Knots for Quest Quad Runner?

Hi,

First post here...

Can anyone recommend the best knot for step #1 in the attached instructions? One end of an elastic cord is to be tied to both ends of a kevlar cord. The goal here is to make a loop of the kevlar and not have it come loose from the elastic.

And, since we're talking knots, any suggestions for what type of knot to use for step 5 (a) where the instructions say to use "XXXX" knot?

Thanks!

https://www.questaerospace.com/instructions/5016.pdf

I've built the Quadrunner, and it's a great rocket.

I'm going to give you two bits of advice. First, the knot. I can't remember what knot I used, but I just now googled "knot for tying two strings together," and found the Double Fisherman's Knot, which you can find here, at animatedknots.com. But you might google that term and see if there's another knot you prefer.

But a more important piece of advice: The elastic part of the shock cord is woefully short. I built the rocket last year, and by the time I flew it, I realized the shock cord was inadequate. I've had rockets with short cords get damaged, because the nose cone blows off, then snaps back and smacks into the rocket, damaging a fin or the body tube. I ended up tying even more elastic to the end of the shock cord. So, I ended up with a three-piece shock cord - Kevlar, elastic, and more elastic.

I'd suggest going to a fabric store or craft store and getting a nice, sturdy piece of sewing elastic - either the round stuff as you get with the kit, or a wide flat piece, maybe 1/4 inch thick or more. Make the total length of the shock cord at least 2-3 times the length of the rocket. Don't use the stuff in the kit.

Or, if the Kevlar is long enough (I don't think it is in the kit), or if you have some spare Kevlar, and you can get it to the point where it reaches to just below the forward end of the body tube, you could tie that into a bowline. Then, you can attach an elastic shock cord using a snap swivel, and replace the elastic part when it becomes worn out - just unhook the snap swivel, tie on some new elastic, and re-hook the snap swivel onto the bowline. In this case, you just have to make sure the Kevlar is long enough that you can reach the end of it from the top of the tube. In my kit, the Kevlar is way too short to do this, so if the elastic wears out, I'll have to figure out how to replace it.

Enjoy the rocket. Here's my first flight video:

[video]https://youtu.be/PClIuUg0I24[/video]

The easiest is to take the three ends together and tie a simple overhand knot. It will hold very well. If you want some insurance against it untying, put a drop of wood glue on it and let it dry before installing.

kj

A simple overhand knot is all thats required for this Kevlar to elastic joining.

It is not a good idea to put any type glue on any knot: First; If the knot needs glue to stay tied it is not a good knot or application.
Second and more important; Dried glue acts like a knife edge sawing through the Kevlar and elastic as the materials are flexed back and forth where the glue ends and the raw materials begin. This sawing action will eventually cause a shock-cord failure.

Thanks for all the helpful replies.

Charlie

Yep, a single overhand knot works well. And don't let the folks who make this product know that you shouldn't put glue on knots. https://loonoutdoors.com/product/uv-knot-sense/

While I agree you need an adequate knot for the application, I've been super glueing my knots for quite a while with no issue, mainly on kites, but it's certainly no fix for a crap knot. I do this on 200lb Kevlar and 550 paracord, not elastic (where I think the knife idea probably holds) without any problems.

Even though gluing a knot typically reduces its strength, there's usually plenty of strength to begin with for our applications. Also, the bigger issue for many people tying knots is making them dressed properly and keeping the knot tight. So using glue is sometimes the lesser of two evils.

Or, you know, that model rockets tend to be ephemeral and usually will disappear long before the glue on a shock cord knot ever has a chance to degrade the performance of the cord. :eyeroll:

kj

Micromeister said:

It is not a good idea to put any type glue on any knot: First; If the knot needs glue to stay tied it is not a good knot or application.
Second and more important; Dried glue acts like a knife edge sawing through the Kevlar and elastic as the materials are flexed back and forth where the glue ends and the raw materials begin. This sawing action will eventually cause a shock-cord failure.

Click to expand...

+1..........

Teddy

+1 for that animated knots link.

In general, I don't like putting glue on knots, because, what if I need to untie it and replace a cord?

My favorite knot for tying something terminating on a screw eye or c-link is the stevedore knot.

For tying two lines together, I use the slim beauty knot.

But, I'm always open to other suggestions!