Need help attaching guide buttons

[Ccolvin968]

I'm working on my first HP rocket. The Formula 75 and I have completed it all... except for mounting the launch buttons.
The way that I want to do it is use some JB weld onto the bottom of the buttons (#10) and let it set/cure and I'm off.
However, I can't seem to get the buttons straight to save my life. I'm absolutely terrified to mess this part up.
I don't want to drill holes and get the measurements wrong then have to re drill and patch holes.
How do you get yours perfectly lined up?
I don't have access to a HP guide rod, so that's a problem.
The 29th of October is my level 1 cert flight, so I have a little time.
I don't have access to special tools. I was hoping a tape measure and a pencil would do.
Any suggestions for how to get them lined up and then mounted so I don't have to worry about anything?
Thanks much!

 

[Tonimus]

Use a door jamb and a pencil to draw a straight line on the body tube, then attach the buttons somewhere on that line. I prefer to screw the aft one into the rear centering ring and I mount the front one near the CG.

 

[rms]

I have used door jambs in the past. I now use a 3 foot piece of 1"X1" aluminum angle to mark straight lines on body tubes.
I believe I get a finer little more accurate line with the angled aluminum. Your milage may differ.

 

[Worsaer]

I have used door jambs in the past. I now use a 3 foot piece of 1"X1" aluminum angle to mark straight lines on body tubes.
I believe I get a finer little more accurate line with the angled aluminum. Your milage may differ.

+1. Works every time..

 

[Onebadhawk]

Use a door jamb and a pencil to draw a straight line on the body tube, then attach the buttons somewhere on that line. I prefer to screw the aft one into the rear centering ring and I mount the front one near the CG.

+1....
This'll work for you....
I your tools are a bit lacking you'll see
that you get a nice straight line via this method. ...

Teddy

 

[OverTheTop]

I now use a 3 foot piece of 1"X1" aluminum angle to mark straight lines on body tubes.

+1. Yep, works well. Make sure you buy a straight piece.

 

[fyrwrxz]

The door jamb thing might work with just tubes but the OP stated he finished his F-75, meaning the fins are in the way. I keep a variety of alaly angle stock to lay on center lines (like a door jamb) but try to find something either 1) small enuff to fit between the fin centerlines or 2) go above the fins and extrapolate your line down from the centering angle into your fin can area. I've even used a drawer pulled out so the rocket hangs on either side to draw lines. Depending on stability, I like to put my buttons at the bottom and just below my Cg-depends on your lift off speeds. Others may have differing opinions (YMMV!). Straight smoke and good chutes!

 

[Tonimus]

3 inch tube, 3 fins, should still fit in a door jamb. Might not be right center between fins, but it'll be a straight reference mark.

 

[K'Tesh]

I think everybody is reading this wrong... They are thinking of alignment (so the rocket wouldn't be straight on the rod). I'm reading this as the bolts/screws are leaning... (T) instead of straight (T). [EDIT] Maybe I read it wrong, but still the info below should be helpful).

When I aim to make my rail buttons to go into a centering ring, I usually glue or epoxy a small scrap of wood (either bass or ply) to the CR to make sure that the drill hits something solid and doesn't create an ugly blow out, should I miss slightly.

For my rail buttons that are not going into a centering ring, I usually glue a scrap of balsa to a scrap of bass or plywood, then drill a hole through them. I then press in a T-nut into the harder wood, and sand the balsa to match the inside curve of the body tube. I drill my hole for the bolt/screw, screw the bolt in, and get the wood/T-nut placed, tacking it in with some medium thickness CA. Next, I back the screw out, put a dab of petroleum jelly on it, and screw it back in. Then I wick some super thin around the body tube/backing joint. Some epoxy putty to fix it in place (and prevent the laundry from snagging on it), and I'm done.

I highly doubt that if the rail buttons are not in line with each other (forward and back), that the rocket will suffer much for it. Sure, you may loose a few feet in max altitude, but as long as you only use two buttons, it won't bind (may look odd up close though).

Another trick for keeping things straight, is to poke (or drill) a small pilot hole to keep your drill bit from wandering.

 

[TopRamen]

V-Blocks on a drill press will make the holes line at 90 degrees, just like drilling and tapping any round object.
The concept is what counts, not having a drill press or tapping the holes afterward.

[video=youtube;m4PLNyQJ4Yk]https://www.youtube.com/watch?v=m4PLNyQJ4Yk[/video]

[video=youtube;TpPR5JhTFdc]https://www.youtube.com/watch?v=TpPR5JhTFdc[/video]

 

[Ccolvin968]

Thanks for the input everyone. I'm just trying to get them lined up correctly.
Should I use screws or can I mount with only Epoxy or JB Weld?
Would it hurt to use a dab of either added with loctite to make sure they don't move?
My centering rings are too thin to screw anything in to.

 

[K'Tesh]

Thanks for the input everyone. I'm just trying to get them lined up correctly.

I'm sure I'm speaking for just about everyone here (maybe not all). Not a problem, glad to help.

With what you've been given already, you should be able to get it done to your satisfaction.

Should I use screws or can I mount with only Epoxy or JB Weld?

Screws or bolts, do not glue the rail buttons to the rocket. They can wear out, and by not allowing them to spin freely, they're likely to wear out even faster.

Would it hurt to use a dab of either added with loctite to make sure they don't move?

Locktite to hold the screw in, probably wouldn't hurt, but if you check them before launching (does it look like it's backing out? Yes, tighten it. No, fine as is) you're likely not to run into any problems. Rail buttons are cheap, if one were to back out and fall off (in flight) it's likely no great loss.

My centering rings are too thin to screw anything in to.

Thus my suggestion about adding a piece of scrap wood to screw into.

Best of Luck! Straight Smoke! Good Chutes!