Mistake in drilling hole on motor mount ring

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kavel_r

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Wanting to save costs, rather than using an aeropack retainer, I got the madcow motor retainer for my patriot build.

I started drilling the pilot holes for the inserts, but the first hole I drilled was too close to the center of the ring. I drilled two new holes that were farther from the center, but the plywood chipped slightly.

How should I fill the hole and the chips? Wood filler? Epoxy? As it's the motor mount, it needs to be as strong as possible.
 
kavel_r said:
Wanting to save costs, rather than using an aeropack retainer, I got the madcow motor retainer for my patriot build.

I started drilling the pilot holes for the inserts, but the first hole I drilled was too close to the center of the ring. I drilled two new holes that were farther from the center, but the plywood chipped slightly.

How should I fill the hole and the chips? Wood filler? Epoxy? As it's the motor mount, it needs to be as strong as possible.
Click to expand...

Definitely Epoxy.
And make sure to put a layer of quality epoxy from the edge of the motor mount (where the engine aft closure binds on the MMT) to the airframe, across the rear MMT centering ring.

a

P.S.: Wood filler is just for looks. Epoxy is for strength. You need the latter.
 
afadeev said:
Definitely Epoxy.
And make sure to put a layer of quality epoxy from the edge of the motor mount (where the engine aft closure binds on the MMT) to the airframe, across the rear MMT centering ring.

a

P.S.: Wood filler is just for looks. Epoxy is for strength. You need the latter.
Click to expand...

Thanks. JB-Weld should be plenty strong enough, right?
 
afadeev said:
Yep, and perfect for the heat-sensitive application.
Click to expand...

Deeeettttooo, (Ditto, I agree) I filled in a defect with 30 minute Tower Hobbies 30 minute epoxy that was 20 years old when I was building a rocket and it works fine. Rocket is still around if I can find it in the basement. Kurt
 
Alright! I was worried that I might have irreversibly compromised the strength of the ring.
 
I haven’t seen them, but I’m guessing you could leave the hole and chip as is and the ring would still be strong enough.

Id fill with epoxy, just because it’s handy, and wouldn’t lose a wink of sleep
 
Drill the bad hole out to next size larger wood dowel, glue dowel into hole, wait for glue to dry/cure, then sand flush with CR, soak dowel with CA (not necessary but may help when re-drilling), re-drill hole correctly. Easy fix.
 
Or move that ring further up and use the other ring.


Sent from my iPad using Rocketry Forum
 
rharshberger said:
Drill the bad hole out to next size larger wood dowel, glue dowel into hole, wait for glue to dry/cure, then sand flush with CR, soak dowel with CA (not necessary but may help when re-drilling), re-drill hole correctly. Easy fix.
Click to expand...
That would work, but the hole is so close to the edge of the ring that drilling it any larger would break the edge.
 
kavel_r said:
Sorry, I don't understand what that means. Could you explain further?
Click to expand...
If the CR was not already glued in place, you could have either replaced it, or turned the damaged CR into 3rd mid-MT spare, and put a new one in it's place.

Assuming that the CR is already epoxied, moving or sanding it will be challenging. Just epoxy over and let it fly. It will hold just fine.

In all likelihood, you have overbuilt the rocket anyway, just like the rest of us :).

a

Sent from my Pixel using Rocketry Forum mobile app
 
kavel_r said:
Wanting to save costs, rather than using an aeropack retainer, I got the madcow motor retainer for my patriot build.

I started drilling the pilot holes for the inserts, but the first hole I drilled was too close to the center of the ring. I drilled two new holes that were farther from the center, but the plywood chipped slightly.

How should I fill the hole and the chips? Wood filler? Epoxy? As it's the motor mount, it needs to be as strong as possible.
Click to expand...

Not a big deal at all. Just fill hole with epoxy and fly the heck out of the rocket.
 
Without knowing the details of the build, filling with epoxy is a good idea. For many builds the holes probably don't even matter.

Sent from my SAMSUNG-SGH-I337 using Rocketry Forum mobile app
 
I filled it with JB Weld epoxy earlier today. Thanks for all the suggestions!
 

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