My daughter picked out this rocket because she liked the looks of it and also it flies on 29mm motors which are relatively inexpensive and don't require hazmat to ship. We started on it this past weekend and have benefitted from other's threads, so thought I would post our progress here.
Having built a few rockets with fins assemblies outside of the booster tube, I really wanted to do that for this rocket. Problem is that isn't possible with the supplied rings. After thinking about it for a bit, I realized I could create something with my CNC that would serve that purpose. I devised a thicker ring that has slots cut into it to hold the fins at perfect 90 degree angles to the motor mount and allow for an outside the tube construction approach. Here are the rings freshly cut from the sheet stock:
While the stock kit only comes with two rings and a short tube, I opted to make a longer motor mount and include a third forward ring. The thicker rings will also come in handy to screw in the rail buttons later. The stock is baltic birch and is nominally 3/8" thick.
Before we could assemble the mount, I did a quick bevel on the leading and trailing edges using an 11 degree carbide chamfer bit and the router table:
The result was nicely chamfered fins that will make a nice airfoil:
Next was the glue up of the entire assembly. We used Rocket Poxy and you can see the finished result here. It made for a quick and easy assembly. To insure one ring was planar with the other, I scribed a line on the motor mount tube and made sure that the first fin root was exactly parallel to the scribed line. I also allowed enough of the motor mount to stick out to attach a motor retainer which will be glued on after finishing. Since there is a space between the fins and the rings that will be occupied by the booster tube, I had to be careful to clean out any epoxy that collected there. Also opted for a 8/32" screw eye frozen in place with epoxy:
The bane of my existence for any of these projects is filling the spirals. I decided to try one of LOC's kits for fiberglassing the tubes and I have to say it worked great, even for the first time. I used CE 2000 epoxy that was made by by an outfit called resin research. It has an open time of about 30 minutes before it starts to harden. I made it in two batches, doing first the booster section and then the payload section. Big take aways are make more epoxy than you think you will need. I feel like it went on too thin on the booster which left some rough spots that I will fill in. I used a liberal amount on the payload and it came out as smooth as glass. The only thing that needs addressed on the payload section is the .002" high ridge where the edge of the one piece of mylar started. Make sure you have everything laid out. I weighed the 2:1 mixture by pouring it into a paper cup on a postage scale. I also used a cheap $1 Harbor freight chip brush which I was surprised shed very few bristles. Like maybe only two that I had to pick off the fiberglass. Start with lots of space and a taped down piece of freezer paper (coated side up) and all the stuff you will need:
I intended to document this more fully, but wearing gloves and working with sticky epoxy proved a challenge. So I didn't catch any more shots than this and the finished product. Some thoughts:
1) Pour the epoxy right on the fiberglass in as many streams as you can. the more the better as it's not like paint and the more uniform you can make it the better
2) Use the brush to work it all around on the fiberglass until it all becomes a uniform color.
3) It seems like the perfect amount of epoxy on the fiberglass is when you can't see the weave of the fiberglass anymore. if you can, it might leave a rough finish on the tube.
4) Don't expect the fiberglass to have a perfect seam--it will overlap and you will never be able to see where that is in the finished product. Just make sure that the seam of the fiberglass is not lined up with the seam in the mylar.
5) Roll the entire works on the tube and once you are like 3/4 of the way wrapped, carefully peel back the butcher paper and finish rolling the tube
6) With your hands, smooth out the fiberglass ensuring there are no puckers or gathers...this is mostly an issue on the end where the seam is, so take note
7) Once wrapped, pick the whole thing up and put it on the mylar and roll it up and tape in the middle. I used an old credit card to get the air bubbles out. One thing that i didn't fully realize until after it was dry is there are two kinds of bubbles. One type is large bubbles between the epoxy and surface of the mylar. These are easily worked out with the credit card. The other type are tiny bubbles in the epoxy itself that are not on the surface of the mylar. You will never get all of those out, but once the epoxy is dry, it won't matter as they are not on the surface and are very tiny. Perhaps these tiny bubbles are unique to my flavor of epoxy.
8) Leave the brush in the epoxy as a guide for when to cut the wrapped ends flush with a knife. it should be a little flexible and not hard. It is much easier to cut when it is not fully cured than it is after it hardens. I trimmed the ends flush and cut out the fin slots. I think I did that cutting about 4 hours after mixing. YMMV with your formulation of epoxy.
A shot of the finished product which is as smooth as a pvc pipe (at least the payload section):
Not a hint of a spiral and it will really be a snap to paint. I think it was much less work than filling spirals and you have the added bonus of extra strength. Pretty excited about learning this new skill.
More to follow. Next step is to slit the booster and epoxy in the fin assembly.
Having built a few rockets with fins assemblies outside of the booster tube, I really wanted to do that for this rocket. Problem is that isn't possible with the supplied rings. After thinking about it for a bit, I realized I could create something with my CNC that would serve that purpose. I devised a thicker ring that has slots cut into it to hold the fins at perfect 90 degree angles to the motor mount and allow for an outside the tube construction approach. Here are the rings freshly cut from the sheet stock:
While the stock kit only comes with two rings and a short tube, I opted to make a longer motor mount and include a third forward ring. The thicker rings will also come in handy to screw in the rail buttons later. The stock is baltic birch and is nominally 3/8" thick.
Before we could assemble the mount, I did a quick bevel on the leading and trailing edges using an 11 degree carbide chamfer bit and the router table:
The result was nicely chamfered fins that will make a nice airfoil:
Next was the glue up of the entire assembly. We used Rocket Poxy and you can see the finished result here. It made for a quick and easy assembly. To insure one ring was planar with the other, I scribed a line on the motor mount tube and made sure that the first fin root was exactly parallel to the scribed line. I also allowed enough of the motor mount to stick out to attach a motor retainer which will be glued on after finishing. Since there is a space between the fins and the rings that will be occupied by the booster tube, I had to be careful to clean out any epoxy that collected there. Also opted for a 8/32" screw eye frozen in place with epoxy:
The bane of my existence for any of these projects is filling the spirals. I decided to try one of LOC's kits for fiberglassing the tubes and I have to say it worked great, even for the first time. I used CE 2000 epoxy that was made by by an outfit called resin research. It has an open time of about 30 minutes before it starts to harden. I made it in two batches, doing first the booster section and then the payload section. Big take aways are make more epoxy than you think you will need. I feel like it went on too thin on the booster which left some rough spots that I will fill in. I used a liberal amount on the payload and it came out as smooth as glass. The only thing that needs addressed on the payload section is the .002" high ridge where the edge of the one piece of mylar started. Make sure you have everything laid out. I weighed the 2:1 mixture by pouring it into a paper cup on a postage scale. I also used a cheap $1 Harbor freight chip brush which I was surprised shed very few bristles. Like maybe only two that I had to pick off the fiberglass. Start with lots of space and a taped down piece of freezer paper (coated side up) and all the stuff you will need:
I intended to document this more fully, but wearing gloves and working with sticky epoxy proved a challenge. So I didn't catch any more shots than this and the finished product. Some thoughts:
1) Pour the epoxy right on the fiberglass in as many streams as you can. the more the better as it's not like paint and the more uniform you can make it the better
2) Use the brush to work it all around on the fiberglass until it all becomes a uniform color.
3) It seems like the perfect amount of epoxy on the fiberglass is when you can't see the weave of the fiberglass anymore. if you can, it might leave a rough finish on the tube.
4) Don't expect the fiberglass to have a perfect seam--it will overlap and you will never be able to see where that is in the finished product. Just make sure that the seam of the fiberglass is not lined up with the seam in the mylar.
5) Roll the entire works on the tube and once you are like 3/4 of the way wrapped, carefully peel back the butcher paper and finish rolling the tube
6) With your hands, smooth out the fiberglass ensuring there are no puckers or gathers...this is mostly an issue on the end where the seam is, so take note
7) Once wrapped, pick the whole thing up and put it on the mylar and roll it up and tape in the middle. I used an old credit card to get the air bubbles out. One thing that i didn't fully realize until after it was dry is there are two kinds of bubbles. One type is large bubbles between the epoxy and surface of the mylar. These are easily worked out with the credit card. The other type are tiny bubbles in the epoxy itself that are not on the surface of the mylar. You will never get all of those out, but once the epoxy is dry, it won't matter as they are not on the surface and are very tiny. Perhaps these tiny bubbles are unique to my flavor of epoxy.
8) Leave the brush in the epoxy as a guide for when to cut the wrapped ends flush with a knife. it should be a little flexible and not hard. It is much easier to cut when it is not fully cured than it is after it hardens. I trimmed the ends flush and cut out the fin slots. I think I did that cutting about 4 hours after mixing. YMMV with your formulation of epoxy.
A shot of the finished product which is as smooth as a pvc pipe (at least the payload section):
Not a hint of a spiral and it will really be a snap to paint. I think it was much less work than filling spirals and you have the added bonus of extra strength. Pretty excited about learning this new skill.
More to follow. Next step is to slit the booster and epoxy in the fin assembly.
