1st MPR Launch = Disaster

Today was my first launch as a Tripoli member. It wasn't ideal weather to begin with. 35 degrees and winds between 15-20 mph.

Some of you may remember that I just got done building the Estes Ventris that we called Lady Liberty. I built the kit to the exact specifications. It flew on a G80-7T.

The rocket went up just fine and the ejection charge did its job. I also used the Estes Sonic Igniter and it worked fine. But at ejection the entire shock cord mount came out with it. I used a pretty strong superglue that I have used with many other rockets. When I rebuild this rocket or buy another one, I was wondering what tips you guys had for a different kind of shock cord mount and where do you get the Kevlar to make a shock cord. The elastic ones that Estes has I am told on here and at the launch are unreliable, even though it wasn't the culprit today. It may have snapped if the mount had stayed in place but I guess we'll never know. : (

And to top it all off I lost the Altimeter 1 that was attached to the nose cone. Oy.

On a positive note, my kids Estes Code Red went up without any problems on a C6-5. : )

The instructions say use white glue, not super glue which is what I used and has worked fine.

Sorry for your lose.

Derek said:

The instructions say use white glue, not super glue which is what I used and has worked fine.

Sorry for your lose.

Click to expand...

Alright, so I deviated a little bit. : )

Yeah I can't decide what to do with it now. The fins and the main body tube are all in great condition. Missing the nose cone, payload section, and transition part. Plus the parachute and shock cord.

You may be in luck. As it so happens, I have a spare ventris nose cone, payload bay and transition. Pay for shipping and it is yours.

Derek said:

You may be in luck. As it so happens, I have a spare ventris nose cone, payload bay and transition. Pay for shipping and it is yours.

Click to expand...

Thanks man! That's awesome. Send me a private message with your address and I'll send you a check/cash. Do you have a recommendation for a different kind of mount? Also, where do I get Kevlar to make a new shock cord?

I'll cut the estes shock cord out and you can use that. Just make another tri fold mount and use white glue.

Derek said:

I'll cut the estes shock cord out and you can use that. Just make another tri fold mount and use white glue.

Click to expand...

Just regular Elmers white glue?

For this, good old white glue and a new trifold is going to be easiest.

In the future, you can add Kevlar to the motor mount tube. I typically make it short, and tie the elastic to it to avoid zippers.


1/4" thick should be more than enough (at 1200lbs break I'm sure of it): https://rocketrywarehouse.com/product_info.php?products_id=160

Here's one way to do it. Just make sure if you have TTW fins the wrap isnt in the way of the tabs. This is 1/4" on a 38mm MMT



Most of the time I'll make the loop shorter than the body tube, so the kevlar doesn't cut into the body tube. If you need to change the cord above it and can't reach into the tube, just fish it out the back of the motor mount and viola! there it is outside the rocket.


Above I used JBweld. You can used epoxy as well, but heat could become an issue with that. Be careful if you epoxy two straps to the MMT that you can still position them in a way they dont block any fins. Don't ask how I know this.


In my Onyx, my first midpower build, I braided some thin kevlar line and came out of the tube with it. I've launched it a bunch of time like this and no zippers, I tie 6 foot of elastic to it.



On some low power stuff you can use some kevlar thread. Some of the Estes kits used to have you attach elastic to the centering rings much like this, and it works. Just hard to replace later.


Or if you prefer overkill:

DizWolf said:

For this, good old white glue and a new trifold is going to be easiest.

In the future, you can add Kevlar to the motor mount tube. I typically make it short, and tie the elastic to it to avoid zippers. Ill add some photos and a link when I get to my computer

Click to expand...

Thanks. I appreciate it. Lots to learn for sure.

Tightbond II wood glue works well too...

TheSamurai said:

Thanks. I appreciate it. Lots to learn for sure.

Click to expand...

No problem. Lots of people helped me, so I try to share what I know. I certainly have plenty more to learn as well.

Spooks said:

Tightbond II wood glue works well too...

Click to expand...

after cutting out the shock cord, that looks like what I actually used.

for the most part, titebond 2 and elmers white glue can be used interchangeably. just don't use elmers school glue!

Derek said:

after cutting out the shock cord, that looks like what I actually used.

for the most part, titebond 2 and elmers white glue can be used interchangeably. just don't use elmers school glue!

Click to expand...

School glue is good for couplers when you need them to slide. Glue All locks before I can get them to the right place.

I got 100' of great 1/8" Kevlar from Fuddrucker here on forums , sent PM , and arrived in couple of days quick service and great cord

CA's (i.e., super glues) do not work that well with regard to shear loads. Imagine two planks being pulled in opposite directions. That is shear.

Paper glues, like Elmer's, or epoxy is a better bonding medium in this application.

Greg

GregGleason said:

CA's (i.e., super glues) do not work that well with regard to shear loads. Imagine two planks being pulled in opposite directions. That is shear.

Paper glues, like Elmer's, or epoxy is a better bonding medium in this application.

Greg

Click to expand...

Thanks for the advice everyone. I think the other glue I have out in the shop is Elmer's Wood Glue. Don't think I have the white so I'll have to go buy some.

Sorry to hear of your loss, lots of good advise up there to help you rebuild.

I have ordered from www.thethreadexchange.com a couple times. Great selection, good prices, speedy shipping...I was very happy doing business with them.

TheSamurai said:

Elmer's Wood Glue. Don't think I have the white so I'll have to go buy some.

Click to expand...

That's good stuff, somewhere in the white glue - Titebond spectrum.

I've also epoxied a nylon rope to the inside of the tube (big glob), a variant of how LOC says to do it on thier kits.

bill_s said:

That's good stuff, somewhere in the white glue - Titebond spectrum.

I've also epoxied a nylon rope to the inside of the tube (big glob), a variant of how LOC says to do it on thier kits.

Click to expand...

I didn't even think about using epoxy for the shock cord mount. It's crazy because I didn't think that simple white or wood glue would work better than superglue. Shows you how much I know about how good which glues are with which surfaces.

Like Greg Gleason said, super glues shear easily. My rule of thumb, Elmer's white (not easy clean or school glue) for A-E. epoxy for F and above. I only use super glue to strengthen the ends of body tubes. Wood glue is functionally good, but not sure how well it paints over. I also don't like Trifold on MPR. I just built a Leviathan with a baffle. Put eyebolt on baffle.
https://www.rocketryforum.com/showthread.php?47232-Estes-Leviathan-My-first-MPR-build

bill_s said:

That's good stuff, somewhere in the white glue - Titebond spectrum.

I've also epoxied a nylon rope to the inside of the tube (big glob), a variant of how LOC says to do it on thier kits.

Click to expand...

I've had LOCs tiny little nylon rope burn through before. It doesn't take much.

Yeah I brought out my big 4 inch diameter Estes NCR SA Archer with a G-80 and said forget it as soon as I stepped out of the van into that cold wind, yuck!

TheSamurai said:

But at ejection the entire shock cord mount came out with it. I used a pretty strong superglue that I have used with many other rockets. )

Click to expand...

Super glue is good at lots of things but a shock cord mount is not one of them. Wood glue would have been fine; epoxy would work but would have been overkill.

Resist the temptation to deviate from the instructions until you know why you want to deviate from them. Tip: super glue is not very good at handling shear stresses compared to other adhesives. Shock cord mounts are mainly subjected to shear stresses.

RoyAtl said:

Super glue is good at lots of things but a shock cord mount is not one of them. Wood glue would have been fine; epoxy would work but would have been overkill.

Resist the temptation to deviate from the instructions until you know why you want to deviate from them. Tip: super glue is not very good at handling shear stresses compared to other adhesives. Shock cord mounts are mainly subjected to shear stresses.

Click to expand...

Yeah I figured that out at quite the cost. lol