Astrobee D ...rail buttons...

[Stones]

Just picked up an Astrobee D (Aerotech) and I'm thinking of going with rail buttons instead of the stock 1/4 lugs. Anyone done this mod? I figure one could leave the material in the slots on the tube and either fil 'n finish or epoxy over them. I'm also figuring to go with 3 buttons, one at the aft CR, one somewhere close to the stock top LL, and another between the CP/CG. Comments?...

 

[Juerg]

I'd just use two buttons in about the same location as the lugs would go.
If you do so, I'd suggest to install some sort of key to define the orientation of booster and payload towards each other so the guides are allways in line.

The other option is to install one rail guide at the very end of the rocket and the other rail guide in the area of the forward bulkhead. Should work as well

Juerg

 

[Stones]

Juerg...
Tnx for the info. I've attached a pic that shows where I think a 2 button setup would work.

 

[rstaff3]

Stones, the general placement looks good. I'd move the bottom button up a tad so it enters just below that bottom ring (if I'm reading the drawing correctly) and shift the upper button to just below the top ring. This placement has worked well for me.

 

[Juerg]

Yes, should work fine!

Cheers

Juerg

 

[Stones]

Obviously, the paint scheme lends itself to attaching the fins to the BT, after everything is painted. My question, is the top narrow section of the root edge of the fins glued to the BT? Seems it might be a mess in the making, trying to lay down such a small area of glue to match up to this narrow edge when attaching the fins to the fin locks/BT. On the other hand, this area seems a bit "flexable" and I'm wondering if the flow of air during and after launch may cause some distortion and cause an unstable flight. Those of you who have built this one, what worked, didn't work, etc. ?

tia...

 

[Juerg]

I did mount the fins after painting the body tube.
I used slow curing CA (ZAP odorless) to glue the finlock tabs in place.
I put also CA in the fin root and made sure the fins are straight. (You'll probably have to bend them carefully, the fins are normally wraped a bit)
Only after having istalled all four fins, I did fill up the gap on the fin root carefully using ZAP a Gap where needed.
You should make sure both ends of the fin root are well bonded to the tube. Not so much because of airflow considerations but because otherwise the plastic tends to go back into its original wraped shape.

Have fun

Juerg