.

I made this mod on a Fat Boy to get around the same problem. As shown in the attachment, I cut off the tapered part of the NC base and converted the NC itself to become the parachute compartment. I closed off this new 'chute bay with a full-diameter solid disc across the bottom of the NC, near the front end of the BT. This keeps the ejection gases completely away from the recovery gear and does not use any wadding, barf, or protective bags. Click on the tabs from left to right to see how to build this feature. The example in the EXCEL spreadsheet was adapted to PNC60 (like the Baby Bertha) but I think you will get the idea how to work this on larger NCs.

You will have to use something flame-resistant (like Kevlar) for the anchor system, as those parts are still exposed to the hot ejection gases.

I hope this info is useful to you.
That's exactly what I did, and it works great. In fact, I probably got the idea from you on TRF 1.0 To secure the shock cord, I used a short piece of Kevlar attached to the tip of the NC with Gorilla Glue, then I tied the shock cord to that.
 

Sartori42

Member
Joined
Mar 22, 2009
Messages
20
Reaction score
0
OK, we got in a few launches this weekend. My first launch of my Big Daddy had a nomex parachute protector wrapped around the parachute and shock cords. It did protect the parachute, but it seemed to cause a different problem. When the deployment charge went off, blowing everything out of the BT, I think the nomex protector got mixed up with the parachute lines. It seemed to take a long time before the parachute inflated. For a few seconds, it seemed like the parachute wouldn't inflate, but it finally did.

On my Big Daddy, I have a loop in the shock cord and 2/3 of the way from the BT to the NC. I hook the parachute to that loop using a no.5 swivel snap. I also tied the nomex parachute protector on a short length of shock cord and attached it to the loop using another swivel snap. I know they say to run the main shock cord thru the "button hole" on the nomex protector, but I thought my plan would be better. Now, I'm not so sure.

Does anyone else have any issues with nomex parachute protectors getting "involved" with the parachute deployment? If you don't have any problems, how do you connect the parachute protector to the rocket?

Cheers.

Steven
 

hardinlw

Well-Known Member
Joined
Jan 19, 2009
Messages
372
Reaction score
1
The TARC team I have been mentoring ended up wrapping the upper and lower sections of the shock cord around a hand to make a neat little bundle. The chute protector was installed with the shock cord through the buttonhole as recommended and was slid down to the top of the rocket leaving very little shock cord loose in the rocket. (They had a bad experience with the shock cord looping over the chute protector and keeping it in the end of the airframe. The rocket separated, but the chute did not open. It fell on its side from 800 feet and the egg survived. Talk about some good packing!) Most of the time, the chute opens instantly. There have been a couple of times that it took a while for it to open and I suspect that the nomex was folded around the chute. That's something they are going to work on prior to the finals. If you think about it, the chute wrapped in the protector can come out of the airframe, but if the slipstream holds the protector wrapped around the chute, it will not be subjected to the aerodynamic forces that would make it open. Somehow you need to make the chute come out of the protector. With larger rockets using deployment bags, a small drogue can do this or you can use the momentum of the nose cone to pull everything apart.
 

Sartori42

Member
Joined
Mar 22, 2009
Messages
20
Reaction score
0
Larry,

Thanks for the reply. I had considered the parachute getting stuck in the nomex protector, which is why I put it on its own shock cord. I kinda wanted to "disassociate" the two parts (parachute and protector) at altitude, but I'm not sure I succeeded in that. I got the impression that the nomex protector was "flapping about" in the airstream and may have caused a slow parachute deployment. However, it could have been any of a number of other factors (wind, engine, parachute packing, etc). Hopefully, someone else will chime in with how they pack their chute and nomex protector and if they have any issues. Thanks again.

Cheers.

Steven
 

RangerStl

Well-Known Member
Joined
Jan 17, 2009
Messages
1,086
Reaction score
1
Larry,

Thanks for the reply. I had considered the parachute getting stuck in the nomex protector, which is why I put it on its own shock cord. I kinda wanted to "disassociate" the two parts (parachute and protector) at altitude, but I'm not sure I succeeded in that. I got the impression that the nomex protector was "flapping about" in the airstream and may have caused a slow parachute deployment. However, it could have been any of a number of other factors (wind, engine, parachute packing, etc). Hopefully, someone else will chime in with how they pack their chute and nomex protector and if they have any issues. Thanks again.

Cheers.

Steven
I have had the chute fail to unfurl at all once and unfurl at 50 feet another time even with no chute protector. Looked like the chute ball got in the turbulent wake of that big rocket coming down and never saw air fast enough to pull it open. Since that time I've just draped the shroud lines loosely on top of the chute rather than wrapping them aroung the folded chute. I use one or 2 sheets of wadding in the tube set in like a barrier and then put a layer of barf on top of that. Usually the nose cone is sitting on top of the wad of stuff.

N
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,730
Reaction score
324
Location
Stafford, VA
I've always attached the chute protector near the BT and the chute near the nose cone. As long as you have sufficient ejection charge, the nose cone will pull the chute away from the chute protector. I also lay the chute shroud lines inside the various folds of the chute and wrap the protector around the chute instead of shrould lines. Haven't had issue with chute and protector.
 

Sartori42

Member
Joined
Mar 22, 2009
Messages
20
Reaction score
0
Handleman,

Thanks everyone for your replies. I agree with the idea of the protector near the BT and the parachute near the NC. However, being a newbie, I built the Big Daddy exactly according to the Estes instructions, using the supplied parts. That means the supplied rubber shock cord attached with the standard trifold paper inserted into the BT. The 12" square protector is big enough to affect the parachute if I put it anywhere along the line. However, if I tie another length of shock cord to the stock one, maybe I can get more separation between the BT and the NC. Are there any guidelines as to how long shock cords should be? Thanks.

Cheers.

Steven
 

powderburner

Well-Known Member
Joined
Jan 18, 2009
Messages
7,401
Reaction score
4
I built the Big Daddy exactly according to the Estes instructions, using the supplied parts.
Steven, I was thinking about this again, and the reports by some of these other guys about deployed chutes not opening well, and I started wondering about your shock cord length. I guess great minds think alike?

The first thing I would do is toss the Estes shock cord. My apologies to Penrose, but the provided cords are just too short.

You need one that is significantly longer---some guys here on TRF recommend using a shock cord that is three times the rocket's length (for low-power rockets). I suppose it wouldn't hurt to use four, or five times the length, but you begin to get different deployment problems where the shock cord stays in a bundle and pulls into a tight wad (instead of spreading out to full length) after ejection. Maybe there are tricks to attaining a "tidy" and complete extension of the full length of the shock cord, like maybe some secret techniques used by parachute packers?

Anyway, a short shock cord (as is often provided for many kits) runs the risk of having the NC pull the shock cord out to full extension (after ejection) and then snapping back to whack (and dent) the rocket. In fact, the "Estes dent" is a fairly famous type of damage that many people have had happen because of short shock cords, and it is soooo easy to avoid.

And, with stubby rockets, a parachute held close to the rocket easily not get much "clean" air to help with full opening of the chute.

I like to use a strong heat-resistant cord that anchors to the rocket and reaches six to twelve inches (or longer) outside the rocket. This is the main tether part that is exposed to the hot ejection gas. I use Kevlar if I have it available. I have also used heavy cotton and nylon cord but soak and coat those materials with white or yellow glue to improve their resistance to flash flames. I look for a tether with enough tensile strength to stand up to 20 pounds or so of pull, more if my low-power rocket is a big & heavy one.

I tie the end of the main tether in a small loop at the loose end. This lets me tie on any additional length of non-stretching tether that I might want to use, or I can tied on some stretchable elastic band to absorb some of the "shock" of the NC yanking on the other end of the line. I use a length of stretchable shock cord that is about as long as the rocket, maybe longer. The material is the 1/4 inch wide elastic band that comes in six foot lengths for around a buck; you can find it in the sewing department of many stores. (They also sell wider elastic band material that you can use for heavier rockets.) This arrangement lets you pack the stretchable part of the shock cord up ahead of the ejection wadding and keeps it away from the hot ejection gas.

Some folks like the stretchy "rubber band"-type material that comes with many kits. That's fine, I just recommend that you keep a close watch on the stuff. I have found that once this rubbery material develops a nick on one edge, it can easily tear all the way through the entire width. It seems to toughen and dry out after long storage, or after many ejections, faster than the elastic-band material (IMHO).

For low-power rockets, I don't like making the entire length of the shock cord from non-stretchable material. I like to have roughly half-n-half up to where the parachute (or streamer) attaches, and maybe even another short piece of tether material on out to the NC.

All parts of the shock cord system (anchors, tethers, stretchable cord, knots, swivels, clips, etc.), regardless of materials used, need to be inspected frequently and repaired when you see damage (fraying, roasting, stiffening, etc).

As far as guidelines on how long to make the whole shock cord (for low power rockets), as far as I can see, the "three times the length of the rocket" rule of thumb seems to work. You would probably be OK at two times, or four times, but it's not all that important. What is important is to watch out for shorty cords provided with many kits--and replace them!

Sorry if this response was overkill, but I wasn't sure what sort of answer you needed. I hope some part of all that is useful to you
 
Last edited:

Sartori42

Member
Joined
Mar 22, 2009
Messages
20
Reaction score
0
Powderburner,

"The first thing I would do is toss the Estes shock cord."

I understand the desire to do this, but I'm not sure how to accomplish it. When I glued the trifold anchor for the rubber shock cord, I secured it WELL. I suppose I could easily cut off the shock cord and leave the mounting in the BT, but how to secure a new shock cord system? While I like the 3" diameter of the BT, I don't think I can get in there and insert some sort of anchor to the top engine mount centering disc. When I built my Quest Harpoon, it had me tie a kevlar string around the engine tube and then up the BT. That's a pretty secure system in my estimation. I have some kevlar cord, but don't know how I'd securely mount it inside the BT of the Big Daddy now that the rocket is complete. I'm open to any ideas.

Thanks everyone.

Cheers.

Steven
 

DM1975

Upscalien
TRF Supporter
Joined
Mar 11, 2009
Messages
1,752
Reaction score
161
Location
Kansas
If all else fails you could just cut the old one off and use another piece of card stock or paper to make another trifold mount and just glue it and the new shock cord in another location, like maybe 180 degrees from the old one. I have done this a couple different times and it works fine.
 

Trident

Retired, plenty of kits
Joined
Jan 18, 2009
Messages
861
Reaction score
9
I now have 4 or 5 launches of my Big Daddy behind me now, and I have a question about the best way to insert and protect its parachute.
[...]

Thanks.

Steven
I have taken a different approach a few times when there is not much length in the chute compartment, but you have decent tube diameter:

Extend the motor tube up to the base of the nose cone. Then, pack your chute around this stuffer tube. No wadding needed - the gases hit the bottom of the nose cone, and the nose cone will pull the chute out. If in doubt, add a little nose weight to make sure there is plenty of mass in that nose cone that will help pull the chute out.

This is easier to do during initial assembly, but I have done this after the rocket was built, using a coupler and another piece of motor tubing to make the extended stuffer tube.
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,730
Reaction score
324
Location
Stafford, VA
I use the ribbon sewing trim you find at Walmart. It comes on a 5 yard spool, about 3/16" wide, made of cloth, lots of colors and costs about $0.49 a spool IIRC. I use 6 - 8 feet for small Estes rockets and 10 - 12 if the nose cone is a little heavier it's a zipperless design.

I attach it with the same tri-fold method used with the elastic shock cords.

No more "Estes dents" or broken elastic and my shock cords are color coordinated.
 

Sartori42

Member
Joined
Mar 22, 2009
Messages
20
Reaction score
0
Some interesting responses....

I kinda had it in my head that the trifold attachment of shock cords was frowned upon. I don't know where I got that idea, maybe within my own head, but there it is. I like the kevlar line, elastic cord system used in my Quest Harpoon. Seems more "elegant" to my mind.

Also, I looked at the inside surface of the Big Daddy BT. It's pretty discolored from ejection charges. Will this soot interfere with the attachment of another trifold anchor? I assume since others have done it, it must work. Are there preparations to be made?

Finally, I had thought of a different possibility. What if I drilled a small hole in the top centering ring, just big enough to fit a kevlar cord thru it. Then, drilled another small hole in the external (bottom) centering ring. I think I could run a thin stiff wire thru the 2 holes and pull the kevlar back thru the two holes. Then attach a small anchor (washer?) and glue it to the bottom centering disc. I little drop of glue should seal the holes around the kevlar string. Make sense to anyone?

Thanks for all your inputs. It's nice to have a variety of inputs...

Cheers.

Steven
 

novikov

Member
Joined
Apr 12, 2009
Messages
8
Reaction score
0
Last weekend I put my Big Daddy up three times. when I was assembling it I spaced getting the shock cord strung through the centering ring like the instructions said... My solution was to create a baffle system out of 1/8 inch panelling and coat the two pieces in epoxy. once that was dry Isecured the two together with a small gap (1/8 inch) between then put a bit of steel wool in and glued the baffle into the tube just off of (again about 1/8 inch) the motor tube. With that secured I attached the shockcord to an eye screw then screwed that into the upper layer of the baffle. Launched on a D12-3 (to make sure it wouldn't hit the clouds) and two E9-6s looks like maybe a bit of scorching on the very end of the shock cord. I am thinking about replacing it with a good length of kevlar cord and just using that instead. The chute had no issues at all. One flight the thing canted into the wind about 100 feet up and i had a bit of a walk, but other than that it was a great set of flights.

This was my first baffle attempt and so far I am quite liking it. I am planning to see about doing baffles in more of my rockets and probably see about retroing them into some of my older ones.



Jed
 

Handeman

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
7,730
Reaction score
324
Location
Stafford, VA
Last weekend I put my Big Daddy up three times. when I was assembling it I spaced getting the shock cord strung through the centering ring like the instructions said... My solution was to create a baffle system out of 1/8 inch panelling and coat the two pieces in epoxy. once that was dry Isecured the two together with a small gap (1/8 inch) between then put a bit of steel wool in and glued the baffle into the tube just off of (again about 1/8 inch) the motor tube. With that secured I attached the shockcord to an eye screw then screwed that into the upper layer of the baffle. Launched on a D12-3 (to make sure it wouldn't hit the clouds) and two E9-6s looks like maybe a bit of scorching on the very end of the shock cord. I am thinking about replacing it with a good length of kevlar cord and just using that instead. The chute had no issues at all. One flight the thing canted into the wind about 100 feet up and i had a bit of a walk, but other than that it was a great set of flights.

This was my first baffle attempt and so far I am quite liking it. I am planning to see about doing baffles in more of my rockets and probably see about retroing them into some of my older ones.



Jed
Interesting baffle system. I think over time you will find several things out about baffles.
  • They tend to last longer the further they are from the motors.
  • Stainless steel scrubbers work well for filling them, but even that will degrade after time.
  • Baffles that prevent burning particles from passing by changing the path of the gas seem to last the longest.
  • Baffles with restrictive paths or clogged filler require better motor retention and sometime even stronger body tubes.
  • Steel wool is actually flammable. Put at match to a small piece sometime.

I think using baffles is really a personal choice. Some people love them, others don't. Some designs work better, some longer, some better for longer, but as long as the chute doesn't burn/melt and it deploys right, it's all good.
 

novikov

Member
Joined
Apr 12, 2009
Messages
8
Reaction score
0
Yeah I know there are various problems with it and I fully expect the whole thing to go up in flames at some point... but it is working amazingly well for a first baffle attempt that was done in two days just so I could see how it worked.

There were a couple of other issues I ran into with the standard assembly instructions that I plan to see about doing another one some time and try to do them differently. Mainly the forward centering ring isn't up against the fins, and the instructions tell you to make sure the fins are seated at the back all the way... quarter inch gap at the pressure end of things seems like a bad game plan to me. And that would give me a chance to try some other wadding free solutions on the ejection system (maybe a piston ejection?) Still pondering various options.


Thanks for the input about the baffles though. I will definately keep that stuff in mind in the future.

Jed
 

DM1975

Upscalien
TRF Supporter
Joined
Mar 11, 2009
Messages
1,752
Reaction score
161
Location
Kansas
Extend the motor tube up to the base of the nose cone. Then, pack your chute around this stuffer tube. No wadding needed - the gases hit the bottom of the nose cone, and the nose cone will pull the chute out. If in doubt, add a little nose weight to make sure there is plenty of mass in that nose cone that will help pull the chute out.
This is what I have done with mine, along with making it a 29mm motor mount.
 

Mike Di Venti

Well-Known Member
Joined
Feb 17, 2009
Messages
404
Reaction score
1
Satori42,
There are a lot of great ideas here.
Here's one more. :) :
In mine, I have a small 3"x3" nomex that I stuff down the motor tube, put a little dog barf on top and then fold my nylon chute a lay it on top.
now, i also use 1/8" kevlar when I built mine and it's like 4ft long. I zig zag it back an forth and tape the ends so it doesn't tangle on deployment.
The nomex piece is tied to a loop a couple of inches from the top of motor tube so it's not going to travel up the shock cord and foul my chute.

My fat boy had about 30 or flights on it from c6-5 to AT F35-8.
She burned up last wknd do to a AT cato.
so, back to the building table.


good luck
 

GlennW

Well-Known Member
Joined
Feb 17, 2009
Messages
686
Reaction score
1
Some interesting responses....

Also, I looked at the inside surface of the Big Daddy BT. It's pretty discolored from ejection charges. Will this soot interfere with the attachment of another trifold anchor? I assume since others have done it, it must work. Are there preparations to be made?

Steven
It does get very sooty so for better adhesion take a very slightly damp rag or paper towel and just wipe the soot off the area where you'll put the mount. Not too damp though remember it is still cardboard and you don't want to soak it, just enough to get the soot off. This is what I did with my Big Daddy and the mount is in there good now with just Elmers white glue. You don't need anything fancy with this rocket.

Glenn
 

TheRocketNerd

Well-Known Member
Joined
Feb 28, 2009
Messages
108
Reaction score
0
Powderburner,

"The first thing I would do is toss the Estes shock cord."

I understand the desire to do this, but I'm not sure how to accomplish it. When I glued the trifold anchor for the rubber shock cord, I secured it WELL. I suppose I could easily cut off the shock cord and leave the mounting in the BT, but how to secure a new shock cord system? While I like the 3" diameter of the BT, I don't think I can get in there and insert some sort of anchor to the top engine mount centering disc. When I built my Quest Harpoon, it had me tie a kevlar string around the engine tube and then up the BT. That's a pretty secure system in my estimation. I have some kevlar cord, but don't know how I'd securely mount it inside the BT of the Big Daddy now that the rocket is complete. I'm open to any ideas.

Thanks everyone.

Cheers.

Steven
I've done this on several models and works great. Please see my attachment below for a diagram; keep in mind this is the "front view". I take a small rectangle of cardboard and poke two holes in it that are just big enough to pass the kevlar through. THen I knot the kevlar several times so that I have a large knot on the end. I then leave the knot about a 1/4 inch from the bottom hole (see picture) after I weave it through the two holes as shown. Then I place dabs of quick setting epoxy where the kevlar goes through the holes. Place some epoxy on the back of this whole thing when you are done and stick it to the inside of the body tube after you tie a loop in the kevlar. I like to keep the kevlar below the top of the body tube as the elastic replacement (that is always at least 6' long for me) is wider than the kevlar and so won't zipper if the ejection charge is early or late.

Specifically for the BD I like to use a 7x7 or so square of Nome with a slit in the very corner. I attach a snap swivel to the corner of it and a loop in the shock cord. Pack my chute normally and then place it on the nomex so that the sides just wrap around it loosely and you're ready to go! I should mention I used a ripstop nylon chute as well. Good luck. I hope this explanation is clear because it sure works well!

kevlar attachment.jpg
 

TheAviator

Well-Known Member
Joined
Jan 18, 2009
Messages
830
Reaction score
16
Maybe there are tricks to attaining a "tidy" and complete extension of the full length of the shock cord, like maybe some secret techniques used by parachute packers?
Yes, there are some tricks for complete shock cord extension. If you've ever been sailing, one of the first things you are taught is how to "fake" a line. I use this for any kind of string/line/cord/etc. including power cords and such to keep them from tangling.

The general technique is to make the cord do a figure-eight over itself, so it naturally unrolls one layer at a time. For rockets, I use two fingers, and wrap the figure-eight with the cross between my fingers. As long as you pull it off your fingers without twisting the layers together too much, it will unroll much neater than just stuffing it in the tube. This also works with the shroud lines, as long as you don't wrap the parachute in the lines. Then the general order of packing is:

1.) Shock cord (Both the part above and below the parachute attachment point)
2.) Shroud Lines
3.) Parachute
4.) Nose Cone

By packing in that order, you ensure that the line comes out straight, and the parachute doesn't get tangled it its own lines or the shock cord. With a larger rocket such as the Big Daddy or Fat Boy where the shock cord is isn't such a big deal, but it still helps to pack in that order.

One last tip: all Estes motors have at least a small recess in the top. Stuff a half sheet of wadding down into the top of the motor.
 
Top