Estes Goblin - that fragile loop on the nose cone

[Jimmy D. Jones]

I'm building an Estes Goblin and the hardest thing so far has been clearing out the extra plastic in that tiny loop in the nose cone where the shock cord is supposed to attach.

Gently scratched with the tip of a new exacto blade till I got the xtra material out. What's left is a very thin fragile loop. I can see it busting when the charge goes off and the nose cone coming separated.

Anyone got some suggestions for how to build up or otherwise make that loop stronger?

I was thinking of just drilling two holes in the conical part of the shoulder and passing the shock cord thru there. The cord would be a little shorter, but at least it would stay attached to the nose cone.

This may be an issue with many Estes nose cones these days, not sure. Back in the 1970's, the nose cones on my rockets were the old style balsa ones w/ the eyelet screw. No issue there.

Am I worried about nothing? Maybe I am thinking about this too much.

Thanks in advance!

 

[Tractionengines]

I was thinking of just drilling two holes in the conical part of the shoulder and passing the shock cord thru there. The cord would be a little shorter, but at least it would stay attached to the nose cone.

THIS. But use a small loop of kevlar thread. Then tie onto that.

 

[rharshberger]

THIS. But use a small loop of kevlar thread. Then tie onto that.

Exactly! Use the loop only if you like to lose nosecones.

 

[dhbarr]

THIS. But use a small loop of kevlar thread. Then tie onto that.

I didn't have any spare Kevlar when putting my L2 together so I drilled two holes, sent two of my heaviest zip ties through, and hung a quicklink off of that.

( admittedly I probably should have spent more than a couple hours the night before Airfest working on my L2 )

 

[dr wogz]

Second that (or third? fourth) to the two holes in the bottom of the NC.. Not an uncommon thing to do when you get into larger rockets with heavier nose cones

 

[bjphoenix]

I'm building an Estes Goblin and the hardest thing so far has been clearing out the extra plastic in that tiny loop in the nose cone where the shock cord is supposed to attach.

I've seen older nose cones with a tiny circular loop that barely touches the nose cone. Most of my newer ones have a larger rod that is connected to the nose cone to form kind of an L shape. I've never had any problems with these, and I'm talking about the very lightweight Estes type nose cones. If you use a long enough elastic shock cord or even longer kevlar then there shouldn't be much load on the nose cone loop. I think it would be even stronger if you drilled 2 holes in the bottom of the nose cone and passed a kevlar loop through it, or even a wire loop like a piece of paper clip.

 

[OverTheTop]

I am currently working on a Der Big Red Max and had the same issue. I used a hollow-wall anchor in the hole. Seems to work well.

I will need to fabricate an eye bolt to suit.

If you are going to try this make sure you use the anchors for thin wall panels, not the thicker drywall versions.

 

[Philip Tiberius D.]

Cut the bottom 1/4 - 1/8 inch off of the nose cone and use a piece of 220 grit sandpaper on the end of a dowel and scuff up the interior of the nose cone on the inside at the tip. Take a piece of Kevlar rated for 100 to 300 lbs and tie it to a # 8 or # 10 washer. Pour 5 - 6 oz of 5 or 20 minute epoxy into the nose cone and push the washer with the attached cord into the tip. Allow it to rest “pointy side down - with the washer / Kevlar rig until cured. Now you have a set anchor with an extra 3 - 4 inches of space in your rocket.

 

[hobie1dog]

I am currently working on a Der Big Red Max and had the same issue. I used a hollow-wall anchor in the hole. Seems to work well.
View attachment 507904
I will need to fabricate an eye bolt to suit.

If you are going to try this make sure you use the anchors for thin wall panels, not the thicker drywall versions.

excellent idea

 

[bjphoenix]

View attachment 507904

I think the factory loop on that nose cone is probably stronger than it looks. Not that it couldn't be broken and not that an occasional launch won't subject it to higher than normal forces in which case your idea would be good for strengthening. You can probably buy an eye bolt with proper threads to fit that insert. Or you can just bolt on a big washer or a couple of loops of chain using the bolt that is already in the washer. That's a pretty big diameter nose cone so you could put in 2 of those inserts and fashion a bent piece of metal with 2 holes in it to go between inserts.

Some people have complained about the angled surface on the side of that nose cone allowing the ejection charge pressure to escape before the nose cone is fully popped off allowing the rocket to lawn dart. I've seen this discussed more related to the Big Daddy. I cut the base off of mine right where the angled surface starts then I roughened up the inside and fashioned an aircraft plywood bulkhead that would fit. I drilled 2 holes in the plywood and made a wire loop to go through the holes out of coathanger wire, twisted together up inside the nose cone then used epoxy to glue the bulkhead in place. The inside diameter of the nose cone increases slightly above the shoulder so I made the bulkhead to be a tight fit up there so there is some mechanical lock to keep it from coming out. Turn it sideways, push up into the nose cone then rotate it to the intended position and let the epoxy cure.

 

[OverTheTop]

The inside diameter of the nose cone increases slightly above the shoulder so I made the bulkhead to be a tight fit up there so there is some mechanical lock to keep it from coming out. Turn it sideways, push up into the nose cone then rotate it to the intended position and let the epoxy cure.

I have used that method too.

 

[Jimmy D. Jones]

I decided to go with the drill two holes and make a loop out of kevlar thread.

I had some kevlar thread but have never used it for anything before. Every time I try to make a knot in it, it slips undone.

Any suggestions on a knot for kevlar thread that doesn't come apart easily?

I have seen some suggestions on these boards for kevlar knots, but they were for making a loop in the middle of a line of kevlar. What I'm trying to do here is take a length of thread and make a loop out of the entire length, by tieing the ends together.

Suggestions are welcome.

As always thinks in advance.

 

[dhbarr]

I decided to go with the drill two holes and make a loop out of kevlar thread.

I had some kevlar thread but have never used it for anything before. Every time I try to make a knot in it, it slips undone.

Any suggestions on a knot for kevlar thread that doesn't come apart easily?

I have seen some suggestions on these boards for kevlar knots, but they were for making a loop in the middle of a line of kevlar. What I'm trying to do here is take a length of thread and make a loop out of the entire length, by tieing the ends together.

Suggestions are welcome.

As always thinks in advance.

I just use two offset overhands with fabric tape on the end to hold the tags down. Probably this will cause the entire universe to end.

 

[OverTheTop]

I use a dob of PVA wood glue worked into the knot. It does weaken the Kevlar thread but I compensate by using much thicker thread to start with. That help to stop the harness flossing the side of the tube as well.

For larger harnesses I tend to use a cable tie to hold the loose end of a bowline knot.

As has been said before, there are better knots for Kevlar, but this is what I use since I don't push the limits of the safety factors.

 

[bjphoenix]

If you study knots you fall into a big rabbit hole. There are a lot of knots used by anglers, I've studied a lot of them and just can't find one that I can reliably remember. I can remember the bowline from my fishing days so I've used that one. I put a bit of yellow wood glue on the knot to keep it from slipping. I've heard that epoxy or CA glue on kevlar will weaken it, yellow wood glue isn't as bad because it never gets quite as hard. I did see that there is a double bowline that seems to be more slip resistant so I've tried that one more recently.

I would also be concerned about sharp edges on the holes wearing through the kevlar. I would try a piece of wire.

 

[bjphoenix]

Here is a photo of my usual rigging- I use long kevlar cords even for LPR, with a snap swivel on the end. I connect the snap swivel to the loop on the nose cone. My parachutes also have snap swivels and I connect that snap swivel to the first one. So the only load that goes directly through the loop on the nose cone is from the weight of the nose cone itself.

I was quickly finishing up a rocket Friday so I could launch it Saturday and put in my cloth shock cord retainer. But I didn't quite get it far enough down the tube and it was interfering with the nose cone. Well the nose cone has this nice angled section on one side that would give me more room if I break off the little loop so I did. Then I drilled a couple of small holes and bent a piece of small wire to go through the holes and twist together on the inside. Then I hook the snap swivel to this loop of wire. I think something like this would be stronger than the plastic loop if someone doubts the strength of the plastic loop, and this is plenty easy to do.

 

[K'Tesh]

A loop of Kevlar would likely be better... I'd worry about the wire untwisting, or deteriorating due to corrosion.

 

[BEC]

On the reissue Estes Goblin….if you’re going to stay with the streamers, I’d say just fly it. There’s nowhere near the shock load from a streamer unfurling that there is when a ‘chute that’s going too fast opens (or tries to open and shreds). Otherwise, the Kevlar loop idea makes the most sense to me, which apparently it did to you as well.

Two overhand knots right next to each other generally work for me tying such loops. A dab of white glue/wood glue on the knots can’t hurt.

I was a little surprised at that small loop on the nose cone when I built one of those recent Goblins…but then I learned that that particular blow mold had been in use for quite some time.

 

[MidOH]

Sand under and around the plastic loop. Knot your kevlar cord to it. Put a big ole blob of 15min epoxy on the loop hole. Now it's solid and strong.

Put your chute or streamer a few inches down, on the cord.

 

[K'Tesh]

Sand under and around the plastic loop. Knot your kevlar cord to it. Put a big ole blob of 15min epoxy on the loop hole. Now it's solid and strong.

Put your chute or streamer a few inches down, on the cord.

I found that when glue hits fabric, it hardens it, which can make it brittle. I ruined my favorite shirt, when I tried to superglue a small hole, only to have it turn into a big hole as the hardened fabric cracked and broke out of it.

 

[MidOH]

Superglue burns cotton.

 

[jqavins]

Going off on a tangent, I admit.

I had a mid-power kit with a heavy black plastic nose cone with a little loop like that which I totally didn't trust. The bottom of the shoulder is slightly conical and has a hole in the center. I picked a screw eye (not an eye bolt, but one with the wood screw type threads) that was a good fit to the hole. You'd have to screw it in, even though there's not enough plastic thickness for the threads to bite.

Then I mixed up some BSI 20 minute epoxy, which is a little runny if no filler is added. After pouring the epoxy in through the hole, I screwed in the screw eye, then turned the whole thing nose up. Now, I'm well aware that the epoxy wasn't going to bond to that plastic nose cone, but it didn't need to. It pooled in the bottom of the shallow cone of the base, surrounding the screw, and cured there. That made a formed-in-place nut, firmly bonded to the (wood screw type) threads and tight up against the base of the nose cone. If it's completely not bonded to the plastic then it might spin, but it's not coming out and not wiggling.

 

[MidOH]

I considered that for my instruction less Madcow kit. Seemed like that eye was supposed to go there, but kinda loose.

But I ended up hacking the base of the nose off, and used two ply rings and a disk to make a nose bay. Simply bolted an eye to it.