Here is a picture of my altimeter bay. It is a coupler tube. Each bulkhead consisits of:
1- 1/8" ply bulkhead inside coupler
2 - 1/4" ply bulkhead outside with O-ring groove
1 - 3/8" ply to connect the U-bolts to
Left to right:
The left bulkhead is removable, and has an extra o-ring to seal. Next are the ports, CA reinforced. The right bulkhead is epoxied on, so no worries about gas leakage. Then are some 6-32 brass wood inserts with 6-32 button head hex screws to keep the bay in the rocket. There are 3 and they are equally spaced.
The bulkhead is connected with a piece of 1/4-20 steel threaded rod run in the center of the bulkheads.
This picture shows the electronics mounted on a sled. The 1/4-20 rod runs underneath the board. The battery is on the backside of the board. All wires come into the bay on the backside (where the battery is). The 1/4-20 rod runs through the spacers and that holds the sled in place.
This is a closeup of my anti-pulling solution. I didn't want the ejection charges to be pulling on the connecting terminals when in flight in case they shift, or when installing. I drilled three holes and ran the wire through. Took care of the problem.
Here is an end view of the bay. This is the drogue side. It is epoxied permanently onto the coupler. You can see the U-bolt and the three 6-32 retention screws. The hole on the right is where the e-match wires go through. Also, the 1/4-20 all thread is sealed with a small rubber washer under the nut against ejection gasses.
This shows the retention bolts and static port on the airframe. The airframe was marked (1/3 way for each port), then the coupler was inserted. Once it was in the appropriate position all the holes were drilled at once through both materials to insure they would line up.
Here is a picture showing how everything went together in the airframe. I used 3/8" tubular nylon to connect everything. The spacing was tight, especially with dog barf and a chute protector. The bay was just slide into the airframe and twisted into position. To arm I used the twist wire method.
I hope that helps, I'm sure other people can chime in with their setups also. This one worked really great for me. The reason I slide the bay up instead of cutting the airframe was that it was really loose. It allowed a lot of slop. If I could find a tighter coupler, then I would have cut the airframe, making installation easier. If I did that though, I would have needed to add a second set of bolts on the top of the bay to retain that section.
That is a really good method, I like the presicion that it was done with but, you run into a couple problems when you build the alt bay like this. It only works for one rocket, and if you want to move your altimeter it is a hassle.
I use the smokin rocket method (members.aol.com/SMOKINRKTS/ALTITUBE.html) essentially you have coupler with a payload section above it and you put a 54mm tube inside. You then make a sled that fits in this tube and stick your altimeter on it. Then you wire a match into both bays (payload for main and booster for drogue) and fire your rocket (the sled is retained with a screw and washer) then when you want to fly another rocket, simply slide the sled out of the first one and into the 54m,m tube in the bay of the second one
I know that I can't move the alt bay, but I wasn't wanting to. It was purpose built for this rocket. I just move my sled between bays because all of my bays use the center mounted sled. If I could have found a tighter coupler I would have cut the rocket in half and had two sets of holding screws. Would have made assembly easier. Our store just had one tight coupler and I used that for the fincan/payload connection and one slightly loose coupler (it would slide from top to bottom w/o help). For each rocket I have a different bay/coupler because of my different needs. Plus, I really like trying new things with them and each time I build one there is a new revision. The next version is a 75mm bay that I have a on/off switch mounted through the altimeter port. The switch can be seen on Missileworks site. I'm also hoping to have a G10 fiberglass charge holder that screws into the bulkhead on this one, will look kind of like what is on a PML CPR unit.
For me I really like building a new one each time, but interchangable is cool also. Two ways to fillet a fin.