Threading that darned Kevlar up through the body tube!

[jflis]

A new EMRR review of the FlisKits Mudwasp by Jon Chrisman (thank you Jon ) resulted in a bit of frustration for him when, after attaching the Kevlar shock line to the engine mount, he tried to thread the free end of the cord up through the body tube.

Frustrating at best, even more so when you have a bead of glue inside the near end of the body for the engine mount...

In the past, what I did was to tape a narrow paint brush to the end of the cord and just *drop* it through the body tube, letting gravity pull the cord through. Then simply install the engine mount and you're all set.

However, that technique often results in a large portion of the cord getting covered in glue (not a good thing as this can weaken the cord). Someone (I can't for the life of me remember WHO) gave me a new technique that I would like to share here.

Pull up the attached PDF file for reference.

Basically, after you assemble your engine mount and attach the cord to it, you pass the free end of the cord down the top of the engine tube and out the bottom. You then glue this engine mount into the body tube as you normally would. Once dry, you can then pass the cord back into the bottom of the motor tube and out the top of the body tube. (It may still be helpful to tape a paint brush or wood dowel to the end of the cord to help with this part of the process... )

Very simple, works like a charm. The attached file will make this much clearer, I am sure

Enjoy!
jim

View attachment Installing EMK with Kevlar.pdf

 

[Micromeister]

Jim:
Your graphic is EXACTLY the way i've always (or as far back as I can remember) installed motor mounts and then dropped the shockcord thru models of all sizes. but it is very helpful on Micros.

With the cord outside the rear of the model, if you've used a little to much glue and want to wait for it to set before sending the shockcord back thru it's fine to leave it just like it is. I use the same method with motor block mounts as well. Note the channel filed in an old motor casing to make inserting and removal of the casing "Pusher" easier
Hope this helps.

Edit:
Guess this is one of those, Doh moments..were we say...I thought it was just the way it's done? LOL I can't recall ever actually seeing it in instructions. Personally I never liked the idea of the tri-fold "teabag" estes shockcord mount, so I switched to anchoring to the motor mount or motor block Way back when. By attaching the shockcord anchor to the motor mount or block that ment it needed to be kept out of the way during installation. The most natural way to do that was to send to back thru the motor tube or ring. I don't believe I'm the first one to do this, but I can say I've been building this way since at least 1970-71, when I first started using stanless steel fishing leaders as Shock cord anchor mounts.

 

[KDRaven]

Jim the way that you mentioned by putting the kevlar in the motor mount tube then installing the mount into the body also works for the HPR birds also. I have been doing that way for the last few rockets that I have built because it is kind of fun trying to feed 12' of shock cord down the body when there is epoxy for the top centering ring in the body tube.

 

[gpoehlein]

Jim:
Your graphic is EXACTLY the way i've always installed motor mounts and then dropped the shockcord thru models of all sizes. but it is very helpful on Micros.

With the cord outside the rear of the model, if you've used a little to much glue and want to wait for it to set before sending the shockcord back thru it's fine to leave it just like it is. I use the same method with motor block mounts as well. Note the channel filed in an old motor casing to make inserting and removal of the casing "Pusher" easier
Hope this helps.

That little installer tool is too slick, John! I love the ring glued to the base of the motor to insure that the motor block goes in to the right depth every time. Neat idea!

 

[pyrovette20]

Try wrapping the bottom half of the kevlar with wax paper and using masking tape to hold it. Once the epoxy dries you can usually pull on the wax paper and pull it off. If the tape rips or dosent come all the way off no big deal. You end up with a little bit of tape and/or wax paper left on the centering ring or motor mount. I grind away a little bit of the inside part of the top centering ring about 1/8'' x 1/2'' wide run the kevlar through around the motor mount and back up then knot it and epoxy it all.

 

[InFlight]

Jim, I'm going to have to give this a try

I normally tie the kevlar cord to a 1/4" washer or a fishing line sinker and drop it down through the tube. But, there have been a few times were I still got a little bit of glue on the cord.

 

[sandog]

This is the way Polecat kits say to do it too, so it works great on HPR birds as well.

 

[skippy-2]

I don't know where I got the technique from, but I detailed it here in a test of the Fliskits MMX Cluster Mount:

https://rocketryforum.com/showthread.php?t=33768

It is so logical once you start doing it, you wonder why you never did it before.

 

[gpoehlein]

I don't know where I got the technique from, but I detailed it here in a test of the Fliskits MMX Cluster Mount:

https://rocketryforum.com/showthread.php?t=33768

It is so logical once you start doing it, you wonder why you never did it before.

Close, Skippy - you wonder why it never OCCURED to you to do it that way before!

 

[rstaff3]

When you get old, you sometimes wonder why you didn't REMEMBER to do it that way :surprised:

 

[Pantherjon]

I had done it before(but not tying anything to the cord) but had a major brain fart when I was building the Mudwasp for some reason!

 

[jflis]

I don't know where I got the technique from, but I detailed it here in a test of the Fliskits MMX Cluster Mount:

https://rocketryforum.com/showthread.php?t=33768

It is so logical once you start doing it, you wonder why you never did it before.

BINGO! That was my thought when someone first showed this to me. It is elegant, simple and (after having seen it) seems quite obvious...

Yet here I am 45 years into the hobby and I just heard about this technique in the past 3 months...

Go figure LOL

 

[Fore Check]

BINGO! That was my thought when someone first showed this to me. It is elegant, simple and (after having seen it) seems quite obvious...

Yet here I am 45 years into the hobby and I just heard about this technique in the past 3 months...

Go figure LOL

I started doing this technique very, very early in my days as a BAR. I got the technique through very well photo-illustrated instructions in my first clone kit back in the day before I started cloning and upscaling on my own.

The kit was an Estes Goblin clone from Thrustline. The photo illustrated instructions were there because the clone kit came with a Kevlar thread shock cord mount mod in the kit. Incidentally, this was my first exposure to using Kevlar as a shock cord mount too. I soon started using Kevlar for shock cord mounts on every LPR/MPR build (doing it as a mod as necessary) and following the basic instructions in that first Goblin clone kit I had. I believe I still have that little packet and instructions with photo somewhere in my "archives."

I too use this method on all of my HPR rockets where it comes into play. For the record, Binder Design spells out in their well illustrated instructions this same technique of passing the shock cord down through the motor tube when installing the mount.

 

[hokkyokusei]

The same technique is described in PML kits IIRC.

 

[BobCox]

QModeling also recommends tucking the shock cord. (e.g See page 8 of their Viper manual). They also include an additional refinement to the technique. Instead of threading the shock cord all the way out the back of the motor tube, fold it up and leave it inside the motor tube. That keeps it out of the way so it won't get glue on it from the front or the back.