How tight should Madcow AvBay rivets be?

Hi gang- I'm building the Madcow Frenzy for my L2, and while I'll fly it motor-eject for cert, I want to play with DD, so my loving wife added the removable avBay to last Christmas' present. Sad that it's taken me nearly a year on the project, but anyway...
I'm placing the rivets to hold the AvBay into the upper payload bay, but the 5/32" hole that the instructions called for leave the rivet hanging ~1/2 way out when placed with normal finger pressure. With heavy pressure (after removing the center pin so it doesn't seat), I can get it 3/4 of the way in, but am afraid of pushing it all the way in.
Is this normal, or is there a chance my bit is undersized? How much force should be required? I imagined it would be like sticking a gummy bear to a piece of sheetrock with a thumbtack...and I'm sure that's a technical frame of reference.
The airframe is fiberglassed, but the AvBay coupler is unmodified. The hole is drilled with a drill press, and does clear the tube. The only thing I noticed was some fuzzing in the interior of the AvBay- the airframe was a clean cut.

They shoud be flush with the tube, maybe pull the coupler out adn jsut stick it through the tube and see if its sticking, and do the same with the coupler. I used them in my Stealth i had to make the hole a tad bigger, won't make a difference after you put the rivet together as it expands enough to stay in place.

I've never been a fan of using plastic rivets. In most cases, they are a PITA to get out. What I've used is this: A small sheet metal screw (#6 ) on a smaller bird. Normally you would drill a hole throught the BT and NC in the same way, but a smaller hole, so the screw cuts into the NC. If you already drilled for vivits, turn the NC 10' or so and drill a smaller hole just thru the NC with the BT hole as a guide. To secure the NC, then the small screw can be used to secure the NC. Easy to get in and get out with a few turns of the screw.

If you're looking at DD, you also want to build for shear pins. That's so you can secure the the NC until the ejection charge "shears the pin" and allows the NC to detach, and the chute to come out. Some folks use #2 NYLON screws for this (the nylon screw will break when the ejection charge fires), but for smaller birds, I use a about 1/2" of a small polystyrene rod, in a small hole between the BT and NC

If I understand what you are asking is how to attach the upper payload bay tube to the av-bay and keep it in place during the whole flight?

I have always glued a piece of oak, about 1/4" to 3/8" thick and rounded to match the interior surface of the av-bay, to the inside of the av-bay. Drill a hole large through the payload tube and the coupler/oak block that is big enough for a #6 pan head wood/sheet metal screw. Then drill a hole in the payload tube large enough for the screw to pass through.

Once the screw is in and threads cut in the oak, it can be removed and reinserted as many times as you want. It will hold the payload tube to the av-bay very well and will be one of the last things you'll need to worry about on a DD flight. I have rockets with 20+ DD flights on I to L motors with this setup and that attachment is always solid. You just need to remember to bring a screwdriver along and don't lose the screws.

If you're worried about the alt bay, how about just using t-nuts on the inside of the altbay, and then using #6 screws to attach it? One on each side. A few twists of a screwdriver to remove/attach the alt bay. No "cutting threads in oak, and much stronger.



Here's a 38mmx4" altbay to show the concept. The screw on the left side shows where the t-nut is, and the larger hole is for access to the armining swithc. Corressponding holes are in the palyload BT, and there there is another t-nut 180' from the one in the picture.

Thanks! These ideas for tee-nuts and wood blocking appeal to my preference for robust and repeatable.


Sent from my iPhone using Rocketry Forum