I made a boo-boo. L1 flight zephyr aft centering ring.

[Csheffield]

Level 1 cert build here flying in June.

Bought a zephyr and a flat bottom retainer because I liked the look of it over the screw ones and it was one of the recommended retainers for the zephyr on apogees site.

The build is going along great. Spent days sanding/filling the fins. Sanding and filling the body tubes. When super glue tacking the alignment rails, I made them flush with the motor tube so I’d have a nice flush bottom for my shiny retainer. I epoxied everything and it went well. Last thing I epoxied was the aft centering ring. Got it in and put a nice fillet of epoxy down. Sweet!

Now that it dried up a little and I’m looking at it, the aft ring really isn’t glued to the motor tube besides a little bead I smeared on before sliding the ring on.

Is this a deal breaker for a level 1 flight? I’m feeling mighty dumb right about now.

 

[dhbarr]

How well did the motor tube attach to the other ring(s)? Anyhoo those two bits of wood will take force from the thrust ring.

If it'll keep bothering you, you could convince some thin epoxy to get in there or drill a small hole or three to force more epoxy into.

I wouldn't overthink it as long as it holds up to a bit of hand pushing.

 

[Back_at_it]

Level 1 cert build here flying in June.

Bought a zephyr and a flat bottom retainer because I liked the look of it over the screw ones and it was one of the recommended retainers for the zephyr on apogees site.

The build is going along great. Spent days sanding/filling the fins. Sanding and filling the body tubes. When super glue tacking the alignment rails, I made them flush with the motor tube so I’d have a nice flush bottom for my shiny retainer. I epoxied everything and it went well. Last thing I epoxied was the aft centering ring. Got it in and put a nice fillet of epoxy down. Sweet!

Now that it dried up a little and I’m looking at it, the aft ring really isn’t glued to the motor tube besides a little bead I smeared on before sliding the ring on.

Is this a deal breaker for a level 1 flight? I’m feeling mighty dumb right about now.

No problem at all. The Zephyr is an over engineered rocket and the rear end of it is extremely strong. The fins attach to the motor tube so the force will be transferred through the fins to the main body. You have a nice bead of epoxy around the outside of the rear ring so it's secured. I don't see any issues at all.

If it will make you sleep better, you can take your epoxy and put a small bead around the outside of motor tube where it meets the rear ring then heat it up with a hair dryer and it will thin and flow into gap. Give it 5 mins to soak in then wipe away the excess with a towel lightly wet with alcohol.

 

[ThirstyBarbarian]

No problem at all. The Zephyr is an over engineered rocket and the rear end of it is extremely strong. The fins attach to the motor tube so the force will be transferred through the fins to the main body. You have a nice bead of epoxy around the outside of the rear ring so it's secured. I don't see any issues at all.

If it will make you sleep better, you can take your epoxy and put a small bead around the outside of motor tube where it meets the rear ring then heat it up with a hair dryer and it will thin and flow into gap. Give it 5 mins to soak in then wipe away the excess with a towel lightly wet with alcohol.

I agree with this. It won’t matter. Forward thrust will be transferred from the motor’s thrust ring, to the centering ring, to the fin tabs, to the rocket body. The motor tube doesn’t bear any of that force. You can actually build a rocket without any motor tube at all if you want to as long as the ejection charge is inside the main compartment of the rocket. Motor tubes help align the motor as you slide it in through the centering rings, and they allow you to use motor eject with motors that are too short to reach the forward ring, and they also allow you to glue fin tabs to the motor tube, but for transferring thrust, they are kind of optional.

That said, next time put a ring of epoxy around the end of the motor tube before you put the aft ring on.

Good luck with your cert!

EDIT: I just reread the original post and saw that you did smear a bit of epoxy on the tube before putting on the ring, so you are definitely good to go. You don’t need external fillets for that joint. The danger would be if you try to add any glue externally, you could get some epoxy down inside the motor tube and have a serious pain in the butt.

 

[John_461]

I have that retainer on a couple of my models and it works great from everything from a baby H up to J435s. The thrust ring on your motors pushes against the motor tube, not the centering ring. As long as you have solid attachments from your motor mount to your fins to your body tube, you'll be completely fine. Most (not all) H motors produce a maximum thrust between 30-60 pounds.

In any case, like others have said, some thin epoxy or even wood glue around the motor mount to centering ring joint should alleviate any concerns.

You are, however going to notice a bit of play between the thrust ring of the motor and the motor tube. To solve this, I rolled up 2 pieces of Estes wadding that I had sitting in my range box, and stuffed it between the base of the motor and the retainer. The next rocket I used that type or retainer on, I left about 1/4" of motor tube sticking out from the aft centering ring to eliminate any play.