Bad rail button drilling...

[ewomack]

Well, this isn't a great start to getting going on the DX3 again after a long time - I measured out where the rear button should go (it at least seemed good) and the drill hole itself was clean, but when I screwed in the screw, the wood cracked as pictured below. The screw doesn't emerge even when screwed all of the way in, but it looks pretty awful and I'm not sure if it will affect the rocket performance in any way. I have not epoxied the button in yet - is there a good recovery plan for this? I tried drilling the hole slightly up, but not with much luck. I suppose switching sides is an option? Could filling the hole in and re-drilling work in some way?

 

[GalantVR41062]

If it was my rocket I would pull the screw out, fill the void with wood glue and try to push and hold the fractured plywood back to flat.

Then after the glue dries either re drill further up or drill the hole on another side. The centering rings should be 1/4" thick.

You can also glue a thin ring of coupler or a chunk of body tube on the inside of the airframe hanging down from the rear centering ring. This will help with hangerash and sitting on the launch pad/landing forces.

I hope your motor retainer mounts flush to the bottom centering ring to help transfer the thrust of the motor to the airframe.

 

[waltr]

Yea, a near miss in hole placement. Been there done it.
I would just wick thin CA into the fractured wood (with the screw removed). This should make the wood strong enough to hold the rail button.
No effect on performance if the button is secure. Might not look great but nothing else.

 

[crossfire]

Well, this isn't a great start to getting going on the DX3 again after a long time - I measured out where the rear button should go (it at least seemed good) and the drill hole itself was clean, but when I screwed in the screw, the wood cracked as pictured below. The screw doesn't emerge even when screwed all of the way in, but it looks pretty awful and I'm not sure if it will affect the rocket performance in any way. I have not epoxied the button in yet - is there a good recovery plan for this? I tried drilling the hole slightly up, but not with much luck. I suppose switching sides is an option? Could filling the hole in and re-drilling work in some way?

View attachment 523129

I would also put a glue fillet around CR where it touches body tube and MMT

 

[Tractionengines]

If you put the glue fillet around the ring to body tube joint first. Both top and bottom of CR. The fillet support helps keeps this from happening. I have some times had the drill run out the side of the CR. No issue the body tube, CR, and epoxy all share the load. ( But I tap for machine screws, into the plywood and epoxy. There is only a little "splitting force" this way. If you use a wood screw the "wedge shape" puts a lot of force into splitting the CR.)

As others have said. Pull the screw. CA the fracture back as much as you can. Then add glue/ epoxy fillets. Then re-drill and run the screw in. The CA and fillets will support the ring from splitting again.

Mike.

Edit to show example.

 

[AstroAbaqus]

This has been my nightmare when I did my very first holes. But I had similar damage on wood in the past. Best solution is to remove the screw first. Then inject, maybe with a syringe, into the hole some wood glue (maybe add some wood dust or a filling if you like) and wick the back with CA and press in. Once the glue is dried is up to you. I would use some wood filler and sand it to remove the cosmetic damage.

Otherwise if you have epoxy and some microfibres you can use them to fill the hole and the back and sand it once done. But probably too overkill. In general wood is particularly forgiving for minor damages.

 

[terryg]

If it were me, I would glue on the motor retainer (aeropak or equivalent) and then remove the rail button screw and press the wood bulge back in position. I would then pour some epoxy into the gap between the retainer and the body tube. When the epoxy is cured then screw in the rail button. On my builds I like to glue on an extra piece of plywood to the centering ring to an give extra thick area to drill for the rail button.

 

[Rocketclar]

What I've done for many of my rockets, is to use a small basswood standoff. That helps with minimizing rail "burn" on the finish. Here's a pic of my L2 rocket. I did this since it's Quantum tube and I was using a piston and didn't want the screw to go thru the AF. (Yes, there's also a launch lug which has never been used.) Another technique I've used is the Acme Al rail guides. I've used these to retro fit a launch lug rocket to a rail.

 

[kalsow]

I wonder how many times this has happened on the top side of the centering ring: nobody noticed, no extra measures taken, no failure with the rail button.

Grab the button and give it a good shake. If it holds, it's good enough.

 

[Zman1961]

Been there done that. When I install rail buttons this way, now I always glue a piece of hardwood dowel (maybe 1/4 to 1/2 inch thick, depending on the rocket) sanded to the correct shape to the outer edge of the centering ring. This provides a larger target area for the screw. Measuring everything out along the airframe tube helps as well. You can even glue a piece of dowel into the shoulder of a balsa tail boat if there is one on the rocket. once again, make good measurements along the airframe before gluing in the motor tube assembly. This has worked well for me.

 

[Troy3003]

Just put another small block on the rear and move your button down slightly to catch the new block.

 

[fyrechaser]

What I've done for many of my rockets, is to use a small basswood standoff. That helps with minimizing rail "burn" on the finish. Here's a pic of my L2 rocket. I did this since it's Quantum tube and I was using a piston and didn't want the screw to go thru the AF. (Yes, there's also a launch lug which has never been used.) Another technique I've used is the Acme Al rail guides. I've used these to retro fit a launch lug rocket to a rail.

I've been using stand-off's for a lot of years. Makes it easy to put them where you want them, and no worries about missing a CR or bulkhead. Very useful on minimum diameter projects.

 

[David Schwantz]

I'm with John and I would glue a block below the CR and then reinstall.

 

[bobbyg23]

Glue that sucker in. It will be fine. After it dries, sand off the stuff that cracked up.

 

[AfterBurners]

Not sure what kind of motor retention you will be using but, pull the screw out and fix whatever needs to be fixed (Remove the split wood and sand the back of the center ring flush) and then just get another center ring and glue / epoxy it behind the one you have. It will cover your mistake and hopefully support the screw better? You will probably need to be creative with motor retention or you can use one of MADCOW's retainers. You should be good to go.

 

[ewomack]

Wow, that was far too long of a delay on my part. Life got in the way of me drilling and gluing for a while (yes, not a great few weeks since I've posted).

Thanks everyone for the advice and suggestions. I decided to (finally) try to fill the hole and redrill a tiny bit further up the tube- so far it looks okay and with the screw in I don't see any further pushing on the ring. I haven't epoxied the button in yet.

So how does one get glue into that tiny hole without inadvertently gluing the button down? I have some CA that has a pin point spout, which would probably work, though the instructions suggest epoxy - I have 30 minute epoxy, so I suppose I could pour some down carefully and remove anything left on the surface before screwing everything back in.

And I'm guessing the screw should be in far enough so the button can't move up and down, but it can still spin.

Yes, I'm completely new to this and I don't really have anyone around to ask, so thank you everyone for your patience with my newbie anxieties.

 

[OverTheTop]

So how does one get glue into that tiny hole without inadvertently gluing the button down?

I would put CA glue into the hole, then screw the screw in. To keep any CA off that comes back out of the hole (not likely as the screw will push it further in) I would put a piece of baking paper around the screw at the base of the rail button. Paper can be ripped off later, after the CA cures.