Madcow Super DX3 Mods

[doug_kosty]

So... Santa brought me my first HP kit, and I am puzzling over a few details as to how to build it.

Santa was extra nice and got me the optional altimeter bay, and this is the source of my first stumpage. I'd like to build this to allow motor deploy, altimeter apogee only deploy, and dual deploy (why not......). I figure I'll start with motor deploy and work my way up in complexity.

The instructions on the bay are pretty good, but I am puzzled why they suggest epoxying the bay into the upper airframe. If you do that, the top of the bay is recessed about 14 inches below the nosecone, and is pretty difficult to get at.

My notion is to fasten the bay to the upper airframe using a few (6?) 8-32 tee nuts and screws. It would be a simple matter to remove the screws and pull the bay out completely.

For those unfamiliar with this kit, it is heavy paper tubing, not fiberglass. BTW - "super dx3" is 4 inches in diameter...

Any problems with my plan?

 

[mikec]

My notion is to fasten the bay to the upper airframe using a few (6?) 8-32 tee nuts and screws. It would be a simple matter to remove the screws and pull the bay out completely.

This will definitely work; 6 is way overkill. My Super DX3 uses two #6 screws into T-nuts on small squares of plywood inside the bay.

You can epoxy the bay into the upper tube, though. You just slide the forward bulkhead through the payload tube. I've done this on some rockets and it can be just as simple, it just doesn't allow you to put the bay together at home, which may be easier.

Word of advice -- my Super DX3 didn't like to fly drogueless dual-deploy; it was stable nose-down. You might consider a 12-to-18-inch drogue or maybe a big streamer.

 

[markt51]

I too have the DX3 and was wondering the same thing. I'm waiting on my av bay to arrive still so I have time to work it all out. Appreciate the additional advise on the drogue. . .

 

[doug_kosty]

This will definitely work; 6 is way overkill. My Super DX3 uses two #6 screws into T-nuts on small squares of plywood inside the bay.

You can epoxy the bay into the upper tube, though. You just slide the forward bulkhead through the payload tube. I've done this on some rockets and it can be just as simple, it just doesn't allow you to put the bay together at home, which may be easier.

Word of advice -- my Super DX3 didn't like to fly drogueless dual-deploy; it was stable nose-down. You might consider a 12-to-18-inch drogue or maybe a big streamer.

Thanks for the thoughts. I don't really have a feel for how sturdy to make things - perhaps I'll go with three screws - that'll satisfy my need for symmetry with respect to the fins

Funny - I didn't even consider feeding the top of the ebay through the upper airframe. Guess I need to stare at things a little more!

 

[mikec]

my Super DX3 didn't like to fly drogueless dual-deploy; it was stable nose-down.

In fairness this was on a CTI 4G motor with a good bit of nose weight and the original stubby 3:1 ogive cone. The newer version with the larger NC might do OK drogueless.

 

[sylvie369]

I would not epoxy the coupler in, for exactly the reasons you give (chiefly ease of access).

I'm building one of these as well, and it will have a standard altimeter bay, removable at both ends, for dual deployment, as have all of my other DD rockets.

I agree that 6 screws is overkill. I've always used two, going into blind t-nuts inside the altimeter bay.

 

[doug_kosty]

O.K. - having decided to cut down on the number of screws holding in the altimeter bay :wink:, now onto the next conundrum. The kit ships with open eyebolts to attach the recovery system. Use or replace? This is not a massive rocket, so I am inclined to use as is, but I am more than willing to be educated!

 

[sylvie369]

O.K. - having decided to cut down on the number of screws holding in the altimeter bay :wink:, now onto the next conundrum. The kit ships with open eyebolts to attach the recovery system. Use or replace? This is not a massive rocket, so I am inclined to use as is, but I am more than willing to be educated!

Replace. Might as well get in the habit right away. All you have to do is drill one more hole, and make sure that the u-bolt you install is clear of your threaded rods and ejection cannisters. They add a little weight, but having two attach points and nothing open to pull straight is worth the tradeoff.

That being said, I built my first electronics bay with open eyebolts (before I knew better), and never had a problem. More than 35 DD flights, and I eventually lost the rocket. I'm sure it had quite a few more flights in it. If you do everything right, there shouldn't ever be that much strain on the recovery harness anyway.