Thunderbird 3 is GO!
I haven’t built a LPR kit for a while and this one has been sitting around for about six months. I started this quite a while back, if you consider opening the packet, checking all the bits are there and downloading the instructions. Construction was only started very recently. Since it isn't just a 3FNC rocket I thought it worthy of a build thread.
The kit comes from Radical Rocketry, but don’t forget you also need to purchase some BT-50, BT-60 and BT-80 tubes as well. Parts are printed in ABS plastic (not the usual PLA used in most hobby printers) so they should withstand normal car temperatures without losing form.
https://radicalrocketry.com/
For anyone in Australia, Cape Byron Rocketry has the kits stocked.
Fin pieces were separated out and the furry edges from the CNC machining gently taken off very quickly with an emery board (used for sanding fingernails). The fin ply material looks to be really good and will not need much filling and sanding.
The main transition was sprayed with spray putty and sanded a little. I tried doing this in the lathe, but in the end it was overkill and didn’t achieve any improvement from what I could see. The round parts were sanded on the lathe, and the fins will be left unsanded and with a little texture. Heatsinks work better that way anyway
.
I attacked the nosecone next. It had quite a seam up one side, so I followed the instructions and made a slurry of ABS using the scrap pieces from the 3D printing and acetone. If you are doing this, remember to do it in a well-ventilated space. Don’t forget safety glasses and gloves too. The seam was filled with the slurry and allowed to dry out. It was then sanded with 240-grit until it was down to about the right level. This also took the layer lines off the 3D print, leaving a relatively smooth NC. Next up was a quick wipe with wax and grease remover before coating with a spray putty. This was sanded back to a reasonable finish, and then another layer of spray putty applied, and given a final light sanding. It came up quite good really. The pic looks a bit furry but it is just the camera and resized image. Very smooth.
All the ABS parts were filed and sanded to take any slight lips of the ends of the parts. There are quite a few parts but it really didn’t take too long at all. The airfoils I didn’t bother sanding at all, just made sure they were relatively clean for later use. The front and rear parts for the pods were smoothed in the lathe, with an 18mm expended motor in the chuck and the parts pushed onto that. That method seemed to work well and produce nice smooth pod nose and tail cones. No sign of layer lines after it was done.
Tubes were cut to length, sanded square and marked as per instructions using the marks on the 3D printed transition, aluminium angle and pencil. Nine slots were cut in the various tubes.
I discovered that if you make the slots undersize you can trim them open and straight, with surgical precision, if you hold a steel rule along the location you want to cut and use that to guide a scalpel while you make a slicing motion. You can take out really fine slivers of cardboard that way, easing the hole to the correct size, and with a straight edge!
Tabs on the fins were trimmed down slightly in length, to go into the 20mm and 40mm long slots in the airframe.
FYI, I printed up some tube sanding jigs to square the tube ends after cutting with a scalpel. Not sure where I saw the idea, but it works really well. The 3D parts were printed, holes tapped, 240-grit glued to the disks and then assembled.
Stay tuned!
I haven’t built a LPR kit for a while and this one has been sitting around for about six months. I started this quite a while back, if you consider opening the packet, checking all the bits are there and downloading the instructions. Construction was only started very recently. Since it isn't just a 3FNC rocket I thought it worthy of a build thread.
The kit comes from Radical Rocketry, but don’t forget you also need to purchase some BT-50, BT-60 and BT-80 tubes as well. Parts are printed in ABS plastic (not the usual PLA used in most hobby printers) so they should withstand normal car temperatures without losing form.
https://radicalrocketry.com/
For anyone in Australia, Cape Byron Rocketry has the kits stocked.
Fin pieces were separated out and the furry edges from the CNC machining gently taken off very quickly with an emery board (used for sanding fingernails). The fin ply material looks to be really good and will not need much filling and sanding.
The main transition was sprayed with spray putty and sanded a little. I tried doing this in the lathe, but in the end it was overkill and didn’t achieve any improvement from what I could see. The round parts were sanded on the lathe, and the fins will be left unsanded and with a little texture. Heatsinks work better that way anyway
.I attacked the nosecone next. It had quite a seam up one side, so I followed the instructions and made a slurry of ABS using the scrap pieces from the 3D printing and acetone. If you are doing this, remember to do it in a well-ventilated space. Don’t forget safety glasses and gloves too. The seam was filled with the slurry and allowed to dry out. It was then sanded with 240-grit until it was down to about the right level. This also took the layer lines off the 3D print, leaving a relatively smooth NC. Next up was a quick wipe with wax and grease remover before coating with a spray putty. This was sanded back to a reasonable finish, and then another layer of spray putty applied, and given a final light sanding. It came up quite good really. The pic looks a bit furry but it is just the camera and resized image. Very smooth.
All the ABS parts were filed and sanded to take any slight lips of the ends of the parts. There are quite a few parts but it really didn’t take too long at all. The airfoils I didn’t bother sanding at all, just made sure they were relatively clean for later use. The front and rear parts for the pods were smoothed in the lathe, with an 18mm expended motor in the chuck and the parts pushed onto that. That method seemed to work well and produce nice smooth pod nose and tail cones. No sign of layer lines after it was done.
Tubes were cut to length, sanded square and marked as per instructions using the marks on the 3D printed transition, aluminium angle and pencil. Nine slots were cut in the various tubes.
I discovered that if you make the slots undersize you can trim them open and straight, with surgical precision, if you hold a steel rule along the location you want to cut and use that to guide a scalpel while you make a slicing motion. You can take out really fine slivers of cardboard that way, easing the hole to the correct size, and with a straight edge!
Tabs on the fins were trimmed down slightly in length, to go into the 20mm and 40mm long slots in the airframe.
FYI, I printed up some tube sanding jigs to square the tube ends after cutting with a scalpel. Not sure where I saw the idea, but it works really well. The 3D parts were printed, holes tapped, 240-grit glued to the disks and then assembled.
Stay tuned!
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