Time for another update. I’ve filled the spirals in the false motor tubes and sprayed primer on them to check for missed spots. The photo below shows the end with the fin alignment guide on and the first two fins tacked in place.
Here is a view with all the fins tacked in place and the alignment tool removed.
Next I began pouring 30 minute epoxy down the fin roots to get them firmly attached. This took a while since I could really only effectively do two fins at a time. Then I needed to let them set up so I could rotate the airframe and do another two. Also, since I needed to get epoxy down both sides of the fin roots, it still took seven rotations to get them all done. Here is a look down from the end. The lighting is bad so you might not see much epoxy but it is there.
After all the roots had cured I more or less repeated the process to be sure that I got a good joint all the way down. I then needed to pour fillets for the fins where they meet the dummy motor tubes. I used some clay to plug the end and keep the epoxy from running out and all over the motor tube.
I then poured epoxy into the area and made sure the tube was barely in a nose up attitude. This allowed the epoxy to flow and level without all of it leaking down the front of the fin. I did make sure that some epoxy did flow down the front edge of the fin into the void below. That made for a nice smooth fillet line from the leading edge to the trailing edge.
I then mixed some epoxy with microballoons to make a paste that I could use to fill the voids between the dummy motor tubes and the main motor tube. The picture looks ugly, but when looking at it by eye it is relatively smooth. I’ll see what it looks like when I spray primer over the whole bird later.
Next I need to start working on the nose cone and then can come the painting. Maybe I’ll be ready for a test flight in August?
More work has been done on the Wild Thing. I drilled four small holes through the motor tube and into the 5/8 inch plug. I then epoxied 4 short sections of dowel into the holes. These will serve two purposes. First, they will provide a bit of an additional anchor for the plug to prevent it coming loose during recovery. Admittedly a small chance but why risk it. They will also prevent me from pushing the forward end of the baffle too far down the motor tube.
I then used the bulkhead I’m not using to mark the fin positions. This will help me get the fin alignment correct.
I then pushed it on to the back of the rocket over the 38mm motor tube.
Next, it was time to epoxy the motor mount assembly into the main tube. I first marked on the outside the position of each of the centering rings. This would help me figure out where to smear epoxy on the inside so I would be sure to push the ring through the epoxy on its way to its final position. Since there were three rings on this motor mount, I needed to smear epoxy for the top ring first. Once I had it smeared all around the inside of the tube I started pushing the motor mount in. Before the next centering ring went inside the tube, I smeared its epoxy inside the tube. Then continued pushing the mount in until I was nearing the last ring. This ring basically fits flush with the end of the main tube, so I smeared epoxy at the end of the tube. I then pushed the mount in the final amount. Once that was done I stood the rocket up on its business end as vertical as I could get it. I was using 30 minute epoxy for this, so I let it cure for a couple of hours before I laid the rocket over.
Now I needed to glue in the upper baffle bulkhead. I mixed up about 10ml of 30 minute epoxy and put my rubber gloves on. I smeared a bit of epoxy just above where the bulkhead was to go and then pressed the bulkhead into place. I then used a finger and scooped out some epoxy from the cup and smeared it around the tube/bulkhead joint. I also smeared some around the motor tube/bulkhead joint. I again stood the rocket up vertical until the epoxy had cured.
I then installed the rail buttons. The lower button was screwed into the centering ring at the base of the main tube. The upper button was installed just above the upper baffle ring.
I need to fill in the spirals on the dummy tubes. I could have glassed them but that would have made it difficult to get them installed on the centering rings, and made it harder to get the fins on. It won’t be too bad to get them filled. Then it will be on to the fins. I’ll start by rounding the edges. Then they will get glued in according to the alignment ring I made. Anyway that will be a future update. That’s it for now, thanks for looking.
Here is a brief update on the Wild Thing. I’ve got the baffle almost finished. I drilled 4 holes on four sides of the top of the motor tube. I have the bottom bulkhead of the baffle tacked in place.
Here are all the parts of the baffle section.
I did away with the forward bulkhead that came with the kit and replaced it with two thinner bulkheads from Apogee Components. I drilled four 1 inch holes in one of the bulkheads. That will be the top of the baffle. It will be installed after the motor mount is expoxied in the main tube. That will let me get a good bond on the bottom bulkhead of the baffle. The part with the eyebolt in the lower left of the picture is the recovery system anchor point. It is a 5/8 in plywood plug with a hole in the middle to allow the eyebolt to be attached. I will epoxy the nut of the eyebolt to prevent any future loosening. It gets installed at the top of the motor tube. It will force the exhaust gasses out the holes in the motor tube and then they will pass through the four holes in the forward baffle bulkhead. I use this system in my Mini Magg to good effect.
Here are the baffle parts dry fitted for a check.
I have also started printing some additional parts for the rocket. You might recognize what these are supposed to represent. They are strictly decorative on this rocket. But I think they will add to the visual appeal once the paint goes on.
Time for a quick update on the Wild Thing. I finished sanding the seam on the tube and it is now quite smooth as can be seen in the below photo.
I did have a spot on one end of the tube where one layer of the fiberglass lamination did not stick and got sanded off. The first layer was still well attached to the tube so I just needed to patch the one layer. I mixed some 30 minute epoxy and spread it into the divot. Then I took a strip of blue painters tape to get the epoxy to lay smooth and avoid a bunch of sanding. After it set I removed the tape. I gave it a day to completely cure and then sanded it smooth. The below picture shows the edge where the patch is. You can hardly tell it is there.
With the tube done for now, I turned my attention back to the motor mount. I dry assembled the parts and then put the fins in place. I wanted to see if my tape spacer at the end of the 29mm tubes was going to affect how the fins fit in place. Here is a picture of the dry assembly.
It looks like they will fit fine. Without the tape spacer the 29mm tubes would be too close together to get the fins all the way to the 38mm tube. This is the way the kit was designed. The result would make the fins just a bit more fragile on landings. With the spacer in place I am able to get the fins all the way to the 38mm tube. This will result in a much stronger joint. I ran the change through Rocksim and it doesn’t affect the stability. With seven fins it will be very stable even with the fins being about 3/8 to 1/2 inch shorter than the original design.
Next I wanted to start assembling the motor mount. Since the 29mm tubes actually hold the 38mm tube in place it was going to be very messy trying to glue the tubes together tube by tube and keep them parallel to the center line while keeping the centering rings perpendicular to the center line. Here is a shot of the plans showing the way the tubes fit together.
What I decided to do was to fit all the tubes together, then get the centering rings lined up and make sure the tubes are not angled. Then I applied some CA glue to the centering rings and 29mm tubes to hold them in place. Then I mixed up some 30 minute epoxy and glued the 29mm tubes to the upper centering ring.
After that had cured I used more 30 minute epoxy to glue the 38mm tube to the 29mm tubes from the top of the upper centering ring.
When this is completed I’ll epoxy the 29mm tubes to the back centering ring. The 38mm tube will be firmly attached to the airframe not only at this point, but also at it’s upper end by the baffle that I will build later. At the business end, the fins will solidly attach the 38mm tube to both the fins and the 29mm tubes.
When I finish the fins, I’ll work on the baffle at the front of the 38mm motor tube.
I got the new pumps from West Marine, so now it’s time to glass the tube. I placed the tube on a section of PVC pipe and suspended that between a couple of saw horses.
Next I mixed up some epoxy and coated the tube with the epoxy resin before I started applying the fiberglass.
Next I took my fiberglass and laid one edge on the line I had previously drawn. Then I slowly pressed the glass into the wet tube and started rolling the tube and applying the fiberglass. After I had about 4 inches or so started on the tube I then brushed some more epoxy resin on the glass to get it thoroughly wet. When the fiberglass is clear and you can see the tube underneath then it is wet enough. But you don’t want the resin dripping off either, just enough to get it wet. I then rolled the tube and applied more glass. I smoothed it down and toward the tube ends with my hands as I applied the glass. I also was checking for air pockets in the glass as I was going and smoothed them out as I went. This continued until I made it back around to where I started and then continued with more resin and more rolling the tube. I cut the fiberglass so I had enough to wrap the tube twice. Two layers should be enough for this build. I’m sorry I don’t have pictures of the actual process, I was doing this by myself and my gloved hands were sticky with resin so I didn’t want to touch my phone. Anyway here is the tube after it had two layers of glass applied.
I wrapped the ends with some masking tape to try and keep the ends attached to the tube. Keeping the ends smooth without any wrinkles is one of the hard parts of glassing a tube. When the fiberglass is at the just barely tacky stage but not fully cured then you can remove the tape. When the fiberglass is still at the plastic stage but not hard cured you can cut the ends of the fiberglass cloth flush with the tube ends. Here is the tube with the ends cut off.
You can see I brought it into the house. I did that to help with the cure. When the tube was cured to the point that the resin was not wanting to run anymore I brought it in. The weather just didn’t warm the garage up enough. The warmth of the house finished the cure nicely. Next comes the fun part of sanding the seam smooth and doing any necessary touch ups on the ends. Anyway that’s where is stands as of now. More to come and thanks for looking.