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Kevlar cord attachment

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mugect

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Hello everyone, my first post!

I'm building the Aerotech Arreaux, and want to use Kevlar coming off the motor tube mount. The instructions say NOT to coat the knot for the elastic cord, wondering if it is okay to use CA or epoxy on a Kevlar knot.

Thanks in advance,
Mug
 

dhbarr

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I usually use cloth medical tape to wrap up the ends, nice & flexible but also easily undone.
 

T-Rex

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I have always read that you want to avoid glue on kevlar. I have also read that a small spot of glue on a knot is ok, as long as it is applied where the free tail leaves the knot. Do not saturate the knot.

As dhbarr said above, you will not be able to non-destructively remove the shock cord if you lock it in with a drop of glue...... I tie/sew a small loop in the end of the cord, then run the free end through the anchor point and through to loop. Difficult to explain, but the loop ends up wrapped around the anchor. When/if you want to remove it, just pull the free end back through the loop.

If you are using a kevlar 'string', place something on the string at the end of the tube to spread the force on the tube to a wider surface. This helps prevent the string from ripping through the tube (zipper). Some people use a flag of masking tape, I often use a small rubber sink stopper (make a hole just big enough for the cord to go through, the fix it in place on the cord). A plastic cap from a water/soda bottle might work, but I haven't tried it. YMMV
 

hcmbanjo

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Hello everyone, my first post!
I'm building the Aerotech Arreaux, and want to use Kevlar coming off the motor tube mount. The instructions say NOT to coat the knot for the elastic cord, wondering if it is okay to use CA or epoxy on a Kevlar knot.
Thanks in advance,
Mug
T-Rex give some great advice.
Never use CA on a Kevlar knot. It will harden the knot and run down the line making it hard and brittle.
I have made that mistake before. Epoxy would also make the line stiff and brittle.

You could use a dot of epoxy glue on the Kevlar knot but it won't take much to help set it.
 

Micromeister

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As a scout and Scouter we have always been taught if your having trouble with your knots untying your using the wrong knot!

It has also been proven in the lab. adding glue to any line or rope WILL cause that line to be severed at the glue joint under stress. This is especially true for Kevlar, Nylon and several of the other man-made fibers as the glue hardens the fibers which fracture creating little sharp shards which help cut through the rest of the line just ahead of the glue drop.

If your knot are untying, try a different knot: Bowline, Two or Three Half Hitches for attaching shockcord to nosecone,eyebolt or transition. Butterfly for in-line attachment of recovery systems. Dissimilar lines can be joined with a Sheet Bend or simple overhand loop on the larger line and 2 or 3 half hitches on the smaller line.
As I think about it these 3 or 4 knots are just about the only ones I use on my models these days. NEVER any glue what-so-ever on any of them. Been so long since I've had any kind of Line or knot failure I can't remember the last one.
 

OverTheTop

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I use a bowline at the ends of the harness, whatever I am using. I use a couple of cable ties (only one on the smaller birds) to give some extra confidence that the knot won't slip unexpectedly under snap loading.
 
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